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Sample records for alga chlamydomonas sp

  1. Interactions between marine facultative epiphyte Chlamydomonas sp. (Chlamydomonadales, Chlorophyta) and ceramiaceaen algae (Rhodophyta).

    PubMed

    Klochkova, Tatyana A; Cho, Ga Youn; Boo, Sung Min; Chung, Ki Wha; Kim, Song Ja; Kim, Gwang Hoon

    2008-07-01

    Previously unrecorded marine Chlamydomonas that grew epiphytic on ceramiaceaen algae was collected from the western coast of Korea and isolated into a unialgal culture. The isolate was subjected to 18S rDNA phylogenetic analysis as well as ultrastructure and life cycle studies. It had an affinity with the marine Chlamydomonas species and was less related to freshwater/terrestrial representatives of this genus. It had flagella shorter than the cell body two-layered cell wall with striated outer surface and abundant mucilaginous material beneath the innermost layer and no contractile vacuoles. This alga grew faster in mixed cultures with ceramiaceaen algae rather than in any tested unialgal culture condition; the cells looked healthier and zoosporangia and motile flagellated vegetative cells appeared more often. These results suggested that this Chlamydomonas might be a facultative epiphyte benefiting from its hosts. Several ceramiaceaen algae were tested as host plants. Meanwhile, cell deformation or collapse of the whole thallus was caused to Aglaothamnion byssoides, and preliminary study suggested that a substance released from Chlamydomonas caused the response. This is first report on harmful epiphytic interactions between Chlamydomonas species and red ceramiaceaen algae. PMID:19195375

  2. Transcriptome-wide analysis of DEAD-box RNA helicase gene family in an Antarctic psychrophilic alga Chlamydomonas sp. ICE-L.

    PubMed

    Liu, Chenlin; Huang, Xiaohang

    2015-09-01

    DEAD-box RNA helicase family proteins have been identified in almost all living organisms. Some of them play a crucial role in adaptation to environmental changes and stress response, especially in the low-temperature acclimation in different kinds of organisms. Compared with the full swing study in plants and bacteria, the characters and functions of DEAD-box family proteins had not been surveyed in algae. To identify genes critical for freezing acclimation in algae, we screened DEAD-box RNA helicase genes from the transcriptome sequences of a psychrophilic microalga Chlamydomonas sp. ICE-L which was isolated from Antarctic sea ice. Totally 39 DEAD-box RNA helicase genes had been identified. Most of the DEAD-box RNA helicase have 1:1 homologous relationships in Chlamydomonas reinhardtii and Chlamydomonas sp. ICE-L with several exceptions. The homologous proteins in ICE-L to the helicases critical for cold or freezing tolerance in Arabidopsis thaliana had been identified based on phylogenetic comparison studies. The response of these helicase genes is not always identical in the Chlamydomonas sp. ICE-L and Arabidopsis under the same low-temperature treatment. The expression of several DEAD-box RNA helicase genes including CiRH5, CiRH25, CiRH28, and CiRH55 were significantly up-regulated under freezing treatment of ICE-L and their function in freezing acclimation of ICE-L deserved further investigation. PMID:26174530

  3. Chlamydomonas sajao nov. sp. (Chlorophyta, Volvocales)

    NASA Astrophysics Data System (ADS)

    Lewin, Ralph A.

    1984-06-01

    A new species of Chlamydomonas, namely, C. sajao nov. sp. of the Volvocales, Chlorophyta was isolated from a duckweed growing near a ricefield in the vicinity of Guangzhou, China. This interesting unicellular green alga, similar to C. mexicana from Mexico, secretes quantities of extracellular mucilaginous polysaccharides, and may be employed in improving soil quality. The new species resembles C. waldenburgensis Moewus in most characteristics but differs in three important features.

  4. Long-term experiment on physiological responses to synergetic effects of ocean acidification and photoperiod in the Antarctic sea ice algae Chlamydomonas sp. ICE-L.

    PubMed

    Xu, Dong; Wang, Yitao; Fan, Xiao; Wang, Dongsheng; Ye, Naihao; Zhang, Xiaowen; Mou, Shanli; Guan, Zheng; Zhuang, Zhimeng

    2014-07-15

    Studies on ocean acidification have mostly been based on short-term experiments of low latitude with few investigations of the long-term influence on sea ice communities. Here, the combined effects of ocean acidification and photoperiod on the physiological response of the Antarctic sea ice microalgae Chlamydomonas sp. ICE-L were examined. There was a general increase in growth, PSII photosynthetic parameters, and N and P uptake in continuous light, compared to those exposed to regular dark and light cycles. Elevated pCO2 showed no consistent effect on growth rate (p=0.8) and N uptake (p=0.38) during exponential phrase, depending on the photoperiod but had a positive effect on PSII photosynthetic capacity and P uptake. Continuous dark reduced growth, photosynthesis, and nutrient uptake. Moreover, intracellular lipid, mainly in the form of PUFA, was consumed at 80% and 63% in low and high pCO2 in darkness. However, long-term culture under high pCO2 gave a more significant inhibition of growth and Fv/Fm to high light stress. In summary, ocean acidification may have significant effects on Chlamydomonas sp. ICE-L survival in polar winter. The current study contributes to an understanding of how a sea ice algae-based community may respond to global climate change at high latitudes. PMID:24922067

  5. Validation of housekeeping genes for gene expression studies in an ice alga Chlamydomonas during freezing acclimation.

    PubMed

    Liu, Chenlin; Wu, Guangting; Huang, Xiaohang; Liu, Shenghao; Cong, Bailin

    2012-05-01

    Antarctic ice alga Chlamydomonas sp. ICE-L can endure extreme low temperature and high salinity stress under freezing conditions. To elucidate the molecular acclimation mechanisms using gene expression analysis, the expression stabilities of ten housekeeping genes of Chlamydomonas sp. ICE-L during freezing stress were analyzed. Some discrepancies were detected in the ranking of the candidate reference genes between geNorm and NormFinder programs, but there was substantial agreement between the groups of genes with the most and the least stable expression. RPL19 was ranked as the best candidate reference genes. Pairwise variation (V) analysis indicated the combination of two reference genes was sufficient for qRT-PCR data normalization under the experimental conditions. Considering the co-regulation between RPL19 and RPL32 (the most stable gene pairs given by geNorm program), we propose that the mean data rendered by RPL19 and GAPDH (the most stable gene pairs given by NormFinder program) be used to normalize gene expression values in Chlamydomonas sp. ICE-L more accurately. The example of FAD3 gene expression calculation demonstrated the importance of selecting an appropriate category and number of reference genes to achieve an accurate and reliable normalization of gene expression during freeze acclimation in Chlamydomonas sp. ICE-L. PMID:22527038

  6. Azolla filiculoides Nitrogenase Activity Decrease Induced by Inoculation with Chlamydomonas sp.

    PubMed

    Habte, M

    1986-11-01

    Experiments were conducted to determine the influence of Chlamydomonas sp. on nitrogen fixation (C(2)H(2) --> C(2)H(4)) in Azolla filiculoides and on the nitrogen fixation and growth of free-living Anabaena azollae 2B organisms. Inoculation of azolla medium with Chlamydomonas sp. was associated with decreased nitrogenase activity in A. filiculoides and with increases in the density of a fungal population identified as Acremonium sp. Subsequent inoculation of azolla medium with this fungus was also accompanied by a significant decrease in nitrogenase activity of A. filiculoides. However, the extent of depression of nitrogenase activity was significantly higher when azolla medium was inoculated with Chlamydomonas sp. than when it was inoculated with Acremonium sp. Inoculation of nitrogen-free Stanier medium with either Acremonium sp. or Chlamydomonas sp. did not adversely affect the growth or nitrogenase activity of free-living A. azollae. Decreased nitrogenase activity in A. filiculoides is apparently related to the adverse influence of the green alga and the fungus on the macrosymbiont. The mechanisms that might be involved are discussed. PMID:16347211

  7. Azolla filiculoides Nitrogenase Activity Decrease Induced by Inoculation with Chlamydomonas sp. †

    PubMed Central

    Habte, Mitiku

    1986-01-01

    Experiments were conducted to determine the influence of Chlamydomonas sp. on nitrogen fixation (C2H2 → C2H4) in Azolla filiculoides and on the nitrogen fixation and growth of free-living Anabaena azollae 2B organisms. Inoculation of azolla medium with Chlamydomonas sp. was associated with decreased nitrogenase activity in A. filiculoides and with increases in the density of a fungal population identified as Acremonium sp. Subsequent inoculation of azolla medium with this fungus was also accompanied by a significant decrease in nitrogenase activity of A. filiculoides. However, the extent of depression of nitrogenase activity was significantly higher when azolla medium was inoculated with Chlamydomonas sp. than when it was inoculated with Acremonium sp. Inoculation of nitrogen-free Stanier medium with either Acremonium sp. or Chlamydomonas sp. did not adversely affect the growth or nitrogenase activity of free-living A. azollae. Decreased nitrogenase activity in A. filiculoides is apparently related to the adverse influence of the green alga and the fungus on the macrosymbiont. The mechanisms that might be involved are discussed. PMID:16347211

  8. Resolving the phylogenetic relationship between Chlamydomonas sp. UWO 241 and Chlamydomonas raudensis sag 49.72 (Chlorophyceae) with nuclear and plastid DNA sequences.

    PubMed

    Possmayer, Marc; Gupta, Rajesh K; Szyszka-Mroz, Beth; Maxwell, Denis P; Lachance, Marc-André; Hüner, Norman P A; Smith, David Roy

    2016-04-01

    The Antarctic psychrophilic green alga Chlamy-domonas sp. UWO 241 is an emerging model for studying microbial adaptation to polar environments. However, little is known about its evolutionary history and its phylogenetic relationship with other chlamydomonadalean algae is equivocal. Here, we attempt to clarify the phylogenetic position of UWO 241, specifically with respect to Chlamydomonas rau-densis SAG 49.72. Contrary to a previous report, we show that UWO 241 is a distinct species from SAG 49.72. Our phylogenetic analyses of nuclear and plastid DNA sequences reveal that UWO 241 represents a unique lineage within the Moewusinia clade (sensu Nakada) of the Chlamydomonadales (Chlorophyceae, Chlorophyta), closely affiliated to the marine species Chlamydomonas parkeae SAG 24.89. PMID:27037594

  9. D-lactate metabolism in the alga, Chlamydomonas Reinhardtii

    SciTech Connect

    Husic, D.W.; Tolbert, N.E.

    1986-05-01

    (/sup 14/C)D-lactate rapidly accumulates in Chlamydomonas cells under anaerobic conditions from the sugar-phosphate pools which are labeled during photosynthesis with /sup 14/CO/sub 2/. A soluble D-lactate dehydrogenase (30 ..mu..mol NADH oxidized/h/mg Chl), which functions only in the direction of pyruvate reduction, has been partially purified and characterized. The D-lactate is reoxidized in Chlamydomonas by a mitochondrial membrane-bound dehydrogenase. This enzyme is known in the plant literature as glycolate dehydrogenase, an enzyme of the oxidative photosynthetic carbon (C/sub 2/) cycle. This dehydrogenase may be linked to the mitochondrial electron transport chain, although the direct electron acceptor is unknown. Therefore, D-lactate accumulation may be, in part, due to the shut down of electron transport during anaerobiosis. In vivo chase experiments have shown that the D-lactate turns over rapidly when algal cells, which have been grown with air levels of CO/sub 2/ (0.04%), are returned to aerobic conditions in the light. Such turnover is not observed in cells which had been grown with 1 to 5% CO/sub 2/. Cells grown with high CO/sub 2/ have lower levels of glycolate dehydrogenase activity. They are currently using mutants of Chlamydomonas deficient in mitochondrial respiration to study the role of D-lactate oxidation in these algae.

  10. Photosynthetic H2 metabolism in Chlamydomonas reinhardtii (unicellular green algae).

    PubMed

    Melis, Anastasios

    2007-10-01

    Unicellular green algae have the ability to operate in two distinctly different environments (aerobic and anaerobic), and to photosynthetically generate molecular hydrogen (H2). A recently developed metabolic protocol in the green alga Chlamydomonas reinhardtii permitted separation of photosynthetic O2-evolution and carbon accumulation from anaerobic consumption of cellular metabolites and concomitant photosynthetic H2-evolution. The H2 evolution process was induced upon sulfate nutrient deprivation of the cells, which reversibly inhibits photosystem-II and O2-evolution in their chloroplast. In the absence of O2, and in order to generate ATP, green algae resorted to anaerobic photosynthetic metabolism, evolved H2 in the light and consumed endogenous substrate. This study summarizes recent advances on green algal hydrogen metabolism and discusses avenues of research for the further development of this method. Included is the mechanism of a substantial tenfold starch accumulation in the cells, observed promptly upon S-deprivation, and the regulated starch and protein catabolism during the subsequent H2-evolution. Also discussed is the function of a chloroplast envelope-localized sulfate permease, and the photosynthesis-respiration relationship in green algae as potential tools by which to stabilize and enhance H2 metabolism. In addition to potential practical applications of H2, approaches discussed in this work are beginning to address the biochemistry of anaerobic H2 photoproduction, its genes, proteins, regulation, and communication with other metabolic pathways in microalgae. Photosynthetic H2 production by green algae may hold the promise of generating a renewable fuel from nature's most plentiful resources, sunlight and water. The process potentially concerns global warming and the question of energy supply and demand. PMID:17721788

  11. Growth of Chlamydomonas reinhardtii in acetate-free medium when co-cultured with alginate-encapsulated, acetate-producing strains of Synechococcus sp. PCC 7002

    DOE PAGESBeta

    Therien, Jesse B.; Zadvornyy, Oleg A.; Posewitz, Matthew C.; Bryant, Donald A.; Peters, John W.

    2014-10-18

    The model alga Chlamydomonas reinhardtii requires acetate as a co-substrate for optimal production of lipids, and the addition of acetate to culture media has practical and economic implications for algal biofuel production. We demonstrate the growth of C. reinhardtii on acetate provided by mutant strains of the cyanobacterium Synechococcus sp. PCC7002.

  12. Isolation, growth, ultrastructure, and metal tolerance of the green alga, Chlamydomonas acidophila (Chlorophyta).

    PubMed

    Nishikawa, K; Tominaga, N

    2001-12-01

    An acidophilic volvocine flagellate, Chlamydomonas acidophila (Volvocales) that was isolated from an acid lake, Katanuma, in Miyagi prefecture, Japan was studied for growth, ultrastructural characterization, and metal tolerance. Chlamydomonas acidophila is obligately photoautotrophic, and did not grow in the cultures containing acetate or citrate even in the light. The optimum pH for growth was 3.5-4.5. To characterize metal tolerance, the toxic effects of Cd, Co, Cu, and Zn on this alga were also studied. Effective metal concentrations, which limited the growth by 50%, EC50 were measured, after 72 h of static exposure. EC50s were 14.4 microM Cd2+, 81.3 microM Co2+, 141 microM Cu2+, and 1.16 mM Zn2+ for 72 h of exposure. Thus, this alga had stronger tolerance to these metals than other species in the genus Chlamydomonas. PMID:11826960

  13. Utilizing the green alga Chlamydomonas reinhardtii for microbial electricity generation: a living solar cell.

    PubMed

    Rosenbaum, Miriam; Schröder, Uwe; Scholz, Fritz

    2005-10-01

    By employing living cells of the green alga Chlamydomonas reinhardtii, we demonstrate the possibility of direct electricity generation from microbial photosynthetic activity. The presented concept is based on an in situ oxidative depletion of hydrogen, photosynthetically produced by C. reinhardtii under sulfur-deprived conditions, by polymer-coated electrocatalytic electrodes. PMID:15696280

  14. Production of Recombinant Proteins in the Chloroplast of the Green Alga Chlamydomonas reinhardtii.

    PubMed

    Guzmán-Zapata, Daniel; Macedo-Osorio, Karla Soledad; Almaraz-Delgado, Alma Lorena; Durán-Figueroa, Noé; Badillo-Corona, Jesus Agustín

    2016-01-01

    Chloroplast transformation in the green algae Chlamydomonas reinhardtii can be used for the production of valuable recombinant proteins. Here, we describe chloroplast transformation of C. reinhardtii followed by protein detection. Genes of interest integrate stably by homologous recombination into the chloroplast genome following introduction by particle bombardment. Genes are inherited and expressed in lines recovered after selection in the presence of an antibiotic. Recombinant proteins can be detected by conventional techniques like immunoblotting and purified from liquid cultures. PMID:26614282

  15. Expression of fatty acid desaturase genes and fatty acid accumulation in Chlamydomonas sp. ICE-L under salt stress.

    PubMed

    An, Meiling; Mou, Shanli; Zhang, Xiaowen; Zheng, Zhou; Ye, Naihao; Wang, Dongsheng; Zhang, Wei; Miao, Jinlai

    2013-12-01

    The Antarctic ice microalgae Chlamydomonas sp. ICE-L which is highly resistant to salt stress holds promise in providing an alternative species for the production of microalgal oil. We studied the effects of the alga in confrontation with NaCl stress on the growth, oil yield and expression of fatty acid desaturase genes. The growth rate of Chlamydomonas sp. ICE-L decreased with the gradual increase in NaCl concentration. Interestingly, we found that the highest lipid content was achieved at 16‰ NaCl, reaching 23% (w/w). Meanwhile, the expression of Δ9ACPCiFAD increased rapidly while Δ12CiFAD, ω3CiFAD2 and Δ6CiFAD showed a delayed elevation in response to altered salt stress. C18:3 was the dominant PUFA, which account for about 75% TFA in Chlamydomonas sp. ICE-L. Under 96‰ and 128‰ NaCl stress, the content of C20:5 almost approached that of C18:3. In contrast, low salinity enhanced the dominance of C18:3 at the expense of C20:3 and C20:5. PMID:24084208

  16. Ecophysiology, secondary pigments and ultrastructure of Chlainomonas sp. (Chlorophyta) from the European Alps compared with Chlamydomonas nivalis forming red snow

    PubMed Central

    Remias, Daniel; Pichrtová, Martina; Pangratz, Marion; Lütz, Cornelius; Holzinger, Andreas

    2016-01-01

    Red snow is a well-known phenomenon caused by microalgae thriving in alpine and polar regions during the melting season. The ecology and biodiversity of these organisms, which are adapted to low temperatures, high irradiance and freeze–thaw events, are still poorly understood. We compared two different snow habitats containing two different green algal genera in the European Alps, namely algae blooming in seasonal rock-based snowfields (Chlamydomonas nivalis) and algae dominating waterlogged snow bedded over ice (Chlainomonas sp.). Despite the morphological similarity of the red spores found at the snow surface, we found differences in intracellular organization investigated by light and transmission electron microscopy and in secondary pigments investigated by chromatographic analysis in combination with mass spectrometry. Spores of Chlainomonas sp. show clear differences from Chlamydomonas nivalis in cell wall arrangement and plastid organization. Active photosynthesis at ambient temperatures indicates a high physiological activity, despite no cell division being present. Lipid bodies containing the carotenoid astaxanthin, which produces the red color, dominate cells of both species, but are modified differently. While in Chlainomonas sp. astaxanthin is mainly esterified with two fatty acids and is more apolar, in Chamydomonas nivalis, in contrast, less apolar monoesters prevail. PMID:26884467

  17. High-Throughput Genetics Strategies for Identifying New Components of Lipid Metabolism in the Green Alga Chlamydomonas reinhardtii.

    PubMed

    Li, Xiaobo; Jonikas, Martin C

    2016-01-01

    Microalgal lipid metabolism is of broad interest because microalgae accumulate large amounts of triacylglycerols (TAGs) that can be used for biodiesel production (Durrett et al Plant J 54(4):593-607, 2008; Hu et al Plant J 54(4):621-639, 2008). Additionally, green algae are close relatives of land plants and serve as models to understand conserved lipid metabolism pathways in the green lineage. The green alga Chlamydomonas reinhardtii (Chlamydomonas hereafter) is a powerful model organism for understanding algal lipid metabolism. Various methods have been used to screen Chlamydomonas mutants for lipid amount or composition, and for identification of the mutated loci in mutants of interest. In this chapter, we summarize the advantages and caveats for each of these methods with a focus on screens for mutants with perturbed TAG content. We also discuss technical opportunities and new tools that are becoming available for screens of mutants altered in TAG content or perturbed in other processes in Chlamydomonas. PMID:27023238

  18. Multiple facets of anoxic metabolism and hydrogen production in the unicellular green alga Chlamydomonas reinhardtii.

    PubMed

    Grossman, Arthur R; Catalanotti, Claudia; Yang, Wenqiang; Dubini, Alexandra; Magneschi, Leonardo; Subramanian, Venkataramanan; Posewitz, Matthew C; Seibert, Michael

    2011-04-01

    Many microbes in the soil environment experience micro-oxic or anoxic conditions for much of the late afternoon and night, which inhibit or prevent respiratory metabolism. To sustain the production of energy and maintain vital cellular processes during the night, organisms have developed numerous pathways for fermentative metabolism. This review discusses fermentation pathways identified for the soil-dwelling model alga Chlamydomonas reinhardtii, its ability to produce molecular hydrogen under anoxic conditions through the activity of hydrogenases, and the molecular flexibility associated with fermentative metabolism that has only recently been revealed through the analysis of specific mutant strains. PMID:21563367

  19. Treatment with NaHSO3 greatly enhances photobiological H2 production in the green alga Chlamydomonas reinhardtii.

    PubMed

    Ma, Weimin; Chen, Ming; Wang, Lianjun; Wei, Lanzhen; Wang, Quanxi

    2011-09-01

    Treatment with NaHSO3 induces a 10-fold increase in H2 photoproduction in the filamentous N2-fixing cyanobacterium Anabaena sp. strain PCC 7120. However, it is unclear whether this treatment also increases H2 photoproduction in green alga. In this study, treatment with 13 mM NaHSO3 resulted in about a 200-fold increase in H2 production in Chlamydomonas reinhardtii, and this increase was most probably the result of reduced O2 content and enhanced hydrogenase activity. Compared to the conventional strategy of sulfur deprivation, NaHSO3 treatment results in a higher maximum rate of H2 photoproduction, greater efficiency of conversion of light energy into H2, shorter half-time to produce the maximum accumulated H2 levels, and reduced costs because no centrifugation is involved. We therefore conclude that NaHSO3 treatment is an efficient, rapid, and economic strategy for improving photobiological H2 production in the green alga C. reinhardtii. PMID:21489780

  20. A simple, low-cost method for chloroplast transformation of the green alga Chlamydomonas reinhardtii.

    PubMed

    Economou, Chloe; Wannathong, Thanyanan; Szaub, Joanna; Purton, Saul

    2014-01-01

    The availability of routine techniques for the genetic manipulation of the chloroplast genome of Chlamydomonas reinhardtii has allowed a plethora of reverse-genetic studies of chloroplast biology using this alga as a model organism. These studies range from fundamental investigations of chloroplast gene function and regulation to sophisticated metabolic engineering programs and to the development of the algal chloroplast as a platform for producing high-value recombinant proteins. The established method for delivering transforming DNA into the Chlamydomonas chloroplast involves microparticle bombardment, with the selection of transformant lines most commonly involving the use of antibiotic resistance markers. In this chapter we describe a simpler and cheaper delivery method in which cell/DNA suspensions are agitated with glass beads: a method that is more commonly used for nuclear transformation of Chlamydomonas. Furthermore, we highlight the use of an expression vector (pASapI) that employs an endogenous gene as a selectable marker, thereby avoiding the contentious issue of antibiotic resistance determinants in transgenic lines. PMID:24599870

  1. Growth of the green algae Chlamydomonas reinhardtii under red and blue lasers

    NASA Astrophysics Data System (ADS)

    Kuwahara, Sara S.; Cuello, Joel L.; Myhre, Graham; Pau, Stanley

    2011-03-01

    Red and blue lasers, holding promise as an electric light source for photosynthetic systems on account of being true monochromatic, high-power, and having high electrical-conversion efficiency, were employed in growing a green alga, Chlamydomonas reinhardtii. The laser treatments tested included: 655-nm Red; 680-nm Red; 655-nm Red+474-nm Blue and 680-nm Red+474-nm Blue. A white cold cathode lamp with spectral output similar to that of white fluorescent lamp served as control. C. reinhardtii successfully grew and divided under the 655 and 680-nm red lasers as well as under the white-light control. Supplementing either red with blue laser, however, resulted in increased algae cell count that significantly exceeded those under both red lasers and the white-light control on average by 241%.

  2. A rapid, modular and marker-free chloroplast expression system for the green alga Chlamydomonas reinhardtii.

    PubMed

    Bertalan, Ivo; Munder, Matthias C; Weiß, Caroline; Kopf, Judith; Fischer, Dirk; Johanningmeier, Udo

    2015-02-10

    In search of alternative expression platforms heterologous protein production in microalgae has gained increasing importance in the last years. Particularly, the chloroplast of the green alga Chlamydomonas reinhardtii has been adopted to successfully express foreign proteins like vaccines and antibodies. However, when compared with other expression systems, the development of the algal chloroplast to a powerful production platform for recombinant proteins is still in its early stages. In an effort to further improve methods for a reliable and rapid generation of transplastomic Chlamydomonas strains we constructed the key plasmid pMM2 containing the psbA gene and a multiple cloning site for foreign gene insertion. The psbA gene allows a marker-free selection procedure using as a recipient the Fud7 strain of Chlamydomonas, which grows on media containing acetate as a carbon source, but is unable to grow photoautotrophically due to the lack of an intact psbA gene. Biolistic transformation of Fud7 with vectors containing this gene restores photoautotrophic growth and thus permits selection in the light on media without carbon sources and antibiotics. The multiple cloning site with a BsaI recognition sequence allows type IIs restriction enzyme-based modular cloning which rapidly generates new gene constructs without sequences, which could influence the expression and characteristics of the foreign protein. In order to demonstrate the feasibility of this approach, a codon optimized version of the gene for the bacterial protein MPT64 has been integrated into the plastome. Several strains with different promoter/UTR combinations show a stable expression of the HA tagged MPT64 protein in Chlamydomonas chloroplasts. PMID:25554634

  3. Novel shuttle markers for nuclear transformation of the green alga Chlamydomonas reinhardtii.

    PubMed

    Meslet-Cladière, Laurence; Vallon, Olivier

    2011-12-01

    The green alga Chlamydomonas reinhardtii today is a premier model organism for the study of green algae and plants. Yet the efficient engineering of its nuclear genome requires development of new antibiotic resistance markers. We have recoded, based on codon usage in the nuclear genome, the AadA marker that has been used previously for chloroplast transformation. The recoded AadA gene, placed under the control of the HSP70A-RBCS2 hybrid promoter and preceded by the RbcS2 chloroplast-targeting peptide, can be integrated into the nuclear genome by electroporation, conferring resistance to spectinomycin and streptomycin. Transformation efficiency is markedly increased when vector sequences are completely eliminated from the transforming DNA. Antibiotic resistance is stable for several months in the absence of selection pressure. Shuttle markers allowing selection in both Chlamydomonas and Escherichia coli would also be a useful asset. By placing an artificial bacterial promoter and Shine-Dalgarno sequence in frame within the AadA coding sequence, we generated such a shuttle marker. To our surprise, we found that the classical AphVIII construct already functions as a shuttle marker. Finally, we developed a method to introduce the AadA and AphVIII markers into the vector part of the bacterial artificial chromosomes (BACs) of the Chlamydomonas genomic DNA library. Our aim was to facilitate complementation studies whenever the test gene cannot be selected for directly. After transformation of a petC mutant with a modified BAC carrying the AphVIII marker along with the PETC gene in the insert, almost half of the paromomycin-resistant transformants obtained showed restoration of phototrophy, indicating successful integration of the unselected test gene. With AadA, cotransformation was also observed, but with a lower efficiency. PMID:22002656

  4. Characterization of Chlamydomonas reinhardtii phosphatidylglycerophosphate synthase in Synechocystis sp. PCC 6803.

    PubMed

    Hung, Chun-Hsien; Endo, Kaichiro; Kobayashi, Koichi; Nakamura, Yuki; Wada, Hajime

    2015-01-01

    Phosphatidylglycerol (PG) is an indispensable phospholipid class with photosynthetic function in plants and cyanobacteria. However, its biosynthesis in eukaryotic green microalgae is poorly studied. Here, we report the isolation and characterization of two homologs (CrPGP1 and CrPGP2) of phosphatidylglycerophosphate synthase (PGPS), the rate-limiting enzyme in PG biosynthesis, in Chlamydomonas reinhardtii. Heterologous complementation of Synechocystis sp. PCC 6803 pgsA mutant by CrPGP1 and CrPGP2 rescued the PG-dependent growth phenotype, but the PG level and its fatty acid composition were not fully rescued in the complemented strains. As well, oxygen evolution activity was not fully recovered, although electron transport activity of photosystem II was restored to the wild-type level. Gene expression study of CrPGP1 and CrPGP2 in nutrient-starved C. reinhardtii showed differential response to phosphorus and nitrogen deficiency. Taken together, these results highlight the distinct and overlapping function of PGPS in cyanobacteria and eukaryotic algae. PMID:26379630

  5. Characterization of Chlamydomonas reinhardtii phosphatidylglycerophosphate synthase in Synechocystis sp. PCC 6803

    PubMed Central

    Hung, Chun-Hsien; Endo, Kaichiro; Kobayashi, Koichi; Nakamura, Yuki; Wada, Hajime

    2015-01-01

    Phosphatidylglycerol (PG) is an indispensable phospholipid class with photosynthetic function in plants and cyanobacteria. However, its biosynthesis in eukaryotic green microalgae is poorly studied. Here, we report the isolation and characterization of two homologs (CrPGP1 and CrPGP2) of phosphatidylglycerophosphate synthase (PGPS), the rate-limiting enzyme in PG biosynthesis, in Chlamydomonas reinhardtii. Heterologous complementation of Synechocystis sp. PCC 6803 pgsA mutant by CrPGP1 and CrPGP2 rescued the PG-dependent growth phenotype, but the PG level and its fatty acid composition were not fully rescued in the complemented strains. As well, oxygen evolution activity was not fully recovered, although electron transport activity of photosystem II was restored to the wild-type level. Gene expression study of CrPGP1 and CrPGP2 in nutrient-starved C. reinhardtii showed differential response to phosphorus and nitrogen deficiency. Taken together, these results highlight the distinct and overlapping function of PGPS in cyanobacteria and eukaryotic algae. PMID:26379630

  6. An omics based assessment of cadmium toxicity in the green alga Chlamydomonas reinhardtii.

    PubMed

    Jamers, An; Blust, Ronny; De Coen, Wim; Griffin, Julian L; Jones, Oliver A H

    2013-01-15

    The effects of cadmium were assessed in the freshwater alga Chlamydomonas reinhardtii. Algae were exposed to concentrations of 0, 8.1 or 114.8 μM of cadmium and growth rates, gene transcription and metabolite profiles were examined after 48 and 72 h of exposure. In algae exposed to 8.1 μM Cd, several genes were differentially transcribed after 48 h but no adverse growth related effects were detected. A transient effect on both gene transcription patterns and metabolite profiles could be discerned after 48 h of exposure but the majority of these changes disappeared after 72 h. In contrast, all effects were more pronounced at the 114.8 μM cadmium exposure. Here growth was clearly reduced and transcription of a large number of genes involved in oxidative stress defense mechanisms was differentially increased. Metabolites involved in the glutathione synthesis pathway (an important antioxidant defense) were also affected but the effects of cadmium were found to be more pronounced at the transcript level than in the metabolome, suggesting that the former exhibits greater sensitivity toward cadmium exposure. PMID:23063003

  7. Lack of mutagenic activity of crude and refined oils in the unicellular alga Chlamydomonas reinhardtii

    SciTech Connect

    Vandermeulen, J.H.; Lee, R.W.

    1986-02-01

    Over the past several years, an increasing number of studies have presented evidence for the mutagenicity and/or carcinogenic potential of petroleum-derived hydrocarbons. These most usually were obtained with individual hydrocarbons, and using either specialized bacterial strains (e.g. Ames' strains) or mammalian tissue preparations. While providing important insights into mutagenic mechanisms involving xenobiotic compounds, the relevance of these studies to the natural aquatic environment is not always evident. This applies especially to the mutagenic potential of water-soluble fractions of hydrocarbon mixtures, as in whole oils or in complex distillate fractions, and involving typical marine biota. Accordingly, the authors have examined the mutagenic potential of the water-soluble fractions of four oils (two crude oils and two refined oils) using the unicellular haploid alga Chlamydomonas reinhardtii.

  8. The Unicellular Green Alga Chlamydomonas reinhardtii as an Experimental System to Study Chloroplast RNA Metabolism

    NASA Astrophysics Data System (ADS)

    Nickelsen, J.; Kück, U.

    Chloroplasts are typical organelles of photoautotrophic eukaryotic cells which drive a variety of functions, including photosynthesis. For many years the unicellular green alga Chlamydomonas reinhardtii has served as an experimental organism for studying photosynthetic processes. The recent development of molecular tools for this organism together with efficient methods of genetic analysis and the availability of many photosynthesis mutants has now made this alga a powerful model system for the analysis of chloroplast biogenesis. For example, techniques have been developed to transfer recombinant DNA into both the nuclear and the chloroplast genome. This allows both complementation tests and analyses of gene functions in vivo. Moreover, site-specific DNA recombinations in the chloroplast allow targeted gene disruption experiments which enable a "reverse genetics" to be performed. The potential of the algal system for the study of chloroplast biogenesis is illustrated in this review by the description of regulatory systems of gene expression involved in organelle biogenesis. One example concerns the regulation of trans-splicing of chloroplast mRNAs, a process which is controlled by both multiple nuclear- and chloroplast-encoded factors. The second example involves the stabilization of chloroplast mRNAs. The available data lead us predict distinct RNA elements, which interact with trans-acting factors to protect the RNA against nucleolytic attacks.

  9. Alternative photosynthetic electron transport pathways during anaerobiosis in the green alga Chlamydomonas reinhardtii.

    PubMed

    Hemschemeier, Anja; Happe, Thomas

    2011-08-01

    Oxygenic photosynthesis uses light as energy source to generate an oxidant powerful enough to oxidize water into oxygen, electrons and protons. Upon linear electron transport, electrons extracted from water are used to reduce NADP(+) to NADPH. The oxygen molecule has been integrated into the cellular metabolism, both as the most efficient electron acceptor during respiratory electron transport and as oxidant and/or "substrate" in a number of biosynthetic pathways. Though photosynthesis of higher plants, algae and cyanobacteria produces oxygen, there are conditions under which this type of photosynthesis operates under hypoxic or anaerobic conditions. In the unicellular green alga Chlamydomonas reinhardtii, this condition is induced by sulfur deficiency, and it results in the production of molecular hydrogen. Research on this biotechnologically relevant phenomenon has contributed largely to new insights into additional pathways of photosynthetic electron transport, which extend the former concept of linear electron flow by far. This review summarizes the recent knowledge about various electron sources and sinks of oxygenic photosynthesis besides water and NADP(+) in the context of their contribution to hydrogen photoproduction by C. reinhardtii. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts. PMID:21376011

  10. Controlling expression of genes in the unicellular alga Chlamydomonas reinhardtii with a vitamin-repressible riboswitch.

    PubMed

    Ramundo, Silvia; Rochaix, Jean-David

    2015-01-01

    Chloroplast genomes of land plants and algae contain generally between 100 and 150 genes. These genes are involved in plastid gene expression and photosynthesis and in various other tasks. The function of some chloroplast genes is still unknown and some of them appear to be essential for growth and survival. Repressible and reversible expression systems are highly desirable for functional and biochemical characterization of these genes. We have developed a genetic tool that allows one to regulate the expression of any coding sequence in the chloroplast genome of the unicellular alga Chlamydomonas reinhardtii. Our system is based on vitamin-regulated expression of the nucleus-encoded chloroplast Nac2 protein, which is specifically required for the expression of any plastid gene fused to the psbD 5'UTR. With this approach, expression of the Nac2 gene in the nucleus and, in turn, that of the chosen chloroplast gene artificially driven by the psbD 5'UTR, is controlled by the MetE promoter and Thi4 riboswitch, which can be inactivated in a reversible way by supplying vitamin B12 and thiamine to the growth medium, respectively. This system opens interesting possibilities for studying the assembly and turnover of chloroplast multiprotein complexes such as the photosystems, the ribosome, and the RNA polymerase. It also provides a way to overcome the toxicity often associated with the expression of proteins of biotechnological interest in the chloroplast. PMID:25605390

  11. Metabolic Flexibility of the Green Alga Chlamydomonas reinhardtii as Revealed by the Link between State Transitions and Cyclic Electron Flow.

    PubMed

    Finazzi, Giovanni; Forti, Giorgio

    2004-01-01

    In this Review we focus on the conversion of linear photosynthetic electron transport from water to NADP to the cyclic pathway around Photosystem I in the green alga Chlamydomonas reinhardtii. We discuss the strict relationship that exists between the changes in pathways of electron transport and state transitions, i.e., the reversible functional association of light harvesting proteins with one of the two photosystems of oxygenic photosynthesis. Such a link has not been reported in the case of other photosynthetic organisms, where the state transitions do not affect the pathway of electron transport. Rather, they provide a tool to optimise the rate of linear flow. We propose a kinetic-structural model that explains the mechanism of this particular relationship in Chlamydomonas, and discuss the advantages that this peculiar situation gives to the energetic metabolism of this alga. PMID:16143844

  12. The Antarctic Psychrophile Chlamydomonas sp. UWO 241 Preferentially Phosphorylates a Photosystem I-Cytochrome b6/f Supercomplex1[OPEN

    PubMed Central

    Szyszka-Mroz, Beth; Pittock, Paula; Ivanov, Alexander G.; Lajoie, Gilles; Hüner, Norman P.A.

    2015-01-01

    Chlamydomonas sp. UWO 241 (UWO 241) is a psychrophilic green alga isolated from Antarctica. A unique characteristic of this algal strain is its inability to undergo state transitions coupled with the absence of photosystem II (PSII) light-harvesting complex protein phosphorylation. We show that UWO 241 preferentially phosphorylates specific polypeptides associated with an approximately 1,000-kD pigment-protein supercomplex that contains components of both photosystem I (PSI) and the cytochrome b6/f (Cyt b6/f) complex. Liquid chromatography nano-tandem mass spectrometry was used to identify three major phosphorylated proteins associated with this PSI-Cyt b6/f supercomplex, two 17-kD PSII subunit P-like proteins and a 70-kD ATP-dependent zinc metalloprotease, FtsH. The PSII subunit P-like protein sequence exhibited 70.6% similarity to the authentic PSII subunit P protein associated with the oxygen-evolving complex of PSII in Chlamydomonas reinhardtii. Tyrosine-146 was identified as a unique phosphorylation site on the UWO 241 PSII subunit P-like polypeptide. Assessment of PSI cyclic electron transport by in vivo P700 photooxidation and the dark relaxation kinetics of P700+ indicated that UWO 241 exhibited PSI cyclic electron transport rates that were 3 times faster and more sensitive to antimycin A than the mesophile control, Chlamydomonas raudensis SAG 49.72. The stability of the PSI-Cyt b6/f supercomplex was dependent upon the phosphorylation status of the PsbP-like protein and the zinc metalloprotease FtsH as well as the presence of high salt. We suggest that adaptation of UWO 241 to its unique low-temperature and high-salt environment favors the phosphorylation of a PSI-Cyt b6/f supercomplex to regulate PSI cyclic electron transport rather than the regulation of state transitions through the phosphorylation of PSII light-harvesting complex proteins. PMID:26169679

  13. The Antarctic Psychrophile Chlamydomonas sp. UWO 241 Preferentially Phosphorylates a Photosystem I-Cytochrome b6/f Supercomplex.

    PubMed

    Szyszka-Mroz, Beth; Pittock, Paula; Ivanov, Alexander G; Lajoie, Gilles; Hüner, Norman P A

    2015-09-01

    Chlamydomonas sp. UWO 241 (UWO 241) is a psychrophilic green alga isolated from Antarctica. A unique characteristic of this algal strain is its inability to undergo state transitions coupled with the absence of photosystem II (PSII) light-harvesting complex protein phosphorylation. We show that UWO 241 preferentially phosphorylates specific polypeptides associated with an approximately 1,000-kD pigment-protein supercomplex that contains components of both photosystem I (PSI) and the cytochrome b₆/f (Cyt b₆/f) complex. Liquid chromatography nano-tandem mass spectrometry was used to identify three major phosphorylated proteins associated with this PSI-Cyt b₆/f supercomplex, two 17-kD PSII subunit P-like proteins and a 70-kD ATP-dependent zinc metalloprotease, FtsH. The PSII subunit P-like protein sequence exhibited 70.6% similarity to the authentic PSII subunit P protein associated with the oxygen-evolving complex of PSII in Chlamydomonas reinhardtii. Tyrosine-146 was identified as a unique phosphorylation site on the UWO 241 PSII subunit P-like polypeptide. Assessment of PSI cyclic electron transport by in vivo P700 photooxidation and the dark relaxation kinetics of P700(+) indicated that UWO 241 exhibited PSI cyclic electron transport rates that were 3 times faster and more sensitive to antimycin A than the mesophile control, Chlamydomonas raudensis SAG 49.72. The stability of the PSI-Cyt b₆/f supercomplex was dependent upon the phosphorylation status of the PsbP-like protein and the zinc metalloprotease FtsH as well as the presence of high salt. We suggest that adaptation of UWO 241 to its unique low-temperature and high-salt environment favors the phosphorylation of a PSI-Cyt b₆/f supercomplex to regulate PSI cyclic electron transport rather than the regulation of state transitions through the phosphorylation of PSII light-harvesting complex proteins. PMID:26169679

  14. Toxicity assessment of manufactured nanomaterials using the unicellular green alga Chlamydomonas reinhardtii.

    PubMed

    Wang, Jiangxin; Zhang, Xuezhi; Chen, Yongsheng; Sommerfeld, Milton; Hu, Qiang

    2008-10-01

    With the rapid development of nanotechnology, there is an increasing risk of human and environmental exposure to nanotechnology-based materials and products. As water resources are particularly vulnerable to direct and indirect contamination of nonomaterials (NMs), the potential toxicity and environmental implication of NMs to aquatic organisms must be evaluated. In this study, we assessed potential toxicity of two commercially used NMs, titanium dioxide (TiO(2)) and quantum dots (QDs), using the unicellular green alga Chlamydomonas reinhartii as a model system. The response of the organism to NMs was assessed at physiological, biochemical, and molecular genetic levels. Growth kinetics showed that growth inhibition occurred during the first two to three days of cultivation in the presence of TiO(2) or QDs. Measurements of lipid peroxidation measurement indicated that oxidative stress of the cells occurred as early as 6 h after exposure to TiO(2) or QDs. The transcriptional expression profiling of four stress response genes (sod1, gpx, cat, and ptox2) revealed that transient up-regulation of these genes occurred in cultures containing as low as 1.0 mg L(-1) of TiO(2) or 0.1 mg L(-1) of QDs, and the maximum transcripts of cat, sod1, gpx, and ptox2 occurred at 1.5, 3, 3, and 6 h, respectively, and were proportional to the initial concentration of the NMs. As the cultures continued, recovery in growth was observed and the extent of recovery, as indicated by the final cell concentration, was dosage-dependent. QDs were found to be more toxic to Chlamydomonas cells than TiO(2) under our experimental conditions. PMID:18768203

  15. Growth of Chlamydomonas reinhardtii in acetate-free medium when co-cultured with alginate-encapsulated, acetate-producing strains of Synechococcus sp. PCC 7002

    SciTech Connect

    Therien, Jesse B.; Zadvornyy, Oleg A.; Posewitz, Matthew C.; Bryant, Donald A.; Peters, John W.

    2014-10-18

    The model alga Chlamydomonas reinhardtii requires acetate as a co-substrate for optimal production of lipids, and the addition of acetate to culture media has practical and economic implications for algal biofuel production. We demonstrate the growth of C. reinhardtii on acetate provided by mutant strains of the cyanobacterium Synechococcus sp. PCC7002.

  16. Uranium accumulation and toxicity in the green alga Chlamydomonas reinhardtii is modulated by pH.

    PubMed

    Lavoie, Michel; Sabatier, Sébastien; Garnier-Laplace, Jacqueline; Fortin, Claude

    2014-06-01

    The effects of pH on metal uptake and toxicity in aquatic organisms are currently poorly understood and remain an evolving topic in studies about the biotic ligand model (BLM). In the present study, the authors investigated how pH may influence long-term (4 d) uranium (U) accumulation and chronic toxicity in batch cultures of the freshwater green alga Chlamydomonas reinhardtii. The toxicity expressed as a function of the free uranyl ion was much greater at pH 7 (effective concentration, 50% [EC50] = 1.8 × 10(-9)  M UO2 (2+) ) than at pH 5 (EC50 = 1.2 × 10(-7)  M UO2 (2+) ). The net accumulation rate of U in algal cells was much higher at pH 7 than at pH 5 for the same free [UO2 (2+) ], but the cells exposed at pH 5 were also more sensitive to intracellular U than the cells at pH 7 with EC50s of 4.0 × 10(-15) and 7.1 × 10(-13)  mol of internalized U cell(-1) , respectively. The higher cellular sensitivity to U at pH 5 than at pH 7 could be explained partly by the increase in cytosolic U binding to algal soluble proteins or enzymes at pH 5 as observed by subcellular fractionation. To predict U accumulation and toxicity in algae accurately, the important modulating effects of pH on U accumulation and U cellular sensitivity should be considered in the BLM. PMID:24596137

  17. Examination of chlorophyll fluorescence decay kinetics in sulfur deprived algae Chlamydomonas reinhardtii.

    PubMed

    Volgusheva, A A; Zagidullin, V E; Antal, T K; Korvatovsky, B N; Krendeleva, T E; Paschenko, V Z; Rubin, A B

    2007-06-01

    Chlorophyll fluorescence decay kinetics was measured in sulfur deprived cells of green alga Chlamydomonas reinhardtii with a home made picosecond fluorescence laser spectrometer. The measurements were carried out on samples either shortly adapted to the dark ('Fo conditions') or treated to reduce Qa ('Fm conditions'). Bi-exponential fitting of decay kinetics was applied to distinguish two components one of them related to energy trapping (fast component) and the other to charge stabilization and recombination in PS 2 reaction centers (slow component). It was found that the slow component yield increased by 2.0 and 1.2 times when measured under 'Fo' and 'Fm conditions', respectively, in sulfur deprived cells as compared to control ones. An additional rapid rise of the slow component yield was observed when incubation was carried out in a sealed bioreactor and cell culture turned to anaerobic conditions. The obtained results strongly indicate the existence of the redox control of PS 2 activity during multiphase adaptation of C. reinhardtii to sulfur deficiency stress. Probable mechanisms responsible for the observed increased recombinant fluorescence yield in starved cells are discussed. PMID:17543273

  18. Fatty acid patterns in Chlamydomonas sp. as a marker for nutritional regimes and temperature under extremely acidic conditions.

    PubMed

    Poerschmann, J; Spijkerman, E; Langer, U

    2004-07-01

    Fatty acid profiles were used to characterize nutritional pathways in Chlamydomonas sp. isolated from an acidic mining lake (pH 2.7). Surprisingly, profiles of Chlamydomonas sp. grown in the lab under photoautotrophic, mixotrophic, and heterotrophic conditions at in situ deep strata lake water temperatures (8 degrees C) were very similar, polyunsaturated fatty acids including alpha-linolenic acid (18:3omega3) and 16:4omega3 along with palmitic acid (16:0) being most abundant. Therefore, heterotrophic growth of Chlamydomonas sp. at low temperatures can result in high concentrations of polyunsaturated fatty acids, as previously only described for some psychrophilic bacteria. By contrast, the cultivation of isolated Chlamydomonas sp. at 20 degrees C, reflecting surface water temperatures, provided fatty acid patterns characteristic of the nutrition strategy applied: the concentration of polyunsaturated fatty acids decreased when the growth pathway changed from photoautotrophic via mixotrophic to heterotrophic. Total fatty acid concentration also diminished in this order. Principal component analysis confirmed the significance of FA profiling to mirror nutritional pathways. Lake-water analysis revealed low concentrations of dissolved organic carbon, mainly consisting of polymeric fulvic acids that are unable to support heterotrophic growth of Chlamydomonas sp. Polymeric fulvic acids present in the deeper strata of the lake turned out to be formed in situ on the basis of organic monomers including reduced sulfur-containing ones, as revealed by thermochemolysis and pyrolysis. Growth of Chlamydomonas sp. in the deep chlorophyll maximum is therefore assumed to mainly result from photosynthesis, despite very low photon densities. Phytol-including metabolites proved to be significant biomarkers to indicate the nutritional pathway of Chlamydomonas sp. alpha, omega-Dicarboxylic acids-light-induced degradation products of unsaturated fatty acids-appeared to be good indicators

  19. Lumped pathway metabolic model of organic carbon accumulation and mobilization by the alga Chlamydomonas reinhardtii.

    PubMed

    Guest, Jeremy S; van Loosdrecht, Mark C M; Skerlos, Steven J; Love, Nancy G

    2013-04-01

    Phototrophic microorganisms have significant potential as bioenergy feedstocks, but the sustainability of large-scale cultivation will require the use of wastewater as a renewable resource. A key barrier to this advancement is a lack of bioprocess understanding that would enable the design and implementation of efficient and resilient mixed community, naturally lit cultivation systems. In this study, a lumped pathway metabolic model (denoted the phototrophic process model or PPM) was developed for mixed phototrophic communities subjected to day/night cycling. State variables included functional biomass (XCPO), stored carbohydrates (XCH), stored lipids (XLI), nitrate (SNO), phosphate (SP), and others. PPM metabolic reactions and stoichiometry were based on Chlamydomonas reinhardtii , but experiments for model calibration and validation were performed in flat panel photobioreactors (PBRs) originally inoculated with biomass from a phototrophic system at a wastewater treatment plant. PBRs were operated continuously as cyclostats to poise cells for intrinsic kinetic parameter estimation in batch studies, which included nutrient-available conditions in light and dark as well as nitrogen-starved and phosphorus-starved conditions in light. The model was calibrated and validated and was shown to be a reasonable predictor of growth, lipid and carbohydrate storage, and lipid and carbohydrate mobilization by a mixed microbial community. PMID:23452258

  20. Regulation of cellular manganese and manganese transport rates in the unicellular alga Chlamydomonas

    SciTech Connect

    Sunda, W.G.; Huntsman, S.A.

    1985-01-01

    The cellular accumulation and uptake kinetics of manganese by Chlamydomonas sp. were studied in model chelate buffer systems. Cellular manganese concentrations and uptake rates were related to the computed free manganese ion concentration and were independent of the total or chelated manganese concentration. Cellular manganese was constant at about 1 mmol liter/sup -1/ of cellular volume at free manganese ion concentrations of 10/sup -7/ /sup 6/-10/sup -6/ /sup 3/ mol liter/sup -1/ and decreased below this range. Manganese uptake rates followed saturation kinetics and V/sub max/, but not K/sub s/, varied with the free manganese ion concentration in the growth medium. V/sub max/ appeared to be under negative feedback control and increased with decreasing manganese ion concentration. Variations of up to 30-fold in this parameter seemed to be instrumental in limiting the variation in cellular manganese to a sixfold range despite a 1000-fold variation in free manganese ion concentration in the growth medium.

  1. Transcriptional and cellular responses of the green alga Chlamydomonas reinhardtii to perfluoroalkyl phosphonic acids.

    PubMed

    Sanchez, David; Houde, Magali; Douville, Mélanie; De Silva, Amila O; Spencer, Christine; Verreault, Jonathan

    2015-03-01

    Perfluoroalkyl phosphonic acids (PFPAs), a new class of perfluoroalkyl substances used primarily in the industrial sector as surfactants, were recently detected in surface water and wastewater treatment plant effluents. Toxicological effects of PFPAs have as yet not been investigated in aquatic organisms. The objective of the present study was to evaluate the effects of perfluorooctylphosphonic acid (C8-PFPA) and perfluorodecylphosphonic acid (C10-PFPA) exposure (31-250μg/L) on Chlamydomonas reinhardtii using genomic (qRT-PCR), biochemical (reactive oxygen species production (ROS) and lipid peroxidation), and physiological (cellular viability) indicators. After 72h of exposure, no differences were observed in cellular viability for any of the two perfluorochemicals. However, increase in ROS concentrations (36% and 25.6% at 125 and 250μg/L, respectively) and lipid peroxidation (35.5% and 35.7% at 125 and 250μg/L, respectively) was observed following exposure to C10-PFPA. C8-PFPA exposure did not impact ROS production and lipid peroxidation in algae. To get insights into the molecular response and modes of action of PFPA toxicity, qRT-PCR-based assays were performed to analyze the transcription of genes related to antioxidant responses including superoxide dismutase (SOD-1), glutathione peroxidase (GPX), catalase (CAT), glutathione S-transferase (GST), and ascorbate peroxidase (APX I). Genomic analyses revealed that the transcription of CAT and APX I was up-regulated for all the C10-PFPA concentrations. In addition, PFPAs were quantified in St. Lawrence River surface water samples and detected at concentrations ranging from 250 to 850pg/L for C8-PFPA and 380 to 650pg/L for C10-PFPA. This study supports the prevalence of PFPAs in the aquatic environment and suggests potential impacts of PFPA exposure on the antioxidant defensive system in C. reinhardtii. PMID:25621396

  2. PLASTICITY OF THE PSYCHROPHILIC GREEN ALGA CHLAMYDOMONAS RAUDENSIS (UWO 241) (CHLOROPHYTA) TO SUPRAOPTIMAL TEMPERATURE STRESS(1).

    PubMed

    Possmayer, Marc; Berardi, Gino; Beall, Benjamin F N; Trick, Charles G; Hüner, Norman P A; Maxwell, Denis P

    2011-10-01

    Chlamydomonas raudensis  H. Ettl (UWO 241) is a psychrophilic green alga endemic to Lake Bonney, Antarctica. The objective of this study was to investigate the response of UWO 241 to incubation at 24°C, a temperature close to optimum for related mesophilic species. Using chl a fluorescence analysis, shifting cells from a growth temperature of 10°C-24°C resulted in a decline in PSII photochemical efficiency with light energy being directed away from photochemistry and toward dissipative pathways. Using the SYTOX Green assay, it was determined that UWO 241 cells die when incubated at 24°C under growth irradiance with a half-time of 34.9 h. The role of light in cell death was minor as cell death occurred in darkness at 24°C with a half-time of 43.7 h. To examine the plasticity of UWO 241 to temperature stress, 10°C-grown cells were shifted to 24°C for 12 h and then returned to 10°C to recover. The 12 h incubation at 24°C, which resulted in <10% cell death, led to declines in both light-saturated rates of photosynthesis and respiration, PSII photochemistry and energy partitioning, and changes to transcript abundances-those associated with the light-harvesting protein of PSII and ferredoxin declining rapidly, whereas transcripts of specific heat-shock proteins (HSPs) increased. Within 24-48 h of being transferred back to 10°C, all parameters returned to levels occurring in 10°C-grown cells. This research shows, for the first time, that 24°C is a temperature that is lethal to UWO 241, and yet this organism displays considerable physiological and molecular plasticity. PMID:27020192

  3. Mastoparan-induced programmed cell death in the unicellular alga Chlamydomonas reinhardtii

    PubMed Central

    Yordanova, Zhenya P.; Woltering, Ernst J.; Kapchina-Toteva, Veneta M.; Iakimova, Elena T.

    2013-01-01

    Background and Aims Under stress-promoting conditions unicellular algae can undergo programmed cell death (PCD) but the mechanisms of algal cellular suicide are still poorly understood. In this work, the involvement of caspase-like proteases, DNA cleavage and the morphological occurrence of cell death in wasp venom mastoparan (MP)-treated Chlamydomonas reinhardtii were studied. Methods Algal cells were exposed to MP and cell death was analysed over time. Specific caspase inhibitors were employed to elucidate the possible role of caspase-like proteases. YVADase activity (presumably a vacuolar processing enzyme) was assayed by using a fluorogenic caspase-1 substrate. DNA breakdown was evaluated by DNA laddering and Comet analysis. Cellular morphology was examined by confocal laser scanning microscopy. Key Results MP-treated C. reinhardtii cells expressed several features of necrosis (protoplast shrinkage) and vacuolar cell death (lytic vesicles, vacuolization, empty cell-walled corpse-containing remains of digested protoplast) sometimes within one single cell and in different individual cells. Nucleus compaction and DNA fragmentation were detected. YVADase activity was rapidly stimulated in response to MP but the early cell death was not inhibited by caspase inhibitors. At later time points, however, the caspase inhibitors were effective in cell-death suppression. Conditioned medium from MP-treated cells offered protection against MP-induced cell death. Conclusions In C. reinhardtii MP triggered PCD of atypical phenotype comprising features of vacuolar and necrotic cell deaths, reminiscent of the modality of hypersensitive response. It was assumed that depending on the physiological state and sensitivity of the cells to MP, the early cell-death phase might be not mediated by caspase-like enzymes, whereas later cell death may involve caspase-like-dependent proteolysis. The findings substantiate the hypothesis that, depending on the mode of induction and sensitivity of

  4. Identification of AGO3-Associated miRNAs and Computational Prediction of Their Targets in the Green Alga Chlamydomonas reinhardtii

    PubMed Central

    Voshall, Adam; Kim, Eun-Jeong; Ma, Xinrong; Moriyama, Etsuko N.; Cerutti, Heriberto

    2015-01-01

    The unicellular green alga Chlamydomonas reinhardtii harbors many types of small RNAs (sRNAs) but little is known about their role(s) in the regulation of endogenous genes and cellular processes. To define functional microRNAs (miRNAs) in Chlamydomonas, we characterized sRNAs associated with an argonaute protein, AGO3, by affinity purification and deep sequencing. Using a stringent set of criteria for canonical miRNA annotation, we identified 39 precursor miRNAs, which produce 45 unique, AGO3-associated miRNA sequences including 13 previously reported miRNAs and 32 novel ones. Potential miRNA targets were identified based on the complementarity of miRNAs with candidate binding sites on transcripts and classified, depending on the extent of complementarity, as being likely to be regulated through cleavage or translational repression. The search for cleavage targets identified 74 transcripts. However, only 6 of them showed an increase in messenger RNA (mRNA) levels in a mutant strain almost devoid of sRNAs. The search for translational repression targets, which used complementarity criteria more stringent than those empirically required for a reduction in target protein levels, identified 488 transcripts. However, unlike observations in metazoans, most predicted translation repression targets did not show appreciable changes in transcript abundance in the absence of sRNAs. Additionally, of three candidate targets examined at the protein level, only one showed a moderate variation in polypeptide amount in the mutant strain. Our results emphasize the difficulty in identifying genuine miRNA targets in Chlamydomonas and suggest that miRNAs, under standard laboratory conditions, might have mainly a modulatory role in endogenous gene regulation in this alga. PMID:25769981

  5. Interactive effects of copper oxide nanoparticles and light to green alga Chlamydomonas reinhardtii.

    PubMed

    Cheloni, Giulia; Marti, Elodie; Slaveykova, Vera I

    2016-01-01

    The present study explores the effect of light with different spectral composition on the stability of CuO-nanoparticle (CuO-NP) dispersions and their effects to green alga Chlamydomonas reinhardtii. The results showed that simulated natural light (SNL) and light with enhanced UVB radiation (UVR*) do not affect the dissolution of CuO-NPs as compared to light irradiation conditions typically used in laboratory incubator (INC). Comparable values of ζ-potential and hydrodynamic size during 24h were found under all studied conditions. Concentrations of CuO-NPs below 1mgL(-1) do not attenuate the light penetration in the algal suspensions in comparison with NP-free system. Exposure to a combination of 8μgL(-1) or 0.8mgL(-1) CuO-NPs and INC or SNL has no significant effect on the algal growth inhibition, algal fluorescence and membrane integrity under short-term exposure. However, an enhancement of the percentage of cells experiencing oxidative stress was observed upon exposure to 0.8mgL(-1) CuO-NPs and SNL for 4 and 8h. Combination of UVR* and 0.8mgL(-1) CuO-NPs resulted in synergistic effects for all biological endpoints. Despite the photocatalytic properties of CuO-NPs no significant increase in abiotic reactive oxygen species (ROS) production under simulated solar radiation was observed suggesting that the synergistic effect observed might be correlated to other factors than CuO-NP-mediated ROS photoproduction. Tests performed with CuSO4 confirmed the important role of dissolution as toxicity driving force for lower CuO-NP concentration. However, they failed to clarify the contribution of dissolved Cu on the combined effects at 0.8mgL(-1) CuO-NPs. The results point out the necessity of taking into account the possible interactions between ENPs and changing light conditions when evaluating the potential effects of ENPs to phytoplankton in natural waters. PMID:26655656

  6. Cultivation of Monoraphidium sp., Chlorella sp. and Scenedesmus sp. algae in Batch culture using Nile tilapia effluent.

    PubMed

    Guerrero-Cabrera, Luis; Rueda, José A; García-Lozano, Hiram; Navarro, A Karin

    2014-06-01

    Monoraphidium sp., Chlorella sp. and Scenedesmus sp. algae were cultured in three volumes of Tilapia Effluent Medium (TEM) in comparison with the Bold Basal Medium (BBM) (Nichols and Bold, 1965). Specific growth rate (μ'), biomass dry productivity (Q), volumetric productivity (Qv) as well as lipid and protein content were measured. Then, volumetric productivities for both lipids and proteins were calculated (QVL and QVP). In Scenedesmus sp., BBM produced higher μ' and Qv than TEM in 1.5L volume. Chlorella sp. showed a higher QVL for BBM than TEM. Any observed difference in protein or lipid productivities among volumes was in favor of a greater productivity for 1.5L volume. Even when TEM had a larger protein content in Chlorella sp. than BBM, QVP was not different. Current results imply that TEM can be used as an alternative growth medium for algae when using Batch cultures, yet productivity is reduced. PMID:24736090

  7. Refactoring the Six-Gene Photosystem II Core in the Chloroplast of the Green Algae Chlamydomonas reinhardtii.

    PubMed

    Gimpel, Javier A; Nour-Eldin, Hussam H; Scranton, Melissa A; Li, Daphne; Mayfield, Stephen P

    2016-07-15

    Oxygenic photosynthesis provides the energy to produce all food and most of the fuel on this planet. Photosystem II (PSII) is an essential and rate-limiting component of this process. Understanding and modifying PSII function could provide an opportunity for optimizing photosynthetic biomass production, particularly under specific environmental conditions. PSII is a complex multisubunit enzyme with strong interdependence among its components. In this work, we have deleted the six core genes of PSII in the eukaryotic alga Chlamydomonas reinhardtii and refactored them in a single DNA construct. Complementation of the knockout strain with the core PSII synthetic module from three different green algae resulted in reconstitution of photosynthetic activity to 85, 55, and 53% of that of the wild-type, demonstrating that the PSII core can be exchanged between algae species and retain function. The strains, synthetic cassettes, and refactoring strategy developed for this study demonstrate the potential of synthetic biology approaches for tailoring oxygenic photosynthesis and provide a powerful tool for unraveling PSII structure-function relationships. PMID:26214707

  8. Contrasting ecotoxicity effects of zinc on growth and photosynthesis in a neutrophilic alga (Chlamydomonas reinhardtii) and an extremophilic alga (Cyanidium caldarium).

    PubMed

    Mikulic, Paulina; Beardall, John

    2014-10-01

    This study aimed to determine the contrasting ecotoxicity effects of zinc on growth and photosynthesis in a neutrophilic (Chlamydomonas reinhardtii) and an extremophilic (Cyanidium caldarium) alga. Experiments were carried out to see if cells acclimated to zinc would respond differently to cells that were unexposed to zinc. The study also aimed to see if extremophiles displayed different acclimation properties to neutrophiles. Results showed that the neutrophilic alga C. reinhardtii, was more susceptible to free zinc and had a lower IC50 value than the extremophile, however its stress response protected the photosynthetic apparatus. Upon acclimation, the photosynthetic abilities of C. reinhardtii were not significantly compromised when exposed to toxic levels of free zinc. On the other hand, C. caldarium had a stress response which allowed it to tolerate significantly higher amounts of free zinc in its environment compared to C. reinhardtii , however the stress response did not protect the photosynthetic apparatus, and upon acclimation C. caldarium was no better equipped to protect its photosynthetic integrity than unexposed cells. PMID:25048933

  9. Survival and proliferation characteristics of the microalga Chlamydomonas sp. ICE-L after hypergravitational stress pretreatment

    NASA Astrophysics Data System (ADS)

    Gao, Zhengquan; Li, Demao; Meng, Chunxiao; Xu, Dong; Zhang, Xiaowen; Ye, Naihao

    2013-09-01

    Seeking extraterrestrial life, transferring between planets, even migrating to other planets attracts more and more attention of public and scientists. However, to make it clear for the ability to survive the forces studies is prerequisite to enable the speculations by natural means. Gravity is a critical force involved in all the life on Earth and, possibly, others planets. Organisms have been grown in microgravity habitats and in centrifuges to characterize the biological response to a range of gravitational forces and radiation levels in space and on Earth. However, little is known about the profiles of eukaryotic life under conditions of hyperacceleration attributable to extreme gravities. In this study, a eukaryotic extremophile, the Antarctic green microalga Chlamydomonas sp. ICE-L, showed amazing proliferation capacity during and after hypergravitational stress for 30 min to 48 h at 110,200, 423,400, and 670,800g. These extreme gravities also had profound effects on viability, reproduction rate, photosynthesis efficiency, and gene transcriptional expression of this microalga. Most notably, all three supergravities efficiently stimulated algal cell division, but the greater the centrifugal force and the longer the duration of treatment, the lower the viable rate and breeding potential of samples in the following incubation. These results illustrated Chlamydomonas sp. ICE-L is a useful eukaryotic model system candidate for space research. Further studies could provide new insight into the physical limits of life and its evolution and enhance the possibility for interstellar space travel and the quest for extraterrestrial life according to panspermia theory. Also, it indicated that life come from the outer space is not always prokaryotes but may be eukaryotes.

  10. The ferredoxin-thioredoxin system of a green alga, Chlamydomonas reinhardtii: identification and characterization of thioredoxins and ferredoxin-thioredoxin reductase components

    NASA Technical Reports Server (NTRS)

    Huppe, H. C.; de Lamotte-Guery, F.; Buchanan, B. B.

    1990-01-01

    The components of the ferredoxin-thioredoxin (FT) system of Chlamydomonas reinhardtii have been purified and characterized. The system resembled that of higher plants in consisting of a ferredoxin-thioredoxin reductase (FTR) and two types of thioredoxin, a single f and two m species, m1 and m2. The Chlamydomonas m and f thioredoxins were antigenically similar to their higher-plant counterparts, but not to one another. The m thioredoxins were recognized by antibodies to both higher plant m and bacterial thioredoxins, whereas the thioredoxin f was not. Chlamydomonas thioredoxin f reacted, although weakly, with the antibody to spinach thioredoxin f. The algal thioredoxin f differed from thioredoxins studied previously in behaving as a basic protein on ion-exchange columns. Purification revealed that the algal thioredoxins had molecular masses (Mrs) typical of thioredoxins from other sources, m1 and m2 being 10700 and f 11500. Chlamydomonas FTR had two dissimilar subunits, a feature common to all FTRs studied thus far. One, the 13-kDa ("similar") subunit, resembled its counterpart from other sources in both size and antigenicity. The other, 10-kDa ("variable") subunit was not recognized by antibodies to any FTR tested. When combined with spinach, (Spinacia oleracea L.) thylakoid membranes, the components of the FT system functioned in the light activation of the standard target enzymes from chloroplasts, corn (Zea mays L.) NADP-malate dehydrogenase (EC 1.1.1.82) and spinach fructose 1,6-bisphosphatase (EC 3.1.3.11) as well as the chloroplast-type fructose 1,6-bisphosphatase from Chlamydomonas. Activity was greatest if ferredoxin and other components of the FT system were from Chlamydomonas. The capacity of the Chlamydomonas FT system to activate autologous FBPase indicates that light regulates the photosynthetic carbon metabolism of green algae as in other oxygenic photosynthetic organisms.

  11. Induction to oxidative stress by saxitoxin investigated through lipid peroxidation in Neuro 2A cells and Chlamydomonas reinhardtii alga.

    PubMed

    Melegari, Silvia P; Perreault, François; Moukha, Serge; Popovic, Radovan; Creppy, Edmond E; Matias, William G

    2012-09-01

    Saxitoxin (STX) is a cyanotoxin, which can cause neurotoxic effects and induce ecological changes in aquatic environments, a potential risk to public and environmental health. Many studies of cytotoxicity on animal cells and algae have been performed, although few compare the toxic effects between the two models. In this sense, we investigated the oxidative stress induced by STX (0.4-3.0 nM) in two different cellular models: Neuro-2A (N2A) cells and Chlamydomonas reinhardtii alga by quantification of malondialdehyde (MDA) levels as indicative of lipid peroxidation (LPO). Also was evaluated the antioxidant defense of these cells systems after exposure to STX by the addition of antioxidants in N2A cells culture, and by the measure of antioxidants enzymes activity in C. reinhardtii cells. The MDA levels of N2A cells increased from 15% to 113% for 0.4 and 3.0 nM of STX, respectively, as compared to control. Superoxide-dismutase and catalase did not appear to protect the cell from STX effect while, in cells treated with vitamin E, the rates of MDA production decreased significantly, except for higher concentrations of STX. No MDA productions were observed in algal cells however some effects on antioxidant enzymes activity were observed when algae were exposed to 3.0 nM STX. Our results indicate that the concentrations of STX that may induce oxidative stress through LPO are different in animal and phytoplankton communities. A combination of algal and animal bioassays should be conducted for reliable assessment of oxidative stress induced by STX. PMID:22546629

  12. Effect of petroleum hydrocarbons on algae

    SciTech Connect

    Bhadauria, S. ); Sengar, R.M.S. ); Mittal, S.; Bhattacharjee, S. )

    1992-01-01

    Algal species (65) were isolated from oil refinery effluent. Twenty-five of these species were cultured in Benecke's medium in a growth chamber, along with controls. Retardation in algal growth, inhibition in algal photosynthesis, and discoloration was observed in petroleum enriched medium. Few forms, viz. Cyclotella sp., Cosmarium sp., and Merismopedia sp. could not survive. The lag phase lengthened by several days and slope of exponential phase was also depressed. Chlamydomonas sp., Scenedesmus sp., Ankistrodesmus sp., Nitzschia sp. and Navicula sp. were comparatively susceptible to petroleum. Depression in carbon fixation, cell numbers, and total dry algal mass was noticeable, showing toxicity to both diatoms and green algae.

  13. Valorization of Rhizoclonium sp. algae via pyrolysis and catalytic pyrolysis.

    PubMed

    Casoni, Andrés I; Zunino, Josefina; Piccolo, María C; Volpe, María A

    2016-09-01

    The valorization of Rhizoclonium sp. algae through pyrolysis for obtaining bio-oils is studied in this work. The reaction is carried out at 400°C, at high contact time. The bio-oil has a practical yield of 35% and is rich in phytol. Besides, it is simpler than the corresponding to lignocellulosic biomass due to the absence of phenolic compounds. This property leads to a bio-oil relatively stable to storage. In addition, heterogeneous catalysts (Al-Fe/MCM-41, SBA-15 and Cu/SBA-15), in contact with algae during pyrolysis, are analyzed. The general trend is that the catalysts decrease the concentration of fatty alcohols and other high molecular weight products, since their mild acidity sites promote degradation reactions. Thus, the amount of light products increases upon the use of the catalysts. Particularly, acetol concentration in the bio-oils obtained from the catalytic pyrolysis with SBA-15 and Cu/SBA-15 is notably high. PMID:27253478

  14. The ultrastructure of a Chlamydomonas reinhardtii mutant strain lacking phytoene synthase resembles that of a colorless alga.

    PubMed

    Inwood, William; Yoshihara, Corinne; Zalpuri, Reena; Kim, Kwang-Seo; Kustu, Sydney

    2008-11-01

    Chlamydomonas reinhardtii strains lacking phytoene synthase, the first enzyme of carotenoid biosynthesis, are white. They lack carotenoid pigments, have very low levels of chlorophyll, and can grow only heterotrophically in the dark. Our electron and fluorescence microscopic studies showed that such a mutant strain (lts1-204) had a proliferated plastid envelope membrane but no stacks of thylakoid membranes within the plastid. It accumulated cytoplasmic compartments that appeared to be autophagous vacuoles filled with membranous material. The lts1 mutants apparently lacked pyrenoid bodies, which normally house ribulose bisphosphate carboxylase-oxygenase (Rubisco), and accumulated many starch granules. Although these mutant strains cannot synthesize the carotenoid and carotenoid-derived pigments present in the phototactic organelle (eyespot), the mutant we examined made a vestigial eyespot that was disorganized and often mislocalized to the posterior end of the cell. The absence of a pyrenoid body, the accumulation of starch, and the disorganization of the eyespot may all result from the absence of thylakoids. The ultrastructure of lts1 mutant strains is similar to but distinct from that of previously described white and yellow mutant strains of C. reinhardtii and is similar to that of naturally colorless algae of the Polytoma group. PMID:19825593

  15. Origin of pronounced differences in 77 K fluorescence of the green alga Chlamydomonas reinhardtii in state 1 and 2.

    PubMed

    Ünlü, Caner; Polukhina, Iryna; van Amerongen, Herbert

    2016-04-01

    In response to changes in the reduction state of the plastoquinone pool in its thylakoid membrane, the green alga Chlamydomonas reinhardtti is performing state transitions: remodelling of its thylakoid membrane leads to a redistribution of excitations over photosystems I and II (PSI and PSII). These transitions are accompanied by marked changes in the 77 K fluorescence spectrum, which form the accepted signature of state transitions. The changes are generally thought to reflect a redistribution of light-harvesting complexes (LHCs) over PSII (fluorescing below 700 nm) and PSI (fluorescing above 700 nm). Here we studied the picosecond fluorescence properties of C. reinhardtti over a broad range of wavelengths with very low excitation intensities (0.2 nJ per laser pulse). Cells were directly used for time-resolved fluorescence measurements at 77 K without further treatment, such as medium exchange with glycerol. It is observed that upon going from state 1 (relatively more fluorescence below 700 nm) to state 2 (relatively more fluorescence above 700 nm), a large part of the fluorescence of LHC/PSII becomes substantially quenched in concurrence with LHC detachment from PSII, whereas the absolute amount of PSI fluorescence hardly changes. These results are in agreement with the recent proposal that the amount of LHC moving from PSII to PSI upon going from state 1 to state 2 is rather limited (Unlu et al. Proc Natl Acad Sci USA 111 (9):3460-3465, 2014). PMID:26518693

  16. Molecular toxicity of cerium oxide nanoparticles to the freshwater alga Chlamydomonas reinhardtii is associated with supra-environmental exposure concentrations

    PubMed Central

    Taylor, Nadine S.; Merrifield, Ruth; Williams, Tim D.; Chipman, J. Kevin; Lead, Jamie R.; Viant, Mark R.

    2016-01-01

    Abstract Ceria nanoparticles (NPs) are widely used as fuel catalysts and consequently are likely to enter the environment. Their potential impacts on. biota at environmentally relevant concentrations, including uptake and toxicity, remain to be elucidated and quantitative data on which to assess risk are sparse. Therefore, a definitive assessment of the molecular and phenotypic effects of ceria NPs was undertaken, using well-characterised mono-dispersed NPs as their toxicity is likely to be higher, enabling a conservative hazard assessment. Unbiased transcriptomics and metabolomics approaches were used to investigate the potential toxicity of tightly constrained 4–5 nm ceria NPs to the unicellular green alga, Chlamydomonas reinhardtii, a sentinel freshwater species. A wide range of exposure concentrations were investigated from predicted environmental levels, to support hazard assessment, to supra-environmental levels to provide insight into molecular toxicity pathways. Ceria NPs were internalised into intracellular vesicles within C. reinhardtii, yet caused no significant effect on algal growth at any exposure concentration. Molecular perturbations were only detected at supra-environmental ceria NP-concentrations, primarily down-regulation of photosynthesis and carbon fixation with associated effects on energy metabolism. For acute exposures to small mono-dispersed particles, it can be concluded there should be little concern regarding their dispersal into the environment for this trophic level. PMID:25740379

  17. Polymer coating of copper oxide nanoparticles increases nanoparticles uptake and toxicity in the green alga Chlamydomonas reinhardtii.

    PubMed

    Perreault, François; Oukarroum, Abdallah; Melegari, Silvia Pedroso; Matias, William Gerson; Popovic, Radovan

    2012-06-01

    Copper oxide nanoparticles (CuO NPs) are frequently used in a polymer-coated form, to be included in paints or fabrics for antimicrobial properties. Their application in antifouling paints may lead to the contamination of aquatic ecosystems. However, the toxicological risk of NPs in the environment is hard to evaluate due to a lack of knowledge on the mechanisms of NP interaction with biological systems. In this study, we investigated the effect of polymer coating on CuO NP toxicity in the green alga Chlamydomonas reinhardtii by comparing bare and polymer-coated CuO NPs prepared from the same CuO nanopowder. Both CuO NP suspensions were toxic to C. reinhardtii after 6 h treatment to concentrations of 0.005-0.04 g L(-1). Bare and polymer-coated CuO NPs induced a decrease of Photosystem II activity and the formation of reactive oxygen species. Polymer-coated CuO NP was found to be more toxic than the uncoated CuO NP. The higher toxicity of CS-CuO NP was mainly associated with the increased capacity of polymer-coated CuO NP to penetrate the cell compared to bare CuO NPs. These results indicates that the high toxicity of polymer-coated CuO NPs in algal cells results of intracellular interactions between NPs and the cellular system. PMID:22445953

  18. [Computational analysis of a cys-loop ligand gated ion channel from the green alga Chlamydomonas reinhardtii].

    PubMed

    Mukherjee, Ashutosh

    2015-01-01

    Plants possess several neurotransmitters with well-known physiological roles. Currently only receptors for glutamate were reported to be found in plants, while receptors for acetylcholine, serotonin and GABA have not yet been reported. In animals, these neurotransmitters act via one class of ligand binding ion channels called Cys-loop receptors which play a major role in fast synaptic transmission. They show the presence of two domains namely Neurotransmitter-gated ion-channel ligand-binding domain (Pfam: PF02931) and Neurotransmitter-gated transmembrane domain (Pfam: PF02932). Cys-loop receptors are also known in prokaryotes. No cys-loop receptor has been characterized from plants yet. In this study, the Ensembl plants database was searched for proteins with these two domains in the sequenced plant genomes, what resulted in only one protein (LIC1) from the alga Chlamydomonas reinhardtii. BLAST and profile HMM searches against the pdb structure database showed that this protein is related to animal and prokaryotic cys-loop receptors, although the cysteine residues characteristic of the cys-loop are absent. Physico-chemical and sequence analysis indicate that LIC1 is an anionic receptor. A model of this protein was generated using homology modeling based on a nicotinic acetylcholine receptor of Torpedo marmorata. The characteristic extracellular domain (ECD) and transmembrane domain (TMD) are well structured but the intercellular region is poorly formed. This is the first report on a detailed characterization of a cys-loop receptor from the plant kingdom. PMID:26510602

  19. Efficient expression of nuclear transgenes in the green alga Chlamydomonas: synthesis of an HIV antigen and development of a new selectable marker.

    PubMed

    Barahimipour, Rouhollah; Neupert, Juliane; Bock, Ralph

    2016-03-01

    The unicellular green alga Chlamydomonas reinhardtii has become an invaluable model system in plant biology. There is also considerable interest in developing this microalga into an efficient production platform for biofuels, pharmaceuticals, green chemicals and industrial enzymes. However, the production of foreign proteins in the nucleocytosolic compartment of Chlamydomonas is greatly hampered by the inefficiency of transgene expression from the nuclear genome. We have recently addressed this limitation by isolating mutant algal strains that permit high-level transgene expression and by determining the contributions of GC content and codon usage to gene expression efficiency. Here we have applied these new tools and explored the potential of Chlamydomonas to produce a recombinant biopharmaceutical, the HIV antigen P24. We show that a codon-optimized P24 gene variant introduced into our algal expression strains give rise to recombinant protein accumulation levels of up to 0.25% of the total cellular protein. Moreover, in combination with an expression strain, a resynthesized nptII gene becomes a highly efficient selectable marker gene that facilitates the selection of transgenic algal clones at high frequency. By establishing simple principles of successful transgene expression, our data open up new possibilities for biotechnological research in Chlamydomonas. PMID:26747175

  20. Comparison of the structural changes occurring during the primary phototransition of two different channelrhodopsins from Chlamydomonas algae.

    PubMed

    Ogren, John I; Yi, Adrian; Mamaev, Sergey; Li, Hai; Lugtenburg, Johan; DeGrip, Willem J; Spudich, John L; Rothschild, Kenneth J

    2015-01-20

    Channelrhodopsins (ChRs) from green flagellate algae function as light-gated ion channels when expressed heterologously in mammalian cells. Considerable interest has focused on understanding the molecular mechanisms of ChRs to bioengineer their properties for specific optogenetic applications such as elucidating the function of specific neurons in brain circuits. While most studies have used channelrhodopsin-2 from Chlamydomonas reinhardtii (CrChR2), in this work low-temperature Fourier transform infrared-difference spectroscopy is applied to study the conformational changes occurring during the primary phototransition of the red-shifted ChR1 from Chlamydomonas augustae (CaChR1). Substitution with isotope-labeled retinals or the retinal analogue A2, site-directed mutagenesis, hydrogen-deuterium exchange, and H2(18)O exchange were used to assign bands to the retinal chromophore, protein, and internal water molecules. The primary phototransition of CaChR1 at 80 K involves, in contrast to that of CrChR2, almost exclusively an all-trans to 13-cis isomerization of the retinal chromophore, as in the primary phototransition of bacteriorhodopsin (BR). In addition, significant differences are found for structural changes of the protein and internal water(s) compared to those of CrChR2, including the response of several Asp/Glu residues to retinal isomerization. A negative amide II band is identified in the retinal ethylenic stretch region of CaChR1, which reflects along with amide I bands alterations in protein backbone structure early in the photocycle. A decrease in the hydrogen bond strength of a weakly hydrogen bonded internal water is detected in both CaChR1 and CrChR2, but the bands are much broader in CrChR2, indicating a more heterogeneous environment. Mutations involving residues Glu169 and Asp299 (homologues of the Asp85 and Asp212 Schiff base counterions, respectively, in BR) lead to the conclusion that Asp299 is protonated during P1 formation and suggest that

  1. Characterization of the Major Light-Harvesting Complexes (LHCBM) of the Green Alga Chlamydomonas reinhardtii

    PubMed Central

    Natali, Alberto; Croce, Roberta

    2015-01-01

    Nine genes (LHCBM1-9) encode the major light-harvesting system of Chlamydomonas reinhardtii. Transcriptomic and proteomic analyses have shown that those genes are all expressed albeit in different amounts and some of them only in certain conditions. However, little is known about the properties and specific functions of the individual gene products because they have never been isolated. Here we have purified several complexes from native membranes and/or we have reconstituted them in vitro with pigments extracted from C. reinhardtii. It is shown that LHCBM1 and -M2/7 represent more than half of the LHCBM population in the membrane. LHCBM2/7 forms homotrimers while LHCBM1 seems to be present in heterotrimers. Trimers containing only type I LHCBM (M3/4/6/8/9) were also observed. Despite their different roles, all complexes have very similar properties in terms of pigment content, organization, stability, absorption, fluorescence and excited-state lifetimes. Thus the involvement of LHCBM1 in non-photochemical quenching is suggested to be due to specific interactions with other components of the membrane and not to the inherent quenching properties of the complex. Similarly, the overexpression of LHCBM9 during sulfur deprivation can be explained by its low sulfur content as compared with the other LHCBMs. Considering the highly conserved biochemical and spectroscopic properties, the major difference between the complexes may be in their capacity to interact with other components of the thylakoid membrane. PMID:25723534

  2. Towards elucidation of the toxic mechanism of copper on the model green alga Chlamydomonas reinhardtii.

    PubMed

    Jiang, Yongguang; Zhu, Yanli; Hu, Zhangli; Lei, Anping; Wang, Jiangxin

    2016-09-01

    Toxic effects of copper on aquatic organisms in polluted water bodies have garnered particular attention in recent years. Microalgae play an important role in aquatic ecosystems, and they are sensitive to heavy metal pollution. Thus, it is important to clarify the mechanism of copper toxicity first for ecotoxicology studies. In this study, the physiological, biochemical and gene expression characteristics of a model green microalga, Chlamydomonas reinhardtii, with 0, 50, 150 and 250 μM copper treatments were investigated. The response of C. reinhardtii to copper stress was significantly shown at a dose dependent manner. Inhibition of cell growth and variation of total chlorophyll content were observed with copper treatments. The maximum photochemical efficiency of PSII, actual photochemical efficiency of PSII and photochemical quenching value decreased in the 250 μM copper treatment with minimum values equal to 28, 24 and 60 % of the control values respectively. The content of lipid peroxidation biomarker malondialdehyde with copper treatments increased with a maximum value sevenfold higher than the control value. Inhibition of cell growth and photosynthesis was ascribed to peroxidation of membrane lipids. The glutathione content and activities of antioxidant enzymes, glutathione S-transferase, glutathione peroxidase, superoxide dismutase and peroxidase were induced by copper. Interestingly, the expression of antioxidant genes and the photosynthetic gene decreased in most copper treatments. In conclusion, oxidative stress caused by production of excess reactive oxidative species might be the major mechanism of copper toxicity on C. reinhardtii. PMID:27395008

  3. SPONTANEOUS MUTATION ACCUMULATION IN MULTIPLE STRAINS OF THE GREEN ALGA, CHLAMYDOMONAS REINHARDTII

    PubMed Central

    Morgan, Andrew D; Ness, Rob W; Keightley, Peter D; Colegrave, Nick

    2014-01-01

    Estimates of mutational parameters, such as the average fitness effect of a new mutation and the rate at which new genetic variation for fitness is created by mutation, are important for the understanding of many biological processes. However, the causes of interspecific variation in mutational parameters and the extent to which they vary within species remain largely unknown. We maintained multiple strains of the unicellular eukaryote Chlamydomonas reinhardtii, for approximately 1000 generations under relaxed selection by transferring a single cell every ∼10 generations. Mean fitness of the lines tended to decline with generations of mutation accumulation whereas mutational variance increased. We did not find any evidence for differences among strains in any of the mutational parameters estimated. The overall change in mean fitness per cell division and rate of input of mutational variance per cell division were more similar to values observed in multicellular organisms than to those in other single-celled microbes. However, after taking into account differences in genome size among species, estimates from multicellular organisms and microbes, including our new estimates from C. reinhardtii, become substantially more similar. Thus, we suggest that variation in genome size is an important determinant of interspecific variation in mutational parameters. PMID:24826801

  4. Cadmium exposure and phosphorus limitation increases metal content in the freshwater alga Chlamydomonas reinhardtii.

    PubMed

    Webster, Rachel E; Dean, Andrew P; Pittman, Jon K

    2011-09-01

    The characteristics of metal accumulation in freshwater microalgae are important to elucidate for a full understanding of metal cycling and toxicity in a freshwater system. This study has utilized an elemental profiling approach to investigate the impacts of Cd exposure and phosphorus (P) availability on metal accumulation after 7 days in batch culture-grown Chlamydomonas reinhardtii. Multivariate statistical analysis of the elemental data demonstrated distinct responses between both stresses. Sublethal concentrations of Cd (up to 15 μM) caused increased accumulation of Co. Cu, Fe, and Zn content also increased in response to enhanced Cd concentrations but only when P availability was low. While Cd exposure effected the accumulation of a few specific metals, P limitation increased the accumulation of all essential trace metals and macronutrients analyzed including Co, Fe, K, Na, and Zn but not Mn. The accumulation of Cd also markedly increased in response to P limitation. The impact of P availability on essential metal accumulation was the same when either inorganic P or an organic P source (glycerophosphate) was used. These results highlight the potential risks of metal toxicity for freshwater microalgae and aquatic food chains when P availability is limiting and which can be exacerbated by Cd pollution. PMID:21809879

  5. Ecophysiology, secondary pigments and ultrastructure of Chlainomonas sp. (Chlorophyta) from the European Alps compared with Chlamydomonas nivalis forming red snow.

    PubMed

    Remias, Daniel; Pichrtová, Martina; Pangratz, Marion; Lütz, Cornelius; Holzinger, Andreas

    2016-04-01

    Red snow is a well-known phenomenon caused by microalgae thriving in alpine and polar regions during the melting season. The ecology and biodiversity of these organisms, which are adapted to low temperatures, high irradiance and freeze-thaw events, are still poorly understood. We compared two different snow habitats containing two different green algal genera in the European Alps, namely algae blooming in seasonal rock-based snowfields (Chlamydomonas nivalis) and algae dominating waterlogged snow bedded over ice (Chlainomonassp.). Despite the morphological similarity of the red spores found at the snow surface, we found differences in intracellular organization investigated by light and transmission electron microscopy and in secondary pigments investigated by chromatographic analysis in combination with mass spectrometry. Spores ofChlainomonassp. show clear differences fromChlamydomonas nivalisin cell wall arrangement and plastid organization. Active photosynthesis at ambient temperatures indicates a high physiological activity, despite no cell division being present. Lipid bodies containing the carotenoid astaxanthin, which produces the red color, dominate cells of both species, but are modified differently. While inChlainomonassp. astaxanthin is mainly esterified with two fatty acids and is more apolar, inChamydomonas nivalis, in contrast, less apolar monoesters prevail. PMID:26884467

  6. Hyperspectral imaging of snow algae and green algae from aeroterrestrial habitats.

    PubMed

    Holzinger, Andreas; Allen, Michael C; Deheyn, Dimitri D

    2016-09-01

    Snow algae and green algae living in aeroterrestrial habitats are ideal objects to study adaptation to high light irradiation. Here, we used a detailed description of the spectral properties as a proxy for photo-acclimation/protection in snow algae (Chlamydomonas nivalis, Chlainomonas sp. and Chloromonas sp.) and charophyte green algae (Zygnema sp., Zygogonium ericetorum and Klebsormidium crenulatum). The hyperspectral microscopic mapping and imaging technique allowed us to acquire total absorption spectra of these microalgae in the waveband of 400-900nm. Particularly in Chlamydomonas nivalis and Chlainomonas sp., a high absorbance between 400-550nm was observed, due to naturally occurring secondary carotenoids; in Chloromonas sp. and in the charopyhte algae this high absorbance was missing, the latter being close relatives to land plants. To investigate if cellular water loss has an influence on the spectral properties, the cells were plasmolysed in sorbitol or desiccated at ambient air. While in snow algae, these treatments did hardly change the spectral properties, in the charopyhte algae the condensation of the cytoplasm and plastids increased the absorbance in the lower waveband of 400-500nm. These changes might be ecologically relevant and photoprotective, as aeroterrestrial algae are naturally exposed to occasional water limitation, leading to desiccation, which are conditions usually occurring together with higher irradiation. PMID:27442511

  7. Acclimation of Photosynthetic Light Reactions during Induction of Inorganic Carbon Accumulation in the Green Alga Chlamydomonas reinhardtii12

    PubMed Central

    Palmqvist, Kristin; Sundblad, Lars-Göran; Wingsle, Gunnar; Samuelsson, Göran

    1990-01-01

    Cells of the unicellular green algae Chlamydomonas reinhardtii were grown in high dissolved inorganic carbon (DIC) concentrations (supplied with 50 milliliters per liter CO2[g]) and transferred to low DIC concentrations (supplied with ≤ 100 microliters per liter CO2[g]). Immediately after transfer from high to low DIC the emission of photosystem II related chlorophyll a fluorescence was substantially quenched. It is hypothesized that the suddenly induced inorganic carbon limitation of photosynthesis resulted in a phosphorylation of LHCII, leading to the subsequent state 1 to state 2 transition. After 2 hours of low-DIC acclimation, 77 K fluorescence measurements revealed an increase in the fluorescence emitted from photosystem I, due to direct excitation, suggesting a change in photosystem II/photosystem I stoichiometry or an increased light harvesting capacity of photosystem I. After 5 to 6 hours of acclimation a considerable increase in spillover from photosystem II to photosystem I was observed. These adjustments of the photosynthetic light reactions reached steady-state after about 12 hours of low DIC treatment. The quencher of fluorescence could be removed by 5 minutes of dark treatment followed by 5 minutes of weak light treatment, of any of four different light qualities. It is hypothesized that this restoration of fluorescence was due to a state 2 to state 1 transition in low-DIC acclimated cells. A decreased ratio of violaxanthin to zeaxanthin was also observed in 12 hour low DIC treated cells, compared with high DIC grown cells. This ratio was not coupled to the level of fluorescence quenching. The role of different processes during the induction of a DIC accumulating mechanism is discussed. PMID:16667710

  8. Excitation dynamics and structural implication of the stress-related complex LHCSR3 from the green alga Chlamydomonas reinhardtii.

    PubMed

    Liguori, Nicoletta; Novoderezhkin, Vladimir; Roy, Laura M; van Grondelle, Rienk; Croce, Roberta

    2016-09-01

    LHCSR3 is a member of the Light-Harvesting Complexes (LHC) family, which is mainly composed of pigment-protein complexes responsible for collecting photons during the first steps of photosynthesis. Unlike related LHCs, LHCSR3 is expressed in stress conditions and has been shown to be essential for the fast component of photoprotection, non-photochemical quenching (NPQ), in the green alga Chlamydomonas reinhardtii. In plants, which do not possess LHCSR homologs, NPQ is triggered by the PSBS protein. Both PSBS and LHCSR3 possess the ability to sense pH changes but, unlike PSBS, LHCSR3 binds multiple pigments. In this work we have analyzed the properties of the pigments bound to LHCSR3 and their excited state dynamics. The data show efficient excitation energy transfer between pigments with rates similar to those observed for the other LHCs. Application of an exciton model based on a template of LHCII, the most abundant LHC, satisfactorily explains the collected steady state and time-resolved spectroscopic data, indicating that LHCSR3 has a LHC-like molecular architecture, although it probably binds less pigments. The model suggests that most of the chlorophylls have similar energy and interactions as in LHCII. The most striking difference is the localization of the lowest energy state, which is not on the Chlorophyll a (Chl a) 610-611-612 triplet as in all the LHCB antennas, but on Chl a613, which is located close to the lumen and to the pH-sensing region of the protein. PMID:27150505

  9. Quantitative analysis of the chemotaxis of a green alga, Chlamydomonas reinhardtii, to bicarbonate using diffusion-based microfluidic device.

    PubMed

    Choi, Hong Il; Kim, Jaoon Young Hwan; Kwak, Ho Seok; Sung, Young Joon; Sim, Sang Jun

    2016-01-01

    There is a growing interest in the photosynthetic carbon fixation by microalgae for the production of valuable products from carbon dioxide (CO2). Microalgae are capable of transporting bicarbonate (HCO3 (-)), the most abundant form of inorganic carbon species in the water, as a source of CO2 for photosynthesis. Despite the importance of HCO3 (-) as the carbon source, little is known about the chemotactic response of microalgae to HCO3 (-). Here, we showed the chemotaxis of a model alga, Chlamydomonas reinhardtii, towards HCO3 (-) using an agarose gel-based microfluidic device with a flow-free and stable chemical gradient during the entire assay period. The device was validated by analyzing the chemotactic responses of C. reinhardtii to the previously known chemoattractants (NH4Cl and CoCl2) and chemotactically neutral molecule (NaCl). We found that C. reinhardtii exhibited the strongest chemotactic response to bicarbonate at the concentration of 26 mM in a microfluidic device. The chemotactic response to bicarbonate showed a circadian rhythm with a peak during the dark period and a valley during the light period. We also observed the changes in the chemotaxis to bicarbonate by an inhibitor of bicarbonate transporters and a mutation in CIA5, a transcriptional regulator of carbon concentrating mechanism, indicating the relationship between chemotaxis to bicarbonate and inorganic carbon metabolism in C. reinhardtii. To the best of our knowledge, this is the first report of the chemotaxis of C. reinhardtii towards HCO3 (-), which contributes to the understanding of the physiological role of the chemotaxis to bicarbonate and its relevance to inorganic carbon utilization. PMID:26958101

  10. De novo transcriptomic analysis of hydrogen production in the green alga Chlamydomonas moewusii through RNA-Seq

    PubMed Central

    2013-01-01

    Background Microalgae can make a significant contribution towards meeting global renewable energy needs in both carbon-based and hydrogen (H2) biofuel. The development of energy-related products from algae could be accelerated with improvements in systems biology tools, and recent advances in sequencing technology provide a platform for enhanced transcriptomic analyses. However, these techniques are still heavily reliant upon available genomic sequence data. Chlamydomonas moewusii is a unicellular green alga capable of evolving molecular H2 under both dark and light anaerobic conditions, and has high hydrogenase activity that can be rapidly induced. However, to date, there is no systematic investigation of transcriptomic profiling during induction of H2 photoproduction in this organism. Results In this work, RNA-Seq was applied to investigate transcriptomic profiles during the dark anaerobic induction of H2 photoproduction. 156 million reads generated from 7 samples were then used for de novo assembly after data trimming. BlastX results against NCBI database and Blast2GO results were used to interpret the functions of the assembled 34,136 contigs, which were then used as the reference contigs for RNA-Seq analysis. Our results indicated that more contigs were differentially expressed during the period of early and higher H2 photoproduction, and fewer contigs were differentially expressed when H2-photoproduction rates decreased. In addition, C. moewusii and C. reinhardtii share core functional pathways, and transcripts for H2 photoproduction and anaerobic metabolite production were identified in both organisms. C. moewusii also possesses similar metabolic flexibility as C. reinhardtii, and the difference between C. moewusii and C. reinhardtii on hydrogenase expression and anaerobic fermentative pathways involved in redox balancing may explain their different profiles of hydrogenase activity and secreted anaerobic metabolites. Conclusions Herein, we have described a

  11. Different B-type methionine sulfoxide reductases in Chlamydomonas may protect the alga against high-light, sulfur-depletion, or oxidative stress.

    PubMed

    Zhao, Lei; Chen, Mei; Cheng, Dongmei; Yang, Haomeng; Sun, Yongle; Zhou, Heyi; Huang, Fang

    2013-11-01

    The genome of unicellular green alga Chlamydomonas reinhardtii contains four genes encoding B-type methionine sulfoxide reductases, MSRB1.1, MSRB1.2, MSRB2.1, and MSRB2.2, with functions largely unknown. To understand the cell defense system mediated by the methionine sulfoxide reductases in Chlamydomonas, we analyzed expression and physiological roles of the MSRBs under different abiotic stress conditions using immunoblotting and quantitative polymerase chain reaction (PCR) analyses. We showed that the MSRB2.2 protein was accumulated in cells treated with high light (1,300 µE/m² per s), whereas MSRB1.1 was accumulated in the cells under 1 mmol/L H₂O₂ treatment or sulfur depletion. We observed that the cells with the MSRB2.2 knockdown and overexpression displayed increased and decreased sensitivity to high light, respectively, based on in situ chlorophyll a fluorescence measures. We also observed that the cells with the MSRB1.1 knockdown and overexpression displayed decreased and increased tolerance to sulfur-depletion and oxidative stresses, respectively, based on growth and H₂-producing performance. The physiological implications revealed from the experimental data highlight the importance of MSRB2.2 and MSRB1.1 in protecting Chlamydomonas cells against adverse conditions such as high-light, sulfur-depletion, and oxidative stresses. PMID:24034412

  12. Optimization of culturing conditions for toxicity testing with the alga Oophila sp. (Chlorophyceae), an amphibian endosymbiont.

    PubMed

    Rodríguez-Gil, José Luis; Brain, Richard; Baxter, Leilan; Ruffell, Sarah; McConkey, Brendan; Solomon, Keith; Hanson, Mark

    2014-11-01

    Eggs of the yellow-spotted salamander (Ambystoma maculatum) have a symbiotic relationship with green algae. It has been suggested that contaminants that are preferentially toxic to algae, such as herbicides, may impair the symbiont and, hence, indirectly affect the development of the salamander embryo. To enable testing under near-standard conditions for first-tier toxicity screening, the authors isolated the alga from field-collected eggs and identified conditions providing exponential growth rates in the apparent asexual phase of the alga. This approach provided a uniform, single-species culture, facilitating assessment of common toxicity end points and comparison of sensitivity relative to other species. Sequencing of the 18s ribosomal DNA indicated that the isolated alga is closely related to the recently described Oophila amblystomatis but is more similar to other known Chlamydomonas species, suggesting possible biogeographical variability in the genetic identity of the algal symbiont. After a tiered approach to culturing method refinement, a modified Bristol's media with 1 mM NH4 (+) as nitrogen source was found to provide suitable conditions for toxicity testing at 18 °C and 200 µmol m(-2) s(-1) photosynthetically active radiation (PAR) on a 24-h light cycle. The validity of the approach was demonstrated with Zn(2+) as a reference toxicant. Overall, the present study shows that screening for direct effects of contaminants on the algal symbiont without the presence of the host salamander is possible under certain laboratory conditions. PMID:25113146

  13. Analysis of LhcSR3, a protein essential for feedback de-excitation in the green alga Chlamydomonas reinhardtii.

    PubMed

    Bonente, Giulia; Ballottari, Matteo; Truong, Thuy B; Morosinotto, Tomas; Ahn, Tae K; Fleming, Graham R; Niyogi, Krishna K; Bassi, Roberto

    2011-01-01

    In photosynthetic organisms, feedback dissipation of excess absorbed light energy balances harvesting of light with metabolic energy consumption. This mechanism prevents photodamage caused by reactive oxygen species produced by the reaction of chlorophyll (Chl) triplet states with O₂. Plants have been found to perform the heat dissipation in specific proteins, binding Chls and carotenoids (Cars), that belong to the Lhc family, while triggering of the process is performed by the PsbS subunit, needed for lumenal pH detection. PsbS is not found in algae, suggesting important differences in energy-dependent quenching (qE) machinery. Consistent with this suggestion, a different Lhc-like gene product, called LhcSR3 (formerly known as LI818) has been found to be essential for qE in Chlamydomonas reinhardtii. In this work, we report the production of two recombinant LhcSR isoforms from C. reinhardtii and their biochemical and spectroscopic characterization. We found the following: (i) LhcSR isoforms are Chl a/b- and xanthophyll-binding proteins, contrary to higher plant PsbS; (ii) the LhcSR3 isoform, accumulating in high light, is a strong quencher of Chl excited states, exhibiting a very fast fluorescence decay, with lifetimes below 100 ps, capable of dissipating excitation energy from neighbor antenna proteins; (iii) the LhcSR3 isoform is highly active in the transient formation of Car radical cation, a species proposed to act as a quencher in the heat dissipation process. Remarkably, the radical cation signal is detected at wavelengths corresponding to the Car lutein, rather than to zeaxanthin, implying that the latter, predominant in plants, is not essential; (iv) LhcSR3 is responsive to low pH, the trigger of non-photochemical quenching, since it binds the non-photochemical quenching inhibitor dicyclohexylcarbodiimide, and increases its energy dissipation properties upon acidification. This is the first report of an isolated Lhc protein constitutively active in

  14. Microbiota Influences Morphology and Reproduction of the Brown Alga Ectocarpus sp.

    PubMed

    Tapia, Javier E; González, Bernardo; Goulitquer, Sophie; Potin, Philippe; Correa, Juan A

    2016-01-01

    Associated microbiota play crucial roles in health and disease of higher organisms. For macroalgae, some associated bacteria exert beneficial effects on nutrition, morphogenesis and growth. However, current knowledge on macroalgae-microbiota interactions is mostly based on studies on green and red seaweeds. In this study, we report that when cultured under axenic conditions, the filamentous brown algal model Ectocarpus sp. loses its branched morphology and grows with a small ball-like appearance. Nine strains of periphytic bacteria isolated from Ectocarpus sp. unialgal cultures were identified by 16S rRNA sequencing, and assessed for their effect on morphology, reproduction and the metabolites secreted by axenic Ectocarpus sp. Six of these isolates restored morphology and reproduction features of axenic Ectocarpus sp. Bacteria-algae co-culture supernatants, but not the supernatant of the corresponding bacterium growing alone, also recovered morphology and reproduction of the alga. Furthermore, colonization of axenic Ectocarpus sp. with a single bacterial isolate impacted significantly the metabolites released by the alga. These results show that the branched typical morphology and the individuals produced by Ectocarpus sp. are strongly dependent on the presence of bacteria, while the bacterial effect on the algal exometabolome profile reflects the impact of bacteria on the whole physiology of this alga. PMID:26941722

  15. Microbiota Influences Morphology and Reproduction of the Brown Alga Ectocarpus sp.

    PubMed Central

    Tapia, Javier E.; González, Bernardo; Goulitquer, Sophie; Potin, Philippe; Correa, Juan A.

    2016-01-01

    Associated microbiota play crucial roles in health and disease of higher organisms. For macroalgae, some associated bacteria exert beneficial effects on nutrition, morphogenesis and growth. However, current knowledge on macroalgae–microbiota interactions is mostly based on studies on green and red seaweeds. In this study, we report that when cultured under axenic conditions, the filamentous brown algal model Ectocarpus sp. loses its branched morphology and grows with a small ball-like appearance. Nine strains of periphytic bacteria isolated from Ectocarpus sp. unialgal cultures were identified by 16S rRNA sequencing, and assessed for their effect on morphology, reproduction and the metabolites secreted by axenic Ectocarpus sp. Six of these isolates restored morphology and reproduction features of axenic Ectocarpus sp. Bacteria-algae co-culture supernatants, but not the supernatant of the corresponding bacterium growing alone, also recovered morphology and reproduction of the alga. Furthermore, colonization of axenic Ectocarpus sp. with a single bacterial isolate impacted significantly the metabolites released by the alga. These results show that the branched typical morphology and the individuals produced by Ectocarpus sp. are strongly dependent on the presence of bacteria, while the bacterial effect on the algal exometabolome profile reflects the impact of bacteria on the whole physiology of this alga. PMID:26941722

  16. A High-Throughput Fatty Acid Profiling Screen Reveals Novel Variations in Fatty Acid Biosynthesis in Chlamydomonas reinhardtii and Related Algae

    PubMed Central

    Pflaster, Erin L.; Schwabe, Michael J.; Becker, Joyanne; Wilkinson, Melissa S.; Parmer, Ashley; Clemente, Thomas E.; Cahoon, Edgar B.

    2014-01-01

    Analysis of fatty acid methyl esters (FAMEs) by gas chromatography (GC) is a common technique for the quantitative and qualitative analysis of acyl lipids. Methods for FAME preparation are typically time-consuming and labor-intensive and require multiple transfers of reagents and products between reaction tubes and autosampler vials. In order to increase throughput and lower the time and materials costs required for FAME preparation prior to GC analysis, we have developed a method in which 10-to-20-mg samples of microbial biomass are transferred to standard GC autosampler vials, transesterified using an emulsion of methanolic trimethylsulfonium hydroxide and hexane, and analyzed directly by GC without further sample handling. This method gives results that are essentially identical to those obtained by the more labor- and material-intensive FAME preparation methods, such as transmethylation with methanolic HCl. We applied this method to the screening of laboratory and environmental isolates of the green alga Chlamydomonas for variations in fatty acid composition. This screening method facilitated two novel discoveries. First, we identified a common laboratory strain of C. reinhardtii, CC-620, completely lacking all ω-3 fatty acids normally found in this organism and showed that this strain contains an inactivating mutation in the CrFAD7 gene, encoding the sole ω-3 desaturase activity in this organism. Second, we showed that some species of Chlamydomonas make Δ6-unsaturated polyunsaturated fatty acids (PUFA) rather than the Δ5 species normally made by the previously characterized laboratory strains of Chlamydomonas, suggesting that there is species-specific variation in the regiospecificity and substrate selectivity of front-end desaturases in this algal genus. PMID:25239975

  17. Rapid Aggregation of Biofuel-Producing Algae by the Bacterium Bacillus sp. Strain RP1137

    PubMed Central

    Powell, Ryan J.

    2013-01-01

    Algal biofuels represent one of the most promising means of sustainably replacing liquid fuels. However, significant challenges remain before alga-based fuels become competitive with fossil fuels. One of the largest challenges is the ability to harvest the algae in an economical and low-energy manner. In this article, we describe the isolation of a bacterial strain, Bacillus sp. strain RP1137, which can rapidly aggregate several algae that are candidates for biofuel production, including a Nannochloropsis sp. This bacterium aggregates algae in a pH-dependent and reversible manner and retains its aggregation ability after paraformaldehyde fixation, opening the possibility for reuse of the cells. The optimal ratio of bacteria to algae is described, as is the robustness of aggregation at different salinities and temperatures. Aggregation is dependent on the presence of calcium or magnesium ions. The efficiency of aggregation of Nannochloropsis oceanica IMET1 is between 70 and 95% and is comparable to that obtained by other means of harvest; however, the rate of harvest is fast, with aggregates forming in 30 s. PMID:23892750

  18. Whole-Genome Resequencing Reveals Extensive Natural Variation in the Model Green Alga Chlamydomonas reinhardtii[OPEN

    PubMed Central

    Hazzouri, Khaled M.; Rosas, Ulises; Bahmani, Tayebeh; Nelson, David R.; Abdrabu, Rasha; Harris, Elizabeth H.; Salehi-Ashtiani, Kourosh; Purugganan, Michael D.

    2015-01-01

    We performed whole-genome resequencing of 12 field isolates and eight commonly studied laboratory strains of the model organism Chlamydomonas reinhardtii to characterize genomic diversity and provide a resource for studies of natural variation. Our data support previous observations that Chlamydomonas is among the most diverse eukaryotic species. Nucleotide diversity is ∼3% and is geographically structured in North America with some evidence of admixture among sampling locales. Examination of predicted loss-of-function mutations in field isolates indicates conservation of genes associated with core cellular functions, while genes in large gene families and poorly characterized genes show a greater incidence of major effect mutations. De novo assembly of unmapped reads recovered genes in the field isolates that are absent from the CC-503 assembly. The laboratory reference strains show a genomic pattern of polymorphism consistent with their origin as the recombinant progeny of a diploid zygospore. Large duplications or amplifications are a prominent feature of laboratory strains and appear to have originated under laboratory culture. Extensive natural variation offers a new source of genetic diversity for studies of Chlamydomonas, including naturally occurring alleles that may prove useful in studies of gene function and the dissection of quantitative genetic traits. PMID:26392080

  19. Global Metabolic Regulation of the Snow Alga Chlamydomonas nivalis in Response to Nitrate or Phosphate Deprivation by a Metabolome Profile Analysis

    PubMed Central

    Lu, Na; Chen, Jun-Hui; Wei, Dong; Chen, Feng; Chen, Gu

    2016-01-01

    In the present work, Chlamydomonas nivalis, a model species of snow algae, was used to illustrate the metabolic regulation mechanism of microalgae under nutrient deprivation stress. The seed culture was inoculated into the medium without nitrate or phosphate to reveal the cell responses by a metabolome profile analysis using gas chromatography time-of-flight mass spectrometry (GC/TOF-MS). One hundred and seventy-one of the identified metabolites clustered into five groups by the orthogonal partial least squares discriminant analysis (OPLS-DA) model. Among them, thirty of the metabolites in the nitrate-deprived group and thirty-nine of the metabolites in the phosphate-deprived group were selected and identified as “responding biomarkers” by this metabolomic approach. A significant change in the abundance of biomarkers indicated that the enhanced biosynthesis of carbohydrates and fatty acids coupled with the decreased biosynthesis of amino acids, N-compounds and organic acids in all the stress groups. The up- or down-regulation of these biomarkers in the metabolic network provides new insights into the global metabolic regulation and internal relationships within amino acid and fatty acid synthesis, glycolysis, the tricarboxylic acid cycle (TCA) and the Calvin cycle in the snow alga under nitrate or phosphate deprivation stress. PMID:27171077

  20. Algae Sense Exact Temperatures: Small Heat Shock Proteins Are Expressed at the Survival Threshold Temperature in Cyanidioschyzon merolae and Chlamydomonas reinhardtii

    PubMed Central

    Kobayashi, Yusuke; Harada, Naomi; Nishimura, Yoshiki; Saito, Takafumi; Nakamura, Mami; Fujiwara, Takayuki; Kuroiwa, Tsuneyoshi; Misumi, Osami

    2014-01-01

    The primitive red alga Cyanidioschyzon merolae inhabits acidic hot springs and shows robust resistance to heat shock treatments up to 63 °C. Microarray analysis was performed to identify the key genes underlying the high temperature tolerance of this organism. Among the upregulated genes that were identified, we focused on two small heat shock proteins (sHSPs) that belong to a unique class of HSP families. These two genes are located side by side in an inverted repeat orientation on the same chromosome and share a promoter. These two genes were simultaneously and rapidly upregulated in response to heat shock treatment (>1,000-fold more than the control). Interestingly, upregulation appeared to be triggered not by a difference in temperatures, but rather by the absolute temperature. Similar sHSP structural genes have been reported in the green alga Chlamydomonas reinhardtii, but the threshold temperature for the expression of these sHSP-encoding genes in Ch. reinhardtii was different from the threshold temperature for the expression of the sHSP genes from Cy. merolae. These results indicate the possible importance of an absolute temperature sensing system in the evolution and tolerance of high-temperature conditions among unicellular microalgae. PMID:25267447

  1. Global Metabolic Regulation of the Snow Alga Chlamydomonas nivalis in Response to Nitrate or Phosphate Deprivation by a Metabolome Profile Analysis.

    PubMed

    Lu, Na; Chen, Jun-Hui; Wei, Dong; Chen, Feng; Chen, Gu

    2016-01-01

    In the present work, Chlamydomonas nivalis, a model species of snow algae, was used to illustrate the metabolic regulation mechanism of microalgae under nutrient deprivation stress. The seed culture was inoculated into the medium without nitrate or phosphate to reveal the cell responses by a metabolome profile analysis using gas chromatography time-of-flight mass spectrometry (GC/TOF-MS). One hundred and seventy-one of the identified metabolites clustered into five groups by the orthogonal partial least squares discriminant analysis (OPLS-DA) model. Among them, thirty of the metabolites in the nitrate-deprived group and thirty-nine of the metabolites in the phosphate-deprived group were selected and identified as "responding biomarkers" by this metabolomic approach. A significant change in the abundance of biomarkers indicated that the enhanced biosynthesis of carbohydrates and fatty acids coupled with the decreased biosynthesis of amino acids, N-compounds and organic acids in all the stress groups. The up- or down-regulation of these biomarkers in the metabolic network provides new insights into the global metabolic regulation and internal relationships within amino acid and fatty acid synthesis, glycolysis, the tricarboxylic acid cycle (TCA) and the Calvin cycle in the snow alga under nitrate or phosphate deprivation stress. PMID:27171077

  2. Oil accumulation in the model green alga Chlamydomonas reinhardtii: characterization, variability between common laboratory strains and relationship with starch reserves

    PubMed Central

    2011-01-01

    Background When cultivated under stress conditions, many microalgae species accumulate both starch and oil (triacylglycerols). The model green microalga Chlamydomonas reinhardtii has recently emerged as a model to test genetic engineering or cultivation strategies aiming at increasing lipid yields for biodiesel production. Blocking starch synthesis has been suggested as a way to boost oil accumulation. Here, we characterize the triacylglycerol (TAG) accumulation process in Chlamydomonas and quantify TAGs in various wild-type and starchless strains. Results In response to nitrogen deficiency, Chlamydomonas reinhardtii produced TAGs enriched in palmitic, oleic and linoleic acids that accumulated in oil-bodies. Oil synthesis was maximal between 2 and 3 days following nitrogen depletion and reached a plateau around day 5. In the first 48 hours of oil deposition, a ~80% reduction in the major plastidial membrane lipids occurred. Upon nitrogen re-supply, mobilization of TAGs started after starch degradation but was completed within 24 hours. Comparison of oil content in five common laboratory strains (CC124, CC125, cw15, CC1690 and 11-32A) revealed a high variability, from 2 μg TAG per million cell in CC124 to 11 μg in 11-32A. Quantification of TAGs on a cell basis in three mutants affected in starch synthesis (cw15sta1-2, cw15sta6 and cw15sta7-1) showed that blocking starch synthesis did not result in TAG over-accumulation compared to their direct progenitor, the arginine auxotroph strain 330. Moreover, no significant correlation was found between cellular oil and starch levels among the twenty wild-type, mutants and complemented strains tested. By contrast, cellular oil content was found to increase steeply with salt concentration in the growth medium. At 100 mM NaCl, oil level similar to nitrogen depletion conditions could be reached in CC124 strain. Conclusion A reference basis for future genetic studies of oil metabolism in Chlamydomonas is provided. Results

  3. High-efficiency homologous recombination in the oil-producing alga Nannochloropsis sp.

    PubMed

    Kilian, Oliver; Benemann, Christina S E; Niyogi, Krishna K; Vick, Bertrand

    2011-12-27

    Algae have reemerged as potential next-generation feedstocks for biofuels, but strain improvement and progress in algal biology research have been limited by the lack of advanced molecular tools for most eukaryotic microalgae. Here we describe the development of an efficient transformation method for Nannochloropsis sp., a fast-growing, unicellular alga capable of accumulating large amounts of oil. Moreover, we provide additional evidence that Nannochloropsis is haploid, and we demonstrate that insertion of transformation constructs into the nuclear genome can occur by high-efficiency homologous recombination. As examples, we generated knockouts of the genes encoding nitrate reductase and nitrite reductase, resulting in strains that were unable to grow on nitrate and nitrate/nitrite, respectively. The application of homologous recombination in this industrially relevant alga has the potential to rapidly advance algal functional genomics and biotechnology. PMID:22123974

  4. High-efficiency homologous recombination in the oil-producing alga Nannochloropsis sp.

    PubMed Central

    Kilian, Oliver; Benemann, Christina S. E.; Niyogi, Krishna K.; Vick, Bertrand

    2011-01-01

    Algae have reemerged as potential next-generation feedstocks for biofuels, but strain improvement and progress in algal biology research have been limited by the lack of advanced molecular tools for most eukaryotic microalgae. Here we describe the development of an efficient transformation method for Nannochloropsis sp., a fast-growing, unicellular alga capable of accumulating large amounts of oil. Moreover, we provide additional evidence that Nannochloropsis is haploid, and we demonstrate that insertion of transformation constructs into the nuclear genome can occur by high-efficiency homologous recombination. As examples, we generated knockouts of the genes encoding nitrate reductase and nitrite reductase, resulting in strains that were unable to grow on nitrate and nitrate/nitrite, respectively. The application of homologous recombination in this industrially relevant alga has the potential to rapidly advance algal functional genomics and biotechnology. PMID:22123974

  5. Temperature regulates fatty acid desaturases at a transcriptional level and modulates the fatty acid profile in the Antarctic microalga Chlamydomonas sp. ICE-L.

    PubMed

    An, Meiling; Mou, Shanli; Zhang, Xiaowen; Ye, Naihao; Zheng, Zhou; Cao, Shaona; Xu, Dong; Fan, Xiao; Wang, Yitao; Miao, Jinlai

    2013-04-01

    Chlamydomonas sp. ICE-L which can thrive in extreme environments of the Antarctic is a major biomass producer. The FAD genes in Chlamydomonas sp. ICE-L were obtained and sequence alignment showed that these genes are homologous to known FADs with conserved histidine motifs. In this study, we analyzed the transcription of five FADs and FA compositions at different temperatures. The results showed that the expressions of Δ9CiFAD, ω3CiFAD1 and ω3CiFAD2 were apparently up-regulated at 0°C, however, the up-regulation of Δ6CiFAD intensified with rising temperature. Meanwhile, analysis of the FA compositions showed that PUFAs were dominant compositions, accounting for more than 75% TFA in Chlamydomonas sp. ICE-L. Furthermore, PUFAs were significantly increased at 0 and 5°C, which may be attributed to higher proportions of C18:3 and C20:3. Moreover, PUFAs were significantly decreased at 15°C whereas SFAs were significantly increased. PMID:23500572

  6. Evaluation of the Marine Algae Gracilaria salicornia and Sargassum sp. For the Biosorption of Cr (VI) from Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Shams Khorramabadi, Gh.; Darvishi Cheshmeh Soltani, R.

    In this study, the adsorption properties of two different marine algae (Gracilaria salicornia (red algae) and Sargassum sp. (brown algae) were investigated. Equilibrium isotherms were studied to evaluate the relative ability of the two algae to sequester Cr (VI) from aqueous solutions. The maximum biosorption capacity obtained was 45.959 mg g-1 for G. salicornia and 33.258 mg g-1 for Sargassum sp. at a solution pH of 4 and 50 mg L-1 initial chromium concentration. A significant fraction of the total Cr (VI) uptake was achieved within 60 min. Biosorbed chromium ions concentrations increased with increasing concentrations of biosorbents and increasing pH. The biosorption of Cr (VI) on G. salicornia and Sargassum sp. could best be described by the Langmuir model (R2>0.997 for Sargassum sp. and R2>0.999 for G. salicornia).

  7. Removal of trimethoprim, sulfamethoxazole, and triclosan by the green alga Nannochloris sp.

    PubMed

    Bai, Xuelian; Acharya, Kumud

    2016-09-01

    Trimethoprim (TMP), sulfamethoxazole (SMX), and triclosan (TCS) are widely used and continuously released into aquatic environments. Freshwater algae can be responsible for the uptake and transfer of the contaminants because they are a major food source for most aquatic organisms. This research applied incubation studies to evaluate the removal efficiency of TMP, SMX, and TCS by the green alga Nannochloris sp. The results showed that the hydrophilic antibiotics TMP and SMX remained in the algal culture at 100% and 68%, respectively, after 14days of incubation, and therefore were not significantly removed from the medium. However, the lipophilic antimicrobial TCS was significantly removed from the medium. Immediately after incubation began, 74% of TCS dissipated and 100% of TCS was removed after 7days of incubation. Additionally, over 42% of TCS was found associated with the algal cells throughout the incubation. The results demonstrate that the presence of Nannochloris sp. eliminated TCS in the aquatic system, but could not significantly remove the antibiotics TMP and SMX. The removal mechanisms of SMX and TCS were found to be different in the algal culture. Algae-promoted photolysis was the primary process for removing SMX and algae-mediated uptake played a major role in removing TCS. PMID:27179202

  8. Pyropia plicata sp. nov. (Bangiales, Rhodophyta): naming a common intertidal alga from New Zealand

    PubMed Central

    Nelson, Wendy A.

    2013-01-01

    Abstract A commonly found red alga of the upper intertidal zone of New Zealand rocky coasts is described for the first time as Pyropia plicata sp. nov. This species has been incorrectly known as Porphyra columbina Mont. (now Pyropia columbina (Mont.) W.A.Nelson) for many years. Pyropia plicata is widespread and common, and it is readily distinguished from other species of bladed Bangiales in New Zealand by its distinctive morphology, with pleated blades attached by a central rhizoidal holdfast. PMID:23794933

  9. Dehydroascorbate: a possible surveillance molecule of oxidative stress and programmed cell death in the green alga Chlamydomonas reinhardtii.

    PubMed

    Murik, Omer; Elboher, Ahinoam; Kaplan, Aaron

    2014-04-01

    Chlamydomonas reinhardtii tolerates relatively high H2 O2 levels that induce an array of antioxidant activities. However, rather than rendering the cells more resistant to oxidative stress, the cells become far more sensitive to an additional H2 O2 dose. If H2 O2 is provided 1.5-9 h after an initial dose, it induces programmed cell death (PCD) in the wild-type, but not in the dum1 mutant impaired in the mitochondrial respiratory complex III. This mutant does not exhibit a secondary oxidative burst 4-5 h after the inducing H2 O2 , nor does it activate metacaspase-1 after the second H2 O2 treatment. The intracellular dehydroascorbate level, a product of ascorbate peroxidase, increases under conditions leading to PCD. The addition of dehydroascorbate induces PCD in the wild-type and dum1 cultures, but higher levels are required in dum1 cells, where it is metabolized faster. The application of dehydroascorbate induces the expression of metacaspase-2, which is much stronger than the expression of metacaspase-1. The presence or absence of oxidative stress, in addition to the rise in internal dehydroascorbate, may determine which metacaspase is activated during Chlamydomonas PCD. Cell death is strongly affected by the timing of H2 O2 or dehydroascorbate admission to synchronously grown cultures, suggesting that the cell cycle phase may distinguish cells that perish from those that do not. PMID:24345283

  10. Photochemical Performance of the Acidophilic Red Alga Cyanidium sp. in a pH Gradient

    NASA Astrophysics Data System (ADS)

    Kvíderová, Jana

    2012-06-01

    The acidophilic red alga Cyanidium sp. is one of the dominant mat-forming species in the highly acidic waters of Río Tinto, Spain. The culture of Cyanidium sp., isolated from a microbial mat sample collected at Río Tinto, was exposed to 9 different pH conditions in a gradient from 0.5 to 5 for 24 h and its physiological status evaluated by variable chlorophyll a fluorescence kinetics measurements. Maximum quantum yield was determined after 30 min, 1 h, 2 h, 4 h, 6 h and 24 h of exposure after 15 min dark adaptation. The effect of pH on photochemical activity of Cyanidium sp. was observable as early as 30 min after exposure and the pattern remained stable or with only minor modifications for 24 h. The optimum pH ranged from 1.5 to 2.5. A steep decrease of the photochemical activity was observed at pH below 1 even after 30 min of exposure. Although the alga had tolerated the exposure to pH = 1 for at least 6 h, longer (24 h) exposure resulted in reduction of the photochemical activity. At pH above 2.5, the decline was more moderate and its negative effect on photochemistry was less severe. According to the fluorescence measurements, the red alga Cyanidium sp. is well-adapted to prevailing pH at its original locality at Río Tinto, i.e. pH of 1 to 3. The short-term survival in pH < 1.5 may be adaptation to rare exposures to such low pH in the field. The tolerance of pH above 3 could be caused by adaptation to the microenvironment of the inner parts of microbial mats in which Cyanidium sp. usually dominates and where higher pH could occur due to photosynthetic oxygen production.

  11. Toxicity of silver to two freshwater algae, Chlamydomonas reinhardtii and Pseudokirchneriella sub-capitata, grown under continuous culture conditions: influence of thiosulphate.

    PubMed

    Hiriart-Baer, Véronique P; Fortin, Claude; Lee, Dae-Young; Campbell, Peter G C

    2006-06-15

    In a test of the biotic ligand model (BLM), the uptake and toxicity of silver, in the absence or presence of the inorganic ligand, thiosulphate, were assessed for two freshwater green algae, Chlamydomonas reinhardtii and Pseudokirchneriella sub-capitata, using turbidostat continuous cultures. In the initial experiments, run in the absence of thiosulphate, the influent Ag concentration was varied from 0 to 75 nM in steps; for each influent concentration, silver uptake was calculated and the algal growth rate was determined. Silver uptake rates at low Ag concentrations were similar for both algae (e.g., 14-19 nmolm(-2)h(-1), for influent Ag(+) concentrations of approximately 9 nM) but at higher exposures uptake by P. sub-capitata exceeded that of C. reinhardtii. Despite this higher uptake rate, in the absence of thiosulphate P. sub-capitata was not more sensitive to free silver; 50% growth inhibition was reached at influent free Ag(+) concentrations of 15+/-7 and 22+/-13 nM for C. reinhardtii and P. sub-capitata, respectively. In the second series of experiments, the free Ag(+) concentration was held constant ( approximately 9 nM in the influent; 2-3 nM in the effluent) while the concentration of the silver thiosulphate complex, AgS(2)O(3)(-), was increased from 9 to 90 nM in steps. Under such conditions, the BLM would predict that silver uptake and toxicity should remain constant. On the contrary, both silver uptake and silver toxicity increased, indicating that the anionic silver thiosulphate complex enters the algal cells via a membrane-bound sulphate transporter and contributes to uptake and toxicity. However, for both algae there were indications that silver assimilated in this manner was somewhat less toxic to the algal cell than silver that entered via cation transport only. Physiological indicators of stress revealed possible different intracellular targets for these two freshwater algae, proteins and enzymes for C. reinhardtii and the photosynthetic

  12. Optimizing biodiesel production in marine Chlamydomonas sp. JSC4 through metabolic profiling and an innovative salinity-gradient strategy

    PubMed Central

    2014-01-01

    Background Biodiesel production from marine microalgae has received much attention as microalgae can be cultivated on non-arable land without the use of potable water, and with the additional benefits of mitigating CO2 emissions and yielding biomass. However, there is still a lack of effective operational strategies to promote lipid accumulation in marine microalgae, which are suitable for making biodiesel since they are mainly composed of saturated and monounsaturated fatty acids. Moreover, the regulatory mechanisms involved in lipid biosynthesis in microalgae under environmental stress are not well understood. Results In this work, the combined effects of salinity and nitrogen depletion stresses on lipid accumulation of a newly isolated marine microalga, Chlamydomonas sp. JSC4, were explored. Metabolic intermediates were profiled over time to observe transient changes during the lipid accumulation triggered by the combination of the two stresses. An innovative cultivation strategy (denoted salinity-gradient operation) was also employed to markedly improve the lipid accumulation and lipid quality of the microalga, which attained an optimal lipid productivity of 223.2 mg L-1 d-1 and a lipid content of 59.4% per dry cell weight. This performance is significantly higher than reported in most related studies. Conclusions This work demonstrated the synergistic integration of biological and engineering technologies to develop a simple and effective strategy for the enhancement of oil production in marine microalgae. PMID:25002905

  13. Apparent lack of an O/sup 6/-methylguanine repair mechanism in the unicellular alga, Chlamydomonas ReinhardtII

    SciTech Connect

    Frost, B.; Small, G.D.

    1986-05-01

    O/sup 6/-Methylguanine (O/sup 6/meG) is the presumed major mutagenic lesion formed by the treatment of DNA with methylating agents such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The repair of this lesion has been shown to involve a protein which selectively removes the O/sup 6/-methyl group by transferring the group to one of the protein's cysteinyl residues. Several prokaryotic and eukaryotic organisms have this O/sup 6/-meG transferase (O/sup 6/MGT) activity, while other (e.g., yeast) lack any apparent O/sup 6/MGT. In some organisms, the O/sup 6/MGT is inducible in response to sublethal doses of methylating agent. The authors have examined Chlamydomonas for such a repair system. This is the first report of a search for O/sup 6/meG repair in a plant system. O/sup 6/meG repair was examined on three levels: in vivo removal of O/sup 6/meG, inducible repair of O/sup 6/meG, the presence of O/sup 6/MGT activity in cellular extracts. They observed no obvious removal of O/sup 6/meG from cellular DNA at various times (up to 30 hours) after treatment of cells with MNNG. The authors were unable to detect any inducible repair of O/sup 6/meG upon pretreatment of cells with sublethal doses of MNNG. Finally, they observed no apparent O/sup 6/MGT activity in cell-free extracts prepared two different ways following the protocols used in E. coli and in rat liver. These results suggest Chlamydomonas apparently lacks a repair mechanism for O/sup 6/meG.

  14. Metabolic and photosynthetic consequences of blocking starch biosynthesis in the green alga Chlamydomonas reinhardtii sta6 mutant.

    PubMed

    Krishnan, Anagha; Kumaraswamy, G Kenchappa; Vinyard, David J; Gu, Huiya; Ananyev, Gennady; Posewitz, Matthew C; Dismukes, G Charles

    2015-03-01

    Upon nutrient deprivation, microalgae partition photosynthate into starch and lipids at the expense of protein synthesis and growth. We investigated the role of starch biosynthesis with respect to photosynthetic growth and carbon partitioning in the Chlamydomonas reinhardtii starchless mutant, sta6, which lacks ADP-glucose pyrophosphorylase. This mutant is unable to convert glucose-1-phosphate to ADP-glucose, the precursor of starch biosynthesis. During nutrient-replete culturing, sta6 does not re-direct metabolism to make more proteins or lipids, and accumulates 20% less biomass. The underlying molecular basis for the decreased biomass phenotype was identified using LC-MS metabolomics studies and flux methods. Above a threshold light intensity, photosynthetic electron transport rates (water → CO2) decrease in sta6 due to attenuated rates of NADPH re-oxidation, without affecting photosystems I or II (no change in isolated photosynthetic electron transport). We observed large accumulations of carbon metabolites that are precursors for the biosynthesis of lipids, amino acids and sugars/starch, indicating system-wide consequences of slower NADPH re-oxidation. Attenuated carbon fixation resulted in imbalances in both redox and adenylate energy. The pool sizes of both pyridine and adenylate nucleotides in sta6 increased substantially to compensate for the slower rate of turnover. Mitochondrial respiration partially relieved the reductant stress; however, prolonged high-light exposure caused accelerated photoinhibition. Thus, starch biosynthesis in Chlamydomonas plays a critical role as a principal carbon sink influencing cellular energy balance however, disrupting starch biosynthesis does not redirect resources to other bioproducts (lipids or proteins) during nutrient-replete culturing, resulting in cells that are susceptible to photochemical damage caused by redox stress. PMID:25645872

  15. Negative Impact on Growth and Photosynthesis in the Green Alga Chlamydomonas reinhardtii in the Presence of the Estrogen 17α-Ethynylestradiol

    PubMed Central

    Pocock, Tessa; Falk, Stefan

    2014-01-01

    It is well known that estrogenic compounds affect development of fertilized eggs of many species of birds, fish and amphibians through disrupted activity of carbonic anhydrase (CA). The most potent activity comes from the most commonly occurring synthetic sterol, 17α-Ethynylestradiol (EE2). Less is known about the responses of aquatic phytoplankton to these compounds. Here we show for the first time that, in comparision to the control, the addition of 7 µM EE2 reduced the growth rate of the green alga Chlamydomonas reinhardtii by 68% for cells grown at high CO2. When cells were grown in ambient air (low Ci) with a fully activated carbon concentrating mechanism through the induction of CA activity, the growth rates were reduced by as much as 119%. A reduced growth rate could be observed at EE2 concentrations as low as 10 pM. This was accompanied by a reduced maximum capacity for electron transport in photosystem II as determined by a lower FV/FM for low Ci-grown cells, which indicates the involvement of CAH3, a CA specifically located in the thylakoid lumen involved in proton pumping across the thylakoid membranes. These results were in agreement with an observed reduction in the chloroplastic affinity for Ci as shown by a strong increase in the Michaelis-Menten K0.5 for HCO3−. In itself, a lowering of the growth rate of a green alga by addition of the sterol EE2 warrants further investigation into the potential environmental impact by the release of treated waste water. PMID:25310092

  16. Effect of chromium oxide (III) nanoparticles on the production of reactive oxygen species and photosystem II activity in the green alga Chlamydomonas reinhardtii.

    PubMed

    Costa, Cristina Henning da; Perreault, François; Oukarroum, Abdallah; Melegari, Sílvia Pedroso; Popovic, Radovan; Matias, William Gerson

    2016-09-15

    With the growth of nanotechnology and widespread use of nanomaterials, there is an increasing risk of environmental contamination by nanomaterials. However, the potential implications of such environmental contamination are hard to evaluate since the toxicity of nanomaterials if often not well characterized. The objective of this study was to evaluate the toxicity of a chromium-based nanoparticle, Cr2O3-NP, used in a wide diversity of industrial processes and commercial products, on the unicellular green alga Chlamydomonas reinhardtii. The deleterious impacts of Cr2O3-NP were characterized using cell density measurements, production of reactive oxygen species (ROS), esterase enzymes activity, and photosystem II electron transport as indicators of toxicity. Cr2O3-NP exposure inhibited culture growth and significantly lowered cellular Chlorophyll a content. From cell density measurements, EC50 values of 2.05±0.20 and 1.35±0.06gL(-1) Cr2O3-NP were obtained after 24 and 72h of exposure, respectively. In addition, ROS levels were increased to 160.24±2.47% and 59.91±0.15% of the control value after 24 and 72h of exposition to 10gL(-1) Cr2O3-NP. At 24h of exposure, the esterase activity increased to 160.24% of control value, revealing a modification of the short-term metabolic response of algae to Cr2O3-NP exposure. In conclusion, the metabolism of C. reinhardtii was the most sensitive to Cr2O3-NP after 24h of treatment. PMID:26803219

  17. The slow S to M rise of chlorophyll a fluorescence reflects transition from state 2 to state 1 in the green alga Chlamydomonas reinhardtii.

    PubMed

    Kodru, Sireesha; Malavath, Tirupathi; Devadasu, Elsinraju; Nellaepalli, Sreedhar; Stirbet, Alexandrina; Subramanyam, Rajagopal; Govindjee

    2015-08-01

    The green alga Chlamydomonas (C.) reinhardtii is a model organism for photosynthesis research. State transitions regulate redistribution of excitation energy between photosystem I (PS I) and photosystem II (PS II) to provide balanced photosynthesis. Chlorophyll (Chl) a fluorescence induction (the so-called OJIPSMT transient) is a signature of several photosynthetic reactions. Here, we show that the slow (seconds to minutes) S to M fluorescence rise is reduced or absent in the stt7 mutant (which is locked in state 1) in C. reinhardtii. This suggests that the SM rise in wild type C. reinhardtii may be due to state 2 (low fluorescence state; larger antenna in PS I) to state 1 (high fluorescence state; larger antenna in PS II) transition, and thus, it can be used as an efficient and quick method to monitor state transitions in algae, as has already been shown in cyanobacteria (Papageorgiou et al. 1999, 2007; Kaňa et al. 2012). We also discuss our results on the effects of (1) 3-(3,4-dichlorophenyl)-1,4-dimethyl urea, an inhibitor of electron transport; (2) n-propyl gallate, an inhibitor of alternative oxidase (AOX) in mitochondria and of plastid terminal oxidase in chloroplasts; (3) salicylhydroxamic acid, an inhibitor of AOX in mitochondria; and (4) carbonyl cyanide p-trifluoromethoxyphenylhydrazone, an uncoupler of phosphorylation, which dissipates proton gradient across membranes. Based on the data presented in this paper, we conclude that the slow PSMT fluorescence transient in C. reinhardtii is due to the superimposition of, at least, two phenomena: qE dependent non-photochemical quenching of the excited state of Chl, and state transitions. PMID:25663564

  18. X-ray dense cellular inclusions in the cells of the green alga Chlamydomonas reinhardtii as seen by soft-x-ray microscopy

    SciTech Connect

    Stead, A.D.; Ford, T.W.; Page, A.M.; Brown, J.T.; Meyer-Ilse, W.

    1997-04-01

    Soft x-rays, having a greater ability to penetrate biological material than electrons, have the potential for producing images of intact, living cells. In addition, by using the so-called {open_quotes}water window{close_quotes} area of the soft x-ray spectrum, a degree of natural contrast is introduced into the image due to differential absorption of the wavelengths by compounds with a high carbon content compared to those with a greater oxygen content. The variation in carbon concentration throughout a cell therefore generates an image which is dependent upon the carbon density within the specimen. Using soft x-ray contact microscopy the authors have previously examined the green alga Chlamydomonas reinhardtii, and the most prominent feature of the cells are the numerous x-ray absorbing spheres, But they were not seen by conventional transmission electron microscopy. Similar structures have also been reported by the Goettingen group using their cryo transmission x-ray microscope at BESSY. Despite the fact that these spheres appear to occupy up to 20% or more of the cell volume when seen by x-ray microscopy, they are not visible by transmission electron microscopy. Given the difficulties and criticisms associated with soft x-ray contact microscopy, the present study was aimed at confirming the existence of these cellular inclusions and learning more of their possible chemical composition.

  19. Requirement for Asn298 on D1 protein for oxygen evolution: analyses by exhaustive amino acid substitution in the green alga Chlamydomonas reinhardtii.

    PubMed

    Kuroda, Hiroshi; Kodama, Natsumi; Sun, Xiao-Yu; Ozawa, Shin-ichiro; Takahashi, Yuichiro

    2014-07-01

    PSII generates strong oxidants used for water oxidation. The secondary electron donor, Y(Z), is Tyr161 on PSII reaction center D1 protein and mediates electron transfer from the oxygen-evolving Mn(4)CaO(5) cluster to the primary electron donor, P680. The latest PSII crystal structure revealed the presence of a hydrogen bond network around Y(Z), which is anticipated to play important roles in the electron and proton transfer reactions. Y(Z) forms a hydrogen bond with His190 which in turn forms a hydrogen bond with Asn298 on D1 protein. Although functional roles of Y(Z) and His190 have already been characterized, little is known about the functional role of Asn298. Here we have generated 19 mutants from a green alga Chlamydomonas reinhardtii, in which the Asn298 has been substituted by each of the other 19 amino acid residues. All mutants showed significantly impaired or no photosynthetic growth. Seven mutants capable of photosynthetic growth showed oxygen-evolving activity although at a significantly reduced rate. Interestingly the oxygen-evolving activity of these mutants was markedly photosensitive. The 19 mutants accumulated PSII at variable levels and showed a light-induced electron transfer reaction from 1,5-diphenylcarbazide (DPC) to 2,6-dichlorophenolindophenol (DCIP), suggesting that Asn298 is important for the function and photoprotection of the Mn(4)CaO(5) cluster. PMID:24853102

  20. Expression and membrane-targeting of an active plant cytochrome P450 in the chloroplast of the green alga Chlamydomonas reinhardtii.

    PubMed

    Gangl, Doris; Zedler, Julie A Z; Włodarczyk, Artur; Jensen, Poul Erik; Purton, Saul; Robinson, Colin

    2015-02-01

    The unicellular green alga Chlamydomonas reinhardtii has potential as a cell factory for the production of recombinant proteins and other compounds, but mainstream adoption has been hindered by a scarcity of genetic tools and a need to identify products that can be generated in a cost-effective manner. A promising strategy is to use algal chloroplasts as a site for synthesis of high value bioactive compounds such as diterpenoids since these are derived from metabolic building blocks that occur naturally within the organelle. However, synthesis of these complex plant metabolites requires the introduction of membrane-associated enzymes including cytochrome P450 enzymes (P450s). Here, we show that a gene (CYP79A1) encoding a model P450 can be introduced into the C. reinhardtii chloroplast genome using a simple transformation system. The gene is stably expressed and the P450 is efficiently targeted into chloroplast membranes by means of its endogenous N-terminal anchor domain, where it is active and accounts for 0.4% of total cell protein. These results provide proof of concept for the introduction of diterpenoid synthesis pathways into the chloroplast of C. reinhardtii. PMID:25556316

  1. Some Nutritional Characteristics of a Naturally Occurring Alga (Microcystis sp.) in a Guatemalan Lake

    PubMed Central

    de la Fuente, Gabriel; Flores, Antonio; Molina, Mario R.; Almengor, Leticia; Bressani, Ricardo

    1977-01-01

    The nutritional characteristics of an alga (Microcystis sp.) that occurs naturally in a Guatemalan lake were determined. The sun-dried material proved to have a high protein content (55.6%) and to be a possible good source of calcium and phosphorus (1, 169.1 and 633.4 mg/100 mg, respectively). Amino acid analysis showed that total sulfur amino acids were the most deficient ones, giving a protein score of 42 to the material. The in vitro protein digestibility of the material was 69.5%. Biological trials demonstrated that when the material was offered as the only protein source, very low consumption and a high mortality rate were obtained whether or not the diet was supplemented with 0.4% dl-methionine. However, when the material supplied 25% of the total protein of a corn-algae diet, the protein quality of the cereal was significantly improved (P < 0.05). PMID:16345191

  2. Genome-Wide Identification of Regulatory Elements and Reconstruction of Gene Regulatory Networks of the Green Alga Chlamydomonas reinhardtii under Carbon Deprivation

    PubMed Central

    Vischi Winck, Flavia; Arvidsson, Samuel; Riaño-Pachón, Diego Mauricio; Hempel, Sabrina; Koseska, Aneta; Nikoloski, Zoran; Urbina Gomez, David Alejandro; Rupprecht, Jens; Mueller-Roeber, Bernd

    2013-01-01

    The unicellular green alga Chlamydomonas reinhardtii is a long-established model organism for studies on photosynthesis and carbon metabolism-related physiology. Under conditions of air-level carbon dioxide concentration [CO2], a carbon concentrating mechanism (CCM) is induced to facilitate cellular carbon uptake. CCM increases the availability of carbon dioxide at the site of cellular carbon fixation. To improve our understanding of the transcriptional control of the CCM, we employed FAIRE-seq (formaldehyde-assisted Isolation of Regulatory Elements, followed by deep sequencing) to determine nucleosome-depleted chromatin regions of algal cells subjected to carbon deprivation. Our FAIRE data recapitulated the positions of known regulatory elements in the promoter of the periplasmic carbonic anhydrase (Cah1) gene, which is upregulated during CCM induction, and revealed new candidate regulatory elements at a genome-wide scale. In addition, time series expression patterns of 130 transcription factor (TF) and transcription regulator (TR) genes were obtained for cells cultured under photoautotrophic condition and subjected to a shift from high to low [CO2]. Groups of co-expressed genes were identified and a putative directed gene-regulatory network underlying the CCM was reconstructed from the gene expression data using the recently developed IOTA (inner composition alignment) method. Among the candidate regulatory genes, two members of the MYB-related TF family, Lcr1 (Low-CO2 response regulator 1) and Lcr2 (Low-CO2 response regulator 2), may play an important role in down-regulating the expression of a particular set of TF and TR genes in response to low [CO2]. The results obtained provide new insights into the transcriptional control of the CCM and revealed more than 60 new candidate regulatory genes. Deep sequencing of nucleosome-depleted genomic regions indicated the presence of new, previously unknown regulatory elements in the C. reinhardtii genome. Our work can

  3. Interactions between Photosynthesis and Respiration in the Green Alga Chlamydomonas reinhardtii (Characterization of Light-Enhanced Dark Respiration).

    PubMed

    Xue, X.; Gauthier, D. A.; Turpin, D. H.; Weger, H. G.

    1996-11-01

    The rate of respiratory O2 consumption by Chlamydomonas reinhardtii cell suspensions was greater after a period of photosynthesis than in the preceding dark period. This "light-enhanced dark respiration" (LEDR) was a function of both the duration of illumination and the photon fluence rate. Mass spectrometric measurements of gas exchange indicated that the rate of gross respiratory O2 consumption increased during photosynthesis, whereas gross respiratory CO2 production decreased in a photon fluence rate-dependent manner. The rate of postillumination O2 consumption provided a good measure of the O2 consumption rate in the light. LEDR was substantially decreased by the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea or glycolaldehyde, suggesting that LEDR was photosynthesis-dependent. The onset of photosynthesis resulted in an increase in the cellular levels of phosphoglycerate, malate, and phosphoenolpyruvate, and a decrease in whole-cell ATP and citrate levels; all of these changes were rapidly reversed upon darkening. These results are consistent with a decrease in the rate of respiratory carbon flow during photosynthesis, whereas the increase in respiratory O2 consumption during photosynthesis may be mediated by the export of photogenerated reductant from the chloroplast. We suggest that photosynthesis interacts with respiration at more than one level, simultaneously decreasing the rate of respiratory carbon flow while increasing the rate of respiratory O2 consumption. PMID:12226429

  4. Algae.

    PubMed

    Raven, John A; Giordano, Mario

    2014-07-01

    Algae frequently get a bad press. Pond slime is a problem in garden pools, algal blooms can produce toxins that incapacitate or kill animals and humans and even the term seaweed is pejorative - a weed being a plant growing in what humans consider to be the wrong place. Positive aspects of algae are generally less newsworthy - they are the basis of marine food webs, supporting fisheries and charismatic marine megafauna from albatrosses to whales, as well as consuming carbon dioxide and producing oxygen. Here we consider what algae are, their diversity in terms of evolutionary origin, size, shape and life cycles, and their role in the natural environment and in human affairs. PMID:25004359

  5. New α-glucosidase inhibitors from marine algae-derived Streptomyces sp. OUCMDZ-3434

    PubMed Central

    Chen, Zhengbo; Hao, Jiejie; Wang, Liping; Wang, Yi; Kong, Fandong; Zhu, Weiming

    2016-01-01

    Wailupemycins H (1) and I (2) with a new skeleton coupled two 6-(2-phenylnaphthalene-1-yl)pyrane-2-one nuclei to a –CH2– linkage were identified from the culture of Streptomyces sp. OUCMDZ-3434 associated with the marine algae, Enteromorpha prolifera. Compounds 1 and 2 are two new α-glucosidase inhibitors with the Ki/IC50 values of 16.8/19.7 and 6.0/8.3 μM, respectively. In addition, the absolute configurations of wailupemycins D (3) and E (4) are also resolved in this paper for the first time. PMID:26822662

  6. Evaluation of toxicity and oxidative stress induced by copper oxide nanoparticles in the green alga Chlamydomonas reinhardtii.

    PubMed

    Melegari, Silvia Pedroso; Perreault, François; Costa, Rejane Helena Ribeiro; Popovic, Radovan; Matias, William Gerson

    2013-10-15

    Copper oxide nanoparticles (CuO NP) are frequently employed for their antimicrobial properties in antifouling paints. Their extensive use can contaminate aquatic ecosystems. However, the toxicological effects of this NP in the environment are poorly known. In this study, we evaluated the toxicity and oxidative stress induced by CuO NP on Chlamydomonas reinhardtii using several toxicological assays. CuO NP was found to induce growth inhibition and a significant decrease in carotenoids levels. From data on cells density after 72 h of CuO NP exposure in light, the EC50 value was calculated to be 150.45±1.17 mg L(-1) and the NOEC≤100 mg L(-1). Evaluation of esterase activity demonstrates a decrease in cell metabolism activity with the increase of CuO NP concentration. The CuO NP induced an increase of reactive species level (190±0.45% at 1000 mg L(-1) after 72 h of exposition, compared to control) and lipid peroxidation of cellular membranes (73±2% at 1000 mg L(-1) of CuO NP in 72 h of exposition, compared to control). Investigation of CuO NP uptake showed the presence of NP into C. reinhardtii cells in different sites of the cell and, biomarkers of enzymatic antioxidants showed a change of activity after CuO NP exposition. In conclusion, C. reinhardtii was shown to be sensitive to the presence of CuO NP in their environment and CuO NP treatments induced a toxic response from 0.1 mg L(-1) after 72 h of treatment. PMID:24113166

  7. New tools for chloroplast genetic engineering allow the synthesis of human growth hormone in the green alga Chlamydomonas reinhardtii.

    PubMed

    Wannathong, Thanyanan; Waterhouse, Janet C; Young, Rosanna E B; Economou, Chloe K; Purton, Saul

    2016-06-01

    In recent years, there has been an increasing interest in the exploitation of microalgae in industrial biotechnology. Potentially, these phototrophic eukaryotes could be used for the low-cost synthesis of valuable recombinant products such as bioactive metabolites and therapeutic proteins. The algal chloroplast in particular represents an attractive target for such genetic engineering, both because it houses major metabolic pathways and because foreign genes can be targeted to specific loci within the chloroplast genome, resulting in high-level, stable expression. However, routine methods for chloroplast genetic engineering are currently available only for one species-Chlamydomonas reinhardtii-and even here, there are limitations to the existing technology, including the need for an expensive biolistic device for DNA delivery, the lack of robust expression vectors, and the undesirable use of antibiotic resistance markers. Here, we describe a new strain and vectors for targeted insertion of transgenes into a neutral chloroplast locus that (i) allow scar-less fusion of a transgenic coding sequence to the promoter/5'UTR element of the highly expressed endogenous genes psaA or atpA, (ii) employ the endogenous gene psbH as an effective but benign selectable marker, and (iii) ensure the successful integration of the transgene construct in all transformant lines. Transformation is achieved by a simple and cheap method of agitation of a DNA/cell suspension with glass beads, with selection based on the phototrophic rescue of a cell wall-deficient ΔpsbH strain. We demonstrate the utility of these tools in the creation of a transgenic line that produces high levels of functional human growth hormone. PMID:26887319

  8. Rapid method for DNA isolation from a tough cell wall green alga Tetraspora sp. CU2551.

    PubMed

    Maneeruttanarungroj, Cherdsak; Incharoensakdi, Aran

    2016-06-01

    Genetic studies are important to understand the complex biological system of various organisms. Some eukaryotic green organisms have tough cell wall which precludes the efficient extraction of the genetic materials. Here, we developed the method for simple and rapid isolation of high quality DNA from a green alga Tetraspora sp. CU2551. The cell homogenization procedures were combined with physical force plus heat treatment to disrupt the cell envelope of Tetraspora sp. CU2551. Without protease treatment, vortexing with glass bead for 30-105 s at 70 °C led to the isolation of a high purity DNA which was suitable for downstream process. The improved method was successfully developed and could be applied for the rapid isolation of DNA from other unicellular and filamentous green microalgal strains. PMID:27116965

  9. Cellular Fe-hydroxides and heavy metal sorption in Euglena sp. (algae): implications for biomineralization

    SciTech Connect

    Mann, H.; Beveridge, T.O. Fyfe, W.S.; Tazaki, K.

    1985-01-01

    STEM imagery and electron diffraction patterns of Euglena sp. reveal pronounced intra and cellular-membrane aggregates of Fe-hydroxides (some lepidocrocite), in natural communities from tailings waters, Elliott Lake, Ontario. Pure isolates of Euglena sp. contain 40-70% Fe by dry weight and in addition average Al 28,000 ppm, Sr 150, Ba 40, Zn 150, Mn 250, Ni 120, Pb 1600, Th 70, Cu 200 and U 180. In tailings waters, Fe solute concentrations average 560 ppm and U 50 ppb. Concentration factors for Fe, Ba, Zn, Mn, Ti, V, Ni, Pb, Cr, Ag, Co and Cu in algae referenced to average world river waters are greater than or equal to 10/sup 6/. These results endorse the premise that microorganisms mediate transfer of many solutes between the hydrosphere and sedimentary regime.

  10. RNAi Knock-Down of LHCBM1, 2 and 3 Increases Photosynthetic H2 Production Efficiency of the Green Alga Chlamydomonas reinhardtii

    PubMed Central

    Oey, Melanie; Ross, Ian L.; Stephens, Evan; Steinbeck, Janina; Wolf, Juliane; Radzun, Khairul Adzfa; Kügler, Johannes; Ringsmuth, Andrew K.; Kruse, Olaf; Hankamer, Ben

    2013-01-01

    Single cell green algae (microalgae) are rapidly emerging as a platform for the production of sustainable fuels. Solar-driven H2 production from H2O theoretically provides the highest-efficiency route to fuel production in microalgae. This is because the H2-producing hydrogenase (HYDA) is directly coupled to the photosynthetic electron transport chain, thereby eliminating downstream energetic losses associated with the synthesis of carbohydrate and oils (feedstocks for methane, ethanol and oil-based fuels). Here we report the simultaneous knock-down of three light-harvesting complex proteins (LHCMB1, 2 and 3) in the high H2-producing Chlamydomonas reinhardtii mutant Stm6Glc4 using an RNAi triple knock-down strategy. The resultant Stm6Glc4L01 mutant exhibited a light green phenotype, reduced expression of LHCBM1 (20.6% ±0.27%), LHCBM2 (81.2% ±0.037%) and LHCBM3 (41.4% ±0.05%) compared to 100% control levels, and improved light to H2 (180%) and biomass (165%) conversion efficiencies. The improved H2 production efficiency was achieved at increased solar flux densities (450 instead of ∼100 µE m−2 s−1) and high cell densities which are best suited for microalgae production as light is ideally the limiting factor. Our data suggests that the overall improved photon-to-H2 conversion efficiency is due to: 1) reduced loss of absorbed energy by non-photochemical quenching (fluorescence and heat losses) near the photobioreactor surface; 2) improved light distribution in the reactor; 3) reduced photoinhibition; 4) early onset of HYDA expression and 5) reduction of O2-induced inhibition of HYDA. The Stm6Glc4L01 phenotype therefore provides important insights for the development of high-efficiency photobiological H2 production systems. PMID:23613840

  11. Cd2+ Toxicity to a Green Alga Chlamydomonas reinhardtii as Influenced by Its Adsorption on TiO2 Engineered Nanoparticles

    PubMed Central

    Yang, Wei-Wan; Miao, Ai-Jun; Yang, Liu-Yan

    2012-01-01

    In the present study, Cd2+ adsorption on polyacrylate-coated TiO2 engineered nanoparticles (TiO2-ENs) and its effect on the bioavailability as well as toxicity of Cd2+ to a green alga Chlamydomonas reinhardtii were investigated. TiO2-ENs could be well dispersed in the experimental medium and their pHpzc is approximately 2. There was a quick adsorption of Cd2+ on TiO2-ENs and a steady state was reached within 30 min. A pseudo-first order kinetics was found for the time-related changes in the amount of Cd2+ complexed with TiO2-ENs. At equilibrium, Cd2+ adsorption followed the Langmuir isotherm with the maximum binding capacity 31.9, 177.1, and 242.2 mg/g when the TiO2-EN concentration was 1, 10, and 100 mg/l, respectively. On the other hand, Cd2+ toxicity was alleviated in the presence of TiO2-ENs. Algal growth was less suppressed in treatments with comparable total Cd2+ concentration but more TiO2-ENs. However, such toxicity difference disappeared and all the data points could be fitted to a single Logistic dose-response curve when cell growth inhibition was plotted against the free Cd2+ concentration. No detectable amount of TiO2-ENs was found to be associated with the algal cells. Therefore, TiO2-ENs could reduce the free Cd2+ concentration in the toxicity media, which further lowered its bioavailability and toxicity to C. reinhardtii. PMID:22403644

  12. RNAi knock-down of LHCBM1, 2 and 3 increases photosynthetic H2 production efficiency of the green alga Chlamydomonas reinhardtii.

    PubMed

    Oey, Melanie; Ross, Ian L; Stephens, Evan; Steinbeck, Janina; Wolf, Juliane; Radzun, Khairul Adzfa; Kügler, Johannes; Ringsmuth, Andrew K; Kruse, Olaf; Hankamer, Ben

    2013-01-01

    Single cell green algae (microalgae) are rapidly emerging as a platform for the production of sustainable fuels. Solar-driven H2 production from H2O theoretically provides the highest-efficiency route to fuel production in microalgae. This is because the H2-producing hydrogenase (HYDA) is directly coupled to the photosynthetic electron transport chain, thereby eliminating downstream energetic losses associated with the synthesis of carbohydrate and oils (feedstocks for methane, ethanol and oil-based fuels). Here we report the simultaneous knock-down of three light-harvesting complex proteins (LHCMB1, 2 and 3) in the high H2-producing Chlamydomonas reinhardtii mutant Stm6Glc4 using an RNAi triple knock-down strategy. The resultant Stm6Glc4L01 mutant exhibited a light green phenotype, reduced expression of LHCBM1 (20.6% ±0.27%), LHCBM2 (81.2% ±0.037%) and LHCBM3 (41.4% ±0.05%) compared to 100% control levels, and improved light to H2 (180%) and biomass (165%) conversion efficiencies. The improved H2 production efficiency was achieved at increased solar flux densities (450 instead of ∼100 µE m(-2) s(-1)) and high cell densities which are best suited for microalgae production as light is ideally the limiting factor. Our data suggests that the overall improved photon-to-H2 conversion efficiency is due to: 1) reduced loss of absorbed energy by non-photochemical quenching (fluorescence and heat losses) near the photobioreactor surface; 2) improved light distribution in the reactor; 3) reduced photoinhibition; 4) early onset of HYDA expression and 5) reduction of O2-induced inhibition of HYDA. The Stm6Glc4L01 phenotype therefore provides important insights for the development of high-efficiency photobiological H2 production systems. PMID:23613840

  13. Influence of agglomeration of cerium oxide nanoparticles and speciation of cerium(III) on short term effects to the green algae Chlamydomonas reinhardtii.

    PubMed

    Röhder, Lena A; Brandt, Tanja; Sigg, Laura; Behra, Renata

    2014-07-01

    Cerium oxide nanoparticles (CeO2 NP) are increasingly used in industrial applications and may be released to the aquatic environment. The fate of CeO2 NP and effects on algae are largely unknown. In this study, the short term effects of CeO2 NP in two different agglomeration states on the green algae Chlamydomonas reinhardtii were examined. The role of dissolved cerium(III) on toxicity, its speciation and the dissolution of CeO2 NP were considered. The role of cell wall of C. reinhardtii as a barrier and its influence on the sensitivity to CeO2 NP and cerium(III) was evaluated by testing both, the wild type and the cell wall free mutant of C. reinhardtii. Characterization showed that CeO2 NP had a surface charge of ∼0mV at physiological pH and agglomerated in exposure media. Phosphate stabilized CeO2 NP at pH 7.5 over 24h. This effect was exploited to test CeO2 NP dispersed in phosphate with a mean size of 140nm and agglomerated in absence of phosphate with a mean size of 2000nm. The level of dissolved cerium(III) in CeO2 NP suspensions was very low and between 0.1 and 27nM in all tested media. Exposure of C. reinhardtii to Ce(NO3)3 decreased the photosynthetic yield in a concentration dependent manner with EC50 of 7.5±0.84μM for wild type and EC50 of 6.3±0.53μM for the cell wall free mutant. The intracellular level of reactive oxygen species (ROS) increased upon exposure to Ce(NO3)3 with effective concentrations similar to those inhibiting photosynthesis. The agglomerated CeO2 NP caused a slight decrease of photosynthetic yield at the highest concentrations (100μM), while no effect was observed for dispersed CeO2 NP. The low toxicity of agglomerated CeO2 NP was attributed quantitatively to Ce(3+) ions co-occurring in the nanoparticle suspension whereas for dispersed CeO2 NP, dissolved Ce(3+) was precipitated with phosphate and not bioavailable. Furthermore CeO2 NP did not affect the intracellular ROS level. The cell wall free mutant and wild type of C

  14. Defluviitalea phaphyphila sp. nov., a Novel Thermophilic Bacterium That Degrades Brown Algae

    PubMed Central

    Ji, Shi-Qi; Wang, Bing; Lu, Ming

    2015-01-01

    Brown algae are one of the largest groups of oceanic primary producers for CO2 removal and carbon sinks for coastal regions. However, the mechanism for brown alga assimilation remains largely unknown in thermophilic microorganisms. In this work, a thermophilic alginolytic community was enriched from coastal sediment, from which an obligate anaerobic and thermophilic bacterial strain, designated Alg1, was isolated. Alg1 shared a 16S rRNA gene identity of 94.6% with Defluviitalea saccharophila LIND6LT2T. Phenotypic, chemotaxonomic, and phylogenetic studies suggested strain Alg1 represented a novel species of the genus Defluviitalea, for which the name Defluviitalea phaphyphila sp. nov. is proposed. Alg1 exhibited an intriguing ability to convert carbohydrates of brown algae, including alginate, laminarin, and mannitol, to ethanol and acetic acid. Three gene clusters participating in this process were predicted to be in the genome, and candidate enzymes were successfully expressed, purified, and characterized. Six alginate lyases were demonstrated to synergistically deconstruct alginate into unsaturated monosaccharide, followed by one uronic acid reductase and two 2-keto-3-deoxy-d-gluconate (KDG) kinases to produce pyruvate. A nonclassical mannitol 1-phosphate dehydrogenase, catalyzing d-mannitol 1-phosphate to fructose 1-phosphate in the presence of NAD+, and one laminarase also were disclosed. This work revealed that a thermophilic brown alga-decomposing system containing numerous novel thermophilic alginate lyases and a unique mannitol 1-phosphate dehydrogenase was adopted by the natural ethanologenic strain Alg1 during the process of evolution in hostile habitats. PMID:26590273

  15. Defluviitalea phaphyphila sp. nov., a Novel Thermophilic Bacterium That Degrades Brown Algae.

    PubMed

    Ji, Shi-Qi; Wang, Bing; Lu, Ming; Li, Fu-Li

    2016-02-01

    Brown algae are one of the largest groups of oceanic primary producers for CO2 removal and carbon sinks for coastal regions. However, the mechanism for brown alga assimilation remains largely unknown in thermophilic microorganisms. In this work, a thermophilic alginolytic community was enriched from coastal sediment, from which an obligate anaerobic and thermophilic bacterial strain, designated Alg1, was isolated. Alg1 shared a 16S rRNA gene identity of 94.6% with Defluviitalea saccharophila LIND6LT2(T). Phenotypic, chemotaxonomic, and phylogenetic studies suggested strain Alg1 represented a novel species of the genus Defluviitalea, for which the name Defluviitalea phaphyphila sp. nov. is proposed. Alg1 exhibited an intriguing ability to convert carbohydrates of brown algae, including alginate, laminarin, and mannitol, to ethanol and acetic acid. Three gene clusters participating in this process were predicted to be in the genome, and candidate enzymes were successfully expressed, purified, and characterized. Six alginate lyases were demonstrated to synergistically deconstruct alginate into unsaturated monosaccharide, followed by one uronic acid reductase and two 2-keto-3-deoxy-d-gluconate (KDG) kinases to produce pyruvate. A nonclassical mannitol 1-phosphate dehydrogenase, catalyzing D-mannitol 1-phosphate to fructose 1-phosphate in the presence of NAD(+), and one laminarase also were disclosed. This work revealed that a thermophilic brown alga-decomposing system containing numerous novel thermophilic alginate lyases and a unique mannitol 1-phosphate dehydrogenase was adopted by the natural ethanologenic strain Alg1 during the process of evolution in hostile habitats. PMID:26590273

  16. Ozonation of the marine dinoflagellate alga Amphidinium sp.--implications for ballast water disinfection.

    PubMed

    Oemcke, D J; Hans van Leeuwen, J

    2005-12-01

    Ozone has been investigated for its potential to remove marine dinoflagellate algae from ships' ballast water. Dinoflagellate algae, Amphidinium sp. isolated from the Great Barrier Reef, Townsville, Australia were used as indicators since these produce a type of cyst that is difficult to inactivate, but are relatively easy to culture. The ozonation experiments have demonstrated a high ozone demand for inactivation of the algal cultures, which increases as the culture ages. The main ozone demand in seawater is due to its reaction with bromide to form bromine compounds. The non-bromide ozone demand has been estimated by measuring the residuals produced after various doses of ozone. The Amphidinium sp. show an unexpected response to both ozonation and bromination, with an instantaneous inactivation of the organisms for all doses that produced an oxidant residual in the seawater, followed by an effect of the disinfection residual. The standard design procedure of comparing Ct will not be effective for predicting the response of the organism to varying dose, C, and contact time, t, and a plot of ozone produced oxidant residual against organism inactivation for various contact times is proposed for design purposes. High doses of ozone (5-11 mg/L) and up to 6h of residual contact were required for a 4-log inactivation of the Amphidinium sp. Ozonation is likely to be a difficult technology to implement for organisms with this ozone requirement in combination with characteristics of ballast tanks, which contain areas of sediments high in detritus and areas of corrosion. PMID:16289281

  17. N-ACYL HOMOSERINE LACTONe LACTONASE, AiiA, INACTIVATION OF QUORUM-SENSING AGONISTS PRODUCED BY CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA) AND CHARACTERIZATION OF aiiA TRANSGENIC ALGAE(1).

    PubMed

    Rajamani, Sathish; Teplitski, Max; Kumar, Anil; Krediet, Cory J; Sayre, Richard T; Bauer, Wolfgang D

    2011-10-01

    Eukaryotes such as plants and the unicellular green alga Chlamydomonas reinhardtii P. A. Dang. produce and secrete compounds that mimic N-acyl homoserine lactone (AHL) bacterial quorum-sensing (QS) signals and alter QS-regulated gene expression in the associated bacteria. Here, we show that the set of C. reinhardtii signal-mimic compounds that activate the CepR AHL receptor of Burkholderia cepacia are susceptible to inactivation by AiiA, an AHL lactonase enzyme of Bacillus. Inactivation of these algal mimics by AiiA suggests that the CepR-stimulatory class of mimics produced by C. reinhardtii may have a conserved lactone ring structure in common with AHL QS signals. To examine the role of AHL mimic compounds in the interactions of C. reinhardtii with bacteria, the aiiA gene codon optimized for Chlamydomonas was generated for the expression of AiiA as a chimeric fusion with cyan fluorescent protein (AimC). Culture filtrates of transgenic strains expressing the fusion protein AimC had significantly reduced levels of CepR signal-mimic activities. When parental and transgenic algae were cultured with a natural pond water bacterial community, a morphologically distinct, AHL-producing isolate of Aeromonas veronii was observed to colonize the transgenic algal cultures and form biofilms more readily than the parental algal cultures, indicating that secretion of the CepR signal mimics by the alga can significantly affect its interactions with bacteria it encounters in natural environments. The parental alga was also able to sequester and/or destroy AHLs in its growth media to further disrupt or manipulate bacterial QS. PMID:27020200

  18. Total lipid production of the green alga Nannochloropsis sp. QII under different nitrogen regimes

    SciTech Connect

    Suen, Yu.; Hubbard, J.S.; Holzer, G.; Tornabene, T.G.

    1987-06-01

    The green alga Nannochloropsis sp. QII was cultivated in media with sufficient and growth-limiting levels of nitrogen (nitrate). Nitrogen deficiency promoted lipid synthesis yielding cells with lipids comprising 55% of the biomass. The major lipids were triacylglycerols (79%), polar lipids (9%) and hydrocarbons (2.5%). The polar lipids consisted of a broad range of phospholipids, glycolipids and sulfolipids. Other lipids identified were pigments, free fatty acids, saponifiable and unsaponifiable sterol derivatives, various glycerides, a family of alkyl-1, 4-dioxane derivatives and a series of alkyl- and hydroxy-alkyl-dimethyl-acetals. Experiments in which /sup 14/CO/sub 2/ was provided at different times in the growth cycle demonstrated that enhanced lipid biosynthesis at low nitrogen levels resulted principally from de novo CO/sub 2/ fixation.

  19. Sphacelaria lacustris sp. nov. , a freshwater brown alga from Lake Michigan

    SciTech Connect

    Schloesser, R.E.; Blum, J.L.

    1980-06-01

    The growth, reproduction and ultrasturcture of a new freshwater phaeophyte, Sphacelaria lacustris sp. nov., are described. The plant occurs as a minute calcified thallus at 5 to 15 m depth along the western shoreline of Lake Michigan. Both freshly collected and laboratory grown plants show apical growth of erect and basal filaments, intermittent longitudinal divisions in filament segments, vegetative reproduction by propagules, numerous parietal chloroplasts and an absence of pyrenoids, characteristics of Sphacelaria. This material is separated from the only other freshwater species in the genus (S. fluviatilis Jao) at least by differences in longitudinal septation, in branching, in its propagules and in general aspect. Between this plant and marine brown algae there are essential similarities of ultrastructure of cell wall and pores, chloroplasts, mitochondria, nucleus and the production/excretion of physodes.

  20. Chlamydomonas: A Model Green Plant.

    ERIC Educational Resources Information Center

    Sheffield, E.

    1985-01-01

    Discusses the instructional potential of Chlamydomonas in providing a basis for a range of experimental investigations to illustrate basic biological phenomena. Describes the use of this algae genus in studies of population growth, photosynthesis, and mating behavior. Procedures for laboratory exercises are included. (ML)

  1. BIODIVERSITY OF CORALLINE ALGAE IN THE NORTHEASTERN ATLANTIC INCLUDING CORALLINA CAESPITOSA SP. NOV. (CORALLINOIDEAE, RHODOPHYTA)(1).

    PubMed

    Walker, Rachel H; Brodie, Juliet; Russell, Stephen; Irvine, Linda M; Orfanidis, Sotiris

    2009-02-01

    The Corallinoideae (Corallinaceae) is represented in the northeastern Atlantic by Corallina officinalis L.; Corallina elongata J. Ellis et Sol.; Haliptilon squamatum (L.) H. W. Johans., L. M. Irvine et A. M. Webster; and Jania rubens (L.) J. V. Lamour. The delimitation of these geniculate coralline red algae is based primarily on morphological characters. Molecular analysis based on cox1 and 18S rRNA gene phylogenies supported the division of the Corallinoideae into the tribes Janieae and Corallineae. Within the Janieae, a sequence difference of 46-48 bp (8.6%-8.9%) between specimens of H. squamatum and J. rubens in the cox1 phylogeny leads us to conclude that they are congeneric. J. rubens var. rubens and J. rubens var. corniculata (L.) Yendo clustered together in both phylogenies, suggesting that for those genes, there was no genetic basis for the morphological variation. Within the Corallineae, it appears that in some regions, the name C. elongata has been misapplied. C. officinalis samples formed two clusters that differed by 45-54 bp (8.4%-10.0%), indicating species-level divergence, and morphological differences were sufficient to define two species. One of these clusters was consistent with the morphology of the type specimen of C. officinalis (LINN 1293.9). The other species cluster is therefore described here as Corallina caespitosa sp. nov. This study has demonstrated that there is a clear need for a revision of the genus Corallina to determine the extent of "pseudocryptic" diversity in this group of red algae. PMID:27033664

  2. Molecular and biochemical characterization of mannitol-1-phosphate dehydrogenase from the model brown alga Ectocarpus sp.

    PubMed

    Bonin, Patricia; Groisillier, Agnès; Raimbault, Alice; Guibert, Anaïs; Boyen, Catherine; Tonon, Thierry

    2015-09-01

    The sugar alcohol mannitol is important in the food, pharmaceutical, medical and chemical industries. It is one of the most commonly occurring polyols in nature, with the exception of Archaea and animals. It has a range of physiological roles, including as carbon storage, compatible solute, and osmolyte. Mannitol is present in large amounts in brown algae, where its synthesis involved two steps: a mannitol-1-phosphate dehydrogenase (M1PDH) catalyzes a reversible reaction between fructose-6-phosphate (F6P) and mannitol-1-phosphate (M1P) (EC 1.1.1.17), and a mannitol-1-phosphatase hydrolyzes M1P to mannitol (EC 3.1.3.22). Analysis of the model brown alga Ectocarpus sp. genome provided three candidate genes for M1PDH activities. We report here the sequence analysis of Ectocarpus M1PDHs (EsM1PDHs), and the biochemical characterization of the recombinant catalytic domain of EsM1PDH1 (EsM1PDH1cat). Ectocarpus M1PDHs are representatives of a new type of modular M1PDHs among the polyol-specific long-chain dehydrogenases/reductases (PSLDRs). The N-terminal domain of EsM1PDH1 was not necessary for enzymatic activity. Determination of kinetic parameters indicated that EsM1PDH1cat displayed higher catalytic efficiency for F6P reduction compared to M1P oxidation. Both activities were influenced by NaCl concentration and inhibited by the thioreactive compound pHMB. These observations were completed by measurement of endogenous M1PDH activity and of EsM1PDH gene expression during one diurnal cycle. No significant changes in enzyme activity were monitored between day and night, although transcription of two out of three genes was altered, suggesting different levels of regulation for this key metabolic pathway in brown algal physiology. PMID:26232554

  3. Genomics of Volvocine Algae

    PubMed Central

    Umen, James G.; Olson, Bradley J.S.C.

    2015-01-01

    Volvocine algae are a group of chlorophytes that together comprise a unique model for evolutionary and developmental biology. The species Chlamydomonas reinhardtii and Volvox carteri represent extremes in morphological diversity within the Volvocine clade. Chlamydomonas is unicellular and reflects the ancestral state of the group, while Volvox is multicellular and has evolved numerous innovations including germ-soma differentiation, sexual dimorphism, and complex morphogenetic patterning. The Chlamydomonas genome sequence has shed light on several areas of eukaryotic cell biology, metabolism and evolution, while the Volvox genome sequence has enabled a comparison with Chlamydomonas that reveals some of the underlying changes that enabled its transition to multicellularity, but also underscores the subtlety of this transition. Many of the tools and resources are in place to further develop Volvocine algae as a model for evolutionary genomics. PMID:25883411

  4. Antioxidant, cytotoxic, antitumor, and protective DNA damage metabolites from the red sea brown alga Sargassum sp

    PubMed Central

    Ayyad, Seif-Eldin N.; Ezmirly, Saleh T.; Basaif, Salim A.; Alarif, Walied M.; Badria, Adel F.; Badria, Farid A.

    2011-01-01

    Background: Macroalgae can be viewed as a potential antioxidant and anti-inflammatory sources owing to their capability of producing compounds for its protection from environmental factors such as heat, pollution, stress, oxygen concentration, and UV radiations. Objective: To isolate major compounds which are mainly responsible for the pharmacological activity of brown alga under investigation, Sargassum sp. Materials and Methods: Algal material was air dried, extracted with a mixture of organic solvents, and fractionated with different adsorbents. The structures of obtained pure compounds were elucidated with different spectroscopic techniques, and two pure materials were tested for protection of DNA from damage, antioxidant, antitumor, and cytotoxicity. Results: Four pure compounds were obtained, of which fucosterol (1) and fucoxanthin (4) were tested; it was found that fucoxanthin has strong antioxidant and cytotoxicity against breast cancer (MCF-7) with IC50 = 11.5 μg/ml. Conclusion: The naturally highly conjugated safe compound fucoxanthin could be used as antioxidant and as an antitumor compound. PMID:22022163

  5. Amylibacter ulvae sp. nov., a new alphaproteobacterium isolated from the Pacific green alga Ulva fenestrata.

    PubMed

    Nedashkovskaya, Olga I; Kukhlevskiy, Andrey D; Zhukova, Natalia V; Kim, Seung Bum

    2016-04-01

    A strictly aerobic, Gram-stain-negative, rod-shaped and non-motile bacterium, designated strain 6Alg 255(T), was isolated from the green alga Ulva fenestrata. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that the novel strain affiliated to the family Rhodobacteraceae of the class Alphaproteobacteria being most closely related to Amylibacter marinus LMG 28364(T) with 16S rRNA gene sequence similarity of 97.2 %. Strain 6Alg 255(T) grew with 0.5-6.0 % NaCl and at 4-33 °C, hydrolysed aesculin, casein, gelatin and urea. The DNA G + C content was 50.4 mol%. The prevalent fatty acids were C18:1 ω7c and C16:0. The polar lipid profile was characterized by the presence of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and unidentified aminolipid. The major respiratory quinone was Q-10. The significant molecular distinctiveness between the novel isolate and its nearest neighbour was strongly supported by the differences in physiological and biochemical tests. Therefore, strain 6Alg 255(T) represents a novel species of the genus Amylibacter, for which the name Amylibacter ulvae sp. nov. is proposed. The type strain is 6Alg 255(T) (=KCTC 32465(T) = KMM 6515(T)). PMID:26762377

  6. A Comparative biochemical study on two marine endophytes, Bacterium SRCnm and Bacillus sp. JS, Isolated from red sea algae.

    PubMed

    Ahmed, Eman Fadl; Hassan, Hossam Mokhtar; Rateb, Mostafa Ezzat; Abdel-Wahab, Noha; Sameer, Somayah; Aly Taie, Hanan Anwar; Abdel-Hameed, Mohammed Sayed; Hammouda, Ola

    2016-01-01

    Two marine endophytic bacteria were isolated from the Red Sea algae; a red alga; Acanthophora dendroides and the brown alga Sargassum sabrepandum. The isolates were identified based on their 16SrRNA sequences as Bacterium SRCnm and Bacillus sp. JS. The objective of this study was to investigate the potential anti-microbial and antioxidant activities of the extracts of the isolated bacteria grown in different nutrient conditions. Compared to amoxicillin (25μg/disk) and erythromycin (15μg/disk), the extracts of Bacterium SRCn min media II, III, IV and V were potent inhibitors of the gram-positive bacterium Sarcina maxima even at low concentrations. Also, the multidrug resistant Staphylococcus aureus(MRSA) was more sensitive to the metabolites produced in medium (II) of the same endophyte than erythromycin (15μg/disk). A moderate activity of the Bacillus sp. JS extracts of media I and II was obtained against the same pathogen. The total compounds (500ug/ml) of both isolated endophytes showed moderate antioxidant activities (48.9% and 46.1%, respectively). LC/MS analysis of the bacterial extracts was carried out to investigate the likely natural products produced. Cyclo(D-cis-Hyp-L-Leu), dihydrosphingosine and 2-Amino-1,3-hexadecanediol were identified in the fermentation medium of Bacterium SRCnm, whereas cyclo (D-Pro-L-Tyr) and cyclo (L-Leu-L-Pro) were the suggested compounds of Bacillus sp. JS. PMID:26826831

  7. First Report of Pseudobodo sp, a New Pathogen for a Potential Energy-Producing Algae: Chlorella vulgaris Cultures

    PubMed Central

    Zhang, Bangzhou; Yang, Luxi; Zhang, Huajun; Zhang, Jingyan; Li, Yi; Zheng, Wei; Tian, Yun; Liu, Jingwen; Zheng, Tianling

    2014-01-01

    Chlorella vulgaris, is a kind of single-celled green algae, which could serve as a potential source of food and energy because of its photosynthetic efficiency. In our study, a pathogenic organism targeting C. vulgaris was discovered. The algae-lytic activity relates to a fraction from lysates of infected C. vulgaris that was blocked upon filtration through a 3 µm filter. 18S rRNA gene sequence analysis revealed that it shared 99.0% homology with the protist Pseudobodo tremulans. Scanning electron microscope analysis showed that Pseudobodo sp. KD51 cells were approximately 4–5 µm long, biflagellate with an anterior collar around the anterior part of the cell in unstressed feeding cells. Besides the initial host, Pseudobodo sp. KD51 could also kill other algae, indicating its relatively wide predatory spectrum. Heat stability, pH and salinity tolerance experiments were conducted to understand their effects on its predatory activities, and the results showed that Pseudobodo sp. KD51 was heat-sensitive, and pH and salinity tolerant. PMID:24599263

  8. First report of Pseudobodo sp, a new pathogen for a potential energy-producing algae: Chlorella vulgaris cultures.

    PubMed

    Chen, Zhangran; Lei, Xueqian; Zhang, Bangzhou; Yang, Luxi; Zhang, Huajun; Zhang, Jingyan; Li, Yi; Zheng, Wei; Tian, Yun; Liu, Jingwen; Zheng, Tianling

    2014-01-01

    Chlorella vulgaris, is a kind of single-celled green algae, which could serve as a potential source of food and energy because of its photosynthetic efficiency. In our study, a pathogenic organism targeting C. vulgaris was discovered. The algae-lytic activity relates to a fraction from lysates of infected C. vulgaris that was blocked upon filtration through a 3 µm filter. 18S rRNA gene sequence analysis revealed that it shared 99.0% homology with the protist Pseudobodo tremulans. Scanning electron microscope analysis showed that Pseudobodo sp. KD51 cells were approximately 4-5 µm long, biflagellate with an anterior collar around the anterior part of the cell in unstressed feeding cells. Besides the initial host, Pseudobodo sp. KD51 could also kill other algae, indicating its relatively wide predatory spectrum. Heat stability, pH and salinity tolerance experiments were conducted to understand their effects on its predatory activities, and the results showed that Pseudobodo sp. KD51 was heat-sensitive, and pH and salinity tolerant. PMID:24599263

  9. Winogradskyella eckloniae sp. nov., a marine bacterium isolated from the brown alga Ecklonia cava.

    PubMed

    Kim, Ji-Young; Park, So-Hyun; Seo, Ga-Young; Kim, Young-Ju; Oh, Duck-Chul

    2015-09-01

    A novel bacterial strain, designated EC29(T), was isolated from the brown alga Ecklonia cava collected on Jeju Island, Republic of Korea. Cells of strain EC29(T) were Gram-stain-negative, aerobic, rod-shaped and motile by gliding. Growth was observed at 10-30 °C (optimum, 20-25 °C), at pH 6.0-9.5 (optimum, pH 7.5) and in the presence of 1-5% (w/v) NaCl. Phylogenetic analyses based on the 16S rRNA gene sequence revealed that the strain belonged to the genus Winogradskyella. Strain EC29(T) exhibited the highest 16S rRNA gene sequence similarities, of 96.5-97.8%, to the type strains of Winogradskyella pulchriflava EM106(T), Winogradskyella echinorum KMM 6211(T) and Winogradskyella ulvae KMM 6390(T). Strain EC29(T) exhibited < 27% DNA-DNA relatedness with Winogradskyella pulchriflava EM106(T) and Winogradskyella echinorum KMM 6211(T). The predominant fatty acids of strain EC29(T) were iso-C15 : 0, iso-C15 : 1 G, C15 : 0, iso-C17 : 0 3-OH, iso-C15 : 0 3-OH and anteiso-C15 : 0. The DNA G+C content was 31.1 mol% and the major respiratory quinone was menaquinone-6 (MK-6). Based on a polyphasic study, strain EC29(T) is considered to represent a novel species of the genus Winogradskyella, for which the name Winogradskyella eckloniae sp. nov. is proposed. The type strain is EC29(T) ( = KCTC 32172(T) = JCM 18703(T)). PMID:25979633

  10. Flavobacterium jejuensis sp. nov., isolated from marine brown alga Ecklonia cava.

    PubMed

    Park, So-Hyun; Kim, Ji-Young; Kim, Young-Ju; Heo, Moon-Soo

    2015-11-01

    A bacterial strain, designated EC11(T) was isolated from brown alga Ecklonia cava collected from Jeju Island, Korea. EC11(T) was identified as a Gram-negative, rod-shaped and yellow-pigmented bacterial strain. The strain EC11(T) grew over a temperature range of 10 °C to 30 °C (optimally at 25 °C), and a pH range of 6.0-10.5 (optimally at pH 7.5). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain EC11(T) belongs to the genus Flavobacterium. Strain EC11(T) shared close similarity with Flavobacterium jumunjinense HME7102(T) (96.4%), Flavobacterium dongtanense LW30(T) (95.8%), Flavobacterium haoranii LQY-7(T) (95.3%), and Flavobacterium urocaniciphilum (95.1%). The major fatty acids (> 5%) were iso-C17:0 3-OH (22.4%), iso-C15:0 3-OH (19.0%), C15:0 (12.4%), summed feature 3 (comprising C16:1 ω7c/ C16:1 ω6c; 9.78%), iso-C15:1 G (9.6%), and iso-C16:0 3-OH (9.0%). The DNA G+C content was 28.1 mol% and the strain contained MK-6 as the predominant menaquinone. The major polar lipids were phosphatidylethanolamine, two unknown aminolipids and three unknown polar lipids. Based on phenotypic, chemotaxonomic and phylogenetic analysis, strain EC11T represents a novel species of the Flavobacterium genus, for which the name Flavobacterium jejuensis sp. nov. is proposed. The type strain of F. jejuensis is EC11(T) (=KCTC 42149(T) = JCM 30735(T)). PMID:26502959

  11. Shewanella algicola sp. nov., a marine bacterium isolated from brown algae.

    PubMed

    Kim, Ji-Young; Yoo, Han-Su; Lee, Dong-Heon; Park, So-Hyun; Kim, Young-Ju; Oh, Duck-Chul

    2016-06-01

    A Gram-stain-negative, aerobic, rod-shaped bacterium motile by means of a single polar flagella, strain ST-6T, was isolated from a brown alga (Sargassum thunbergii) collected in Jeju, Republic of Korea. Strain ST-6T was psychrotolerant, growing at 4-30 °C (optimum 20 °C). Phylogenetic analysis based on 16S rRNA and gyrB gene sequences revealed that strain ST-6T belonged to a distinct lineage in the genus Shewanella. Strain ST-6T was related most closely to Shewanella basaltis J83T, S. gaetbuli TF-27T, S. arctica IT12T, S. vesiculosa M7T and S. aestuarii SC18T, showing 96-97 % and 85-70 % 16S rRNA and gyrB gene sequences similarities, respectively. DNA-DNA relatedness values between strain ST-6T and the type strains of two species of the genus Shewanella were <22.6 %. The major cellular fatty acids (>5 %) were summed feature 3 (comprising C16:1ω7c and/ or iso-C15:0 2-OH), C16:0, iso-C13:0 and C17:1ω8c. The DNA G+C content of strain ST-6Twas 42.4 mol%, and the predominant isoprenoid quinones were menaquinone MK-7 and ubiquinones Q-7 and Q-8. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain ST-6T is considered to represent a novel species of the genus Shewanella, for which the name Shewanella algicola sp. nov. is proposed. The type strain is ST-6T (= KCTC 23253T = JCM 31091T). PMID:26962005

  12. Iron economy in Chlamydomonas reinhardtii

    PubMed Central

    Glaesener, Anne G.; Merchant, Sabeeha S.; Blaby-Haas, Crysten E.

    2013-01-01

    While research on iron nutrition in plants has largely focused on iron-uptake pathways, photosynthetic microbes such as the unicellular green alga Chlamydomonas reinhardtii provide excellent experimental systems for understanding iron metabolism at the subcellular level. Several paradigms in iron homeostasis have been established in this alga, including photosystem remodeling in the chloroplast and preferential retention of some pathways and key iron-dependent proteins in response to suboptimal iron supply. This review presents our current understanding of iron homeostasis in Chlamydomonas, with specific attention on characterized responses to changes in iron supply, like iron-deficiency. An overview of frequently used methods for the investigation of iron-responsive gene expression, physiology and metabolism is also provided, including preparation of media, the effect of cell size, cell density and strain choice on quantitative measurements and methods for the determination of metal content and assessing the effect of iron supply on photosynthetic performance. PMID:24032036

  13. Mychonastes desiccatus Brown sp. nova (Chlorococcales, Chlorophyta)--an intertidal alga forming achlorophyllous desiccation-resistant cysts

    NASA Technical Reports Server (NTRS)

    Margulis, L.; Hinkle, G.; McKhann, H.; Moynihan, B.

    1988-01-01

    An intertidal Chlorella-like alga Mychonastes desiccatus Brown sp. nova, capable of forming achlorophyllous desiccation-resistant cysts, has been grown in unialgal culture. This small alga was first isolated from a dried sample of a well-studied microbial mat. The mat, located at North Pond, Laguna Figueroa, San Quintin, Baja California, Mexico, is a vertically-stratified microbial community which forms laminated sediments. Morphology, pigment composition and G+C content are within the range typical for the genus Chlorella s. 1. Unlike other chlorellae, however, upon desiccation M. desiccatus forms an achlorophyllous, lipid-filled cyst (thick-walled resting stage) in which no plastid is evident. Rewetting leads to chloroplast differentiation, excystment and recovery of the fully green alga. During desiccation, sporopollenin is deposited within a thickening cell wall. Encystment cannot be induced by growth in the dark. The formation of desiccation-induced cysts allows the alga to survive frequent and intermittent periods of dryness. These chlorellae tolerate wide ranges of acidity and temperature; they both grow and form cysts in media in which sodium ions are replaced with potassium. Although the cysts tolerate crystalline salts, the cell grow optimally in concentrations corresponding from three-quarters to full-strength seawater.

  14. PSI-driven cyclic electron flow allows intertidal macro-algae Ulva sp. (Chlorophyta) to survive in desiccated conditions.

    PubMed

    Gao, Shan; Shen, Songdong; Wang, Guangce; Niu, Jianfeng; Lin, Apeng; Pan, Guanghua

    2011-05-01

    Ulva sp. (Chlorophyta) is a representative species of the intertidal macro-algae responsible for the green tides that occurred along the shores of Qingdao in 2008 and had detrimental effects on the preparation for the 2008 Beijing Olympic Games sailing competition. In view of its significance, we have investigated the photosynthetic performance of the photosystems and the changes in photosynthetic electron transport that occur during desiccation and rehydration of Ulva sp. The PSII activity in Ulva sp. declined gradually during the course of desiccation, which was reflected by the decreased maximum quantum yield and effective quantum yield, whereas the PSI activity fluctuated significantly. In contrast, the electron transport rates of PSII approached zero at severe levels of desiccation, but the electron transport of PSI, which still operated, could be suppressed effectively by a specific inhibitor. Furthermore, the electron transport of PSI during rehydration of desiccated thalli was recovered faster than that of PSII. All these results implied that the linear electron flow was abolished in desiccated Ulva sp., whereas the cyclic PSI activity was significantly elevated, was still active at severe levels of desiccation and could be restored faster than PSII activity. Based on these results, we concluded the PSI-driven cyclic electron flow might provide desiccation tolerance and additional flexibility for the cell physiology of Ulva sp. under desiccation conditions, which might be one of the most important factors that make Ulva sp. well suited to experience daily cycles of desiccation at low tide and rehydration at high tide. PMID:21471121

  15. Factors determining growth and vertical distribution of planktonic algae in extremely acidic mining lakes (pH 2.7)

    NASA Astrophysics Data System (ADS)

    Bissinger, Vera

    2003-04-01

    In this thesis, I investigated the factors influencing the growth and vertical distribution of planktonic algae in extremely acidic mining lakes (pH 2-3). In the focal study site, Lake 111 (pH 2.7; Lusatia, Germany), the chrysophyte, Ochromonas sp., dominates in the upper water strata and the chlorophyte, Chlamydomonas sp., in the deeper strata, forming a pronounced deep chlorophyll maximum (DCM). Inorganic carbon (IC) limitation influenced the phototrophic growth of Chlamydomonas sp. in the upper water strata. Conversely, in deeper strata, light limited its phototrophic growth. When compared with published data for algae from neutral lakes, Chlamydomonas sp. from Lake 111 exhibited a lower maximum growth rate, an enhanced compensation point and higher dark respiration rates, suggesting higher metabolic costs due to the extreme physico-chemical conditions. The photosynthetic performance of Chlamydomonas sp. decreased in high-light-adapted cells when IC limited. In addition, the minimal phosphorus (P) cell quota was suggestive of a higher P requirement under IC limitation. Subsequently, it was shown that Chlamydomonas sp. was a mixotroph, able to enhance its growth rate by taking up dissolved organic carbon (DOC) via osmotrophy. Therefore, it could survive in deeper water strata where DOC concentrations were higher and light limited. However, neither IC limitation, P availability nor in situ DOC concentrations (bottom-up control) could fully explain the vertical distribution of Chlamydomonas sp. in Lake 111. Conversely, when a novel approach was adopted, the grazing influence of the phagotrophic phototroph, Ochromonas sp., was found to exert top-down control on its prey (Chlamydomonas sp.) reducing prey abundance in the upper water strata. This, coupled with the fact that Chlamydomonas sp. uses DOC for growth, leads to a pronounced accumulation of Chlamydomonas sp. cells at depth; an apparent DCM. Therefore, grazing appears to be the main factor influencing the

  16. Sorption properties of algae Spirogyra sp. and their use for determination of heavy metal ions concentrations in surface water.

    PubMed

    Rajfur, Małgorzata; Kłos, Andrzej; Wacławek, Maria

    2010-11-01

    Kinetics of heavy-metal ions sorption by alga Spirogyra sp. was evaluated experimentally in the laboratory, using both the static and the dynamic approach. The metal ions--Mn(2+), Cu(2+), Zn(2+) and Cd(2+)--were sorbed from aqueous solutions of their salts. The static experiments showed that the sorption equilibria were attained in 30 min, with 90-95% of metal ions sorbed in first 10 min of each process. The sorption equilibria were approximated with the Langmuir isotherm model. The algae sorbed each heavy metal ions proportionally to the amount of this metal ions in solution. The experiments confirmed that after 30 min of exposition to contaminated water, the concentration of heavy metal ions in the algae, which initially contained small amounts of these metal ions, increased proportionally to the concentration of metal ions in solution. The presented results can be used for elaboration of a method for classification of surface waters that complies with the legal regulations. PMID:20435526

  17. The cell-wall glycoproteins of the green alga Scenedesmus obliquus. The predominant cell-wall polypeptide of Scenedesmus obliquus is related to the cell-wall glycoprotein gp3 of Chlamydomonas reinhardtii.

    PubMed

    Voigt, Jürgen; Stolarczyk, Adam; Zych, Maria; Malec, Przemysław; Burczyk, Jan

    2014-02-01

    The green alga Scenedesmus obliquus contains a multilayered cell wall, ultrastructurally similar to that of Chlamydomonas reinhardtii, although its proportion of hydroxyproline is considerably lower. Therefore, we have investigated the polypeptide composition of the insoluble and the chaotrope-soluble wall fractions of S. obliquus. The polypeptide pattern of the chaotrope-soluble wall fraction was strongly modified by chemical deglycosylation with anhydrous hydrogen fluoride (HF) in pyridine indicating that most of these polypeptides are glycosylated. Polypeptide constituents of the chaotrope-soluble cell-wall fraction with apparent molecular masses of 240, 270, 265, and 135 kDa cross-reacted with a polyclonal antibody raised against the 100 kDa deglycosylation product of the C. reinhardtii cell-wall glycoprotein GP3B. Chemical deglycosylation of the chaotrope-soluble wall fraction resulted in a 135 kDa major polypeptide and a 106 kDa minor component reacting with the same antibody. This antibody recognized specific peptide epitopes of GP3B. When the insoluble wall fraction of S. obliquus was treated with anhydrous HF/pyridine, three polypeptides with apparent molecular masses of 144, 135, and 65 kDa were solubilized, which also occured in the deglycosylated chaotrope-soluble wall fraction. These findings indicate that theses glycoproteins are cross-linked to the insoluble wall fraction via HF-sensitive bonds. PMID:24388513

  18. The Chlamydomonas heat stress response.

    PubMed

    Schroda, Michael; Hemme, Dorothea; Mühlhaus, Timo

    2015-05-01

    Heat waves occurring at increased frequency as a consequence of global warming jeopardize crop yield safety. One way to encounter this problem is to genetically engineer crop plants toward increased thermotolerance. To identify entry points for genetic engineering, a thorough understanding of how plant cells perceive heat stress and respond to it is required. Using the unicellular green alga Chlamydomonas reinhardtii as a model system to study the fundamental mechanisms of the plant heat stress response has several advantages. Most prominent among them is the suitability of Chlamydomonas for studying stress responses system-wide and in a time-resolved manner under controlled conditions. Here we review current knowledge on how heat is sensed and signaled to trigger temporally and functionally grouped sub-responses termed response elements to prevent damage and to maintain cellular homeostasis in plant cells. PMID:25754362

  19. Ascorbate accumulation during sulphur deprivation and its effects on photosystem II activity and H2 production of the green alga Chlamydomonas reinhardtii.

    PubMed

    Nagy, Valéria; Vidal-Meireles, André; Tengölics, Roland; Rákhely, Gábor; Garab, Győző; Kovács, László; Tóth, Szilvia Z

    2016-07-01

    In nature, H2 production in Chlamydomonas reinhardtii serves as a safety valve during the induction of photosynthesis in anoxia, and it prevents the over-reduction of the photosynthetic electron transport chain. Sulphur deprivation of C. reinhardtii also triggers a complex metabolic response resulting in the induction of various stress-related genes, down-regulation of photosynthesis, the establishment of anaerobiosis and expression of active hydrogenase. Photosystem II (PSII) plays dual role in H2 production because it supplies electrons but the evolved O2 inhibits the hydrogenase. Here, we show that upon sulphur deprivation, the ascorbate content in C. reinhardtii increases about 50-fold, reaching the mM range; at this concentration, ascorbate inactivates the Mn-cluster of PSII, and afterwards, it can donate electrons to tyrozin Z(+) at a slow rate. This stage is followed by donor-side-induced photoinhibition, leading to the loss of charge separation activity in PSII and reaction centre degradation. The time point at which maximum ascorbate concentration is reached in the cell is critical for the establishment of anaerobiosis and initiation of H2 production. We also show that ascorbate influenced H2 evolution via altering the photosynthetic electron transport rather than hydrogenase activity and starch degradation. PMID:26714836

  20. Effects of Dried Algae Schizochytrium Sp., A Rich Source of Docosahexaenoic Acid, on Growth, Fatty Acid Composition, and Sensory Quality of Channel Catfish Ictalurus Punctatus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A laboratory study was conducted to investigate the effect of supplementation of dried algae Schizochytrium sp., a rich source of 22:6 n-3, on growth, fatty acid composition, and sensory quality of channel catfish Ictalurus punctatus. Five isonitrogenous (28% crude protein) and isocaloric (2.78 kcal...

  1. Effectiveness and toxicity of a novel isolated actinomycete strain Streptomyces sp. JS01 on a harmful alga Phaeocystis globosa.

    PubMed

    Zhang, Huajun; Zhang, Su; Peng, Yun; Li, Yi; Cai, Guanjing; Chen, Zhangran; Zheng, Wei; Tian, Yun; Xu, Hong; Zheng, Tianling

    2015-06-01

    An aquatic actinomycete capable of eliminating the brown tide causing marine alga Phaeocystis globosa was isolated from the surface sea water and the isolate named JS01 was characterized as Streptomyces on the basis of its 16S rRNA gene sequence. The supernatant of JS01 could lyse algal cells, implying that JS01 produced a latent alga-lytic compound. Considering this algicidal activity and the response of the algal cells, Chlorophyll a fluorescence decreased significantly in P. globosa in response to the JS01 supernatant when analyzed with flow cytometry. The algal cells experienced cell shrinkage and plasmolysis before disintegration after 72 h of treatment. The released algicide(s) were heat-tolerant, except above 121 °C, and fluctuation in pH variations; even so, algicidal activity was also over 60 %. The maximum toxicity of JS01 was on the seventh day of culture, and the relative luminosity was 0.49 at that time when detected by luminous bacteria Vibrio fischeri. These results indicated that the Streptomyces sp. JS01 could function as a potential controller of Phaeocystis globosa blooms. PMID:25638354

  2. Assessing bio-available silver released from silver nanoparticles embedded in silica layers using the green algae Chlamydomonas reinhardtii as bio-sensors.

    PubMed

    Pugliara, Alessandro; Makasheva, Kremena; Despax, Bernard; Bayle, Maxime; Carles, Robert; Benzo, Patrizio; BenAssayag, Gérard; Pécassou, Béatrice; Sancho, Maria Carmen; Navarro, Enrique; Echegoyen, Yolanda; Bonafos, Caroline

    2016-09-15

    Silver nanoparticles (AgNPs) because of their strong antibacterial activity are widely used in health-care sector and industrial applications. Their huge surface-volume ratio enhances the silver release compared to the bulk material, leading to an increased toxicity for microorganisms sensitive to this element. This work presents an assessment of the toxic effect on algal photosynthesis due to small (size <20nm) AgNPs embedded in silica layers. Two physical approaches were originally used to elaborate the nanocomposite structures: (i) low energy ion beam synthesis and (ii) combined silver sputtering and plasma polymerization. These techniques allow elaboration of a single layer of AgNPs embedded in silica films at defined nanometer distances (from 0 to 7nm) beneath the free surface. The structural and optical properties of the nanostructures were studied by transmission electron microscopy and optical reflectance. The silver release from the nanostructures after 20h of immersion in buffered water was measured by inductively coupled plasma mass spectrometry and ranges between 0.02 and 0.49μM. The short-term toxicity of Ag to photosynthesis of Chlamydomonas reinhardtii was assessed by fluorometry. The obtained results show that embedding AgNPs reduces the interactions with the buffered water free media, protecting the AgNPs from fast oxidation. The release of bio-available silver (impacting on the algal photosynthesis) is controlled by the depth at which AgNPs are located for a given host matrix. This provides a procedure to tailor the toxicity of nanocomposites containing AgNPs. PMID:26953143

  3. Acclimation of Antarctic Chlamydomonas to the sea-ice environment: a transcriptomic analysis.

    PubMed

    Liu, Chenlin; Wang, Xiuliang; Wang, Xingna; Sun, Chengjun

    2016-07-01

    The Antarctic green alga Chlamydomonas sp. ICE-L was isolated from sea ice. As a psychrophilic microalga, it can tolerate the environmental stress in the sea-ice brine, such as freezing temperature and high salinity. We performed a transcriptome analysis to identify freezing stress responding genes and explore the extreme environmental acclimation-related strategies. Here, we show that many genes in ICE-L transcriptome that encoding PUFA synthesis enzymes, molecular chaperon proteins, and cell membrane transport proteins have high similarity to the gens from Antarctic bacteria. These ICE-L genes are supposed to be acquired through horizontal gene transfer from its symbiotic microbes in the sea-ice brine. The presence of these genes in both sea-ice microalgae and bacteria indicated the biological processes they involved in are possibly contributing to ICE-L success in sea ice. In addition, the biological pathways were compared between ICE-L and its closely related sister species, Chlamydomonas reinhardtii and Volvox carteri. In ICE-L transcripome, many sequences homologous to the plant or bacteria proteins in the post-transcriptional, post-translational modification, and signal-transduction KEGG pathways, are absent in the nonpsychrophilic green algae. These complex structural components might imply enhanced stress adaptation capacity. At last, differential gene expression analysis at the transcriptome level of ICE-L indicated that genes that associated with post-translational modification, lipid metabolism, and nitrogen metabolism are responding to the freezing treatment. In conclusion, the transcriptome of Chlamydomonas sp. ICE-L is very useful for exploring the mutualistic interaction between microalgae and bacteria in sea ice; and discovering the specific genes and metabolism pathways responding to the freezing acclimation in psychrophilic microalgae. PMID:27161450

  4. Assembly of the Light-Harvesting Chlorophyll Antenna in the Green Alga Chlamydomonas reinhardtii Requires Expression of the TLA2-CpFTSY Gene1[C][W][OA

    PubMed Central

    Kirst, Henning; García-Cerdán, Jose Gines; Zurbriggen, Andreas; Melis, Anastasios

    2012-01-01

    The truncated light-harvesting antenna2 (tla2) mutant of Chlamydomonas reinhardtii showed a lighter-green phenotype, had a lower chlorophyll (Chl) per-cell content, and higher Chl a/b ratio than corresponding wild-type strains. Physiological analyses revealed a higher intensity for the saturation of photosynthesis and greater Pmax values in the tla2 mutant than in the wild type. Biochemical analyses showed that the tla2 strain was deficient in the Chl a-b light-harvesting complex, and had a Chl antenna size of the photosystems that was only about 65% of that in the wild type. Molecular and genetic analyses showed a single plasmid insertion in the tla2 strain, causing a chromosomal DNA rearrangement and deletion/disruption of five nuclear genes. The TLA2 gene, causing the tla2 phenotype, was cloned by mapping the insertion site and upon complementation with each of the genes that were deleted. Successful complementation was achieved with the C. reinhardtii TLA2-CpFTSY gene, whose occurrence and function in green microalgae has not hitherto been investigated. Functional analysis showed that the nuclear-encoded and chloroplast-localized CrCpFTSY protein specifically operates in the assembly of the peripheral components of the Chl a-b light-harvesting antenna. In higher plants, a cpftsy null mutation inhibits assembly of both the light-harvesting complex and photosystem complexes, thus resulting in a seedling-lethal phenotype. The work shows that cpftsy deletion in green algae, but not in higher plants, can be employed to generate tla mutants. The latter exhibit improved solar energy conversion efficiency and photosynthetic productivity under mass culture and bright sunlight conditions. PMID:22114096

  5. Hydrogen photoproduction in green algae Chlamydomonas reinhardtii sustainable over 2 weeks with the original cell culture without supply of fresh cells nor exchange of the whole culture medium.

    PubMed

    Yagi, Takafumi; Yamashita, Kyohei; Okada, Norihide; Isono, Takumi; Momose, Daisuke; Mineki, Shigeru; Tokunaga, Eiji

    2016-07-01

    Unicellular green algae Chlamydomonas reinhardtii are known to make hydrogen photoproduction under the anaerobic condition with water molecules as the hydrogen source. Since the hydrogen photoproduction occurs for a cell to circumvent crisis of its survival, it is only temporary. It is a challenge to realize persistent hydrogen production because the cells must withstand stressful conditions to survive with alternation of generations in the cell culture. In this paper, we have found a simple and cost-effective method to sustain the hydrogen production over 14 days in the original culture, without supply of fresh cells nor exchange of the culture medium. This is achieved for the cells under hydrogen production in a sulfur-deprived culture solution on the {anaerobic, intense light} condition in a desiccator, by periodically providing a short period of the recovery time (2 h) with a small amount of TAP(+S) supplied outside of the desiccator. As this operation is repeated, the response time of transition into hydrogen production (preparation time) is shortened and the rate of hydrogen production (build up time) is increased. The optimum states of these properties favorable to the hydrogen production are attained in a few days and stably sustained for more than 10 days. Since generations are alternated during this consecutive hydrogen production experiment, it is suggested that the improved hydrogen production properties are inherited to next generations without genetic mutation. The properties are reset only when the cells are placed on the {sulfur-sufficient, aerobic, moderate light} conditions for a long time (more than 1 day at least). PMID:27083446

  6. The basal bodies of Chlamydomonas reinhardtii.

    PubMed

    Dutcher, Susan K; O'Toole, Eileen T

    2016-01-01

    The unicellular green alga, Chlamydomonas reinhardtii, is a biflagellated cell that can swim or glide. C. reinhardtii cells are amenable to genetic, biochemical, proteomic, and microscopic analysis of its basal bodies. The basal bodies contain triplet microtubules and a well-ordered transition zone. Both the mother and daughter basal bodies assemble flagella. Many of the proteins found in other basal body-containing organisms are present in the Chlamydomonas genome, and mutants in these genes affect the assembly of basal bodies. Electron microscopic analysis shows that basal body duplication is site-specific and this may be important for the proper duplication and spatial organization of these organelles. Chlamydomonas is an excellent model for the study of basal bodies as well as the transition zone. PMID:27252853

  7. Preparation and Evaluation of the Chelating Nanocomposite Fabricated with Marine Algae Schizochytrium sp. Protein Hydrolysate and Calcium.

    PubMed

    Lin, Jiaping; Cai, Xixi; Tang, Mengru; Wang, Shaoyun

    2015-11-11

    Marine algae have been becoming a popular research topic because of their biological implication. The algae peptide-based metal-chelating complex was investigated in this study. Schizochytrium sp. protein hydrolysate (SPH) possessing high Ca-binding capacity was prepared through stepwise enzymatic hydrolysis to a degree of hydrolysis of 22.46%. The nanocomposites of SPH chelated with calcium ions were fabricated in aqueous solution at pH 6 and 30 °C for 20 min, with the ratio of SPH to calcium 3:1 (w/w). The size distribution showed that the nanocomposite had compact structure with a radius of 68.16 ± 0.50 nm. SPH was rich in acidic amino acids, accounting for 33.55%, which are liable to bind with calcium ions. The molecular mass distribution demonstrated that the molecular mass of SPH was principally concentrated at 180-2000 Da. UV scanning spectroscopy and Fourier transform infrared spectroscopy suggested that the primary sites of calcium-binding corresponded to the carboxyl groups, carbonyl groups, and amino groups of SPH. The results of fluorescent spectroscopy, size distribution, atomic force microscope, and (1)H nuclear magnetic resonance spectroscopy suggested that calcium ions chelated with SPH would cause intramolecular and intermolecular folding and aggregating. The SPH-calcium chelate exerted remarkable stability and absorbability under either acidic or basic conditions, which was in favor of calcium absorption in the gastrointestinal tracts of humans. The investigation suggests that SPH-calcium chelate has the potential prospect to be utilized as a nutraceutical supplement to improve bone health in the human body. PMID:26499390

  8. Distinctive Architecture of the Chloroplast Genome in the Chlorodendrophycean Green Algae Scherffelia dubia and Tetraselmis sp. CCMP 881.

    PubMed

    Turmel, Monique; de Cambiaire, Jean-Charles; Otis, Christian; Lemieux, Claude

    2016-01-01

    The Chlorodendrophyceae is a small class of green algae belonging to the core Chlorophyta, an assemblage that also comprises the Pedinophyceae, Trebouxiophyceae, Ulvophyceae and Chlorophyceae. Here we describe for the first time the chloroplast genomes of chlorodendrophycean algae (Scherffelia dubia, 137,161 bp; Tetraselmis sp. CCMP 881, 100,264 bp). Characterized by a very small single-copy (SSC) region devoid of any gene and an unusually large inverted repeat (IR), the quadripartite structures of the Scherffelia and Tetraselmis genomes are unique among all core chlorophytes examined thus far. The lack of genes in the SSC region is offset by the rich and atypical gene complement of the IR, which includes genes from the SSC and large single-copy regions of prasinophyte and streptophyte chloroplast genomes having retained an ancestral quadripartite structure. Remarkably, seven of the atypical IR-encoded genes have also been observed in the IRs of pedinophycean and trebouxiophycean chloroplast genomes, suggesting that they were already present in the IR of the common ancestor of all core chlorophytes. Considering that the relationships among the main lineages of the core Chlorophyta are still unresolved, we evaluated the impact of including the Chlorodendrophyceae in chloroplast phylogenomic analyses. The trees we inferred using data sets of 79 and 108 genes from 71 chlorophytes indicate that the Chlorodendrophyceae is a deep-diverging lineage of the core Chlorophyta, although the placement of this class relative to the Pedinophyceae remains ambiguous. Interestingly, some of our phylogenomic trees together with our comparative analysis of gene order data support the monophyly of the Trebouxiophyceae, thus offering further evidence that the previously observed affiliation between the Chlorellales and Pedinophyceae is the result of systematic errors in phylogenetic reconstruction. PMID:26849226

  9. Distinctive Architecture of the Chloroplast Genome in the Chlorodendrophycean Green Algae Scherffelia dubia and Tetraselmis sp. CCMP 881

    PubMed Central

    Turmel, Monique; de Cambiaire, Jean-Charles; Otis, Christian; Lemieux, Claude

    2016-01-01

    The Chlorodendrophyceae is a small class of green algae belonging to the core Chlorophyta, an assemblage that also comprises the Pedinophyceae, Trebouxiophyceae, Ulvophyceae and Chlorophyceae. Here we describe for the first time the chloroplast genomes of chlorodendrophycean algae (Scherffelia dubia, 137,161 bp; Tetraselmis sp. CCMP 881, 100,264 bp). Characterized by a very small single-copy (SSC) region devoid of any gene and an unusually large inverted repeat (IR), the quadripartite structures of the Scherffelia and Tetraselmis genomes are unique among all core chlorophytes examined thus far. The lack of genes in the SSC region is offset by the rich and atypical gene complement of the IR, which includes genes from the SSC and large single-copy regions of prasinophyte and streptophyte chloroplast genomes having retained an ancestral quadripartite structure. Remarkably, seven of the atypical IR-encoded genes have also been observed in the IRs of pedinophycean and trebouxiophycean chloroplast genomes, suggesting that they were already present in the IR of the common ancestor of all core chlorophytes. Considering that the relationships among the main lineages of the core Chlorophyta are still unresolved, we evaluated the impact of including the Chlorodendrophyceae in chloroplast phylogenomic analyses. The trees we inferred using data sets of 79 and 108 genes from 71 chlorophytes indicate that the Chlorodendrophyceae is a deep-diverging lineage of the core Chlorophyta, although the placement of this class relative to the Pedinophyceae remains ambiguous. Interestingly, some of our phylogenomic trees together with our comparative analysis of gene order data support the monophyly of the Trebouxiophyceae, thus offering further evidence that the previously observed affiliation between the Chlorellales and Pedinophyceae is the result of systematic errors in phylogenetic reconstruction. PMID:26849226

  10. Combined biocidal action of silver nanoparticles and ions against Chlorococcales (Scenedesmus quadricauda, Chlorella vulgaris) and filamentous algae (Klebsormidium sp.).

    PubMed

    Zouzelka, Radek; Cihakova, Pavlina; Rihova Ambrozova, Jana; Rathousky, Jiri

    2016-05-01

    Despite the extensive research, the mechanism of the antimicrobial and biocidal performance of silver nanoparticles has not been unequivocally elucidated yet. Our study was aimed at the investigation of the ability of silver nanoparticles to suppress the growth of three types of algae colonizing the wetted surfaces or submerged objects and the mechanism of their action. Silver nanoparticles exhibited a substantial toxicity towards Chlorococcales Scenedesmus quadricauda, Chlorella vulgaris, and filamentous algae Klebsormidium sp., which correlated with their particle size. The particles had very good stability against agglomeration even in the presence of multivalent cations. The concentration of silver ions in equilibrium with nanoparticles markedly depended on the particle size, achieving about 6 % and as low as about 0.1 % or even less for the particles 5 nm in size and for larger ones (40-70 nm), respectively. Even very limited proportion of small particles together with larger ones could substantially increase concentration of Ag ions in solution. The highest toxicity was found for the 5-nm-sized particles, being the smallest ones in this study. Their toxicity was even higher than that of silver ions at the same silver concentration. When compared as a function of the Ag(+) concentration in equilibrium with 5-nm particles, the toxicity of ions was at least 17 times higher than that obtained by dissolving silver nitrite (if not taking into account the effect of nanoparticles themselves). The mechanism of the toxicity of silver nanoparticles was found complex with an important role played by the adsorption of silver nanoparticles and the ions released from the particles on the cell surface. This mechanism could be described as some sort of synergy between nanoparticles and ions. While our study clearly showed the presence of this synergy, its detailed explanation is experimentally highly demanding, requiring a close cooperation between materials scientists

  11. Nitrogen and phosphorus removal from municipal wastewater by the green alga Chlorella sp.

    PubMed

    Wang, Changfu; Yu, Xiaoqing; Lv, Hong; Yang, Jun

    2013-04-01

    The potential of microalgae as a source of renewable energy based on wastewater has received increasing interest worldwide in recent decades. A freshwater microalga Chlorella sp. was investigated for its ability to remove both nitrogen and phosphorus from influent and effluent wastewaters which were diluted in four different proportions (namely, 100%, 75%, 50% and 25%). Chlorella sp. grew fastest under 50% influent and effluent wastewaters culture conditions, and showed an maximum cell density (4.25 x 10(9) ind 1(-1) for influent wastewater and 3.54 x 109 ind l(-1) for effluent wastewater), indicating the levels of nitrogen and phosphorus greatly influenced algal growth. High removal efficiency for total nitrogen (17.04-58.85%) and total phosphorus (62.43-97.08%) was achieved. Further, more than 83% NH4-N in 75%, 50%, 25% influent wastewater, 88% NOx-N in effluent wastewater and 90% PO4-P in all treatments were eliminated after 24 days of incubation. Chlorella sp. grew well when PO4-P concentration was very low, indicating that this might be not the limiting factor to algal growth. Our results suggest the potential importance of integrating nutrient removal from wastewater by microalgae cultivation as biofuel production feedstock. PMID:24620613

  12. Genome of the halotolerant green alga Picochlorum sp. reveals strategies for thriving under fluctuating environmental conditions.

    PubMed

    Foflonker, Fatima; Price, Dana C; Qiu, Huan; Palenik, Brian; Wang, Shuyi; Bhattacharya, Debashish

    2015-02-01

    An expected outcome of climate change is intensification of the global water cycle, which magnifies surface water fluxes, and consequently alters salinity patterns. It is therefore important to understand the adaptations and limits of microalgae to survive changing salinities. To this end, we sequenced the 13.5 Mbp genome of the halotolerant green alga Picochlorum SENEW3 (SE3) that was isolated from a brackish water pond subject to large seasonal salinity fluctuations. Picochlorum SE3 encodes 7367 genes, making it one of the smallest and most gene dense eukaryotic genomes known. Comparison with the pico-prasinophyte Ostreococcus tauri, a species with a limited range of salt tolerance, reveals the enrichment of transporters putatively involved in the salt stress response in Picochlorum SE3. Analysis of cultures and the protein complement highlight the metabolic flexibility of Picochlorum SE3 that encodes genes involved in urea metabolism, acetate assimilation and fermentation, acetoin production and glucose uptake, many of which form functional gene clusters. Twenty-four cases of horizontal gene transfer from bacterial sources were found in Picochlorum SE3 with these genes involved in stress adaptation including osmolyte production and growth promotion. Our results identify Picochlorum SE3 as a model for understanding microalgal adaptation to stressful, fluctuating environments. PMID:24965277

  13. Mameliella phaeodactyli sp. nov., a member of the family Rhodobacteraceae isolated from the marine algae Phaeodactylum tricornutum.

    PubMed

    Chen, Zhangran; Zhang, Jingyan; Lei, Xueqian; Lai, Qiliang; Yang, Luxi; Zhang, Huajun; Li, Yi; Zheng, Wei; Tian, Yun; Yu, Zhiming; Xu, Hong; Zheng, Tianling

    2015-05-01

    A novel Gram-staining-negative, aerobic, rod-shaped, non-motile, yellow bacterium designated strain KD53(T), was isolated from a culture of the alga Phaeodactylum tricornutum from Xiamen, Fujian Province, China. 16S rRNA gene sequence comparison showed that strain KD53(T) was a member of the Roseobacter clade within the family Rhodobacteraceae , forming a distinct lineage with species of the genus Mameliella . The 16S rRNA gene sequence similarities between strain KD53(T) and other strains examined were all less than 97.0%. Strain KD53(T) was found to grow optimally at 28 °C, at pH 7.5-8.0 and in the presence of 3% (w/v) NaCl. The dominant fatty acids of strain KD53(T) were C18 : 1ω6c and/or C18 : 1ω7c, C18 : 0 and C16 : 0. The major polar lipids were phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol. The DNA G+C content was 65 mol% and the major respiratory quinone was ubiquinone 10 (Q-10). On the basis of phenotypic data and phylogenetic inference, strain KD53(T) represents a novel member of the genus Mameliella , then the name Mameliella phaeodactyli sp. nov. is proposed. The type strain is KD53(T) ( =MCCC 1K00273(T) =KCTC 42178(T)). PMID:25716952

  14. Light stress and photoprotection in Chlamydomonas reinhardtii.

    PubMed

    Erickson, Erika; Wakao, Setsuko; Niyogi, Krishna K

    2015-05-01

    Plants and algae require light for photosynthesis, but absorption of too much light can lead to photo-oxidative damage to the photosynthetic apparatus and sustained decreases in the efficiency and rate of photosynthesis (photoinhibition). Light stress can adversely affect growth and viability, necessitating that photosynthetic organisms acclimate to different environmental conditions in order to alleviate the detrimental effects of excess light. The model unicellular green alga, Chlamydomonas reinhardtii, employs diverse strategies of regulation and photoprotection to avoid, minimize, and repair photo-oxidative damage in stressful light conditions, allowing for acclimation to different and changing environments. PMID:25758978

  15. Phaeodactylibacter xiamenensis gen. nov., sp. nov., a member of the family Saprospiraceae isolated from the marine alga Phaeodactylum tricornutum.

    PubMed

    Chen, Zhangran; Lei, Xueqian; Lai, Qiliang; Li, Yi; Zhang, Bangzhou; Zhang, Jingyan; Zhang, Huajun; Yang, Luxi; Zheng, Wei; Tian, Yun; Yu, Zhiming; Xu, Hong; Zheng, Tianling

    2014-10-01

    A novel Gram-staining-negative, aerobic, rod-shaped, non-motile, reddish-orange and chemoheterotrophic bacteria, designated strain KD52(T), was isolated from a culture of the alga Phaeodactylum tricornutum from Xiamen, Fujian Province, China. 16S rRNA gene sequence comparison showed that strain KD52(T) was a member of the family Saprospiraceae, forming a distinct lineage with 'Portibacter lacus' KCTC 23747. The 16S rRNA gene sequence similarity between strain KD52(T) and the type strains of species of the family Saprospiraceae ranged from 86% to 89%. Growth occurred at 20-37 °C (optimum, 28 °C), in the presence of 1-9% (w/v) NaCl (optimum, 2.5%) and at pH 5-8.5 (optimum, pH 6.0). The dominant fatty acids (>10%) of strain KD52(T) were iso-C15:0 (33.1%), iso-C15:1 G (14.8%) and summed feature 3 (comprising C16:1ω7c and/or C16:1ω6c, 13.8%). The major polar lipids were diphosphatidylglycerol, three unidentified phospholipids, four unknown lipids and one unidentified aminolipid. The DNA G+C content was 51 mol% and the major respiratory quinone was menaquinone-7 (MK-7). On the basis of phenotypic data and phylogenetic inference, strain KD52(T) represents a novel species of a new genus, for which the name Phaeodactylibacter xiamenensis gen. nov., sp. nov., is proposed. The type strain is KD52(T) ( = MCCC 1F01213(T) = KCTC 32575(T)). PMID:25052393

  16. Evaluation of an oil-producing green alga Chlorella sp. C2 for biological DeNOx of industrial flue gases.

    PubMed

    Zhang, Xin; Chen, Hui; Chen, Weixian; Qiao, Yaqin; He, Chenliu; Wang, Qiang

    2014-09-01

    NOx, a significant portion of fossil fuel flue gases, are among the most serious environmental issues in the world and must be removed in an additional costly gas treatment step. This study evaluated the growth of the green alga Chlorella sp. C2 under a nitrite-simulated NOx environment and the removal rates of actual flue gas fixed salts (FGFSs) from Sinopec's Shijiazhuang refinery along with lipid production. The results showed that nitrite levels lower than 176.5 mM had no significant adverse effects on the cell growth and photosynthesis of Chlorella sp. C2, demonstrating that this green alga could utilize nitrite and NOx as a nitrogen source. High concentrations of nitrite (88.25-176.5 mM) also resulted in the accumulation of neutral lipids. A 60% nitrite removal efficiency was obtained together with the production of 33% algae lipids when cultured with FGFS. Notably, the presence of nitrate in the FGFS medium significantly enhanced the nitrite removal capability, biomass and lipid production. Thus, this study may provide a new insight into the economically viable application of microalgae in the synergistic combination of biological DeNOx of industrial flue gases and biodiesel production. PMID:25105531

  17. Swimming of Chlamydomonas reinhardtii in weakly elastic fluids

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Gollub, Jerry; Arratia, Paulo

    2012-11-01

    The swimming behavior of the algae Chlamydomonas reinhardtii in weakly elastic fluids is investigated in experiments using microscopy and tracking methods. The effects of fluid viscosity and elasticity on the swimming speed, flagellar shape, beating frequency, and efficiency are examined. Here, the fluid viscosity is varied using water and sucrose solutions, while fluid elasticity is introduced by adding flexible polymer CMC (carboxymethyl cellulose) to the buffer solution. Swimming experiments are performed in a thin-film apparatus equipped with a microscope and high-speed camera. We find that even small amounts of fluid elasticity can have a significant effect on the swimming kinematics and dynamics of Chlamydomonas because of the relatively high beating frequency of its flagella (50-60 Hz). For example, the Chlamydomonas swimming speed is hindered by fluid elasticity compared to Newtonian fluids. In addition, the algae swimming speed decreases as the fluid elasticity is increased. This research is supported by the NSF through grant DMR-1104705.

  18. Measurements of photorespiration in some microscopic algae.

    PubMed

    Cheng, K H; Colman, B

    1974-09-01

    The rate of photorespiration in three green algae and four blue-green algae was determined by the measurement of the rate of loss of photosynthetically fixed (14)CO2 in light in CO2-free air at 25°. In all algae studied, CO2 evolution in light was considerably less than that in the dark, except for Chlamydomonas reinhardii which released slightly more CO2 in the light. Raising the temperature to 35° had little effect on the ratio of light to dark (14)CO2 release. Blue-green algae showed the lowest photorespiration rate of the algae studied. PMID:24458883

  19. Identity and physiology of a new psychrophilic eukaryotic green alga, Chlorella sp., strain BI, isolated from a transitory pond near Bratina Island, Antarctica.

    PubMed

    Morgan-Kiss, Rachael M; Ivanov, Alexander G; Modla, Shannon; Czymmek, Kirk; Hüner, Norman P A; Priscu, John C; Lisle, John T; Hanson, Thomas E

    2008-09-01

    Permanently low temperature environments are one of the most abundant microbial habitats on earth. As in most ecosystems, photosynthetic organisms drive primary production in low temperature food webs. Many of these phototrophic microorganisms are psychrophilic; however, functioning of the photosynthetic processes of these enigmatic psychrophiles (the "photopsychrophiles") in cold environments is not well understood. Here we describe a new chlorophyte isolated from a low temperature pond, on the Ross Ice Shelf near Bratina Island, Antarctica. Phylogenetic and morphological analyses place this strain in the Chlorella clade, and we have named this new chlorophyte Chlorella BI. Chlorella BI is a psychrophilic species, exhibiting optimum temperature for growth at around 10 degrees C. However, psychrophily in the Antarctic Chlorella was not linked to high levels of membrane-associated poly-unsaturated fatty acids. Unlike the model Antarctic lake alga, Chlamydomonas raudensis UWO241, Chlorella BI has retained the ability for dynamic short term adjustment of light energy distribution between photosystem II (PS II) and photosystem I (PS I). In addition, Chlorella BI can grow under a variety of trophic modes, including heterotrophic growth in the dark. Thus, this newly isolated photopsychrophile has retained a higher versatility in response to environmental change than other well studied cold-adapted chlorophytes. PMID:18661097

  20. Identity and physiology of a new psychrophilic eukaryotic green alga, Chlorella sp., strain BI, isolated from a transitory pond near Bratina Island, Antarctica

    USGS Publications Warehouse

    Morgan-Kiss, R. M.; Ivanov, A.G.; Modla, S.; Czymmek, K.; Huner, N.P.A.; Priscu, J.C.; Lisle, J.T.; Hanson, T.E.

    2008-01-01

    Permanently low temperature environments are one of the most abundant microbial habitats on earth. As in most ecosystems, photosynthetic organisms drive primary production in low temperature food webs. Many of these phototrophic microorganisms are psychrophilic; however, functioning of the photosynthetic processes of these enigmatic psychrophiles (the 'photopsychrophiles') in cold environments is not well understood. Here we describe a new chlorophyte isolated from a low temperature pond, on the Ross Ice Shelf near Bratina Island, Antarctica. Phylogenetic and morphological analyses place this strain in the Chlorella clade, and we have named this new chlorophyte Chlorella BI. Chlorella BI is a psychrophilic species, exhibiting optimum temperature for growth at around 10??C. However, psychrophily in the Antarctic Chlorella was not linked to high levels of membrane-associated poly-unsaturated fatty acids. Unlike the model Antarctic lake alga, Chlamydomonas raudensis UWO241, Chlorella BI has retained the ability for dynamic short term adjustment of light energy distribution between photosystem II (PS II) and photosystem I (PS I). In addition, Chlorella BI can grow under a variety of trophic modes, including heterotrophic growth in the dark. Thus, this newly isolated photopsychrophile has retained a higher versatility in response to environmental change than other well studied cold-adapted chlorophytes. ?? 2008 Springer.

  1. Toxic potential of iron oxide, CdS/Ag₂S composite, CdS and Ag₂S NPs on a fresh water alga Mougeotia sp.

    PubMed

    Jagadeesh, E; Khan, Behlol; Chandran, Preethy; Khan, S Sudheer

    2015-01-01

    Nanoparticles (NPs) are being used in many industries ranging from medical, textile, automobile, consumer products, etc. This may increase the probability of their (NPs) release into the environment and fresh water ecosystems. The present study focuses on testing the potential effect of iron oxide, nanocomposite of cadmium sulfide and silver sulfide, cadmium sulfide and silver sulfide nanoparticles (NPs) on a fresh water alga Mougeotia sp. as the model organism. The alga was treated with different concentrations of NPs (0.1-25 mg/L). The NPs exposure caused lipid peroxidation and ROS production, and suppressed the antioxidant defense system such as catalase, glutathione reductase, and superoxide dismutase. Adsorption of NPs on algal surface and membrane damage were confirmed through microscopic evaluation and increase in protein content in extracellular medium. The present investigation pointed out the ecological implications of NPs. The study warrants the need for regulatory agencies to monitor and regulate the use of NPs. PMID:25465759

  2. Alterations in seawater pH and CO 2 affect calcification and photosynthesis in the tropical coralline alga, Hydrolithon sp. (Rhodophyta)

    NASA Astrophysics Data System (ADS)

    Semesi, I. Sware; Kangwe, Juma; Björk, Mats

    2009-09-01

    Calcification in the marine environment is the basis for the accretion of carbonate in structures such as coral reefs, algal ridges and carbonate sands. Among the organisms responsible for such calcification are the Corallinaceae (Rhodophyta), recognised as major contributors to the process world-wide. Hydrolithon sp. is a coralline alga that often forms rhodoliths in the Western Indian Ocean. In Zanzibar, it is commonly found in shallow lagoons, where it often grows within seagrass beds and/or surrounded by green algae such as Ulva sp. Since seagrasses in Zanzibar have recently been shown to raise the pH of the surrounding seawater during the day, and since calcification rates are sensitive to pH, which changes the saturation state of calcium carbonate, we measured the effects of pH on photosynthetic and calcification rates of this alga. It was found that pH had significant effects on both calcification and photosynthesis. While increased pH enhanced calcification rates both in the light and in the dark at pH >8.6, photosynthetic rates decreased. On the other hand, an increase in dissolved CO 2 concentration to ˜26 μmol kg -1 (by bubbling with air containing 0.9 mbar CO 2) caused a decrease in seawater pH which resulted in 20% less calcification after 5 days of exposure, while enhancing photosynthetic rates by 13%. The ecological implications of these findings is that photosynthetically driven changes in water chemistry by surrounding plants can affect calcification rates of coralline algae, as may future ocean acidification resulting from elevated atmospheric CO 2.

  3. Characterization and optimization of hydrogen production by a salt water blue-green alga Oscillatoria sp. Miami BG 7. II - Use of immobilization for enhancement of hydrogen production

    NASA Technical Reports Server (NTRS)

    Phlips, E. J.; Mitsui, A.

    1986-01-01

    The technique of cellular immobilization was applied to the process of hydrogen photoproduction of nonheterocystous, filamentous marine blue-green alga, Oscillatoria sp. Miami BG 7. Immobilization with agar significantly improved the rate and longevity of hydrogen production, compared to free cell suspensions. Rates of H2 production in excess of 13 microliters H2 mg dry/wt h were observed and hydrogen production was sustained for three weeks. Immobilization also provided some stabilization to environmental variability and was adaptable to outdoor light conditions. In general, immobilization provides significant advantages for the production and maintenance of hydrogen photoproduction for this strain.

  4. Clocks in algae.

    PubMed

    Noordally, Zeenat B; Millar, Andrew J

    2015-01-20

    As major contributors to global oxygen levels and producers of fatty acids, carotenoids, sterols, and phycocolloids, algae have significant ecological and commercial roles. Early algal models have contributed much to our understanding of circadian clocks at physiological and biochemical levels. The genetic and molecular approaches that identified clock components in other taxa have not been as widely applied to algae. We review results from seven species: the chlorophytes Chlamydomonas reinhardtii, Ostreococcus tauri, and Acetabularia spp.; the dinoflagellates Lingulodinium polyedrum and Symbiodinium spp.; the euglenozoa Euglena gracilis; and the red alga Cyanidioschyzon merolae. The relative simplicity, experimental tractability, and ecological and evolutionary diversity of algal systems may now make them particularly useful in integrating quantitative data from "omic" technologies (e.g., genomics, transcriptomics, metabolomics, and proteomics) with computational and mathematical methods. PMID:25379817

  5. Aurearenophyceae classis nova, a new class of Heterokontophyta based on a new marine unicellular alga Aurearena cruciata gen. et sp. nov. inhabiting sandy beaches.

    PubMed

    Kai, Atsushi; Yoshii, Yukie; Nakayama, Takeshi; Inouye, Isao

    2008-07-01

    A new heterokontophyte alga, Aurearena cruciata gen. et sp. nov., was isolated from sandy beaches in Japan. Isolates were characterized by light and electron microscopy, spectroscopy of pigment composition, and molecular phylogenetic analyses using 18S rDNA and rbcL. The alga usually possessed a cell wall but also retained two heterokont flagella beneath the cell wall. Each walled cell first produced only a single flagellate cell that subsequently divided into two flagellate cells. Electron-opaque vesicles, possibly associated with cell wall formation, were observed beneath the cell membrane. The chloroplast consisted of two compartments, each enclosed by a chloroplast envelope and the inner membrane of the chloroplast endoplasmic reticulum; these two compartments were surrounded by a common outer membrane of chloroplast endoplasmic reticulum. Molecular phylogenetic trees suggested that this alga was a new and independent member of the clade that included the Phaeophyceae and Xanthophyceae (PX clade). A new class, Aurearenophyceae classis nova was proposed for A. cruciata. PMID:18358776

  6. Chlamydomonas Flavodiiron Proteins Facilitate Acclimation to Anoxia During Sulfur Deprivation

    PubMed Central

    Jokel, Martina; Kosourov, Sergey; Battchikova, Natalia; Tsygankov, Anatoly A.; Aro, Eva Mari; Allahverdiyeva, Yagut

    2015-01-01

    The flavodiiron proteins (FDPs) are involved in the detoxification of oxidative compounds, such as nitric oxide (NO) or O2 in Archaea and Bacteria. In cyanobacteria, the FDPs Flv1 and Flv3 are essential in the light-dependent reduction of O2 downstream of PSI. Phylogenetic analysis revealed that two genes (flvA and flvB) in the genome of Chlamydomonas reinhardtii show high homology to flv1 and flv3 genes of the cyanobacterium Synechocystis sp. PCC 6803. The physiological role of these FDPs in eukaryotic green algae is not known, but it is of a special interest since these phototrophic organisms perform oxygenic photosynthesis similar to higher plants, which do not possess FDP homologs. We have analyzed the levels of flvA and flvB transcripts in C. reinhardtii cells under various environmental conditions and showed that these genes are highly expressed under ambient CO2 levels and during the early phase of acclimation to sulfur deprivation, just before the onset of anaerobiosis and the induction of efficient H2 photoproduction. Importantly, the increase in transcript levels of the flvA and flvB genes was also corroborated by protein levels. These results strongly suggest the involvement of FLVA and FLVB proteins in alternative electron transport. PMID:26063391

  7. Chlamydomonas Flavodiiron Proteins Facilitate Acclimation to Anoxia During Sulfur Deprivation.

    PubMed

    Jokel, Martina; Kosourov, Sergey; Battchikova, Natalia; Tsygankov, Anatoly A; Aro, Eva Mari; Allahverdiyeva, Yagut

    2015-08-01

    The flavodiiron proteins (FDPs) are involved in the detoxification of oxidative compounds, such as nitric oxide (NO) or O(2) in Archaea and Bacteria. In cyanobacteria, the FDPs Flv1 and Flv3 are essential in the light-dependent reduction of O(2) downstream of PSI. Phylogenetic analysis revealed that two genes (flvA and flvB) in the genome of Chlamydomonas reinhardtii show high homology to flv1 and flv3 genes of the cyanobacterium Synechocystis sp. PCC 6803. The physiological role of these FDPs in eukaryotic green algae is not known, but it is of a special interest since these phototrophic organisms perform oxygenic photosynthesis similar to higher plants, which do not possess FDP homologs. We have analyzed the levels of flvA and flvB transcripts in C. reinhardtii cells under various environmental conditions and showed that these genes are highly expressed under ambient CO(2) levels and during the early phase of acclimation to sulfur deprivation, just before the onset of anaerobiosis and the induction of efficient H(2) photoproduction. Importantly, the increase in transcript levels of the flvA and flvB genes was also corroborated by protein levels. These results strongly suggest the involvement of FLVA and FLVB proteins in alternative electron transport. PMID:26063391

  8. Identification of an NADP/thioredoxin system in Chlamydomonas reinhardtii

    NASA Technical Reports Server (NTRS)

    Huppe, H. C.; Picaud, A.; Buchanan, B. B.; Miginiac-Maslow, M.

    1991-01-01

    The protein components of the NADP/thioredoxin system, NADP-thioredoxin reductase (NTR) and thioredoxin h, have been purified and characterized from the green alga, Chlamydomonas reinhardtii. The analysis of this system confirms that photoautotrophic Chlamydomonas cells resemble leaves in having both an NADP- and ferrodoxin-linked thioredoxin redox system. Chlamydomonas thioredoxin h, which is smaller on sodium dodecyl sulfate-polyacrylamide gel electrophoresis than thioredoxin m from the same source, cross-reacted with antisera to thioredoxin h from spinach (Spinacia oleracea L.) and wheat germ (Triticum vulgaris L.) but not with antisera to m or f thioredoxins. In these properties, the thioredoxin h resembled a thioredoxin from Chlamydomonas, designated Ch1, whose sequence was reported recently (P. Decottignies et al., 1991, Eur. J. Biochem. 198, 505-512). The differential reactivity of thioredoxin h with antisera was used to demonstrate that thioredoxin h is enriched outside the chloroplast. The NTR was purified from Chlamydomonas using thioredoxin h from the same source. Similar to its counterpart from other organisms, Chlamydomonas NTR had a subunit size of approx. 36 kDa and was specific for NADPH. Chlamydomonas NTR effectively reduced thioredoxin h from the same source but showed little activity with the other thioredoxins tested, including spinach thioredoxin h and Escherichia coli thioredoxin. Comparison of the reduction of Chlamydomonas thioredoxins m and h by each of the endogenous thioredoxin reductases, NTR and ferredoxin-thioredoxin reductase, revealed a differential specificity of each enzyme for thioredoxin. Thus, NTR showed increased activity with thioredoxin h and ferredoxin-thioredoxin reductase with thioredoxins m and f.

  9. Photomixing of chlamydomonas rheinhardtii suspensions

    NASA Astrophysics Data System (ADS)

    Dervaux, Julien; Capellazzi Resta, Marina; Abou, Bérengère; Brunet, Philippe

    2014-11-01

    Chlamydomonas rheinhardtii is a fast swimming unicellular alga able to bias its swimming direction in gradients of light intensity, an ability know as phototaxis. We have investigated experimentally both the swimming behavior of individual cells and the macroscopic response of shallow suspensions of these micro-organisms in response to a localized light source. At low light intensity, algae exhibit positive phototaxis and accumulate beneath the excitation light. In weakly concentrated thin layers, the balance between phototaxis and cell motility results in steady symmetrical patterns compatible with a purely diffusive model using effective diffusion coefficients extracted from the analysis of individual cell trajectories. However, at higher cell density and layer depth, collective effects induce convective flows around the light source. These flows disturb the cell concentration patterns which spread and may then becomes unstable. Using large passive tracer particles, we have characterized the velocity fields associated with this forced bioconvection and their dependence on the cell density and layer depth. By tuning the light distribution, this mechanism of photo-bioconvection allows a fine control over the local fluid flows, and thus the mixing efficiency, in algal suspensions.

  10. Multi-gene phylogenetic analyses of New Zealand coralline algae: Corallinapetra Novaezelandiae gen. et sp. nov. and recognition of the Hapalidiales ord. nov.

    PubMed

    Nelson, Wendy A; Sutherland, Judith E; Farr, Tracy J; Hart, Darren R; Neill, Kate F; Kim, Hee Jeong; Yoon, Hwan Su

    2015-06-01

    Coralline red algae from the New Zealand region were investigated in a study focused on documenting regional diversity. We present a multi-gene analysis using sequence data obtained for four genes (nSSU, psaA, psbA, rbcL) from 68 samples. The study revealed cryptic diversity at both genus and species levels, confirming and providing further evidence of problems with current taxonomic concepts in the Corallinophycidae. In addition, a new genus Corallinapetra novaezelandiae gen. et sp. nov. is erected for material from northern New Zealand. Corallinapetra is excluded from all currently recognized families and orders within the Corallinophycidae and thus represents a previously unrecognized lineage within this subclass. We discuss rank in the Corallinophycidae and propose the order Hapalidiales. PMID:26986662

  11. Biomass and hydrogen photoproduction by a marine blue-green alga Oscillatoria sp. Miami BG 7 in natural seawater culture system

    SciTech Connect

    Ramachandran, S.

    1985-01-01

    A non-heterocystous marine blue-green alga Oscillatoria sp. Miami BG 7 showed high biomass yields and hydrogen production rates in a natural seawater based system. Variations in water quality such as salinity, pH, trace metal concentration and combined nitrogen level did not affect either the biomass or the hydrogen production. Recycling of the two steps involved in hydrogen production (i.e., aerobic growth phase and anaerobic hydrogen production phase) significantly increased (> 400%) the hydrogen yield. Immobilization of cells improved hydrogen production activity and its tolerance to adverse environmental conditions. Both the biomass and hydrogen production were not affected under uncontrolled outdoor environments. High biomass yield (250 mg dry wt/l/day or 40 g/m/sup 2//day), solar energy conversion efficiency (3.2%) and hydrogen production rate (1 ml H/sub 2//ml gel/day) were obtained in small scale outdoor systems.

  12. Crouania pumila sp. nov. (Callithamniaceae: Rhodophyta), a new species of marine red algae from the Seaflower International Biosphere Reserve, Caribbean Colombia.

    PubMed

    Gavio, Brigitte; Reyes-Gómez, Viviana P; Wynne, Michael J

    2013-09-01

    In the Colombian Caribbean, the marine macroalgal flora of the Seaflower International Biosphere Reserve has been little studied, despite its ecological importance. Historical records have reported only 201 macroalgae species within its area of almost 350,000 km2. However, recent surveys have shown a diversity of small algae previously overlooked. With the aim to determine the macroalgal diversity in the Reserve, we undertook field surveys in different ecosystems: coral reefs, seagrass beds, and rocky and sandy substrates, at different depths, from intertidal to 37 m. During these field surveys, we collected a small described species belonging to the genus Crouania (Callithamniaceae, Rhodophyta), Crouania pumila sp. nov. that is decribed in this paper. This new species was distinguished from other species of the genus by a distinctive suite of traits including its diminutive size (to only 3.5 mm in length), its decumbent, slightly calcified habit (epiphytic on other algae), its ramisympodial branching, the ecorticate main axes, and the elongate shape of the terminal cells of the cortical filaments. The observations were provided for both female (cystocarpic) and tetrasporangiate thalli; however, male thalli were not seen. Further studies have to be undertaken in this Reserve in order to carry out other macroalgal analysis and descriptions. PMID:24027904

  13. Acidophilic green alga Pseudochlorella sp. YKT1 accumulates high amount of lipid droplets under a nitrogen-depleted condition at a low-pH.

    PubMed

    Hirooka, Shunsuke; Higuchi, Sumio; Uzuka, Akihiro; Nozaki, Hisayoshi; Miyagishima, Shin-ya

    2014-01-01

    Microalgal storage lipids are considered to be a promising source for next-generation biofuel feedstock. However, microalgal biodiesel is not yet economically feasible due to the high cost of production. One of the reasons for this is that the use of a low-cost open pond system is currently limited because of the unavoidable contamination with undesirable organisms. Extremophiles have an advantage in culturing in an open pond system because they grow in extreme environments toxic to other organisms. In this study, we isolated the acidophilic green alga Pseudochlorella sp. YKT1 from sulfuric acid mine drainage in Nagano Prefecture, Japan. The vegetative cells of YKT1 display the morphological characteristics of Trebouxiophyceae and molecular phylogenetic analyses indicated it to be most closely related to Pseudochlorella pringsheimii. The optimal pH and temperature for the growth of YKT1 are pH 3.0-5.0 and a temperature 20-25°C, respectively. Further, YKT1 is able to grow at pH 2.0 and at 32°C, which corresponds to the usual water temperature in the outdoors in summer in many countries. YKT1 accumulates a large amount of storage lipids (∼30% of dry weigh) under a nitrogen-depleted condition at low-pH (pH 3.0). These results show that acidophilic green algae will be useful for industrial applications by acidic open culture systems. PMID:25221913

  14. Inhibitory effects of soluble algae products (SAP) released by Scenedesmus sp. LX1 on its growth and lipid production.

    PubMed

    Zhang, Tian-Yuan; Yu, Yin; Wu, Yin-Hu; Hu, Hong-Ying

    2013-10-01

    Soluble algal products (SAP) accumulated in culture medium via water reuse may affect the growth of microalga during the cultivation. Scenedesmus sp. LX1, a freshwater microalga, was used in this study to investigate the effect of SAP on growth and lipid production of microalga. Under the SAP concentrations of 6.4-25.8 mg L(-1), maximum algal density (K) and maximum growth rate (Rmax) of Scenedesmus sp. LX1 were decreased by 50-80% and 35-70% compared with the control group, respectively. The effect of SAP on lipid accumulation of Scenedesmus sp. LX1 was non-significant. According to hydrophilic-hydrophobic and acid-base properties, SAP was fractionized into six fractions. All of the fractions could inhibit the growth of Scenedesmus sp. LX1. Organic bases (HIB, HOB) and hydrophilic acids (HIA) showed the strongest inhibition. HIA could also decrease the lipid content of Scenedesmus sp. LX1 by 59.2%. As the inhibitory effect, SAP should be seriously treated before water reuse. PMID:23982061

  15. Use of biofuel by-product from the green algae Desmochloris sp. and diatom Nanofrustulum sp. meal in diets for nile tilapia Oreochromis niloticus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Algal by-product meals from the Hawaiian biofuels industry were evaluated as protein ingredients in diets for juveniles of Nile tilapia (Oreochromis niloticus). Four experimental diets were formulated to contain 40% protein and were made with fish meal, soybean meal, whole diatom (Nanofrustulum sp.)...

  16. Alga-Derived Substrates Select for Distinct Betaproteobacterial Lineages and Contribute to Niche Separation in Limnohabitans Strains▿

    PubMed Central

    Šimek, Karel; Kasalický, Vojtěch; Zapomělová, Eliška; Horňák, Karel

    2011-01-01

    We examined the proportions of major Betaproteobacteria subgroups within bacterial communities in diverse nonaxenic, monospecific cultures of algae or cyanobacteria: four species of cryptophyta (genera Cryptomonas and Rhodomonas), four species of chlorophyta (genera Pediastrum, Staurastrum, and Chlamydomonas), and two species of cyanobacteria (genera Dolichospermum and Aphanizomenon). In the cryptophyta cultures, Betaproteobacteria represented 48 to 71% of total bacteria, the genus Limnohabitans represented 18 to 26%, and the Polynucleobacter B subcluster represented 5 to 16%. In the taxonomically diverse chlorophyta group, the genus Limnohabitans accounted for 7 to 45% of total bacteria. In contrast, cyanobacterial cultures contained significantly lower proportions of the Limnohabitans bacteria (1 to 3% of the total) than the cryptophyta and chlorophyta cultures. Notably, largely absent in all of the cultures was Polynucleobacter necessarius (Polynucleobacter C subcluster). Subsequently, we examined the growth of Limnohabitans strains in the presence of different algae or their extracellular products (EPP). Two strains, affiliated with Limnohabitans planktonicus and Limnohabitans parvus, were separately inoculated into axenic cultures of three algal species growing in an inorganic medium: Cryptomonas sp., Chlamydomonas noctigama, and Pediastrum boryanum. The Limnohabitans strains cocultured with these algae or inoculated into their EPP consistently showed (i) pronounced population growth compared to the control without the algae or EPP and (ii) stronger growth stimulation of L. planktonicus than of L. parvus. Overall, growth responses of the Limnohabitans strains cultured with algae were highly species specific, which suggests a pronounced niche separation between two closely related Limnohabitans species likely mediated by different abilities to utilize the substrates produced by different algal species. PMID:21873481

  17. Alga-derived substrates select for distinct Betaproteobacterial lineages and contribute to niche separation in Limnohabitans strains.

    PubMed

    Simek, Karel; Kasalický, Vojtĕch; Zapomĕlová, Eliska; Hornák, Karel

    2011-10-01

    We examined the proportions of major Betaproteobacteria subgroups within bacterial communities in diverse nonaxenic, monospecific cultures of algae or cyanobacteria: four species of cryptophyta (genera Cryptomonas and Rhodomonas), four species of chlorophyta (genera Pediastrum, Staurastrum, and Chlamydomonas), and two species of cyanobacteria (genera Dolichospermum and Aphanizomenon). In the cryptophyta cultures, Betaproteobacteria represented 48 to 71% of total bacteria, the genus Limnohabitans represented 18 to 26%, and the Polynucleobacter B subcluster represented 5 to 16%. In the taxonomically diverse chlorophyta group, the genus Limnohabitans accounted for 7 to 45% of total bacteria. In contrast, cyanobacterial cultures contained significantly lower proportions of the Limnohabitans bacteria (1 to 3% of the total) than the cryptophyta and chlorophyta cultures. Notably, largely absent in all of the cultures was Polynucleobacter necessarius (Polynucleobacter C subcluster). Subsequently, we examined the growth of Limnohabitans strains in the presence of different algae or their extracellular products (EPP). Two strains, affiliated with Limnohabitans planktonicus and Limnohabitans parvus, were separately inoculated into axenic cultures of three algal species growing in an inorganic medium: Cryptomonas sp., Chlamydomonas noctigama, and Pediastrum boryanum. The Limnohabitans strains cocultured with these algae or inoculated into their EPP consistently showed (i) pronounced population growth compared to the control without the algae or EPP and (ii) stronger growth stimulation of L. planktonicus than of L. parvus. Overall, growth responses of the Limnohabitans strains cultured with algae were highly species specific, which suggests a pronounced niche separation between two closely related Limnohabitans species likely mediated by different abilities to utilize the substrates produced by different algal species. PMID:21873481

  18. The complete plastid genome sequence of the parasitic green alga Helicosporidium sp. is highly reduced and structured

    PubMed Central

    de Koning, Audrey P; Keeling, Patrick J

    2006-01-01

    Background Loss of photosynthesis has occurred independently in several plant and algal lineages, and represents a major metabolic shift with potential consequences for the content and structure of plastid genomes. To investigate such changes, we sequenced the complete plastid genome of the parasitic, non-photosynthetic green alga, Helicosporidium. Results The Helicosporidium plastid genome is among the smallest known (37.5 kb), and like other plastids from non-photosynthetic organisms it lacks all genes for proteins that function in photosynthesis. Its reduced size results from more than just loss of genes, however; it has little non-coding DNA, with only one intron and tiny intergenic spaces, and no inverted repeat (no duplicated genes at all). It encodes precisely the minimal complement of tRNAs needed to translate the universal genetic code, and has eliminated all redundant isoacceptors. The Helicosporidium plastid genome is also highly structured, with each half of the circular genome containing nearly all genes on one strand. Helicosporidium is known to be related to trebouxiophyte green algae, but the genome is structured and compacted in a manner more reminiscent of the non-photosynthetic plastids of apicomplexan parasites. Conclusion Helicosporidium contributes significantly to our understanding of the evolution of plastid DNA because it illustrates the highly ordered reduction that occurred following the loss of a major metabolic function. The convergence of plastid genome structure in Helicosporidium and the Apicomplexa raises the interesting possibility that there are common forces that shape plastid genomes, subsequent to the loss of photosynthesis in an organism. PMID:16630350

  19. The Chlamydomonas Cell Cycle

    PubMed Central

    Cross, Frederick R.; Umen, James G.

    2015-01-01

    The position of Chlamydomonas within the eukaryotic phylogeny makes it a unique model in at least two important ways: as a representative of the critically important, early-diverging lineage leading to plants, and as a microbe retaining important features of the last eukaryotic common ancestor (LECA) that have been lost in the highly studied yeast lineages. Its cell biology has been studied for many decades, and it has well-developed experimental genetic tools, both classical (Mendelian) and molecular. Unlike land plants, it is a haploid with very few gene duplicates, making it ideal for loss-of-function genetic studies. The Chlamydomonas cell cycle has a striking temporal and functional separation between cell growth and rapid cell divisions, probably connected to the interplay between diurnal cycles that drive photosynthetic cell growth with the cell division cycle; it also exhibits a highly choreographed interaction between the cell cycle and its centriole/basal body/flagellar cycle. Here we review the current status of studies of the Chlamydomonas cell cycle. We begin with an overview of cell cycle control in the well-studied yeast and animal systems, which has yielded a canonical, well-supported model. We discuss briefly what is known about similarities and differences in plant cell cycle control compared to this model. We next review the cytology and cell biology of the multiple fission cell cycle of Chlamydomonas. Lastly we review recent genetic approaches and insights into Chlamydomonas cell cycle regulation that have been enabled by a new generation of genomics-based tools. PMID:25690512

  20. The importance of light and photoperiod in sexual reproduction and geographical distribution in the green snow alga, Chloromonas sp.-D (Chlorophyceae, Volvocales)

    NASA Astrophysics Data System (ADS)

    Hoham, Ronald W.; Marcarelli, Amy M.; Rogers, Haldre S.; Ragan, Michael D.; Petre, Benjamin M.; Ungerer, Michael D.; Barnes, Joseph M.; Francis, David O.

    2000-12-01

    The effects of premating light regimes on sexual reproduction and the production of spherical cells in Chloromonas sp.-D, a unicellular green snow alga, were studied using cross-mating strains 582C and 582D isolated from snowpacks associated with mixed hardwood- softwood forests in Whetstone Gulf State Park, Tughill Plateau, NY. Two pre-acclimation regimes were used, Vita-Lite as controls (530- 700 nm peak) and blue light as experimentals (430- 460 nm peak) prior to the mating experiments. In blue light, an increase in the number of matings and spherical cells (spheres) produced in the life cycle was observed as the photoperiod increased. This implies that longer photoperiods of blue light are more optimal for sexual reproduction in Chloromonas sp.-D than shorter ones. Under Vita-Lite, there was a significant increase in the number of matings and spheres with the extended 20 : 4 photoperiod compared with the shorter 14 : 10 photoperiod. Under blue light, significantly more matings and spheres occurred than under Vita-Lite using the same irradiance level of 95µmol photons m-2 s-1 (photosynthetically active radiation [PAR] of 400- 700 nm) for the 14 : 10 and 20 : 4 photoperiods. The results of these experiments suggest that Chloromonas sp.-D, known only from the Tughill Plateau, NY, is not reproducing optimally at this site where it grows and reproduces under an approximate 14 : 10 photoperiod in early April. However, in the upper 10 cm of snow in the Tughill Plateau, a blue light irradiance level of 95µmol photons m-2 s-1 occurs, which is optimal for this species. When these conditions are combined with a 14 : 10 photoperiod, the Tughill Plateau appears to be sub-optimal for mating and production of spherical cells. Since Chloromonas sp.-D does not appear to have a dependence on a dark cycle, this would allow it to expand its geographical distribution. It may reproduce more optimally under blue light (95µmol photons m-2 s-1) with an extended photoperiod (>20 : 4

  1. Enhancement of Biodiesel Production from Marine Alga, Scenedesmus sp. through In Situ Transesterification Process Associated with Acidic Catalyst

    PubMed Central

    Kim, Ga Vin; Choi, WoonYong; Kang, DoHyung; Lee, ShinYoung; Lee, HyeonYong

    2014-01-01

    The aim of this study was to increase the yield of biodiesel produced by Scenedesmus sp. through in situ transesterification by optimizing various process parameters. Based on the orthogonal matrix analysis for the acidic catalyst, the effects of the factors decreased in the order of reaction temperature (47.5%) > solvent quantity (26.7%) > reaction time (17.5%) > catalyst amount (8.3%). Based on a Taguchi analysis, the effects of the factors decreased in the order of solvent ratio (34.36%) > catalyst (28.62%) > time (19.72%) > temperature (17.32%). The overall biodiesel production appeared to be better using NaOH as an alkaline catalyst rather than using H2SO4 in an acidic process, at 55.07 ± 2.18% (based on lipid weight) versus 48.41 ± 0.21%. However, in considering the purified biodiesel, it was found that the acidic catalyst was approximately 2.5 times more efficient than the alkaline catalyst under the following optimal conditions: temperature of 70°C (level 2), reaction time of 10 hrs (level 2), catalyst amount of 5% (level 3), and biomass to solvent ratio of 1 : 15 (level 2), respectively. These results clearly demonstrated that the acidic solvent, which combined oil extraction with in situ transesterification, was an effective catalyst for the production of high-quantity, high-quality biodiesel from a Scenedesmus sp. PMID:24689039

  2. Most microRNAs in the single-cell alga Chlamydomonas reinhardtii are produced by Dicer-like 3-mediated cleavage of introns and untranslated regions of coding RNAs.

    PubMed

    Valli, Adrian A; Santos, Bruno A C M; Hnatova, Silvia; Bassett, Andrew R; Molnar, Attila; Chung, Betty Y; Baulcombe, David C

    2016-04-01

    We describe here a forward genetic screen to investigate the biogenesis, mode of action, and biological function of miRNA-mediated RNA silencing in the model algal species,Chlamydomonas reinhardtii Among the mutants from this screen, there were three atDicer-like 3that failed to produce both miRNAs and siRNAs and others affecting diverse post-biogenesis stages of miRNA-mediated silencing. The DCL3-dependent siRNAs fell into several classes including transposon- and repeat-derived siRNAs as in higher plants. The DCL3-dependent miRNAs differ from those of higher plants, however, in that many of them are derived from mRNAs or from the introns of pre-mRNAs. Transcriptome analysis of the wild-type anddcl3mutant strains revealed a further difference from higher plants in that the sRNAs are rarely negative switches of mRNA accumulation. The few transcripts that were more abundant indcl3mutant strains than in wild-type cells were not due to sRNA-targeted RNA degradation but to direct DCL3 cleavage of miRNA and siRNA precursor structures embedded in the untranslated (and translated) regions of the mRNAs. Our analysis reveals that the miRNA-mediated RNA silencing inC. reinhardtiidiffers from that of higher plants and informs about the evolution and function of this pathway in eukaryotes. PMID:26968199

  3. Most microRNAs in the single-cell alga Chlamydomonas reinhardtii are produced by Dicer-like 3-mediated cleavage of introns and untranslated regions of coding RNAs

    PubMed Central

    Valli, Adrian A.; Santos, Bruno A.C.M.; Hnatova, Silvia; Bassett, Andrew R.; Molnar, Attila; Chung, Betty Y.; Baulcombe, David C.

    2016-01-01

    We describe here a forward genetic screen to investigate the biogenesis, mode of action, and biological function of miRNA-mediated RNA silencing in the model algal species, Chlamydomonas reinhardtii. Among the mutants from this screen, there were three at Dicer-like 3 that failed to produce both miRNAs and siRNAs and others affecting diverse post-biogenesis stages of miRNA-mediated silencing. The DCL3-dependent siRNAs fell into several classes including transposon- and repeat-derived siRNAs as in higher plants. The DCL3-dependent miRNAs differ from those of higher plants, however, in that many of them are derived from mRNAs or from the introns of pre-mRNAs. Transcriptome analysis of the wild-type and dcl3 mutant strains revealed a further difference from higher plants in that the sRNAs are rarely negative switches of mRNA accumulation. The few transcripts that were more abundant in dcl3 mutant strains than in wild-type cells were not due to sRNA-targeted RNA degradation but to direct DCL3 cleavage of miRNA and siRNA precursor structures embedded in the untranslated (and translated) regions of the mRNAs. Our analysis reveals that the miRNA-mediated RNA silencing in C. reinhardtii differs from that of higher plants and informs about the evolution and function of this pathway in eukaryotes. PMID:26968199

  4. Procedures for the Generation of Mature Chlamydomonas reinhardtii Zygotes for Molecular and Biochemical Analyses 1

    PubMed Central

    Wegener, Dorothee; Treier, Ulrike; Beck, Christoph F.

    1989-01-01

    Zygotes represent an important stage in the sexual cycle of the unicellular green alga Chlamydomonas reinhardtii. To study zygote germination at a molecular level, a protocol was elaborated for the generation of zygotes in large quantities and a method was developed for the extraction from zygotes of RNA that could be translated in vitro. Images Figure 1 Figure 3 PMID:16666800

  5. The production of sulfonated chitosan-sodium alginate found in brown algae (Sargassum sp.) composite membrane as proton exchange membrane fuel cell (PEMFC)

    NASA Astrophysics Data System (ADS)

    Wafiroh, Siti; Pudjiastuti, Pratiwi; Sari, Ilma Indana

    2016-03-01

    The majority of energy was used in this period is from fossil fuel, which getting decreased in the future. The objective of this research is production and characterization of sulfonated chitosan-sodium alginate found in brown algae (Sargassum sp.) composite membrane as Proton Exchange Membrane Fuel Cell (PEMFC) for alternative energy. PEMFC was produced with 4 variations (w/w) ratio between chitosan and sodium alginate, 8 : 0, 8 : 1, 8 : 2, 8 : 4 (w/w). The production of membrane was mixed sodium alginate solution into chitosan solution and sulfonated with H2SO4 0.72 N. The characterization of the PEM was uses Modulus Young analysis, water swelling, ion exchange capacity, FTIR, SEM, DTA, methanol permeability and proton conductivity. The result of the research, showed that the optimum membrane was with ratio 8 : 2 (w/w) that the Modulus Young 8564 kN/m2, water swelling 31.86%, ion exchange capacity 1.020 meq/g, proton conductivity 8,8 × 10-6 S/cm, methanol permeability 1.90 × 10-8 g/cm2s and glass transition temperature (Tg) 100.9 °C, crystalline temperature (Tc) 227.6 °C, and the melting temperature (Tm) 267.9 °C.

  6. Effective Biological DeNOx of Industrial Flue Gas by the Mixotrophic Cultivation of an Oil-Producing Green Alga Chlorella sp. C2.

    PubMed

    Chen, Weixian; Zhang, Shanshan; Rong, Junfeng; Li, Xiang; Chen, Hui; He, Chenliu; Wang, Qiang

    2016-02-01

    Nitrogen oxides (NOx) are the components of fossil flue gas that result in the most serious environmental concerns. We previously showed that the biological removal of NOx by microalgae appears superior to traditional treatments. This study optimizes the strategy for the microalgal-based DeNOx of flue gas by fed-batch mixotrophic cultivation. By using actual flue gas fixed salts (FGFS) as the nitrogen supply, the mixotrophical cultivation of the green alga Chlorella sp. C2 with high NOx absorption efficiency was optimized in a stepwise manner in a 5 L bioreactor and resulted in a maximum biomass productivity of 9.87 g L(-1) d(-1). The optimized strategy was further scaled up to 50 L, and a biomass productivity of 7.93 g L(-1) d(-1) was achieved, with an overall DeNOx efficiency of 96%, along with an average nitrogen CR of 0.45 g L(-1) d(-1) and lipid productivity of 1.83 g L(-1) d(-1). With an optimized mixotrophical cultivation, this study further proved the feasibility of using Chlorella for the combination of efficient biological DeNOx of flue gas and microalgae-based products production. Thus, this study shows a promising industrial strategy for flue gas biotreatment in plants with limited land area. PMID:26751001

  7. Symbiodinium thermophilum sp. nov., a thermotolerant symbiotic alga prevalent in corals of the world's hottest sea, the Persian/Arabian Gulf

    PubMed Central

    Hume, B. C. C.; D'Angelo, C.; Smith, E. G.; Stevens, J. R.; Burt, J.; Wiedenmann, J.

    2015-01-01

    Coral reefs are in rapid decline on a global scale due to human activities and a changing climate. Shallow water reefs depend on the obligatory symbiosis between the habitat forming coral host and its algal symbiont from the genus Symbiodinium (zooxanthellae). This association is highly sensitive to thermal perturbations and temperatures as little as 1°C above the average summer maxima can cause the breakdown of this symbiosis, termed coral bleaching. Predicting the capacity of corals to survive the expected increase in seawater temperatures depends strongly on our understanding of the thermal tolerance of the symbiotic algae. Here we use molecular phylogenetic analysis of four genetic markers to describe Symbiodinium thermophilum, sp. nov. from the Persian/Arabian Gulf, a thermally tolerant coral symbiont. Phylogenetic inference using the non-coding region of the chloroplast psbA gene resolves S. thermophilum as a monophyletic lineage with large genetic distances from any other ITS2 C3 type found outside the Gulf. Through the characterisation of Symbiodinium associations of 6 species (5 genera) of Gulf corals, we demonstrate that S. thermophilum is the prevalent symbiont all year round in the world's hottest sea, the southern Persian/Arabian Gulf. PMID:25720577

  8. Symbiodinium thermophilum sp. nov., a thermotolerant symbiotic alga prevalent in corals of the world's hottest sea, the Persian/Arabian Gulf.

    PubMed

    Hume, B C C; D'Angelo, C; Smith, E G; Stevens, J R; Burt, J; Wiedenmann, J

    2015-01-01

    Coral reefs are in rapid decline on a global scale due to human activities and a changing climate. Shallow water reefs depend on the obligatory symbiosis between the habitat forming coral host and its algal symbiont from the genus Symbiodinium (zooxanthellae). This association is highly sensitive to thermal perturbations and temperatures as little as 1°C above the average summer maxima can cause the breakdown of this symbiosis, termed coral bleaching. Predicting the capacity of corals to survive the expected increase in seawater temperatures depends strongly on our understanding of the thermal tolerance of the symbiotic algae. Here we use molecular phylogenetic analysis of four genetic markers to describe Symbiodinium thermophilum, sp. nov. from the Persian/Arabian Gulf, a thermally tolerant coral symbiont. Phylogenetic inference using the non-coding region of the chloroplast psbA gene resolves S. thermophilum as a monophyletic lineage with large genetic distances from any other ITS2 C3 type found outside the Gulf. Through the characterisation of Symbiodinium associations of 6 species (5 genera) of Gulf corals, we demonstrate that S. thermophilum is the prevalent symbiont all year round in the world's hottest sea, the southern Persian/Arabian Gulf. PMID:25720577

  9. Subunit Asa1 spans all the peripheral stalk of the mitochondrial ATP synthase of the chlorophycean alga Polytomella sp.

    PubMed

    Colina-Tenorio, Lilia; Miranda-Astudillo, Héctor; Cano-Estrada, Araceli; Vázquez-Acevedo, Miriam; Cardol, Pierre; Remacle, Claire; González-Halphen, Diego

    2016-04-01

    Mitochondrial F1FO-ATP synthase of chlorophycean algae is dimeric. It contains eight orthodox subunits (alpha, beta, gamma, delta, epsilon, OSCP, a and c) and nine atypical subunits (Asa1 to 9). These subunits build the peripheral stalk of the enzyme and stabilize its dimeric structure. The location of the 66.1kDa subunit Asa1 has been debated. On one hand, it was found in a transient subcomplex that contained membrane-bound subunits Asa1/Asa3/Asa5/Asa8/a (Atp6)/c (Atp9). On the other hand, Asa1 was proposed to form the bulky structure of the peripheral stalk that contacts the OSCP subunit in the F1 sector. Here, we overexpressed and purified the recombinant proteins Asa1 and OSCP and explored their interactions in vitro, using immunochemical techniques and affinity chromatography. Asa1 and OSCP interact strongly, and the carboxy-terminal half of OSCP seems to be instrumental for this association. In addition, the algal ATP synthase was partially dissociated at relatively high detergent concentrations, and an Asa1/Asa3/Asa5/Asa8/a/c10 subcomplex was identified. Furthermore, Far-Western analysis suggests an Asa1-Asa8 interaction. Based on these results, a model is proposed in which Asa1 spans the whole peripheral arm of the enzyme, from a region close to the matrix-exposed side of the mitochondrial inner membrane to the F1 region where OSCP is located. 3D models show elongated, helix-rich structures for chlorophycean Asa1 subunits. Asa1 subunit probably plays a scaffolding role in the peripheral stalk analogous to the one of subunit b in orthodox mitochondrial enzymes. PMID:26657474

  10. Description of Lecythium terrestris sp. nov. (Chlamydophryidae, Cercozoa), a Soil Dwelling Protist Feeding on Fungi and Algae.

    PubMed

    Dumack, Kenneth; Müller, Marina E H; Bonkowski, Michael

    2016-04-01

    Testate amoebae have been frequently studied by protistologists, but still little information is available on some groups like the Chlamydophryidae. These amoebae are difficult to culture and therefore quantitative information on their morphology, phylogeny and ecology is scarce. We isolated and cultured a small testate amoeba from an agricultural field at Müncheberg near Berlin, Germany. Morphological analyses revealed it to be a new species of the genus Lecythium. We describe Lecythium terrestris sp. nov. and present its morphology, mycophagous and algivorous feeding habits and its ability to form cell aggregates by fusion. Using small-subunit ribosomal RNA gene phylogeny, we could confirm the phylogenetic position of the genus Lecythium among the Cercozoa where it groups closely to Pseudodifflugiidae (Tectofilosida). PMID:26874465

  11. Tools for regulated gene expression in the chloroplast of Chlamydomonas.

    PubMed

    Rochaix, Jean-David; Surzycki, Raymond; Ramundo, Silvia

    2014-01-01

    The green unicellular alga Chlamydomonas reinhardtii has emerged as a very attractive model system for chloroplast genetic engineering. Algae can be transformed readily at the chloroplast level through bombardment of cells with a gene gun, and transformants can be selected using antibiotic resistance or phototrophic growth. An inducible chloroplast gene expression system could be very useful for several reasons. First, it could be used to elucidate the function of essential chloroplast genes required for cell growth and survival. Second, it could be very helpful for expressing proteins which are toxic to the algal cells. Third, it would allow for the reversible depletion of photosynthetic complexes thus making it possible to study their biogenesis in a controlled fashion. Fourth, it opens promising possibilities for hydrogen production in Chlamydomonas. Here we describe an inducible/repressible chloroplast gene expression system in Chlamydomonas in which the copper-regulated Cyc6 promoter drives the expression of the nuclear Nac2 gene encoding a protein which is targeted to the chloroplast where it acts specifically on the chloroplast psbD 5'-untranslated region and is required for the stable accumulation of the psbD mRNA and photosystem II. The system can be used for any chloroplast gene or transgene by placing it under the control of the psbD 5'-untranslated region. PMID:24599871

  12. Proton gradient regulation 5-mediated cyclic electron flow under ATP- or redox-limited conditions: a study of ΔATpase pgr5 and ΔrbcL pgr5 mutants in the green alga Chlamydomonas reinhardtii.

    PubMed

    Johnson, Xenie; Steinbeck, Janina; Dent, Rachel M; Takahashi, Hiroko; Richaud, Pierre; Ozawa, Shin-Ichiro; Houille-Vernes, Laura; Petroutsos, Dimitris; Rappaport, Fabrice; Grossman, Arthur R; Niyogi, Krishna K; Hippler, Michael; Alric, Jean

    2014-05-01

    The Chlamydomonas reinhardtii proton gradient regulation5 (Crpgr5) mutant shows phenotypic and functional traits similar to mutants in the Arabidopsis (Arabidopsis thaliana) ortholog, Atpgr5, providing strong evidence for conservation of PGR5-mediated cyclic electron flow (CEF). Comparing the Crpgr5 mutant with the wild type, we discriminate two pathways for CEF and determine their maximum electron flow rates. The PGR5/proton gradient regulation-like1 (PGRL1) ferredoxin (Fd) pathway, involved in recycling excess reductant to increase ATP synthesis, may be controlled by extreme photosystem I acceptor side limitation or ATP depletion. Here, we show that PGR5/PGRL1-Fd CEF functions in accordance with an ATP/redox control model. In the absence of Rubisco and PGR5, a sustained electron flow is maintained with molecular oxygen instead of carbon dioxide serving as the terminal electron acceptor. When photosynthetic control is decreased, compensatory alternative pathways can take the full load of linear electron flow. In the case of the ATP synthase pgr5 double mutant, a decrease in photosensitivity is observed compared with the single ATPase-less mutant that we assign to a decreased proton motive force. Altogether, our results suggest that PGR5/PGRL1-Fd CEF is most required under conditions when Fd becomes overreduced and photosystem I is subjected to photoinhibition. CEF is not a valve; it only recycles electrons, but in doing so, it generates a proton motive force that controls the rate of photosynthesis. The conditions where the PGR5 pathway is most required may vary in photosynthetic organisms like C. reinhardtii from anoxia to high light to limitations imposed at the level of carbon dioxide fixation. PMID:24623849

  13. Reparation in unicellular green algae during chronic exposure to the action of mutagenic factors. II. Restoration of single-stranded DNA breaks following exposure of Chlamydomonas reinchardii to gamma-irradiation

    SciTech Connect

    Sergeeva, S.A.; Ptitsina, S.N.; Shevchenko, V.A.

    1986-12-01

    The restoration of single-stranded breaks in the DNA in different strains of unicellular green algae (chlamydomonads) during chronic exposure to the action of mutagenic factors following ..gamma..-irradiation was investigated. It was shown that the restoration of DNA breaks was most effective in the case of strain M ..gamma../sup mt/sup +//, which is resistant to radiation. Strains, that were sensitive to UV irradiation showed a similar order of DNA break restoration as the wild-type strain. Strain UVS-1 showed a higher level of restoration than the wild-type strain. The data indicated that chlamydomonads have different pathways of reparation, which lead to the restoration of breaks induced by ..gamma..-irradiation and UV-rays.

  14. Salinity affects the photoacclimation of Chlamydomonas raudensis Ettl UWO241.

    PubMed

    Takizawa, Kenji; Takahashi, Shinichiro; Hüner, Norman P A; Minagawa, Jun

    2009-03-01

    Chlamydomonas raudensis Ettl UWO241, a natural variant of C. raudensis, is deficient in state transitions. Its habitat, the deepest layer of Lake Bonney in Antarctica, features low irradiance, low temperature, and high salinity. Although psychrophily and low-light acclimation of this green alga has been described, very little information is available on the effect of salinity. Here, we demonstrate that this psychrophile is halotolerant, not halophilic, and it shows energy redistribution between photosystem I and II based on energy spillover under low-salt conditions. Furthermore, we revealed that C. raudensis exhibits higher non-photochemical quenching in comparison with the mesophile Chlamydomonas reinhardtii, when grown with low-salt, which is due to the lower proton conductivity across the thylakoid membrane. Significance of the C. raudensis UWO241 traits found in the low salinity culture are implicated with their natural habitats, including the high salinity and extremely stable light environments. PMID:19137412

  15. Nonphotochemical quenching of chlorophyll fluorescence in Chlamydomonas reinhardtii.

    PubMed

    Finazzi, Giovanni; Johnson, Giles N; Dall'Osto, Luca; Zito, Francesca; Bonente, Giulia; Bassi, Roberto; Wollman, Francis-André

    2006-02-01

    Unlike plants, Chlamydomonas reinhardtii shows a restricted ability to develop nonphotochemical quenching upon illumination. Most of this limited quenching is due to state transitions instead of DeltapH-driven high-energy state quenching, qE. The latter could only be observed when the ability of the cells to perform photosynthesis was impaired, either by lowering temperature to approximately 0 degrees C or in mutants lacking RubisCO activity. Two main features were identified that account for the low level of qE in Chlamydomonas. On one hand, the electrochemical proton gradient generated upon illumination is apparently not sufficient to promote fluorescence quenching. On the other hand, the capacity to transduce the presence of a DeltapH into a quenching response is also intrinsically decreased in this alga, when compared to plants. The possible mechanism leading to these differences is discussed. PMID:16445291

  16. Metabolism of D-lactate and structurally related organic acids in Chlamydomonas reinhardtii

    SciTech Connect

    Husic, D.W.

    1986-01-01

    During the initial minutes of anaerobiosis, /sup 14/C-labeled D-lactate, derived from the photosynthetic sugar phosphate pool, accumulated in the unicellular green alga, Chlamydomonas reinhardtii. The production of the D-isomer of lactate by algae is in contrast to plant and mammalian cells in which L-lactate is formed. After initial lactate formation, Chlamydomonas exhibits a mixed-acid type fermentation, thereby avoiding lactate accumulation and enabling the cells to tolerate extended periods of anaerobiosis. A pyruvate reductase which catalyzes the formation of D-lactate in Chlamydomonas was partially purified and characterized. Lactate produced anaerobically was metabolized only when Chlamydomonas cells were returned to aerobic conditions, and reoxidation of the D-lactate was apparently catalyzed by a mitochondrial membrane-bound dehydrogenase, rather than by the soluble pyruvate reductase. Mutants of Chlamydomonas, deficient in mitochondrial respiration, were used to demonstrate that lactate metabolism was linked to the mitochondrial electron transport chain. In addition, the oxidation of glycolate, a structural analog of lactate, was also linked to mitochondrial electron transport in vivo.

  17. UV-B Perception and Acclimation in Chlamydomonas reinhardtii.

    PubMed

    Tilbrook, Kimberley; Dubois, Marine; Crocco, Carlos D; Yin, Ruohe; Chappuis, Richard; Allorent, Guillaume; Schmid-Siegert, Emanuel; Goldschmidt-Clermont, Michel; Ulm, Roman

    2016-04-01

    Plants perceive UV-B, an intrinsic component of sunlight, via a signaling pathway that is mediated by the photoreceptor UV RESISTANCE LOCUS8 (UVR8) and induces UV-B acclimation. To test whether similar UV-B perception mechanisms exist in the evolutionarily distant green alga Chlamydomonas reinhardtii, we identified Chlamydomonas orthologs of UVR8 and the key signaling factor CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). Cr-UVR8 shares sequence and structural similarity to Arabidopsis thaliana UVR8, has conserved tryptophan residues for UV-B photoreception, monomerizes upon UV-B exposure, and interacts with Cr-COP1 in a UV-B-dependent manner. Moreover, Cr-UVR8 can interact with At-COP1 and complement the Arabidopsis uvr8 mutant, demonstrating that it is a functional UV-B photoreceptor. Chlamydomonas shows apparent UV-B acclimation in colony survival and photosynthetic efficiency assays. UV-B exposure, at low levels that induce acclimation, led to broad changes in the Chlamydomonas transcriptome, including in genes related to photosynthesis. Impaired UV-B-induced activation in the Cr-COP1 mutant hit1 indicates that UVR8-COP1 signaling induces transcriptome changes in response to UV-B. Also, hit1 mutants are impaired in UV-B acclimation. Chlamydomonas UV-B acclimation preserved the photosystem II core proteins D1 and D2 under UV-B stress, which mitigated UV-B-induced photoinhibition. These findings highlight the early evolution of UVR8 photoreceptor signaling in the green lineage to induce UV-B acclimation and protection. PMID:27020958

  18. Hydrogen evolution as a consumption mode of reducing equivalents in green algal fermentation. [Chlamydomonas reinhardii; Chlorella pyrenoidosa; Chlorococcum minutum

    SciTech Connect

    Ohta, S.; Miyamoto, K.; Miura, Y.

    1987-04-01

    Dark anaerobic fermentation in the green algae Chlamydomonas MGA 161, Chlamydomonas reinhardtii, Chlorella pyrenoidosa, and Chlorococcum minutum was studied. Their isolate, Chlamydomonas MGA 161, was unusual in having high H/sub 2/ but almost no formate. The fermentation pattern in Chlamydomonas MGA 161 was altered by changes in the NaCl or NH/sub 4/Cl concentration. Glycerol formation increased at low (0.1%) and high (7%) NaCl concentrations starch degradation, and formation of ethanol, H/sub 2/, and CO/sub 2/ increased with the addition of NH/sub 4/Cl to above 5 millimolar in N-deficient cells. C. reinhardtii and C.pyrenoidosa exhibited a very similar anaerobic metabolism, forming formate, acetate and ethanol in a ratio of about 2:2:1. C. minimum was also unusual in forming acetate, glycerol, and CO/sub 2/ as its main products, with H/sub 2/, formate, and ethanol being formed in negligible amounts. In the presence of CO, ethanol formation increased twofold in Chlamydomonas MGA 161 and C. reinhardtii, but the fermentation pattern in C. minimum did not change. An experiment with hypophosphite addition showed that dark H/sub 2/ evolution of the Escherichia coli type could be ruled out in Chlamydomonas MGA 161 and C. reinhardtii. Among the green algae investigated, three fermentation types were identified by the distribution pattern of the end products, which reflected the consumption model of reducing equivalents in the cells.

  19. Function of the chloroplast hydrogenase in the microalga Chlamydomonas: the role of hydrogenase and state transitions during photosynthetic activation in anaerobiosis.

    PubMed

    Ghysels, Bart; Godaux, Damien; Matagne, René F; Cardol, Pierre; Franck, Fabrice

    2013-01-01

    Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment. PMID:23717558

  20. Production of therapeutic proteins in the chloroplast of Chlamydomonas reinhardtii

    PubMed Central

    2014-01-01

    Chloroplast transformation in the photosynthetic alga Chlamydomonas reinhardtii has been used to explore the potential to use it as an inexpensive and easily scalable system for the production of therapeutic recombinant proteins. Diverse proteins, such as bacterial and viral antigens, antibodies and, immunotoxins have been successfully expressed in the chloroplast using endogenous and chimeric promoter sequences. In some cases, proteins have accumulated to high level, demonstrating that this technology could compete with current production platforms. This review focuses on the works that have engineered the chloroplast of C. reinhardtii with the aim of producing recombinant proteins intended for therapeutical use in humans or animals. PMID:25136510

  1. Production of therapeutic proteins in the chloroplast of Chlamydomonas reinhardtii.

    PubMed

    Almaraz-Delgado, Alma Lorena; Flores-Uribe, José; Pérez-España, Víctor Hugo; Salgado-Manjarrez, Edgar; Badillo-Corona, Jesús Agustín

    2014-01-01

    Chloroplast transformation in the photosynthetic alga Chlamydomonas reinhardtii has been used to explore the potential to use it as an inexpensive and easily scalable system for the production of therapeutic recombinant proteins. Diverse proteins, such as bacterial and viral antigens, antibodies and, immunotoxins have been successfully expressed in the chloroplast using endogenous and chimeric promoter sequences. In some cases, proteins have accumulated to high level, demonstrating that this technology could compete with current production platforms. This review focuses on the works that have engineered the chloroplast of C. reinhardtii with the aim of producing recombinant proteins intended for therapeutical use in humans or animals. PMID:25136510

  2. Catenovulum maritimus sp. nov., a novel agarolytic gammaproteobacterium isolated from the marine alga Porphyra yezoensis Ueda (AST58-103), and emended description of the genus Catenovulum.

    PubMed

    Li, Dong-Qi; Zhou, Yan-Xia; Liu, Tao; Chen, Guan-Jun; Du, Zong-Jun

    2015-08-01

    A novel agarolytic, Gram-stain negative, heterotrophic, facultatively anaerobic and pale-white pigmented bacterial strain, designated Q1(T), was isolated from the marine alga Porphyra yezoensis Ueda (AST58-103) collected from the coastal area of Weihai, China. The cells are motile by means of peritrichous flagella. The isolate requires NaCl for growth, while seawater is not necessary, and growth occurs optimally at about 30-33 °C, in 1-3 % (w/v) NaCl and at pH 7-7.5. Strain Q1(T) shows oxidase-positive and catalase-negative activities, and possesses the ability to hydrolyse starch and alginate, but not cellulose, gelatin, urea or Tween-80. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain Q1(T) is affiliated with the family Alteromonadaceae within the class Gammaproteobacteria. The isolate, strain Q1(T), is most closely related to Catenovulum agarivorans YM01(T) (94.85 %), with less than 91.2 % sequence similarity to other close relatives with validly published names. The draft genome sequence of strain Q1(T) consists of 62 contigs (>200 bp) of 4,548,270 bp. The genomes of Q1(T) and YM01(T) have an ANI value of 70.7 %, and the POCP value between the two genomes is 64.4 %. The genomic DNA G+C content of strain Q1(T) is 37.9 mol% as calculated from the draft genome sequence. The main isoprenoid quinone is ubiquinone-8. The predominant cellular fatty acids are summed feature 3 (C16:1 ω7c and/or iso-C15:0 2-OH), C16:0 and C18:1 ω7c. The major polar lipids are phosphatidylethanolamine and phosphatidylglycerol. Based on data from a polyphasic chemotaxonomic, physiological and biochemical study, strain Q1(T) should be classified as a novel species of the genus Catenovulum, for which the name Catenovulum maritimus sp. nov. is proposed. The type strain is Q1(T) (=CICC 10836(T)=DSM 28813(T)). PMID:26036673

  3. Systemic Cold Stress Adaptation of Chlamydomonas reinhardtii*

    PubMed Central

    Valledor, Luis; Furuhashi, Takeshi; Hanak, Anne-Mette; Weckwerth, Wolfram

    2013-01-01

    Chlamydomonas reinhardtii is one of the most important model organisms nowadays phylogenetically situated between higher plants and animals (Merchant et al. 2007). Stress adaptation of this unicellular model algae is in the focus because of its relevance to biomass and biofuel production. Here, we have studied cold stress adaptation of C. reinhardtii hitherto not described for this algae whereas intensively studied in higher plants. Toward this goal, high throughput mass spectrometry was employed to integrate proteome, metabolome, physiological and cell-morphological changes during a time-course from 0 to 120 h. These data were complemented with RT-qPCR for target genes involved in central metabolism, signaling, and lipid biosynthesis. Using this approach dynamics in central metabolism were linked to cold-stress dependent sugar and autophagy pathways as well as novel genes in C. reinhardtii such as CKIN1, CKIN2 and a hitherto functionally not annotated protein named CKIN3. Cold stress affected extensively the physiology and the organization of the cell. Gluconeogenesis and starch biosynthesis pathways are activated leading to a pronounced starch and sugar accumulation. Quantitative lipid profiles indicate a sharp decrease in the lipophilic fraction and an increase in polyunsaturated fatty acids suggesting this as a mechanism of maintaining membrane fluidity. The proteome is completely remodeled during cold stress: specific candidates of the ribosome and the spliceosome indicate altered biosynthesis and degradation of proteins important for adaptation to low temperatures. Specific proteasome degradation may be mediated by the observed cold-specific changes in the ubiquitinylation system. Sparse partial least squares regression analysis was applied for protein correlation network analysis using proteins as predictors and Fv/Fm, FW, total lipids, and starch as responses. We applied also Granger causality analysis and revealed correlations between proteins and

  4. Fermentative metabolism of Chlamydomonas reinhardtii

    SciTech Connect

    Gfeller, R.P.; Gibbs, M.

    1984-05-01

    The anaerobic starch breakdown into end-products in the green alga Chlamydomonas reinhardtii F-60 has been investigated in the dark and in the light. The effects of 3-(3,4-dicholorophenyl)-1,1-dimethylurea (DCMU) and carbonyl cyanide-p-trifluoromethoxyphenyl hydrazone (FCCP) on the fermentation in the light have also been investigated. Anaerobic starch breakdown rate (13.1 +/- 3.5 micromoles C per milligram chlorophyll per hour) is increased 2-fold by FCCP in the dark. Light (100 watts per square meter) decreases up to 4-fold the dark rate, an inhibition reversed by FCCP. In the dark, formate, acetate, and ethanol are formed in the ratios of 2.07:1.07:0.91, and account for roughly 100% of the C from the starch. H/sub 2/ production is 0.43 mole per mole glucose in the starch. Glycerol, D-lactate, and CO/sub 2/ have been detected in minor amounts. In the light, with DCMU and FCCP present, acetate is produced in a 1:1 ratio to formate, and H/sub 2/ evolution is 2.13 moles per mole glucose. When FCCP only is present, acetate production is lower, and CO/sub 2/ and H/sub 2/ evolutions is 1.60 and 4.73 moles per mole glucose, respectively. When DCMU alone is present, CO/sub 2/ and H/sub 2/ photoevolution is higher than in the dark. Without DCMU, CO/sub 2/ and H/sub 2/ evolution is about 100% higher than in its presence. In both conditions, acetate is not formed. In all conditions in the light, ethanol is a minor product. Formate production is least affected by light. The stoichiometry in the dark indicates that starch is degraded via the glycolytic pathway, and pyruvate is broken down into acetyl-CoA and formate. Acetyl-CoA is further dissimilated into acetate and ethanol. In the light, acetate is produced only in the presence of FCCP and, when photophosphorylation is possible, it is used in unidentified reactions. Ethanol formation is inhibited by the light in all conditions. 30 references, 5 figures, 2 tables.

  5. The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions

    PubMed Central

    Merchant, Sabeeha S.; Prochnik, Simon E.; Vallon, Olivier; Harris, Elizabeth H.; Karpowicz, Steven J.; Witman, George B.; Terry, Astrid; Salamov, Asaf; Fritz-Laylin, Lillian K.; Maréchal-Drouard, Laurence; Marshall, Wallace F.; Qu, Liang-Hu; Nelson, David R.; Sanderfoot, Anton A.; Spalding, Martin H.; Kapitonov, Vladimir V.; Ren, Qinghu; Ferris, Patrick; Lindquist, Erika; Shapiro, Harris; Lucas, Susan M.; Grimwood, Jane; Schmutz, Jeremy; Cardol, Pierre; Cerutti, Heriberto; Chanfreau, Guillaume; Chen, Chun-Long; Cognat, Valérie; Croft, Martin T.; Dent, Rachel; Dutcher, Susan; Fernández, Emilio; Ferris, Patrick; Fukuzawa, Hideya; González-Ballester, David; González-Halphen, Diego; Hallmann, Armin; Hanikenne, Marc; Hippler, Michael; Inwood, William; Jabbari, Kamel; Kalanon, Ming; Kuras, Richard; Lefebvre, Paul A.; Lemaire, Stéphane D.; Lobanov, Alexey V.; Lohr, Martin; Manuell, Andrea; Meier, Iris; Mets, Laurens; Mittag, Maria; Mittelmeier, Telsa; Moroney, James V.; Moseley, Jeffrey; Napoli, Carolyn; Nedelcu, Aurora M.; Niyogi, Krishna; Novoselov, Sergey V.; Paulsen, Ian T.; Pazour, Greg; Purton, Saul; Ral, Jean-Philippe; Riaño-Pachón, Diego Mauricio; Riekhof, Wayne; Rymarquis, Linda; Schroda, Michael; Stern, David; Umen, James; Willows, Robert; Wilson, Nedra; Zimmer, Sara Lana; Allmer, Jens; Balk, Janneke; Bisova, Katerina; Chen, Chong-Jian; Elias, Marek; Gendler, Karla; Hauser, Charles; Lamb, Mary Rose; Ledford, Heidi; Long, Joanne C.; Minagawa, Jun; Page, M. Dudley; Pan, Junmin; Pootakham, Wirulda; Roje, Sanja; Rose, Annkatrin; Stahlberg, Eric; Terauchi, Aimee M.; Yang, Pinfen; Ball, Steven; Bowler, Chris; Dieckmann, Carol L.; Gladyshev, Vadim N.; Green, Pamela; Jorgensen, Richard; Mayfield, Stephen; Mueller-Roeber, Bernd; Rajamani, Sathish; Sayre, Richard T.; Brokstein, Peter; Dubchak, Inna; Goodstein, David; Hornick, Leila; Huang, Y. Wayne; Jhaveri, Jinal; Luo, Yigong; Martínez, Diego; Ngau, Wing Chi Abby; Otillar, Bobby; Poliakov, Alexander; Porter, Aaron; Szajkowski, Lukasz; Werner, Gregory; Zhou, Kemin; Grigoriev, Igor V.; Rokhsar, Daniel S.; Grossman, Arthur R.

    2010-01-01

    Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella. PMID:17932292

  6. The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions

    SciTech Connect

    Merchant, Sabeeha S

    2007-04-09

    Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the 120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella.

  7. Phase-dependent forcing and synchronization in the three-sphere model of Chlamydomonas

    NASA Astrophysics Data System (ADS)

    Bennett, Rachel R.; Golestanian, Ramin

    2013-07-01

    The green alga Chlamydomonas swims with synchronized beating of its two flagella, and is experimentally observed to exhibit run-and-tumble behaviour similar to bacteria. Recently, we studied a simple hydrodynamic three-sphere model of Chlamydomonas with a phase-dependent driving force that can produce run-and-tumble behaviour when intrinsic noise is added, due to the nonlinear mechanics of the system. Here, we consider the noiseless case and explore numerically the parameter space in the driving force profiles, which determine whether or not the synchronized state evolves from a given initial condition, as well as the stability of the synchronized state. We find that phase-dependent forcing, or a beat pattern, is necessary for stable synchronization in the geometry we work with. The phase-dependent forcing allows this simple model of Chlamydomonas to produce a rich variety of behaviours.

  8. Phylogenomic analysis of the Chlamydomonas genome unmasks proteins potentially involved in photosynthetic function and regulation

    PubMed Central

    Karpowicz, Steven J.; Heinnickel, Mark; Dewez, David; Hamel, Blaise; Dent, Rachel; Niyogi, Krishna K.; Johnson, Xenie; Alric, Jean; Wollman, Francis-André; Li, Huiying; Merchant, Sabeeha S.

    2010-01-01

    Chlamydomonas reinhardtii, a unicellular green alga, has been exploited as a reference organism for identifying proteins and activities associated with the photosynthetic apparatus and the functioning of chloroplasts. Recently, the full genome sequence of Chlamydomonas was generated and a set of gene models, representing all genes on the genome, was developed. Using these gene models, and gene models developed for the genomes of other organisms, a phylogenomic, comparative analysis was performed to identify proteins encoded on the Chlamydomonas genome which were likely involved in chloroplast functions (or specifically associated with the green algal lineage); this set of proteins has been designated the GreenCut. Further analyses of those GreenCut proteins with uncharacterized functions and the generation of mutant strains aberrant for these proteins are beginning to unmask new layers of functionality/regulation that are integrated into the workings of the photosynthetic apparatus. PMID:20490922

  9. Activation of Autophagy by Metals in Chlamydomonas reinhardtii

    PubMed Central

    Pérez-Martín, Marta; Blaby-Haas, Crysten E.; Pérez-Pérez, María Esther; Andrés-Garrido, Ascensión; Blaby, Ian K.; Merchant, Sabeeha S.

    2015-01-01

    Autophagy is an intracellular self-degradation pathway by which eukaryotic cells recycle their own material in response to specific stress conditions. Exposure to high concentrations of metals causes cell damage, although the effect of metal stress on autophagy has not been explored in photosynthetic organisms. In this study, we investigated the effect of metal excess on autophagy in the model unicellular green alga Chlamydomonas reinhardtii. We show in cells treated with nickel an upregulation of ATG8 that is independent of CRR1, a global regulator of copper signaling in Chlamydomonas. A similar effect on ATG8 was observed with copper and cobalt but not with cadmium or mercury ions. Transcriptome sequencing data revealed an increase in the abundance of the protein degradation machinery, including that responsible for autophagy, and a substantial overlap of that increased abundance with the hydrogen peroxide response in cells treated with nickel ions. Thus, our results indicate that metal stress triggers autophagy in Chlamydomonas and suggest that excess nickel may cause oxidative damage, which in turn activates degradative pathways, including autophagy, to clear impaired components and recover cellular homeostasis. PMID:26163317

  10. Activation of Autophagy by Metals in Chlamydomonas reinhardtii.

    PubMed

    Pérez-Martín, Marta; Blaby-Haas, Crysten E; Pérez-Pérez, María Esther; Andrés-Garrido, Ascensión; Blaby, Ian K; Merchant, Sabeeha S; Crespo, José L

    2015-09-01

    Autophagy is an intracellular self-degradation pathway by which eukaryotic cells recycle their own material in response to specific stress conditions. Exposure to high concentrations of metals causes cell damage, although the effect of metal stress on autophagy has not been explored in photosynthetic organisms. In this study, we investigated the effect of metal excess on autophagy in the model unicellular green alga Chlamydomonas reinhardtii. We show in cells treated with nickel an upregulation of ATG8 that is independent of CRR1, a global regulator of copper signaling in Chlamydomonas. A similar effect on ATG8 was observed with copper and cobalt but not with cadmium or mercury ions. Transcriptome sequencing data revealed an increase in the abundance of the protein degradation machinery, including that responsible for autophagy, and a substantial overlap of that increased abundance with the hydrogen peroxide response in cells treated with nickel ions. Thus, our results indicate that metal stress triggers autophagy in Chlamydomonas and suggest that excess nickel may cause oxidative damage, which in turn activates degradative pathways, including autophagy, to clear impaired components and recover cellular homeostasis. PMID:26163317

  11. Similar relative mutation rates in the three genetic compartments of Mesostigma and Chlamydomonas.

    PubMed

    Hua, Jimeng; Smith, David Roy; Borza, Tudor; Lee, Robert W

    2012-01-01

    Levels of nucleotide substitution at silent sites in organelle versus nuclear DNAs have been used to estimate relative mutation rates among these compartments and explain lineage-specific features of genome evolution. Synonymous substitution divergence values in animals suggest that the rate of mutation in the mitochondrial DNA is 10-50 times higher than that of the nuclear DNA, whereas overall data for most seed plants support relative mutation rates in mitochondrial, plastid, and nuclear DNAs of 1:3:10. Little is known about relative mutation rates in green algae, as substitution rate data is limited to only the mitochondrial and nuclear genomes of the chlorophyte Chlamydomonas. Here, we measure silent-site substitution rates in the plastid DNA of Chlamydomonas and the three genetic compartments of the streptophyte green alga Mesostigma. In contrast to the situation in animals and land plants, our results support similar relative mutation rates among the three genetic compartments of both Chlamydomonas and Mesostigma. These data are discussed in relation to published intra-species genetic diversity data for the three genetic compartments of Chlamydomonas and are ultimately used to address contemporary hypotheses on the organelle genome evolution. To guide future work, we describe evolutionary divergence data of all publically available Mesostigma viride strains and identify, for the first time, three distinct lineages of Mesostigma. PMID:21621456

  12. Inhibition of Target of Rapamycin Signaling and Stress Activate Autophagy in Chlamydomonas reinhardtii1[W

    PubMed Central

    Pérez-Pérez, María Esther; Florencio, Francisco J.; Crespo, José L.

    2010-01-01

    Autophagy is a catabolic membrane-trafficking process whereby cells recycle cytosolic proteins and organelles under stress conditions or during development. This degradative process is mediated by autophagy-related (ATG) proteins that have been described in yeast, animals, and more recently in plants. In this study, we report the molecular characterization of autophagy in the unicellular green alga Chlamydomonas reinhardtii. We demonstrate that the ATG8 protein from Chlamydomonas (CrATG8) is functionally conserved and may be used as a molecular autophagy marker. Like yeast ATG8, CrATG8 is cleaved at the carboxyl-terminal conserved glycine and is associated with membranes in Chlamydomonas. Cell aging or different stresses such as nutrient limitation, oxidative stress, or the accumulation of misfolded proteins in the endoplasmic reticulum caused an increase in CrATG8 abundance as well as the detection of modified forms of this protein, both landmarks of autophagy activation. Furthermore, rapamycin-mediated inhibition of the Target of Rapamycin signaling pathway, a major regulator of autophagy in eukaryotes, results in identical effects on CrATG8 and a relocalization of this protein in Chlamydomonas cells similar to the one observed upon nutrient limitation. Thus, our findings indicate that Chlamydomonas cells may respond to stress conditions by inducing autophagy via Target of Rapamycin signaling modulation. PMID:20107021

  13. Effective viscosity of non-gravitactic Chlamydomonas Reinhardtii microswimmer suspensions

    NASA Astrophysics Data System (ADS)

    Mussler, Matthias; Rafaï, Salima; Peyla, Philippe; Wagner, Christian

    2013-03-01

    Active microswimmers are known to affect the macroscopic viscosity of suspensions in a more complex manner than passive particles. For puller-like microswimmers an increase in the viscosity has been observed. It has been suggested that the persistence of the orientation of the microswimmers hinders the rotation that is normally caused by the vorticity. It was previously shown that some sorts of algae are bottom-heavy swimmers, i.e., their centre of mass is not located in the centre of the body. In this way, the algae affect the vorticity of the flow when they are perpendicularly oriented to the axis of gravity. This orientation of gravity to vorticity is given in a rheometer that is equipped with a cone-plate geometry. Here we present measurements of the viscosity both in a cone-plate and a Taylor-Couette cell. The two set-ups yielded the same increase in viscosity although the axis of gravitation in the Taylor-Couette cell is parallel to the direction of vorticity. In a complementary experiment we tested the orientation of the direction of swimming through microscopic observation of single Chlamydomonas reinhardtii and could not identify a preferred orientation, i.e., our specific strain of Chlamydomonas reinhardtii are not bottom-heavy swimmers. We thus conclude that bottom heaviness is not a prerequisite for the increase of viscosity and that the effect of gravity on the rheology of our strain of Chlamydomonas reinhardtii is negligible. This finding reopens the question of whether the origin of persistence in the orientation of cells is actually responsible for the increased viscosity of the suspension.

  14. The Study of Algae

    ERIC Educational Resources Information Center

    Rushforth, Samuel R.

    1977-01-01

    Included in this introduction to the study of algae are drawings of commonly encountered freshwater algae, a summary of the importance of algae, descriptions of the seven major groups of algae, and techniques for collection and study of algae. (CS)

  15. Enhanced accumulation of PCB congeners by Baltic Sea blue mussels, Mytilus edulis, with increased algae enrichment

    SciTech Connect

    Gilek, M.; Bjoerk, M.; Broman, D.; Kautsky, N.; Naef, C.

    1996-09-01

    The objective of this study was to examine if natural variations in the quantity of phytoplankton-derived particulate and dissolved organic carbon influences the accumulation of polychlorinated biphenyls (PCBs) in the tissues of Baltic Sea blue mussels (Mytilus edulis L.). In a laboratory flow-through experiment the authors exposed M. edulis to the technical PCB mixture Aroclor{reg_sign} 1248 for 21 d at three different enrichments of the unicellular green algae Chlamydomonas sp., 0.10, 0.16, and 0.32 mg particulate organic carbon (POC)/L. Tissue and water concentrations were determined for seven PCB congeners and 21-d bioaccumulation factors were calculated against total water concentrations. Contrary to what would be expected, an increase in algae enrichment from 0.10 to 0.32 mg POC/L resulted in an enhanced PCB accumulation by a factor of approx. 2. This increase in PCB accumulation was more pronounced for PCB congeners with lower hydrophobicity. These observations have implications for the design of laboratory accumulation studies and potentially for PCB accumulation and cycling in field populations of suspension-feeding mussels in response to changes in eutrophication status.

  16. Plectin-like proteins are present in cells of Chlamydomonas eugametos (Volvocales).

    PubMed

    Hendrychová, J; Vítová, M; Bisová, K; Wiche, G; Zachleder, V

    2002-01-01

    Using both monoclonal and polyclonal antibodies against mammalian plectin (multifunctional protein cross-linking cytoskeletal structures, mainly intermediate filaments, in mammalian cells), several putative isoforms of plectin-like proteins were found in protein extracts from the green alga Chlamydomonas eugametos (Volvocales). Immunofluorescence and immunoblotting revealed that some of the plectin-like proteins were present in perinuclear region or localized near the cell wall, probably being attached to the cytoplasmic membrane. PMID:12503400

  17. High-fidelity phototaxis in biflagellate algae

    NASA Astrophysics Data System (ADS)

    Leptos, Kyriacos; Chioccioli, Maurizio; Furlan, Silvano; Pesci, Adriana; Goldstein, Raymond

    2015-11-01

    The single-cell alga Chlamydomonas reinhardtii is a motile biflagellate that can swim towards light for its photosynthetic requirements, a behavior referred to as phototaxis. The cell responds upon light stimulation through its rudimentary eye - the eyespot - by changing the beating amplitude of its two flagella accordingly - a process called the photoresponse. All this occurs in a coordinated fashion as Chlamydomonas spins about its body axis while swimming, thus experiencing oscillating intensities of light. We use high-speed video microscopy to measure the flagellar dynamics of the photoresponse on immobilized cells and interpret the results with a mathematical model of adaptation similar to that used previously for Volvox. These results are incorporated into a model of phototactic steering to yield trajectories that are compared to those obtained by three-dimensional tracking. Implications of these results for the evolution of multicellularity in the Volvocales are discussed.

  18. Low oxygen levels contribute to improve photohydrogen production in mixotrophic non-stressed Chlamydomonas cultures

    SciTech Connect

    Jurado-Oller, Jose Luis; Dubini, Alexandra; Galvan, Aurora; Fernandez, Emilio; Gonzalez-Ballester, David

    2015-09-17

    Currently, hydrogen fuel is derived mainly from fossil fuels, but there is an increasing interest in clean and sustainable technologies for hydrogen production. In this context, the ability of some photosynthetic microorganisms, particularly cyanobacteria and microalgae, to produce hydrogen is a promising alternative for renewable, clean-energy production. Among a diverse array of photosynthetic microorganisms able to produce hydrogen, the green algae Chlamydomonas reinhardtii is the model organism widely used to study hydrogen production. Furthermore, the well-known fact that acetate-containing medium enhances hydrogen production in this algae, little is known about the precise role of acetate during this process.

  19. Low oxygen levels contribute to improve photohydrogen production in mixotrophic non-stressed Chlamydomonas cultures

    DOE PAGESBeta

    Jurado-Oller, Jose Luis; Dubini, Alexandra; Galvan, Aurora; Fernandez, Emilio; Gonzalez-Ballester, David

    2015-09-17

    Currently, hydrogen fuel is derived mainly from fossil fuels, but there is an increasing interest in clean and sustainable technologies for hydrogen production. In this context, the ability of some photosynthetic microorganisms, particularly cyanobacteria and microalgae, to produce hydrogen is a promising alternative for renewable, clean-energy production. Among a diverse array of photosynthetic microorganisms able to produce hydrogen, the green algae Chlamydomonas reinhardtii is the model organism widely used to study hydrogen production. Furthermore, the well-known fact that acetate-containing medium enhances hydrogen production in this algae, little is known about the precise role of acetate during this process.

  20. Functional Specificity of Cardiolipin Synthase Revealed by the Identification of a Cardiolipin Synthase CrCLS1 in Chlamydomonas reinhardtii

    PubMed Central

    Hung, Chun-Hsien; Kobayashi, Koichi; Wada, Hajime; Nakamura, Yuki

    2016-01-01

    Phosphatidylglycerol (PG) and cardiolipin (CL) are two essential classes of phospholipid in plants and algae. Phosphatidylglycerophosphate synthase (PGPS) and cardiolipin synthase (CLS) involved in the biosynthesis of PG and CL belong to CDP-alcohol phosphotransferase and share overall amino acid sequence homology. However, it remains elusive whether PGPS and CLS are functionally distinct in vivo. Here, we report identification of a gene encoding CLS in Chlamydomonas reinhardtii, CrCLS1, and its functional compatibility. Whereas CrCLS1 did not complement the growth phenotype of a PGPS mutant of Synechocystis sp. PCC 6803, it rescued the temperature-sensitive growth phenotype, growth profile with different carbon sources, phospholipid composition and enzyme activity of Δcrd1, a CLS mutant of Saccharomyces cerevisiae. These results suggest that CrCLS1 encodes a functional CLS of C. reinhardtii as the first identified algal CLS, whose enzyme function is distinct from that of PGPSs from C. reinhardtii. Comparison of CDP-alcohol phosphotransferase motif between PGPS and CLS among different species revealed a possible additional motif that might define the substrate specificity of these closely related enzymes. PMID:26793177

  1. Effect of Interactions Among Algae on Nitrogen Fixation by Blue-Green Algae (Cyanobacteria) in Flooded Soils

    PubMed Central

    Wilson, John T.; Greene, Sarah; Alexander, Martin

    1979-01-01

    Nitrogen fixation (C2H2 reduction) by algae in flooded soil was limited by interactions within the algal community. Nitrogen fixation by either indigenous algae or Tolypothrix tenuis was reduced severalfold by a dense suspension of the green alga Nephrocytium sp. Similarly, interactions between the nitrogen-fixing alga (cyanobacterium) Aulosira 68 and natural densities of indigenous algae limited nitrogen-fixing activity in one of two soils examined. This was demonstrated by developing a variant of Aulosira 68 that was resistant to the herbicide simetryne at concentrations that prevented development of indigenous algae. More nitrogen was fixed by the resistant variant in flooded soil containing herbicide than was fixed in herbicide-free soil by either the indigenous algae or indigenous algae plus the parent strain of Aulosira. Interference from indigenous algae may hamper the development of nitrogen-fixing algae introduced into rice fields in attempts to increase biological nitrogen fixation. PMID:16345463

  2. O2 Uptake in the Light in Chlamydomonas

    PubMed Central

    Peltier, Gilles; Thibault, Pierre

    1985-01-01

    The nature of the process responsible for the stationary O2 uptake occurring in the light under saturating CO2 concentration in Chlamydomonas reinhardii has been investigated. For this purpose, a mass spectrometer with a membrane inlet system was used to measure O2 uptake and evolution in the algal suspension. First, we observed that the O2 uptake rate was constant (about 0.5 micromoles of O2 per milligram chlorophyll per minute) during a light to dark transition and was not affected by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Salicylhydroxamic acid had no effect on O2 uptake in the dark or in the light, but was found to have the same inhibitory effect either in the dark or in the light when added to cyanide-treated algae. The stimulation of the O2 uptake rate due to the uncoupling effect of carbonyl cyanide m-chlorophenylhydrazone was about the same in the dark or in the light. From these results, we conclude that mitochondrial respiration is maintained during illumination and therefore is not inhibited by high ATP levels. Another conclusion is that in conditions where photorespiration is absent, no other light-dependent O2 uptake process occurs. If Mehler reactions are involved, in Chlamydomonas, under conditions where both photosynthetic carbon oxidation and reduction cycles cannot operate (as in cyanide-treated algae), their occurrence in photosynthesizing algae either under saturating CO2 concentration or at the CO2 compensation point appears very unlikely. The comparison with the situation previously reported in Scenedesmus (R. J. Radmer and B. Kok 1976 Plant Physiol 58: 336-340) suggests that different O2 uptake processes might be present in these two algal species. PMID:16664375

  3. Nutrient removal from horticultural wastewater by benthic filamentous algae Klebsormidium sp., Stigeoclonium spp. and their communities: From laboratory flask to outdoor Algal Turf Scrubber (ATS).

    PubMed

    Liu, Junzhuo; Danneels, Bram; Vanormelingen, Pieter; Vyverman, Wim

    2016-04-01

    Benthic filamentous algae have evident advantages in wastewater treatment over unicellular microalgae, including the ease in harvesting and resistance to predation. To assess the potentials of benthic filamentous algae in treating horticultural wastewater under natural conditions in Belgium, three strains and their mixture with naturally wastewater-borne microalgae were cultivated in 250 ml Erlenmeyer flasks in laboratory as well as in 1 m(2) scale outdoor Algal Turf Scrubber (ATS) with different flow rates. Stigeoclonium competed well with the natural wastewater-borne microalgae and contributed to most of the biomass production both in Erlenmeyer flasks and outdoor ATS at flow rates of 2-6 L min(-1) (water velocity 3-9 cm s(-1)), while Klebsormidium was not suitable for growing in horticultural wastewater under the tested conditions. Flow rate had great effects on biomass production and nitrogen removal, while phosphorus removal was less influenced by flow rate due to other mechanisms than assimilation by algae. PMID:26841229

  4. Chlamydomonas reinhardtii PsbS Protein Is Functional and Accumulates Rapidly and Transiently under High Light.

    PubMed

    Tibiletti, Tania; Auroy, Pascaline; Peltier, Gilles; Caffarri, Stefano

    2016-08-01

    Photosynthetic organisms must respond to excess light in order to avoid photo-oxidative stress. In plants and green algae the fastest response to high light is non-photochemical quenching (NPQ), a process that allows the safe dissipation of the excess energy as heat. This phenomenon is triggered by the low luminal pH generated by photosynthetic electron transport. In vascular plants the main sensor of the low pH is the PsbS protein, while in the green alga Chlamydomonas reinhardtii LhcSR proteins appear to be exclusively responsible for this role. Interestingly, Chlamydomonas also possesses two PsbS genes, but so far the PsbS protein has not been detected and its biological function is unknown. Here, we reinvestigated the kinetics of gene expression and PsbS and LhcSR3 accumulation in Chlamydomonas during high light stress. We found that, unlike LhcSR3, PsbS accumulates very rapidly but only transiently. In order to determine the role of PsbS in NPQ and photoprotection in Chlamydomonas, we generated transplastomic strains expressing the algal or the Arabidopsis psbS gene optimized for plastid expression. Both PsbS proteins showed the ability to increase NPQ in Chlamydomonas wild-type and npq4 (lacking LhcSR3) backgrounds, but no clear photoprotection activity was observed. Quantification of PsbS and LhcSR3 in vivo indicates that PsbS is much less abundant than LhcSR3 during high light stress. Moreover, LhcSR3, unlike PsbS, also accumulates during other stress conditions. The possible role of PsbS in photoprotection is discussed. PMID:27329221

  5. Evolution of sex and mating loci: an expanded view from Volvocine algae.

    PubMed

    Umen, James G

    2011-12-01

    Sexual reproduction in Volvocine algae coevolved with the acquisition of multicellularity. Unicellular genera such as Chlamydomonas and small colonial genera from this group have classical mating types with equal-sized gametes, while larger multicellular genera such as Volvox have differentiated males and females that produce sperm and eggs respectively. Newly available sequence from the Volvox and Chlamydomonas genomes and mating loci open up the potential to investigate how sex-determining regions co-evolve with major changes in development and sexual reproduction. The expanded size and sequence divergence between the male and female haplotypes of the Volvox mating locus (MT) not only provide insights into how the colonial Volvocine algae might have evolved sexual dimorphism, but also raise questions about why the putative ancestral-like MT locus in Chlamydomonas shows less divergence between haplotypes than expected. PMID:22035946

  6. 13th International Conference on Chlamydomonas

    SciTech Connect

    Silflow, Carolyn D.

    2014-03-11

    The 13th International Conference on Chlamydomonas (EMBO Workshop on the Cell and Molecular Biology of Chlamydomonas) was held May 27 to June 1, 2008 in Hyeres, France. The conference was the biennial meeting for all researchers studying the green algal systems Chlamydomonas and Volvox. The conference brought together approximately 200 investigators from around the world (North America, Asia, Europe and Australia) representing different fields and disciplines (cell biology, genetics, biochemistry, biophysics, plant physiology, genomics). It provided an opportunity for investigators from different countries to share methodologies and to discuss recent results with a focus on the Chlamydomonas experimental system.

  7. Effect of oxygen and temperature on the efficiency of photosynthetic carbon assimilation in two microscopic algae.

    PubMed

    Coleman, J R; Colman, B

    1980-05-01

    The CO(2) compensation points of Coccochloris peniocystis, a blue-green alga and Chlamydomonas reinhardtii, a green alga, were determined at pH 8.0 in a closed system by a gas chromatographic technique. The compensation point of Chlamydomonas increased markedly with temperature, rising from 0.79 microliter per liter CO(2) at 15 C to 2.5 microliters per liter CO(2) at 35 C. In contrast, the compensation point of Coccochloris at 20 C was 0.71 microliter per liter CO(2) and rose to only 0.95 microliter per liter CO(2) at 40 C.The compensation point of the green alga was significantly reduced at low O(2) concentrations (1 to 2%) when measured over the temperature range of 15 to 35 C. The compensation point of the blue-green alga, over the temperature range of 20 to 40 C, was unaffected by lowering the O(2) concentration.The whole cell CO(2) affinity of Chlamydomonas decreased substantially with increasing temperature at 21% O(2) whereas little change was observed over the same temperature regime when the CO(2) affinity was determined at O(2) concentrations of 1 to 2%. The CO(2) affinity of Coccochloris did not decrease significantly with either increasing temperature or O(2) concentration.These results suggest that while photorespiration is undetectable in Coccochloris some photorespiratory CO(2) release occurs in Chlamydomonas. PMID:16661319

  8. Individual Flagellar Waveform Affects Collective Behavior of Chlamydomonas reinhardtii.

    PubMed

    Kage, Azusa; Mogami, Yoshihiro

    2015-08-01

    Bioconvection is a form of collective motion that occurs spontaneously in the suspension of swimming microorganisms. In a previous study, we quantitatively described the "pattern transition," a phase transition phenomenon that so far has exclusively been observed in bioconvection of the unicellular green alga Chlamydomonas. We suggested that the transition could be induced by changes in the balance between the gravitational and shear-induced torques, both of which act to determine the orientation of the organism in the shear flow. As both of the torques should be affected by the geometry of the Chlamydomonas cell, alteration in the flagellar waveform might change the extent of torque generation by altering overall geometry of the cell. Based on this working hypothesis, we examined bioconvection behavior of two flagellar mutants of Chlamydomonas reinhardtii, ida1 and oda2, making reference to the wild type. Flagella of ida1 beat with an abnormal waveform, while flagella of oda2 show a normal waveform but lower beat frequency. As a result, both mutants had swimming speed of less than 50% of the wild type. ida1 formed bioconvection patterns with smaller spacing than those of wild type and oda2. Two-axis view revealed the periodic movement of the settling blobs of ida1, while oda2 showed qualitatively similar behavior to that of wild type. Unexpectedly, ida1 showed stronger negative gravitaxis than did wild type, while oda2 showed relatively weak gravitaxis. These findings suggest that flagellar waveform, not swimming speed or beat frequency, strongly affect bioconvection behavior in C. reinhardtii. PMID:26245228

  9. Molecular techniques to interrogate and edit the Chlamydomonas nuclear genome.

    PubMed

    Jinkerson, Robert E; Jonikas, Martin C

    2015-05-01

    The success of the green alga Chlamydomonas reinhardtii as a model organism is to a large extent due to the wide range of molecular techniques that are available for its characterization. Here, we review some of the techniques currently used to modify and interrogate the C. reinhardtii nuclear genome and explore several technologies under development. Nuclear mutants can be generated with ultraviolet (UV) light and chemical mutagens, or by insertional mutagenesis. Nuclear transformation methods include biolistic delivery, agitation with glass beads, and electroporation. Transforming DNA integrates into the genome at random sites, and multiple strategies exist for mapping insertion sites. A limited number of studies have demonstrated targeted modification of the nuclear genome by approaches such as zinc-finger nucleases and homologous recombination. RNA interference is widely used to knock down expression levels of nuclear genes. A wide assortment of transgenes has been successfully expressed in the Chlamydomonas nuclear genome, including transformation markers, fluorescent proteins, reporter genes, epitope tagged proteins, and even therapeutic proteins. Optimized expression constructs and strains help transgene expression. Emerging technologies such as the CRISPR/Cas9 system, high-throughput mutant identification, and a whole-genome knockout library are being developed for this organism. We discuss how these advances will propel future investigations. PMID:25704665

  10. Propulsive Forces on the Flagellum during Locomotion of Chlamydomonas reinhardtii

    PubMed Central

    Bayly, P.V.; Lewis, B.L.; Ranz, E.C.; Okamoto, R.J.; Pless, R.B.; Dutcher, S.K.

    2011-01-01

    The distributed propulsive forces exerted on the flagellum of the swimming alga Chlamydomonas reinhardtii by surrounding fluid were estimated from experimental image data. Images of uniflagellate mutant Chlamydomonas cells were obtained at 350 frames/s with 125-nm spatial resolution, and the motion of the cell body and the flagellum were analyzed in the context of low-Reynolds-number fluid mechanics. Wild-type uniflagellate cells, as well as uniflagellate cells lacking inner dynein arms (ida3) or outer dynein arms (oda2) were studied. Ida3 cells exhibit stunted flagellar waveforms, whereas oda2 cells beat with lower frequency. Image registration and sorting algorithms provided high-resolution estimates of the motion of the cell body, as well as detailed kinematics of the flagellum. The swimming cell was modeled as an ellipsoid in Stokes flow, propelled by viscous forces on the flagellum. The normal and tangential components of force on the flagellum (fN and fT) were related by resistive coefficients (CN and CT) to the corresponding components of velocity (VN and VT).The values of these coefficients were estimated by satisfying equilibrium requirements for force and torque on the cell. The estimated values of the resistive coefficients are consistent among all three genotypes and similar to theoretical predictions. PMID:21641317

  11. Blue Light Regulation of Cell Division in Chlamydomonas reinhardtii 1

    PubMed Central

    Münzner, Petra; Voigt, Jürgen

    1992-01-01

    A delay in cell division was observed when synchronized cultures of the unicellular green alga Chlamydomonas reinhardtii growing under heterotrophic conditions were exposed to white light during the second half of the growth period. This effect was also observed when photosynthesis was blocked by addition of the photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Light pulses of 10 minutes were sufficient to induce a delay in cell division in the presence or absence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. A delay in cell division was induced by blue light but not by illumination with red or far-red light. The equal intensity action spectrum revealed two peaks at 400 and 500 nm. PMID:16669046

  12. Effects of light on gravitaxis and velocity in Chlamydomonas reinhardtii.

    PubMed

    Sineshchekov, O; Lebert, M; Hader, D P

    2000-09-01

    The effects of light on gravitaxis and velocity in the bi-flagellated green alga Chlamydomonas reinhardtii were investigated using a real time automatic tracking system. Three distinct light effects on gravitaxis and velocity with parallel kinetics were found. Photosynthetically active continuous red light reversibly enhances the swimming velocity and increases or decreases the precision of gravitaxis, depending on its initial level. Blue light flashes induce fast transient increases in velocity immediately after the photophobic response, and transiently decrease or even reverse negative gravitaxis. The calcium dependence of this response, its fluence-response curve and its spectral characteristics strongly suggest the participation of chlamy-rhodopsin in this effect. The third response, a prolonged activation of velocity and gravitaxis, is also induced by blue light flashes, which can be observed even in calcium-free medium. PMID:12090268

  13. A TRP conductance modulates repolarization after sensory-dependent depolarization in Chlamydomonas reinhardtii

    PubMed Central

    Arias-Darraz, Luis; Colenso, Charlotte K; Veliz, Luis A; Vivar, Juan P; Cardenas, Sylvana; Brauchi, Sebastian

    2015-01-01

    Sensory integration is vital for motile organisms constantly exposed to changing surroundings. Chlamydomonas reinhardtii is a single-celled green alga found swimming in freshwater. In this type of alga, sensory input is first detected by membrane receptors located in the cell body, and then transduced to the beating cilia by membrane depolarization. Many components of the machinery associated with sensory integration in C. reinhardtii, such as chemoreceptors and repolarization-associated channels, are yet uncharacterized. TRP channels are known mediators for cellular sensing in animal cells and it has been suggested that the C. reinhardtii genome encodes for a set of TRP proteins. Here, by combining behavioral studies with electrophysiological experiments conducted on both population and single alga, we test whether TRP channel blockers affect algal swimming behavior. Our results suggest that a TRP conductance is associated to the repolarization that follows a depolarizing receptor potential, highlighting a primitive function of TRP proteins. PMID:26186626

  14. Developing molecular tools for Chlamydomonas reinhardtii

    NASA Astrophysics Data System (ADS)

    Noor-Mohammadi, Samaneh

    Microalgae have garnered increasing interest over the years for their ability to produce compounds ranging from biofuels to neutraceuticals. A main focus of researchers has been to use microalgae as a natural bioreactor for the production of valuable and complex compounds. Recombinant protein expression in the chloroplasts of green algae has recently become more routine; however, the heterologous expression of multiple proteins or complete biosynthetic pathways remains a significant challenge. To take full advantage of these organisms' natural abilities, sophisticated molecular tools are needed to be able to introduce and functionally express multiple gene biosynthetic pathways in its genome. To achieve the above objective, we have sought to establish a method to construct, integrate and express multigene operons in the chloroplast and nuclear genome of the model microalgae Chlamydomonas reinhardtii. Here we show that a modified DNA Assembler approach can be used to rapidly assemble multiple-gene biosynthetic pathways in yeast and then integrate these assembled pathways at a site-specific location in the chloroplast, or by random integration in the nuclear genome of C. reinhardtii. As a proof of concept, this method was used to successfully integrate and functionally express up to three reporter proteins (AphA6, AadA, and GFP) in the chloroplast of C. reinhardtii and up to three reporter proteins (Ble, AphVIII, and GFP) in its nuclear genome. An analysis of the relative gene expression of the engineered strains showed significant differences in the mRNA expression levels of the reporter genes and thus highlights the importance of proper promoter/untranslated-region selection when constructing a target pathway. In addition, this work focuses on expressing the cofactor regeneration enzyme phosphite dehydrogenase (PTDH) in the chloroplast and nuclear genomes of C. reinhardtii. The PTDH enzyme converts phosphite into phosphate and NAD(P)+ into NAD(P)H. The reduced

  15. Rescue of a paralyzed-flagella mutant of Chlamydomonas by transformation

    SciTech Connect

    Diener, D.R.; Curry, A.M.; Johnson, K.A.; Williams, B.D.; Rosenbaum, J.L. ); Lefebvre, P.A. ); Kindle, K.L. )

    1990-08-01

    The biflagellate alga Chlamydomonas has been used extensively in the genetic and biochemical analysis of flagellar assembly and motility. The authors have restored motility to a paralyzed-flagella mutant of Chlamydomonas by transforming with the corresponding wild-type gene. A nitrate reductase-deficient paralyzed-flagella strain, nit1-305 pf-14, carrying mutations in the genes for nitrate reductase and radial spoke protein 3, was transformed with wild-type copies of both genes. Two-thirds of the cells that survived nitrate selection also regained motility, indicating that they had been transformed with both the nitrate reductase and radial spoke protein 3 genes. Transformants typically contained multiple copies of both genes, genetically linked to each other, but not linked to the original mutant loci. Complementation of paralyzed-flagella mutants by transformation is a powerful tool for investigating flagellar assembly and function.

  16. Antimicrobial cocktails to control bacterial and fungal contamination in Chlamydomonas reinhardtii cultures.

    PubMed

    Wang, Liang; Yang, Fengyuan; Chen, Huiyi; Fan, Zhiyue; Zhou, Yongkang; Lu, Jun; Zheng, Yuanlin

    2016-01-01

    Chlamydomonas reinhardtii is a unicellular green alga widely used for research in photosynthesis, cell cycle regulation, ciliary biogenesis, and other physiological processes. Sterile cultures are needed for these studies, but contamination from bacteria and fungi occurs frequently. Although the One-shot Solution cocktail consisting of carbendazim, ampicillin, and cefotaxime has been developed for removing these contaminants from algal cultures, it is not always effective. Here we report two new antimicrobial cocktails for treating mixed bacterial and fungal contamination of Chlamydomonas cultures. A combination of the bactericide nalidixic acid with one of two fungicides, azoxystrobin or tebuconazole, was more effective than the One-shot Solution cocktail. In some of our tests, we find that alternating use of our new cocktails with One-shot Solution is needed to remove obstinate contaminants. PMID:26956093

  17. Limited photosynthetic electron flow but no CO2 fixation in Chlamydomonas mutants lacking photosystem I.

    PubMed

    Cournac, L; Redding, K; Bennoun, P; Peltier, G

    1997-10-13

    By measuring O2 and CO2 exchange in mutants of the green alga Chlamydomonas reinhardtii in which genes encoding the reaction center of photosystem I (psaA or psaB) have been deleted, we found that a photosystem II-dependent electron flow using O2 as the final acceptor can be sustained in the light. However, in contrast with recent reports using other Chlamydomonas mutants (B4 and F8), we show here that CO2 fixation does not occur in the absence of photosystem I. By deleting the psaA gene in both B4 and F8 strains, we conclude that the ability of these mutants to fix CO2 in the light is due to the presence of residual amounts of photosystem I. PMID:9369234

  18. Group I introns interrupt the chloroplast psaB and psbC and the mitochondrial rrnL gene in Chlamydomonas.

    PubMed Central

    Turmel, M; Mercier, J P; Côté, M J

    1993-01-01

    The polymerase chain reaction was used to identify novel IAI subgroup introns in cpDNA-enriched preparations from the interfertile green algae Chlamydomonas eugametos and Chlamydomonas moewusii. These experiments along with sequence analysis disclosed the presence, in both green algae, of a single IA1 intron in the psaB gene and of two group I introns (IA2 and IA1) in the psbC gene. In addition, two group I introns (IA1 and IB4) were found in the peptidyltransferase region of the mitochondrial large subunit rRNA gene at the same positions as previously reported Chlamydomonas chloroplast introns. The 188 bp segment preceding the first mitochondrial intron revealed extensive sequence similarity to the distantly spaced rRNA-coding modules L7 and L8 in the Chlamydomonas reinhardtii mitochondrial DNA, indicating that these two modules have undergone rearrangements in Chlamydomonas. The IA1 introns in psaB and psbC were found to be related in sequence to the first intron in the C. moewusii chloroplast psbA gene. The similarity between the former introns extends to the immediate 5' flanking exon sequence, suggesting that group I intron transposition occurred from one of the two genes to the other through reverse splicing. PMID:7504814

  19. Identification and molecular characterization of a novel Chlamydomonas reinhardtii mutant defective in chlorophyll biosynthesis

    PubMed Central

    Mitra, Mautusi

    2013-01-01

    The green micro-alga Chlamydomonas reinhardtii is an elegant model organism to study all aspects of oxygenic photosynthesis. Chlorophyll (Chl) and heme are major tetrapyrroles that play an essential role in energy metabolism in photosynthetic organisms and are synthesized via a common branched tetrapyrrole biosynthetic pathway. One of the enzymes in the pathway is Mg chelatase (MgChel) which inserts Mg 2+ into protoporphyrin IX (PPIX, proto) to form magnesium-protoporphyrin IX (MgPPIX, Mgproto), the first biosynthetic intermediate in the Chl branch. MgChel is a multimeric enzyme that consists of three subunits designated CHLD, CHLI and CHLH. Plants have two isozymes of CHLI (CHLI1 and CHLI2) which are 70%-81% identical in protein sequences. Although the functional role of CHLI1 is well characterized, that of CHLI2 is not. We have isolated a non-photosynthetic light sensitive mutant 5A7 by random DNA insertional mutagenesis that is devoid of any detectable Chl. PCR based analyses show that 5A7 is missing the CHLI1 gene and at least eight additional functionally uncharacterized genes. 5A7 has an intact CHLI2 gene. Complementation with a functional copy of the CHLI1 gene restored Chl biosynthesis, photo-autotrophic growth and light tolerance in 5A7. We have identified the first chli1 (chli1-1) mutant of Chlamydomonas reinhardtii and in green algae. Our results show that in the wild type Chlamydomonas CHLI2 protein amount is lower than that of CHLI1 and the chli1-1 mutant has a drastic reduction in CHLI2 protein levels although it possesses the CHLI2 gene. Our chli1-1 mutant opens up new avenues to explore the functional roles of CHLI1 and CHLI2 in Chl biosynthesis in Chlamydomonas, which has never been studied before. PMID:24555064

  20. ELLIPTOCHLORIS MARINA SP. NOV. (TREBOUXIOPHYCEAE, CHLOROPHYTA), SYMBIOTIC GREEN ALGA OF THE TEMPERATE PACIFIC SEA ANEMONES ANTHOPLEURA XANTHOGRAMMICA AND A. ELEGANTISSIMA (ANTHOZOA, CNIDARIA)(1).

    PubMed

    Letsch, Molly R; Muller-Parker, Gisèle; Friedl, Thomas; Lewis, Louise A

    2009-10-01

    Symbiotic green algae from two species of intertidal Pacific sea anemones, Anthopleura elegantissima and Anthopleura xanthogrammica, were collected from the northeastern Pacific coast of North America across the known range of the symbiont. Freshly isolated Anthopleura symbionts were used for both morphological and molecular analyses because Anthopleura symbiont cultures were not available. Light and transmission electron microscopy supported previous morphological studies, showing the symbionts consist of spherical unicells from 5 to 10 μm in diameter, with numerous vesicles, and a single bilobed chloroplast. Pyrenoids were not seen in LM, but a thylakoid-free area was observed in TEM, consistent with previous findings. Many algal cells extracted from fresh anemone tissue were observed in the process of division, producing two autospores within a maternal cell wall. The morphology of the green symbionts matches that of Elliptochloris Tscherm.-Woess. Molecular phylogenetic analyses of the nuclear SSU rDNA and the plastid encoded gene for the large subunit of RUBISCO (rbcL) support the monophyly of these green algal symbionts, regardless of host species and geographic origin. Phylogenetically, sequences of the Anthopleura symbionts are nested within the genus Elliptochloris and are distinct from sequences of all other Elliptochloris spp. examined. Given the ecological and phylogenetic distinctions among the green algal symbionts in Anthopleura spp. and the named species of Elliptochloris, we designate the green algal symbionts as a new species, Elliptochloris marina (Trebouxiophyceae, Chlorophyta). PMID:27032358

  1. Synchroma pusillum sp. nov. and other new algal isolates with chloroplast complexes confirm the Synchromophyceae (Ochrophyta) as a widely distributed group of amoeboid algae.

    PubMed

    Schmidt, Maria; Horn, Susanne; Flieger, Kerstin; Ehlers, Katrin; Wilhelm, Christian; Schnetter, Reinhard

    2012-07-01

    Seven new isolates of the heterokont algal class Synchromophyceae are described from coastal habitats of the Atlantic Ocean, including the Caribbean and Mediterranean Seas. All of the new isolates contain chloroplast complexes, a key feature of this group of algae. Morphology, pigments and DNA sequences support a monophyletic grouping of the Synchromophyceae to the exclusion of other Ochrophyta (primarily photosynthetic stramenopiles). Within the Synchromophyceae, two phylogenetic clades based on rbcL and 18S rDNA data were discovered, which differ in cell size and also the number of plastid complexes per cell. Two isolates form a clade with the type species Synchroma grande, while all other isolates form a separate clade, including the newly described species S. pusillum. Further species delineation of the isolates is difficult due to the highly similar morphology and life cycle strategy. Phylogenetic relationships with other genera of the Ochrophyta, such as Leukarachnion and Chlamydomyxa, are apparent and shed light on a heterogeneous branch of heterokont evolution. PMID:22578425

  2. UV-B Perception and Acclimation in Chlamydomonas reinhardtii[OPEN

    PubMed Central

    Chappuis, Richard; Allorent, Guillaume

    2016-01-01

    Plants perceive UV-B, an intrinsic component of sunlight, via a signaling pathway that is mediated by the photoreceptor UV RESISTANCE LOCUS8 (UVR8) and induces UV-B acclimation. To test whether similar UV-B perception mechanisms exist in the evolutionarily distant green alga Chlamydomonas reinhardtii, we identified Chlamydomonas orthologs of UVR8 and the key signaling factor CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). Cr-UVR8 shares sequence and structural similarity to Arabidopsis thaliana UVR8, has conserved tryptophan residues for UV-B photoreception, monomerizes upon UV-B exposure, and interacts with Cr-COP1 in a UV-B-dependent manner. Moreover, Cr-UVR8 can interact with At-COP1 and complement the Arabidopsis uvr8 mutant, demonstrating that it is a functional UV-B photoreceptor. Chlamydomonas shows apparent UV-B acclimation in colony survival and photosynthetic efficiency assays. UV-B exposure, at low levels that induce acclimation, led to broad changes in the Chlamydomonas transcriptome, including in genes related to photosynthesis. Impaired UV-B-induced activation in the Cr-COP1 mutant hit1 indicates that UVR8-COP1 signaling induces transcriptome changes in response to UV-B. Also, hit1 mutants are impaired in UV-B acclimation. Chlamydomonas UV-B acclimation preserved the photosystem II core proteins D1 and D2 under UV-B stress, which mitigated UV-B-induced photoinhibition. These findings highlight the early evolution of UVR8 photoreceptor signaling in the green lineage to induce UV-B acclimation and protection. PMID:27020958

  3. MicroRNAs in a multicellular green alga Volvox carteri.

    PubMed

    Li, Jingrui; Wu, Yang; Qi, Yijun

    2014-01-01

    microRNAs (miRNAs) have emerged as key components in the eukaryotic gene regulatory network. We and others have previously identified many miRNAs in a unicellular green alga, Chlamydomonas reinhardtii. To investigate whether miRNA-mediated gene regulation is a general mechanism in green algae and how miRNAs have been evolved in the green algal lineage, we examined small RNAs in Volvox carteri, a multicellular species in the same family with Chlamydomonas reinhardtii. We identified 174 miRNAs in Volvox, with many of them being highly enriched in gonidia or somatic cells. The targets of the miRNAs were predicted and many of them were subjected to miRNA-mediated cleavage in vivo, suggesting that miRNAs play regulatory roles in the biology of green algae. Our catalog of miRNAs and their targets provides a resource for further studies on the evolution, biological functions, and genomic properties of miRNAs in green algae. PMID:24369344

  4. RESPONSES OF MARINE UNICELLULAR ALGAE TO BROMINATED ORGANIC COMPOUNDS IN SIX GROWTH MEDIA

    EPA Science Inventory

    Marine unicellular algae, Skeletonema costatum, Thalassiosira pseudonana, and Chlorella sp., were exposed to the industrial brominated compounds, tetrabromobisphenol A (TBBP), decabromobiphenyloxide (DBBO), hexabromocyclododecane (HBCD), pentabromomethylbenzene (PBMB), pentabromo...

  5. Dispensability of a sulfolipid for photoautotrophic cell growth and photosynthesis in a marine cyanobacterium, Synechococcus sp. PCC 7002.

    PubMed

    Sato, Norihiro; Kamimura, Ryohei; Tsuzuki, Mikio

    2016-09-01

    Sulfoquinovosyl diacylglycerol, which mainly comprises thylakoid membranes in oxygenic photosynthetic organisms, plays species-dependent roles in freshwater microbes. In this study, a sulfoquinovosyl-diacylglycerol deficient mutant was generated in a cyanobacterium, Synechococcus sp. PCC 7002, for the first time among marine microbes to gain more insight into its physiological significance. The mutation had little deleterious impact on photoautotrophic cell growth, and functional and structural properties of the photosystem II complex. These findings were similar to previous observations for a freshwater cyanobacterium, Synechococcus elongatus PCC 7942, but were distinct from those for another freshwater cyanobacterium, Synechocystis sp. PCC 6803, and a green alga, Chlamydomonas reinhardtii, both of which require sulfoquinovosyl diacylglycerol for cell growth and/or photosystem II. Therefore, the functionality of PSII to dispense with sulfoquinovosyl diacylglycerol in Synechococcus sp. PCC 7002, similar to that in Synechococcus elongatus PCC 7942, seemed to have been excluded from the evolution of the PSII complex from cyanobacteria to green algal chloroplasts. Meanwhile, sulfoquinovosyl diacylglycerol was found to contribute to photoheterotrophic growth of Synechococcus sp. PCC 7002, which revealed a novel species-dependent strategy for utilizing SQDG in physiological processes. PMID:27372425

  6. The oxygen evolving enhancer protein 1 (OEE) of photosystem II in green algae exhibits thioredoxin activity.

    PubMed

    Heide, Heinrich; Kalisz, Henryk M; Follmann, Hartmut

    2004-02-01

    A thioredoxin-like chloroplast protein of the fructosebisphosphatase-stimulating f-type, but with an unusually high molecular mass of 28 kDa has previously been identified and purified to homogeneity in a fractionation scheme for resolution of the acid- and heat-stable, regular-size (12kDa) thioredoxins of the unicellular green algae, Scenedesmus obliquus. An apparently analogous protein of 26 kDa was described in a cyanobacterium, Anabaena sp., but no such large thioredoxin species f exists in the thioredoxin profiles of higher plants. The structure of the 28 kDa protein, which had been envisaged to represent a precursor, or fusion product of the two more specialized, common chloroplast thioredoxins f and m has now been determined by amino acid sequencing. Although it exhibits virtually all the properties and enzyme-modulating activities of a thioredoxin proper this algal protein, surprisingly, does not belong to the thioredoxin family of small redox proteins but is identical with OEE (oxygen evolving enhancer) protein 1, an auxiliary component of the photosystem II manganese cluster. Extracts of Chlorella vulgaris and Chlamydomonas reinhardtii also contain heat-stable protein fractions of 23-26 kDa capable of specifically stimulating chloroplast fructosebisphosphatase in vitro. In contrast, OEE protein 1 from spinach is not able to modulate FbPase or NADP malate dehydrogenase from spinach chloroplasts. A dual function of the OEE protein in algal photosynthesis is envisaged. PMID:15022827

  7. The Purification of the Chlamydomonas reinhardtii chloroplast ClpP complex: additional subunits and structural features

    PubMed Central

    Derrien, Benoît; Majeran, Wojciech; Effantin, Grégory; Ebenezer, Joseph; Friso, Giulia; van Wijk, Klaas J.; Steven, Alasdair C.; Maurizi, Michael R.; Vallon, Olivier

    2012-01-01

    The ClpP peptidase is a major constituent of the proteolytic machinery of bacteria and organelles. The chloroplast ClpP complex is unusual, in that it associates a large number of subunits, one of which (ClpP1) is encoded in the chloroplast, the others in the nucleus. The complexity of these large hetero-oligomeric complexes has been a major difficulty in their overproduction and biochemical characterization. In this paper, we describe the purification of native chloroplast ClpP complex from the green alga Chlamydomonas reinhardtii, using a strain that carries the Strep-tag II at the C-terminus of the ClpP1 subunit. Similar to land plants, the algal complex comprises active and inactive subunits (3 ClpP and 5 ClpR, respectively). Evidence is presented that a sub-complex can be produced by dissociation, comprising ClpP1 and ClpR1, 2, 3 and 4, similar to the ClpR-ring described in land plants. Our Chlamydomonas ClpP preparation also contains two ClpT subunits, ClpT3 and ClpT4, which like the land plant ClpT1 and ClpT2 show 2 Clp-N domains. ClpTs are believed to function in substrate binding and/or assembly of the two heptameric rings. Phylogenetic analysis indicates that ClpT subunits have appeared independently in Chlorophycean algae, in land plants and in dispersed cyanobacterial genomes. Negative staining electron microscopy shows that the Chlamydomonas complex retains the barrel-like shape of homo-oligomeric ClpPs, with 4 additional peripheral masses that we speculate represent either the additional IS1 domain of ClpP1 (a feature unique to algae) or ClpTs or extensions of ClpR subunits PMID:22772861

  8. Isolation and characterization of glutamine synthetase genes in Chlamydomonas reinhardtii.

    PubMed

    Chen, Q; Silflow, C D

    1996-11-01

    To elucidate the role of glutamine synthetase (GS) in nitrogen assimilation in the green alga Chlamydomonas reinhardtii we used maize GS1 (the cytosolic form) and GS2 (the chloroplastic form) cDNAs as hybridization probes to isolate C. reinhardtii cDNA clones. The amino acid sequences derived from the C. reinhardtii clones have extensive homology with GS enzymes from higher plants. A putative amino-terminal transit peptide encoded by the GS2 cDNA suggests that the protein localizes to the chloroplast. Genomic DNA blot analysis indicated that GS1 is encoded by a single gene, whereas two genomic fragments hybridized to the GS2 cDNA probe. All GS2 cDNA clones corresponded to only one of the two GS2 genomic sequences. We provide evidence that ammonium, nitrate, and light regulate GS transcript accumulation in green algae. Our results indicate that the level of GS1 transcripts is repressed by ammonium but induced by nitrate. The level of GS2 transcripts is not affected by ammonium or nitrate. Expression of both GS1 and GS2 genes is regulated by light, but perhaps through different mechanisms. Unlike in higher plants, no decreased level of GS2 transcripts was detected when cells were grown under conditions that repress photorespiration. Analysis of GS transcript levels in mutants with defects in the nitrate assimilation pathway show that nitrate assimilation and ammonium assimilation are regulated independently. PMID:8938407

  9. Characterizing the anaerobic response of Chlamydomonas reinhardtii by quantitative proteomics.

    PubMed

    Terashima, Mia; Specht, Michael; Naumann, Bianca; Hippler, Michael

    2010-07-01

    The versatile metabolism of the green alga Chlamydomonas reinhardtii is reflected in its complex response to anaerobic conditions. The anaerobic response is also remarkable in the context of renewable energy because C. reinhardtii is able to produce hydrogen under anaerobic conditions. To identify proteins involved during anaerobic acclimation as well as to localize proteins and pathways to the powerhouses of the cell, chloroplasts and mitochondria from C. reinhardtii in aerobic and anaerobic (induced by 8 h of argon bubbling) conditions were isolated and analyzed using comparative proteomics. A total of 2315 proteins were identified. Further analysis based on spectral counting clearly localized 606 of these proteins to the chloroplast, including many proteins of the fermentative metabolism. Comparative quantitative analyses were performed with the chloroplast-localized proteins using stable isotopic labeling of amino acids ([(13)C(6)]arginine/[(12)C(6)]arginine in an arginine auxotrophic strain). The quantitative data confirmed proteins previously characterized as induced at the transcript level as well as identified several new proteins of unknown function induced under anaerobic conditions. These proteins of unknown function provide new candidates for further investigation, which could bring insights for the engineering of hydrogen-producing alga strains. PMID:20190198

  10. Novel insights into the function of LHCSR3 in Chlamydomonas reinhardtii

    PubMed Central

    Xue, Huidan; Bergner, Sonja Verena; Scholz, Martin; Hippler, Michael

    2015-01-01

    Light is essential for photosynthesis but excess light is hazardous as it may lead to the formation of reactive oxygen species. Photosynthetic organisms struggle to optimize light utilization and photosynthesis while minimizing photo-oxidative damage. Hereby light to heat dissipation via specialized proteins is a potent mechanism to acclimate toward excess light. In the green alga Chlamydomonas reinhardtii the expression of an ancient light-harvesting protein LHCSR3 enables cells to dissipate harmful excess energy. Herein we summarize newest insights into the function of LHCSR3 from C. reinhardtii. PMID:26237677

  11. Emergent Run-and-Tumble Behavior in a Simple Model of Chlamydomonas with Intrinsic Noise

    NASA Astrophysics Data System (ADS)

    Bennett, Rachel R.; Golestanian, Ramin

    2013-04-01

    Recent experiments on the green alga Chlamydomonas that swims using synchronized beating of a pair of flagella have revealed that it exhibits a run-and-tumble behavior similar to that of bacteria such as E. coli. Using a simple purely hydrodynamic model that incorporates a stroke cycle and an intrinsic Gaussian white noise, we show that a stochastic run-and-tumble behavior could emerge due to the nonlinearity of the combined synchronization-rotation-translation dynamics. Our study suggests that nonlinear mechanics could be a significant contributing factor to how the trajectories of the microorganism are selected.

  12. Cell and molecular biology of Chlamydomonas

    SciTech Connect

    Not Available

    1988-01-01

    This document contains only the abstracts of 92 presentations on the biology of Chlamydomonas. Topics include gene transformations, gene regulation, biosynthetic pathways, cell surfaces, circadian clocks, and the development and structure of the flagellar apparatus. (TEM)

  13. Dissecting the peripheral stalk of the mitochondrial ATP synthase of chlorophycean algae.

    PubMed

    Vázquez-Acevedo, Miriam; Vega-deLuna, Félix; Sánchez-Vásquez, Lorenzo; Colina-Tenorio, Lilia; Remacle, Claire; Cardol, Pierre; Miranda-Astudillo, Héctor; González-Halphen, Diego

    2016-08-01

    The algae Chlamydomonas reinhardtii and Polytomella sp., a green and a colorless member of the chlorophycean lineage respectively, exhibit a highly-stable dimeric mitochondrial F1Fo-ATP synthase (complex V), with a molecular mass of 1600 kDa. Polytomella, lacking both chloroplasts and a cell wall, has greatly facilitated the purification of the algal ATP-synthase. Each monomer of the enzyme has 17 polypeptides, eight of which are the conserved, main functional components, and nine polypeptides (Asa1 to Asa9) unique to chlorophycean algae. These atypical subunits form the two robust peripheral stalks observed in the highly-stable dimer of the algal ATP synthase in several electron-microscopy studies. The topological disposition of the components of the enzyme has been addressed with cross-linking experiments in the isolated complex; generation of subcomplexes by limited dissociation of complex V; detection of subunit-subunit interactions using recombinant subunits; in vitro reconstitution of subcomplexes; silencing of the expression of Asa subunits; and modeling of the overall structural features of the complex by EM image reconstruction. Here, we report that the amphipathic polymer Amphipol A8-35 partially dissociates the enzyme, giving rise to two discrete dimeric subcomplexes, whose compositions were characterized. An updated model for the topological disposition of the 17 polypeptides that constitute the algal enzyme is suggested. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi. PMID:26873638

  14. CO2 Biofixation by the Cyanobacterium Spirulina sp. LEB 18 and the Green Alga Chlorella fusca LEB 111 Grown Using Gas Effluents and Solid Residues of Thermoelectric Origin.

    PubMed

    da Silva Vaz, Bruna; Costa, Jorge Alberto Vieira; de Morais, Michele Greque

    2016-01-01

    The concentration of carbon dioxide (CO2) in the atmosphere has increased from 280 to 400 ppm in the last 10 years, and the coal-fired power plants are responsible for approximately 22 % of these emissions. The burning of fossil fuel also produces a great amount of solid waste that causes serious industrial and environmental problems. The biological processes become interesting alternative in combating pollution and developing new products. The objective of this study was to evaluate the CO2 biofixation potential of microalgae that were grown using gaseous effluents and solid residues of thermoelectric origin. The microalgae Chlorella fusca LEB 111 presented higher rate of CO2 biofixation (42.8 %) (p < 0.01) than did Spirulina sp. LEB 18. The values for the CO2 biofixation rates and the kinetic parameters of Spirulina and Chlorella cells grown using combustion gas did not differ significantly from those of cells grown using CO2 and a carbon source in the culture media. These microalgae could be grown using ash derived from coal combustion, using the minerals present in this residue as the source of the essential metals required for their growth and the CO2 derived from the combustion gas as their carbon source. PMID:26453033

  15. Partial purification of the chloroplast ATP synthase from Chlamydomonas reinhardtii and the cloning and sequencing of a cDNA encoding the gamma subunit

    SciTech Connect

    Yu, L.M.

    1988-01-01

    The chloroplast ATP synthase was partially purified from the green alga Chlamydomonas reinhardtii by extracting membranes with deoxycholate and KCl, followed by centrifugation and ammonium sulfate fractionation of the supernatant. The enzyme assay involved the reconstitution of such fractions with bacteriorhodopsin and soybean phospholipids to form vesicles capable of light-dependent ({sup 32}P)-phosphate esterification. A cDNA for the gamma subunit from Chlamydomonas was isolated, expressed in vitro and sequenced. It contains the entire coding region for the gamma subunit precursor. A 35 amino acid long transit peptide resides at the NH{sub 2}-terminus of a 323 amino acid long mature peptide that is 77% similar to the spinach gamma subunit. Six cysteines were found; three were conserved in Chlamydomonas and spinach.

  16. Chlamydomonas Xanthophyll Cycle Mutants Identified by Video Imaging of Chlorophyll Fluorescence Quenching.

    PubMed Central

    Niyogi, K. K.; Bjorkman, O.; Grossman, A. R.

    1997-01-01

    The photosynthetic apparatus in plants is protected against oxidative damage by processes that dissipate excess absorbed light energy as heat within the light-harvesting complexes. This dissipation of excitation energy is measured as nonphotochemical quenching of chlorophyll fluorescence. Nonphotochemical quenching depends primarily on the [delta]pH that is generated by photosynthetic electron transport, and it is also correlated with the amounts of zeaxanthin and antheraxanthin that are formed from violaxanthin by the operation of the xanthophyll cycle. To perform a genetic dissection of nonphotochemical quenching, we have isolated npq mutants of Chlamydomonas by using a digital video-imaging system. In excessive light, the npq1 mutant is unable to convert violaxanthin to antheraxanthin and zeaxanthin; this reaction is catalyzed by violaxanthin de-epoxidase. The npq2 mutant appears to be defective in zeaxanthin epoxidase activity, because it accumulates zeaxanthin and completely lacks antheraxanthin and violaxanthin under all light conditions. Characterization of these mutants demonstrates that a component of nonphotochemical quenching that develops in vivo in Chlamydomonas depends on the accumulation of zeaxanthin and antheraxanthin via the xanthophyll cycle. However, observation of substantial, rapid, [delta]pH-dependent nonphotochemical quenching in the npq1 mutant demonstrates that the formation of zeaxanthin and antheraxanthin via violaxanthin de-epoxidase activity is not required for all [delta]pH-dependent nonphotochemical quenching in this alga. Furthermore, the xanthophyll cycle is not required for survival of Chlamydomonas in excessive light. PMID:12237386

  17. Mutants of Chlamydomonas: tools to study thylakoid membrane structure, function and biogenesis.

    PubMed

    de Vitry, C; Vallon, O

    1999-06-01

    The unicellular green alga Chlamydomonas reinhardtii is a model system for the study of photosynthesis and chloroplast biogenesis. C. reinhardtii has a photosynthesis apparatus similar to that of higher plants and it grows at rapid rate (generation time about 8 h). It is a facultative phototroph, which allows the isolation of mutants unable to perform photosynthesis and its sexual cycle allows a variety of genetic studies. Transformation of the nucleus and chloroplast genomes is easily performed. Gene transformation occurs mainly by homologous recombination in the chloroplast and heterologous recombination in the nucleus. Mutants are precious tools for studies of thylakoid membrane structure, photosynthetic function and assembly. Photosynthesis mutants affected in the biogenesis of a subunit of a protein complex usually lack the entire complex; this pleiotropic effect has been used in the identification of the other subunits, in the attribution of spectroscopic signals and also as a 'genetic cleaning' process which facilitates both protein complex purification, absorption spectroscopy studies or freeze-fracture analysis. The cytochrome b6f complex is not required for the growth of C. reinhardtii, unlike the case of photosynthetic prokaryotes in which the cytochrome complex is also part of the respiratory chain, and can be uniquely studied in Chlamydomonas by genetic approaches. We describe in greater detail the use of Chlamydomonas mutants in the study of this complex. PMID:10433117

  18. Recharacterization of Chlamydomonas reinhardtii and its relatives with new isolates from Japan.

    PubMed

    Nakada, Takashi; Shinkawa, Haruka; Ito, Takuro; Tomita, Masaru

    2010-01-01

    Chlamydomonas reinhardtii P. A. Dang. (Volvocales, Chlorophyceae) is one of the most intensely studied algae, and its whole genome was sequenced. Although this species was originally described based on materials from France and is often referred to as a cosmopolitan species, all culture strains available today have been isolated from eastern North America. The distinctions with similar and/or closely related species, such as Chlamydomonas globosa J. Snow and Chlamydomonas orbicularis E. G. Pringsh., are also contentious. In this study, new strains of C. reinhardtii and C. globosa were isolated from Japan and compared with several strains similar to C. reinhardtii. Based on the morphological, genealogical, phylogenetical, and mating studies including the new Japanese strains, the circumscription of C. reinhardtii was clarified. C. reinhardtii was most closely related to C. globosa, and they were shown to be different species. Although C. reinhardtii was similar to C. orbicularis, the authentic strain of C. orbicularis was morphologically distinguishable and phylogenetically distant from C. reinhardtii. Discovery of the Japanese strains of C. reinhardtii supports the cosmopolitan distribution of this species. Based on Japanese strains and/or strains from other countries, emended descriptions of C. reinhardtii, C. globosa, and C. orbicularis are given. PMID:19882207

  19. A new method to identify flanking sequence tags in chlamydomonas using 3’-RACE

    PubMed Central

    2012-01-01

    Background The green alga Chlamydomonas reinhardtii, although a premier model organism in biology, still lacks extensive insertion mutant libraries with well-identified Flanking Sequence Tags (FSTs). Rapid and efficient methods are needed for FST retrieval. Results Here, we present a novel method to identify FSTs in insertional mutants of Chlamydomonas. Transformants can be obtained with a resistance cassette lacking a 3’ untranslated region (UTR), suggesting that the RNA that is produced from the resistance marker terminates in the flanking genome when it encounters a cleavage/polyadenylation signal. We have used a robust 3’-RACE method to specifically amplify such chimeric cDNAs. Out of 38 randomly chosen transformants, 27 (71%) yielded valid FSTs, of which 23 could be unambiguously mapped to the genome. Eighteen of the mutants lie within a predicted gene. All but two of the intragenic insertions occur in the sense orientation with respect to transcription, suggesting a bias against situations of convergent transcription. Among the 14 insertion sites tested by genomic PCR, 12 could be confirmed. Among these are insertions in genes coding for PSBS3 (possibly involved in non-photochemical quenching), the NimA-related protein kinase CNK2, the mono-dehydroascorbate reductase MDAR1, the phosphoglycerate mutase PGM5 etc.. Conclusion We propose that our 3’-RACE FST method can be used to build large scale FST libraries in Chlamydomonas and other transformable organisms. PMID:22735168

  20. Bioaccumulation of nickel by algae

    SciTech Connect

    Wang, H.K.; Wood, J.M.

    1984-02-01

    Six strains of algae and one Euglena sp. were tested for their ability to bioaccumulate nickel. Radioactive /sup 63/Ni was used together with a microplate technique to determine the conditions for nickel removal by axenic cultures of cyanobacteria, green algae, and one euglenoid. The cyanobacteria tested were found to be more sensitive to nickel toxicity than the green algae or the Euglena sp. The concentration factor (CF) for nickel was determined under a variety of conditions and found to be in the range from 0 to 3.0 x 10/sup 3/. The effect of environmental variables on nickel uptake was examined, and a striking pH effect for biaccumulation was observed, with most of the algal strains accumulating nickel optimally at approximately pH 8.0. Competition experiments for binding sites between nickel and other cations as well as with other complexing anions, showed that /sup 63/Ni uptake was affected only by cobalt and by humic acids.

  1. Altered Fermentative Metabolism in Chlamydomonas reinhardtii Mutants Lacking Pyruvate Formate Lyase and Both Pyruvate Formate Lyase and Alcohol Dehydrogenase

    SciTech Connect

    Catalanotti, C.; Dubini, A.; Subramanian, V.; Yang, W. Q.; Magneschi, L.; Mus, F.; Seibert, M.; Posewitz, M. C.; Grossman, A. R.

    2012-02-01

    Chlamydomonas reinhardtii, a unicellular green alga, often experiences hypoxic/anoxic soil conditions that activate fermentation metabolism. We isolated three Chlamydomonas mutants disrupted for the pyruvate formate lyase (PFL1) gene; the encoded PFL1 protein catalyzes a major fermentative pathway in wild-type Chlamydomonas cells. When the pfl1 mutants were subjected to dark fermentative conditions, they displayed an increased flux of pyruvate to lactate, elevated pyruvate decarboxylation, ethanol accumulation, diminished pyruvate oxidation by pyruvate ferredoxin oxidoreductase, and lowered H2 production. The pfl1-1 mutant also accumulated high intracellular levels of lactate, succinate, alanine, malate, and fumarate. To further probe the system, we generated a double mutant (pfl1-1 adh1) that is unable to synthesize both formate and ethanol. This strain, like the pfl1 mutants, secreted lactate, but it also exhibited a significant increase in the levels of extracellular glycerol, acetate, and intracellular reduced sugars and a decrease in dark, fermentative H2 production. Whereas wild-type Chlamydomonas fermentation primarily produces formate and ethanol, the double mutant reroutes glycolytic carbon to lactate and glycerol. Although the metabolic adjustments observed in the mutants facilitate NADH reoxidation and sustained glycolysis under dark, anoxic conditions, the observed changes could not have been predicted given our current knowledge of the regulation of fermentation metabolism.

  2. The conserved plant sterility gene HAP2 functions after attachment of fusogenic membranes in Chlamydomonas and Plasmodium gametes

    PubMed Central

    Liu, Yanjie; Tewari, Rita; Ning, Jue; Blagborough, Andrew M.; Garbom, Sara; Pei, Jimin; Grishin, Nick V.; Steele, Robert E.; Sinden, Robert E.; Snell, William J.; Billker, Oliver

    2008-01-01

    The cellular and molecular mechanisms that underlie species-specific membrane fusion between male and female gametes remain largely unknown. Here, by use of gene discovery methods in the green alga Chlamydomonas, gene disruption in the rodent malaria parasite Plasmodium berghei, and distinctive features of fertilization in both organisms, we report discovery of a mechanism that accounts for a conserved protein required for gamete fusion. A screen for fusion mutants in Chlamydomonas identified a homolog of HAP2, an Arabidopsis sterility gene. Moreover, HAP2 disruption in Plasmodium blocked fertilization and thereby mosquito transmission of malaria. HAP2 localizes at the fusion site of Chlamydomonas minus gametes, yet Chlamydomonas minus and Plasmodium hap2 male gametes retain the ability, using other, species-limited proteins, to form tight prefusion membrane attachments with their respective gamete partners. Membrane dye experiments show that HAP2 is essential for membrane merger. Thus, in two distantly related eukaryotes, species-limited proteins govern access to a conserved protein essential for membrane fusion. PMID:18367645

  3. An ISFET-algal (Chlamydomonas) hybrid provides a system for eco-toxicological tests.

    PubMed

    Schubnell, D; Lehmann, M; Baumann, W; Rott, F G; Wolf, B; Beck, C F

    1999-05-31

    A cellular sensoring system was designed in which metabolism-dedicated pH-ISFETs and the unicellular green alga Chlamydomonas reinhardtii as a biological component, were combined. The system permits on-line detection of pH changes caused by the metabolic and photosynthetic activities of the cells. Photosynthetic activity results in a basification of the medium caused by uptake of CO2. In darkness, an acidification of the medium, resulting from the production of CO2 by degradation of starch was observed. Both, acidification and basification, are sensitive indicators for the physiological activity of the alga. Experiments using inhibitors of energy metabolism or photosynthesis illustrate the utility of this system for an on-line monitoring of substances of eco-toxicological importance. PMID:10451914

  4. Successful expression of heterologous egfp gene in the mitochondria of a photosynthetic eukaryote Chlamydomonas reinhardtii.

    PubMed

    Hu, Zhangli; Zhao, Zhonglin; Wu, Zhihua; Fan, Zhun; Chen, Jun; Wu, Jinxia; Li, Jiancheng

    2011-09-01

    The efficient expression of exogenous gene in mitochondria of photosynthetic organism has been an insurmountable problem. In this study, the pBsLPNCG was constructed by inserting the egfp gene into a site between TERMINVREP-Left repeats and the cob gene in a fragment of mitochondrial DNA of Chlamydomonas reinhardtii CC-124 and introduced into the mitochondria of respiratory deficient dum-1 mutation of C. reinhardtii CC-2654. Sequencing and DNA Southern analyses revealed that egfp gene had been integrated into the mitochondrial genome of transgenic algae as expected and no other copy of egfp existed in their nucleic genome. Both the fluorescence detection and Western blot analysis confirmed the presence of eGFP protein in the transgenic algae; it indicated that the egfp gene was successfully expressed in the mitochondria of C. reinhardtii. PMID:21664493

  5. Metabolic network reconstruction of Chlamydomonas offers insight into light-driven algal metabolism

    PubMed Central

    Chang, Roger L; Ghamsari, Lila; Manichaikul, Ani; Hom, Erik F Y; Balaji, Santhanam; Fu, Weiqi; Shen, Yun; Hao, Tong; Palsson, Bernhard Ø; Salehi-Ashtiani, Kourosh; Papin, Jason A

    2011-01-01

    Metabolic network reconstruction encompasses existing knowledge about an organism's metabolism and genome annotation, providing a platform for omics data analysis and phenotype prediction. The model alga Chlamydomonas reinhardtii is employed to study diverse biological processes from photosynthesis to phototaxis. Recent heightened interest in this species results from an international movement to develop algal biofuels. Integrating biological and optical data, we reconstructed a genome-scale metabolic network for this alga and devised a novel light-modeling approach that enables quantitative growth prediction for a given light source, resolving wavelength and photon flux. We experimentally verified transcripts accounted for in the network and physiologically validated model function through simulation and generation of new experimental growth data, providing high confidence in network contents and predictive applications. The network offers insight into algal metabolism and potential for genetic engineering and efficient light source design, a pioneering resource for studying light-driven metabolism and quantitative systems biology. PMID:21811229

  6. Harvesting fresh water and marine algae by magnetic separation: screening of separation parameters and high gradient magnetic filtration.

    PubMed

    Cerff, Martin; Morweiser, Michael; Dillschneider, Robert; Michel, Aymeé; Menzel, Katharina; Posten, Clemens

    2012-08-01

    In this study, the focus is on magnetic separation of fresh water algae Chlamydomonas reinhardtii and Chlorella vulgaris as well as marine algae Phaeodactylum tricornutum and Nannochloropsis salina by means of silica-coated magnetic particles. Due to their small size and low biomass concentrations, harvesting algae by conventional methods is often inefficient and cost-consuming. Magnetic separation is a powerful tool to capture algae by adsorption to submicron-sized magnetic particles. Hereby, separation efficiency depends on parameters such as particle concentration, pH and medium composition. Separation efficiencies of >95% were obtained for all algae while maximum particle loads of 30 and 77 g/g were measured for C. reinhardtii and P. tricornutum at pH 8 and 12, respectively. This study highlights the potential of silica-coated magnetic particles for the removal of fresh water and marine algae by high gradient magnetic filtration and provides critical discussion on future improvements. PMID:22705536

  7. Characterization of oxidative phosphorylation in the colorless chlorophyte Polytomella sp. Its mitochondrial respiratory chain lacks a plant-like alternative oxidase.

    PubMed

    Reyes-Prieto, Adrián; El-Hafidi, Mohammed; Moreno-Sánchez, Rafael; González-Halphen, Diego

    2002-07-01

    The presence of an alternative oxidase (AOX) in Polytomella sp., a colorless relative of Chlamydomonas reinhardtii, was explored. Oxygen uptake in Polytomella sp. mitochondria was inhibited by KCN (94%) or antimycin (96%), and the remaining cyanide-resistant respiration was not blocked by the AOX inhibitors salicylhydroxamic acid (SHAM) or n-propylgallate. No stimulation of an AOX activity was found upon addition of either pyruvate, alpha-ketoglutarate, or AMP, or by treatment with DTT. An antibody raised against C. reinhardtii AOX did not recognized any polypeptide band of Polytomella sp. mitochondria in Western blots. Also, PCR experiments and Southern blot analysis failed to identify an Aox gene in this colorless alga. Finally, KCN exposure of cell cultures failed to stimulate an AOX activity. Nevertheless, KCN exposure of Polytomella sp. cells induced diminished mitochondrial respiration (20%) and apparent changes in cytochrome c oxidase affinity towards cyanide. KCN-adapted cells exhibited a significant increase of a-type cytochromes, suggesting accumulation of inactive forms of cytochrome c oxidase. Another effect of KCN exposure was the reduction of the protein/fatty acid ratio of mitochondrial membranes, which may affect the observed respiratory activity. We conclude that Polytomella lacks a plant-like AOX, and that its corresponding gene was probably lost during the divergence of this colorless genus from its close photosynthetic relatives. PMID:12160990

  8. 3[prime] end maturation of the Chlamydomonas reinhardtii chloroplast atpB mRNA is a two-step process

    SciTech Connect

    Stern, D.B.; Kindle, K.L. )

    1993-04-01

    The research studied the 3[prime] end maturation of green algae chloroplast atpB mRNA. Most data on transcription termination and 3[prime] end maturation in chloroplasts have been based on in vitro experiments. Newly developed chloroplast transformation techniques have allowed the use of a green algae, Chlamydomonas reinhardtii, to examine chloroplast mRNA 3[prime] end stability determinants and mRNA processing both in vitro and in vivo. The results of this research showed that Chlamydomonas chloroplast protein extracts contain an endonuclease activity that cleaves a synthetic precursor of atpB mRNA 10 nucleotides downstream on the mature 3[prime] end in vitro. Rapid cleavage by this endonuclease is followed by exonucleolytic removal of 10 nucleotides to yield the mature 3[prime] end.

  9. Receptor mediated mineralocorticoid action in alga cell mutants.

    PubMed

    Mirshahi, M; Mirshahi, A; Nato, A; Agarwal, M K

    1992-12-21

    The multiplication of Chlamydomonas cells can be arrested by the spirolactone derivative RU 26752 and this is fully reversible by the natural hormone aldosterone. Continuous growth in the presence of RU 26752 led to the isolation of a population subsequently resistant to the action of mineralocortoid analogues, due possibly to the selection of mutant cells. Immunophotochemical evidence is provided for a 52 kDa protein that possesses functional steroid and DNA binding domains. Alga cells therefore appear to respond to steroid hormones in a manner similar to the mammalian systems, possibly via a receptor that may represent a pygmy ancestor of the latter day steroid receptor superfamily. PMID:1334844

  10. Stable isotope fractionation in photosynthesis: Analysis of autotrophic competence following transformation of the chloroplast genome of Chlamydomonas

    SciTech Connect

    Boynton, J.E.; Gillham, N.W.; Osmond, C.B.

    1991-06-15

    Isotopic techniques needed to assess the interactions between photosynthesis and respiration in Chlamydomonas have been devised for {sup 13}C, using plate and liquid cultures. The effectiveness of various transformation strategies for the chloroplast psbA gene has been evaluated with respect to their utility in constructing and characterizing strains homoplasmic for site-directed mutations in an otherwise isogenic background. Our analysis of the first site-directed change in the D-1 protein of Chlamydomonas indicates that a second site mutation (arg{sub 238} > lys) in the loop between transmembrane helices IV -- V can partially compensate for the reduced photosynthetic performance that accompanies the atrazine resistant mutation (ser{sub 264} > ala/gly) in this alga and in higher plants grown under high light intensities. 31 refs., 2 figs.

  11. Effect of Triacontanol on Chlamydomonas1

    PubMed Central

    Houtz, Robert L.; Ries, Stanley K.; Tolbert, N. E.

    1985-01-01

    Treatment of Chlamydomonas reinhardtii cells, cultured at 5% CO2, with 1 to 1000 micrograms triacontanol (TRIA) per liter resulted in 21 to 35% increases in cell density, 7 to 31% increases in total chlorophyll, and 20 to 100% increases in photosynthetic CO2 assimilation. The increase in CO2 fixation with TRIA treatment occurred before, and was independent of, increases in total chlorophyll or cell number. Chlamydomonas cells responded to a broad range of TRIA concentrations that were at least one order of magnitude above the optimum concentration established for higher plants. The necessity for larger concentrations of TRIA may be due to destabilizing effects of Ca2+ and K+ present in the Chlamydomonas growth medium. These ions caused flocculation of the colloidally dispersed TRIA in apparent competition with binding of [14C]TRIA to Chlamydomonas cells. Octacosanol inhibited the effect of TRIA on photosynthetic CO2 assimilation. TRIA treatment did not alter the distribution of 14C-label among photosynthetic products. The effect of TRIA on photosynthetic CO2 assimilation increased with time after treatment up to 3 days. Chlamydomonas cells that had been grown at low-CO2 (air) did not respond to TRIA, and transfer of high-CO2 (5%) grown cells that had responded to TRIA to a low-CO2 atmosphere resulted in a loss of the effect of TRIA. The effect of pH on photosynthetic CO2 assimilation indicated that CO2 is probably the species of inorganic carbon utilized by control and TRIA-treated Chlamydomonas cells. PMID:16664414

  12. A steering mechanism for phototaxis in Chlamydomonas.

    PubMed

    Bennett, Rachel R; Golestanian, Ramin

    2015-03-01

    Chlamydomonas shows both positive and negative phototaxis. It has a single eyespot near its equator, and as the cell rotates during the forward motion, the light signal received by the eyespot varies. We use a simple mechanical model of Chlamydomonas that couples the flagellar beat pattern to the light intensity at the eyespot to demonstrate a mechanism for phototactic steering that is consistent with observations. The direction of phototaxis is controlled by a parameter in our model, and the steering mechanism is robust to noise. Our model shows switching between directed phototaxis when the light is on and run-and-tumble behaviour in the dark. PMID:25589576

  13. A steering mechanism for phototaxis in Chlamydomonas

    PubMed Central

    Bennett, Rachel R.; Golestanian, Ramin

    2015-01-01

    Chlamydomonas shows both positive and negative phototaxis. It has a single eyespot near its equator, and as the cell rotates during the forward motion, the light signal received by the eyespot varies. We use a simple mechanical model of Chlamydomonas that couples the flagellar beat pattern to the light intensity at the eyespot to demonstrate a mechanism for phototactic steering that is consistent with observations. The direction of phototaxis is controlled by a parameter in our model, and the steering mechanism is robust to noise. Our model shows switching between directed phototaxis when the light is on and run-and-tumble behaviour in the dark. PMID:25589576

  14. Using Natural Selection to Explore the Adaptive Potential of Chlamydomonas reinhardtii

    PubMed Central

    Price, Dana C.; Levitan, Orly; Boyd, Jeffrey; Bhattacharya, Debashish

    2014-01-01

    Improving feedstock is critical to facilitate the commercial utilization of algae, in particular in open pond systems where, due to the presence of competitors and pests, high algal growth rates and stress tolerance are beneficial. Here we raised laboratory cultures of the model alga Chlamydomonas reinhardtii under serial dilution to explore the potential of crop improvement using natural selection. The alga was evolved for 1,880 generations in liquid medium under continuous light (EL population). At the end of the experiment, EL cells had a growth rate that was 35% greater than the progenitor population (PL). The removal of acetate from the medium demonstrated that EL growth enhancement largely relied on efficient usage of this organic carbon source. Genome re-sequencing uncovered 1,937 polymorphic DNA regions in the EL population with 149 single nucleotide polymorphisms resulting in amino acid substitutions. Transcriptome analysis showed, in the EL population, significant up regulation of genes involved in protein synthesis, the cell cycle and cellular respiration, whereas the DNA repair pathway and photosynthesis were down regulated. Like other algae, EL cells accumulated neutral lipids under nitrogen depletion. Our work demonstrates transcriptome and genome-wide impacts of natural selection on algal cells and points to a useful strategy for strain improvement. PMID:24658261

  15. Expression of bkt and bch genes from Haematococcus pluvialis in transgenic Chlamydomonas.

    PubMed

    Zheng, KaiJing; Wang, ChaoGang; Xiao, Ming; Chen, Jun; Li, JianCheng; Hu, ZhangLi

    2014-10-01

    β-carotene ketolase and β-carotene hydroxylase encoded by bkt and bch, respectively, are key enzymes required for astaxanthin biosynthesis in Haematococcu pluvialis 34-1n. Two expression vectors containing cDNA sequences of bkt and bch were constructed and co-transformed into cell-wall-deficient Chlamydomonas reinhardtii CC-849. Transgenic algae were screened on TAP agar plates containing 10 μg mL(-1) Zeomycin. PCR-Southern analysis showed that bkt and bch were integrated into the genomes of C. reinhardtii. Transcripts of bkt and bch were further confirmed by RT-PCR-Southern analysis. Compared with the wild type, transgenic algae produced 29.04% and 30.27% more carotenoids and xanthophylls, respectively. Moreover, the transgenic algae could accumulate 34% more astaxanthin than wild type. These results indicate that foreign bkt and bch genes were successfully translated into β-carotene ketolase and β-carotene hydroxylase, which were responsible for catalyzing the biosynthesis of astaxanthin in transgenic algae. PMID:25209726

  16. Blue-green algae

    MedlinePlus

    ... Talk with your health provider.Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)Blue-green algae might slow blood clotting. Taking blue-green algae along with medications that ...

  17. Magnetic separation of algae

    DOEpatents

    Nath, Pulak; Twary, Scott N.

    2016-04-26

    Described herein are methods and systems for harvesting, collecting, separating and/or dewatering algae using iron based salts combined with a magnetic field gradient to separate algae from an aqueous solution.

  18. Water Collective Dynamics in Whole Photosynthetic Green Algae as Affected by Protein Single Mutation.

    PubMed

    Russo, Daniela; Rea, Giuseppina; Lambreva, Maya D; Haertlein, Michael; Moulin, Martine; De Francesco, Alessio; Campi, Gaetano

    2016-07-01

    In the context of the importance of water molecules for protein function/dynamics relationship, the role of water collective dynamics in Chlamydomonas green algae carrying both native and mutated photosynthetic proteins has been investigated by neutron Brillouin scattering spectroscopy. Results show that single point genetic mutation may notably affect collective density fluctuations in hydrating water providing important insight on the transmission of information possibly correlated to biological functionality. In particular, we highlight that the damping factor of the excitations is larger in the native compared to the mutant algae as a signature of a different plasticity and structure of the hydrogen bond network. PMID:27300078

  19. Influence of algae on photolysis rates of chemicals in water

    SciTech Connect

    Zepp, R.G.; Schlotzhauer, P.F.

    1983-08-01

    Sunlight-induced algal transformations of 22 nonionic organic chemicals were studied in order to provide kinetic results and equations concerning the influence of algae on the behavior of pollutants in freshwater environments. Screening studies indicated that green and blue-green algae, at concentrations of 1-10 mg of chlorophyll a/L, accelerate photoreaction of certain polycylic aromatic hydrocarbons, organophosphorus compounds, and anilines in water. The rate of change in aniline concentration, (P), in the aniline-Chlamydomonas photoreaction can be described by the following expression: rate = A(1 + B/(P))-1. At low substrate concentrations, the reaction rate is first order with respect to both algae and substrate concentration. Methyl parathion and parathion photoreacted 390 times more rapidly when sorbed by algae than in distilled water, and aniline and m-toluidine reacted over 12000 times faster, indicating that light-induced algal transformations of certain pollutants may be significant. Other results indicated that reaction rates are unaffected by heat-killing the algae. 27 references

  20. (Carbon and hydrogen metabolism of green algae in light and dark)

    SciTech Connect

    Not Available

    1990-01-01

    The focus of this project was the elucidation of anaerobic metabolism in ecuaryotic green algae, chlamydomonas reinhardii. Chlamydomonas is a versatile organism that can grow under disparate conditions such as fresh water lakes and sewage ponds. The cell an photoassimilate CO{sub 2} aerobically and anaerobically, the latter after adaptation'' to a hydrogen metabolism. It can recall the knallgas or oxyhydrogen reaction and utilize hydrogen the simplest of all reducing agents for the dark assimilation of CO{sub 2} by the photosynthetic carbon reduction cycle. The dark reduction with hydrogen lies on the border line between autotrophic and heterotrophic carbon assimilation. Both autotrophic and heterotrophic bacteria are known in which molecular hydrogen can replace either inorganic or organic hydrogen donors. Here the dark reduction of CO{sub 2} acquires a particular importance since it occurs in the same cell that carries on photoreduction and photosynthesis. We will demonstrate here that the alga chloroplast possesses a respiratory capacity. It seems likely that Chlamydomonas may have retained the chloroplastic respiratory pathway because of the selective advantage provided to the algae under a wide range of environmental conditions that the cells experience in nature. The ability to cycle electrons and poise the reduction level of the photosynthetic apparatus under aerobic and microaerobic conditions could allow more efficient CO{sub 2} fixation and enhanced growth under unfavorable conditions or survival under more severe conditions.

  1. Evidence for a photoprotective function for secondary carotenoids of snow algae

    SciTech Connect

    Bidigare, R.R.; Ondrusek, M.E. ); Kennicutt, M.C. II ); Iturriaga, R. ); Harvey, H.R. ); Hoham, R.W. ); Macko, S.A. )

    1993-08-01

    Snow algae occupy a unique habitat in high altitude and polar environments. These algae are often subject to extremes in nutrient availability, acidity, solar irradiance, desiccation, and ambient temperature. This report documents the accumulation of secondary carotenoids by snow algae in response to the availability of nitrogenous nutrients. Unusually large accumulations of astaxanthin esters in extra-chloroplastic lipid globules produce the characteristic red pigmentation typical of some snow algae (e.g., Chlamydomonas nivalis (Bauer) Wille). Consequently, these compounds greatly reduce the amount of light available for absorption by the light-harvesting pigment-protein complexes, thus potentially limiting photoinhibition and photodamage caused by intense solar radiation. The esterification of astaxanthin with fatty acids represents a possible mechanism by which this chromophore can be concentrated within cytoplasmic globules to maximize its photoprotective efficiency. 53 refs., 2 figs., 4 tabs.

  2. Identification of the Elusive Pyruvate Reductase of Chlamydomonas reinhardtii Chloroplasts.

    PubMed

    Burgess, Steven J; Taha, Hussein; Yeoman, Justin A; Iamshanova, Oksana; Chan, Kher Xing; Boehm, Marko; Behrends, Volker; Bundy, Jacob G; Bialek, Wojciech; Murray, James W; Nixon, Peter J

    2016-01-01

    Under anoxic conditions the green alga Chlamydomonas reinhardtii activates various fermentation pathways leading to the creation of formate, acetate, ethanol and small amounts of other metabolites including d-lactate and hydrogen. Progress has been made in identifying the enzymes involved in these pathways and their subcellular locations; however, the identity of the enzyme involved in reducing pyruvate to d-lactate has remained unclear. Based on sequence comparisons, enzyme activity measurements, X-ray crystallography, biochemical fractionation and analysis of knock-down mutants, we conclude that pyruvate reduction in the chloroplast is catalyzed by a tetrameric NAD(+)-dependent d-lactate dehydrogenase encoded by Cre07.g324550. Its expression during aerobic growth supports a possible function as a 'lactate valve' for the export of lactate to the mitochondrion for oxidation by cytochrome-dependent d-lactate dehydrogenases and by glycolate dehydrogenase. We also present a revised spatial model of fermentation based on our immunochemical detection of the likely pyruvate decarboxylase, PDC3, in the cytoplasm. PMID:26574578

  3. Metabolic acclimation to excess light intensity in Chlamydomonas reinhardtii.

    PubMed

    Davis, Maria C; Fiehn, Oliver; Durnford, Dion G

    2013-07-01

    There are several well-described acclimation responses to excess light in green algae but the effect on metabolism has not been thoroughly investigated. This study examines the metabolic changes during photoacclimation to high-light (HL) stress in Chlamydomonas reinhardtii using nuclear magnetic resonance and mass spectrometry. Using principal component analysis, a clear metabolic response to HL intensity was observed on global metabolite pools, with major changes in the levels of amino acids and related nitrogen metabolites. Amino acid pools increased during short-term photoacclimation, but were especially prominent in HL-acclimated cultures. Unexpectedly, we observed an increase in mitochondrial metabolism through downstream photorespiratory pathways. The expression of two genes encoding key enzymes in the photorespiratory pathway, glycolate dehydrogenase and malate synthase, were highly responsive to the HL stress. We propose that this pathway contributes to metabolite pools involved in nitrogen assimilation and may play a direct role in photoacclimation. Our results suggest that primary and secondary metabolism is highly pliable and plays a critical role in coping with the energetic imbalance during HL exposure and a necessary adjustment to support an increased growth rate that is an effective energy sink for the excess reducing power generated during HL stress. PMID:23346954

  4. Singlet oxygen production in Chlamydomonas reinhardtii under heat stress.

    PubMed

    Prasad, Ankush; Ferretti, Ursula; Sedlářová, Michaela; Pospíšil, Pavel

    2016-01-01

    In the current study, singlet oxygen formation by lipid peroxidation induced by heat stress (40 °C) was studied in vivo in unicellular green alga Chlamydomonas reinhardtii. Primary and secondary oxidation products of lipid peroxidation, hydroperoxide and malondialdehyde, were generated under heat stress as detected using swallow-tailed perylene derivative fluorescence monitored by confocal laser scanning microscopy and high performance liquid chromatography, respectively. Lipid peroxidation was initiated by enzymatic reaction as inhibition of lipoxygenase by catechol and caffeic acid prevented hydroperoxide formation. Ultra-weak photon emission showed formation of electronically excited species such as triplet excited carbonyl, which, upon transfer of excitation energy, leads to the formation of either singlet excited chlorophyll or singlet oxygen. Alternatively, singlet oxygen is formed by direct decomposition of hydroperoxide via Russell mechanisms. Formation of singlet oxygen was evidenced by the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl detected by electron paramagnetic resonance spin-trapping spectroscopy and the imaging of green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. Suppression of singlet oxygen formation by lipoxygenase inhibitors indicates that singlet oxygen may be formed via enzymatic lipid peroxidation initiated by lipoxygenase. PMID:26831215

  5. Singlet oxygen production in Chlamydomonas reinhardtii under heat stress

    PubMed Central

    Prasad, Ankush; Ferretti, Ursula; Sedlářová, Michaela; Pospíšil, Pavel

    2016-01-01

    In the current study, singlet oxygen formation by lipid peroxidation induced by heat stress (40 °C) was studied in vivo in unicellular green alga Chlamydomonas reinhardtii. Primary and secondary oxidation products of lipid peroxidation, hydroperoxide and malondialdehyde, were generated under heat stress as detected using swallow-tailed perylene derivative fluorescence monitored by confocal laser scanning microscopy and high performance liquid chromatography, respectively. Lipid peroxidation was initiated by enzymatic reaction as inhibition of lipoxygenase by catechol and caffeic acid prevented hydroperoxide formation. Ultra-weak photon emission showed formation of electronically excited species such as triplet excited carbonyl, which, upon transfer of excitation energy, leads to the formation of either singlet excited chlorophyll or singlet oxygen. Alternatively, singlet oxygen is formed by direct decomposition of hydroperoxide via Russell mechanisms. Formation of singlet oxygen was evidenced by the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl detected by electron paramagnetic resonance spin-trapping spectroscopy and the imaging of green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. Suppression of singlet oxygen formation by lipoxygenase inhibitors indicates that singlet oxygen may be formed via enzymatic lipid peroxidation initiated by lipoxygenase. PMID:26831215

  6. Transport of urea at low concentrations in Chlamydomonas reinhardi.

    PubMed

    Williams, S K; Hodson, R C

    1977-04-01

    Urea transport into the unicellular green alga Chlamydomonas reinhardi was investigated to further our understanding of controls operating on urea catabolism in this organism. Transport into cells grown with acetate and deprived of ammonia is a saturable process, mediated by at least two systems operating maximally at different external urea concentrations. The lower concentration system, with an apparent Km for urea of 5.1 micron, was the object of detailed study. Transport of urea from a saturating concentration (57 micron) into ammonia- and acetate-grown cells freshly suspended in ammonia-limited medium was not detected. Upon further culturing in the absence of ammonia, derepression occurred with transport ability, first appearing at about 1 h , reaching a maximum at about 2 h, and maintaining this maximum at least 5 h. In contrast to this, CO2-grown cells became derepressed more slowly, and maximum transport ability was not maintained. Addition of ammonia or methylamine (5 mM) during nitrogen deprivation prevented further increases in transport ability and caused loss of previously acquired transport ability. Cycloheximide (10 microng/ml) had a similar effect. Energy uncouplers or dark, anaerobic conditions depressed transport. By these criteria, transport from low urea concentrations is mediated by a process that requires protein synthesis and activation by cellular energy, and the process has a rapid rate of turnover and of deactivation by ammonia. PMID:856784

  7. Identification of the Elusive Pyruvate Reductase of Chlamydomonas reinhardtii Chloroplasts

    PubMed Central

    Burgess, Steven J.; Taha, Hussein; Yeoman, Justin A.; Iamshanova, Oksana; Chan, Kher Xing; Boehm, Marko; Behrends, Volker; Bundy, Jacob G.; Bialek, Wojciech; Murray, James W.; Nixon, Peter J.

    2016-01-01

    Under anoxic conditions the green alga Chlamydomonas reinhardtii activates various fermentation pathways leading to the creation of formate, acetate, ethanol and small amounts of other metabolites including d-lactate and hydrogen. Progress has been made in identifying the enzymes involved in these pathways and their subcellular locations; however, the identity of the enzyme involved in reducing pyruvate to d-lactate has remained unclear. Based on sequence comparisons, enzyme activity measurements, X-ray crystallography, biochemical fractionation and analysis of knock-down mutants, we conclude that pyruvate reduction in the chloroplast is catalyzed by a tetrameric NAD+-dependent d-lactate dehydrogenase encoded by Cre07.g324550. Its expression during aerobic growth supports a possible function as a ‘lactate valve’ for the export of lactate to the mitochondrion for oxidation by cytochrome-dependent d-lactate dehydrogenases and by glycolate dehydrogenase. We also present a revised spatial model of fermentation based on our immunochemical detection of the likely pyruvate decarboxylase, PDC3, in the cytoplasm. PMID:26574578

  8. CrGNAT gene regulates excess copper accumulation and tolerance in Chlamydomonas reinhardtii.

    PubMed

    Wang, Ye; Cheng, Zhen Zhen; Chen, Xi; Zheng, Qi; Yang, Zhi Min

    2015-11-01

    Excess copper (Cu) in environment affects the growth and metabolism of plants and green algae. However, the molecular mechanism for regulating plant tolerance to excess Cu is not fully understood. Here, we report a gene CrGNAT enconding an acetyltransferase in Chlamydomonas reinhardtii and identified its role in regulating tolerance to Cu toxicity. Expression of CrGNAT was significantly induced by 75-400μM Cu. The top induction occurred at 100μM. Transgenic algae overexpressing CrGNAT (35S::CrGNAT) in C. reinhardtii showed high tolerance to excess Cu, with improved cell population, chlorophyll accumulation and photosynthesis efficiency, but with low degree of oxidation with regard to reduced hydrogen peroxide, lipid peroxides and non-protein thiol compounds. In contrast, CrGNAT knock-down lines with antisense led to sensitivity to Cu stress. 35S::CrGNAT algae accumulated more Cu and other metals (Zn, Fe, Cu, Mn and Mg) than wild-type, whereas the CrGNAT down-regulated algae (35S::AntiCrGNAT) had moderate levels of Cu and Mn, but no effects on Zn, Fe and Mg accumulation as compared to wild-type. The elevated metal absorption in CrGNAT overexpression algae implies that the metals can be removed from water media. Quantitative RT-PCR analysis revealed that expression of two genes encoding N-lysine histone methyltransferases was repressed in 35S::CrGNAT algae, suggesting that CrGNAT-regulated algal tolerance to Cu toxicity is likely associated with histone methylation and chromatin remodeling. The present work provided an example a basis to develop techniques for environmental restoration of metal-contaminated aquatic ecosystems. PMID:26475193

  9. Green Algae as Model Organisms for Biological Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Goldstein, Raymond E.

    2015-01-01

    In the past decade, the volvocine green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model organisms for a number of problems in biological fluid dynamics. These include flagellar propulsion, nutrient uptake by swimming organisms, hydrodynamic interactions mediated by walls, collective dynamics and transport within suspensions of microswimmers, the mechanism of phototaxis, and the stochastic dynamics of flagellar synchronization. Green algae are well suited to the study of such problems because of their range of sizes (from 10 μm to several millimeters), their geometric regularity, the ease with which they can be cultured, and the availability of many mutants that allow for connections between molecular details and organism-level behavior. This review summarizes these recent developments and highlights promising future directions in the study of biological fluid dynamics, especially in the context of evolutionary biology, that can take advantage of these remarkable organisms.

  10. Green Algae as Model Organisms for Biological Fluid Dynamics*

    PubMed Central

    Goldstein, Raymond E.

    2015-01-01

    In the past decade the volvocine green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model organisms for a number of problems in biological fluid dynamics. These include flagellar propulsion, nutrient uptake by swimming organisms, hydrodynamic interactions mediated by walls, collective dynamics and transport within suspensions of microswimmers, the mechanism of phototaxis, and the stochastic dynamics of flagellar synchronization. Green algae are well suited to the study of such problems because of their range of sizes (from 10 μm to several millimetres), their geometric regularity, the ease with which they can be cultured and the availability of many mutants that allow for connections between molecular details and organism-level behavior. This review summarizes these recent developments and highlights promising future directions in the study of biological fluid dynamics, especially in the context of evolutionary biology, that can take advantage of these remarkable organisms. PMID:26594068

  11. Proton Gradient Regulation 5-Mediated Cyclic Electron Flow under ATP- or Redox-Limited Conditions: A Study of ΔATPase pgr5 and ΔrbcL pgr5 Mutants in the Green Alga Chlamydomonas reinhardtii1[C][W

    PubMed Central

    Johnson, Xenie; Steinbeck, Janina; Dent, Rachel M.; Takahashi, Hiroko; Richaud, Pierre; Ozawa, Shin-Ichiro; Houille-Vernes, Laura; Petroutsos, Dimitris; Rappaport, Fabrice; Grossman, Arthur R.; Niyogi, Krishna K.; Hippler, Michael; Alric, Jean

    2014-01-01

    The Chlamydomonas reinhardtii proton gradient regulation5 (Crpgr5) mutant shows phenotypic and functional traits similar to mutants in the Arabidopsis (Arabidopsis thaliana) ortholog, Atpgr5, providing strong evidence for conservation of PGR5-mediated cyclic electron flow (CEF). Comparing the Crpgr5 mutant with the wild type, we discriminate two pathways for CEF and determine their maximum electron flow rates. The PGR5/proton gradient regulation-like1 (PGRL1) ferredoxin (Fd) pathway, involved in recycling excess reductant to increase ATP synthesis, may be controlled by extreme photosystem I acceptor side limitation or ATP depletion. Here, we show that PGR5/PGRL1-Fd CEF functions in accordance with an ATP/redox control model. In the absence of Rubisco and PGR5, a sustained electron flow is maintained with molecular oxygen instead of carbon dioxide serving as the terminal electron acceptor. When photosynthetic control is decreased, compensatory alternative pathways can take the full load of linear electron flow. In the case of the ATP synthase pgr5 double mutant, a decrease in photosensitivity is observed compared with the single ATPase-less mutant that we assign to a decreased proton motive force. Altogether, our results suggest that PGR5/PGRL1-Fd CEF is most required under conditions when Fd becomes overreduced and photosystem I is subjected to photoinhibition. CEF is not a valve; it only recycles electrons, but in doing so, it generates a proton motive force that controls the rate of photosynthesis. The conditions where the PGR5 pathway is most required may vary in photosynthetic organisms like C. reinhardtii from anoxia to high light to limitations imposed at the level of carbon dioxide fixation. PMID:24623849

  12. O(2) uptake in the light in chlamydomonas: evidence for persistent mitochondrial respiration.

    PubMed

    Peltier, G; Thibault, P

    1985-09-01

    The nature of the process responsible for the stationary O(2) uptake occurring in the light under saturating CO(2) concentration in Chlamydomonas reinhardii has been investigated. For this purpose, a mass spectrometer with a membrane inlet system was used to measure O(2) uptake and evolution in the algal suspension. First, we observed that the O(2) uptake rate was constant (about 0.5 micromoles of O(2) per milligram chlorophyll per minute) during a light to dark transition and was not affected by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Salicylhydroxamic acid had no effect on O(2) uptake in the dark or in the light, but was found to have the same inhibitory effect either in the dark or in the light when added to cyanide-treated algae. The stimulation of the O(2) uptake rate due to the uncoupling effect of carbonyl cyanide m-chlorophenylhydrazone was about the same in the dark or in the light. From these results, we conclude that mitochondrial respiration is maintained during illumination and therefore is not inhibited by high ATP levels. Another conclusion is that in conditions where photorespiration is absent, no other light-dependent O(2) uptake process occurs. If Mehler reactions are involved, in Chlamydomonas, under conditions where both photosynthetic carbon oxidation and reduction cycles cannot operate (as in cyanide-treated algae), their occurrence in photosynthesizing algae either under saturating CO(2) concentration or at the CO(2) compensation point appears very unlikely. The comparison with the situation previously reported in Scenedesmus (R. J. Radmer and B. Kok 1976 Plant Physiol 58: 336-340) suggests that different O(2) uptake processes might be present in these two algal species. PMID:16664375

  13. A comparison of hydrogen photoproduction by sulfur-deprived Chlamydomonas reinhardtii under different growth conditions.

    PubMed

    Kosourov, Sergey; Patrusheva, Elena; Ghirardi, Maria L; Seibert, Michael; Tsygankov, Anatoly

    2007-03-10

    Continuous photoproduction of H(2) by the green alga, Chlamydomonas reinhardtii, is observed after incubating the cultures for about a day in the absence of sulfate and in the presence of acetate. Sulfur deprivation causes the partial and reversible inactivation of photosynthetic O(2) evolution in algae, resulting in the light-induced establishment of anaerobic conditions in sealed photobioreactors, expression of two [FeFe]-hydrogenases in the cells, and H(2) photoproduction for several days. We have previously demonstrated that sulfur-deprived algal cultures can produce H(2) gas in the absence of acetate, when appropriate experimental protocols were used (Tsygankov, A.A., Kosourov, S.N., Tolstygina, I.V., Ghirardi, M.L., Seibert, M., 2006. Hydrogen production by sulfur-deprived Chlamydomonas reinhardtii under photoautotrophic conditions. Int. J. Hydrogen Energy 31, 1574-1584). We now report the use of an automated photobioreactor system to compare the effects of photoautotrophic, photoheterotrophic and photomixotrophic growth conditions on the kinetic parameters associated with the adaptation of the algal cells to sulfur deprivation and H(2) photoproduction. This was done under the experimental conditions outlined in the above reference, including controlled pH. From this comparison we show that both acetate and CO(2) are required for the most rapid inactivation of photosystem II and the highest yield of H(2) gas production. Although, the presence of acetate in the system is not critical for the process, H(2) photoproduction under photoautotrophic conditions can be increased by optimizing the conditions for high starch accumulation. These results suggest ways of engineering algae to improve H(2) production, which in turn may have a positive impact on the economics of applied systems for H(2) production. PMID:17275940

  14. Effects of nitrogen dioxide on algae

    SciTech Connect

    Wodzinski, R.S.; Alexander, M.

    1980-01-01

    Photosynthetic activity of Anabaena flos-aquae in a soil suspension at an initial pH of 4.9 was almost totally eliminated after 3 days of exposure to 5.0 ppm (..mu..l/liter) NO/sub 2/, at which time the pH had fallen to 3.9. In contrast, A. flos-aquae in soil suspensions at an initial pH of 6.0 was not inhibited after 3 days by 5.0 ppm NO/sub 2/, but the activity was reduced by half in the presence of 15.0 ppm NO/sub 2/; the pH was 6.5 and 5.8, respectively, in the NO/sub 2/-treated samples on day 3. Photosynthesis by the green algae Chlamydomonas reinhardtii and Ankistrodesmus falcatus in soil suspensions at an initial pH of approx 4.2 was not appreciably affected by 15.0 ppm of NO/sub 2/ after 3 days, at which time the pH had fallen below 4.0. The high levels of NO/sub 2/ and low pH values required for toxicity suggest that blue-green and green algae probably will not be affected directly by NO/sub 2/ in polluted air.

  15. Effects of nitrogen dioxide on algae

    SciTech Connect

    Wodzinski, R.S.; Alexander, M.

    1980-01-01

    Photosynthetic activity of Anabaena flos-aquae in a soil suspension at an initial pH of 4.9 was almost totally eliminated after 3 days of exposure to 5.0 ppM (..mu..l/liter) NO/sub 2/, at which time the pH had fallen to 3.9. In contrast, A. flos-aquae in soil suspensions at an initial pH of 6.0 was not inhibited after 3 days by 5.0 ppM NO/sub 2/, but the activity was reduced by half in the presence of 15.0 ppM NO/sub 2/; the pH was 6.5 and 5.8, respectively, in the NO/sub 2/-treated samples on day 3. Photosynthesis by the green algae Chlamydomonas reinhardtii and Ankistrodesmus falcatus in soil suspensions at an initial pH of approx. 4.2 was not appreciably affected by 15.0 ppM of NO/sub 2/ after 3 days, at which time the pH had fallen below 4.0. The high levels of NO/sub 2/ and low pH values required for toxicity suggest that blue-green and green algae probably will not be affected directly by NO/sub 2/ in polluted air.

  16. Measurement of ethanol formation in single living cells of Chlamydomonas reinhardtii using synchrotron Fourier Transform Infrared spectromicroscopy

    NASA Astrophysics Data System (ADS)

    Goff, Kira L.; Quaroni, Luca; Pedersen, Tor; Wilson, Kenneth E.

    2010-02-01

    We demonstrate the capability of Fourier-Transform Infra-Red (FITR) spectroscopy to detect metabolite formation by the unicellular algae Chlamydomonas reinhardtii in solution. We show that using a synchrotron source in the microscopy configuration provides a sufficient s/n ratio to detect small molecular species accumulating at a single cell, allowing an increased sensitivity relative to measurements of bulk cultures. The formation of small molecular species, including ethanol and at least one carbonyl containing compound, can be detected with a time resolution of the order of one minute.

  17. Measurement of ethanol formation in single living cells of Chlamydomonas reinhardtii using synchrotron Fourier Transform Infrared spectromicroscopy

    SciTech Connect

    Goff, Kira L.; Quaroni, Luca; Pedersen, Tor; Wilson, Kenneth E.

    2010-02-03

    We demonstrate the capability of Fourier-Transform Infra-Red (FITR) spectroscopy to detect metabolite formation by the unicellular algae Chlamydomonas reinhardtii in solution. We show that using a synchrotron source in the microscopy configuration provides a sufficient s/n ratio to detect small molecular species accumulating at a single cell, allowing an increased sensitivity relative to measurements of bulk cultures. The formation of small molecular species, including ethanol and at least one carbonyl containing compound, can be detected with a time resolution of the order of one minute.

  18. Toxicity of chlorinated benzenes to marine algae

    NASA Astrophysics Data System (ADS)

    Ma, Yan-Jun; Wang, Xiu-Lin; Yu, Wei-Jun; Zhang, Li-Jun; Sun, Han-Zhang

    1997-12-01

    Growth of Chlorella marine, Nannochloropsis oculata, Pyramidomonas sp., Platymonas subcordiformis and Phaeodactylum tricornutum exposed to monochlorobenzene (MCB), 1,2-dichlorobenzene (1,2-DCB), 1, 2, 3, 4-tetrachlorobenzene (1, 2, 3, 4-TeCB) and pentachlorobenzene (PeCB) was tested. Tests of 72 h- EC 50 values showed that the toxicity ranged in the order: MCB<1,2-DCB<1,2,3,4-TeCBalgae was almost in the order: Pyramidomonas sp. < Platymonas subcordiformis < Nannochloropsis oculata < Chlorella marine < Phaeodactylum tricomutum. Study of the QSAR (Quantitative Structure-Activity Relationship) between K OW and toxicity of CBs to marine algae showed good relationships between -log EC 50 and log K OW.

  19. Taxonomic revision of oil-producing green algae, Chlorococcum oleofaciens (Volvocales, Chlorophyceae), and its relatives.

    PubMed

    Kawasaki, Yuriko; Nakada, Takashi; Tomita, Masaru

    2015-10-01

    Historically, species in Volvocales were classified based primarily on morphology. Although the taxonomy of Chlamydomonas has been re-examined using a polyphasic approach including molecular phylogeny, that of Chlorococcum (Cc.), the largest coccoid genus in Volvocales, has yet to be reexamined. Six species thought to be synonymous with the oil-producing alga Cc. oleofaciens were previously not confirmed by molecular phylogeny. In this study, seven authentic strains of Cc. oleofaciens and its putative synonyms, along with 11 relatives, were examined based on the phylogeny of the 18S ribosomal RNA (rRNA) gene, comparisons of secondary structures of internal transcribed spacer 1 (ITS1) and ITS2 rDNA, and morphological observations by light microscopy. Seven 18S rRNA types were recognized among these strains and three were distantly related to Cc. oleofaciens. Comparisons of ITS rDNA structures suggested possible separation of the remaining four types into different species. Shapes of vegetative cells, thickness of the cell walls in old cultures, the size of cells in old cultures, and stigma morphology of zoospores also supported the 18S rRNA grouping. Based on these results, the 18 strains examined were reclassified into seven species. Among the putative synonyms, synonymy of Cc. oleofaciens, Cc. croceum, and Cc. granulosum was confirmed, and Cc. microstigmatum, Cc. rugosum, Cc. aquaticum, and Cc. nivale were distinguished from Cc. oleofaciens. Furthermore, another related strain is described as a new species, Macrochloris rubrioleum sp. nov. PMID:26986894

  20. Basis for the Resistance of Several Algae to Microbial Decomposition

    PubMed Central

    Gunnison, Douglas; Alexander, Martin

    1975-01-01

    The basis for the resistance of certain algae to microbial decomposition in natural waters was investigated using Pediastrum duplex, Staurastrum sp., and Fischerella muscicola as test organisms. Enzyme preparations previously found to convert susceptible algae into spheroplasts had no such effect on the resistant species, although glucose and galacturonic acid were released from P. duplex walls. Little protein or lipid but considerable carbohydrate was found in the walls of the refractory organisms, but resistance was not correlated with the presence of a unique sugar monomer. A substance present in Staurastrum sp. walls was characterized as lignin or lignin-like on the basis of its extraction characteristics, infrared spectrum, pyrolysis pattern, and content of an aromatic building block. Sporopollenin was found in P. duplex, and cellulose in Staurastrum sp. Cell walls of the algae were fractionated, and the fractions least susceptible to microbial degradation were the sporopollenin of P. duplex, the polyaromatic component of Staurastrum sp., and two F. muscicola fractions containing several sugar monomers. The sporopollenin content of P. duplex, the content of lignin or a related constituent of Staurastrum sp., and the resistance of the algae to microbial attack increased with age. It is suggested that resistance results from the presence of sporopollenin in P. duplex, a lignin-like material in Staurastrum sp., and possibly heteropolysaccharides in F. muscicola. PMID:808166

  1. Expression and assembly of a fully active antibody in algae

    NASA Astrophysics Data System (ADS)

    Mayfield, Stephen P.; Franklin, Scott E.; Lerner, Richard A.

    2003-01-01

    Although combinatorial antibody libraries have solved the problem of access to large immunological repertoires, efficient production of these complex molecules remains a problem. Here we demonstrate the efficient expression of a unique large single-chain (lsc) antibody in the chloroplast of the unicellular, green alga, Chlamydomonas reinhardtii. We achieved high levels of protein accumulation by synthesizing the lsc gene in chloroplast codon bias and by driving expression of the chimeric gene using either of two C. reinhardtii chloroplast promoters and 5' and 3' RNA elements. This lsc antibody, directed against glycoprotein D of the herpes simplex virus, is produced in a soluble form by the alga and assembles into higher order complexes in vivo. Aside from dimerization by disulfide bond formation, the antibody undergoes no detectable posttranslational modification. We further demonstrate that accumulation of the antibody can be modulated by the specific growth regime used to culture the alga, and by the choice of 5' and 3' elements used to drive expression of the antibody gene. These results demonstrate the utility of alga as an expression platform for recombinant proteins, and describe a new type of single chain antibody containing the entire heavy chain protein, including the Fc domain.

  2. Culture of microalgae Chlamydomonas reinhardtii in wastewater for biomass feedstock production.

    PubMed

    Kong, Qing-xue; Li, Ling; Martinez, Blanca; Chen, Paul; Ruan, Roger

    2010-01-01

    The objective of this research was to develop large-scale technologies to produce oil-rich algal biomass from wastewater. The experiments were conducted using Erlenmeyer flasks and biocoil photobioreactor. Chlamydomonas reinhardtii was grown in artificial media and wastewaters taken from three different stages of the treatment process, namely, influent, effluent, and centrate. Each of wastewaters contained different levels of nutrients. The specific growth rate of C. reinhardtii in different cultures was monitored over a period of 10 days. The biomass yield of microalgae and associated nitrogen and phosphorous removal were evaluated. Effects of CO(2) and pH on the growth were also studied. The level of nutrients greatly influenced algae growth. High levels of nutrients seem to inhibit algae growth in the beginning, but provided sustained growth to a high degree. The studies have shown that the optimal pH for C. reinhardtii is in the range of 7.5. An injection of air and a moderate amount of CO(2) promoted algae growth. However, too much CO(2) inhibited algae growth due to a significant decrease in pH. The experimental results showed that algal dry biomass yield reached a maximum of 2.0 g L(-1) day(-1) in the biocoil. The oil content of microalgae of C. reinhardtii was 25.25% (w/w) in dry biomass weight. In the biocoil, 55.8 mg nitrogen and 17.4 mg phosphorus per liter per day were effectively removed from the centrate wastewater. Ferric chloride was found to be an effective flocculent that helps the algae settle for easy harvest and separation from the culture media. PMID:19507059

  3. Characterization of a Mutant Deficient for Ammonium and Nitric Oxide Signalling in the Model System Chlamydomonas reinhardtii

    PubMed Central

    Sanz-Luque, Emanuel; Ocaña-Calahorro, Francisco; Galván, Aurora; Fernández, Emilio; de Montaigu, Amaury

    2016-01-01

    The ubiquitous signalling molecule Nitric Oxide (NO) is characterized not only by the variety of organisms in which it has been described, but also by the wealth of biological processes that it regulates. In contrast to the expanding repertoire of functions assigned to NO, however, the mechanisms of NO action usually remain unresolved, and genes that work within NO signalling cascades are seldom identified. A recent addition to the list of known NO functions is the regulation of the nitrogen assimilation pathway in the unicellular alga Chlamydomonas reinhardtii, a well-established model organism for genetic and molecular studies that offers new possibilities in the search for mediators of NO signalling. By further exploiting a collection of Chlamydomonas insertional mutant strains originally isolated for their insensitivity to the ammonium (NH4+) nitrogen source, we found a mutant which, in addition to its ammonium insensitive (AI) phenotype, was not capable of correctly sensing the NO signal. Similarly to what had previously been described in the AI strain cyg56, the expression of nitrogen assimilation genes in the mutant did not properly respond to treatments with various NO donors. Complementation experiments showed that NON1 (NO Nitrate 1), a gene that encodes a protein containing no known functional domain, was the gene underlying the mutant phenotype. Beyond the identification of NON1, our findings broadly demonstrate the potential for Chlamydomonas reinhardtii to be used as a model system in the search for novel components of gene networks that mediate physiological responses to NO. PMID:27149516

  4. High-Resolution Profiling of a Synchronized Diurnal Transcriptome from Chlamydomonas reinhardtii Reveals Continuous Cell and Metabolic Differentiation[OPEN

    PubMed Central

    2015-01-01

    The green alga Chlamydomonas reinhardtii is a useful model organism for investigating diverse biological processes, such as photosynthesis and chloroplast biogenesis, flagella and basal body structure/function, cell growth and division, and many others. We combined a highly synchronous photobioreactor culture system with frequent temporal sampling to characterize genome-wide diurnal gene expression in Chlamydomonas. Over 80% of the measured transcriptome was expressed with strong periodicity, forming 18 major clusters. Genes associated with complex structures and processes, including cell cycle control, flagella and basal bodies, ribosome biogenesis, and energy metabolism, all had distinct signatures of coexpression with strong predictive value for assigning and temporally ordering function. Importantly, the frequent sampling regime allowed us to discern meaningful fine-scale phase differences between and within subgroups of genes and enabled the identification of a transiently expressed cluster of light stress genes. Coexpression was further used both as a data-mining tool to classify and/or validate genes from other data sets related to the cell cycle and to flagella and basal bodies and to assign isoforms of duplicated enzymes to their cognate pathways of central carbon metabolism. Our diurnal coexpression data capture functional relationships established by dozens of prior studies and are a valuable new resource for investigating a variety of biological processes in Chlamydomonas and other eukaryotes. PMID:26432862

  5. Chlamydomonas as a model for biofuels and bio-products production.

    PubMed

    Scranton, Melissa A; Ostrand, Joseph T; Fields, Francis J; Mayfield, Stephen P

    2015-05-01

    Developing renewable energy sources is critical to maintaining the economic growth of the planet while protecting the environment. First generation biofuels focused on food crops like corn and sugarcane for ethanol production, and soybean and palm for biodiesel production. Second generation biofuels based on cellulosic ethanol produced from terrestrial plants, has received extensive funding and recently pilot facilities have been commissioned, but to date output of fuels from these sources has fallen well short of what is needed. Recent research and pilot demonstrations have highlighted the potential of algae as one of the most promising sources of sustainable liquid transportation fuels. Algae have also been established as unique biofactories for industrial, therapeutic, and nutraceutical co-products. Chlamydomonas reinhardtii's long established role in the field of basic research in green algae has paved the way for understanding algal metabolism and developing genetic engineering protocols. These tools are now being utilized in C. reinhardtii and in other algal species for the development of strains to maximize biofuels and bio-products yields from the lab to the field. PMID:25641390

  6. Cellular internalization and intracellular biotransformation of silver nanoparticles in Chlamydomonas reinhardtii.

    PubMed

    Wang, Songshan; Lv, Jitao; Ma, Jingyuan; Zhang, Shuzhen

    2016-10-01

    It is necessary to elucidate cellular internalization and intracellular biotransformation in order to accurately assess the toxicity and fate of nanoparticles after interaction with organisms. Therefore, this work employed a combination of high resolution imaging and in situ detection spectroscopic techniques to systematically investigate the intracellular localization, morphology and chemical speciation of silver in the cells of Chlamydomonas reinhardtii, a unicellular freshwater green alga, after exposure to AgNPs coated with polyvinylpyrrolidone at a concentration of 2.0 mg/L. High resolution secondary ion mass spectrometry and high-angle annular dark field scanning transmission electron microscopy together with energy dispersive spectroscopy and selected area electron diffraction collectively confirmed that after 48 h of exposure, AgNPs entered the periplasmic space after cellular internalization into the algal cells. Silver was also found to coexist with sulfur inside the cytoplasm in both crystalline and amorphous forms, which were further identified as β-Ag2S and silver thiolates with synchrotron X-ray absorption spectroscopy. In combination, these analyses demonstrated that silver inside algae could be attributed to the uptake and sequestration of Ag(+) ion released from AgNPs, which was further sequestrated into cellular compartments. This study provides solid evidence for particle internalization and biotransformation of AgNPs after interaction with algae. PMID:27098098

  7. Analysis of the high-affinity iron uptake system at the Chlamydomonas reinhardtii plasma membrane.

    PubMed

    Terzulli, Alaina; Kosman, Daniel J

    2010-05-01

    Multicopper ferroxidases play a vital role in iron metabolism in bacteria, fungi, algae, and mammals. Saccharomyces cerevisiae utilizes a channeling mechanism to couple the ferroxidase activity of Fet3p to Fe(3+) transport into the cell by Ftr1p. In contrast, the mechanisms by which mammals couple the ferroxidase reaction to iron trafficking is unclear. The human ferroxidases ceruloplasmin and hephaestin are twice the size of Fet3p and interact with proteins that are not expressed in fungi. Chlamydomonas FOX1 is a homolog of the human ferroxidases but likely supports iron uptake in a manner similar to that of yeast, since Chlamydomonas reinhardtii expresses a ferric iron permease homolog, FTR1. The results presented support this hypothesis. We show that FOX1 is trafficked to the plasma membrane and is oriented with its multicopper oxidase/ferroxidase domain in the exocytoplasmic space. Our analysis of FTR1 indicates its topology is similar to that of S. cerevisiae Ftr1p, with a potential exocytoplasmic iron channeling motif and two potential iron permeation motifs in membrane-spanning regions. We demonstrate that high-affinity iron uptake is dependent on FOX1 and the copper status of the cell. Kinetic inhibition of high-affinity iron uptake by a ferric iron chelator does not reflect the strength of the chelator, supporting a ferric iron channeling mechanism for high-affinity iron uptake in Chlamydomonas. Last, recombinant FOX1 (rFOX1) has been isolated in a partially holo form that exhibits the UV-visible absorbance spectrum of a multicopper oxidase and the catalytic activity of a ferroxidase. PMID:20348389

  8. The Hsp70 and Hsp40 Chaperones Influence Microtubule Stability in Chlamydomonas

    PubMed Central

    Silflow, Carolyn D.; Sun, Xiaoqing; Haas, Nancy A.; Foley, Joseph W.; Lefebvre, Paul A.

    2011-01-01

    Mutations at the APM1 and APM2 loci in the green alga Chlamydomonas reinhardtii confer resistance to phosphorothioamidate and dinitroaniline herbicides. Genetic interactions between apm1 and apm2 mutations suggest an interaction between the gene products. We identified the APM1 and APM2 genes using a map-based cloning strategy. Genomic DNA fragments containing only the DNJ1 gene encoding a type I Hsp40 protein rescue apm1 mutant phenotypes, conferring sensitivity to the herbicides and rescuing a temperature-sensitive growth defect. Lesions at five apm1 alleles include missense mutations and nucleotide insertions and deletions that result in altered proteins or very low levels of gene expression. The HSP70A gene, encoding a cytosolic Hsp70 protein known to interact with Hsp40 proteins, maps near the APM2 locus. Missense mutations found in three apm2 alleles predict altered Hsp70 proteins. Genomic fragments containing the HSP70A gene rescue apm2 mutant phenotypes. The results suggest that a client of the Hsp70–Hsp40 chaperone complex may function to increase microtubule dynamics in Chlamydomonas cells. Failure of the chaperone system to recognize or fold the client protein(s) results in increased microtubule stability and resistance to the microtubule-destabilizing effect of the herbicides. The lack of redundancy of genes encoding cytosolic Hsp70 and Hsp40 type I proteins in Chlamydomonas makes it a uniquely valuable system for genetic analysis of the function of the Hsp70 chaperone complex. PMID:21940683

  9. A steering mechanism for phototaxis in Chlamydomonas

    NASA Astrophysics Data System (ADS)

    Bennett, Rachel; Golestanian, Ramin

    2015-03-01

    Chlamydomonas shows both positive and negative phototaxis. It has a single eyespot near its equator and as the cell rotates during forward motion the light signal received by the eyespot varies. We use a simple mechanical model of Chlamydomonas that couples the flagellar beat pattern to the light intensity at the eyespot to demonstrate a mechanism for phototactic steering that is consistent with observations. The direction of phototaxis is controlled by a parameter in our model and the steering mechanism is robust to noise. In the dark, our model shows emergent run-and-tumble behavior and we see switching between directed phototaxis and run-and-tumble when we switch the light on and off.

  10. Altered Fermentative Metabolism in Chlamydomonas reinhardtii Mutants Lacking Pyruvate Formate Lyase and Both Pyruvate Formate Lyase and Alcohol Dehydrogenase[W

    PubMed Central

    Catalanotti, Claudia; Dubini, Alexandra; Subramanian, Venkataramanan; Yang, Wenqiang; Magneschi, Leonardo; Mus, Florence; Seibert, Michael; Posewitz, Matthew C.; Grossman, Arthur R.

    2012-01-01

    Chlamydomonas reinhardtii, a unicellular green alga, often experiences hypoxic/anoxic soil conditions that activate fermentation metabolism. We isolated three Chlamydomonas mutants disrupted for the pyruvate formate lyase (PFL1) gene; the encoded PFL1 protein catalyzes a major fermentative pathway in wild-type Chlamydomonas cells. When the pfl1 mutants were subjected to dark fermentative conditions, they displayed an increased flux of pyruvate to lactate, elevated pyruvate decarboxylation, ethanol accumulation, diminished pyruvate oxidation by pyruvate ferredoxin oxidoreductase, and lowered H2 production. The pfl1-1 mutant also accumulated high intracellular levels of lactate, succinate, alanine, malate, and fumarate. To further probe the system, we generated a double mutant (pfl1-1 adh1) that is unable to synthesize both formate and ethanol. This strain, like the pfl1 mutants, secreted lactate, but it also exhibited a significant increase in the levels of extracellular glycerol, acetate, and intracellular reduced sugars and a decrease in dark, fermentative H2 production. Whereas wild-type Chlamydomonas fermentation primarily produces formate and ethanol, the double mutant reroutes glycolytic carbon to lactate and glycerol. Although the metabolic adjustments observed in the mutants facilitate NADH reoxidation and sustained glycolysis under dark, anoxic conditions, the observed changes could not have been predicted given our current knowledge of the regulation of fermentation metabolism. PMID:22353371

  11. Taxonomic revision of Chlamydomonas subg. Amphichloris (Volvocales, Chlorophyceae), with resurrection of the genus Dangeardinia and descriptions of Ixipapillifera gen. nov. and Rhysamphichloris gen. nov.

    PubMed

    Nakada, Takashi; Tomita, Masaru; Wu, Jiunn-Tzong; Nozaki, Hisayoshi

    2016-04-01

    Chlamydomonas (Cd.) is one of the largest but most polyphyletic genera of freshwater unicellular green algae. It consists of 400-600 morphological species and requires taxonomic revision. Toward reclassification, each morphologically defined classical subgenus (or subgroup) should be examined using culture strains. Chlamydomonas subg. Amphichloris is characterized by a central nucleus between two axial pyrenoids, however, the phylogenetic structure of this subgenus has yet to be examined using molecular data. Here, we examined 12 strains including six newly isolated strains, morphologically identified as Chlamydomonas subg. Amphichloris, using 18S rRNA gene phylogeny, light microscopy, and mitochondria fluorescent microscopy. Molecular phylogenetic analyses revealed three independent lineages of the subgenus, separated from the type species of Chlamydomonas, Cd. reinhardtii. These three lineages were further distinguished from each other by light and fluorescent microscopy-in particular by the morphology of the papillae, chloroplast surface, stigmata, and mitochondria-and are here assigned to three genera: Dangeardinia emend., Ixipapillifera gen. nov., and Rhysamphichloris gen. nov. Based on the molecular and morphological data, two to three species were recognized in each genus, including one new species, I. pauromitos. In addition, Cd. deasonii, which was previously assigned to subgroup "Pleiochloris," was included in the genus Ixipapillifera as I. deasonii comb. nov. PMID:27037593

  12. Comparative genomics in Chlamydomonas and Plasmodium identifies an ancient nuclear envelope protein family essential for sexual reproduction in protists, fungi, plants, and vertebrates

    PubMed Central

    Ning, Jue; Otto, Thomas D.; Pfander, Claudia; Schwach, Frank; Brochet, Mathieu; Bushell, Ellen; Goulding, David; Sanders, Mandy; Lefebvre, Paul A.; Pei, Jimin; Grishin, Nick V.; Vanderlaan, Gary; Billker, Oliver; Snell, William J.

    2013-01-01

    Fertilization is a crucial yet poorly characterized event in eukaryotes. Our previous discovery that the broadly conserved protein HAP2 (GCS1) functioned in gamete membrane fusion in the unicellular green alga Chlamydomonas and the malaria pathogen Plasmodium led us to exploit the rare biological phenomenon of isogamy in Chlamydomonas in a comparative transcriptomics strategy to uncover additional conserved sexual reproduction genes. All previously identified Chlamydomonas fertilization-essential genes fell into related clusters based on their expression patterns. Out of several conserved genes in a minus gamete cluster, we focused on Cre06.g280600, an ortholog of the fertilization-related Arabidopsis GEX1. Gene disruption, cell biological, and immunolocalization studies show that CrGEX1 functions in nuclear fusion in Chlamydomonas. Moreover, CrGEX1 and its Plasmodium ortholog, PBANKA_113980, are essential for production of viable meiotic progeny in both organisms and thus for mosquito transmission of malaria. Remarkably, we discovered that the genes are members of a large, previously unrecognized family whose first-characterized member, KAR5, is essential for nuclear fusion during yeast sexual reproduction. Our comparative transcriptomics approach provides a new resource for studying sexual development and demonstrates that exploiting the data can lead to the discovery of novel biology that is conserved across distant taxa. PMID:23699412

  13. Photo-cycle dynamics of LOV1-His domain of phototropin from Chlamydomonas reinhardtii with roseoflavin monophosphate cofactor

    NASA Astrophysics Data System (ADS)

    Tyagi, A.; Penzkofer, A.; Mathes, T.; Hegemann, P.

    2010-09-01

    The wild-type phototropin protein phot from the green alga Chlamydomonas reinhardtii consists of two N-terminal LOV domains LOV1 and LOV2 with flavin mononucleotide (FMN) cofactor and a C-terminal serine-threonine kinase domain. It controls multiple steps in the sexual lifecycle of the alga. Here the LOV1-His domain of phot with modified cofactor is studied. FMN is replaced by roseoflavin monophosphate (8-dimethylamino-8-demethyl-FMN, RoFMN). The modified LOV1 domain is called RoLOV1. The photo-dynamics consequences of the cofactor change are studied. The absorption, emission, and photo-cyclic behaviour of LOV1-His and RoLOV1-His are compared. A spectroscopic characterisation of the cofactors FMN and RoFMN (roseoflavin) is given.

  14. Identification of a highly conserved hydroxyproline-rich glycoprotein in the cell walls of Chlamydomonas reinhardtii and two other Volvocales.

    PubMed

    Adair, W S; Appel, H

    1989-10-01

    The unicellular alga Chlamydomonas reinhardtii Dang, has a cell wall made entirely from hydroxyproline-rich glycoproteins (HRGPs). We recently employed a quantiative in vitro reconstitution system (Adair et al. 1987, J. Cell Biol. 105, 2373-2382) to assign outer-wall HRGPs of C. reinhardtii to specific sublayers, and describe the major interactions responsible for their assembly. Some of these interactions appear to involve relatively conserved HRGP domains, as evidenced by interspecific cell-wall reconstitution between C. reinhardtii and two multicellular Volvocales (Volvoxcarteri lyengar and Gonium pectorale Müller). In the present report we provide biochemical and immunological evidence that the outer cell-walls of V. carteri and G. pectorale both contain prominent HRGPs closely related to C. reinhardtii GP2. Identification of conserved GP2 homologues indicates a molecular basis for interspecific reconstitution and provides a useful avenue for characterization of HRGP domains mediating cell-wall formation in these algae. PMID:24201668

  15. Oleosin of subcellular lipid droplets evolved in green algae.

    PubMed

    Huang, Nan-Lan; Huang, Ming-Der; Chen, Tung-Ling L; Huang, Anthony H C

    2013-04-01

    In primitive and higher plants, intracellular storage lipid droplets (LDs) of triacylglycerols are stabilized with a surface layer of phospholipids and oleosin. In chlorophytes (green algae), a protein termed major lipid-droplet protein (MLDP) rather than oleosin on LDs was recently reported. We explored whether MLDP was present directly on algal LDs and whether algae had oleosin genes and oleosins. Immunofluorescence microscopy revealed that MLDP in the chlorophyte Chlamydomonas reinhardtii was associated with endoplasmic reticulum subdomains adjacent to but not directly on LDs. In C. reinhardtii, low levels of a transcript encoding an oleosin-like protein (oleolike) in zygotes-tetrads and a transcript encoding oleosin in vegetative cells transferred to an acetate-enriched medium were found in transcriptomes and by reverse transcription-polymerase chain reaction. The C. reinhardtii LD fraction contained minimal proteins with no detectable oleolike or oleosin. Several charophytes (advanced green algae) possessed low levels of transcripts encoding oleosin but not oleolike. In the charophyte Spirogyra grevilleana, levels of oleosin transcripts increased greatly in cells undergoing conjugation for zygote formation, and the LD fraction from these cells contained minimal proteins, two of which were oleosins identified via proteomics. Because the minimal oleolike and oleosins in algae were difficult to detect, we tested their subcellular locations in Physcomitrella patens transformed with the respective algal genes tagged with a Green Fluorescent Protein gene and localized the algal proteins on P. patens LDs. Overall, oleosin genes having weak and cell/development-specific expression were present in green algae. We present a hypothesis for the evolution of oleosins from algae to plants. PMID:23391579

  16. Experimental Genome-Wide Determination of RNA Polyadenylation in Chlamydomonas reinhardtii

    PubMed Central

    Bell, Stephen A.; Shen, Chi; Brown, Alishea; Hunt, Arthur G.

    2016-01-01

    The polyadenylation of RNA is a near-universal feature of RNA metabolism in eukaryotes. This process has been studied in the model alga Chlamydomonas reinhardtii using low-throughput (gene-by-gene) and high-throughput (transcriptome sequencing) approaches that recovered poly(A)-containing sequence tags which revealed interesting features of this critical process in Chlamydomonas. In this study, RNA polyadenylation has been studied using the so-called Poly(A) Tag Sequencing (PAT-Seq) approach. Specifically, PAT-Seq was used to study poly(A) site choice in cultures grown in four different media types—Tris-Phosphate (TP), Tris-Phosphate-Acetate (TAP), High-Salt (HS), and High-Salt-Acetate (HAS). The results indicate that: 1. As reported before, the motif UGUAA is the primary, and perhaps sole, cis-element that guides mRNA polyadenylation in the nucleus; 2. The scope of alternative polyadenylation events with the potential to change the coding sequences of mRNAs is limited; 3. Changes in poly(A) site choice in cultures grown in the different media types are very few in number and do not affect protein-coding potential; 4. Organellar polyadenylation is considerable and affects primarily ribosomal RNAs in the chloroplast and mitochondria; and 5. Organellar RNA polyadenylation is a dynamic process that is affected by the different media types used for cell growth. PMID:26730730

  17. A Gamete-specific, Sex-limited Homeodomain Protein in Chlamydomonas

    PubMed Central

    Kurvari, Venkatesh; Grishin, Nick V.; Snell, William J.

    1998-01-01

    During fertilization in Chlamydomonas, gametes of opposite mating types interact with each other through sex-specific adhesion molecules on their flagellar surfaces. Flagellar adhesion brings the cell bodies of the gametes into close contact and initiates a signal transduction pathway in preparation for cell–cell fusion. We have identified a cDNA, gsp1, whose transcript levels are upregulated during flagellar adhesion. The GSP1 polypeptide is a novel, gamete-specific homeodomain protein, the first to be identified in an alga. Its homeodomain shows significant identity with several higher plant homeodomain proteins. Although encoded by a single copy gene present in cells of both mating types, immunoblot analysis showed that GSP1 was expressed in mating type (mt)+ gametes, but was not detectable in mt− gametes or in vegetative cells of either mating type. Moreover, GSP1 appeared late during gametogenesis, suggesting that it may function during adhesion with mt− gametes or after zygote formation. GSP1 is expressed in imp11, mt− mutant gametes, which have a lesion in the mid gene involved in sex determination and exhibit many phenotypic characteristics of mt+ gametes. Thus, gsp1 is negatively regulated by mid and is the first molecule to be identified in Chlamydomonas that shows sex-limited expression. PMID:9864368

  18. Spontaneous Dominant Mutations in Chlamydomonas Highlight Ongoing Evolution by Gene Diversification

    PubMed Central

    Boulouis, Alix; Drapier, Dominique; Razafimanantsoa, Hélène; Wostrikoff, Katia; Tourasse, Nicolas J.; Pascal, Kevin; Girard-Bascou, Jacqueline; Vallon, Olivier; Wollman, Francis-André; Choquet, Yves

    2015-01-01

    We characterized two spontaneous and dominant nuclear mutations in the unicellular alga Chlamydomonas reinhardtii, ncc1 and ncc2 (for nuclear control of chloroplast gene expression), which affect two octotricopeptide repeat (OPR) proteins encoded in a cluster of paralogous genes on chromosome 15. Both mutations cause a single amino acid substitution in one OPR repeat. As a result, the mutated NCC1 and NCC2 proteins now recognize new targets that we identified in the coding sequences of the chloroplast atpA and petA genes, respectively. Interaction of the mutated proteins with these targets leads to transcript degradation; however, in contrast to the ncc1 mutation, the ncc2 mutation requires on-going translation to promote the decay of the petA mRNA. Thus, these mutants reveal a mechanism by which nuclear factors act on chloroplast mRNAs in Chlamydomonas. They illustrate how diversifying selection can allow cells to adapt the nuclear control of organelle gene expression to environmental changes. We discuss these data in the wider context of the evolution of regulation by helical repeat proteins. PMID:25804537

  19. CRISPR/Cas9-induced knockout and knock-in mutations in Chlamydomonas reinhardtii

    PubMed Central

    Shin, Sung-Eun; Lim, Jong-Min; Koh, Hyun Gi; Kim, Eun Kyung; Kang, Nam Kyu; Jeon, Seungjib; Kwon, Sohee; Shin, Won-Sub; Lee, Bongsoo; Hwangbo, Kwon; Kim, Jungeun; Ye, Sung Hyeok; Yun, Jae-Young; Seo, Hogyun; Oh, Hee-Mock; Kim, Kyung-Jin; Kim, Jin-Soo; Jeong, Won-Joong; Chang, Yong Keun; Jeong, Byeong-ryool

    2016-01-01

    Genome editing is crucial for genetic engineering of organisms for improved traits, particularly in microalgae due to the urgent necessity for the next generation biofuel production. The most advanced CRISPR/Cas9 system is simple, efficient and accurate in some organisms; however, it has proven extremely difficult in microalgae including the model alga Chlamydomonas. We solved this problem by delivering Cas9 ribonucleoproteins (RNPs) comprising the Cas9 protein and sgRNAs to avoid cytotoxicity and off-targeting associated with vector-driven expression of Cas9. We obtained CRISPR/Cas9-induced mutations at three loci including MAA7, CpSRP43 and ChlM, and targeted mutagenic efficiency was improved up to 100 fold compared to the first report of transgenic Cas9-induced mutagenesis. Interestingly, we found that unrelated vectors used for the selection purpose were predominantly integrated at the Cas9 cut site, indicative of NHEJ-mediated knock-in events. As expected with Cas9 RNPs, no off-targeting was found in one of the mutagenic screens. In conclusion, we improved the knockout efficiency by using Cas9 RNPs, which opens great opportunities not only for biological research but also industrial applications in Chlamydomonas and other microalgae. Findings of the NHEJ-mediated knock-in events will allow applications of the CRISPR/Cas9 system in microalgae, including “safe harboring” techniques shown in other organisms. PMID:27291619

  20. CRISPR/Cas9-induced knockout and knock-in mutations in Chlamydomonas reinhardtii.

    PubMed

    Shin, Sung-Eun; Lim, Jong-Min; Koh, Hyun Gi; Kim, Eun Kyung; Kang, Nam Kyu; Jeon, Seungjib; Kwon, Sohee; Shin, Won-Sub; Lee, Bongsoo; Hwangbo, Kwon; Kim, Jungeun; Ye, Sung Hyeok; Yun, Jae-Young; Seo, Hogyun; Oh, Hee-Mock; Kim, Kyung-Jin; Kim, Jin-Soo; Jeong, Won-Joong; Chang, Yong Keun; Jeong, Byeong-Ryool

    2016-01-01

    Genome editing is crucial for genetic engineering of organisms for improved traits, particularly in microalgae due to the urgent necessity for the next generation biofuel production. The most advanced CRISPR/Cas9 system is simple, efficient and accurate in some organisms; however, it has proven extremely difficult in microalgae including the model alga Chlamydomonas. We solved this problem by delivering Cas9 ribonucleoproteins (RNPs) comprising the Cas9 protein and sgRNAs to avoid cytotoxicity and off-targeting associated with vector-driven expression of Cas9. We obtained CRISPR/Cas9-induced mutations at three loci including MAA7, CpSRP43 and ChlM, and targeted mutagenic efficiency was improved up to 100 fold compared to the first report of transgenic Cas9-induced mutagenesis. Interestingly, we found that unrelated vectors used for the selection purpose were predominantly integrated at the Cas9 cut site, indicative of NHEJ-mediated knock-in events. As expected with Cas9 RNPs, no off-targeting was found in one of the mutagenic screens. In conclusion, we improved the knockout efficiency by using Cas9 RNPs, which opens great opportunities not only for biological research but also industrial applications in Chlamydomonas and other microalgae. Findings of the NHEJ-mediated knock-in events will allow applications of the CRISPR/Cas9 system in microalgae, including "safe harboring" techniques shown in other organisms. PMID:27291619

  1. An Indexed, Mapped Mutant Library Enables Reverse Genetics Studies of Biological Processes in Chlamydomonas reinhardtii.

    PubMed

    Li, Xiaobo; Zhang, Ru; Patena, Weronika; Gang, Spencer S; Blum, Sean R; Ivanova, Nina; Yue, Rebecca; Robertson, Jacob M; Lefebvre, Paul A; Fitz-Gibbon, Sorel T; Grossman, Arthur R; Jonikas, Martin C

    2016-02-01

    The green alga Chlamydomonas reinhardtii is a leading unicellular model for dissecting biological processes in photosynthetic eukaryotes. However, its usefulness has been limited by difficulties in obtaining mutants in specific genes of interest. To allow generation of large numbers of mapped mutants, we developed high-throughput methods that (1) enable easy maintenance of tens of thousands of Chlamydomonas strains by propagation on agar media and by cryogenic storage, (2) identify mutagenic insertion sites and physical coordinates in these collections, and (3) validate the insertion sites in pools of mutants by obtaining >500 bp of flanking genomic sequences. We used these approaches to construct a stably maintained library of 1935 mapped mutants, representing disruptions in 1562 genes. We further characterized randomly selected mutants and found that 33 out of 44 insertion sites (75%) could be confirmed by PCR, and 17 out of 23 mutants (74%) contained a single insertion. To demonstrate the power of this library for elucidating biological processes, we analyzed the lipid content of mutants disrupted in genes encoding proteins of the algal lipid droplet proteome. This study revealed a central role of the long-chain acyl-CoA synthetase LCS2 in the production of triacylglycerol from de novo-synthesized fatty acids. PMID:26764374

  2. High-Level Accumulation of Triacylglycerol and Starch in Photoautotrophically Grown Chlamydomonas debaryana NIES-2212.

    PubMed

    Toyoshima, Masakazu; Sato, Naoki

    2015-12-01

    Microalgae have the potential to produce triacylglycerol (TAG) and starch, which provide alternative sources of biofuel. A problem in using Chlamydomonas reinhardtii as a model for TAG production has been that this alga lacks phosphatidylcholine (PC), which is thought to be important for TAG synthesis in plants. We found that C. debaryana is one of the rare species of Chlamydomonas having PC. Here we show that this strain, grown under complete photoautotrophic conditions, accumulated TAG and starch up to 20 and 250 pg per cell, respectively, during the stationary phase without nutrient deprivation. Addition of nutrients in this state did not cause loss of TAG, which was found in dilution with fresh medium. The photosynthetically produced TAG contained a high level of monounsaturated fatty acids, which is a preferred property as a material for biodiesel. The oil bodies were present in the cytoplasm, either between the cytoplasmic membrane and the chloroplast or between the chloroplast and the nucleus, whereas the starch granules were present within the chloroplast. Oil bodies were also deposited as a broad layer in the peripheral space of the cytoplasm outside the chloroplast, and might be easily released from the cells by genetic, chemical or mechanical manipulation. These results suggest that C. debaryana is a promising seed organism for developing a good biofuel producer. PMID:26542110

  3. Atomic Resolution Modeling of the Ferredoxin:[FeFe] Hydrogenase Complex from Chlamydomonas reinhardtii

    PubMed Central

    Chang, Christopher H.; King, Paul W.; Ghirardi, Maria L.; Kim, Kwiseon

    2007-01-01

    The [FeFe] hydrogenases HydA1 and HydA2 in the green alga Chlamydomonas reinhardtii catalyze the final reaction in a remarkable metabolic pathway allowing this photosynthetic organism to produce H2 from water in the chloroplast. A [2Fe-2S] ferredoxin is a critical branch point in electron flow from Photosystem I toward a variety of metabolic fates, including proton reduction by hydrogenases. To better understand the binding determinants involved in ferredoxin:hydrogenase interactions, we have modeled Chlamydomonas PetF1 and HydA2 based on amino-acid sequence homology, and produced two promising electron-transfer model complexes by computational docking. To characterize these models, quantitative free energy calculations at atomic resolution were carried out, and detailed analysis of the interprotein interactions undertaken. The protein complex model we propose for ferredoxin:HydA2 interaction is energetically favored over the alternative candidate by 20 kcal/mol. This proposed model of the electron-transfer complex between PetF1 and HydA2 permits a more detailed view of the molecular events leading up to H2 evolution, and suggests potential mutagenic strategies to modulate electron flow to HydA2. PMID:17660315

  4. Photoinduced electric currents in carotenoid-deficient Chlamydomonas mutants reconstituted with retinal and its analogs.

    PubMed Central

    Sineshchekov, O A; Govorunova, E G; Dér, A; Keszthelyi, L; Nultsch, W

    1994-01-01

    Reconstitution of the photoelectric responses involved in photosensory transduction in "blind" cells of Chlamydomonas reinhardtii carotenoid-deficient mutants was studied by means of a recently developed population method. Both the photoreceptor current and the regenerative response can be restored by addition of all-trans-retinal, 9-demethyl-retinal, or dimethyl-octatrienal, while the retinal analogs prevented from 13-cis/trans isomerization, 13-demethyl-retinal and citral, are not effective. Fluence dependence, spectral sensitivity, and effect of hydroxylamine treatment on retinal-induced photoelectric responses are similar to those found earlier in green strains of Chlamydomonas, although an alternative mechanism of antenna directivity in white cells of reconstituted "blind" mutants (likely based on the focusing effect of the transparent cell bodies) leads to the reversed sign of phototaxis in mutant cells under the same conditions. The results obtained indicate that both photoreceptor current and regenerative response are initiated by the same or similar rhodopsins with arhaebacterial-like chromophore(s) and prove directly the earlier suggested identity of the photoreceptor pigment(s) involved in photomotile and photoelectric responses in flagellated algae. PMID:8075341

  5. VMP1-deficient Chlamydomonas exhibits severely aberrant cell morphology and disrupted cytokinesis

    PubMed Central

    2014-01-01

    Background The versatile Vacuole Membrane Protein 1 (VMP1) has been previously investigated in six species. It has been shown to be essential in macroautophagy, where it takes part in autophagy initiation. In addition, VMP1 has been implicated in organellar biogenesis; endo-, exo- and phagocytosis, and protein secretion; apoptosis; and cell adhesion. These roles underly its proven involvement in pancreatitis, diabetes and cancer in humans. Results In this study we analyzed a VMP1 homologue from the green alga Chlamydomonas reinhardtii. CrVMP1 knockdown lines showed severe phenotypes, mainly affecting cell division as well as the morphology of cells and organelles. We also provide several pieces of evidence for its involvement in macroautophagy. Conclusion Our study adds a novel role to VMP1's repertoire, namely the regulation of cytokinesis. Though the directness of the observed effects and the mechanisms underlying them remain to be defined, the protein's involvement in macroautophagy in Chlamydomonas, as found by us, suggests that CrVMP1 shares molecular characteristics with its animal and protist counterparts. PMID:24885763

  6. The Dynein Gene Family in Chlamydomonas Reinhardtii

    PubMed Central

    Porter, M. E.; Knott, J. A.; Myster, S. H.; Farlow, S. J.

    1996-01-01

    To correlate dynein heavy chain (Dhc) genes with flagellar mutations and gain insight into the function of specific dynein isoforms, we placed eight members of the Dhc gene family on the genetic map of Chlamydomonas. Using a PCR-based strategy, we cloned 11 Dhc genes from Chlamydomonas. Comparisons with other Dhc genes indicate that two clones correspond to genes encoding the alpha and beta heavy chains of the outer dynein arm. Alignment of the predicted amino acid sequences spanning the nucleotide binding site indicates that the remaining nine clones can be subdivided into three groups that are likely to include representatives of the inner-arm Dhc isoforms. Gene-specific probes reveal that each clone represents a single-copy gene that is expressed as a transcript of the appropriate size (>13 kb) sufficient to encode a high molecular weight Dhc polypeptide. The expression of all nine genes is upregulated in response to deflagellation, suggesting a role in axoneme assembly or motility. Restriction fragment length polymorphisms between divergent C. reinhardtii strains have been used to place each Dhc gene on the genetic map of Chlamydomonas. These studies lay the groundwork for correlating defects in different Dhc genes with specific flagellar mutations. PMID:8889521

  7. Effect of Triacontanol on Chlamydomonas1

    PubMed Central

    Houtz, Robert L.; Ries, Stanley K.; Tolbert, N. E.

    1985-01-01

    Increased photosynthetic CO2 assimilation by Chlamydomonas reinhardtii cells treated with triacontanol (TRIA) was not due to changes in glycolate excretion, CO2 compensation point, or the sensitivity of photosynthetic CO2 assimilation to O2. Kinetic analysis of TRIA-treated cells showed that the increase in photosynthetic CO2 assimilation was a result of an increase in the apparent Vmax for intact cells. The total activity of ribulose-P2 carboxylase/oxygenase was higher in cell lysates from TRIA-treated cells. However quantification of this enzyme concentration by binding of [14C]carboxyarabinitol-P2 did not show an increase in TRIA-treated cells. Thus, there was an increase in the specific activity of ribulose-P2 carboxylase/oxygenase extracted from Chlamydomonas cells treated with TRIA. TRIA alone had no effect on the activity of the enzyme in cell lysates from Chlamydomonas or purified from spinach (Spinacia oleracea L.) leaves. The ribulose-P2 pool was 50 to 60% higher in cells treated with TRIA that were assayed for photosynthetic CO2 assimilation at high- and low-CO2. TRIA also increased ribulose-P2 levels in the absence of CO2 in the light with atmospheres of N2 or N2 with 21% O2. PMID:16664415

  8. The Haemoglobins of Algae.

    PubMed

    Johnson, Eric A; Lecomte, Juliette T J

    2015-01-01

    In the last few years, advances in algal research have identified the participation of haemoglobins in nitrogen metabolism and the management of reactive nitrogen and oxygen species. This chapter summarises the state of knowledge concerning algal haemoglobins with a focus on the most widely used model system, namely, Chlamydomonas reinhardtii. Genetic, physiologic, structural, and chemical information is compiled to provide a framework for further studies. PMID:26616518

  9. Epigenetic silencing of a foreign gene in nuclear transformants of Chlamydomonas.

    PubMed Central

    Cerutti, H; Johnson, A M; Gillham, N W; Boynton, J E

    1997-01-01

    The unstable expression of introduced genes poses a serious problem for the application of transgenic technology in plants. In transformants of the unicellular green alga Chlamydomonas reinhardtii, expression of a eubacterial aadA gene, conferring spectinomycin resistance, is transcriptionally suppressed by a reversible epigenetic mechanism(s). Variations in the size and frequency of colonies surviving on different concentrations of spectinomycin as well as the levels of transcriptional activity of the introduced transgene(s) suggest the existence of intermediate expression states in genetically identical cells. Gene silencing does not correlate with methylation of the integrated DNA and does not involve large alterations in its chromatin structure, as revealed by digestion with restriction endonucleases and DNase I. Transgene repression is enhanced by lower temperatures, similar to position effect variegation in Drosophila. By analogy to epigenetic phenomena in several eukaryotes, our results suggest a possible role for (hetero)chromatic chromosomal domains in transcriptional inactivation. PMID:9212467

  10. Efficient expression of green fluorescent protein (GFP) mediated by a chimeric promoter in Chlamydomonas reinhardtii

    NASA Astrophysics Data System (ADS)

    Wu, Jinxia; Hu, Zhangli; Wang, Chaogang; Li, Shuangfei; Lei, Anping

    2008-08-01

    To improve the expression efficiency of exogenous genes in Chlamydomonas reinhardtii, a high efficient expression vector was constructed. Green fluorescent protein (GFP) was expressed in C. reinhardtii under the control of promoters: RBCS2 and HSP70A-RBCS2. Efficiency of transformation and expression were compared between two transgenic algae: RBCS2 mediated strain Tran-I and HSP70A-RBCS2 mediated strain Tran-II. Results show that HSP70A-RBCS2 could improve greatly the transformation efficiency by approximately eightfold of RBCS2, and the expression efficiency of GFP in Tran-II was at least double of that in Tran-I. In addition, a threefold increase of GFP in Tran-II was induced by heat shock at 40°C. All of the results demonstrated that HSP70A-RBCS2 was more efficient than RBCS2 in expressing exogenous gene in C. reinhardtii.

  11. Measurement of swimming force generation during flagella regeneration in Chlamydomonas reinhardtii

    NASA Astrophysics Data System (ADS)

    Yukich, John N.; Shaban, Mona; Clodfelter, Catherine; Bernd, Karen

    2007-11-01

    The green alga Chlamydomonas reinhardtii has been at the forefront of many studies investigating the establishment and function of flagella in facilitating cellular motility. Previously we reported an intriguing pattern during flagella regeneration in which increases in force do not always correspond with increase in flagella length. That work made direct measurement of maximum flagellar swimming force by measuring the cell's ability to escape from an optical trap (optical tweezers). Here, we report on optimization and automation of the force measurement using power spectral density calibration of the trap and distance of periodic displacement from the trap center. This process yields an average value for the swimming force. The intriguing pattern described for maximum swimming force is also evident in the average swimming force data, suggesting that the phenomenon reflects a change in flagella functionality during regeneration.

  12. Antagonistic and synergistic effects of light irradiation on the effects of copper on Chlamydomonas reinhardtii.

    PubMed

    Cheloni, Giulia; Cosio, Claudia; Slaveykova, Vera I

    2014-10-01

    The present study showed the important role of light intensity and spectral composition on Cu uptake and effects on green alga Chlamydomonas reinhardtii. High-intenisty light (HL) increased cellular Cu concentrations, but mitigated the Cu-induced decrease in chlorophyll fluorescence, oxidative stress and lipid peroxidation at high Cu concentrations, indicating that Cu and HL interact in an antagonistic manner. HL up-regulated the transcription of genes involved in the antioxidant response in C. reinhardtii and thus reduced the oxidative stress upon exposure to Cu and HL. Combined exposure to Cu and UVBR resulted in an increase of cellular Cu contents and caused severe oxidative damage to the cells. The observed effects were higher than the sum of the effects corresponding to exposure to UVBR or Cu alone suggesting a synergistic interaction. PMID:25072593

  13. Inhibition of Plastocyanin to P700+ Electron Transfer in Chlamydomonas reinhardtii by Hyperosmotic Stress1

    PubMed Central

    Cruz, Jeffrey A.; Salbilla, Brian A.; Kanazawa, Atsuko; Kramer, David M.

    2001-01-01

    Oxygen electrode and fluorescence studies demonstrate that linear electron transport in the freshwater alga Chlamydomonas reinhardtii can be completely abolished by abrupt hyperosmotic shock. We show that the most likely primary site of inhibition of electron transfer by hyperosmotic shock is a blockage of electron transfer between plastocyanin (PC) or cytochrome c6 and P700. The effects on this reaction were reversible upon dilution of the osmolytes and the stability of plastocyanin or photosystem (PS) I was unaffected. Electron micrographs of osmotically shocked cells showed a significant decrease in the thylakoid lumen volume. Comparison of estimated lumenal width with the x-ray structures of plastocyanin and PS I suggest that lumenal space contracts during HOS so as to hinder the movement of docking to PS I of plastocyanin or cytochrome c6. PMID:11706196

  14. Some observations on the carbon dioxide burst in chlorella and chlamydomonas.

    PubMed

    Bunt, J S

    1970-02-01

    In the course of mass spectrometer studies with the algae Chlorella and Chlamydomonas, data were obtained which indicate that the CO(2) burst and gulp are sensitive to oxygen. Furthermore, the CO(2) burst was found to be strongly suppressed when wave lengths shorter than 460 nanometers were blocked at intensities adequate to saturate photosynthesis. Under appropriate conditions at 30 degrees , the CO(2) burst was interrupted by a brief CO(2) gulp and the post illumination gulp by a brief burst of CO(2). The post illumination gulp of CO(2) could be induced during illumination by interposition of a filter blocking wave lengths shorter than 460 nanometers. These data are discussed in relation to earlier reports of the phenomenon and briefly as they affect the detection of photorespiration. PMID:16657291

  15. Membrane-Associated Polypeptides Induced in Chlamydomonas by Limiting CO(2) Concentrations.

    PubMed

    Spalding, M H; Jeffrey, M

    1989-01-01

    Chlamydomonas reinhardtii and other unicellular green algae have a high apparent affinity for CO(2), little O(2) inhibition of photosynthesis, and reduced photorespiration. These characteristics result from operation of a CO(2)-concentrating system. The CO(2)-concentrating system involves active inorganic carbon transport and is under environmental control. Cells grown at limiting CO(2) concentrations have inorganic carbon transport activity, but cells grown at 5% CO(2) do not. Four membrane-associated polypeptides (M(r) 19, 21, 35, and 36 kilodaltons) have been identified which either appear or increase in abundance during adaptation to limiting CO(2) concentrations. The appearance of two of the polypeptides occurs over roughly the same time course as the appearance of the CO(2)-concentrating system activity in response to CO(2) limitation. PMID:16666503

  16. Experimental evolution of an alternating uni- and multicellular life cycle in Chlamydomonas reinhardtii

    PubMed Central

    Ratcliff, William C.; Herron, Matthew D.; Howell, Kathryn; Pentz, Jennifer T.; Rosenzweig, Frank; Travisano, Michael

    2013-01-01

    The transition to multicellularity enabled the evolution of large, complex organisms, but early steps in this transition remain poorly understood. Here we show that multicellular complexity, including development from a single cell, can evolve rapidly in a unicellular organism that has never had a multicellular ancestor. We subject the alga Chlamydomonas reinhardtii to conditions that favour multicellularity, resulting in the evolution of a multicellular life cycle in which clusters reproduce via motile unicellular propagules. While a single-cell genetic bottleneck during ontogeny is widely regarded as an adaptation to limit among-cell conflict, its appearance very early in this transition suggests that it did not evolve for this purpose. Instead, we find that unicellular propagules are adaptive even in the absence of intercellular conflict, maximizing cluster-level fecundity. These results demonstrate that the unicellular bottleneck, a trait essential for evolving multicellular complexity, can arise rapidly via co-option of the ancestral unicellular form. PMID:24193369

  17. Membrane-associated polypeptides induced in Chlamydomonas by limiting CO sub 2 concentrations

    SciTech Connect

    Spalding, M.H.; Jeffrey, M. )

    1989-01-01

    Chlamydomonas reinhardtii and other unicellular green algae have a high apparent affinity for CO{sub 2}, little O{sub 2} inhibition of photosynthesis, and reduced photorespiration. These characteristics result from operation of a CO{sub 2}-concentrating system. The CO{sub 2}-concentrating system involves active inorganic carbon transport and is under environmental control. Cells grown at limiting CO{sub 2} concentrations have inorganic carbon transport activity, but cells grown at 5% CO{sub 2} do not. Four membrane-associated polypeptides (M{sub r}, 19, 21, 35, and 36 kilodaltons) have been identified which either appear or increase in abundance during adaptation to limiting CO{sub 2} concentrations. The appearance of two of the polypeptides occurs over roughly the same time course as the appearance of the CO{sub 2}-concentrating system activity in response to CO{sub 2} limitation.

  18. Brownian dynamics and molecular dynamics study of the association between hydrogenase and ferredoxin from Chlamydomonas reinhardtii.

    PubMed

    Long, Hai; Chang, Christopher H; King, Paul W; Ghirardi, Maria L; Kim, Kwiseon

    2008-10-01

    The [FeFe] hydrogenase from the green alga Chlamydomonas reinhardtii can catalyze the reduction of protons to hydrogen gas using electrons supplied from photosystem I and transferred via ferredoxin. To better understand the association of the hydrogenase and the ferredoxin, we have simulated the process over multiple timescales. A Brownian dynamics simulation method gave an initial thorough sampling of the rigid-body translational and rotational phase spaces, and the resulting trajectories were used to compute the occupancy and free-energy landscapes. Several important hydrogenase-ferredoxin encounter complexes were identified from this analysis, which were then individually simulated using atomistic molecular dynamics to provide more details of the hydrogenase and ferredoxin interaction. The ferredoxin appeared to form reasonable complexes with the hydrogenase in multiple orientations, some of which were good candidates for inclusion in a transition state ensemble of configurations for electron transfer. PMID:18621810

  19. [LIGHT-DEPENDENT SYNTHESIS OF CELL MEMBRANES IN THE Brc-1 MUTANT OF CHLAMYDOMONAS REINHARDTII].

    PubMed

    Semenova, G A; Chekunova, E M; Ladygin, V G

    2015-01-01

    The structural organization of cells of the Brc-1 mutant of the unicellular green algae Chlamydomonas reinhardtii grown in the light and in the dark has been studied. The Brc-1 mutant contains the brc-1 mutation in the nucleus gene LTS3. In the light, all membrane structures in mutant cells form normally and are well developed. In the dark under heterotrophic conditions, the mutant cells grew and divided well, however, all its cell membranes: plasmalemma, tonoplast, mitochondrial membranes, membranes of the nucleus shell and chloroplast, thylakoids, and the membranes of dictiosomes of the Golgi apparatus were not detected. In the dark under heterotrophic conditions, mutant cells well grow and divide. It were shown that a short-term (1-10 min) exposure of Brc-1 mutant cells to light leads to the restoration of all above-mentioned membrane structures. Possible reasons for the alterations of membrane structures are discussed. PMID:26281212

  20. [Harmful algae and health].

    PubMed

    Kankaanpää, Harri T

    2011-01-01

    Harmful algae are a worldwide problem. Phycotoxins is a general term for toxic compounds produced by harmful species of the phytoplankton. This review deals with the occurrence of harmful algae and phycotoxins in the Baltic Sea and other domestic waters, the ways of getting exposed to them, and their effects. Advice on how to avoid the exposure is provided. PMID:21834336

  1. MEETING: Chlamydomonas Annotation Jamboree - October 2003

    SciTech Connect

    Grossman, Arthur R

    2007-04-13

    Shotgun sequencing of the nuclear genome of Chlamydomonas reinhardtii (Chlamydomonas throughout) was performed at an approximate 10X coverage by JGI. Roughly half of the genome is now contained on 26 scaffolds, all of which are at least 1.6 Mb, and the coverage of the genome is ~95%. There are now over 200,000 cDNA sequence reads that we have generated as part of the Chlamydomonas genome project (Grossman, 2003; Shrager et al., 2003; Grossman et al. 2007; Merchant et al., 2007); other sequences have also been generated by the Kasuza sequence group (Asamizu et al., 1999; Asamizu et al., 2000) or individual laboratories that have focused on specific genes. Shrager et al. (2003) placed the reads into distinct contigs (an assemblage of reads with overlapping nucleotide sequences), and contigs that group together as part of the same genes have been designated ACEs (assembly of contigs generated from EST information). All of the reads have also been mapped to the Chlamydomonas nuclear genome and the cDNAs and their corresponding genomic sequences have been reassembled, and the resulting assemblage is called an ACEG (an Assembly of contiguous EST sequences supported by genomic sequence) (Jain et al., 2007). Most of the unique genes or ACEGs are also represented by gene models that have been generated by the Joint Genome Institute (JGI, Walnut Creek, CA). These gene models have been placed onto the DNA scaffolds and are presented as a track on the Chlamydomonas genome browser associated with the genome portal (http://genome.jgi-psf.org/Chlre3/Chlre3.home.html). Ultimately, the meeting grant awarded by DOE has helped enormously in the development of an annotation pipeline (a set of guidelines used in the annotation of genes) and resulted in high quality annotation of over 4,000 genes; the annotators were from both Europe and the USA. Some of the people who led the annotation initiative were Arthur Grossman, Olivier Vallon, and Sabeeha Merchant (with many individual

  2. Combined intracellular nitrate and NIT2 effects on storage carbohydrate metabolism in Chlamydomonas

    PubMed Central

    Vigeolas, H.

    2014-01-01

    Microalgae are receiving increasing attention as alternative production systems for renewable energy such as biofuel. The photosynthetic alga Chlamydomonas reinhardtii is widely recognized as the model system to study all aspects of algal physiology, including the molecular mechanisms underlying the accumulation of starch and triacylglycerol (TAG), which are the precursors of biofuel. All of these pathways not only require a carbon (C) supply but also are strongly dependent on a source of nitrogen (N) to sustain optimal growth rate and biomass production. In order to gain a better understanding of the regulation of C and N metabolisms and the accumulation of storage carbohydrates, the effect of different N sources (NH4NO3 and ) on primary metabolism using various mutants impaired in either NIA1, NIT2 or both loci was performed by metabolic analyses. The data demonstrated that, using NH4NO3, nia1 strain displayed the most striking phenotype, including an inhibition of growth, accumulation of intracellular nitrate, and strong starch and TAG accumulation. The measurements of the different C and N intermediate levels (amino, organic, and fatty acids), together with the determination of acetate and remaining in the medium, clearly excluded the hypothesis of a slower and acetate assimilation in this mutant in the presence of NH4NO3. The results provide evidence of the implication of intracellular nitrate and NIT2 in the control of C partitioning into different storage carbohydrates under mixotrophic conditions in Chlamydomonas. The underlying mechanisms and implications for strategies to increase biomass yield and storage product composition in oleaginous algae are discussed. PMID:24187418

  3. Algae Derived Biofuel

    SciTech Connect

    Jahan, Kauser

    2015-03-31

    One of the most promising fuel alternatives is algae biodiesel. Algae reproduce quickly, produce oils more efficiently than crop plants, and require relatively few nutrients for growth. These nutrients can potentially be derived from inexpensive waste sources such as flue gas and wastewater, providing a mutual benefit of helping to mitigate carbon dioxide waste. Algae can also be grown on land unsuitable for agricultural purposes, eliminating competition with food sources. This project focused on cultivating select algae species under various environmental conditions to optimize oil yield. Membrane studies were also conducted to transfer carbon di-oxide more efficiently. An LCA study was also conducted to investigate the energy intensive steps in algae cultivation.

  4. Functional and Spectroscopic Characterization of Chlamydomonas reinhardtii Truncated Hemoglobins

    PubMed Central

    Droghetti, Enrica; Tundo, Grazia R.; Sanz-Luque, Emanuel; Polticelli, Fabio; Visca, Paolo; Smulevich, Giulietta; Ascenzi, Paolo; Coletta, Massimo

    2015-01-01

    The single-cell green alga Chlamydomonas reinhardtii harbors twelve truncated hemoglobins (Cr-TrHbs). Cr-TrHb1-1 and Cr-TrHb1-8 have been postulated to be parts of the nitrogen assimilation pathway, and of a NO-dependent signaling pathway, respectively. Here, spectroscopic and reactivity properties of Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4, all belonging to clsss 1 (previously known as group N or group I), are reported. The ferric form of Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4 displays a stable 6cLS heme-Fe atom, whereas the hexa-coordination of the ferrous derivative appears less strongly stabilized. Accordingly, kinetics of azide binding to ferric Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4 are independent of the ligand concentration. Conversely, kinetics of CO or NO2− binding to ferrous Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4 are ligand-dependent at low CO or NO2− concentrations, tending to level off at high ligand concentrations, suggesting the presence of a rate-limiting step. In agreement with the different heme-Fe environments, the pH-dependent kinetics for CO and NO2−binding to ferrous Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4 are characterized by different ligand-linked protonation events. This raises the question of whether the simultaneous presence in C. reinhardtii of multiple TrHb1s may be related to different regulatory roles. PMID:25993270

  5. Functional and Spectroscopic Characterization of Chlamydomonas reinhardtii Truncated Hemoglobins.

    PubMed

    Ciaccio, Chiara; Ocaña-Calahorro, Francisco; Droghetti, Enrica; Tundo, Grazia R; Sanz-Luque, Emanuel; Polticelli, Fabio; Visca, Paolo; Smulevich, Giulietta; Ascenzi, Paolo; Coletta, Massimo

    2015-01-01

    The single-cell green alga Chlamydomonas reinhardtii harbors twelve truncated hemoglobins (Cr-TrHbs). Cr-TrHb1-1 and Cr-TrHb1-8 have been postulated to be parts of the nitrogen assimilation pathway, and of a NO-dependent signaling pathway, respectively. Here, spectroscopic and reactivity properties of Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4, all belonging to clsss 1 (previously known as group N or group I), are reported. The ferric form of Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4 displays a stable 6cLS heme-Fe atom, whereas the hexa-coordination of the ferrous derivative appears less strongly stabilized. Accordingly, kinetics of azide binding to ferric Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4 are independent of the ligand concentration. Conversely, kinetics of CO or NO2- binding to ferrous Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4 are ligand-dependent at low CO or NO2- concentrations, tending to level off at high ligand concentrations, suggesting the presence of a rate-limiting step. In agreement with the different heme-Fe environments, the pH-dependent kinetics for CO and NO2-binding to ferrous Cr-TrHb1-1, Cr-TrHb1-2, and Cr-TrHb1-4 are characterized by different ligand-linked protonation events. This raises the question of whether the simultaneous presence in C. reinhardtii of multiple TrHb1s may be related to different regulatory roles. PMID:25993270

  6. Sustained hydrogen photoproduction by Chlamydomonas reinhardtii: Effects of culture parameters.

    PubMed

    Kosourov, Sergey; Tsygankov, Anatoly; Seibert, Michael; Ghirardi, Maria L

    2002-06-30

    The green alga, Chlamydomonas reinhardtii, is capable of sustained H(2) photoproduction when grown under sulfur-deprived conditions. This phenomenon is a result of the partial deactivation of photosynthetic O(2)-evolution activity in response to sulfur deprivation. At these reduced rates of water-oxidation, oxidative respiration under continuous illumination can establish an anaerobic environment in the culture. After 10-15 hours of anaerobiosis, sulfur-deprived algal cells induce a reversible hydrogenase and start to evolve H(2) gas in the light. Using a computer-monitored photobioreactor system, we investigated the behavior of sulfur-deprived algae and found that: (1) the cultures transition through five consecutive phases: an aerobic phase, an O(2)-consumption phase, an anaerobic phase, a H(2)-production phase and a termination phase; (2) synchronization of cell division during pre-growth with 14:10 h light:dark cycles leads to earlier establishment of anaerobiosis in the cultures and to earlier onset of the H(2)-production phase; (3) re-addition of small quantities of sulfate (12.5-50 microM MgSO(4), final concentration) to either synchronized or unsynchronized cell suspensions results in an initial increase in culture density, a higher initial specific rate of H(2) production, an increase in the length of the H(2)-production phase, and an increase in the total amount of H(2) produced; and (4) increases in the culture optical density in the presence of 50 microM sulfate result in a decrease in the initial specific rates of H(2) production and in an earlier start of the H(2)-production phase with unsynchronized cells. We suggest that the effects of sulfur re-addition on H(2) production, up to an optimal concentration, are due to an increase in the residual water-oxidation activity of the algal cells. We also demonstrate that, in principle, cells synchronized by growth under light:dark cycles can be used in an outdoor H(2)-production system without loss of

  7. CONTRIBUTION OF MARINE ALGAE TO TRIHALOMETHANE PRODUCTION IN CHLORINATED ESTUARINE WATER

    EPA Science Inventory

    Three species of marine algae representing major taxonomic groups of phytoplankton, Isochrysis galbana (Chrysophyceae), Carteria sp. (Chlorophyceae), and Thalassiosira pseudonana (Bacillariphyceae), were utilized to investigate the potential of natural occurring chlorophyll a of ...

  8. Acclimation of Chlamydomonas reinhardtii to ultraviolet radiation and its impact on chemical toxicity.

    PubMed

    Korkaric, Muris; Xiao, Mao; Behra, Renata; Eggen, Rik I L

    2015-10-01

    The toxicity of chemical pollutants can be modulated under stressful environmental conditions, such as increased temperature, salinity or ultraviolet radiation (UVR), due to the interaction of effects during simultaneous stressor exposure. However, organisms may acclimate to such conditions by activation of physiological and biochemical defence mechanisms. In sequential exposures, organisms acclimated to environmental stressors may display an increased sensitivity or co-tolerance towards chemical pollutants. It has been suggested that co-tolerance might be expected for similarly acting stressors due to common defence mechanisms. To test this for combinations of UVR and chemical stressors, we first acclimatized the model green alga Chlamydomonas reinhardtii to UVR and subsequently compared the sensitivity of UVR pre-exposed and control algae towards chemicals. Selected chemicals all act on photosynthesis and thus share a common physiological target, but display distinct toxicity mechanisms. Results showed that UVR pre-exposure for four days partially inhibited algal growth and photosynthesis, but also increased algal tolerance to higher UVR levels, confirming UVR acclimation. HPLC analysis of algal pigments indicated that UVR acclimation might in part be explained by the protective function of lutein while the contribution of UVR absorbing compounds was less clear. Challenge exposure to chemicals in the absence of UVR showed that acclimated algae were co-tolerant to the photosensitizer rose bengal, but not to the herbicides paraquat and diuron, suggesting that the fast physiological and biochemical defence mechanisms that conferred tolerance of algae towards higher UVR levels were related to singlet oxygen defence. The presented study suggests that knowledge of the molecular toxicity mechanisms of chemicals, rather than their general physiological target, is needed in order to predict co-tolerance between environmental and chemical stressors. PMID:26349947

  9. Regulation of Flagellar Length in Chlamydomonas

    PubMed Central

    Wilson, Nedra F.; Iyer, Janaki Kannan; Buchheim, Julie A.; Meek, William

    2008-01-01

    Chlamydomonas reinhardtii has two apically localized flagella that are maintained at an equal and appropriate length. Assembly and maintenance of flagella requires a microtubule-based transport system known as intraflagellar transport (IFT). During IFT, proteins destined for incorporation into or removal from a flagellum are carried along doublet microtubules via IFT particles. Regulation of IFT activity therefore is pivotal in determining the length of a flagellum. Reviewed is our current understanding of the role of IFT and signal transduction pathways in the regulation of flagellar length. PMID:18692148

  10. Direct transesterification of Oedogonium sp. oil be using immobilized isolated novel Bacillus sp. lipase.

    PubMed

    Sivaramakrishnan, Ramachandran; Muthukumar, Karuppan

    2014-01-01

    This work emphasizes the potential of the isolated Bacillus sp. lipase for the production of fatty acid methyl ester by the direct transesterification of Oedogonium sp. of macroalgae. Dimethyl carbonate was used as the extraction solvent and also as the reactant. The effect of solvent/algae ratio, water addition, catalyst, temperature, stirring and time on the direct transesterification was studied. The highest fatty acid methyl ester yield obtained under optimum conditions (5 g Oedogonium sp. powder, 7.5 ml of solvent (dimethyl carbonate)/g of algae, 8% catalyst (%wt/wt of oil), distilled water 1% (wt/wt of algae), 36 h, 55°C and 180 rpm) was 82%. Final product was subjected to thermogravimetric analysis and (1)H NMR analysis. The results showed that the isolated enzyme has good potential in catalyzing the direct transesterification of algae, and the dimethyl carbonate did not affect the activity of the isolated lipase. PMID:23890544

  11. Microfluidic one-way streets for algae

    NASA Astrophysics Data System (ADS)

    Dunkel, Jorn; Kantsler, Vasily; Polin, Marco; Goldstein, Raymond E.

    2012-02-01

    Controlling locomotion and transport of microorganisms is a key challenge in the development of future biotechnological applications. Here, we demonstrate the use of optimized microfluidic ratchets to rectify the mean swimming direction in suspensions of the unicellular green alga Chlamydomonas reinhardtii, which is a promising candidate for the photosynthetic production of hydrogen. To assess the potential of microfluidic barriers for the manipulation of algal swimming, we studied first the scattering of individual C. reinhardtii from solid boundaries. High-speed imaging reveals the surprising result that these quasi-spherical ``puller''-type microswimmers primarily interact with surfaces via direct flagellar contact, whereas hydrodynamic effects play a subordinate role. A minimal theoretical model, based on run-and-turn motion and the experimentally measured surface-scattering law, predicts the existence of optimal wedge-shaped ratchets that maximize rectification of initially uniform suspensions. We confirm this prediction in experimental measurements with different geometries. Since the mechano-elastic properties of eukaryotic flagella are conserved across many genera, we expect that our results and methods are applicable to a broad class of biflagellate microorganisms.

  12. BIOCONCENTRATION OF A HEXACHLOROBIPHENYL IN GREAT LAKES PLANKTONIC ALGAE

    EPA Science Inventory

    The bioconcentration of 2,4,5,2',4',5'-hexachlorobiphenyl (HCB) was examined in the Great Lakes algae Fragilaria crotonensis, Ankistrodesmus falcatus, and Microcystis sp. The bioconcentration factors varied from species to species, whether they were expressed in terms of cell num...

  13. [An experiment with Chlamydomonas reinhardtii on the Kosmos-2044 biosatellite].

    PubMed

    Gavrilova, O V; Gabova, A V; Goriainova, L N; Filatova, E V

    1992-01-01

    Space experiment with Chlamydomonas reinhardtii demonstrated that the microgravity effects were noted in Chlamydomonas at both cellular and population levels: in space the cell size is increased, stage of active growth of the culture is extended, it contains the juvenile vegetative motile cells in greater quantities. Ultrastructural analysis indicated that in microgravity the changes in shape, structure and distribution of intracellular organelles and in volume ratio of organelles and cytoplasma are absent. Chlamydomonas data are in line with the results of the Infusoria and Chlorella experiments. PMID:1307032

  14. The plastid genome of the red alga Laurencia.

    PubMed

    Verbruggen, Heroen; Costa, Joana F

    2015-06-01

    We present the 174,935 nt long plastid genome of the red alga Laurencia sp. JFC0032. It is the third plastid genome characterized for the largest order of red algae (Ceramiales). The circular-mapping plastid genome is small compared to most florideophyte red algae, and our comparisons show a trend toward smaller plastid genome sizes in the family Rhodomelaceae, independent from a similar trend in Cyanidiophyceae. The Laurencia genome is densely packed with 200 annotated protein-coding genes (188 widely conserved, 3 open reading frames shared with other red algae and 9 hypothetical coding regions). It has 29 tRNAs, a single-copy ribosomal RNA cistron, a tmRNA, and the RNase P RNA. PMID:26986672

  15. Analytical approaches to photobiological hydrogen production in unicellular green algae.

    PubMed

    Hemschemeier, Anja; Melis, Anastasios; Happe, Thomas

    2009-01-01

    Several species of unicellular green algae, such as the model green microalga Chlamydomonas reinhardtii, can operate under either aerobic photosynthesis or anaerobic metabolism conditions. A particularly interesting metabolic condition is that of "anaerobic oxygenic photosynthesis", whereby photosynthetically generated oxygen is consumed by the cell's own respiration, causing anaerobiosis in the culture in the light, and induction of the cellular "hydrogen metabolism" process. The latter entails an alternative photosynthetic electron transport pathway, through the oxygen-sensitive FeFe-hydrogenase, leading to the light-dependent generation of molecular hydrogen in the chloroplast. The FeFe-hydrogenase is coupled to the reducing site of photosystem-I via ferredoxin and is employed as an electron-pressure valve, through which electrons are dissipated, thus permitting a sustained electron transport in the thylakoid membrane of photosynthesis. This hydrogen gas generating process in the cells offers testimony to the unique photosynthetic metabolism that can be found in many species of green microalgae. Moreover, it has attracted interest by the biotechnology and bioenergy sectors, as it promises utilization of green microalgae and the process of photosynthesis in renewable energy production. This article provides an overview of the principles of photobiological hydrogen production in microalgae and addresses in detail the process of induction and analysis of the hydrogen metabolism in the cells. Furthermore, methods are discussed by which the interaction of photosynthesis, respiration, cellular metabolism, and H(2) production in Chlamydomonas can be monitored and regulated. PMID:19291418

  16. Bioconcentration of tetrachlorobenzene in marine algae

    NASA Astrophysics Data System (ADS)

    Wang, Xiu-Lin; Ma, Yan-Jun; Cheng, Gang; Yu, Wei-Jun; Zhang, Li-Jun

    1997-09-01

    Bioconcentration of tetrachlorobenzene (TeCB) in Chlorella marine, Nannochloropsis oculata, Pyramidomonas sp., Platymonas subcordiformis, and Phaeodactylum tricornutum; and toxicity of TeCB to the marine algae were tested. Values of bioconcentration potential parameters, including uptake rate constant k 1, elimination rate constant k 2 and bioconcentration factor BCF, were obtained not only from the time course of TeCB uptake by the marine algae by using a bioconcentration model, but also from the acute toxicity test data for percent inhibition PI(%)˜exposure concentration of TeCB-time by using a combined bioconcentration and probability model. The results showed good relationship between k 1(TOXIC) and k 1(UPTAKE) and k 2(TOXIC), k 2(UPTAKE), and BCF D(IOXIC) and BCF D(UPTAKE). Especially, the values of BCF D(TOXIC) were well consistent with those of BCF D(UPTAKE).

  17. Nucleotide-metabolizing enzymes in Chlamydomonas flagella.

    PubMed

    Watanabe, T; Flavin, M

    1976-01-10

    Nucleotides have at least two functions in eukaryotic cilia and flagella. ATP, originating in the cells, is utilized for motility by energy-transducing protein(s) called dynein, and the binding of guanine nucleotides to tubulin, and probably certain transformations of the bound nucleotides, are prerequisites for the assembly of microtubules. Besides dynein, which can be solubulized from Chlamydomonas flagella as a heterogeneous, Mg2+ or Ca2+-activated ATPase, we have purified and characterized five other flagellar enzymes involved in nucleotide transformations. A homogeneous, low molecular weight, Ca2+-specific adenosine triphosphatase was isolated, which was inhibited by Mg2+ and was not specific for ATP. This enzyme was not formed by treating purified dynein with proteases. It was absent from extracts of Tetrahymena cilia. Its function might be an auxiliary energy transducer, or in steering or tactic responses. Two species of adenylate kinase were isolated, one of which was much elevated in regenerating flagella; the latter was also present in cell bodies. A large part of flagellar nucleoside diphosphokinase activity could not be solubilized. Two soluble enzyme species were identified, one of which was also present in cell bodies. Since these enzymes are of interest because they might function in microtubule assembly, we studied the extent to which brain nucleoside diphosphokinase co-polymerizes with tubulin purified by repeated cycles of polymerization. Arginine kinase was not detected in Chlamydomonas flagellar extracts. PMID:397

  18. Amidic and acetonic cryoprotectants improve cryopreservation of volvocine green algae.

    PubMed

    Nakazawa, A; Nishii, I

    2012-01-01

    A number of volvocalean green algae species were subjected to a two-step cryopreservation protocol with various cryoprotectants. Potential cryoprotectants were methanol (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methylformamide, and hydroxyacetone (HA). We confirmed prior reports that MeOH was effective for cryopreserving Chlamydomonas, but did not work well for larger volvocaleans such as Volvox. In contrast, DMF and HA were effective for both unicellular and multicellular representatives. When we used a cold-inducible transposon to probe Southern blots of Volvox DNA samples taken before and after storage for one month in LN, we could detect no differences, indicating that the genome had remained relatively stable and that the transposon had not been induced by the cryopreservation procedure. We believe these methods will facilitate long-term storage of several volvocine algal species, including Volvox strains harboring transposon-induced mutations of developmental interest. PMID:22825787

  19. Modeling light-induced currents in the eye of Chlamydomonas reinhardtii.

    PubMed

    Gradmann, D; Ehlenbeck, S; Hegemann, P

    2002-09-15

    Rhodopsin-mediated electrical events in green algae have been recorded in the past from the eyes of numerous micro-algae like Haematococcus pluvialis, Chlamydomonas reinhardtii and Volvox carteri. However, the electrical data gathered by suction-pipette techniques could be interpreted in qualitative terms only. Here we present two models that allow a quantitative analysis of such results: First, an electrical analog circuit for the cell in suction pipette configuration is established. Applying this model to experimental data from unilluminated cells of C. reinhardtii yields a membrane conductance of about 3 Sm(-2). Furthermore, an analog circuit allows the determination of the photocurrent fraction that is recorded under experimental conditions. Second, a reaction scheme of a rhodopsin-type photocycle with an early Ca(2+) conductance and a later H(+) conductance is presented. The combination of both models provides good fits to light-induced currents recorded from C. reinhardtii. Finally, it allowed the calculation of the impact of each model parameter on the time courses of observable photocurrent and of inferred transmembrane voltage. The reduction of the flash-to-peak times at increasing light intensities are explained by superposition of two kinetically distinct rhodopsins and by assuming that the Ca(2+)-conducting state decays faster at more positive membrane voltages. PMID:12235485

  20. Methanol-Promoted Lipid Remodelling during Cooling Sustains Cryopreservation Survival of Chlamydomonas reinhardtii

    PubMed Central

    Yang, Duanpeng; Li, Weiqi

    2016-01-01

    Cryogenic treatments and cryoprotective agents (CPAs) determine the survival rate of organisms that undergo cryopreservation, but their mechanisms of operation have not yet been characterised adequately. In particular, the way in which membrane lipids respond to cryogenic treatments and CPAs is unknown. We developed comparative profiles of the changes in membrane lipids among cryogenic treatments and between the CPAs dimethyl sulfoxide (DMSO) and methanol (MeOH) for the green alga Chlamydomonas reinhardtii. We found that freezing in liquid nitrogen led to a dramatic degradation of lipids, and that thawing at warm temperature (35°C) induced lipid remodelling. DMSO did not protect membranes, but MeOH significantly attenuated lipid degradation. The presence of MeOH during cooling (from 25°C to −55°C at a rate of 1°C/min) sustained the lipid composition to the extent that membrane integrity was maintained; this phenomenon accounts for successful cryopreservation. An increase in monogalactosyldiacylglycerol and a decrease in diacylglycerol were the major changes in lipid composition associated with survival rate, but there was no transformation between these lipid classes. Phospholipase D-mediated phosphatidic acid was not involved in freezing-induced lipid metabolism in C. reinhardtii. Lipid unsaturation changed, and the patterns of change depended on the cryogenic treatment. Our results provide new insights into the cryopreservation of, and the lipid metabolism in, algae. PMID:26731741

  1. The regulation of photosynthetic structure and function during nitrogen deprivation in Chlamydomonas reinhardtii.

    PubMed

    Juergens, Matthew T; Deshpande, Rahul R; Lucker, Ben F; Park, Jeong-Jin; Wang, Hongxia; Gargouri, Mahmoud; Holguin, F Omar; Disbrow, Bradley; Schaub, Tanner; Skepper, Jeremy N; Kramer, David M; Gang, David R; Hicks, Leslie M; Shachar-Hill, Yair

    2015-02-01

    The accumulation of carbon storage compounds by many unicellular algae after nutrient deprivation occurs despite declines in their photosynthetic apparatus. To understand the regulation and roles of photosynthesis during this potentially bioenergetically valuable process, we analyzed photosynthetic structure and function after nitrogen deprivation in the model alga Chlamydomonas reinhardtii. Transcriptomic, proteomic, metabolite, and lipid profiling and microscopic time course data were combined with multiple measures of photosynthetic function. Levels of transcripts and proteins of photosystems I and II and most antenna genes fell with differing trajectories; thylakoid membrane lipid levels decreased, while their proportions remained similar and thylakoid membrane organization appeared to be preserved. Cellular chlorophyll (Chl) content decreased more than 2-fold within 24 h, and we conclude from transcript protein and (13)C labeling rates that Chl synthesis was down-regulated both pre- and posttranslationally and that Chl levels fell because of a rapid cessation in synthesis and dilution by cellular growth rather than because of degradation. Photosynthetically driven oxygen production and the efficiency of photosystem II as well as P700(+) reduction and electrochromic shift kinetics all decreased over the time course, without evidence of substantial energy overflow. The results also indicate that linear electron flow fell approximately 15% more than cyclic flow over the first 24 h. Comparing Calvin-Benson cycle transcript and enzyme levels with changes in photosynthetic (13)CO2 incorporation rates also pointed to a coordinated multilevel down-regulation of photosynthetic fluxes during starch synthesis before the induction of high triacylglycerol accumulation rates. PMID:25489023

  2. The sac mutants of Chlamydomonas reinhardtii reveal transcriptional and posttranscriptional control of cysteine biosynthesis.

    PubMed

    Ravina, Cristina G; Chang, Chwenn-In; Tsakraklides, George P; McDermott, Jeffery P; Vega, Jose M; Leustek, Thomas; Gotor, Cecilia; Davies, John P

    2002-12-01

    Algae and vascular plants are cysteine (Cys) prototrophs. They are able to import, reduce, and assimilate sulfate into Cys, methionine, and other organic sulfur-containing compounds. Characterization of genes encoding the enzymes required for Cys biosynthesis from the unicellular green alga Chlamydomonas reinhardtii reveals that transcriptional and posttranscriptional mechanisms regulate the pathway. The derived amino acid sequences of the C. reinhardtii genes encoding 5'-adenylylsulfate (APS) reductase and serine (Ser) acetyltransferase are orthologous to sequences from vascular plants. The Cys biosynthetic pathway of C. reinhardtii is regulated by sulfate availability. The steady-state level of transcripts and activity of ATP sulfurylase, APS reductase, Ser acetyltransferase, and O-acetyl-Ser (thiol) lyase increase when cells are deprived of sulfate. The sac1 mutation, which impairs C. reinhardtii ability to acclimate to sulfur-deficient conditions, prevents the increase in accumulation of the transcripts encoding these enzymes and also prevents the increase in activity of all the enzymes except APS reductase. The sac2 mutation, which does not affect accumulation of APS reductase transcripts, blocks the increase in APS reductase activity. These results suggest that APS reductase activity is regulated posttranscriptionally in a SAC2-dependent process. PMID:12481091

  3. Rubisco small-subunit α-helices control pyrenoid formation in Chlamydomonas

    PubMed Central

    Meyer, Moritz T.; Genkov, Todor; Skepper, Jeremy N.; Jouhet, Juliette; Mitchell, Madeline C.; Spreitzer, Robert J.; Griffiths, Howard

    2012-01-01

    The pyrenoid is a subcellular microcompartment in which algae sequester the primary carboxylase, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). The pyrenoid is associated with a CO2-concentrating mechanism (CCM), which improves the operating efficiency of carbon assimilation and overcomes diffusive limitations in aquatic photosynthesis. Using the model alga Chlamydomonas reinhardtii, we show that pyrenoid formation, Rubisco aggregation, and CCM activity relate to discrete regions of the Rubisco small subunit (SSU). Specifically, pyrenoid occurrence was shown to be conditioned by the amino acid composition of two surface-exposed α-helices of the SSU: higher plant-like helices knock out the pyrenoid, whereas native algal helices establish a pyrenoid. We have also established that pyrenoid integrity was essential for the operation of an active CCM. With the algal CCM being functionally analogous to the terrestrial C4 pathway in higher plants, such insights may offer a route toward transforming algal and higher plant productivity for the future. PMID:23112177

  4. The Regulation of Photosynthetic Structure and Function during Nitrogen Deprivation in Chlamydomonas reinhardtii1[OPEN

    PubMed Central

    Juergens, Matthew T.; Deshpande, Rahul R.; Lucker, Ben F.; Park, Jeong-Jin; Wang, Hongxia; Gargouri, Mahmoud; Holguin, F. Omar; Disbrow, Bradley; Schaub, Tanner; Skepper, Jeremy N.; Kramer, David M.; Gang, David R.; Hicks, Leslie M.; Shachar-Hill, Yair

    2015-01-01

    The accumulation of carbon storage compounds by many unicellular algae after nutrient deprivation occurs despite declines in their photosynthetic apparatus. To understand the regulation and roles of photosynthesis during this potentially bioenergetically valuable process, we analyzed photosynthetic structure and function after nitrogen deprivation in the model alga Chlamydomonas reinhardtii. Transcriptomic, proteomic, metabolite, and lipid profiling and microscopic time course data were combined with multiple measures of photosynthetic function. Levels of transcripts and proteins of photosystems I and II and most antenna genes fell with differing trajectories; thylakoid membrane lipid levels decreased, while their proportions remained similar and thylakoid membrane organization appeared to be preserved. Cellular chlorophyll (Chl) content decreased more than 2-fold within 24 h, and we conclude from transcript protein and 13C labeling rates that Chl synthesis was down-regulated both pre- and posttranslationally and that Chl levels fell because of a rapid cessation in synthesis and dilution by cellular growth rather than because of degradation. Photosynthetically driven oxygen production and the efficiency of photosystem II as well as P700+ reduction and electrochromic shift kinetics all decreased over the time course, without evidence of substantial energy overflow. The results also indicate that linear electron flow fell approximately 15% more than cyclic flow over the first 24 h. Comparing Calvin-Benson cycle transcript and enzyme levels with changes in photosynthetic 13CO2 incorporation rates also pointed to a coordinated multilevel down-regulation of photosynthetic fluxes during starch synthesis before the induction of high triacylglycerol accumulation rates. PMID:25489023

  5. Metabolic control of urea catabolism in Chlamydomonas reinhardi and Chlorella pyrenoidosa.

    PubMed

    Hodson, R C; Williams, S K; Davidson, W R

    1975-03-01

    In the unicellular green alga Chlamydomonas reinhardi (strain y-1), synthesis of the enzymes required for urea hydrolysis is under substrate induction control by urea and under end product repression control by ammonia. Hydrolysis of urea if effected by the sequential action of the discrete enzymes urea carboxylase and allophanate lyase, collectively called urea amidolyase. The carboxylase converts urea to allophanate in a reaction requiring biotin, adenosine 5'-triphosphate, and Mg2+. The lyase hydrolzyes allophanate to ammonium ions and bicarbonate. Neither activity is present in more than trace amounts when cultures are grown with ammonia or urea plus ammonia, or when they are starved for nitrogen for 8 h. Urea in the absence of ammonia induces both activities 10 to 100 times the basal levels. Addition of ammonia to an induced culture causes complete cessation of carboxylase accumulation and an 80% depression of lyase accumulation. Ammonia does not reduce urea uptake by repressed cells, so it does not prevent induction by the mechanism of inducer exclusion. The unicellular green alga Chlorella pyrenoidosa (strain 3 Emerson) also has discrete carboxylase and lyase enzymes, but only the carboxylase exhibits metabolic control. PMID:1116994

  6. Toxicological effects of nanometer titanium dioxide (nano-TiO2) on Chlamydomonas reinhardtii.

    PubMed

    Chen, Lanzhou; Zhou, Lina; Liu, Yongding; Deng, Songqiang; Wu, Hao; Wang, Gaohong

    2012-10-01

    The toxicological effects of nanometer titanium dioxide (nano-TiO2) on a unicellular green alga Chlamydomonas reinhardtii were assessed by investigating the changes of the physiology and cyto-ultrastructure of this species under treatment. We found that nano-TiO2 inhibited photosynthetic efficiency and cell growth, but the content of chlorophyll a content in algae did not change, while carotenoid and chlorophyll b contents increased. Malondialdehyde (MDA) content reached maximum values after 8h exposure and then decreased to a moderately low level at 72 h. Electron microscopy images indicated that as concentrations of nano-TiO2 increased, a large number of C. reinhardtii cells were noted to be damaged: the number of chloroplasts declined, various other organelles were degraded, plasmolysis occurred, and TiO2 nanoparticles were found to be located inside cell wall and membrane. It was also noted that cell surface was surrounded by TiO2 particles, which could present an obstacle to the exchange of substances between the cell and its surrounding environment. To sum up, the effect of nano-TiO2 on C. reinhardtii included cell surface aggregation, photosynthesis inhibition, lipid peroxidation and new protein synthesis, while the response of C. reinhardtii to nano-TiO2 was a rapid process which occurs during 24 h after exposing and may relate to physiological stress system to mitigate damage. PMID:22883605

  7. Methanol-Promoted Lipid Remodelling during Cooling Sustains Cryopreservation Survival of Chlamydomonas reinhardtii.

    PubMed

    Yang, Duanpeng; Li, Weiqi

    2016-01-01

    Cryogenic treatments and cryoprotective agents (CPAs) determine the survival rate of organisms that undergo cryopreservation, but their mechanisms of operation have not yet been characterised adequately. In particular, the way in which membrane lipids respond to cryogenic treatments and CPAs is unknown. We developed comparative profiles of the changes in membrane lipids among cryogenic treatments and between the CPAs dimethyl sulfoxide (DMSO) and methanol (MeOH) for the green alga Chlamydomonas reinhardtii. We found that freezing in liquid nitrogen led to a dramatic degradation of lipids, and that thawing at warm temperature (35°C) induced lipid remodelling. DMSO did not protect membranes, but MeOH significantly attenuated lipid degradation. The presence of MeOH during cooling (from 25°C to -55°C at a rate of 1°C/min) sustained the lipid composition to the extent that membrane integrity was maintained; this phenomenon accounts for successful cryopreservation. An increase in monogalactosyldiacylglycerol and a decrease in diacylglycerol were the major changes in lipid composition associated with survival rate, but there was no transformation between these lipid classes. Phospholipase D-mediated phosphatidic acid was not involved in freezing-induced lipid metabolism in C. reinhardtii. Lipid unsaturation changed, and the patterns of change depended on the cryogenic treatment. Our results provide new insights into the cryopreservation of, and the lipid metabolism in, algae. PMID:26731741

  8. Multiple regulatory mechanisms in the chloroplast of green algae: relation to hydrogen production.

    PubMed

    Antal, Taras K; Krendeleva, Tatyana E; Tyystjärvi, Esa

    2015-09-01

    A complex regulatory network in the chloroplast of green algae provides an efficient tool for maintenance of energy and redox balance in the cell under aerobic and anaerobic conditions. In this review, we discuss the structural and functional organizations of electron transport pathways in the chloroplast, and regulation of photosynthesis in the green microalga Chlamydomonas reinhardtii. The focus is on the regulatory mechanisms induced in response to nutrient deficiency stress and anoxia and especially on the role of a hydrogenase-mediated reaction in adaptation to highly reducing conditions and ATP deficiency in the cell. PMID:25986411

  9. International Conference on the Cell and Molecular Biology of Chlamydomonas

    SciTech Connect

    Dr. Stephen Miller

    2010-06-10

    The 2010 Conference on the Cell and Molecular Biology of Chlamydomonas was held June 6-10 near Boston, MA, and attracted a record 273 participants, 146 from US labs, 10 from Canada, and the remainder from 18 other countries. The single-celled algal protist Chlamydomonas is a key research organism for many investigators, including those who study photosynthesis, cell motility, adaptation to environmental stresses, the evolution of multicellularity, and the production of biofuels. Chlamydomonas researchers gather every two years at a research conference to exchange methods, develop collaborative efforts, disseminate recent findings, and plan large-scale studies to improve the usefulness of this unique research organism. This conference provides the only opportunity for Chlamydomonas scientists who work on different research problems to meet face to face, and greatly speeds progress in their respective fields. An important function of these Chlamydomonas conferences is to promote and showcase the work of younger scientists, and to attract new investigators into the Chlamydomonas community. DOE award SC0004085 was used to offset the travel and registration costs for 18 young investigators, 9 of whom were women, including one African American. Most of these scientists would not have been able to attend the conference without DOE support. A total of 208 research presentations were made at the meeting, 80 talks (63 presented by students, postdocs, and pre-tenured faculty) and 128 posters. Cell motility and biofuels/metabolism were the best-represented research areas, with a total of 77 presentations. This fact underscores the growing importance of Chlamydomonas as a research and production tool in the rapidly expanding world of biofuels research. A total of 28 talks and posters were presented on the topics of photosynthesis and stress responses, which were among the next best-represented research areas. As at several recent Chlamydomonas meetings, important advances were

  10. Plasmodesmata of brown algae.

    PubMed

    Terauchi, Makoto; Nagasato, Chikako; Motomura, Taizo

    2015-01-01

    Plasmodesmata (PD) are intercellular connections in plants which play roles in various developmental processes. They are also found in brown algae, a group of eukaryotes possessing complex multicellularity, as well as green plants. Recently, we conducted an ultrastructural study of PD in several species of brown algae. PD in brown algae are commonly straight plasma membrane-lined channels with a diameter of 10-20 nm and they lack desmotubule in contrast to green plants. Moreover, branched PD could not be observed in brown algae. In the brown alga, Dictyota dichotoma, PD are produced during cytokinesis through the formation of their precursor structures (pre-plasmodesmata, PPD). Clustering of PD in a structure termed "pit field" was recognized in several species having a complex multicellular thallus structure but not in those having uniseriate filamentous or multiseriate one. The pit fields might control cell-to-cell communication and contribute to the establishment of the complex multicellular thallus. In this review, we discuss fundamental morphological aspects of brown algal PD and present questions that remain open. PMID:25516500

  11. Ca2+-regulated cyclic electron flow supplies ATP for nitrogen starvation-induced lipid biosynthesis in green alga

    PubMed Central

    Chen, Hui; Hu, Jinlu; Qiao, Yaqin; Chen, Weixian; Rong, Junfeng; Zhang, Yunming; He, Chenliu; Wang, Qiang

    2015-01-01

    We previously showed that both the linear photosynthetic electron transportation rate and the respiration rate dropped significantly during N starvation-induced neutral lipid accumulation in an oil-producing microalga, Chlorella sorokiniana, and proposed a possible role for cyclic electron flow (CEF) in ATP supply. In this study, we further exploited this hypothesis in both Chlorella sorokiniana C3 and the model green alga Chlamydomonas. We found that both the rate of CEF around photosystem I and the activity of thylakoid membrane-located ATP synthetase increased significantly during N starvation to drive ATP production. Furthermore, we demonstrated that the Chlamydomonas mutant pgrl1, which is deficient in PGRL1-mediated CEF, accumulated less neutral lipids and had reduced rates of CEF under N starvation. Further analysis revealed that Ca2+ signaling regulates N starvation-induced neutral lipid biosynthesis in Chlamydomonas by increasing calmodulin activity and boosting the expression of the calcium sensor protein that regulates Pgrl1-mediated CEF. Thus, Ca2+-regulated CEF supplies ATP for N starvation-induced lipid biosynthesis in green alga. The increased CEF may re-equilibrate the ATP/NADPH balance and recycle excess light energy in photosystems to prevent photooxidative damage, suggesting Ca2+-regulated CEF also played a key role in protecting and sustaining photosystems. PMID:26450399

  12. Ca(2+)-regulated cyclic electron flow supplies ATP for nitrogen starvation-induced lipid biosynthesis in green alga.

    PubMed

    Chen, Hui; Hu, Jinlu; Qiao, Yaqin; Chen, Weixian; Rong, Junfeng; Zhang, Yunming; He, Chenliu; Wang, Qiang

    2015-01-01

    We previously showed that both the linear photosynthetic electron transportation rate and the respiration rate dropped significantly during N starvation-induced neutral lipid accumulation in an oil-producing microalga, Chlorella sorokiniana, and proposed a possible role for cyclic electron flow (CEF) in ATP supply. In this study, we further exploited this hypothesis in both Chlorella sorokiniana C3 and the model green alga Chlamydomonas. We found that both the rate of CEF around photosystem I and the activity of thylakoid membrane-located ATP synthetase increased significantly during N starvation to drive ATP production. Furthermore, we demonstrated that the Chlamydomonas mutant pgrl1, which is deficient in PGRL1-mediated CEF, accumulated less neutral lipids and had reduced rates of CEF under N starvation. Further analysis revealed that Ca(2+) signaling regulates N starvation-induced neutral lipid biosynthesis in Chlamydomonas by increasing calmodulin activity and boosting the expression of the calcium sensor protein that regulates Pgrl1-mediated CEF. Thus, Ca(2+)-regulated CEF supplies ATP for N starvation-induced lipid biosynthesis in green alga. The increased CEF may re-equilibrate the ATP/NADPH balance and recycle excess light energy in photosystems to prevent photooxidative damage, suggesting Ca(2+)-regulated CEF also played a key role in protecting and sustaining photosystems. PMID:26450399

  13. Zinc Deficiency Impacts CO2 Assimilation and Disrupts Copper Homeostasis in Chlamydomonas reinhardtii*

    PubMed Central

    Malasarn, Davin; Kropat, Janette; Hsieh, Scott I.; Finazzi, Giovanni; Casero, David; Loo, Joseph A.; Pellegrini, Matteo; Wollman, Francis-André; Merchant, Sabeeha S.

    2013-01-01

    Zinc is an essential nutrient because of its role in catalysis and in protein stabilization, but excess zinc is deleterious. We distinguished four nutritional zinc states in the alga Chlamydomonas reinhardtii: toxic, replete, deficient, and limited. Growth is inhibited in zinc-limited and zinc-toxic cells relative to zinc-replete cells, whereas zinc deficiency is visually asymptomatic but distinguished by the accumulation of transcripts encoding ZIP family transporters. To identify targets of zinc deficiency and mechanisms of zinc acclimation, we used RNA-seq to probe zinc nutrition-responsive changes in gene expression. We identified genes encoding zinc-handling components, including ZIP family transporters and candidate chaperones. Additionally, we noted an impact on two other regulatory pathways, the carbon-concentrating mechanism (CCM) and the nutritional copper regulon. Targets of transcription factor Ccm1 and various CAH genes are up-regulated in zinc deficiency, probably due to reduced carbonic anhydrase activity, validated by quantitative proteomics and immunoblot analysis of Cah1, Cah3, and Cah4. Chlamydomonas is therefore not able to grow photoautotrophically in zinc-limiting conditions, but supplementation with 1% CO2 restores growth to wild-type rates, suggesting that the inability to maintain CCM is a major consequence of zinc limitation. The Crr1 regulon responds to copper limitation and is turned on in zinc deficiency, and Crr1 is required for growth in zinc-limiting conditions. Zinc-deficient cells are functionally copper-deficient, although they hyperaccumulate copper up to 50-fold over normal levels. We suggest that zinc-deficient cells sequester copper in a biounavailable form, perhaps to prevent mismetallation of critical zinc sites. PMID:23439652

  14. Potassium Fluxes in Chlamydomonas reinhardtii (I.Kinetics and Electrical Potentials).

    PubMed Central

    Malhotra, B.; Glass, ADM.

    1995-01-01

    Potassium influx and cellular [K+] were measured in the unicellular green alga Chlamydomonas reinhardtii after pretreatment in either 10 or 0 mM external K+ ([K]0). K+ (42K+ or 86Rb+) influx was mediated by a saturable, high-affinity transport system (HATS) at low [K+]0 and a linear, low-affinity transport system at high [K+]o. The HATS was typically more sensitive to metabolic inhibition (and darkness) than the low-affinity transport system. Membrane electrical potentials were determined by measuring the equilibrium distribution of tetraphenylphosphonium. These values, together with estimates of cytoplasmic [K+] (B. Malhotra and A.D.M. Glass [1995] Plant Physiol 108: 1537-1545), demonstrated that at 0.1 mM [K+]0 K+ uptake must be active. At higher [K+]0 (>0.3 mM) K+ influx appeared to be passive and possibly channel mediated. When cells were deprived of K+ for 24 h, the Vmax for the HATS increased from 50 x 10-6 to 85 x 10-6 nmol h-1 cell-1 and the Km value decreased from 0.25 to 0.162 mM. Meanwhile, cellular [K+] declined from 24 x 10-6 to 9 x 10-6 nmol cell-1. During this period influx increased exponentially, reaching its peak value after 18 h of K+ deprivation. This increase of K+ influx was not expressed when cells were exposed to inhibitors of protein synthesis. The use of 42K+ and 86Rb+ in parallel experiments demonstrated that Chlamydomonas discriminated in favor of K+ over Rb+, and this effect increased with the duration of K+ deprivation. PMID:12228559

  15. A revised mineral nutrient supplement increases biomass and growth rate in Chlamydomonas reinhardtii.

    PubMed

    Kropat, Janette; Hong-Hermesdorf, Anne; Casero, David; Ent, Petr; Castruita, Madeli; Pellegrini, Matteo; Merchant, Sabeeha S; Malasarn, Davin

    2011-06-01

    Interest in exploiting algae as a biofuel source and the role of inorganic nutrient deficiency in inducing triacylglyceride (TAG) accumulation in cells necessitates a strategy to efficiently formulate species-specific culture media that can easily be manipulated. Using the reference organism Chlamydomonas reinhardtii, we tested the hypothesis that modeling trace element supplements after the cellular ionome would result in optimized cell growth. We determined the trace metal content of several commonly used Chlamydomonas strains in various culture conditions and developed a revised trace element solution to parallel these measurements. Comparison of cells growing in the revised supplement versus a traditional trace element solution revealed faster growth rates and higher maximum cell densities with the revised recipe. RNA-seq analysis of cultures growing in the traditional versus revised medium suggest that the variation in transcriptomes was smaller than that found between different wild-type strains grown in traditional Hutner's supplement. Visual observation did not reveal defects in cell motility or mating efficiency in the new supplement. Ni²⁺-inducible expression from the CYC6 promoter remained a useful tool, albeit with an increased requirement for Ni²⁺ because of the introduction of an EDTA buffer system in the revised medium. Other advantages include more facile preparation of trace element stock solutions, a reduction in total chemical use, a more consistent batch-to-batch formulation and long-term stability (tested up to 5 years). Under the new growth regime, we analyzed cells growing under different macro- and micronutrient deficiencies. TAG accumulation in N deficiency is comparable in the new medium. Fe and Zn deficiency also induced TAG accumulation, as suggested by Nile Red staining. This approach can be used to efficiently optimize culture conditions for other algal species to improve growth and to assay cell physiology. PMID:21309872

  16. How Chlamydomonas keeps track of the light once it has reached the right phototactic orientation.

    PubMed Central

    Schaller, K; David, R; Uhl, R

    1997-01-01

    By using a real-time assay that allows measurement of the phototactic orientation of the unicellular alga Chlamydomonas with millisecond time resolution, it can be shown that single photons not only induce transient direction changes but that fluence rates as low as 1 photon cell(-1) s(-1) can already lead to a persistent orientation. Orientation is a binary variable, i.e., in a partially oriented population some organisms are fully oriented while the rest are still at random. Action spectra reveal that the response to a pulsed stimulus follows the Dartnall-nomogram for a rhodopsin while the response to a persistent stimulus falls off more rapidly toward the red end of the spectrum. Thus light of 540 nm, for which chlamy-rhodopsin is equally sensitive as for 440-nm light, induces no measurable persistent orientation while 440-nm light does. A model is presented which explains not only this behavior, but also how Chlamydomonas can track the light direction and switches between a positive and negative phototaxis. According to the model the ability to detect the direction of light, to make the right turn and to stay oriented, is a direct consequence of the helical path of the organism, the orientation of its eyespot relative to the helix-axis, and the special shielding properties of eyespot and cell body. The model places particular emphasis on the fact that prolonged swimming into the correct direction not only requires making a correct turn initially, but also avoiding further turns once the right direction has been reached. Images FIGURE 1 FIGURE 4 FIGURE 6 FIGURE 7 FIGURE 8 PMID:9284323

  17. The Antarctic psychrophile, Chlamydomonas subcaudata, is deficient in state I-state II transitions.

    PubMed

    Morgan-Kiss, Rachael M; Ivanov, Alexander G; Huner, Norman P A

    2002-01-01

    State I-State II transitions were monitored in vivo and in vitro in the Antarctic, psychrophillic, green alga, Chlamydomonas subcaudata, as changes in the low-temperature (77 K) chlorophyll fluorescence emission maxima at 722 nm (F722) relative to 699 nm (F699). As expected, the control mesophillic species, Chlamydomonas reinhardtii, was able to modulate the light energy distribution between photosystem II and photosystem I in response to exposure to four different conditions: (i) dark/anaerobic conditions, (ii) a change in Mg2+ concentration, (iii) red light, and (iv) increased incubation temperature. This was correlated with the ability to phosphorylate both of its major light-harvesting polypeptides. In contrast, exposure of C. subcaudata to the same four conditions induced minimum alterations in the 77 K fluorescence emission spectra, which was correlated with the ability to phosphorylate only one of its major light-harvesting polypeptides. Thus, C. subcaudata appears to be deficient in the ability to undergo a State I-State II transition. Functionally, this is associated with alterations in the apparent redox status of the intersystem electron transport chain and with higher rates of photosystem I cyclic electron transport in the psychrophile than in the mesophile, based on in vivo P700 measurements. Structurally, this deficiency is associated with reduced levels of Psa A/B relative to D1, the absence of specific photosystem I light-harvesting polypeptides [R.M. Morgan et al. (1998) Photosynth Res 56:303-314] and a cytochrome b6/f complex that exhibits a form of cytochrome f that is approximately 7 kDa smaller than that observed in C. reinhardtii. We conclude that the Antarctic psychrophile, C. subcaudata, is an example of a natural variant deficient in State I-State II transitions. PMID:11859846

  18. Ferric reduction by iron-limited Chlamydomonas cells interacts with both photosynthesis and respiration.

    PubMed

    Weger, H G; Espie, G S

    2000-04-01

    Iron limitation led to a large increase in extracellular ferricyanide (Fe[III]) reductase activity in cells of the green alga Chlamydomonas reinhardtii Dangeard. Mass-spectrometric measurement of gas exchange indicated that ferricyanide reduction in the dark resulted in a stimulation of respiratory CO2 production without affecting the rate of respiratory O2 consumption, consistent with the previously postulated activation of the oxidative pentose phosphate pathway in support of Fe(III) reduction by iron-limited Chlamydomonas cells (X. Xue et al., 1998, J. Phycol. 34: 939-944). At saturating irradiance, the rate of ferricyanide reduction was stimulated almost 3-fold, and this stimulation was inhibited by 3-(3',4'-dichlorophenyl)-1,1-dimethylurea. Ferricyanide reduction during photosynthesis resulted in approximately a 50% inhibition of photosynthetic CO2 fixation at saturating irradiance, and almost 100% inhibition of CO2 fixation at sub-saturating irradiance. Photosynthesis by iron-sufficient cells was not affected by ferricyanide addition. Addition of 250 microM ferricyanide to iron-limited cells in which photosynthesis was inhibited (either by the presence of glycolaldehyde, or by maintaining the cells at the CO2 compensation point) resulted in a stimulation in the rate of gross photosynthetic O2 evolution. Chlorophyll a fluorescence measurements indicated a large increase in non-photochemical quenching during ferricyanide reduction in the light; the increase in nonphotochemical quenching was abolished by the addition of nigericin. These results suggest that reduction of extracellular ferricyanide (mediated at the plasma membrane) interacts with both photosynthesis and respiration, and that both of these processes contribute NADPH in the light. PMID:10805449

  19. Functional specialization of Chlamydomonas reinhardtii cytosolic thioredoxin h1 in the response to alkylation-induced DNA damage.

    PubMed

    Sarkar, Nandita; Lemaire, Stéphane; Wu-Scharf, Danxia; Issakidis-Bourguet, Emmanuelle; Cerutti, Heriberto

    2005-02-01

    DNA damage occurs as a by-product of intrinsic cellular processes, like DNA replication, or as a consequence of exposure to genotoxic agents. Organisms have evolved multiple mechanisms to avoid, tolerate, or repair DNA lesions. To gain insight into these processes, we have isolated mutants hypersensitive to DNA-damaging agents in the green alga Chlamydomonas reinhardtii. One mutant, Ble-1, showed decreased survival when it was treated with methyl methanesulfonate (MMS), bleomycin, or hydrogen peroxide (H2O2) but behaved like the wild type when it was exposed to UVC irradiation. Ble-1 carries an extensive chromosomal deletion that includes the gene encoding cytosolic thioredoxin h1 (Trxh1). Transformation of Ble-1 with a wild-type copy of Trxh1 fully corrected the MMS hypersensitivity and partly restored the tolerance to bleomycin. Trxh1 also complemented a defect in the repair of MMS-induced DNA strand breaks and alkali-labile sites. In addition, a Trxh1-beta-glucuronidase fusion protein translocated to the nucleus in response to treatment with MMS. However, somewhat surprisingly, Trxh1 failed to correct the Ble-1 hypersensitivity to H2O2. Moreover, Trxh1 suppression by RNA interference in a wild-type strain resulted in enhanced sensitivity to MMS and DNA repair defects but no increased cytotoxicity to H2O2. Thioredoxins have been implicated in oxidative-stress responses in many organisms. Yet our results indicate a specific role of Chlamydomonas Trxh1 in the repair of MMS-induced DNA damage, whereas it is dispensable for the response to H2O2. These observations also suggest functional specialization among cytosolic thioredoxins since another Chlamydomonas isoform (Trxh2) does not compensate for the lack of Trxh1. PMID:15701788

  20. Getting to the heart of intraflagellar transport using Trypanosoma and Chlamydomonas models: the strength is in their differences

    PubMed Central

    2013-01-01

    Cilia and flagella perform diverse roles in motility and sensory perception, and defects in their construction or their function are responsible for human genetic diseases termed ciliopathies. Cilia and flagella construction relies on intraflagellar transport (IFT), the bi-directional movement of ‘trains’ composed of protein complexes found between axoneme microtubules and the flagellum membrane. Although extensive information about IFT components and their mode of action were discovered in the green algae Chlamydomonas reinhardtii, other model organisms have revealed further insights about IFT. This is the case of Trypanosoma brucei, a flagellated protist responsible for sleeping sickness that is turning out to be an emerging model for studying IFT. In this article, we review different aspects of IFT, based on studies of Chlamydomonas and Trypanosoma. Data available from both models are examined to ask challenging questions about IFT such as the initiation of flagellum construction, the setting-up of IFT and the mode of formation of IFT trains, and their remodeling at the tip as well as their recycling at the base. Another outstanding question is the individual role played by the multiple IFT proteins. The use of different models, bringing their specific biological and experimental advantages, will be invaluable in order to obtain a global understanding of IFT. PMID:24289478

  1. The ubiquitin–proteasome pathway protects Chlamydomonas reinhardtii against selenite toxicity, but is impaired as reactive oxygen species accumulate

    PubMed Central

    Vallentine, Patrick; Hung, Chiu-Yueh; Xie, Jiahua; Van Hoewyk, Doug

    2014-01-01

    The ubiquitin–proteasome pathway (UPP) coordinates a myriad of physiological processes in higher plants, including abiotic stress responses, but it is less well characterized in algal species. In this study, the green alga Chlamydomonas reinhardtii was used to gain insights into the role of the UPP during moderate and severe selenite stress at three different time points. The data indicate that activity of the UPP in response to selenium (Se) stress was both time and dose dependent. Moderate selenite stress increased proteasome activity, protein ubiquitination and the proteasomal removal of malformed selenoproteins. However, severe Se stress caused by prolonged selenite treatment or high selenite concentration decreased proteasome activity, inhibited protein ubiquitination and prevented the proteasomal removal of selenoproteins. The UPP impairment during severe Se stress was associated with the observed accumulation of reactive oxygen species (ROS), including mitochondrial superoxide. Additionally, proteasomal inhibition decreased the concentration of chlorophyll in cultures challenged with Se. Therefore, although the UPP protects Chlamydomonas against Se stress, severe oxidative stress induced by selenite toxicity likely hinders the UPP's capacity to mediate a stress response. The possibility that stress tolerance in plants is dependent upon optimal UPP activity and maintenance is discussed. PMID:25301821

  2. Efficient Heterologous Transformation of Chlamydomonas reinhardtii npq2 Mutant with the Zeaxanthin Epoxidase Gene Isolated and Characterized from Chlorella zofingiensis

    PubMed Central

    Couso, Inmaculada; Cordero, Baldo F.; Vargas, María Ángeles; Rodríguez, Herminia

    2012-01-01

    In the violaxanthin cycle, the violaxanthin de-epoxidase and zeaxanthin epoxidase catalyze the inter-conversion between violaxanthin and zeaxanthin in both plants and green algae. The zeaxanthin epoxidase gene from the green microalga Chlorella zofingiensis (Czzep) has been isolated. This gene encodes a polypeptide of 596 amino acids. A single copy of Czzep has been found in the C. zofingiensis genome by Southern blot analysis. qPCR analysis has shown that transcript levels of Czzep were increased after zeaxanthin formation under high light conditions. The functionality of Czzep gene by heterologous genetic complementation in the Chlamydomonas mutant npq2, which lacks zeaxanthin epoxidase (ZEP) activity and accumulates zeaxanthin in all conditions, was analyzed. The Czzep gene was adequately inserted in the pSI105 vector and expressed in npq2. The positive transformants were able to efficiently convert zeaxanthin into violaxanthin, as well as to restore their maximum quantum efficiency of the PSII (Fv/Fm). These results show that Chlamydomonas can be an efficient tool for heterologous expression and metabolic engineering for biotechnological applications. PMID:23118714

  3. An Indexed, Mapped Mutant Library Enables Reverse Genetics Studies of Biological Processes in Chlamydomonas reinhardtii[OPEN

    PubMed Central

    Gang, Spencer S.; Blum, Sean R.; Ivanova, Nina; Yue, Rebecca; Grossman, Arthur R.

    2016-01-01

    The green alga Chlamydomonas reinhardtii is a leading unicellular model for dissecting biological processes in photosynthetic eukaryotes. However, its usefulness has been limited by difficulties in obtaining mutants in specific genes of interest. To allow generation of large numbers of mapped mutants, we developed high-throughput methods that (1) enable easy maintenance of tens of thousands of Chlamydomonas strains by propagation on agar media and by cryogenic storage, (2) identify mutagenic insertion sites and physical coordinates in these collections, and (3) validate the insertion sites in pools of mutants by obtaining >500 bp of flanking genomic sequences. We used these approaches to construct a stably maintained library of 1935 mapped mutants, representing disruptions in 1562 genes. We further characterized randomly selected mutants and found that 33 out of 44 insertion sites (75%) could be confirmed by PCR, and 17 out of 23 mutants (74%) contained a single insertion. To demonstrate the power of this library for elucidating biological processes, we analyzed the lipid content of mutants disrupted in genes encoding proteins of the algal lipid droplet proteome. This study revealed a central role of the long-chain acyl-CoA synthetase LCS2 in the production of triacylglycerol from de novo-synthesized fatty acids. PMID:26764374

  4. SOME FACTORS IN THE COMPETITION OR ANTAGONISM AMONG BACTERIA, ALGAE, AND AQUATIC WEEDS.

    PubMed

    Filzgerald, G P

    1969-12-01

    Field observations of changes in the populations of aquatic weeds and phytoplankton have confirmed that aquatic weeds have antagonistic activity toward phytoplankton. Nutritional studies in the laboratory indicate that cultures of the aquatic weeds, Myriophyllum sp., Ceratophyllum sp., and duckweed (Lemma minor L.); liquid cultures of barley (Hordeum vulgare L., Dickson variety); and cultures of the filamentous green algae, Cladophora sp. and Pithophora oedogonium (Mont.) Withrock, will remain relatively free of epiphytes or competing phytoplankton if the cultures are nitrogen-limited. Field observations of Cladophora sp. have confirmed that the growth of epiphytes on the Cladophora is related to conditions of surplus available nitrogen compounds. It is proposed that this antagonistic activity may be due to a "nitrogen sink" effect in which the aquatic weeds or filamentous green algae prevent the growth of contaminating algae by competition for the limited nitrogen compounds available. However, the presence of bacteria-sized organisms which have selective toxicity to certain algae indicates that perhaps multiple factors exist. Discussed are the ecological implications of associations of certain algae with bacteria that have selective toxicities for other species of algae under certain environmental conditions such as nitrogen-limited growth. PMID:27096454

  5. Factors affecting the mating competence in the unicellular green alga Chlamydomonas eugametos (Volvocales).

    PubMed

    Zachleder, V; Hendrychová, J; Bisová, K; Kubín, S

    2002-01-01

    Routinely prepared gametes (by flooding 3 week-old agar cultures) showed about 80% mating competence if the opposite sexual partners were mixed together. The mating competence exhibited a strict dependence on the composition of the solution in which the cells were suspended before mixing; it decreased progressively with increasing concentration of nitrates. In contrast, no inhibiting effect was found if urea was used as the source of nitrogen. Other ions present in nutrient media did not show any effect. Mating activity varied according to the spectral composition of light, being higher with a blue light than with a red one. Blue light caused accumulation of vis-à-vis pairs, which were blocked to form zygotes. Freshly released daughter cells in vegetatively grown synchronous cultures had a dual nature--vegetative and sexual one. In these daughter cells, similar rules were found for governing of mating competence to those valid for standard gametes obtained from flooded agar cultures. High mating competence was found in daughter cells released the during dark period in distilled water, nitrate-free media, in the presence of Mg2+ or Ca2+ ions, or in media containing urea. The conditions during which daughter cells are released and the conditions under which they mate can be considered crucial for expression of gametic nature as a mating competence. PMID:11980273

  6. Site-specific mutagenesis of the D1 subunit of photosystem II in wild-type Chlamydomonas.

    PubMed Central

    Przibilla, E; Heiss, S; Johanningmeier, U; Trebst, A

    1991-01-01

    The structure and functional mode of photosystem II reaction center protein D1 can be studied by analyzing the effects of amino acid substitutions within the binding niche for QB, the second stable electron acceptor of photosystem II, on herbicide binding. Here we report on site-directed mutagenesis of the psbA gene coding for the D1 protein in the unicellular alga Chlamydomonas reinhardtii. The chloroplasts of wild-type cells were transformed using the particle gun. The plasmids introduced carried an in vitro mutated fragment of the psbA gene. We obtained a double mutant with replacements of amino acids 264 and 266 and a triple mutant having an additional substitution in position 259. The sensitivities of both mutants toward several types of herbicides are given and compared with those of a mutant having only a substitution at position 264. PMID:1840907

  7. A sex recognition glycoprotein is encoded by the plus mating-type gene fus1 of Chlamydomonas reinhardtii.

    PubMed Central

    Ferris, P J; Woessner, J P; Goodenough, U W

    1996-01-01

    Sexual fusion between plus and minus gametes of the unicellular green alga Chlamydomonas reinhardtii entails adhesion between plus-specific and minus-specific "fringe" proteins displayed on the plasma membrane of gametic mating structures. We report the identification of the gene (fus1) encoding the plus fringe glycoprotein, which resides in a unique domain of the mating-type plus (mt+) locus, and which was identified by transposon insertions in three fusion-defective mutant strains. Transformation with fus1+ restores fringe and fusion competence to these mutants and to the pseudo-plus mutant imp11 mt-, defective in minus differentiation. The fus1 gene is remarkable in lacking the codon bias found in all other nuclear genes of C. reinhardtii. Images PMID:8856667

  8. Environmental Feedbacks and Engineered Nanoparticles: Mitigation of Silver Nanoparticle Toxicity to Chlamydomonas reinhardtii by Algal-Produced Organic Compounds

    PubMed Central

    Stevenson, Louise M.; Dickson, Helen; Klanjscek, Tin; Keller, Arturo A.; McCauley, Edward; Nisbet, Roger M.

    2013-01-01

    The vast majority of nanotoxicity studies measures the effect of exposure to a toxicant on an organism and ignores the potentially important effects of the organism on the toxicant. We investigated the effect of citrate-coated silver nanoparticles (AgNPs) on populations of the freshwater alga Chlamydomonas reinhardtii at different phases of batch culture growth and show that the AgNPs are most toxic to cultures in the early phases of growth. We offer strong evidence that reduced toxicity occurs because extracellular dissolved organic carbon (DOC) compounds produced by the algal cells themselves mitigate the toxicity of AgNPs. We analyzed this feedback with a dynamic model incorporating algal growth, nanoparticle dissolution, bioaccumulation of silver, DOC production and DOC-mediated inactivation of nanoparticles and ionic silver. Our findings demonstrate how the feedback between aquatic organisms and their environment may impact the toxicity and ecological effects of engineered nanoparticles. PMID:24086348

  9. Repression of Essential Chloroplast Genes Reveals New Signaling Pathways and Regulatory Feedback Loops in Chlamydomonas[W

    PubMed Central

    Ramundo, Silvia; Rahire, Michèle; Schaad, Olivier; Rochaix, Jean-David

    2013-01-01

    Although reverse genetics has been used to elucidate the function of numerous chloroplast proteins, the characterization of essential plastid genes and their role in chloroplast biogenesis and cell survival has not yet been achieved. Therefore, we developed a robust repressible chloroplast gene expression system in the unicellular alga Chlamydomonas reinhardtii based mainly on a vitamin-repressible riboswitch, and we used this system to study the role of two essential chloroplast genes: ribosomal protein S12 (rps12), encoding a plastid ribosomal protein, and rpoA, encoding the α-subunit of chloroplast bacterial-like RNA polymerase. Repression of either of these two genes leads to the arrest of cell growth, and it induces a response that involves changes in expression of nuclear genes implicated in chloroplast biogenesis, protein turnover, and stress. This response also leads to the overaccumulation of several plastid transcripts and reveals the existence of multiple negative regulatory feedback loops in the chloroplast gene circuitry. PMID:23292734

  10. Solar-driven hydrogen production in green algae.

    PubMed

    Burgess, Steven J; Tamburic, Bojan; Zemichael, Fessehaye; Hellgardt, Klaus; Nixon, Peter J

    2011-01-01

    The twin problems of energy security and global warming make hydrogen an attractive alternative to traditional fossil fuels with its combustion resulting only in the release of water vapor. Biological hydrogen production represents a renewable source of the gas and can be performed by a diverse range of microorganisms from strict anaerobic bacteria to eukaryotic green algae. Compared to conventional methods for generating H(2), biological systems can operate at ambient temperatures and pressures without the need for rare metals and could potentially be coupled to a variety of biotechnological processes ranging from desalination and waste water treatment to pharmaceutical production. Photobiological hydrogen production by microalgae is particularly attractive as the main inputs for the process (water and solar energy) are plentiful. This chapter focuses on recent developments in solar-driven H(2) production in green algae with emphasis on the model organism Chlamydomonas reinhardtii. We review the current methods used to achieve sustained H(2) evolution and discuss possible approaches to improve H(2) yields, including the optimization of culturing conditions, reducing light-harvesting antennae and targeting auxiliary electron transport and fermentative pathways that compete with the hydrogenase for reductant. Finally, industrial scale-up is discussed in the context of photobioreactor design and the future prospects of the field are considered within the broader context of a biorefinery concept. PMID:21807246

  11. Retinal chromophore structure and Schiff base interactions in red-shifted channelrhodopsin-1 from Chlamydomonas augustae.

    PubMed

    Ogren, John I; Mamaev, Sergey; Russano, Daniel; Li, Hai; Spudich, John L; Rothschild, Kenneth J

    2014-06-24

    Channelrhodopsins (ChRs), which form a distinct branch of the microbial rhodopsin family, control phototaxis in green algae. Because ChRs can be expressed and function in neuronal membranes as light-gated cation channels, they have rapidly become an important optogenetic tool in neurobiology. While channelrhodopsin-2 from the unicellular alga Chlamydomonas reinhardtii (CrChR2) is the most commonly used and extensively studied optogenetic ChR, little is known about the properties of the diverse group of other ChRs. In this study, near-infrared confocal resonance Raman spectroscopy along with hydrogen-deuterium exchange and site-directed mutagenesis were used to study the structure of red-shifted ChR1 from Chlamydomonas augustae (CaChR1). These measurements reveal that (i) CaChR1 has an all-trans-retinal structure similar to those of the light-driven proton pump bacteriorhodopsin (BR) and sensory rhodopsin II but different from that of the mixed retinal composition of CrChR2, (ii) lowering the pH from 7 to 2 or substituting neutral residues for Glu169 or Asp299 does not significantly shift the ethylenic stretch frequency more than 1-2 cm(-1) in contrast to BR in which a downshift of 7-9 cm(-1) occurs reflecting neutralization of the Asp85 counterion, and (iii) the CaChR1 protonated Schiff base (SB) has stronger hydrogen bonding than BR. A model is proposed to explain these results whereby at pH 7 the predominant counterion to the SB is Asp299 (the homologue to Asp212 in BR) while Glu169 (the homologue to Asp85 in BR) exists in a neutral state. We observe an unusual constancy of the resonance Raman spectra over the broad range from pH 9 to 2 and discuss its implications. These results are in accord with recent visible absorption and current measurements of CaChR1 [Sineshchekov, O. A., et al. (2013) Intramolecular proton transfer in channelrhodopsins. Biophys. J. 104, 807-817; Li, H., et al. (2014) Role of a helix B lysine residue in the photoactive site in

  12. A fluorescence-activated cell sorting-based strategy for rapid isolation of high-lipid Chlamydomonas mutants

    PubMed Central

    Terashima, Mia; Freeman, Elizabeth S; Jinkerson, Robert E; Jonikas, Martin C

    2015-01-01

    There is significant interest in farming algae for the direct production of biofuels and valuable lipids. Chlamydomonas reinhardtii is the leading model system for studying lipid metabolism in green algae, but current methods for isolating mutants of this organism with a perturbed lipid content are slow and tedious. Here, we present the Chlamydomonas high-lipid sorting (CHiLiS) strategy, which enables enrichment of high-lipid mutants by fluorescence-activated cell sorting (FACS) of pooled mutants stained with the lipid-sensitive dye Nile Red. This method only takes 5 weeks from mutagenesis to mutant isolation. We developed a staining protocol that allows quantification of lipid content while preserving cell viability. We improved separation of high-lipid mutants from the wild type by using each cell's chlorophyll fluorescence as an internal control. We initially demonstrated 20-fold enrichment of the known high-lipid mutant sta1 from a mixture of sta1 and wild-type cells. We then applied CHiLiS to sort thousands of high-lipid cells from a pool of about 60 000 mutants. Flow cytometry analysis of 24 individual mutants isolated by this approach revealed that about 50% showed a reproducible high-lipid phenotype. We further characterized nine of the mutants with the highest lipid content by flame ionization detection and mass spectrometry lipidomics. All mutants analyzed had a higher triacylglycerol content and perturbed whole-cell fatty acid composition. One arbitrarily chosen mutant was evaluated by microscopy, revealing larger lipid droplets than the wild type. The unprecedented throughput of CHiLiS opens the door to a systems-level understanding of green algal lipid biology by enabling genome-saturating isolation of mutants in key genes. PMID:25267488

  13. Evaluation of three herbicide resistance genes for use in genetic transformations and for potential crop protection in algae production.

    PubMed

    Brueggeman, Andrew J; Bruggeman, Andrew J; Kuehler, Daniel; Weeks, Donald P

    2014-09-01

    Genes conferring resistance to the herbicides glyphosate, oxyfluorfen and norflurazon were developed and tested for use as dominant selectable markers in genetic transformation of Chlamydomonas reinhardtii and as potential tools for the protection of commercial-scale algal production facilities against contamination by organisms sensitive to these broad-spectrum herbicides. A synthetic glyphosate acetyltransferase (GAT) gene, when fitted with a strong Chlamydomonas promoter, conferred a 2.7×-fold increase in tolerance to the EPSPS inhibitor, glyphosate, in transgenic cells compared with progenitor WT cells. A mutant Chlamydomonas protoporphyrinogen oxidase (protox, PPO) gene previously shown to produce an enzyme insensitive to PPO-inhibiting herbicides, when genetically engineered, generated transgenic cells able to tolerate up to 136× higher levels of the PPO inhibitor, oxyfluorfen, than nontransformed cells. Genetic modification of the Chlamydomonas phytoene desaturase (PDS) gene-based gene sequences found in various norflurazon-resistant organisms allowed production of transgenic cells tolerant to 40× higher levels of norflurazon than nontransgenic cells. The high efficiency of all three herbicide resistance genes in producing transgenic cells demonstrated their suitability as dominant selectable markers for genetic transformation of Chlamydomonas and, potentially, other eukaryotic algae. However, the requirement for high concentrations of glyphosate and its associated negative effects on cell growth rates preclude its consideration for use in large-scale production facilities. In contrast, only low doses of norflurazon and oxyfluorfen (~1.5 μm and ~0.1 μm, respectively) are required for inhibition of cell growth, suggesting that these two herbicides may prove effective in large-scale algal production facilities in suppressing growth of organisms sensitive to these herbicides. PMID:24796724

  14. Phenotypic Diversity of Hydrogen Production in Chlorophycean Algae Reflects Distinct Anaerobic Metabolisms

    SciTech Connect

    Meuser, J. E.; Ananyev, G.; Wittig, L. E.; Kosourov, S.; Ghirardi, M. L.; Seibert, M.; Dismukes, G. C.; Posewitz, M. C.

    2009-01-01

    Several species of green algae use [FeFe]-hydrogenases to oxidize and/or produce H{sub 2} during anoxia. To further define unique aspects of algal hydrogenase activity, the well-studied anaerobic metabolisms of Chlamydomonas reinhardtii were compared with four strains of Chlamydomonas moewusii and a Lobochlamys culleus strain. In vivo and in vitro hydrogenase activity, starch accumulation/degradation, and anaerobic end product secretion were analyzed. The C. moewusii strains showed the most rapid induction of hydrogenase activity, congruent with high rates of starch catabolism, and anoxic metabolite accumulation. Intriguingly, we observed significant differences in morphology and hydrogenase activity in the C. moewusii strains examined, likely the result of long-term adaptation and/or genetic drift during culture maintenance. Of the C. moewusii strains examined, SAG 24.91 showed the highest in vitro hydrogenase activity. However, SAG 24.91 produced little H{sub 2} under conditions of sulfur limitation, which is likely a consequence of its inability to utilize exogenous acetate. In L. culleus, hydrogenase activity was minimal unless pulsed light was used to induce significant H2 photoproduction. Overall, our results demonstrate that unique anaerobic acclimation strategies have evolved in distinct green algae, resulting in differential levels of hydrogenase activity and species-specific patterns of NADH reoxidation during anoxia.

  15. Arsoniumphospholipid in algae*

    PubMed Central

    Cooney, Robert V.; Mumma, R. O.; Benson, A. A.

    1978-01-01

    A novel phospholipid containing arsenic was formed by all marine algae cultured in [74As]arsenate. Components of the labeled algal extracts readily separated by two-dimensional paper radiochromatography. Base-catalyzed deacylation of the major lipid yielded a phosphodiester identical to one of the two major water-soluble compounds. Acid or enzymic hydrolysis of the phosphodiester produced a product identified as trimethylarsoniumalactic acid. The structure of the phospholipid therefore is O-phosphatidyltrimethylarsoniumlactic acid. Detoxication of arsenate by marine algae leads to accumulation of the arsoniumphospholipid as a major reservoir for arsenic. Its degradation to trimethylarsoniumbetaine, dimethylarsinic acid, methanearsonic acid, and arsenate in marine food chains and its metabolism in human beings are of considerable interest. Images PMID:16592562

  16. Importance of algae as a potential source of biofuel.

    PubMed

    Singh, A K; Singh, M P

    2014-01-01

    Algae have a great potential source of biofuels and also have unique importance to reduce gaseous emissions, greenhouse gases, climatic changes, global warming receding of glaciers, rising sea levels and loss of biodiversity. The microalgae, like Scenedesmus obliquus, Neochloris oleabundans, Nannochloropsis sp., Chlorella emersonii, and Dunaliella tertiolecta have high oil content. Among the known algae, Scenedesmus obliquus is one of the most potential sources for biodiesel as it has adequate fatty acid (linolenic acid) and other polyunsaturated fatty acids. Bio—ethanol is already in the market of United States of America and Europe as an additive in gasoline. Bio—hydrogen is the cleanest biofuel and extensive efforts are going on to bring it to market at economical price. This review highlights recent development and progress in the field of algae as a potential source of biofuel. PMID:25535720

  17. Filling Knowledge Gaps in Biological Networks: integrating global approaches to understand H2 metabolism in Chlamydomonas reinhardtii - Final Report

    SciTech Connect

    Posewitz, Matthew C

    2011-06-30

    The green alga Chlamydomonas reinhardtii (Chlamydomonas) has numerous genes encoding enzymes that function in fermentative pathways. Among these genes, are the [FeFe]-hydrogenases, pyruvate formate lyase, pyruvate ferredoxin oxidoreductase, acetate kinase, and phosphotransacetylase. We have systematically undertaken a series of targeted mutagenesis approaches to disrupt each of these key genes and omics techniques to characterize alterations in metabolic flux. Funds from DE-FG02-07ER64423 were specifically leveraged to generate mutants with disruptions in the genes encoding the [FeFe]-hydrogenases HYDA1 and HYDA2, pyruvate formate lyase (PFL1), and in bifunctional alcohol/aldehyde alcohol dehydrogenase (ADH1). Additionally funds were used to conduct global transcript profiling experiments of wildtype Chlamydomonas cells, as well as of the hydEF-1 mutant, which is unable to make H2 due to a lesion in the [FeFe]-hydrogenase biosynthetic pathway. In the wildtype cells, formate, acetate and ethanol are the dominant fermentation products with traces of CO2 and H2 also being produced. In the hydEF-1 mutant, succinate production is increased to offset the loss of protons as a terminal electron acceptor. In the pfl-1 mutant, lactate offsets the loss of formate production, and in the adh1-1 mutant glycerol is made instead of ethanol. To further probe the system, we generated a double mutant (pfl1-1 adh1) that is unable to synthesize both formate and ethanol. This strain, like the pfl1 mutants, secreted lactate, but also exhibited a significant increase in the levels of extracellular glycerol, acetate, and intracellular reduced sugars, and a decline in dark, fermentative H2 production. Whereas wild-type Chlamydomonas fermentation primarily produces formate and ethanol, the double mutant performs a complete rerouting of the glycolytic carbon to lactate and glycerol. Lastly, transcriptome data have been analysed for both the wildtype and hydEF-1, that correlate with our

  18. Real-time monitoring of genetically modified Chlamydomonas reinhardtii during the Foton M3 space mission

    NASA Astrophysics Data System (ADS)

    Lambreva, M.; Rea, G.; Antonacci, A.; Serafini, A.; Damasso, M.; Pastorelli, S.; Margonelli, A.; Johanningmeier, U.; Bertalan, I.; Pezzotti, G.; Giardi, M. T.

    2008-09-01

    Long-term space exploration, colonization or habitation requires biological life support systems capable to cope with the deleterious space environment. The use of oxygenic photosynthetic microrganisms is an intriguing possibility mainly for food, O2 and nutraceutical compounds production. The critical points of utilizing plants- or algae-based life support systems are the microgravity and the ionizing radiation, which can influence the performance of these organisms. The aim of the present study was to assess the effects of space environment on the photosynthetic activity of various microrganisms and to select space stresstolerant strains. Photosystem II D1 protein sitedirected and random mutants of the unicellular green alga Chlamydomonas reinhardtii [1] were used as a model system to test and select the amino acid substitutions capable to account for space stress tolerance. We focussed our studies also on the accumulation of the Photosystem II photoprotective carotenoids (the xantophylls violaxanthin, anteraxanthin and zeaxanthin), powerful antioxidants that epidemiological studies demonstrated to be human vision protectors. For this purpose some mutants modified at the level of enzymes involved in the biosynthesis of xanthophylls were included in the study [2]. To identify the consequences of the space environment on the photosynthetic apparatus the changes in the Photosystem II efficiency were monitored in real time during the ESA-Russian Foton- M3 mission in September 2007. For the space flight a high-tech, multicell fluorescence detector, Photo-II, was designed and built by the Centre for Advanced Research in Space Optics in collaboration with Kayser-Italy, Biosensor and DAS. Photo-II is an automatic device developed to measure the chlorophyll fluorescence and to provide a living conditions for several different algae strains (Fig.1). Twelve different C. reinhardti strains were analytically selected and two replications for each strain were brought to space

  19. Effects of nitrogen and phosphorus on arsenite accumulation, oxidation, and toxicity in Chlamydomonas reinhardtii.

    PubMed

    Wang, Ning-Xin; Huang, Bin; Xu, Shen; Wei, Zhong-Bo; Miao, Ai-Jun; Ji, Rong; Yang, Liu-Yan

    2014-12-01

    We studied arsenite (iAs(III)) accumulation, oxidation, and toxicity in the freshwater green alga Chlamydomonas reinhardtii under nutrient-enriched (+NP), phosphorus-limited (-P), and nitrogen-limited (-N) conditions. The -P alga (55.1 μM) had a Michaelis constant (Kd) for uptake approximately one tenth of the +NP (419 μM) and -N (501 μM) cells, indicating iAs(III) uptake inhibition by extracellular phosphate. This conclusion was supported by the hyperbolic reduction in iAs(III) uptake rate (V) from 9.2 to 0.8 μmol/g-dw/h when the extracellular phosphate concentration went up from 0 to 250 μM. The maximal iAs(III) uptake rate (Vmax) of the -N alga (24.3 μmol/g-dw/h) was twice as much as that of the +NP (12 μmol/g-dw/h) and -P (8.1 μmol/g-dw/h) cells. It implies that more arsenic transporters were synthesized under the -N condition. Once accumulated, iAs(III) was oxidized and a higher proportion of arsenate (iAs(V)) was observed at lower [As]dis or under nutrient-limited conditions. Nevertheless, iAs(III) oxidation mainly occurred outside the cells with the extent of oxidation reciprocal to [As]dis. Based on the logistic modeling of the concentration-response curves in the +NP, -P, and -N toxicity tests, iAs(III) had an [As]dis-based EC50 of 1763, 13.1, and 1208 μM and an intracellular arsenic concentration based EC50 of 35.6, 28.8, and 195 μmol/g-dw, respectively. Higher iAs(III) toxicity to the -P cells occured because of their increased iAs(III) accumulation, whereas the underlying mechanisms why the -N alga was more tolerant need to be further revealed. Overall, both N and P had remarkable effects on the behavior and effects of iAs(III), which cannot be disregarded in the biogeochemical cycling research of arsenic. PMID:25456231

  20. Studies on flagellar shortening in Chlamydomonas reinhardtii

    SciTech Connect

    Cherniack, J.

    1985-01-01

    Flagellar shortening of Chlamydomonas reinhardtii was promoted by sodium chloride, pyrophosphate (sodium, potassium and ammonium salts), EDTA and EGTA, succinate, citrate and oxalate (sodium salts), caffeine and aminophylline. Removal of calcium from the medium potentiated the effects of these agents in inducing shortening. Investigations of the release of phosphorylated compounds to the medium during pyrophosphate-induced flagellar shortening of cells pre-labelled with /sup 32/P, revealed an as yet unidentified /sup 32/P-labelled compound with distinct chromatographic properties. Chromatography and electrophoresis indicates that it is a small, highly polar molecule with a high charge to mass ratio, containing thermo- and acid-labile phosphate linkages. Investigations showed of the release of /sup 35/S-labelled protein to the medium from cells pre-labelled with /sup 35/S-sulfate showed that flagellated cells released two prominent polypeptides which comigrated with ..cap alpha..- and ..beta..-flagellar tubulin on SDS polyacrylamide gel electrophoresis, while deflagellated cells did not.

  1. Patching Holes in the Chlamydomonas Genome.

    PubMed

    Tulin, Frej; Cross, Frederick R

    2016-01-01

    The Chlamydomonas genome has been sequenced, assembled, and annotated to produce a rich resource for genetics and molecular biology in this well-studied model organism. However, the current reference genome contains ∼1000 blocks of unknown sequence ('N-islands'), which are frequently placed in introns of annotated gene models. We developed a strategy to search for previously unknown exons hidden within such blocks, and determine the sequence, and exon/intron boundaries, of such exons. These methods are based on assembly and alignment of short cDNA and genomic DNA reads, completely independent of prior reference assembly or annotation. Our evidence indicates that a substantial proportion of the annotated intronic N-islands contain hidden exons. For most of these, our algorithm recovers full exonic sequence with associated splice junctions and exon-adjacent intronic sequence. These new exons represent de novo sequence generally present nowhere in the assembled genome, and the added sequence improves evolutionary conservation of the predicted encoded peptides. PMID:27175017

  2. Patching Holes in the Chlamydomonas Genome

    PubMed Central

    Tulin, Frej; Cross, Frederick R.

    2016-01-01

    The Chlamydomonas genome has been sequenced, assembled, and annotated to produce a rich resource for genetics and molecular biology in this well-studied model organism. However, the current reference genome contains ∼1000 blocks of unknown sequence (‘N-islands’), which are frequently placed in introns of annotated gene models. We developed a strategy to search for previously unknown exons hidden within such blocks, and determine the sequence, and exon/intron boundaries, of such exons. These methods are based on assembly and alignment of short cDNA and genomic DNA reads, completely independent of prior reference assembly or annotation. Our evidence indicates that a substantial proportion of the annotated intronic N-islands contain hidden exons. For most of these, our algorithm recovers full exonic sequence with associated splice junctions and exon-adjacent intronic sequence. These new exons represent de novo sequence generally present nowhere in the assembled genome, and the added sequence improves evolutionary conservation of the predicted encoded peptides. PMID:27175017

  3. Effect of sonication frequency on the disruption of algae.

    PubMed

    Kurokawa, Masaki; King, Patrick M; Wu, Xiaoge; Joyce, Eadaoin M; Mason, Timothy J; Yamamoto, Ken

    2016-07-01

    In this study, the efficiency of ultrasonic disruption of Chaetoceros gracilis, Chaetoceros calcitrans, and Nannochloropsis sp. was investigated by applying ultrasonic waves of 0.02, 0.4, 1.0, 2.2, 3.3, and 4.3 MHz to algal suspensions. The results showed that reduction in the number of algae was frequency dependent and that the highest efficiency was achieved at 2.2, 3.3, and 4.3MHz for C. gracilis, C. calcitrans, and Nannochloropsis sp., respectively. A review of the literature suggested that cavitation, rather than direct effects of ultrasonication, are required for ultrasonic algae disruption, and that chemical effects are likely not the main mechanism for algal cell disruption. The mechanical resonance frequencies estimated by a shell model, taking into account elastic properties, demonstrated that suitable disruption frequencies for each alga were associated with the cell's mechanical properties. Taken together, we consider here that physical effects of ultrasonication were responsible for algae disruption. PMID:26964936

  4. Settlement of marine periphytic algae in a tropical estuary

    NASA Astrophysics Data System (ADS)

    Nayar, S.; Goh, B. P. L.; Chou, L. M.

    2005-08-01

    This note describes settlement studies of marine periphytic algae on glass substrata in a tropical estuary in Singapore. The rates of production in terms of 14C radiotracer uptake, biomass in terms of chlorophyll a, community structure and cell abundance were measured from the settled periphytic algae at various depths in the water column and compared with the prevailing hydrographical conditions. Relatively higher periphytic algal settlement was observed at 1 m depth, even though it was not statistically different from other depths. Diatoms such as Skeletonema costatum and Thalassiosira rotula dominated the assemblage, together with the marine cyanobacteria Synechococcus sp. The three settlement parameters viz., periphytic algal production, chlorophyll a and cell counts showed significant differences between the days of settlement, with no significant differences observed for different depths. The periphytic algal community in this study comprised 30 microalgal species, dominated by diatoms (78%), followed by cyanobacteria (19% - primarily Synechococcus sp.), green flagellates (1%), dinoflagellates (1%) and other forms accounting for the remaining 1% of the total cell counts. Correlation studies and principal component analysis (PCA) revealed significant influence of silicate concentrations in the water column with the settlement of periphytic algae in this estuary. Though photoinhibited at the surface, photosynthetically available radiation did not seem to influence the overall settlement of periphytic algae. Diatoms and Synechococcus in the periphytic algal community were influenced by water temperature, PAR, pH and dissolved oxygen as seen in the PCA plots.

  5. Analysis of Axonemal Assembly During Ciliary Regeneration in Chlamydomonas.

    PubMed

    Hunter, Emily L; Sale, Winfield S; Alford, Lea M

    2016-01-01

    Chlamydomonas reinhardtii is an outstanding model genetic organism for study of assembly of cilia. Here, methods are described for synchronization of ciliary regeneration in Chlamydomonas to analyze the sequence in which ciliary proteins assemble. In addition, the methods described allow analysis of the mechanisms involved in regulation of ciliary length, the proteins required for ciliary assembly, and the temporal expression of genes encoding ciliary proteins. Ultimately, these methods can contribute to discovery of conserved genes that when defective lead to abnormal ciliary assembly and human disease. PMID:27514926

  6. Heat-stable oral alga-based vaccine protects mice from Staphylococcus aureus infection.

    PubMed

    Dreesen, Imke A J; Charpin-El Hamri, Ghislaine; Fussenegger, Martin

    2010-02-01

    While 15 million deaths per year are caused by communicable pathogens worldwide, health care authorities emphasize the considerable impact of poverty on the incidence of infectious diseases. The emergence of antigen-expressing plant tissues (e.g. rice, tomato, potato) has indicated the potential of land plants for low-cost vaccines in oral immunization programs. In this study, we engineered the chloroplasts of the unicellular green alga Chlamydomonas reinhardtii for the stable expression of the D2 fibronectin-binding domain of Staphylococcus aureus fused with the cholera toxin B subunit (CTB), under the control of rbcL UTRs. Analysis of sera and faeces of mice, fed for 5 weeks with transgenic algae grown in confined Wave Bioreactor, revealed the induction of specific mucosal and systemic immune responses. Algae-based vaccination significantly reduced the pathogen load in the spleen and the intestine of treated mice and protected 80% of them against lethal doses of S. aureus. Importantly, the alga vaccine was stable for more than 1.5 years at room temperature. These results indicate that C. reinhardtii may play an important role in molecular pharming, as it combines the beneficial features of land plant vaccines, while offering unmatched ease of growth compared to other members of the plant kingdom. PMID:19995584

  7. Laccase-like enzyme activities from chlorophycean green algae with potential for bioconversion of phenolic pollutants.

    PubMed

    Otto, Benjamin; Beuchel, Carl; Liers, Christiane; Reisser, Werner; Harms, Hauke; Schlosser, Dietmar

    2015-06-01

    In order to explore the abundance and potential environmental functions of green algal laccases, we screened various algae for extracellular laccase-like activities, characterized basic features of these activities in selected species and exemplarily studied the transformation of environmental pollutants and complex natural compounds by the laccase of Tetracystis aeria. Oxidation of the classical laccase substrate ABTS was found to be widespread in chlorophycean algae. The oxidation activity detected in members of the 'Scenedesmus' clade was caused by an unknown thermostable low-molecular-mass compound. In contrast, species of the Moewusinia, including Chlamydomonas moewusii and T. aeria, excreted putative 'true' laccases. Phenolic substrates were oxidized by these enzymes optimally at neutral to alkaline pH. The Tetracystis laccase efficiently transformed bisphenol A, 17α-ethinylestradiol, nonylphenol and triclosan in the presence of ABTS as redox mediator, while anthracene, veratrylalcohol and adlerol were not attacked. Lignosulfonate and humic acid underwent slight (de)polymerization reactions in the presence of the laccase and mediator(s), probably involving the oxidation of phenolic constituents. Possible natural functions of the enzymes, such as the synthesis of complex polymers or detoxification processes, may assist the survival of the algae in adverse environments. In contaminated surface waters, laccase-producing green algae might contribute to the environmental breakdown of phenolic pollutants. PMID:25926529

  8. Experimental Definition and Validation of Protein Coding Transcripts in Chlamydomonas reinhardtii

    SciTech Connect

    Kourosh Salehi-Ashtiani; Jason A. Papin

    2012-01-13

    Algal fuel sources promise unsurpassed yields in a carbon neutral manner that minimizes resource competition between agriculture and fuel crops. Many challenges must be addressed before algal biofuels can be accepted as a component of the fossil fuel replacement strategy. One significant challenge is that the cost of algal fuel production must become competitive with existing fuel alternatives. Algal biofuel production presents the opportunity to fine-tune microbial metabolic machinery for an optimal blend of biomass constituents and desired fuel molecules. Genome-scale model-driven algal metabolic design promises to facilitate both goals by directing the utilization of metabolites in the complex, interconnected metabolic networks to optimize production of the compounds of interest. Using Chlamydomonas reinhardtii as a model, we developed a systems-level methodology bridging metabolic network reconstruction with annotation and experimental verification of enzyme encoding open reading frames. We reconstructed a genome-scale metabolic network for this alga and devised a novel light-modeling approach that enables quantitative growth prediction for a given light source, resolving wavelength and photon flux. We experimentally verified transcripts accounted for in the network and physiologically validated model function through simulation and generation of new experimental growth data, providing high confidence in network contents and predictive applications. The network offers insight into algal metabolism and potential for genetic engineering and efficient light source design, a pioneering resource for studying light-driven metabolism and quantitative systems biology. Our approach to generate a predictive metabolic model integrated with cloned open reading frames, provides a cost-effective platform to generate metabolic engineering resources. While the generated resources are specific to algal systems, the approach that we have developed is not specific to algae and

  9. Energy-dissipative supercomplex of photosystem II associated with LHCSR3 in Chlamydomonas reinhardtii.

    PubMed

    Tokutsu, Ryutaro; Minagawa, Jun

    2013-06-11

    Plants and green algae have a low pH-inducible mechanism in photosystem II (PSII) that dissipates excess light energy, measured as the nonphotochemical quenching of chlorophyll fluorescence (qE). Recently, nonphotochemical quenching 4 (npq4), a mutant strain of the green alga Chlamydomonas reinhardtii that is qE-deficient and lacks the light-harvesting complex stress-related protein 3 (LHCSR3), was reported [Peers G, et al. (2009) Nature 462(7272):518-521]. Here, applying a newly established procedure, we isolated the PSII supercomplex and its associated light-harvesting proteins from both WT C. reinhardtii and the npq4 mutant grown in either low light (LL) or high light (HL). LHCSR3 was present in the PSII supercomplex from the HL-grown WT, but not in the supercomplex from the LL-grown WT or mutant. The purified PSII supercomplex containing LHCSR3 exhibited a normal fluorescence lifetime at a neutral pH (7.5) by single-photon counting analysis, but a significantly shorter lifetime at pH 5.5, which mimics the acidified lumen of the thylakoid membranes in HL-exposed chloroplasts. The switch from light-harvesting mode to energy-dissipating mode observed in the LHCSR3-containing PSII supercomplex was sensitive to dicyclohexylcarbodiimide, a protein-modifying agent specific to protonatable amino acid residues. We conclude that the PSII-LHCII-LHCSR3 supercomplex formed in the HL-grown C. reinhardtii cells is capable of energy dissipation on protonation of LHCSR3. PMID:23716695

  10. Pyruvate:Ferredoxin Oxidoreductase Is Coupled to Light-independent Hydrogen Production in Chlamydomonas reinhardtii*

    PubMed Central

    Noth, Jens; Krawietz, Danuta; Hemschemeier, Anja; Happe, Thomas

    2013-01-01

    In anaerobiosis, the green alga Chlamydomonas reinhardtii evolves molecular hydrogen (H2) as one of several fermentation products. H2 is generated mostly by the [Fe-Fe]-hydrogenase HYDA1, which uses plant type ferredoxin PETF/FDX1 (PETF) as an electron donor. Dark fermentation of the alga is mainly of the mixed acid type, because formate, ethanol, and acetate are generated by a pyruvate:formate lyase pathway similar to Escherichia coli. However, C. reinhardtii also possesses the pyruvate:ferredoxin oxidoreductase PFR1, which, like pyruvate:formate lyase and HYDA1, is localized in the chloroplast. PFR1 has long been suggested to be responsible for the low but significant H2 accumulation in the dark because the catalytic mechanism of pyruvate:ferredoxin oxidoreductase involves the reduction of ferredoxin. With the aim of proving the biochemical feasibility of the postulated reaction, we have heterologously expressed the PFR1 gene in E. coli. Purified recombinant PFR1 is able to transfer electrons from pyruvate to HYDA1, using the ferredoxins PETF and FDX2 as electron carriers. The high reactivity of PFR1 toward oxaloacetate indicates that in vivo, fermentation might also be coupled to an anaerobically active glyoxylate cycle. Our results suggest that C. reinhardtii employs a clostridial type H2 production pathway in the dark, especially because C. reinhardtii PFR1 was also able to allow H2 evolution in reaction mixtures containing Clostridium acetobutylicum 2[4Fe-4S]-ferredoxin and [Fe-Fe]-hydrogenase HYDA. PMID:23258532

  11. Photosynthetic responses and accumulation of mesotrione in two freshwater algae.

    PubMed

    Ni, Yan; Lai, Jinhu; Wan, Jinbao; Chen, Lianshui

    2014-01-01

    Mesotrione is a herbicide used for killing annual grasses and broad-leaved weeds in maize. A recent investigation has shown that mesotrione has been detected as an organic contaminant in aquatic environments and may have a negative impact on aquatic organisms. To evaluate the eco-toxicity of mesotrione to algae, experiments focusing on photosynthetic responses and mesotrione accumulation in Microcystis sp. and Scenedesmus quadricauda were carried out. Both algae treated with mesotrione at 0.05-10 mg L(-1) for 7 days reduced the photosynthetic capacity. The fluorescence of chlorophyll a, the maximal PSII activity (Fv/Fm), and the parameters (Ik, α and ETRmax) of rapid light curves (RLCs) in both algae were decreased under mesotrione exposure. The 96 h EC50 values for mesotrione on S. quadricauda and Microcystis sp. were 4.41 and 6.19 mg L(-1), respectively. The latter shows more tolerance to mesotrione. Mesotrione was shown to be readily accumulated by both species. Such uptake of mesotrione led to the rapid removal of mesotrione from the medium. Overall, this study represents the initial comprehensive analyses of Microcystis sp. and S. quadricauda in adaptation to the mesotrione contaminated aquatic ecosystems. PMID:25059419

  12. Independent Control of the Static and Dynamic Components of the Chlamydomonas Flagellar Beat.

    PubMed

    Geyer, Veikko F; Sartori, Pablo; Friedrich, Benjamin M; Jülicher, Frank; Howard, Jonathon

    2016-04-25

    When the green alga Chlamydomonas reinhardtii swims, it uses the breaststroke beat of its two flagella to pull itself forward [1]. The flagellar waveform can be decomposed into a static component, corresponding to an asymmetric time-averaged shape, and a dynamic component, corresponding to the time-varying wave [2]. Extreme lightening conditions photoshock the cell, converting the breaststroke beat into a symmetric sperm-like beat, which causes a reversal of the direction of swimming [3]. Waveform conversion is achieved by a reduction in magnitude of the static component, whereas the dynamic component remains unchanged [2]. The coupling between static and dynamic components, however, is poorly understood, and it is not known whether the static component requires the dynamic component or whether it can exist independently. We used isolated and reactivated axonemes [4] to investigate the relation between the two beat components. We discovered that, when reactivated in the presence of low ATP concentrations, axonemes displayed the static beat component in absence of the dynamic component. Furthermore, we found that the amplitudes of the two components depend on ATP in qualitatively different ways. These results show that the decomposition into static and dynamic components is not just a mathematical concept but that the two components can independently control different aspects of cell motility: the static component controls swimming direction, whereas the dynamic component provides propulsion. PMID:27040779

  13. The response of Chlamydomonas reinhardtii to nitrogen deprivation: a systems biology analysis.

    PubMed

    Park, Jeong-Jin; Wang, Hongxia; Gargouri, Mahmoud; Deshpande, Rahul R; Skepper, Jeremy N; Holguin, F Omar; Juergens, Matthew T; Shachar-Hill, Yair; Hicks, Leslie M; Gang, David R

    2015-02-01

    Drastic alteration in macronutrients causes large changes in gene expression in the photosynthetic unicellular alga Chlamydomonas reinhardtii. Preliminary data suggested that cells follow a biphasic response to this change hinging on the initiation of lipid accumulation, and we hypothesized that drastic repatterning of metabolism also followed this biphasic modality. To test this hypothesis, transcriptomic, proteomic, and metabolite changes that occur under nitrogen (N) deprivation were analyzed. Eight sampling times were selected covering the progressive slowing of growth and induction of oil synthesis between 4 and 6 h after N deprivation. Results of the combined, systems-level investigation indicated that C. reinhardtii cells sense and respond on a large scale within 30 min to a switch to N-deprived conditions turning on a largely gluconeogenic metabolic state, which then transitions to a glycolytic stage between 4 and 6 h after N depletion. This nitrogen-sensing system is transduced to carbon- and nitrogen-responsive pathways, leading to down-regulation of carbon assimilation and chlorophyll biosynthesis, and an increase in nitrogen metabolism and lipid biosynthesis. For example, the expression of nearly all the enzymes for assimilating nitrogen from ammonium, nitrate, nitrite, urea, formamide/acetamide, purines, pyrimidines, polyamines, amino acids and proteins increased significantly. Although arginine biosynthesis enzymes were also rapidly up-regulated, arginine pool size changes and isotopic labeling results indicated no increased flux through this pathway. PMID:25515814

  14. Extensive de novo mutation rate variation between individuals and across the genome of Chlamydomonas reinhardtii

    PubMed Central

    Ness, Rob W.; Morgan, Andrew D.; Vasanthakrishnan, Radhakrishnan B.; Colegrave, Nick; Keightley, Peter D.

    2015-01-01

    Describing the process of spontaneous mutation is fundamental for understanding the genetic basis of disease, the threat posed by declining population size in conservation biology, and much of evolutionary biology. Directly studying spontaneous mutation has been difficult, however, because new mutations are rare. Mutation accumulation (MA) experiments overcome this by allowing mutations to build up over many generations in the near absence of natural selection. Here, we sequenced the genomes of 85 MA lines derived from six genetically diverse strains of the green alga Chlamydomonas reinhardtii. We identified 6843 new mutations, more than any other study of spontaneous mutation. We observed sevenfold variation in the mutation rate among strains and that mutator genotypes arose, increasing the mutation rate approximately eightfold in some replicates. We also found evidence for fine-scale heterogeneity in the mutation rate, with certain sequence motifs mutating at much higher rates, and clusters of multiple mutations occurring at closely linked sites. There was little evidence, however, for mutation rate heterogeneity between chromosomes or over large genomic regions of 200 kbp. We generated a predictive model of the mutability of sites based on their genomic properties, including local GC content, gene expression level, and local sequence context. Our model accurately predicted the average mutation rate and natural levels of genetic diversity of sites across the genome. Notably, trinucleotides vary 17-fold in rate between the most and least mutable sites. Our results uncover a rich heterogeneity in the process of spontaneous mutation both among individuals and across the genome. PMID:26260971

  15. Identification of Novel Mitochondrial Protein Components of Chlamydomonas reinhardtii. A Proteomic Approach1

    PubMed Central

    van Lis, Robert; Atteia, Ariane; Mendoza-Hernández, Guillermo; González-Halphen, Diego

    2003-01-01

    Pure mitochondria of the photosynthetic alga Chlamydomonas reinhardtii were analyzed using blue native-polyacrylamide gel electrophoresis (BN-PAGE). The major oxidative phosphorylation complexes were resolved: F1F0-ATP synthase, NADH-ubiquinone oxidoreductase, ubiquinol-cytochrome c reductase, and cytochrome c oxidase. The oligomeric states of these complexes were determined. The F1F0-ATP synthase runs exclusively as a dimer, in contrast to the C. reinhardtii chloroplast enzyme, which is present as a monomer and subcomplexes. The sequence of a 60-kD protein, associated with the mitochondrial ATP synthase and with no known counterpart in any other organism, is reported. This protein may be related to the strong dimeric character of the algal F1F0-ATP synthase. The oxidative phosphorylation complexes resolved by BN-PAGE were separated into their subunits by second dimension sodium dodecyl sulfate-PAGE. A number of polypeptides were identified mainly on the basis of their N-terminal sequence. Core I and II subunits of complex III were characterized, and their proteolytic activities were predicted. Also, the heterodimeric nature of COXIIA and COXIIB subunits in cytochrome c oxidase was demonstrated. Other mitochondrial proteins like the chaperone HSP60, the alternative oxidase, the aconitase, and the ADP/ATP carrier were identified. BN-PAGE was also used to approach the analysis of the major chloroplast protein complexes of C. reinhardtii. PMID:12746537

  16. Isolation of Chlamydomonas reinhardtii mutants with altered mitochondrial respiration by chlorophyll fluorescence measurement.

    PubMed

    Massoz, Simon; Larosa, Véronique; Horrion, Bastien; Matagne, René F; Remacle, Claire; Cardol, Pierre

    2015-12-10

    The unicellular green alga Chlamydomonas reinhardtii is a model organism for studying energetic metabolism. Most mitochondrial respiratory-deficient mutants characterized to date have been isolated on the basis of their reduced ability to grow in heterotrophic conditions. Mitochondrial deficiencies are usually partly compensated by adjustment of photosynthetic activity and more particularly by transition to state 2. In this work, we explored the opportunity to select mutants impaired in respiration and/or altered in dark metabolism by measuring maximum photosynthetic efficiency by chlorophyll fluorescence analyses (FV/FM). Out of about 2900 hygromycin-resistant insertional mutants generated from wild type or from a mutant strain deficient in state transitions (stt7 strain), 22 were found to grow slowly in heterotrophic conditions and 8 of them also showed a lower FV/FM value. Several disrupted coding sequences were identified, including genes coding for three different subunits of respiratory-chain complex I (NUO9, NUOA9, NUOP4) or for isocitrate lyase (ICL1). Overall, the comparison of respiratory mutants obtained in wild-type or stt7 genetic backgrounds indicated that the FV/FM value can be used to isolate mutants severely impaired in dark metabolism. PMID:26022424

  17. Phosphoprotein SAK1 is a regulator of acclimation to singlet oxygen in Chlamydomonas reinhardtii

    PubMed Central

    Wakao, Setsuko; Chin, Brian L; Ledford, Heidi K; Dent, Rachel M; Casero, David; Pellegrini, Matteo; Merchant, Sabeeha S; Niyogi, Krishna K

    2014-01-01

    Singlet oxygen is a highly toxic and inevitable byproduct of oxygenic photosynthesis. The unicellular green alga Chlamydomonas reinhardtii is capable of acclimating specifically to singlet oxygen stress, but the retrograde signaling pathway from the chloroplast to the nucleus mediating this response is unknown. Here we describe a mutant, singlet oxygen acclimation knocked-out 1 (sak1), that lacks the acclimation response to singlet oxygen. Analysis of genome-wide changes in RNA abundance during acclimation to singlet oxygen revealed that SAK1 is a key regulator of the gene expression response during acclimation. The SAK1 gene encodes an uncharacterized protein with a domain conserved among chlorophytes and present in some bZIP transcription factors. The SAK1 protein is located in the cytosol, and it is induced and phosphorylated upon exposure to singlet oxygen, suggesting that it is a critical intermediate component of the retrograde signal transduction pathway leading to singlet oxygen acclimation. DOI: http://dx.doi.org/10.7554/eLife.02286.001 PMID:24859755

  18. Eyespot-dependent determination of the phototactic sign in Chlamydomonas reinhardtii.

    PubMed

    Ueki, Noriko; Ide, Takahiro; Mochiji, Shota; Kobayashi, Yuki; Tokutsu, Ryutaro; Ohnishi, Norikazu; Yamaguchi, Katsushi; Shigenobu, Shuji; Tanaka, Kan; Minagawa, Jun; Hisabori, Toru; Hirono, Masafumi; Wakabayashi, Ken-Ichi

    2016-05-10

    The biflagellate green alga Chlamydomonas reinhardtii exhibits both positive and negative phototaxis to inhabit areas with proper light conditions. It has been shown that treatment of cells with reactive oxygen species (ROS) reagents biases the phototactic sign to positive, whereas that with ROS scavengers biases it to negative. Taking advantage of this property, we isolated a mutant, lts1-211, which displays a reduction-oxidation (redox) dependent phototactic sign opposite to that of the wild type. This mutant has a single amino acid substitution in phytoene synthase, an enzyme that functions in the carotenoid-biosynthesis pathway. The eyespot contains large amounts of carotenoids and is crucial for phototaxis. Most lts1-211 cells have no detectable eyespot and reduced carotenoid levels. Interestingly, the reversed phototactic-sign phenotype of lts1-211 is shared by other eyespot-less mutants. In addition, we directly showed that the cell body acts as a convex lens. The lens effect of the cell body condenses the light coming from the rear onto the photoreceptor in the absence of carotenoid layers, which can account for the reversed-phototactic-sign phenotype of the mutants. These results suggest that light-shielding property of the eyespot is essential for determination of phototactic sign. PMID:27122315

  19. Induction and Segregation of Chloroplast Mutations in Vegetative Cell Cultures of Chlamydomonas Reinhardtii

    PubMed Central

    Lee, Robert W.; Haughn, George W.

    1980-01-01

    The single chloroplast of the alga Chlamydomonas reinhardtii contains at least 100 copies of the chloroplast chromosome. It is not known how the chloroplast (or cell) becomes homoplasmic for a mutation that arises in one of these copies. Under suitable selection conditions, clones with chloroplast mutations for streptomycin resistance induced by methyl methanesulfonate can be recovered with direct plating after mutagenesis. Using an adaptation of the Luria-Delbrück fluctuation test, mutagenized cultures grown on nonselective liquid medium for seven to nine doublings show negligible proliferation of cells capable of forming such mutant colonies. In contrast, cells among the same cultures with reduced nuclear mutations conferring streptomycin resistance reveal considerable clonal propagation prior to plating on selection medium. Reconstruction growth-rate experiments show no reduced growth of cells with chloroplast mutations relative to either wild-type cells or to those with nuclear mutations. We propose that newly arising chloroplast mutations and their copies are usually transmitted to only one daughter cell for several cell generations by reductional divisions of the chloroplast genome. In the absence of recombination and mixing, such a reductional partition of chloroplast alleles would readily permit the formation of homoplasmic lines without the need for selection. PMID:17249064

  20. The Awesome Power of Dikaryons for Studying Flagella and Basal Bodies in Chlamydomonas reinhardtii

    PubMed Central

    Dutcher, Susan K.

    2014-01-01

    Cilia/flagella and basal bodies/centrioles play key roles in human health and homeostasis. Among the organisms used to study these microtubule-based organelles, the green alga Chlamydomonas reinhardtii has several advantages. One is the existence of a temporary phase of the life cycle, termed the dikaryon. These cells are formed during mating when the cells fuse and the behavior of flagella from two genetically distinguishable parents can be observed. During this stage, the cytoplasms mix allowing for a defect in the flagella of one parent to be rescued by proteins from the other parent. This offers the unique advantage of adding back wild-type gene product or labeled protein at endogenous levels that can used to monitor various flagellar and basal body phenotypes. Mutants that show rescue and ones that fail to show rescue are both informative about the nature of the flagella and basal body defects. When rescue occurs, it can be used to determine the mutant gene product and to follow the temporal and spatial patterns of flagellar assembly. This review describes many examples of insights into basal body and flagellar proteins’ function and assembly that have been discovered using dikaryons and discusses the potential for further analyses. PMID:24272949

  1. Oxidative stress contributes to autophagy induction in response to endoplasmic reticulum stress in Chlamydomonas reinhardtii.

    PubMed

    Pérez-Martín, Marta; Pérez-Pérez, María Esther; Lemaire, Stéphane D; Crespo, José L

    2014-10-01

    The accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) results in the activation of stress responses, such as the unfolded protein response or the catabolic process of autophagy to ultimately recover cellular homeostasis. ER stress also promotes the production of reactive oxygen species, which play an important role in autophagy regulation. However, it remains unknown whether reactive oxygen species are involved in ER stress-induced autophagy. In this study, we provide evidence connecting redox imbalance caused by ER stress and autophagy activation in the model unicellular green alga Chlamydomonas reinhardtii. Treatment of C. reinhardtii cells with the ER stressors tunicamycin or dithiothreitol resulted in up-regulation of the expression of genes encoding ER resident endoplasmic reticulum oxidoreductin1 oxidoreductase and protein disulfide isomerases. ER stress also triggered autophagy in C. reinhardtii based on the protein abundance, lipidation, cellular distribution, and mRNA levels of the autophagy marker ATG8. Moreover, increases in the oxidation of the glutathione pool and the expression of oxidative stress-related genes were detected in tunicamycin-treated cells. Our results revealed that the antioxidant glutathione partially suppressed ER stress-induced autophagy and decreased the toxicity of tunicamycin, suggesting that oxidative stress participates in the control of autophagy in response to ER stress in C. reinhardtii In close agreement, we also found that autophagy activation by tunicamycin was more pronounced in the C. reinhardtii sor1 mutant, which shows increased expression of oxidative stress-related genes. PMID:25143584

  2. The metabolome of Chlamydomonas reinhardtii following induction of anaerobic H2 production by sulfur depletion.

    PubMed

    Matthew, Timmins; Zhou, Wenxu; Rupprecht, Jens; Lim, Lysha; Thomas-Hall, Skye R; Doebbe, Anja; Kruse, Olaf; Hankamer, Ben; Marx, Ute C; Smith, Steven M; Schenk, Peer M

    2009-08-28

    The metabolome of the model species Chlamydomonas reinhardtii has been analyzed during 120 h of sulfur depletion to induce anaerobic hydrogen (H(2)) production, using NMR spectroscopy, gas chromatography coupled to mass spectrometry, and TLC. The results indicate that these unicellular green algae consume freshly supplied acetate in the medium to accumulate energy reserves during the first 24 h of sulfur depletion. In addition to the previously reported accumulation of starch, large amounts of triacylglycerides were deposited in the cells. During the early 24- to 72-h time period fermentative energy metabolism lowered the pH, H(2) was produced, and amino acid levels generally increased. In the final phase from 72 to 120 h, metabolism slowed down leading to a stabilization of pH, even though some starch and most triacylglycerides remained. We conclude that H(2) production does not slow down due to depletion of energy reserves but rather due to loss of essential functions resulting from sulfur depletion or due to a build-up of the toxic fermentative products formate and ethanol. PMID:19478077

  3. Genetic analysis of suppressors of the PF10 mutation in Chlamydomonas reinhardtii

    SciTech Connect

    Dutcher, S.K.; Gibbons, W.; Inwood, W.B.

    1988-12-01

    A mutation at the PF10 locus of the unicellular green alga Chlamydomonas reinhardtii leads to abnormal cell motility. The asymmetric form of the ciliary beat stroke characteristic of wild-type flagella is modified by this mutation to a nearly symmetric beat. We report here that this abnormal motility is a conditional phenotype that depends on light intensity. In the absence of light or under low light intensities, the motility is more severely impaired than at higher light intensities. By UV mutagenesis we obtained 11 intragenic and 70 extragenic strains that show reversion of the pf10 motility phenotype observed in low light. The intragenic events reverted the motility phenotype of the pf10 mutation completely. The extragenic events define at least seven suppressor loci; these map to linkage groups IV, VII, IX, XI, XII and XVII. Suppressor mutations at two of the seven loci (LIS1 and LIS2) require light for their suppressor activity. Forty-eight of the 70 extragenic suppressors were examined in heterozygous diploid cells; 47 of these mutants were recessive to the wild-type allele and one mutant (bop5-1) was dominant to the wild-type allele. Complementation analysis of the 47 recessive mutants showed unusual patterns. Most mutants within a recombinationally defined group failed to complement one another, although there were pairs that showed intra-allelic complementation. Additionally, some of the mutants at each recombinationally defined locus failed to complement mutants at other loci. They define dominant enhancers of one another.

  4. Adaptation of Chlamydomonas reinhardtii high-CO sub 2 -requiring mutants to limiting CO sub 2

    SciTech Connect

    Suzuki, K.; Spalding, M.H. )

    1989-07-01

    Photosynthetic characteristics of four high-CO{sub 2}-requiring mutants of Chlamydomonas reinhardtii were compared to those of wild type before and after a 24-hour exposure to limiting CO{sub 2} concentrations. The four mutants represent two loci involved in the CO{sub 2}-concentrating system of this unicellular alga. All mutants had a lower photosynthetic affinity for inorganic carbon than did the wild type when grown at an elevated CO{sub 2} concentration, indicating that the genetic lesion in each is expressed even at elevated CO{sub 2} concentrations. Wild type and all four mutants exhibited adaptive responses to limiting CO{sub 2} characteristic of the induction of the CO{sub 2}-concentrating system, resulting in an increased affinity for inorganic carbon only in wild type. Although other components of the CO{sub 2}-concentrating system were induced in these mutants, the defective component in each was sufficient to prevent any increase in the affinity for inorganic carbon. It was concluded that the genes corresponding to the ca-1 and pmp-1 loci exhibit at least partially constitutive expression and that all components of the CO{sub 2}-concentrating system may be required to significantly affect the photosynthetic affinity for inorganic carbon.

  5. Transcriptome Analysis of Manganese-deficient Chlamydomonas reinhardtii Provides Insight on the Chlorophyll Biosynthesis Pathway

    SciTech Connect

    Lockhart, Ainsley; Zvenigorodsky, Natasha; Pedraza, Mary Ann; Lindquist, Erika

    2011-08-11

    The biosynthesis of chlorophyll and other tetrapyrroles is a vital but poorly understood process. Recent genomic advances with the unicellular green algae Chlamydomonas reinhardtii have created opportunity to more closely examine the mechanisms of the chlorophyll biosynthesis pathway via transcriptome analysis. Manganese is a nutrient of interest for complex reactions because of its multiple stable oxidation states and role in molecular oxygen coordination. C. reinhardtii was cultured in Manganese-deplete Tris-acetate-phosphate (TAP) media for 24 hours and used to create cDNA libraries for sequencing using Illumina TruSeq technology. Transcriptome analysis provided intriguing insight on possible regulatory mechanisms in the pathway. Evidence supports similarities of GTR (Glutamyl-tRNA synthase) to its Chlorella vulgaris homolog in terms of Mn requirements. Data was also suggestive of Mn-related compensatory up-regulation for pathway proteins CHLH1 (Manganese Chelatase), GUN4 (Magnesium chelatase activating protein), and POR1 (Light-dependent protochlorophyllide reductase). Intriguingly, data suggests possible reciprocal expression of oxygen dependent CPX1 (coproporphyrinogen III oxidase) and oxygen independent CPX2. Further analysis using RT-PCR could provide compelling evidence for several novel regulatory mechanisms in the chlorophyll biosynthesis pathway.

  6. Volatile fractions of landfill leachates and their effect on Chlamydomonas reinhardtii: In vivo chlorophyll a fluorescence

    SciTech Connect

    Brack, W.; Rottler, H.; Frank, H.

    1998-10-01

    Volatile organic compounds such as short-chain halogenated hydrocarbons and alkylated benzenes are widely used as solvents or as intermediates in the chemical industry, and some of them are fuel components. Dichloromethane, trichloroethene, 1,1,1-trichloroethane, and tetrachloroethene have been produced in amounts of 500,000 to 1 million t/year, 80 to 100% of which are released to the environment. The production of toluene, a major component of fuels for internal combustion engines, amounts to about 30 million t/year. A method for identification of toxic volatile constituents of landfill leachates is presented that combines bioassay-compatible sample preparation, chemical analysis, and a bioassay based on in vivo chlorophyll a fluorescence of the green alga Chlamydomonas reinhardtii. Two major pathways of toxicity were identified by comparing fluorescence patterns: specific toxicity of hydrogen sulfide, and narcotic action of nonreactive organic compounds. For quantification, the contributions of identified compounds were calculated using toxic units. The ecotoxicologic relevance of volatile fractions from hazardous waste leachates was shown.

  7. Improved automated monitoring and new analysis algorithm for circadian phototaxis rhythms in Chlamydomonas

    PubMed Central

    Gaskill, Christa; Forbes-Stovall, Jennifer; Kessler, Bruce; Young, Mike; Rinehart, Claire A.; Jacobshagen, Sigrid

    2010-01-01

    Automated monitoring of circadian rhythms is an efficient way of gaining insight into oscillation parameters like period and phase for the underlying pacemaker of the circadian clock. Measurement of the circadian rhythm of phototaxis (swimming towards light) exhibited by the green alga Chlamydomonas reinhardtii has been automated by directing a narrow and dim light beam through a culture at regular intervals and determining the decrease in light transmittance due to the accumulation of cells in the beam. In this study, the monitoring process was optimized by constructing a new computer-controlled measuring machine that limits the test beam to wavelengths reported to be specific for phototaxis and by choosing an algal strain, which does not need background illumination between test light cycles for proper expression of the rhythm. As a result, period and phase of the rhythm are now unaffected by the time a culture is placed into the machine. Analysis of the rhythm data was also optimized through a new algorithm, whose robustness was demonstrated using virtual rhythms with various noises. The algorithm differs in particular from other reported algorithms by maximizing the fit of the data to a sinusoidal curve that dampens exponentially. The algorithm was also used to confirm the reproducibility of rhythm monitoring by the machine. Machine and algorithm can now be used for a multitude of circadian clock studies that require unambiguous period and phase determinations such as light pulse experiments to identify the photoreceptor(s) that reset the circadian clock in C. reinhardtii. PMID:20116270

  8. The Involvement of hybrid cluster protein 4, HCP4, in Anaerobic Metabolism in Chlamydomonas reinhardtii.

    PubMed

    Olson, Adam C; Carter, Clay J

    2016-01-01

    The unicellular green algae Chlamydomonas reinhardtii has long been studied for its unique fermentation pathways and has been evaluated as a candidate organism for biofuel production. Fermentation in C. reinhardtii is facilitated by a network of three predominant pathways producing four major byproducts: formate, ethanol, acetate and hydrogen. Previous microarray studies identified many genes as being highly up-regulated during anaerobiosis. For example, hybrid cluster protein 4 (HCP4) was found to be one of the most highly up-regulated genes under anoxic conditions. Hybrid cluster proteins have long been studied for their unique spectroscopic properties, yet their biological functions remain largely unclear. To probe its role during anaerobiosis, HCP4 was silenced using artificial microRNAs (ami-hcp4) followed by extensive phenotypic analyses of cells grown under anoxic conditions. Both the expression of key fermentative enzymes and their respective metabolites were significantly altered in ami-hcp4, with nitrogen uptake from the media also being significantly different than wild-type cells. The results strongly suggest a role for HCP4 in regulating key fermentative and nitrogen utilization pathways. PMID:26930496

  9. An organelle K+ channel is required for osmoregulation in Chlamydomonas reinhardtii.

    PubMed

    Xu, Feifei; Wu, Xiaoan; Jiang, Lin-Hua; Zhao, Hucheng; Pan, Junmin

    2016-08-01

    Fresh water protozoa and algae face hypotonic challenges in their living environment. Many of them employ a contractile vacuole system to uptake excessive water from the cytoplasm and expel it to the environment to achieve cellular homeostasis. K(+), a major osmolyte in contractile vacuole, is predicted to create higher osmolarity for water influx. Molecular mechanisms for K(+) permeation through the plasma membrane have been well studied. However, how K(+) permeates organelles such as the contractile vacuole is not clear. Here, we show that the six-transmembrane K(+) channel KCN11 in Chlamydomonas is exclusively localized to contractile vacuole. Ectopic expression of KCN11 in HEK293T cells results in voltage-gated K(+) channel activity. Disruption of the gene or mutation of key residues for K(+) permeability of the channel leads to dysfunction of cell osmoregulation in very hypotonic conditions. The contractile cycle is inhibited in the mutant cells with a slower rate of contractile vacuole swelling, leading to cell death. These data demonstrate a new role for six-transmembrane K(+) channels in contractile vacuole functioning and provide further insights into osmoregulation mediated by the contractile vacuole. PMID:27311484

  10. High-resolution crystal structure and redox properties of chloroplastic triosephosphate isomerase from Chlamydomonas reinhardtii.

    PubMed

    Zaffagnini, Mirko; Michelet, Laure; Sciabolini, Chiara; Di Giacinto, Nastasia; Morisse, Samuel; Marchand, Christophe H; Trost, Paolo; Fermani, Simona; Lemaire, Stéphane D

    2014-01-01

    Triosephosphate isomerase (TPI) catalyzes the interconversion of glyceraldehyde-3-phosphate to dihydroxyacetone phosphate. Photosynthetic organisms generally contain two isoforms of TPI located in both cytoplasm and chloroplasts. While the cytoplasmic TPI is involved in the glycolysis, the chloroplastic isoform participates in the Calvin-Benson cycle, a key photosynthetic process responsible for carbon fixation. Compared with its cytoplasmic counterpart, the functional features of chloroplastic TPI have been poorly investigated and its three-dimensional structure has not been solved. Recently, several studies proposed TPI as a potential target of different redox modifications including dithiol/disulfide interchanges, glutathionylation, and nitrosylation. However, neither the effects on protein activity nor the molecular mechanisms underlying these redox modifications have been investigated. Here, we have produced recombinantly and purified TPI from the unicellular green alga Chlamydomonas reinhardtii (Cr). The biochemical properties of the enzyme were delineated and its crystallographic structure was determined at a resolution of 1.1 Å. CrTPI is a homodimer with subunits containing the typical (β/α)8-barrel fold. Although no evidence for TRX regulation was obtained, CrTPI was found to undergo glutathionylation by oxidized glutathione and trans-nitrosylation by nitrosoglutathione, confirming its sensitivity to multiple redox modifications. PMID:24157611

  11. The Involvement of hybrid cluster protein 4, HCP4, in Anaerobic Metabolism in Chlamydomonas reinhardtii

    PubMed Central

    Olson, Adam C.; Carter, Clay J.

    2016-01-01

    The unicellular green algae Chlamydomonas reinhardtii has long been studied for its unique fermentation pathways and has been evaluated as a candidate organism for biofuel production. Fermentation in C. reinhardtii is facilitated by a network of three predominant pathways producing four major byproducts: formate, ethanol, acetate and hydrogen. Previous microarray studies identified many genes as being highly up-regulated during anaerobiosis. For example, hybrid cluster protein 4 (HCP4) was found to be one of the most highly up-regulated genes under anoxic conditions. Hybrid cluster proteins have long been studied for their unique spectroscopic properties, yet their biological functions remain largely unclear. To probe its role during anaerobiosis, HCP4 was silenced using artificial microRNAs (ami-hcp4) followed by extensive phenotypic analyses of cells grown under anoxic conditions. Both the expression of key fermentative enzymes and their respective metabolites were significantly altered in ami-hcp4, with nitrogen uptake from the media also being significantly different than wild-type cells. The results strongly suggest a role for HCP4 in regulating key fermentative and nitrogen utilization pathways. PMID:26930496

  12. Evidence for phenotypic plasticity in the Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241.

    PubMed

    Pocock, Tessa; Vetterli, Adrien; Falk, Stefan

    2011-01-01

    Life in extreme environments poses unique challenges to photosynthetic organisms. The ability for an extremophilic green alga and its genetic and mesophilic equivalent to acclimate to changes in their environment was examined to determine the extent of their phenotypic plasticities. The Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241 (UWO) was isolated from an ice-covered lake in Antarctica, whereas its mesophilic counterpart C. raudensis Ettl. SAG 49.72 (SAG) was isolated from a meadow pool in the Czech Republic. The effects of changes in temperature and salinity on growth, morphology, and photochemistry were examined in the two strains. Differential acclimative responses were observed in UWO which include a wider salinity range for growth, and broader temperature- and salt-induced fluctuations in F(v)/F(m), relative to SAG. Furthermore, the redox state of the photosynthetic electron transport chain, measured as 1-q(P), was modulated in the extremophile whereas this was not observed in the mesophile. Interestingly, it is shown for the first time that SAG is similar to UWO in that it is unable to undergo state transitions. The different natural histories of these two strains exert different evolutionary pressures and, consequently, different abilities for acclimation, an important component of phenotypic plasticity. In contrast to SAG, UWO relied on a redox sensing and signalling system under the growth conditions used in this study. It is proposed that growth and adaptation of UWO under a stressful and extreme environment poises this extremophile for better success under changing environmental conditions. PMID:21041369

  13. Proteomic Analysis of a Fraction with Intact Eyespots of Chlamydomonas reinhardtii and Assignment of Protein Methylation

    PubMed Central

    Eitzinger, Nicole; Wagner, Volker; Weisheit, Wolfram; Geimer, Stefan; Boness, David; Kreimer, Georg; Mittag, Maria

    2015-01-01

    Flagellate green algae possess a visual system, the eyespot. In Chlamydomonas reinhardtii it is situated at the edge of the chloroplast and consists of two carotenoid rich lipid globule layers subtended by thylakoid membranes (TM) that are attached to both chloroplast envelope membranes and a specialized area of the plasma membrane (PM). A former analysis of an eyespot fraction identified 203 proteins. To increase the understanding of eyespot related processes, knowledge of the protein composition of the membranes in its close vicinity is desirable. Here, we present a purification procedure that allows isolation of intact eyespots. This gain in intactness goes, however, hand in hand with an increase of contaminants from other organelles. Proteomic analysis identified 742 proteins. Novel candidates include proteins for eyespot development, retina-related proteins, ion pumps, and membrane-associated proteins, calcium sensing proteins as well as kinases, phosphatases and 14-3-3 proteins. Methylation of proteins at Arg or Lys is known as an important posttranslational modification involved in, e.g., signal transduction. Here, we identify several proteins from eyespot fractions that are methylated at Arg and/or Lys. Among them is the eyespot specific SOUL3 protein that influences the size and position of the eyespot and EYE2, a protein important for its development. PMID:26697039

  14. Evidence for phenotypic plasticity in the Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241

    PubMed Central

    Pocock, Tessa; Vetterli, Adrien; Falk, Stefan

    2011-01-01

    Life in extreme environments poses unique challenges to photosynthetic organisms. The ability for an extremophilic green alga and its genetic and mesophilic equivalent to acclimate to changes in their environment was examined to determine the extent of their phenotypic plasticities. The Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241 (UWO) was isolated from an ice-covered lake in Antarctica, whereas its mesophilic counterpart C. raudensis Ettl. SAG 49.72 (SAG) was isolated from a meadow pool in the Czech Republic. The effects of changes in temperature and salinity on growth, morphology, and photochemistry were examined in the two strains. Differential acclimative responses were observed in UWO which include a wider salinity range for growth, and broader temperature- and salt-induced fluctuations in Fv/Fm, relative to SAG. Furthermore, the redox state of the photosynthetic electron transport chain, measured as 1–qP, was modulated in the extremophile whereas this was not observed in the mesophile. Interestingly, it is shown for the first time that SAG is similar to UWO in that it is unable to undergo state transitions. The different natural histories of these two strains exert different evolutionary pressures and, consequently, different abilities for acclimation, an important component of phenotypic plasticity. In contrast to SAG, UWO relied on a redox sensing and signalling system under the growth conditions used in this study. It is proposed that growth and adaptation of UWO under a stressful and extreme environment poises this extremophile for better success under changing environmental conditions. PMID:21041369

  15. Stable nuclear transformation of Chlamydomonas reinhardtii by using a C. reinhardtii gene as the selectable marker.

    PubMed Central

    Mayfield, S P; Kindle, K L

    1990-01-01

    We have developed a stable nuclear transformation system for the unicellular green alga Chlamydomonas reinhardtii. Transformation was accomplished by introducing the cloned C. reinhardtii oxygen-evolving enhancer protein 1 (OEE1) gene into C. reinhardtii cells by bombardment with DNA-coated tungsten particles. The recipient strain was an OEE1-deficient, nonphotosynthetic, acetate-requiring mutant, which recovered photosynthetic competence after transformation, and was therefore able to grow in the absence of acetate. Analysis of several transformants indicates that transformation has proceeded via second-site integration of the cloned gene, leaving the endogenous mutant gene intact. In genetic crosses of transformants with wild type, both mutant and wild-type phenotypes were recovered, showing that the photosynthetic competence of transformants was due not to reversion of the original locus but rather to expression of the introduced gene. We suggest that the success of the present system is largely due to using a homologous C. reinhardtii gene, leading to stable maintenance and expression of the gene. Transformation with heterologous genes may be problematic because of poor expression due to an unusual codon bias in C. reinhardtii. Images PMID:2179948

  16. Alga-produced cholera toxin-Pfs25 fusion proteins as oral vaccines.

    PubMed

    Gregory, James A; Topol, Aaron B; Doerner, David Z; Mayfield, Stephen

    2013-07-01

    Infectious diseases disproportionately affect indigent regions and are the greatest cause of childhood mortality in developing countries. Practical, low-cost vaccines for use in these countries are paramount to reducing disease burdens and concomitant poverty. Algae are a promising low-cost system for producing vaccines that can be orally delivered, thereby avoiding expensive purification and injectable delivery. We engineered the chloroplast of the eukaryotic alga Chlamydomonas reinhardtii to produce a chimeric protein consisting of the 25-kDa Plasmodium falciparum surface protein (Pfs25) fused to the β subunit of the cholera toxin (CtxB) to investigate an alga-based whole-cell oral vaccine. Pfs25 is a promising malaria transmission-blocking vaccine candidate that has been difficult to produce in traditional recombinant systems due to its structurally complex tandem repeats of epidermal growth factor-like domains. The noncatalytic CtxB domain of the cholera holotoxin assembles into a pentameric structure and acts as a mucosal adjuvant by binding GM1 ganglioside receptors on gut epithelial cells. We demonstrate that CtxB-Pfs25 accumulates as a soluble, properly folded and functional protein within algal chloroplasts, and it is stable in freeze-dried alga cells at ambient temperatures. In mice, oral vaccination using freeze-dried algae that produce CtxB-Pfs25 elicited CtxB-specific serum IgG antibodies and both CtxB- and Pfs25-specific secretory IgA antibodies. These data suggest that algae are a promising system for production and oral delivery of vaccine antigens, but as an orally delivered adjuvant, CtxB is best suited for eliciting secretory IgA antibodies for vaccine antigens against pathogens that invade mucosal surfaces using this strategy. PMID:23603678

  17. Manganese encrustation of zygospores of a chlamydomonas (chlorophyta: volvocales).

    PubMed

    Schulz-Baldes, M; Lewin, R A

    1975-06-13

    In media containing normal trace-element supplements, but not in manganese-deficient media, zygospores of a new species of Chlamydomonas (isolated from soil) become encrusted with a dark brown mineral coating. Staining with benzidine indicates that the encrustation is rich in manganese. This has been confirmed by x-ray analysis in combination with a scanning electron microscope. PMID:17798436

  18. The uni chromosome of Chlamydomonas: histone genes and nucleosome structure.

    PubMed

    Walther, Z; Hall, J L

    1995-09-25

    The uni linkage group (ULG) of Chlamydomonas reinhardtii contains many genes involved in the basal body-flagellar system. Recent evidence suggests that the corresponding uni chromosome is located in close proximity to the basal body complex. In the course of studies into its molecular organization, we have found a cluster of four histone genes on the ULG. The genes are arranged as divergently-transcribed pairs: H3-H4 and H2B-H2A. Genomic sequencing reveals that these genes lack introns and contain characteristic 3' palindromes similar to those of animals. The predicted amino acid sequences are highly conserved across species, with greatest similarities to the histone genes of Volvox. Southern analysis shows that each histone gene is present in 15-20 copies in Chlamydomonas and suggests a dispersed genomic organization. Northern analysis of mitotically-synchronized cells shows that, like the replication-dependent histones of higher eukaryotes, Chlamydomonas histone genes are expressed during S-phase. Using a gene-specific probe on Northern blots, we provide evidence that the ULG H4 gene is regulated in the same manner as other Chlamydomonas histone genes. Finally, micrococcal nuclease protection experiments show that the uni chromosome itself associates with histone proteins and displays a conventional nucleosomal banding pattern. PMID:7479007

  19. A Transient Receptor Potential Ion Channel in Chlamydomonas Shares Key Features with Sensory Transduction-Associated TRP Channels in Mammals

    PubMed Central

    Arias-Darraz, Luis; Cabezas, Deny; Colenso, Charlotte K.; Alegría-Arcos, Melissa; Bravo-Moraga, Felipe; Varas-Concha, Ignacio; Almonacid, Daniel E.; Madrid, Rodolfo; Brauchi, Sebastian

    2015-01-01

    Sensory modalities are essential for navigating through an ever-changing environment. From insects to mammals, transient receptor potential (TRP) channels are known mediators for cellular sensing. Chlamydomonas reinhardtii is a motile single-celled freshwater green alga that is guided by photosensory, mechanosensory, and chemosensory cues. In this type of alga, sensory input is first detected by membrane receptors located in the cell body and then transduced to the beating cilia by membrane depolarization. Although TRP channels seem to be absent in plants, C. reinhardtii possesses genomic sequences encoding TRP proteins. Here, we describe the cloning and characterization of a C. reinhardtii version of a TRP channel sharing key features present in mammalian TRP channels associated with sensory transduction. In silico sequence-structure analysis unveiled the modular design of TRP channels, and electrophysiological experiments conducted on Human Embryonic Kidney-293T cells expressing the Cr-TRP1 clone showed that many of the core functional features of metazoan TRP channels are present in Cr-TRP1, suggesting that basic TRP channel gating characteristics evolved early in the history of eukaryotes. PMID:25595824

  20. Functional analysis of three type-2 DGAT homologue genes for triacylglycerol production in the green microalga Chlamydomonas reinhardtii.

    PubMed

    La Russa, M; Bogen, C; Uhmeyer, A; Doebbe, A; Filippone, E; Kruse, O; Mussgnug, J H

    2012-11-30

    Photosynthetic organisms like plants and algae can use sunlight to produce lipids as important metabolic compounds. Plant-derived triacylglycerols (TAGs) are valuable for human and animal nutrition because of their high energy content and are becoming increasingly important for the production of renewable biofuels. Acyl-CoA:diacylglycerol acyltransferases (DGATs) have been demonstrated to play an important role in the accumulation of TAG compounds in higher plants. DGAT homologue genes have been identified in the genome of the green alga Chlamydomonas reinhardtii, however their function in vivo is still unknown. In this work, the three most promising type-2 DGAT candidate genes potentially involved in TAG lipid accumulation (CrDGAT2a, b and c) were investigated by constructing overexpression strains. For each of the genes, three strains were identified which showed enhanced mRNA levels of between 1.7 and 29.1 times that of the wild type (wt). Total lipid contents, neutral lipids and fatty acid profiles were determined and showed that an enhanced mRNA expression level of the investigated DGAT genes did not boost the intracellular TAG accumulation or resulted in alterations of the fatty acid profiles compared to wild type during standard growth condition or during nitrogen or sulfur stress conditions. We conclude that biotechnological efforts to enhance cellular TAG amount in microalgae need further insights into the complex network of lipid biosynthesis to identify potential bottlenecks of neutral lipid production. PMID:22542934

  1. Two Chlamydomonas OPR proteins stabilize chloroplast mRNAs encoding small subunits of photosystem II and cytochrome b6 f.

    PubMed

    Wang, Fei; Johnson, Xenie; Cavaiuolo, Marina; Bohne, Alexandra-Viola; Nickelsen, Joerg; Vallon, Olivier

    2015-06-01

    In plants and algae, chloroplast gene expression is controlled by nucleus-encoded proteins that bind to mRNAs in a specific manner, stabilizing mRNAs or promoting their splicing, editing, or translation. Here, we present the characterization of two mRNA stabilization factors of the green alga Chlamydomonas reinhardtii, which both belong to the OctotricoPeptide Repeat (OPR) family. MCG1 is necessary to stabilize the petG mRNA, encoding a small subunit of the cytochrome b6 f complex, while MBI1 stabilizes the psbI mRNA, coding for a small subunit of photosystem II. In the mcg1 mutant, the small RNA footprint corresponding to the 5'-end of the petG transcript is reduced in abundance. In both cases, the absence of the small subunit perturbs assembly of the cognate complex. Whereas PetG is essential for formation of a functional cytochrome b6 f dimer, PsbI appears partly dispensable as a low level of PSII activity can still be measured in its absence. Thus, nuclear control of chloroplast gene expression is not only exerted on the major core subunits of the complexes, but also on small subunits with a single transmembrane helix. While OPR proteins have thus far been involved in translation or trans-splicing of plastid mRNAs, our results expand the potential roles of this repeat family to their stabilization. PMID:25898982

  2. Profiling Chlamydomonas metabolism under dark, anoxic H2-producing conditions using a combined proteomic, transcriptomic, and metabolomic approach.

    PubMed

    Subramanian, Venkataramanan; Dubini, Alexandra; Astling, David P; Laurens, Lieve M L; Old, William M; Grossman, Arthur R; Posewitz, Matthew C; Seibert, Michael

    2014-12-01

    Chlamydomonas reinhardtii is well adapted to survive under different environmental conditions due to the unique flexibility of its metabolism. Here we report metabolic pathways that are active during acclimation to anoxia, but were previously not thoroughly studied under dark, anoxic H2-producing conditions in this model green alga. Proteomic analyses, using 2D-differential in-gel electrophoresis in combination with shotgun mass fingerprinting, revealed increased levels of proteins involved in the glycolytic pathway downstream of 3-phosphoglycerate, the glyoxylate pathway, and steps of the tricarboxylic acid (TCA) reactions. Upregulation of the enzyme, isocitrate lyase (ICL), was observed, which was accompanied by increased intracellular succinate levels, suggesting the functioning of glyoxylate pathway reactions. The ICL-inhibitor study revealed presence of reverse TCA reactions under these conditions. Contributions of the serine-isocitrate lyase pathway, glycine cleavage system, and c1-THF/serine hydroxymethyltransferase pathway in the acclimation to dark anoxia were found. We also observed increased levels of amino acids (AAs) suggesting nitrogen reorganization in the form of de novo AA biosynthesis during anoxia. Overall, novel routes for reductant utilization, in combination with redistribution of carbon and nitrogen, are used by this alga during acclimation to O2 deprivation in the dark. PMID:25333711

  3. LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells.

    PubMed

    Dinc, Emine; Tian, Lijin; Roy, Laura M; Roth, Robyn; Goodenough, Ursula; Croce, Roberta

    2016-07-01

    To avoid photodamage, photosynthetic organisms are able to thermally dissipate the energy absorbed in excess in a process known as nonphotochemical quenching (NPQ). Although NPQ has been studied extensively, the major players and the mechanism of quenching remain debated. This is a result of the difficulty in extracting molecular information from in vivo experiments and the absence of a validation system for in vitro experiments. Here, we have created a minimal cell of the green alga Chlamydomonas reinhardtii that is able to undergo NPQ. We show that LHCII, the main light harvesting complex of algae, cannot switch to a quenched conformation in response to pH changes by itself. Instead, a small amount of the protein LHCSR1 (light-harvesting complex stress related 1) is able to induce a large, fast, and reversible pH-dependent quenching in an LHCII-containing membrane. These results strongly suggest that LHCSR1 acts as pH sensor and that it modulates the excited state lifetimes of a large array of LHCII, also explaining the NPQ observed in the LHCSR3-less mutant. The possible quenching mechanisms are discussed. PMID:27335457

  4. Proteomic Analysis of the Eyespot of Chlamydomonas reinhardtii Provides Novel Insights into Its Components and Tactic Movements[W

    PubMed Central

    Schmidt, Melanie; Geßner, Gunther; Luff, Matthias; Heiland, Ines; Wagner, Volker; Kaminski, Marc; Geimer, Stefan; Eitzinger, Nicole; Reißenweber, Tobias; Voytsekh, Olga; Fiedler, Monika; Mittag, Maria; Kreimer, Georg

    2006-01-01

    Flagellate green algae have developed a visual system, the eyespot apparatus, which allows the cell to phototax. To further understand the molecular organization of the eyespot apparatus and the phototactic movement that is controlled by light and the circadian clock, a detailed understanding of all components of the eyespot apparatus is needed. We developed a procedure to purify the eyespot apparatus from the green model alga Chlamydomonas reinhardtii. Its proteomic analysis resulted in the identification of 202 different proteins with at least two different peptides (984 in total). These data provide new insights into structural components of the eyespot apparatus, photoreceptors, retina(l)-related proteins, members of putative signaling pathways for phototaxis and chemotaxis, and metabolic pathways within an algal visual system. In addition, we have performed a functional analysis of one of the identified putative components of the phototactic signaling pathway, casein kinase 1 (CK1). CK1 is also present in the flagella and thus is a promising candidate for controlling behavioral responses to light. We demonstrate that silencing CK1 by RNA interference reduces its level in both flagella and eyespot. In addition, we show that silencing of CK1 results in severe disturbances in hatching, flagellum formation, and circadian control of phototaxis. PMID:16798888

  5. Miocene Coralline algae

    SciTech Connect

    Bosence, D.W.J.

    1988-01-01

    The coralline algae (Order Corallinales) were sedimentologically and ecologically important during the Miocene, a period when they were particularly abundant. The many poorly described and illustrated species and the lack of quantitative data in coralline thalli make specific determinations particularly difficult, but some species are well known and widespread in the Tethyan area. The sedimentologic importance of the Miocene coralline algae is reflected in the abundance of in-situ coralline buildups, rhodoliths, and coralline debris facies at Malta and Spain; similar sequences are known throughout the Tethyan Miocene. In-situ buildups vary from leafy crustose biostromes to walled reefs with dense coralline crusts and branches. Growth forms are apparently related to hydraulic energy. Rhodoliths vary from leafy, crustose, and open-branched forms in muddy sediments to dense, crustose, and radial-branching forms in coarse grainstones. Rhodolith form and internal structure correlate closely with hydraulic energy. Coralline genera are conservative and, as such, are useful in paleoenvironmental analysis. Of particular interest are the restricted depth ranges of recent coralline genera. More research is needed on the sedimentology, paleoecology, and systematics of the Cenozoic corallines, as they have particular value in paleoenvironmental analysis.

  6. Comparative sensitivity of five species of macrophytes and six species of algae to atrazine, metribuzin, alachlor, and metolachlor

    USGS Publications Warehouse

    Fairchild, J.F.; Ruessler, D.S.; Carlson, A.R.

    1998-01-01

    This study determined the relative sensitivity of five species of aquatic macrophytes and six species of algae to four commonly used herbicides (atrazine, metribuzin, alachlor, and metolachlor). Toxicity tests consisted of 96-h (duckweed and algae) or 14-d (submerged macrophytes) static exposures. The triazine herbicides (atrazine and metribuzin) were significantly more toxic to aquatic plants than were the acetanilide herbicides (alachlor and metolachlor). Toxicity studies ranked metribuzin > atrazine > alachlor > metolachlor in decreasing order of overall toxicity to aquatic plants. Relative sensitivities of macrophytes to these herbicides decreased in the order of Ceratophyllum > Najas > Elodea > Lemna > Myriophyllum. Relative sensitivities of algae to herbicides decreased in the order of Selenastrum > Chlorella > Chlamydomonas > Microcystis > Scenedesmus > Anabaena. Algae and macrophytes were of similar overall sensitivities to herbicides. Data indicated that Selenastrum, a commonly tested green alga, was generally more sensitive compared to other plant species. Lemna minor, a commonly tested floating vascular plant, was of intermediate sensitivity, and was fivefold less sensitive than Ceratophyllum, which was the most sensitive species tested. The results indicated that no species was consistently most sensitive, and that a suite of aquatic plant test species may be needed to perform accurate risk assessments of herbicides.

  7. Cellular Auxin Transport in Algae

    PubMed Central

    Zhang, Suyun; van Duijn, Bert

    2014-01-01

    The phytohormone auxin is one of the main directors of plant growth and development. In higher plants, auxin is generated in apical plant parts and transported from cell-to-cell in a polar fashion. Auxin is present in all plant phyla, and the existence of polar auxin transport (PAT) is well established in land plants. Algae are a group of relatively simple, autotrophic, photosynthetic organisms that share many features with land plants. In particular, Charophyceae (a taxon of green algae) are closest ancestors of land plants. In the study of auxin function, transport and its evolution, the algae form an interesting research target. Recently, proof for polar auxin transport in Chara species was published and auxin related research in algae gained more attention. In this review we discuss auxin transport in algae with respect to land plants and suggest directions for future studies. PMID:27135491

  8. Cellular Auxin Transport in Algae.

    PubMed

    Zhang, Suyun; van Duijn, Bert

    2014-01-01

    The phytohormone auxin is one of the main directors of plant growth and development. In higher plants, auxin is generated in apical plant parts and transported from cell-to-cell in a polar fashion. Auxin is present in all plant phyla, and the existence of polar auxin transport (PAT) is well established in land plants. Algae are a group of relatively simple, autotrophic, photosynthetic organisms that share many features with land plants. In particular, Charophyceae (a taxon of green algae) are closest ancestors of land plants. In the study of auxin function, transport and its evolution, the algae form an interesting research target. Recently, proof for polar auxin transport in Chara species was published and auxin related research in algae gained more attention. In this review we discuss auxin transport in algae with respect to land plants and suggest directions for future studies. PMID:27135491

  9. Respiratory Chain of Colorless Algae II. Cyanophyta

    PubMed Central

    Webster, D. A.; Hackett, D. P.

    1966-01-01

    Whole cell difference spectra of the blue-green algae, Saprospira grandis, Leucothrix mucor, and Vitreoscilla sp. have one, or at the most 2, broad α-bands near 560 mμ. At −190° these bands split to give 4 peaks in the α-region for b and c-type cytochromes, but no α-band for a-type cytochromes is visible. The NADH oxidase activity of these organisms was shown to be associated with particulate fractions of cell homogenates. The response of this activity to inhibitors differed from the responses of the NADH oxidase activities of particulate preparations from the green algae and higher plants to the same inhibitors, but is more typical of certain bacteria. No cytochrome oxidase activity was present in these preparations. The respiration of Saprospira and Vitreoscilla can be light-reversibly inhibited by CO, and all 3 organisms have a CO-binding pigment whose CO complex absorbs near 570, 535, and 417 mμ. The action spectrum for the light reversal of CO-inhibited Vitreoscilla respiration shows maxima at 568, 534, and 416 mμ. The results suggest that the terminal oxidase in these blue-greens is an o-type cytochrome. Images PMID:5932404

  10. Omics in Chlamydomonas for Biofuel Production.

    PubMed

    Aucoin, Hanna R; Gardner, Joseph; Boyle, Nanette R

    2016-01-01

    In response to demands for sustainable domestic fuel sources, research into biofuels has become increasingly important. Many challenges face biofuels in their effort to replace petroleum fuels, but rational strain engineering of algae and photosynthetic organisms offers a great deal of promise. For decades, mutations and stress responses in photosynthetic microbiota were seen to result in production of exciting high-energy fuel molecules, giving hope but minor capability for design. However, '-omics' techniques for visualizing entire cell processing has clarified biosynthesis and regulatory networks. Investigation into the promising production behaviors of the model organism C. reinhardtii and its mutants with these powerful techniques has improved predictability and understanding of the diverse, complex interactions within photosynthetic organisms. This new equipment has created an exciting new frontier for high-throughput, predictable engineering of photosynthetically produced carbon-neutral biofuels. PMID:27023246

  11. Evaluation of the contamination of marine algae (seaweed) from the St. Lawrence River and likely to be consumed by humans

    SciTech Connect

    Phaneuf, D.; Cote, I.; Dumas, P.; Ferron, L.A.; LeBlanc, A.

    1999-02-01

    The goal of the study was to assess the contamination of marine algae (seaweeds) growing in the St. Lawrence River estuary and Gulf of St. Lawrence and to evaluate the risks to human health from the consumption of these algae. Algae were collected by hand at low tide. A total of 10 sites on the north and south shores of the St. Lawrence as well as in Baie des Chaleurs were sampled. The most frequently collected species of algae were Fucus vesiculosus, Ascophyllum nodosum, Laminaria Longicruris, Palmaria palmata, Ulva lactuca, and Fucus distichus. Alga samples were analyzed for metals iodine, and organochlorines. A risk assessment was performed using risk factors. In general, concentrations in St. Lawrence algae were not very high. Consequently, health risks associated with these compounds in St. Lawrence algae were very low. Iodine concentration, on the other hand, could be of concern with regard to human health. Regular consumption of algae, especially of Laminaria sp., could result in levels of iodine sufficient to cause thyroid problems. For regular consumers, it would be preferable to choose species with low iodine concentrations, such as U. lactuca and P. palmata, in order to prevent potential problems. Furthermore, it would also be important to assess whether preparation for consumption or cooking affects the iodine content of algae. Algae consumption may also have beneficial health effects. Scientific literature has shown that it is a good source of fiber and vitamins, especially vitamin B{sub 12}.

  12. Nucleotide diversity of the colorless green alga Polytomella parva (Chlorophyceae, Chlorophyta): high for the mitochondrial telomeres, surprisingly low everywhere else.

    PubMed

    Smith, David Roy; Lee, Robert W

    2011-01-01

    Silent-site nucleotide diversity data (π(silent)) can provide insights into the forces driving genome evolution. Here we present π(silent) statistics for the mitochondrial and nuclear DNAs of Polytomella parva, a nonphotosynthetic green alga with a highly reduced, linear fragmented mitochondrial genome. We show that this species harbors very little genetic diversity, with the exception of the mitochondrial telomeres, which have an excess of polymorphic sites. These data are compared with previously published π(silent) values from the mitochondrial and nuclear genomes of the model species Chlamydomonas reinhardtii and Volvox carteri, which are close relatives of P. parva, and are used to understand the modes and tempos of genome evolution within green algae. PMID:21762422

  13. Ecology of Harmful Algae

    NASA Astrophysics Data System (ADS)

    Roelke, Daniel L.

    2007-07-01

    Edna Graneli and Jefferson T. Turner, Editors;Ecological Studies Series, Vol. 189; Springer; ISBN 3540322094; 413 pp.; 2006; $195 Harmful algal blooms (HABs) affect commercially and recreationally important species, human health, and ecosystem functioning. Hallmark events are the visually stunning blooms where waters are discolored and filled with ichthyotoxin-producing algae that lead to large fish kills. Of most concern, however, are HABs that pose a threat to human health. For example, some phycotoxins bioaccumulate in the guts and tissues of commercially and recreationally important species that when consumed by humans, may result in nausea, paralysis, memory loss, and even death. In addition to the deleterious impacts of phycotoxins, HABs can be problematic in other ways. For example, the decay of blooms often leads to low dissolved oxygen in subsurface waters. Blooms also reduce light penetration into the water column. Both processes disrupt ecosystems and in some cases have completely destroyed benthic communities.

  14. The effects of barley straw (Hordeum vulgare) on the growth of freshwater algae.

    PubMed

    Ferrier, M D; Butler, B R; Terlizzi, D E; Lacouture, R V

    2005-11-01

    Bioassays were conducted to determine the efficacy of barley straw liquor in controlling algal growth of 12 freshwater species of algae representing three divisions. Barley straw liquor inhibited the growth of three nuisance algae common in freshwater: Synura petersenii, Dinobyron sp., and Microcystis aeruginosa. However, Selenastrum capricornutum, Spirogyra sp., Oscillatoria lutea var. contorta, and Navicula sp. had significantly increased growth in the presence of straw liquor. The growth of the remainder, Ulothrix fimbriata, Scenedesmus quadricauda, Chlorella vulgaris, Anabaena flos-aquae, and Synedra sp. showed no significant difference from controls. In a related field study, we treated four of six ponds with barley straw and monitored their chlorophyll a levels for one growing season. While phytoplankton populations in all ponds decreased in midsummer, the phytoplankton biomass in treated ponds did not differ significantly from that of control ponds, suggesting that the application of barley straw had no effect on algal growth in these systems. PMID:16051085

  15. Differential thermal effects on the energy distribution between photosystem II and photosystem I in thylakoid membranes of a psychrophilic and a mesophilic alga.

    PubMed

    Morgan-Kiss, Rachael; Ivanov, Alexander G; Williams, John; Mobashsher Khan; Huner, Norman P A

    2002-04-12

    Sensitivity of the photosynthetic thylakoid membranes to thermal stress was investigated in the psychrophilic Antarctic alga Chlamydomonas subcaudata. C. subcaudata thylakoids exhibited an elevated heat sensitivity as indicated by a temperature-induced rise in F(o) fluorescence in comparison with the mesophilic species, Chlamydomonas reinhardtii. This was accompanied by a loss of structural stability of the photosystem (PS) II core complex and functional changes at the level of PSI in C. reinhardtii, but not in C. subcaudata. Lastly, C. subcaudata exhibited an increase in unsaturated fatty acid content of membrane lipids in combination with unique fatty acid species. The relationship between lipid unsaturation and the functioning of the photosynthetic apparatus under elevated temperatures is discussed. PMID:11997125

  16. Platinum anniversary: virus and lichen alga together more than 70 years.

    PubMed

    Petrzik, Karel; Vondrák, Jan; Kvíderová, Jana; Lukavský, Jaromír

    2015-01-01

    Trebouxia aggregata (Archibald) Gärtner (phylum Chlorophyta, family Trebouxiaceae), a lichen symbiotic alga, has been identified as host of the well-known herbaceous plant virus Cauliflower mosaic virus (CaMV, family Caulimoviridae). The alga had been isolated from Xanthoria parietina more than 70 years ago and has been maintained in a collection since that time. The CaMV detected in this collection entry has now been completely sequenced. The virus from T. aggregata is mechanically transmissible to a herbaceous host and induces disease symptoms there. Its genome differs by 173 nt from the closest European CaMV-D/H isolate from cauliflower. No site under positive selection was found on the CaMV genome from T. aggregata. We therefore assume that the virus's presence in this alga was not sufficiently long to fix any specific changes in its genome. Apart from this symbiotic alga, CaMV capsid protein sequences were amplified from many other non-symbiotic algae species maintained in a collection (e.g., Oonephris obesa, Elliptochloris sp., Microthamnion kuetzingianum, Chlorella vulgaris, Pseudococcomyxa sp.). CaMV-free Chlorella vulgaris was treated with CaMV to establish virus infection. The virus was still detected there after five passages. The virus infection is morphologically symptomless on Chlorella algae and the photosynthesis activity is slightly decreased in comparison to CaMV-free alga culture. This is the first proof as to the natural presence of CaMV in algae and the first demonstration of algae being artificially infected with this virus. PMID:25789995

  17. Platinum Anniversary: Virus and Lichen Alga Together More than 70 Years

    PubMed Central

    Petrzik, Karel; Vondrák, Jan; Kvíderová, Jana; Lukavský, Jaromír

    2015-01-01

    Trebouxia aggregata (Archibald) Gärtner (phylum Chlorophyta, family Trebouxiaceae), a lichen symbiotic alga, has been identified as host of the well-known herbaceous plant virus Cauliflower mosaic virus (CaMV, family Caulimoviridae). The alga had been isolated from Xanthoria parietina more than 70 years ago and has been maintained in a collection since that time. The CaMV detected in this collection entry has now been completely sequenced. The virus from T. aggregata is mechanically transmissible to a herbaceous host and induces disease symptoms there. Its genome differs by 173 nt from the closest European CaMV-D/H isolate from cauliflower. No site under positive selection was found on the CaMV genome from T. aggregata. We therefore assume that the virus’s presence in this alga was not sufficiently long to fix any specific changes in its genome. Apart from this symbiotic alga, CaMV capsid protein sequences were amplified from many other non-symbiotic algae species maintained in a collection (e.g., Oonephris obesa, Elliptochloris sp., Microthamnion kuetzingianum, Chlorella vulgaris, Pseudococcomyxa sp.). CaMV-free Chlorella vulgaris was treated with CaMV to establish virus infection. The virus was still detected there after five passages. The virus infection is morphologically symptomless on Chlorella algae and the photosynthesis activity is slightly decreased in comparison to CaMV-free alga culture. This is the first proof as to the natural presence of CaMV in algae and the first demonstration of algae being artificially infected with this virus. PMID:25789995

  18. The small domain of cytochrome f from the psychrophile Chlamydomonas raudensis UWO 241 modulates the apparent molecular mass and decreases the accumulation of cytochrome f in the mesophile Chlamydomonas reinhardtii.

    PubMed

    Gudynaite-Savitch, Loreta; Loiselay, Christelle; Savitch, Leonid V; Simmonds, John; Kohalmi, Susanne E; Choquet, Yves; Hüner, Norman P A

    2007-10-01

    Cytochrome f from the psychrophile Chlamydomonas raudensis UWO 241 has a lower thermostability of its c-type heme and an apparent molecular mass that is 7 kDa lower than that of the model mesophilic green alga Chlamydomonas reinhardtii. We combined chloroplast transformation, site-directed mutagensis, and the creation of chimeric fusion constructs to assess the contribution of specific domains and (or) amino acids residues to the structure, stability, and accumulation of cytochrome f, as well as its function in photosynthetic intersystem electron transport. We demonstrate that differences in the amino acid sequence of the small domain and specific charged amino acids in the large domain of cytochrome f alter the physical properties of this protein but do not affect either the thermostability of the c-type heme, the apparent half-life of cytochrome f in the presence of the chloroplastic protein synthesis inhibitor chloramphenicol, or the capacity for photosynthetic intersystem electron transport, measured as e-/P700. However, pulse-labeling with [14C]acetate, combined with immunoblotting, indicated that the negative autoregulation of cytochrome f accumulation observed in mesophilic C. reinhardtii transformed with chimeric constructs from the psychrophile was likely the result of the defective association of the chimeric forms of cytochrome f with the other subunits of the cytochrome b6/f complex native to the C. reinhardtii wild type. These results are discussed in terms of the unique fatty acid composition of the thylakoid membranes of C. raudensis UWO 241 adapted to cold environments. PMID:17901903

  19. Complexity and idiosyncrasy in the responses of algae to disturbance in mono- and multi-species assemblages.

    PubMed

    Goodsell, P J; Underwood, A J

    2008-09-01

    There is considerable debate about whether stability (e.g. inertia) of an assemblage, or of individuals in an assemblage, is positively associated with the number of species or whether there are idiosyncratic effects of particular species. We assessed the general model that the loss of an individual alga, caused by trampling, is greater in monospecific than in multi-species stands but that the responses of algae are idiosyncratic, depending on the morphology of the species. The experiment was done on conspicuous and dominant algae with different morphology on temperate Australian rocky shores: the fucalean algae Hormosira banksii and Sargassum sp. and the coralline alga Corallina officinalis. We assessed the relative and interactive effects of the extent of trampling (number of paths) and the localised intensity of trampling (number of travels per path) on the three algae. The number of paths trampled (the extent of disturbance) had more impact on each alga than the number of times paths were travelled (the intensity of disturbance). As predicted, H. banksii was most susceptible to trampling at each level than were the coarser algae Sargassum sp. and C. officinalis. There was a consistent trend for each alga to be more inert to trampling when in the presence of the other two species than when in monospecific stands, but this was only statistically significant (P < 0.05) for the softer alga H. banksii. The responses of H. banksii and Sargassum sp. to disturbance seemed, in many cases, to be due to the presence of C. officinalis rather than to "diversity" per se. The relationship between the number of species and stability is complex in intertidal habitats, depending on the species and the combinations of species with which it grows. PMID:18574597

  20. Fuel From Algae: Scaling and Commercialization of Algae Harvesting Technologies

    SciTech Connect

    2010-01-15

    Broad Funding Opportunity Announcement Project: Led by CEO Ross Youngs, AVS has patented a cost-effective dewatering technology that separates micro-solids (algae) from water. Separating micro-solids from water traditionally requires a centrifuge, which uses significant energy to spin the water mass and force materials of different densities to separate from one another. In a comparative analysis, dewatering 1 ton of algae in a centrifuge costs around $3,400. AVS’s Solid-Liquid Separation (SLS) system is less energy-intensive and less expensive, costing $1.92 to process 1 ton of algae. The SLS technology uses capillary dewatering with filter media to gently facilitate water separation, leaving behind dewatered algae which can then be used as a source for biofuels and bio-products. The biomimicry of the SLS technology emulates the way plants absorb and spread water to their capillaries.

  1. [From algae to "functional foods"].

    PubMed

    Vadalà, M; Palmieri, B

    2015-01-01

    In the recent years, a growing interest for nutraceutical algae (tablets, capsules, drops) has been developed, due to their effective health benefits, as a potential alternative to the classic drugs. This review explores the use of cyanobacterium Spirulina, the microalgae Chlorella, Dunaliella, Haematococcus, and the macroalgae Klamath, Ascophyllum, Lithothamnion, Chondrus, Hundaria, Glacilaria, Laminaria, Asparagopsis, Eisenia, Sargassum as nutraceuticals and dietary supplements, in terms of production, nutritional components and evidence-based health benefits. Thus, our specific goals are: 1) Overview of the algae species currently used in nutraceuticals; 2) Description of their characteristics, action mechanisms, and possible side effects; 3) Perspective of specific algae clinical investigations development. PMID:26378764

  2. Transgenic algae engineered for higher performance

    DOEpatents

    Unkefer, Pat J; Anderson, Penelope S; Knight, Thomas J

    2014-10-21

    The present disclosure relates to transgenic algae having increased growth characteristics, and methods of increasing growth characteristics of algae. In particular, the disclosure relates to transgenic algae comprising a glutamine phenylpyruvate transaminase transgene and to transgenic algae comprising a glutamine phenylpyruvate transaminase transgene and a glutamine synthetase.

  3. Characterization of type 2 diacylglycerol acyltransferases in Chlamydomonas reinhardtii reveals their distinct substrate specificities and functions in triacylglycerol biosynthesis.

    PubMed

    Liu, Jin; Han, Danxiang; Yoon, Kangsup; Hu, Qiang; Li, Yantao

    2016-04-01

    Diacylglycerol acyltransferases (DGATs) catalyze a rate-limiting step of triacylglycerol (TAG) biosynthesis in higher plants and yeast. The genome of the green alga Chlamydomonas reinhardtii has multiple genes encoding type 2 DGATs (DGTTs). Here we present detailed functional and biochemical analyses of Chlamydomonas DGTTs. In vitro enzyme analysis using a radiolabel-free assay revealed distinct substrate specificities of three DGTTs: CrDGTT1 preferred polyunsaturated acyl CoAs, CrDGTT2 preferred monounsaturated acyl CoAs, and CrDGTT3 preferred C16 CoAs. When diacylglycerol was used as the substrate, CrDGTT1 preferred C16 over C18 in the sn-2 position of the glycerol backbone, but CrDGTT2 and CrDGTT3 preferred C18 over C16. In vivo knockdown of CrDGTT1, CrDGTT2 or CrDGTT3 resulted in 20-35% decreases in TAG content and a reduction of specific TAG fatty acids, in agreement with the findings of the in vitro assay and fatty acid feeding test. These results demonstrate that CrDGTT1, CrDGTT2 and CrDGTT3 possess distinct specificities toward acyl CoAs and diacylglycerols, and may work in concert spatially and temporally to synthesize diverse TAG species in C. reinhardtii. CrDGTT1 was shown to prefer prokaryotic lipid substrates and probably resides in both the endoplasmic reticulum and chloroplast envelope, indicating its role in prokaryotic and eukaryotic TAG biosynthesis. Based on these findings, we propose a working model for the role of CrDGTT1 in TAG biosynthesis. This work provides insight into TAG biosynthesis in C. reinhardtii, and paves the way for engineering microalgae for production of biofuels and high-value bioproducts. PMID:26919811

  4. Genome-Wide Analysis of Tandem Repeats in Plants and Green Algae

    PubMed Central

    Zhao, Zhixin; Guo, Cheng; Sutharzan, Sreeskandarajan; Li, Pei; Echt, Craig S.; Zhang, Jie; Liang, Chun

    2013-01-01

    Tandem repeats (TRs) extensively exist in the genomes of prokaryotes and eukaryotes. Based on the sequenced genomes and gene annotations of 31 plant and algal species in Phytozome version 8.0 (http://www.phytozome.net/), we examined TRs in a genome-wide scale, characterized their distributions and motif features, and explored their putative biological functions. Among the 31 species, no significant correlation was detected between the TR density and genome size. Interestingly, green alga Chlamydomonas reinhardtii (42,059 bp/Mbp) and castor bean Ricinus communis (55,454 bp/Mbp) showed much higher TR densities than all other species (13,209 bp/Mbp on average). In the 29 land plants, including 22 dicots, 5 monocots, and 2 bryophytes, 5′-UTR and upstream intergenic 200-nt (UI200) regions had the first and second highest TR densities, whereas in the two green algae (C. reinhardtii and Volvox carteri) the first and second highest densities were found in intron and coding sequence (CDS) regions, respectively. In CDS regions, trinucleotide and hexanucleotide motifs were those most frequently represented in all species. In intron regions, especially in the two green algae, significantly more TRs were detected near the intron–exon junctions. Within intergenic regions in dicots and monocots, more TRs were found near both the 5′ and 3′ ends of genes. GO annotation in two green algae revealed that the genes with TRs in introns are significantly involved in transcriptional and translational processing. As the first systematic examination of TRs in plant and green algal genomes, our study showed that TRs displayed nonrandom distribution for both intragenic and intergenic regions, suggesting that they have potential roles in transcriptional or translational regulation in plants and green algae. PMID:24192840

  5. Genome-wide analysis of tandem repeats in plants and green algae.

    PubMed

    Zhao, Zhixin; Guo, Cheng; Sutharzan, Sreeskandarajan; Li, Pei; Echt, Craig S; Zhang, Jie; Liang, Chun

    2014-01-01

    Tandem repeats (TRs) extensively exist in the genomes of prokaryotes and eukaryotes. Based on the sequenced genomes and gene annotations of 31 plant and algal species in Phytozome version 8.0 (http://www.phytozome.net/), we examined TRs in a genome-wide scale, characterized their distributions and motif features, and explored their putative biological functions. Among the 31 species, no significant correlation was detected between the TR density and genome size. Interestingly, green alga Chlamydomonas reinhardtii (42,059 bp/Mbp) and castor bean Ricinus communis (55,454 bp/Mbp) showed much higher TR densities than all other species (13,209 bp/Mbp on average). In the 29 land plants, including 22 dicots, 5 monocots, and 2 bryophytes, 5'-UTR and upstream intergenic 200-nt (UI200) regions had the first and second highest TR densities, whereas in the two green algae (C. reinhardtii and Volvox carteri) the first and second highest densities were found in intron and coding sequence (CDS) regions, respectively. In CDS regions, trinucleotide and hexanucleotide motifs were those most frequently represented in all species. In intron regions, especially in the two green algae, significantly more TRs were detected near the intron-exon junctions. Within intergenic regions in dicots and monocots, more TRs were found near both the 5' and 3' ends of genes. GO annotation in two green algae revealed that the genes with TRs in introns are significantly involved in transcriptional and translational processing. As the first systematic examination of TRs in plant and green algal genomes, our study showed that TRs displayed nonrandom distribution for both intragenic and intergenic regions, suggesting that they have potential roles in transcriptional or translational regulation in plants and green algae. PMID:24192840

  6. Cyanobactericidal effect of Rhodococcus sp. isolated from eutrophic lake on Microcystis sp.

    PubMed

    Lee, Young-Ki; Ahn, Chi-Yong; Kim, Hee-Sik; Oh, Hee-Mock

    2010-11-01

    A bacterium, which was observed in all cultivations of Microcystis sp., was isolated and designated as Rhodococcus sp. KWR2. The growth of bloom-forming cyanobacteria, including four strains of Microcystis aeruginosa and Anabaena variabilis, was suppressed by up to 75-88% by 2% (v/v) culture broth of KWR2 after 5 days. But KWR2 did not inhibit eukaryotic algae, Chlorella vulgaris and Scenedesmus sp. An extracellular algicidal substance produced by KWR2 showed a cyanobactericidal activity of 94% and was water-soluble with a molecular weight of lower than 8 kDa. PMID:20640876

  7. Rapid and simple UPLC-MS/MS method for precise phytochelatin quantification in alga extracts.

    PubMed

    Bräutigam, Anja; Wesenberg, Dirk; Preud'homme, Hugues; Schaumlöffel, Dirk

    2010-09-01

    Quantitative phytochelatin (PC) analysis is, due to oxidation sensitivity of the PCs, matrix effects, and time consuming sample preparation, still a challenging analytical task. In this study, a rapid, simple, and sensitive method for precise determination of native PCs in crude extracts of the green alga Chlamydomonas reinhardtii was developed. Algae were exposed 48 h to 70 μM Cd. Coupling of ultra performance liquid chromatography and electrospray ionization tandem mass spectrometry with multi-reaction mode transitions for detection permitted the required short-time, high-resolution separation and detection specificity. Thus, under optimized chromatographic conditions, 10 thiol peptides were baseline-separated within 7 min. Relative detection limits in the nanomolar range in microliter sample volumes were achieved (corresponding to absolute detection limits at femtomole level). Next to glutathione (GSH), the most abundant cadmium-induced PCs in C. reinhardtii, namely CysGSH, PC(2), PC(3), CysPC(2), and CysPC(3), were quantified with high reproducibility at concentrations between 15 and 198 nmol g(-1) fresh weight. The biological variation of PC synthesis of nine independently grown alga cultures was determined to be on average 13.7%. PMID:20632163

  8. Genomic analysis of organismal complexity in the multicellular green alga Volvox carteri

    SciTech Connect

    Prochnik, Simon E.; Umen, James; Nedelcu, Aurora; Hallmann, Armin; Miller, Stephen M.; Nishii, Ichiro; Ferris, Patrick; Kuo, Alan; Mitros, Therese; Fritz-Laylin, Lillian K.; Hellsten, Uffe; Chapman, Jarrod; Simakov, Oleg; Rensing, Stefan A.; Terry, Astrid; Pangilinan, Jasmyn; Kapitonov, Vladimir; Jurka, Jerzy; Salamov, Asaf; Shapiro, Harris; Schmutz, Jeremy; Grimwood, Jane; Lindquist, Erika; Lucas, Susan; Grigoriev, Igor V.; Schmitt, Rudiger; Kirk, David; Rokhsar, Daniel S.

    2010-07-01

    Analysis of the Volvox carteri genome reveals that this green alga's increased organismal complexity and multicellularity are associated with modifications in protein families shared with its unicellular ancestor, and not with large-scale innovations in protein coding capacity. The multicellular green alga Volvox carteri and its morphologically diverse close relatives (the volvocine algae) are uniquely suited for investigating the evolution of multicellularity and development. We sequenced the 138 Mb genome of V. carteri and compared its {approx}14,500 predicted proteins to those of its unicellular relative, Chlamydomonas reinhardtii. Despite fundamental differences in organismal complexity and life history, the two species have similar protein-coding potentials, and few species-specific protein-coding gene predictions. Interestingly, volvocine algal-specific proteins are enriched in Volvox, including those associated with an expanded and highly compartmentalized extracellular matrix. Our analysis shows that increases in organismal complexity can be associated with modifications of lineage-specific proteins rather than large-scale invention of protein-coding capacity.

  9. Effect of endocrine disrupters on photosystem II energy fluxes of green algae and cyanobacteria.

    PubMed

    Perron, Marie-Claude; Juneau, Philippe

    2011-05-01

    Among the numerous toxics found in the aquatic environment, endocrine disrupters can interfere with the normal functioning of the endocrine system of several organisms, leading to important consequences. Even if algae and cyanobacteria are non-target organisms without endocrine system, our goals were to verify if endocrine disrupters can affect photosynthetic activity and how energy flows through photosystem II (PSII) were altered. To reach these objectives, we exposed, for 15 min, two green algae (Chlamydomonas reinhardtii strain CC125, Pseudokirchneriella subcapitata strain CPCC37) and a toxic and a non-toxic strain of Microcystis aeruginosa (CPCC299 and CPCC632 respectively) to 4-octylphenol, 4-nonylphenol and β-estradiol at concentrations ranging from 0.1 to 5 μg/mL. We have shown for the first time that endocrine disrupters may have drastic effects on PSII energy fluxes. Furthermore, we showed that various species have different sensitivity to endocrine disrupters. P. subcapitata was tolerant to each endocrine disrupter tested, while flows of energy through PSII were affected similarly, but at different extent, for the other species. Cyanobacterial PSII energy fluxes were more affected than green algae, suggesting that the prokaryotic characteristics of these organisms are responsible of their high sensitivity. PMID:21439565

  10. Assimilation efficiency of organic contaminants from algae by the zebra mussel, Dreissena polymorpha

    SciTech Connect

    Goldenstein, T.A.; Bruner, K.A.; Fisher, S.W.; Landrum, P.F.

    1995-12-31

    A high percent of hydrophobic contaminants in the Great Lakes are particulate bound. Due to large populations and its high filtering capacity, the zebra mussel, Dreissena polymorpha, has the potential to re-direct contaminants from the water column by removal of contaminated particles, including algae. Throughout a season, zebra mussels feed on a variety of algal species. To determine if there are algal species differences in assimilation efficiency of contaminants, the percent assimilation efficiency (%AE) of three PCB congeners and DDE from three algae species were investigated using pulse-chase methodology. Results suggest no species difference in %AE for hexachlorobiphenyl (HCBP) from the algae Chlorella vulgaris and Chlamydomonas rheinhardtii. The mean %AE of HCBP from C. vulgaris was 60.9 (SE = {+-} 4.1), as compared to 68.6 (SE = {+-} 2.9) from C. rheinhardtii. Results from additional compounds and algal species will be discussed. The results of this study will allow them to refine the mechanism of contaminant uptake in aquatic filter feeders and assess the effect of zebra mussels on contaminant cycling in the Great lakes.

  11. Salicylhydroxamic acid (SHAM) inhibition of the DIC-pump in unicellular algae

    SciTech Connect

    Goyal, A.; Tolbert, N.E. )

    1989-04-01

    SHAM at 1 or 2 mM inhibits dissolved inorganic carbon (DIC) concentrating mechanisms in unicellular green algae as measured by photosynthetic oxygen evolution or by {sup 14}C-inorganic carbon uptake (using silicone oil centrifugation techniques). This inhibition was reversed by high levels of DIC whereby the cells do not require the concentrating mechanism. SHAM inhibited the DIC-pump, which uses external CO{sub 2}, in three species of algae, Dunaliella tertiolecta, Chlamydomonas reinhardtii, and Scenedesmus obliquus when adapted to low CO{sub 2} and assayed around neutral pH. Scenedesmus adapted to air at pH 9.0 to use external HCO{sub 3}{sup {minus}} were not affected by SHAM. It is important to establish low optimum concentrations of SHAM, which varied with the algal species. The mechanism of SHAM inhibition of the CO{sub 2} concentrating process is unknown. SHAM inhibits alternative respiration in these algae, but SHAM may also inhibit other reactions involving H{sup +} gradients or transporters associated with the DIC-pump.

  12. Photosynthesis and photorespiration in algae.

    PubMed

    Lloyd, N D; Canvin, D T; Culver, D A

    1977-05-01

    The CO(2) exchange of several species of fresh water and marine algae was measured in the laboratory to determine whether photorespiration occurs in these organisms. The algae were positioned as thin layers on filter paper and the CO(2) exchange determined in an open gas exchange system. In either 21 or 1% O(2) there was little difference between (14)CO(2) and (12)CO(2) uptake. Apparent photosynthesis was the same in 2, 21, or 50% O(2). The compensation points of all algae were less than 10 mul 1(-1). CO(2) or (14)CO(2) evolution into CO(2)-free air in the light was always less than the corresponding evolution in darkness. These observations are inconsistent with the proposal that photorespiration exists in these algae. PMID:16659972

  13. Algae fuel clean electricity generation

    SciTech Connect

    O'Sullivan, D.

    1993-02-08

    The paper describes plans for a 600-kW pilot generating unit, fueled by diesel and Chlorella, a green alga commonly seen growing on the surface of ponds. The plant contains Biocoil units in which Chlorella are grown using the liquid effluents from sewage treatment plants and dissolved carbon dioxide from exhaust gases from the combustion unit. The algae are partially dried and fed into the combustor where diesel fuel is used to maintain ignition. Diesel fuel is also used for start-up and as a backup fuel for seasonal shifts that affect the algae growing conditions. Since the algae use the carbon dioxide emitted during the combustion process, the process will not contribute to global warming.

  14. Three light-inducible heat shock genes of Chlamydomonas reinhardtii.

    PubMed Central

    von Gromoff, E D; Treier, U; Beck, C F

    1989-01-01

    Genomic clones representing three Chlamydomonas reinhardtii genes homologous to the Drosophila hsp70 heat shock gene were isolated. The mRNAs of genes hsp68, hsp70, and hsp80 could be translated in vitro into proteins of Mr 68,000, 70,000, and 80,000, respectively. Transcription of these genes increased dramatically upon heat shock, and the corresponding mRNAs rapidly accumulated, reaching a peak at around 30 min after a shift to the elevated temperature. Light also induced the accumulation of the mRNAs encoded by these heat shock genes. A shift of dark-grown cells to light resulted in a drastic increase in mRNA levels, which reached a maximum at around 1 h after the shift. Thus, in Chlamydomonas, expression of hsp70-homologous heat shock genes appears to be regulated by thermal stress and light. Images PMID:2779571

  15. Cambrian calcareous algae and bacteria

    NASA Astrophysics Data System (ADS)

    Luchinina, Veronica A.; Terleev, A. A.

    2003-01-01

    Individual calcareous algae were known in Riphean. Their mass distribution is connected to the beginning of Cambrian. Despite of a long history of study, the nature of this group long time remained not clear. The new unique finds of algae from East Sayan region have shown, that primary carbonate thallus disappeared in the process of fossilization, and after it the calcareous cover formed by association of bacteria and cyanobacteria only.

  16. Triacylglycerol Accumulation in Photosynthetic Cells in Plants and Algae.

    PubMed

    Du, Zhi-Yan; Benning, Christoph

    2016-01-01

    Plant and algal oils are some of the most energy-dense renewable compounds provided by nature. Triacylglycerols (TAGs) are the major constituent of plant oils, which can be converted into fatty acid methyl esters commonly known as biodiesel. As one of the most efficient producers of TAGs, photosynthetic microalgae have attracted substantial interest for renewable fuel production. Currently, the big challenge of microalgae based TAGs for biofuels is their high cost compared to fossil fuels. A conundrum is that microalgae accumulate large amounts of TAGs only during stress conditions such as nutrient deprivation and temperature stress, which inevitably will inhibit growth. Thus, a better understanding of why and how microalgae induce TAG biosynthesis under stress conditions would allow the development of engineered microalgae with increased TAG production during conditions optimal for growth. Land plants also synthesize TAGs during stresses and we will compare new findings on environmental stress-induced TAG accumulation in plants and microalgae especially in the well-characterized model alga Chlamydomonas reinhardtii and a biotechnologically relevant genus Nannochloropsis. PMID:27023236

  17. Relevance of nutrient media composition for hydrogen production in Chlamydomonas.

    PubMed

    Gonzalez-Ballester, David; Jurado-Oller, Jose Luis; Fernandez, Emilio

    2015-09-01

    Microalgae are capable of biological H2 photoproduction from water, solar energy, and a variety of organic substrates. Acclimation responses to different nutrient regimes finely control photosynthetic activity and can influence H2 production. Hence, nutrient stresses are an interesting scenario to study H2 production in photosynthetic organisms. In this review, we mainly focus on the H2-production mechanisms in Chlamydomonas reinhardtii and the physiological relevance of the nutrient media composition when producing H2. PMID:25952745

  18. Measurement of photorespiration in algae.

    PubMed

    Birmingham, B C; Coleman, J R; Colman, B

    1982-01-01

    The rates of true and apparent photosynthesis of two unicellular green algae, one diatom and four blue-green algae were measured in buffer at pH 8.0 at subsaturating concentrations of dissolved inorganic carbon (13-27 micromolar). Initial rates of depletion from the medium of inorganic carbon and (14)C activity caused by the algae in a closed system were measured by gas chromatography and by liquid scintillation counting, respectively. The rate of photorespiration was calculated as the difference between the rates of apparent and true photosynthesis. The three eucaryotic algae and two blue-green algae had photorespiratory rates of 10 to 28% that of true photosynthesis at air levels of O(2). Reduction of the O(2) level to 2% caused a 52 to 91% reduction in photorespiratory rate. Two other blue-green algae displayed low photorespiratory rates, 2.4 to 6.2% that of true photosynthesis at air levels of O(2), and reduction of the O(2) concentration had no effect on these rates. PMID:16662171

  19. Crystal structure of the Chlamydomonas starch debranching enzyme isoamylase ISA1 reveals insights into the mechanism of branch trimming and complex assembly.

    PubMed

    Sim, Lyann; Beeren, Sophie R; Findinier, Justin; Dauvillée, David; Ball, Steven G; Henriksen, Anette; Palcic, Monica M

    2014-08-15

    The starch debranching enzymes isoamylase 1 and 2 (ISA1 and ISA2) are known to exist in a large complex and are involved in the biosynthesis and crystallization of starch. It is suggested that the function of the complex is to remove misplaced branches of growing amylopectin molecules, which would otherwise prevent the association and crystallization of adjacent linear chains. Here, we investigate the function of ISA1 and ISA2 from starch producing alga Chlamydomonas. Through complementation studies, we confirm that the STA8 locus encodes for ISA2 and sta8 mutants lack the ISA1·ISA2 heteromeric complex. However, mutants retain a functional dimeric ISA1 that is able to partly sustain starch synthesis in vivo. To better characterize ISA1, we have overexpressed and purified ISA1 from Chlamydomonas reinhardtii (CrISA1) and solved the crystal structure to 2.3 Å and in complex with maltoheptaose to 2.4 Å. Analysis of the homodimeric CrISA1 structure reveals a unique elongated structure with monomers connected end-to-end. The crystal complex reveals details about the mechanism of branch binding that explains the low activity of CrISA1 toward tightly spaced branches and reveals the presence of additional secondary surface carbohydrate binding sites. PMID:24993830

  20. Gas Exchange of Algae

    PubMed Central

    Ammann, Elizabeth C. B.; Lynch, Victoria H.

    1965-01-01

    Continuously growing cultures of Chlorella pyrenoidosa Starr 252, operating at constant density and under constant environmental conditions, produced uniform photosynthetic quotient (PQ = CO2/O2) and O2 values during 6 months of observations. The PQ for the entire study was 0.90 ± 0.024. The PQ remained constant over a threefold light-intensity change and a threefold change in O2 production (0.90 ± 0.019). At low light intensities, when the rate of respiration approached the rate of photosynthesis, the PQ became extremely variable. Six lamps of widely different spectral-energy distribution produced no significant change in the PQ (0.90 ± 0.025). Oxygen production was directly related to the number of quanta available, irrespective of spectral-energy distribution. Such dependability in producing uniform PQ and O2 values warrants a consideration of algae to maintain a constant gas environment for submarine or spaceship use. Images Fig. 1 PMID:14339260

  1. Forward and reverse genetic analysis of microtubule motors in Chlamydomonas.

    PubMed

    Pazour, G J; Witman, G B

    2000-12-01

    The ability to integrate biochemical, cell biological, and genetic approaches makes Chlamydomonas reinhardtii the premier model organism for studies of the eukaryotic flagellum and its associated molecular motors. Hundreds of motility mutations have been identified in Chlamydomonas, including many that affect dyneins and kinesins. These mutations have yielded much information on the structure and function of the motors as well as the roles of individual subunits within the motors. The development of insertional mutagenesis has opened the door to powerful new approaches for genetic analysis in Chlamydomonas. Insertional mutants are created by transforming cells with DNA-containing selectable markers. The DNA is randomly integrated throughout the genome and usually deletes part of the chromosome at the site of insertion, thereby creating mutations that are marked by the integrated DNA. These mutations can be used for forward genetic approaches where one characterizes a mutant phenotype and then clones the relevant gene using the integrated DNA as a tag. The insertional mutants also may be used in a reverse genetic approach in which mutants lacking a gene of interest are identified by DNA hybridization. We describe methods to generate and characterize insertional mutants, using mutations that affect the outer dynein arm as examples. PMID:11133235

  2. N6-Methyldeoxyadenosine Marks Active Transcription Start Sites in Chlamydomonas

    PubMed Central

    Chen, Kai; Deng, Xin; Yu, Miao; Han, Dali; Hao, Ziyang; Liu, Jianzhao; Lu, Xingyu; Dore, Louis C; Weng, Xiaocheng; Ji, Quanjiang; Mets, Laurens; He, Chuan

    2015-01-01

    SUMMARY N6-methyldeoxyadenosine (6mA or m6A) is a DNA modification preserved in prokaryotes to eukaryotes. It is widespread in bacteria, and functions in DNA mismatch repair, chromosome segregation, and virulence regulation. In contrast, the distribution and function of 6mA in eukaryotes have been unclear. Here we present a comprehensive analysis of the 6mA landscape in the genome of Chlamydomonas using new sequencing approaches. We identified the 6mA modification in 84% of genes in Chlamydomonas. We found that 6mA mainly locates at ApT dinucleotides around transcription start sites (TSS) with a bimodal distribution, and appears to mark active genes. A periodic pattern of 6mA deposition was also observed at base resolution, which is associated with nucleosome distribution near the TSS, suggesting a possible role in nucleosome positioning. The new genome-wide mapping of 6mA and its unique distribution in the Chlamydomonas genome suggest potential regulatory roles of 6mA in gene expression in eukaryotic organisms. PMID:25936837

  3. Actin is required for IFT regulation in Chlamydomonas reinhardtii

    PubMed Central

    Avasthi, Prachee; Onishi, Masayuki; Karpiak, Joel; Yamamoto, Ryosuke; Mackinder, Luke; Jonikas, Martin C.; Sale, Winfield S.; Shoichet, Brian; Pringle, John R.; Marshall, Wallace F.

    2014-01-01

    Summary Assembly of cilia and flagella requires intraflagellar transport (IFT), a highly regulated kinesin-based transport system that moves cargo from the basal body to the tip of flagella [1]. The recruitment of IFT components to basal bodies is a function of flagellar length, with increased recruitment in rapidly growing short flagella [2]. The molecular pathways regulating IFT are largely a mystery. Since actin network disruption leads to changes in ciliary length and number, actin has been proposed to have a role in ciliary assembly. However, the mechanisms involved are unknown. In Chlamydomonas reinhardtii, conventional actin is found in both the cell body and the inner dynein arm complexes within flagella [3, 4]. Previous work showed that treating Chlamydomonas cells with the actin-depolymerizing compound cytochalasin D resulted in reversible flagellar shortening [5], but how actin is related to flagellar length or assembly remains unknown. Here, we utilize small-molecule inhibitors and genetic mutants to analyze the role of actin dynamics in flagellar assembly in Chlamydomonas reinhardtii. We demonstrate that actin plays a role in IFT recruitment to basal bodies during flagellar elongation, and that when actin is perturbed, the normal dependence of IFT recruitment on flagellar length is lost. We also find that actin is required for sufficient entry of IFT material into flagella during assembly. These same effects are recapitulated with a myosin inhibitor suggesting actin may act via myosin in a pathway by which flagellar assembly is regulated by flagellar length. PMID:25155506

  4. Actin is required for IFT regulation in Chlamydomonas reinhardtii.

    PubMed

    Avasthi, Prachee; Onishi, Masayuki; Karpiak, Joel; Yamamoto, Ryosuke; Mackinder, Luke; Jonikas, Martin C; Sale, Winfield S; Shoichet, Brian; Pringle, John R; Marshall, Wallace F

    2014-09-01

    Assembly of cilia and flagella requires intraflagellar transport (IFT), a highly regulated kinesin-based transport system that moves cargo from the basal body to the tip of flagella [1]. The recruitment of IFT components to basal bodies is a function of flagellar length, with increased recruitment in rapidly growing short flagella [2]. The molecular pathways regulating IFT are largely a mystery. Because actin network disruption leads to changes in ciliary length and number, actin has been proposed to have a role in ciliary assembly. However, the mechanisms involved are unknown. In Chlamydomonas reinhardtii, conventional actin is found in both the cell body and the inner dynein arm complexes within flagella [3, 4]. Previous work showed that treating Chlamydomonas cells with the actin-depolymerizing compound cytochalasin D resulted in reversible flagellar shortening [5], but how actin is related to flagellar length or assembly remains unknown. Here we utilize small-molecule inhibitors and genetic mutants to analyze the role of actin dynamics in flagellar assembly in Chlamydomonas reinhardtii. We demonstrate that actin plays a role in IFT recruitment to basal bodies during flagellar elongation and that when actin is perturbed, the normal dependence of IFT recruitment on flagellar length is lost. We also find that actin is required for sufficient entry of IFT material into flagella during assembly. These same effects are recapitulated with a myosin inhibitor, suggesting that actin may act via myosin in a pathway by which flagellar assembly is regulated by flagellar length. PMID:25155506

  5. Nucleated assembly of Chlamydomonas and Volvox cell walls.

    PubMed

    Adair, W S; Steinmetz, S A; Mattson, D M; Goodenough, U W; Heuser, J E

    1987-11-01

    The Chlamydomonas reinhardtii cell wall is made up of hydroxyproline-rich glycoproteins, arranged in five distinct layers. The W6 (crystalline) layer contains three major glycoproteins (GP1, GP2, GP3), selectively extractable with chaotropic agents, that self-assemble into crystals in vitro. A system to study W6 assembly in a quantitative fashion was developed that employs perchlorate-extracted Chlamydomonas cells as nucleating agents. Wall reconstitution by biotinylated W6 monomers was monitored by FITC-streptavidin fluorescence and quick-freeze/deep-etch electron microscopy. Optimal reconstitution was obtained at monomer concentrations (0.2-0.3 mg/ml) well below those required for nonnucleated assembly. Assembly occurred from multiple nucleation sites, and faithfully reflected the structure of the intact W6 layer. Specificity of nucleated assembly was demonstrated using two cell-wall mutants (cw-2 and cw-15); neither served as a substrate for assembly of wild-type monomers. In addition, W6 sublayers were assembled from purified components: GP2 and GP3 coassembled to form the inner (W6A) sublayer; this then served as a substrate for self-assembly of GP1 into the outer (W6B) sublayer. Finally, evolutionary relationships between C. reinhardtii and two additional members of the Volvocales (Chlamydomonas eugametos and Volvox carteri) were explored by performing interspecific reconstitutions. Hybrid walls were obtained between C. reinhardtii and Volvox but not with C. eugametos, confirming taxonomic assignments based on structural criteria. PMID:3680387

  6. Geographic variation in the damselfish-red alga cultivation mutualism in the Indo-West Pacific

    PubMed Central

    2010-01-01

    Background On coral reefs, damselfish defend their territories from invading herbivores and maintain algal turfs, from which they harvest filamentous algae. In southern Japan, intensive weeding of indigestible algae by Stegastes nigricans results in overgrowth by one filamentous alga, Polysiphonia sp. 1. Because this alga is highly susceptible to grazing and is competitively inferior to other algae, it survives only within the protective territories of this fish species, suggesting an obligate mutualism between damselfish and their cultivated alga. The wide distribution of damselfish species through the Indo-Central Pacific raises the question of whether this species-specific mutualism is maintained throughout the geographic range of the fish. To address this question, from all 18 damselfish species we conducted comprehensive surveys of algal flora within their territories throughout the Indo-West Pacific, and identified species of Polysiphonia using morphological examination and gene sequencing data. Results Several species of the genus Polysiphonia were observed as a major crop in territories throughout the geographic range of S. nigricans. Polysiphonia sp. 1 occurred only in territories of S. nigricans in central areas of the Indo-Pacific. However, its occurrence was low from the Great Barrier Reef and Mauritius. In contrast, other indigenous Polysiphonia species, which formed a clade with Polysiphonia sp. 1, occurred in the territories of fishes from Egypt, Kenya, and the Maldives. The other Polysiphonia species in the clade only inhabited damselfish territories and were never found elsewhere. Conclusions Cultivation mutualism between the damselfish S. nigricans and algae of Polysiphonia was maintained throughout the Indo-West Pacific, although algal crop species and the mode of cultivation (e.g., presence/absence of selective weeding, the species composition of algal turfs) varied among localities. This finding implies that damselfish utilize indigenous

  7. Response of freshwater algae to water quality in Qinshan Lake within Taihu Watershed, China

    NASA Astrophysics Data System (ADS)

    Zhang, Jianying; Ni, Wanmin; Luo, Yang; Jan Stevenson, R.; Qi, Jiaguo

    Although frequent algal blooms in Taihu Lake in China have become major environmental problems and have drawn national and international attention, little is understood about the relationship between algal blooms and water quality. The goal of this study was to assess the growth and species responses of freshwater algae to variation in water quality in Qinshan Lake, located in headwaters of the Taihu watershed. Water samples were collected monthly from ten study sites in the Qinshan Lake and were analyzed for species distribution of freshwater algae and physiochemical parameters such as total nitrogen (TN), NH4+-N, NO3--N, total phosphorus (TP), chemical oxygen demand (COD Mn) and Chl-a. The results showed that average TN was 4.47 mg/L, with 92.2% of values greater than the TN standard set by the Chinese Environmental Protection Agency; average TP was 0.051 mg/L, with 37.9% of values above the TP national standard; and average trophic level index (TLI) was 53, the lower end of eutrophic condition. Average Chl-a concentration was 12.83 mg/m 3. Green algae and diatom far outweighed other freshwater algae and were dominant most time of the year, with the highest relative abundances of 96% and 99%, respectively. Blue-green algae, composed mainly toxic strains like Microcystis sp ., Nostoc sp. and Oscillatoria sp., became most dominant in the summer with the maximum relative abundance of 69%. The blue-green algae sank to the lake bottom to overwinter, and then dinoflagellates became the dominant species in the winter, with highest relative abundance of 89%. Analysis indicated that nutrients, especially control of ammonia and co-varying nutrients were the major restrictive factor of population growth of blue-green algae, suggesting that control in nutrient enrichments is the major preventive measure of algal blooms in Qinshan Lake.

  8. The family of DOF transcription factors: from green unicellular algae to vascular plants.

    PubMed

    Moreno-Risueno, Miguel Angel; Martínez, Manuel; Vicente-Carbajosa, Jesús; Carbonero, Pilar

    2007-04-01

    This article deals with the origin and evolution of the DOF transcription factor family through a phylogenetic analysis of those DOF sequences identified from a variety of representative organisms from different taxonomic groups: the green unicellular alga Chlamydomonas reinhardtii, the moss Physcomitrella patens, the fern Selaginella moellendorffii, the gymnosperm Pinus taeda, the dicotyledoneous Arabidopsis thaliana and the monocotyledoneous angiosperms Oryza sativa and Hordeum vulgare. In barley, we have identified 26 different DOF genes by sequence analyses of clones isolated from the screening of genomic libraries and of ESTs, whereas a single DOF gene was identified by bioinformatics searches in the Chlamydomonas genome. The phylogenetic analysis groups all these genes into six major clusters of orthologs originated from a primary basal grade. Our results suggest that duplications of an ancestral DOF, probably formed in the photosynthetic eukaryotic ancestor, followed by subsequent neo-, sub-functionalization and pseudogenization processes would have triggered the expansion of the DOF family. Loss, acquisition and shuffling of conserved motifs among the new DOFs likely underlie the mechanism of formation of the distinct subfamilies. PMID:17180359

  9. [Phototaxis of the green algae: the new class of rhodopsin receptors].

    PubMed

    Govorunova, E G; Jung, K H; Sineshchekov, O A

    2004-01-01

    Photomotility behavior in green flagellate algae is mediated by rhodopsin-like receptors, which was initially suggested on the basis of physiological evidence. The cascade of rapid Ca(2+)-dependent electrical responses in the plasma membrane plays a key role in the signal transduction chain during both phototaxis and the photophobic response. The photoreceptor current through the plasma membrane is the earliest detectable event upon photoexcitation of the photoreceptors. Analysis of this current revealed that it consists of at least two components with different characteristics. Genes encoding two archaeal-type rhodopsins (type I rhodopsins) were recently identified in the genome of Chlamydomonas reinhardtii and named (Chlamydomonas Sensory Rhodopsins A and B CSRA and CSRB). The measurements of photoelectric and motor responses in genetic transformants of C. reinhardtii enriched in each of these receptor proteins showed that the two components of the photoreceptor current are mediated by the two rhodopsins, and that both CSRA and CSRB are involved in phototaxis and the photophobic response. The CSRA-mediated current dominates at high light intensities and contributes primarily to the photophobic response. The CSRB-initiated transduction involves an efficient amplification cascade and mediates the highly sensitive phototaxis at low light intensities. CSRA and CSRB expressed heterologously in oocytes of Xenopus laevis act as light-gated proton channels, although it is unclear whether this channel activity plays a functional role in the initiation of motor responses and/or occurs in the native system. PMID:15129628

  10. Phylogenetic relationships of the green alga Volvox carteri deduced from small-subunit ribosomal RNA comparisons.

    PubMed

    Rausch, H; Larsen, N; Schmitt, R

    1989-09-01

    The 1788-nucleotide sequence of the small-subunit ribosomal RNA (srRNA) coding region from the chlorophyte Volvox carteri was determined. The secondary structure bears features typical of the universal model of srRNA, including about 40 helices and a division into four domains. Phylogenetic relationships to 17 other eukaryotes, including two other chlorophytes, were explored by comparing srRNA sequences. Similarity values and the inspection of phylogenetic trees derived by distance matrix methods revealed a close relationship between V. carteri and Chlamydomonas reinhardtii. The results are consistent with the view that these Volvocales, and the third green alga, Nanochlorum eucaryotum, are more closely related to higher plants than to any other major eukaryotic group, but constitute a distinct lineage that has long been separated from the line leading to the higher plants. PMID:2506359

  11. Analysis of uncultured extremophilic snow algae by non-invasive single cell Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Beer, Thomas; Tanaka, Zuki; Netzter, Nathan; Rothschild, Lynn J.; Chen, Bin

    2011-10-01

    The study of life in extreme environments is a critical component of Astrobiology. But many of the so-called "extremophiles" are not readily cultivatable and therefore difficult to study under laboratory conditions. An example of such an extremophile is the snow alga Chlamydomonas cd. nivalis which expresses still unstudied secondary metabolites within its life cycle. In this paper, we present the first time the non-invasive single cell Raman spectroscopy of the life cycle dependent metabolite composition of C. nivalis. These secondary metabolites are likely related to the adaptation of C. nivalis to various stress factors. Normalized carotenoid Raman spectra intensities reveal characteristic ratio differences that allow identification of life cycle stages and putative secondary metabolites.

  12. Flagellated Algae Protein Evolution Suggests the Prevalence of Lineage-Specific Rules Governing Evolutionary Rates of Eukaryotic Proteins

    PubMed Central

    Chang, Ting-Yan; Liao, Ben-Yang

    2013-01-01

    Understanding the general rules governing the rate of protein evolution is fundamental to evolutionary biology. However, attempts to address this issue in yeasts and mammals have revealed considerable differences in the relative importance of determinants for protein evolutionary rates. This phenomenon was previously explained by the fact that yeasts and mammals are different in many cellular and genomic properties. Flagellated algae species have several cellular and genomic characteristics that are intermediate between yeasts and mammals. Using partial correlation analyses on the evolution of 6,921 orthologous proteins from Chlamydomonas reinhardtii and Volvox carteri, we examined factors influencing evolutionary rates of proteins in flagellated algae. Previous studies have shown that mRNA abundance and gene compactness are strong determinants for protein evolutionary rates in yeasts and mammals, respectively. We show that both factors also influence algae protein evolution with mRNA abundance having a larger impact than gene compactness on the rates of algae protein evolution. More importantly, among all the factors examined, coding sequence (CDS) length has the strongest (positive) correlation with protein evolutionary rates. This correlation between CDS length and the rates of protein evolution is not due to alignment-related issues or domain density. These results suggest no simple and universal rules governing protein evolutionary rates across different eukaryotic lineages. Instead, gene properties influence the rate of protein evolution in a lineage-specific manner. PMID:23563973

  13. Flagellated algae protein evolution suggests the prevalence of lineage-specific rules governing evolutionary rates of eukaryotic proteins.

    PubMed

    Chang, Ting-Yan; Liao, Ben-Yang

    2013-01-01

    Understanding the general rules governing the rate of protein evolution is fundamental to evolutionary biology. However, attempts to address this issue in yeasts and mammals have revealed considerable differences in the relative importance of determinants for protein evolutionary rates. This phenomenon was previously explained by the fact that yeasts and mammals are different in many cellular and genomic properties. Flagellated algae species have several cellular and genomic characteristics that are intermediate between yeasts and mammals. Using partial correlation analyses on the evolution of 6,921 orthologous proteins from Chlamydomonas reinhardtii and Volvox carteri, we examined factors influencing evolutionary rates of proteins in flagellated algae. Previous studies have shown that mRNA abundance and gene compactness are strong determinants for protein evolutionary rates in yeasts and mammals, respectively. We show that both factors also influence algae protein evolution with mRNA abundance having a larger impact than gene compactness on the rates of algae protein evolution. More importantly, among all the factors examined, coding sequence (CDS) length has the strongest (positive) correlation with protein evolutionary rates. This correlation between CDS length and the rates of protein evolution is not due to alignment-related issues or domain density. These results suggest no simple and universal rules governing protein evolutionary rates across different eukaryotic lineages. Instead, gene properties influence the rate of protein evolution in a lineage-specific manner. PMID:23563973

  14. Salicylhydroxamic acid (SHAM) inhibition of the dissolved inorganic carbon concentrating process in unicellular green algae

    SciTech Connect

    Goyal, A.; Tolbert, N.E. )

    1990-03-01

    Rates of photosynthetic O{sub 2} evolution, for measuring K{sub 0.5}(CO{sub 2} + HCO{sub 3}{sup {minus}}) at pH 7, upon addition of 50 micromolar HCO{sub 3}{sup {minus}} to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K{sub i}(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO{sub 2} uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O{sub 2} evolution dependent on low levels of dissolved inorganic carbon (50 micromolar NaHCO{sub 3}), and the rate of {sup 14}CO{sub 2} fixation with 100 micromolar ({sup 14}C)HCO{sub 3}{sup {minus}}. Salicylhydroxamic acid inhibition of O{sub 2} evolution and {sup 14}CO{sub 2}-fixation was reversed by higher levels of NaHCO{sub 3}. Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO{sub 2} accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

  15. Transcriptional program for nitrogen starvation-induced lipid accumulation in Chlamydomonas reinhardtii

    SciTech Connect

    Garcia de Lomana, Adrian Lopez; Schäuble, Sascha; Valenzuela, Jacob; Imam, Saheed; Carter, Warren; Bilgin, Damla D.; Yohn, Christopher B.; Turkarslan, Serdar; Reiss, David J.; Orellana, Monica V.; Price, Nathan D.; Baliga, Nitin S.

    2015-12-02

    Algae accumulate lipids to endure different kinds of environmental stresses including macronutrient starvation. Although this response has been extensively studied, an in depth understanding of the transcriptional regulatory network (TRN) that controls the transition into lipid accumulation remains elusive. In this study, we used a systems biology approach to elucidate the transcriptional program that coordinates the nitrogen starvation-induced metabolic readjustments that drive lipid accumulation in Chlamydomonas reinhardtii. We demonstrate that nitrogen starvation triggered differential regulation of 2147 transcripts, which were co-regulated in 215 distinct modules and temporally ordered as 31 transcriptional waves. An early-stage response was triggered within 12 min that initiated growth arrest through activation of key signaling pathways, while simultaneously preparing the intracellular environment for later stages by modulating transport processes and ubiquitin-mediated protein degradation. Subsequently, central metabolism and carbon fixation were remodeled to trigger the accumulation of triacylglycerols. Further analysis revealed that these waves of genome-wide transcriptional events were coordinated by a regulatory program orchestrated by at least 17 transcriptional regulators, many of which had not been previously implicated in this process. We demonstrate that the TRN coordinates transcriptional downregulation of 57 metabolic enzymes across a period of nearly 4 h to drive an increase in lipid content per unit biomass. Notably, this TRN appears to also drive lipid accumulation during sulfur starvation, while phosphorus starvation induces a different regulatory program. The TRN model described here is available as a community-wide web-resource at http://networks.systemsbiology.net/chlamy-portal. In conclusion, in this work, we have uncovered a comprehensive mechanistic model of the TRN controlling the transition from N starvation to lipid accumulation