Specific inhibition of antenna bacteriochlorophyll synthesis in Chlorobium vibrioforme by anesthetic gases.

PubMed Central

Ormerod, J G; Nesbakken, T; Beale, S I

1990-01-01

The green sulfur bacterium Chlorobium vibrioforme contains two types of bacteriochlorophyll (Bchl). The minor pigment, Bchl a, is associated primarily with the cell membrane and its reaction centers; and the major light-harvesting antenna pigment, Bchl d, is found primarily in the chlorosomes, which are attached to the inner surface of the cell membrane. Anesthetic gases, such as N2O, ethylene, and acetylene, were found to inhibit the synthesis of Bchl d, but not of Bchl a, thus allowing the cells to grow at high light intensities with a greatly diminished content of antenna pigment. Chlorosomes were absent or sparse in inhibited cells. Porphyrins accumulated in the inhibited cells. The major one was identified as the Bchl precursor magnesium-protoporphyrin IX monomethyl ester (Mg-PPME) by comparative absorption and fluorescence spectroscopy and thin-layer chromatography of the porphyrin and its derivatives with those of authentic protoporphyrin IX. Small amounts of Mg-PPME were present in control cells, but the addition of inhibitor caused a rapid increase in the Mg-PPME concentration, accompanying the inhibition of Bchl d synthesis. Cells grown in the presence of ethephon (as a source of ethylene) and allowed to stand in dim light for long periods accumulated large amounts of PPME and other porphyrins and excreted or released porphyrins, which accumulated as a brown precipitate in the culture. Inhibition of Bchl d synthesis was relieved upon removal of the inhibitor. These results suggest that the gases act at a step in pigment biosynthesis that affects the utilization of Mg-PPME for isocyclic ring formation. Synthesis of Bchl d and Bchl a may be differentially affected by the gases because of compartmentation of their biosynthetic apparatus or because competition for precursors favors Bchl a synthesis. An ethephon-resistant mutant strain was isolated by selection for growth in dim, long-wavelength light. The mutant cells were also resistant to acetylene, but not

[Metabolism of carbohydrates in the cells of green sulphur bacteria Chlorobium limicola Ya-2002].

PubMed

Horishnyĭ, M B; Hudz', S P; Hnatush, S O

2009-01-01

The nature of carbohydrates that accumulate in the cells of photosynthetic green sulphur bacteria of Chlorobium limicola Ya-2002 has been investigated. It is shown by infra-red spectrometry, that carbohydrates accumulated in the cells of bacteria are identical (by 90-95%) to glycogen of the bull liver. Exogenous glucose, saccharose, maltose, did not stimulate formation of glycogen. Growth of glycogen level in the cells of bacteria was observed at addition of acetate or piruvate in the conditions of bacteria cultivation in the light and in the presence CO2 and H2S in the environment. Washed cells of C. limicola Ya-2002 did not use glucose of the environment neither in the conditions of illumination nor in darkness, however acetate and piruvate are actively used in the light. During incubation of the washed cells in darkness the level of glycogen fell down approximately three times. Its amount during cells incubation in the light did not change. The decline of glycogen level in cells during their incubation in darkness was accompanied by piling up of carbonic acids in the environment acetate prevailing among them.

Production of polyhydroxybutyrate by the marine photosynthetic bacterium Rhodovulum sulfidophilum P5

NASA Astrophysics Data System (ADS)

Cai, Jinling; Wei, Ying; Zhao, Yupeng; Pan, Guanghua; Wang, Guangce

2012-07-01

The effects of different NaCl concentrations, nitrogen sources, carbon sources, and carbon to nitrogen molar ratios on biomass accumulation and polyhydroxybutyrate (PHB) production were studied in batch cultures of the marine photosynthetic bacterium Rhodovulum sulfidophilum P5 under aerobic-dark conditions. The results show that the accumulation of PHB in strain P5 is a growth-associated process. Strain P5 had maximum biomass and PHB accumulation at 2%-3% NaCl, suggesting that the bacterium can maintain growth and potentially produce PHB at natural seawater salinity. In the nitrogen source test, the maximum biomass accumulation (8.10±0.09 g/L) and PHB production (1.11±0.13 g/L and 14.62%±2.2 of the cell dry weight) were observed when peptone and ammonium chloride were used as the sole nitrogen source. NH{4/+}-N was better for PHB production than other nitrogen sources. In the carbon source test, the maximum biomass concentration (7.65±0.05 g/L) was obtained with malic acid as the sole carbon source, whereas the maximum yield of PHB (5.03±0.18 g/L and 66.93%±1.69% of the cell dry weight) was obtained with sodium pyruvate as the sole carbon source. In the carbon to nitrogen ratios test, sodium pyruvate and ammonium chloride were selected as the carbon and nitrogen sources, respectively. The best carbon to nitrogen molar ratio for biomass accumulation (8.77±0.58 g/L) and PHB production (6.07±0.25 g/L and 69.25%±2.05% of the cell dry weight) was 25. The results provide valuable data on the production of PHB by R. sulfidophilum P5 and further studies are on-going for best cell growth and PHB yield.

Breakdown of food waste by anaerobic fermentation and non-oxygen producing photosynthesis using a photosynthetic bacterium.

PubMed

Mekjinda, N; Ritchie, R J

2015-01-01

Large volumes of food waste are produced by restaurants, hotels, etc generating problems in its collection, processing and disposal. Disposal as garbage increases the organic matter in landfills and leachates. The photosynthetic bacterium Rhodopseudomonas palustris (CGA 009) easily broke down food waste. R. palustris produces H2 under anaerobic conditions and digests a very wide range of organic compounds. R. palustris reduced BOD by ≈70% and COD by ≈33%, starch, ammonia, nitrate, was removed but had little effect on reducing sugar or the total phosphorus, lipid, protein, total solid in a 7-day incubation. R. palustris produced a maximum of 80ml H2/g COD/day. A two-stage anaerobic digestion using yeast as the first stage, followed by a R. palustris digestion was tested but production of H2 was low. Copyright © 2014 Elsevier Ltd. All rights reserved.

Isolation, characterization, and amino acid sequences of auracyanins, blue copper proteins from the green photosynthetic bacterium Chloroflexus aurantiacus

NASA Technical Reports Server (NTRS)

McManus, J. D.; Brune, D. C.; Han, J.; Sanders-Loehr, J.; Meyer, T. E.; Cusanovich, M. A.; Tollin, G.; Blankenship, R. E.

1992-01-01

Three small blue copper proteins designated auracyanin A, auracyanin B-1, and auracyanin B-2 have been isolated from the thermophilic green gliding photosynthetic bacterium Chloroflexus aurantiacus. All three auracyanins are peripheral membrane proteins. Auracyanin A was described previously (Trost, J. T., McManus, J. D., Freeman, J. C., Ramakrishna, B. L., and Blankenship, R. E. (1988) Biochemistry 27, 7858-7863) and is not glycosylated. The two B forms are glycoproteins and have almost identical properties to each other, but are distinct from the A form. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis apparent monomer molecular masses are 14 (A), 18 (B-2), and 22 (B-1) kDa. The amino acid sequences of the B forms are presented. All three proteins have similar absorbance, circular dichroism, and resonance Raman spectra, but the electron spin resonance signals are quite different. Laser flash photolysis kinetic analysis of the reactions of the three forms of auracyanin with lumiflavin and flavin mononucleotide semiquinones indicates that the site of electron transfer is negatively charged and has an accessibility similar to that found in other blue copper proteins. Copper analysis indicates that all three proteins contain 1 mol of copper per mol of protein. All three auracyanins exhibit a midpoint redox potential of +240 mV. Light-induced absorbance changes and electron spin resonance signals suggest that auracyanin A may play a role in photosynthetic electron transfer. Kinetic data indicate that all three proteins can donate electrons to cytochrome c-554, the electron donor to the photosynthetic reaction center.

High-pressure and stark hole-burning studies of chlorosome antennas from Chlorobium tepidum.

PubMed

Wu, H M; Rätsep, M; Young, C S; Jankowiak, R; Blankenship, R E; Small, G J

2000-09-01

Results from high-pressure and Stark hole-burning experiments on isolated chlorosomes from the green sulfur bacterium Chlorobium tepidum are presented, as well as Stark hole-burning data for bacteriochlorophyll c (BChl c) monomers in a poly(vinyl butyral) copolymer film. Large linear pressure shift rates of -0.44 and -0.54 cm(-1)/MPa were observed for the chlorosome BChl c Q(y)-band at 100 K and the lowest Q(y)-exciton level at 12 K, respectively. It is argued that approximately half of the latter shift rate is due to electron exchange coupling between BChl c molecules. The similarity between the above shift rates and those observed for the B875 and B850 BChl a rings of the light-harvesting complexes of purple bacteria is emphasized. For BChl c monomer, fDeltamu++ = 0.35 D, where Deltamu+ is the dipole moment change for the Q(y) transition and f is the local field correction factor. The data establish that Deltamu+ is dominated by the matrix-induced contribution. The change in polarizability (Deltaalpha) for the Q(y) transition of the BChl c monomer is estimated at 19 A(3), which is essentially identical to that of the Chl a monomer. Interestingly, no Stark effects were observed for the lowest exciton level of the chlorosomes (maximum Stark field of 10(5) V/cm). Possible explanations for this are given, and these include consideration of structural models for the chlorosome BChl c aggregates.

Production of bioplastics and hydrogen gas by photosynthetic microorganisms

NASA Astrophysics Data System (ADS)

Yasuo, Asada; Masato, Miyake; Jun, Miyake

1998-03-01

Our efforts have been aimed at the technological basis of photosynthetic-microbial production of materials and an energy carrier. We report here accumulation of poly-(3-hydroxybutyrate) (PHB), a raw material of biodegradable plastics and for production of hydrogen gas, and a renewable energy carrier by photosynthetic microorganisms (tentatively defined as cyanobacteria plus photosynthetic bateria, in this report). A thermophilic cyanobacterium, Synechococcus sp. MA19 that accumulates PHB at more than 20% of cell dry wt under nitrogen-starved conditions was isolated and microbiologically identified. The mechanism of PHB accumulation was studied. A mesophilic Synechococcus PCC7942 was transformed with the genes encoding PHB-synthesizing enzymes from Alcaligenes eutrophus. The transformant accumulated PHB under nitrogen-starved conditions. The optimal conditions for PHB accumulation by a photosynthetic bacterium grown on acetate were studied. Hydrogen production by photosynthetic microorganisms was studied. Cyanobacteria can produce hydrogen gas by nitrogenase or hydrogenase. Hydrogen production mediated by native hydrogenase in cyanobacteria was revealed to be in the dark anaerobic degradation of intracellular glycogen. A new system for light-dependent hydrogen production was targeted. In vitro and in vivo coupling of cyanobacterial ferredoxin with a heterologous hydrogenase was shown to produce hydrogen under light conditions. A trial for genetic trasformation of Synechococcus PCC7942 with the hydrogenase gene from Clostridium pasteurianum is going on. The strong hydrogen producers among photosynthetic bacteria were isolated and characterized. Co-culture of Rhodobacter and Clostriumdium was applied to produce hydrogen from glucose. Conversely in the case of cyanobacteria, genetic regulation of photosynthetic proteins was intended to improve conversion efficiency in hydrogen production by the photosynthetic bacterium, Rhodobacter sphaeroides RV. A mutant acquired by

[Chlorobaculum macestae sp. nov., a new green sulfur bacterium].

PubMed

Koppen, O I; Berg, I A; Lebedeva, N V; Taisova, A S; Kolganova, T V; Slobodova, N V; Bulygina, E S; Turova, T P; Ivanovskiĭ, R N

2008-01-01

The investigated green sulfur bacterium, strain M, was isolated from a sulfidic spring on the Black Sea Coast of the Caucasus. The cells of strain M are straight or curved rods 0.6-0.9 x 1.8-4.2 microm in size. According to the cell wall structure, the bacteria are gram-negative. Chlorosomes are located along the cell periphery. Strain M is an obligate anaerobe capable of photoautotrophic growth on sulfide, thiosulfate, and H2. It utilizes ammonium, urea, casein hydrolysate, and N2 as nitrogen sources and sulfide, thiosulfate, and elemental sulfur as sulfur sources. Bacteriochlorophyll c and the carotenoid chlorobactene are the main pigments. The optimal growth temperature is 25-28 degrees C; the optimal pH is 6.8. The strain does not require NaCl. Vitamin B12 stimulates growth. The content of the G+C base pairs in the DNA of strain M is 58.3 mol %. In the phylogenetic tree constructed on the basis of analysis of nucleotide sequences of 16S rRNA genes, strain M forms a separate branch, which occupies an intermediate position between the phylogenetic cluster containing representatives of the genus Chlorobaculum (94.9-96.8%) and the cluster containing species of the genus Chlorobium (94.1-96.5%). According to the results of analysis of the amino acid sequence corresponding to the fmo gene, strain M represents a branch which, unlike that in the "ribosomal" tree, falls into the cluster of the genus Chlorobaculum (95.8-97.2%). Phylogenetic analysis of the amino acid sequence corresponding to the nifH gene placed species of the genera Chlorobaculum and Chlorobium into a single cluster, whereas strain M formed a separate branch. The results obtained allow us to describe strain M as a new species of the genus Chlorobaculum. Chlorobaculum macestae sp. nov.

Effects of oxidants and reductants on the efficiency of excitation transfer in green photosynthetic bacteria

NASA Technical Reports Server (NTRS)

Wang, J.; Brune, D. C.; Blankenship, R. E.

1990-01-01

The efficiency of energy transfer in chlorosome antennas in the green sulfur bacteria Chlorobium vibrioforme and Chlorobium limicola was found to be highly sensitive to the redox potential of the suspension. Energy transfer efficiencies were measured by comparing the absorption spectrum of the bacteriochlorophyll c or d pigments in the chlorosome to the excitation spectrum for fluorescence arising from the chlorosome baseplate and membrane-bound antenna complexes. The efficiency of energy transfer approaches 100% at low redox potentials induced by addition of sodium dithionite or other strong reductants, and is lowered to 10-20% under aerobic conditions or after addition of a variety of membrane-permeable oxidizing agents. The redox effect on energy transfer is observed in whole cells, isolated membranes and purified chlorosomes, indicating that the modulation of energy transfer efficiency arises within the antenna complexes and is not directly mediated by the redox state of the reaction center. It is proposed that chlorosomes contain a component that acts as a highly quenching center in its oxidized state, but is an inefficient quencher when reduced by endogenous or exogenous reductants. This effect may be a control mechanism that prevents cellular damage resulting from reaction of oxygen with reduced low-potential electron acceptors found in the green sulfur bacteria. The redox modulation effect is not observed in the green gliding bacterium Chloroflexus aurantiacus, which contains chlorosomes but does not contain low-potential electron acceptors.

Excitonic Energy Landscape of the Y16F Mutant of the Chlorobium tepidum Fenna-Matthews-Olson (FMO) Complex: High Resolution Spectroscopic and Modeling Studies.

PubMed

Khmelnitskiy, Anton; Saer, Rafael G; Blankenship, Robert E; Jankowiak, Ryszard

2018-04-12

We report high-resolution (low-temperature) absorption, emission, and nonresonant/resonant hole-burned (HB) spectra and results of excitonic calculations using a non-Markovian reduced density matrix theory (with an improved algorithm for parameter optimization in heterogeneous samples) obtained for the Y16F mutant of the Fenna-Matthews-Olson (FMO) trimer from the green sulfur bacterium Chlorobium tepidum. We show that the Y16F mutant is a mixture of FMO complexes with three independent low-energy traps (located near 817, 821, and 826 nm), in agreement with measured composite emission and HB spectra. Two of these traps belong to mutated FMO subpopulations characterized by significantly modified low-energy excitonic states. Hamiltonians for the two major subpopulations (Sub 821 and Sub 817 ) provide new insight into extensive changes induced by the single-point mutation in the vicinity of BChl 3 (where tyrosine Y16 was replaced with phenylalanine F16). The average decay time(s) from the higher exciton state(s) in the Y16F mutant depends on frequency and occurs on a picosecond time scale.

Influence of organics and silica on Fe(II) oxidation rates and cell-mineral aggregate formation by the green-sulfur Fe(II)-oxidizing bacterium Chlorobium ferrooxidans KoFox - Implications for Fe(II) oxidation in ancient oceans

NASA Astrophysics Data System (ADS)

Gauger, Tina; Byrne, James M.; Konhauser, Kurt O.; Obst, Martin; Crowe, Sean; Kappler, Andreas

2016-06-01

Most studies on microbial phototrophic Fe(II) oxidation (photoferrotrophy) have focused on purple bacteria, but recent evidence points to the importance of green-sulfur bacteria (GSB). Their recovery from modern ferruginous environments suggests that these photoferrotrophs can offer insights into how their ancient counterparts grew in Archean oceans at the time of banded iron formation (BIF) deposition. It is unknown, however, how Fe(II) oxidation rates, cell-mineral aggregate formation, and Fe-mineralogy vary under environmental conditions reminiscent of the geological past. To address this, we studied the Fe(II)-oxidizer Chlorobium ferrooxidans KoFox, a GSB living in co-culture with the heterotrophic Geospirillum strain KoFum. We investigated the mineralogy of Fe(III) metabolic products at low/high light intensity, and in the presence of dissolved silica and/or fumarate. Silica and fumarate influenced the crystallinity and particle size of the produced Fe(III) minerals. The presence of silica also enhanced Fe(II) oxidation rates, especially at high light intensities, potentially by lowering Fe(II)-toxicity to the cells. Electron microscopic imaging showed no encrustation of either KoFox or KoFum cells with Fe(III)-minerals, though weak associations were observed suggesting co-sedimentation of Fe(III) with at least some biomass via these aggregates, which could support diagenetic Fe(III)-reduction. Given that GSB are presumably one of the most ancient photosynthetic organisms, and pre-date cyanobacteria, our findings, on the one hand, strengthen arguments for photoferrotrophic activity as a likely mechanism for BIF deposition on a predominantly anoxic early Earth, but, on the other hand, also suggest that preservation of remnants of Fe(II)-oxidizing GSB as microfossils in the rock record is unlikely.

Redox regulation of energy transfer efficiency in antennas of green photosynthetic bacteria

NASA Technical Reports Server (NTRS)

Blankenship, R. E.; Cheng, P.; Causgrove, T. P.; Brune, D. C.; Wang, J.

1993-01-01

The efficiency of energy transfer from the peripheral chlorosome antenna structure to the membrane-bound antenna in green sulfur bacteria depends strongly on the redox potential of the medium. The fluorescence spectra and lifetimes indicate that efficient quenching pathways are induced in the chlorosome at high redox potential. The midpoint redox potential for the induction of this effect in isolated chlorosomes from Chlorobium vibrioforme is -146 mV at pH 7 (vs the normal hydrogen electrode), and the observed midpoint potential (n = 1) decreases by 60 mV per pH unit over the pH range 7-10. Extraction of isolated chlorosomes with hexane has little effect on the redox-induced quenching, indicating that the component(s) responsible for this effect are bound and not readily extractable. We have purified and partially characterized the trimeric water-soluble bacteriochlorophyll a-containing protein from the thermophilic green sulfur bacterium Chlorobium tepidum. This protein is located between the chlorosome and the membrane. Fluorescence spectra of the purified protein indicate that it also contains groups that quench excitations at high redox potential. The results indicate that the energy transfer pathway in green sulfur bacteria is regulated by redox potential. This regulation appears to operate in at least two distinct places in the energy transfer pathway, the oligomeric pigments in the interior of the chlorosome and in the bacteriochlorophyll a protein. The regulatory effect may serve to protect the cell against superoxide-induced damage when oxygen is present. By quenching excitations before they reach the reaction center, reduction and subsequent autooxidation of the low potential electron acceptors found in these organisms is avoided.

Chlorobium limicola forma thiosulfatophilum: Biocatalyst in the Production of Sulfur and Organic Carbon from a Gas Stream Containing H2S and CO2

PubMed Central

Cork, Douglas J.; Garunas, Ruta; Sajjad, Ashfaq

1983-01-01

Chlorobium limicola forma thiosulfatophilum (ATCC 17092) was grown in a 1-liter continuously stirred tank reactor (800-ml liquid volume) at pH 6.8, 30°C, saturated light intensity, and a gas flow rate of 23.6 ml/min from a gas cylinder blend consisting of 3.9 mol% H2S, 9.2 mol% CO2, 86.4 mol% N2, and 0.5 mol% H2. This is the first demonstration of photoautotrophic growth of a Chlorobium sp. on a continuous inorganic gas feed. A significant potential exists for applying this photoautotrophic process to desulfurization and CO2 fixation of gases containing acidic components (H2S and CO2). PMID:16346255

Spectroscopic studies of two spectral variants of light-harvesting complex 2 (LH2) from the photosynthetic purple sulfur bacterium Allochromatium vinosum.

PubMed

Niedzwiedzki, Dariusz M; Bina, David; Picken, Nichola; Honkanen, Suvi; Blankenship, Robert E; Holten, Dewey; Cogdell, Richard J

2012-09-01

Two spectral forms of the peripheral light-harvesting complex (LH2) from the purple sulfur photosynthetic bacterium Allochromatium vinosum were purified and their photophysical properties characterized. The complexes contain bacteriochlorophyll a (BChl a) and multiple species of carotenoids. The composition of carotenoids depends on the light conditions applied during growth of the cultures. In addition, LH2 grown under high light has a noticeable split of the B800 absorption band. The influence of the change of carotenoid distribution as well as the spectral change of the excitonic absorption of the bacteriochlorophylls on the light-harvesting ability was studied using steady-state absorption, fluorescence and femtosecond time-resolved absorption at 77K. The results demonstrate that the change of the distribution of the carotenoids when cells were grown at low light adapts the absorptive properties of the complex to the light conditions and maintains maximum photon-capture performance. In addition, an explanation for the origin of the enigmatic split of the B800 absorption band is provided. This spectral splitting is also observed in LH2 complexes from other photosynthetic sulfur purple bacterial species. According to results obtained from transient absorption spectroscopy, the B800 band split originates from two spectral forms of the associated BChl a monomeric molecules bound within the same complex. Copyright © 2012 Elsevier B.V. All rights reserved.

Biofilm Formation by a Metabolically Versatile Bacterium

DTIC Science & Technology

2005-10-02

Rhodopseudomonas palustris is a photosynthetic bacterium that has good potential to be developed as a biocatalyst for the production of hydrogen, a...A for none) Samanta, S. K and C. S. Harwood. 2005. Use of the Rhodopseudomonas palustris genome to identify a single amino acid that contributes to...operon from Rhodopseudomonas palustris mediates dicarboxylic acid degradation and participates in anaerobic benzoate degradation. Microbiology 151

Forster energy transfer in chlorosomes of green photosynthetic bacteria

NASA Technical Reports Server (NTRS)

Causgrove, T. P.; Brune, D. C.; Blankenship, R. E.

1992-01-01

Energy transfer properties of whole cells and chlorosome antenna complexes isolated from the green sulfur bacteria Chlorobium limicola (containing bacteriochlorophyll c), Chlorobium vibrioforme (containing bacteriochlorophyll d) and Pelodictyon phaeoclathratiforme (containing bacteriochlorophyll e) were measured. The spectral overlap of the major chlorosome pigment (bacteriochlorophyll c, d or, e) with the bacteriochlorophyll a B795 chlorosome baseplate pigment is greatest for bacteriochlorophyll c and smallest for bacteriochlorophyll e. The absorbance and fluorescence spectra of isolated chlorosomes were measured, fitted to gaussian curves and the overlap factors with B795 calculated. Energy transfer times from the bacteriochlorophyll c, d or e to B795 were measured in whole cells and the results interpreted in terms of the Forster theory of energy transfer.

A reverse KREBS cycle in photosynthesis: consensus at last

NASA Technical Reports Server (NTRS)

Buchanan, B. B.; Arnon, D. I.

1990-01-01

The Krebs cycle (citric acid or tricarboxylic acid cycle), the final common pathway in aerobic metabolism for the oxidation of carbohydrates, fatty acids and amino acids, is known to be irreversible. It liberates CO2 and generates NADH whose aerobic oxidation yields ATP but it does not operate in reverse as a biosynthetic pathway for CO2 assimilation. In 1966, our laboratory described a cyclic pathway for CO2 assimilation (Evans, Buchanan and Arnon 1966) that was unusual in two respects: (i) it provided the first instance of an obligate photoautotroph that assimilated CO2 by a pathway different from Calvin's reductive pentose phosphate cycle (Calvin 1962) and (ii) in its overall effect the new cycle was a reversal of the Krebs cycle. Named the 'reductive carboxylic acid cycle' (sometimes also called the reductive tricarboxylic acid cycle) the new cycle appeared to be the sole CO2 assimilation pathway in Chlorobium thiosulfatophilum (Evans et al. 1966) (now known as Chlorobium limicola forma thiosulfatophilum). Chlorobium is a photosynthetic green sulfur bacterium that grows anaerobically in an inorganic medium with sulfide and thiosulfate as electron donors and CO2 as an obligatory carbon source. In the ensuing years, the new cycle was viewed with skepticism. Not only was it in conflict with the prevailing doctrine that the 'one important property ... shared by all (our emphasis) autotrophic species is the assimilation of CO2 via the Calvin cycle' (McFadden 1973) but also some of its experimental underpinnings were challenged. It is only now that in the words of one of its early skeptics (Tabita 1988) 'a long and tortuous controversy' has ended with general acceptance of the reductive carboxylic acid cycle as a photosynthetic CO2 assimilation pathway distinct from the pentose cycle. (Henceforth, to minimize repetitiveness, the reductive pentose phosphate cycle will often be referred to as the pentose cycle and the reductive carboxylic acid cycle as the carboxylic

A reverse KREBS cycle in photosynthesis: consensus at last.

PubMed

Buchanan, B B; Arnon, D I

1990-01-01

The Krebs cycle (citric acid or tricarboxylic acid cycle), the final common pathway in aerobic metabolism for the oxidation of carbohydrates, fatty acids and amino acids, is known to be irreversible. It liberates CO2 and generates NADH whose aerobic oxidation yields ATP but it does not operate in reverse as a biosynthetic pathway for CO2 assimilation. In 1966, our laboratory described a cyclic pathway for CO2 assimilation (Evans, Buchanan and Arnon 1966) that was unusual in two respects: (i) it provided the first instance of an obligate photoautotroph that assimilated CO2 by a pathway different from Calvin's reductive pentose phosphate cycle (Calvin 1962) and (ii) in its overall effect the new cycle was a reversal of the Krebs cycle. Named the 'reductive carboxylic acid cycle' (sometimes also called the reductive tricarboxylic acid cycle) the new cycle appeared to be the sole CO2 assimilation pathway in Chlorobium thiosulfatophilum (Evans et al. 1966) (now known as Chlorobium limicola forma thiosulfatophilum). Chlorobium is a photosynthetic green sulfur bacterium that grows anaerobically in an inorganic medium with sulfide and thiosulfate as electron donors and CO2 as an obligatory carbon source. In the ensuing years, the new cycle was viewed with skepticism. Not only was it in conflict with the prevailing doctrine that the 'one important property ... shared by all (our emphasis) autotrophic species is the assimilation of CO2 via the Calvin cycle' (McFadden 1973) but also some of its experimental underpinnings were challenged. It is only now that in the words of one of its early skeptics (Tabita 1988) 'a long and tortuous controversy' has ended with general acceptance of the reductive carboxylic acid cycle as a photosynthetic CO2 assimilation pathway distinct from the pentose cycle. (Henceforth, to minimize repetitiveness, the reductive pentose phosphate cycle will often be referred to as the pentose cycle and the reductive carboxylic acid cycle as the carboxylic

Rhodobase, a meta-analytical tool for reconstructing gene regulatory networks in a model photosynthetic bacterium.

PubMed

Moskvin, Oleg V; Bolotin, Dmitry; Wang, Andrew; Ivanov, Pavel S; Gomelsky, Mark

2011-02-01

We present Rhodobase, a web-based meta-analytical tool for analysis of transcriptional regulation in a model anoxygenic photosynthetic bacterium, Rhodobacter sphaeroides. The gene association meta-analysis is based on the pooled data from 100 of R. sphaeroides whole-genome DNA microarrays. Gene-centric regulatory networks were visualized using the StarNet approach (Jupiter, D.C., VanBuren, V., 2008. A visual data mining tool that facilitates reconstruction of transcription regulatory networks. PLoS ONE 3, e1717) with several modifications. We developed a means to identify and visualize operons and superoperons. We designed a framework for the cross-genome search for transcription factor binding sites that takes into account high GC-content and oligonucleotide usage profile characteristic of the R. sphaeroides genome. To facilitate reconstruction of directional relationships between co-regulated genes, we screened upstream sequences (-400 to +20bp from start codons) of all genes for putative binding sites of bacterial transcription factors using a self-optimizing search method developed here. To test performance of the meta-analysis tools and transcription factor site predictions, we reconstructed selected nodes of the R. sphaeroides transcription factor-centric regulatory matrix. The test revealed regulatory relationships that correlate well with the experimentally derived data. The database of transcriptional profile correlations, the network visualization engine and the optimized search engine for transcription factor binding sites analysis are available at http://rhodobase.org. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Complete Genome Sequence of the Filamentous Anoxygenic Phototrophic Bacterium Chloroflexus aurantiacus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Kuo-Hsiang; Barry, Kerrie; Chertkov, Olga

Chloroflexus aurantiacus is a thermophilic filamentous anoxygenic phototrophic (FAP) bacterium, and can grow phototrophically under anaerobic conditions or chemotrophically under aerobic and dark conditions. According to 16S rRNA analysis, Chloroflexi species are the earliest branching bacteria capable of photosynthesis, and Cfl. aurantiacus has been long regarded as a key organism to resolve the obscurity of the origin and early evolution of photosynthesis. Cfl. aurantiacus contains a chimeric photosystem that comprises some characters of green sulfur bacteria and purple photosynthetic bacteria, and also has some unique electron transport proteins compared to other photosynthetic bacteria.

Different Metabolomic Responses to Carbon Starvation between Light and Dark Conditions in the Purple Photosynthetic Bacterium, Rhodopseudomonas palustris.

PubMed

Kanno, Nanako; Matsuura, Katsumi; Haruta, Shin

2018-03-29

Purple photosynthetic bacteria utilize light energy for growth. We previously demonstrated that light energy contributed to prolonging the survival of multiple purple bacteria under carbon-starved conditions. In order to clarify the effects of illumination on metabolic states under carbon-starved, non-growing conditions, we herein compared the metabolic profiles of starved cells in the light and dark using the purple bacterium, Rhodopseudomonas palustris. The metabolic profiles of starved cells in the light were markedly different from those in the dark. After starvation for 5 d in the light, cells showed increases in the amount of ATP and the NAD + /NADH ratio. Decreases in the amounts of most metabolites related to glycolysis and the TCA cycle in energy-rich starved cells suggest the active utilization of these metabolites for the modification of cellular components. Starvation in the dark induced the consumption of cellular compounds such as amino acids, indicating that the degradation of these cellular components produced ATP in order to maintain viability under energy-poor conditions. The present results suggest that intracellular energy levels alter survival strategies under carbon-starved conditions through metabolism.

THE FINE STRUCTURE OF GREEN BACTERIA

PubMed Central

Cohen-Bazire, Germaine; Pfennig, Norbert; Kunisawa, Riyo

1964-01-01

The fine structure of several strains of green bacteria belonging to the genus Chlorobium has been studied in thin sections with the electron microscope. In addition to having general cytological features typical of Gram-negative bacteria, the cells of these organisms always contain membranous mesosomal elements, connected with the cytoplasmic membrane, and an elaborate system of isolated cortical vesicles, some 300 to 400 A wide and 1000 to 1500 A long. The latter structures, chlorobium vesicles, have been isolated in a partly purified state by differential centrifugation of cell-free extracts. They are associated with a centrifugal fraction that has a very high specific chlorophyll content. In all probability, therefore, the chlorobium vesicles are the site of the photosynthetic apparatus of green bacteria. PMID:14195611

Studies on Hydrogen Production by Photosynthetic Bacteria after Anaerobic Fermentation of Starch by a Hyperthermophile, Pyrococcus furiosus

NASA Astrophysics Data System (ADS)

Sugitate, Toshihiro; Fukatsu, Makoto; Ishimi, Katsuhiro; Kohno, Hideki; Wakayama, Tatsuki; Nakamura, Yoshihiro; Miyake, Jun; Asada, Yasuo

In order to establish the sequential hydrogen production from waste starch using a hyperthermophile, Pyrococcus furiosus, and a photosynthetic bacterium, basic studies were done. P. furiosus produced hydrogen and acetate by anaerobic fermentation at 90°C. A photosynthetic bacterium, Rhodobacter sphaeroides RV, was able to produce hydrogen from acetate under anaerobic and light conditions at 30°C. However, Rb. sphaeroides RV was not able to produce hydrogen from acetate in the presence of sodium chloride that was essential for the growth and hydrogen production of P. furiosus although it produced hydrogen from lactate at a reduced rate with 1% sodium chloride. A newly isolated strain, CST-8, from natural environment was, however, able to produce hydrogen from acetate, especially with 3 mM L-alanine and in the presence of 1% sodium chloride. The sequential hydrogen production with P. furiosus and salt-tolerant photosynthetic bacteria could be probable at least in the laboratory experiment scale.

X-ray crystallographic analysis of the sulfur carrier protein SoxY from Chlorobium limicola f. thiosulfatophilum reveals a tetrameric structure

PubMed Central

Stout, Jan; Van Driessche, Gonzalez; Savvides, Savvas N.; Van Beeumen, Jozef

2007-01-01

Dissimilatory oxidation of thiosulfate in the green sulfur bacterium Chlorobium limicola f. thiosulfatophilum is carried out by the ubiquitous sulfur-oxidizing (Sox) multi-enzyme system. In this system, SoxY plays a key role, functioning as the sulfur substrate-binding protein that offers its sulfur substrate, which is covalently bound to a conserved C-terminal cysteine, to another oxidizing Sox enzyme. Here, we report the crystal structures of a stand-alone SoxY protein of C. limicola f. thiosulfatophilum, solved at 2.15 Å and 2.40 Å resolution using X-ray diffraction data collected at 100 K and room temperature, respectively. The structure reveals a monomeric Ig-like protein, with an N-terminal α-helix, that oligomerizes into a tetramer via conserved contact regions between the monomers. The tetramer can be described as a dimer of dimers that exhibits one large hydrophobic contact region in each dimer and two small hydrophilic interface patches in the tetramer. At the tetramer interface patch, two conserved redox-active C-terminal cysteines form an intersubunit disulfide bridge. Intriguingly, SoxY exhibits a dimer/tetramer equilibrium that is dependent on the redox state of the cysteines and on the type of sulfur substrate component bound to them. Taken together, the dimer/tetramer equilibrium, the specific interactions between the subunits in the tetramer, and the significant conservation level of the interfaces strongly indicate that these SoxY oligomers are biologically relevant. PMID:17327392

Characterisation of the LH2 spectral variants produced by the photosynthetic purple sulphur bacterium Allochromatium vinosum.

PubMed

Carey, Anne-Marie; Hacking, Kirsty; Picken, Nichola; Honkanen, Suvi; Kelly, Sharon; Niedzwiedzki, Dariusz M; Blankenship, Robert E; Shimizu, Yuuki; Wang-Otomo, Zheng-Yu; Cogdell, Richard J

2014-11-01

This study systematically investigated the different types of LH2 produced by Allochromatium (Alc.) vinosum, a photosynthetic purple sulphur bacterium, in response to variations in growth conditions. Three different spectral forms of LH2 were isolated and purified, the B800-820, B800-840 and B800-850 LH2 types, all of which exhibit an unusual split 800 peak in their low temperature absorption spectra. However, it is likely that more forms are also present. Relatively more B800-820 and B800-840 are produced under low light conditions, while relatively more B800-850 is produced under high light conditions. Polypeptide compositions of the three different LH2 types were determined by a combination of HPLC and TOF/MS. The B800-820, B800-840 and B800-850 LH2 types all have a heterogeneous polypeptide composition, containing multiple types of both α and β polypeptides, and differ in their precise polypeptide composition. They all have a mixed carotenoid composition, containing carotenoids of the spirilloxanthin series. In all cases the most abundant carotenoid is rhodopin; however, there is a shift towards carotenoids with a higher conjugation number in LH2 complexes produced under low light conditions. CD spectroscopy, together with the polypeptide analysis, demonstrates that these Alc. vinosum LH2 complexes are more closely related to the LH2 complex from Phs. molischianum than they are to the LH2 complexes from Rps. acidophila. Copyright © 2014. Published by Elsevier B.V.

Biohydrogen production in a continuous stirred tank bioreactor from synthesis gas by anaerobic photosynthetic bacterium: Rhodopirillum rubrum.

PubMed

Younesi, Habibollah; Najafpour, Ghasem; Ku Ismail, Ku Syahidah; Mohamed, Abdul Rahman; Kamaruddin, Azlina Harun

2008-05-01

Hydrogen may be considered a potential fuel for the future since it is carbon-free and oxidized to water as a combustion product. Bioconversion of synthesis gas (syngas) to hydrogen was demonstrated in continuous stirred tank bioreactor (CSTBR) utilizing acetate as a carbon source. An anaerobic photosynthetic bacterium, Rhodospirillum rubrum catalyzed water-gas shift reaction which was applied for the bioconversion of syngas to hydrogen. The continuous fermentation of syngas in the bioreactor was continuously operated at various gas flow rates and agitation speeds, for the period of two months. The gas flow rates were varied from 5 to 14 ml/min. The agitation speeds were increasingly altered in the range of 150-500 rpm. The pH and temperature of the bioreactor was set at 6.5 and 30 degrees C. The liquid flow rate was kept constant at 0.65 ml/min for the duration of 60 days. The inlet acetate concentration was fed at 4 g/l into the bioreactor. The hydrogen production rate and yield were 16+/-1.1 mmol g(-1)cell h(-1) and 87+/-2.4% at fixed agitation speed of 500 rpm and syngas flow rate of 14 ml/min, respectively. The mass transfer coefficient (KLa) at this condition was approximately 72.8h(-1). This new approach, using a biocatalyst was considered as an alternative method of conventional Fischer-Tropsch synthetic reactions, which were able to convert syngas into hydrogen.

Metabolic analysis of Chlorobium chlorochromatii CaD3 reveals clues of the symbiosis in ‘Chlorochromatium aggregatum'.

PubMed Central

Cerqueda-García, Daniel; Martínez-Castilla, León P; Falcón, Luisa I; Delaye, Luis

2014-01-01

A symbiotic association occurs in ‘Chlorochromatium aggregatum', a phototrophic consortium integrated by two species of phylogenetically distant bacteria composed by the green-sulfur Chlorobium chlorochromatii CaD3 epibiont that surrounds a central β-proteobacterium. The non-motile chlorobia can perform nitrogen and carbon fixation, using sulfide as electron donors for anoxygenic photosynthesis. The consortium can move due to the flagella present in the central β-protobacterium. Although Chl. chlorochromatii CaD3 is never found as free-living bacteria in nature, previous transcriptomic and proteomic studies have revealed that there are differential transcription patterns between the symbiotic and free-living status of Chl. chlorocromatii CaD3 when grown in laboratory conditions. The differences occur mainly in genes encoding the enzymatic reactions involved in nitrogen and amino acid metabolism. We performed a metabolic reconstruction of Chl. chlorochromatii CaD3 and an in silico analysis of its amino acid metabolism using an elementary flux modes approach (EFM). Our study suggests that in symbiosis, Chl. chlorochromatii CaD3 is under limited nitrogen conditions where the GS/GOGAT (glutamine synthetase/glutamate synthetase) pathway is actively assimilating ammonia obtained via N2 fixation. In contrast, when free-living, Chl. chlorochromatii CaD3 is in a condition of nitrogen excess and ammonia is assimilated by the alanine dehydrogenase (AlaDH) pathway. We postulate that ‘Chlorochromatium aggregatum' originated from a parasitic interaction where the N2 fixation capacity of the chlorobia would be enhanced by injection of 2-oxoglutarate from the β-proteobacterium via the periplasm. This consortium would have the advantage of motility, which is fundamental to a phototrophic bacterium, and the syntrophy of nitrogen and carbon sources. PMID:24285361

Nonphotochemical Hole-Burning Studies of Energy Transfer Dynamics in Antenna Complexes of Photosynthetic Bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuzaki, Satoshi

2001-01-01

This thesis contains the candidate's original work on excitonic structure and energy transfer dynamics of two bacterial antenna complexes as studied using spectral hole-burning spectroscopy. The general introduction is divided into two chapters (1 and 2). Chapter 1 provides background material on photosynthesis and bacterial antenna complexes with emphasis on the two bacterial antenna systems related to the thesis research. Chapter 2 reviews the underlying principles and mechanism of persistent nonphotochemical hole-burning (NPHB) spectroscopy. Relevant energy transfer theories are also discussed. Chapters 3 and 4 are papers by the candidate that have been published. Chapter 3 describes the application ofmore » NPHB spectroscopy to the Fenna-Matthews-Olson (FMO) complex from the green sulfur bacterium Prosthecochloris aestuarii; emphasis is on determination of the low energy vibrational structure that is important for understanding the energy transfer process associated within three lowest energy Q y-states of the complex. The results are compared with those obtained earlier on the FMO complex from Chlorobium tepidum. In Chapter 4, the energy transfer dynamics of the B800 molecules of intact LH2 and B800-deficient LH2 complexes of the purple bacterium Rhodopseudomonas acidophila are compared. New insights on the additional decay channel of the B800 ring of bacteriochlorophyll a (BChl a) molecules are provided. General conclusions are given in Chapter 5. A version of the hole spectrum simulation program written by the candidate for the FMO complex study (Chapter 3) is included as an appendix. The references for each chapter are given at the end of each chapter.« less

Production and Consumption of Hydrogen in Hot Spring Microbial Mats Dominated by a Filamentous Anoxygenic Photosynthetic Bacterium

PubMed Central

Otaki, Hiroyo; Everroad, R. Craig; Matsuura, Katsumi; Haruta, Shin

2012-01-01

Microbial mats containing the filamentous anoxygenic photosynthetic bacterium Chloroflexus aggregans develop at Nakabusa hot spring in Japan. Under anaerobic conditions in these mats, interspecies interaction between sulfate-reducing bacteria as sulfide producers and C. aggregans as a sulfide consumer has been proposed to constitute a sulfur cycle; however, the electron donor utilized for microbial sulfide production at Nakabusa remains to be identified. In order to determine this electron donor and its source, ex situ experimental incubation of mats was explored. In the presence of molybdate, which inhibits biological sulfate reduction, hydrogen gas was released from mat samples, indicating that this hydrogen is normally consumed as an electron donor by sulfate-reducing bacteria. Hydrogen production decreased under illumination, indicating that C. aggregans also functions as a hydrogen consumer. Small amounts of hydrogen may have also been consumed for sulfur reduction. Clone library analysis of 16S rRNA genes amplified from the mats indicated the existence of several species of hydrogen-producing fermentative bacteria. Among them, the most dominant fermenter, Fervidobacterium sp., was successfully isolated. This isolate produced hydrogen through the fermentation of organic carbon. Dispersion of microbial cells in the mats resulted in hydrogen production without the addition of molybdate, suggesting that simultaneous production and consumption of hydrogen in the mats requires dense packing of cells. We propose a cyclic electron flow within the microbial mats, i.e., electron flow occurs through three elements: S (elemental sulfur, sulfide, sulfate), C (carbon dioxide, organic carbon) and H (di-hydrogen, protons). PMID:22446313

Photosynthetic functions of Synechococcus in the ocean microbiomes of diverse salinity and seasons.

PubMed

Kim, Yihwan; Jeon, Jehyun; Kwak, Min Seok; Kim, Gwang Hoon; Koh, InSong; Rho, Mina

2018-01-01

Synechococcus is an important photosynthetic picoplankton in the temperate to tropical oceans. As a photosynthetic bacterium, Synechococcus has an efficient mechanism to adapt to the changes in salinity and light intensity. The analysis of the distributions and functions of such microorganisms in the ever changing river mouth environment, where freshwater and seawater mix, should help better understand their roles in the ecosystem. Toward this objective, we have collected and sequenced the ocean microbiome in the river mouth of Kwangyang Bay, Korea, as a function of salinity and temperature. In conjunction with comparative genomics approaches using the sequenced genomes of a wide phylogeny of Synechococcus, the ocean microbiome was analyzed in terms of their composition and clade-specific functions. The results showed significant differences in the compositions of Synechococcus sampled in different seasons. The photosynthetic functions in such enhanced Synechococcus strains were also observed in the microbiomes in summer, which is significantly different from those in other seasons.

The death mechanism of the harmful algal bloom species Alexandrium tamarense induced by algicidal bacterium Deinococcus sp. Y35

PubMed Central

Li, Yi; Zhu, Hong; Lei, Xueqian; Zhang, Huajun; Cai, Guanjing; Chen, Zhangran; Fu, Lijun; Xu, Hong; Zheng, Tianling

2015-01-01

Harmful algal blooms (HABs) cause a variety of deleterious effects on aquatic ecosystems, especially the toxic dinoflagellate Alexandrium tamarense, which poses a serious threat to marine economic and human health based on releasing paralytic shellfish poison into the environment. The algicidal bacterium Deinococcus sp. Y35 which can induce growth inhibition on A. tamarense was used to investigate the functional mechanism. The growth status, reactive oxygen species (ROS) content, photosynthetic system and the nuclear system of algal cells were determined under algicidal activity. A culture of strain Y35 not only induced overproduction of ROS in algal cells within only 0.5 h of treatment, also decrease the total protein content as well as the response of the antioxidant enzyme. Meanwhile, lipid peroxidation was induced and cell membrane integrity was lost. Photosynthetic pigments including chlorophyll a and carotenoid decreased along with the photosynthetic efficiency being significantly inhibited. At the same time, photosynthesis-related gene expression showed down-regulation. More than, the destruction of cell nuclear structure and inhibition of proliferating cell nuclear antigen (PCNA) related gene expression were confirmed. The potential functional mechanism of the algicidal bacterium on A. tamarense was investigated and provided a novel viewpoint which could be used in HABs control. PMID:26441921

The death mechanism of the harmful algal bloom species Alexandrium tamarense induced by algicidal bacterium Deinococcus sp. Y35.

PubMed

Li, Yi; Zhu, Hong; Lei, Xueqian; Zhang, Huajun; Cai, Guanjing; Chen, Zhangran; Fu, Lijun; Xu, Hong; Zheng, Tianling

2015-01-01

Harmful algal blooms (HABs) cause a variety of deleterious effects on aquatic ecosystems, especially the toxic dinoflagellate Alexandrium tamarense, which poses a serious threat to marine economic and human health based on releasing paralytic shellfish poison into the environment. The algicidal bacterium Deinococcus sp. Y35 which can induce growth inhibition on A. tamarense was used to investigate the functional mechanism. The growth status, reactive oxygen species (ROS) content, photosynthetic system and the nuclear system of algal cells were determined under algicidal activity. A culture of strain Y35 not only induced overproduction of ROS in algal cells within only 0.5 h of treatment, also decrease the total protein content as well as the response of the antioxidant enzyme. Meanwhile, lipid peroxidation was induced and cell membrane integrity was lost. Photosynthetic pigments including chlorophyll a and carotenoid decreased along with the photosynthetic efficiency being significantly inhibited. At the same time, photosynthesis-related gene expression showed down-regulation. More than, the destruction of cell nuclear structure and inhibition of proliferating cell nuclear antigen (PCNA) related gene expression were confirmed. The potential functional mechanism of the algicidal bacterium on A. tamarense was investigated and provided a novel viewpoint which could be used in HABs control.

The genetic basis of anoxygenic photosynthetic arsenite oxidation

USGS Publications Warehouse

Hernandez-Maldonado, Jamie; Sanchez-Sedillo, Benjamin; Stoneburner, Brendon; Boren, Alison; Miller, Laurence G.; McCann, Shelley; Rosen, Michael R.; Oremland, Ronald S.; Saltikov, Chad W.

2017-01-01

“Photoarsenotrophy”, the use of arsenite as an electron donor for anoxygenic photosynthesis, is thought to be an ancient form of phototrophy along with the photosynthetic oxidation of Fe(II), H2S, H2, and NO2-. Photoarsenotrophy was recently identified from Paoha Island's (Mono Lake, CA) arsenic-rich hot springs. The genomes of several photoarsenotrophs revealed a gene cluster, arxB2AB1CD, where arxA is predicted to encode for the sole arsenite oxidase. The role of arxA in photosynthetic arsenite oxidation was confirmed by disrupting the gene in a representative photoarsenotrophic bacterium, resulting in the loss of light-dependent arsenite oxidation. In situ evidence of active photoarsenotrophic microbes was supported by arxA mRNA detection for the first time, in red-pigmented microbial mats within the hot springs of Paoha Island. This work expands on the genetics for photosynthesis coupled to new electron donors and elaborates on known mechanisms for arsenic metabolism, thereby highlighting the complexities of arsenic biogeochemical cycling.

Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation

PubMed Central

Oka, Hisaki

2016-01-01

Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature. PMID:27173144

Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation

NASA Astrophysics Data System (ADS)

Oka, Hisaki

2016-05-01

Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature.

Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation.

PubMed

Oka, Hisaki

2016-05-13

Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature.

[Pigments of green sulfur bacteria isolated from reservoirs of Iavoriv sulfur deposit].

PubMed

Baran, I M; Hudz', S P; Hnatush, S O; Fedorovych, A M

2004-01-01

The enormous amount of hydrogen sulfide (up to 11 mg/ml) is present in the Yavoriv sulfur deposit reservoirs owing to sulfur reductive bacteria activity. As a consequence the ecological situation is badly affected and requires recovering. The biological H2S decomposition by photosynthetic sulfur bacteria, which use the hydrogen sulfide as electron donor during photosynthesis, can be one of the possible ways of this toxic substance destruction. The qualitative and quantitative analysis of photosynthetic pigments composition that derived from green photosynthesizing sulfur bacteria from reservoirs of Yavoriv sulfur deposit is carried out. It was fixed that Pelodictyon sp., Chlorobium sp. and isolated consortia "Pelochromatium sp." contain the bacteriochlorophyll c and d. All the isolated cultures contained bacteriochlorophyll a in trace amounts. The obtained photosynthetic pigments (bacteriochlorophylls, carotenoids) were recognized by their absorption spectra in the visible and far-red region and by their quantity. The difference was not essential. All investigated cultures of isolated bacteria contain some carotenoid the Chlorobium sp. and obtained consortia possesses isorenieratene. The absorption maxima of extracted pigments from young cultures of isolated green sulfur bacteria are more definitely displayed than those from old cultures. Investigations of phototrophic sulfur bacteria were carried out in Ukraine up to now. Ecological problem that occurred in the Yavoriv sulfur deposit as a result of the deposit exploitation caused a necessity of the investigation of photosynthetic sulfur bacteria and bacterial photosynthesis mechanism. The photosynthetic pigments nature identification will promote the fast and precise identification of the new forms of photosynthetic sulfur bacteria and will extend our knowledge about their role in the anoxygenic photosynthesis.

Genes, Genomes, and Assemblages of Modern Anoxygenic Photosynthetic Cyanobacteria as Proxies for Ancient Cyanobacteria

NASA Astrophysics Data System (ADS)

Grim, S. L.; Dick, G.

2015-12-01

Oxygenic photosynthetic (OP) cyanobacteria were responsible for the production of O2 during the Proterozoic. However, the extent and degree of oxygenation of the atmosphere and oceans varied for over 2 Ga after OP cyanobacteria first appeared in the geologic record. Cyanobacteria capable of anoxygenic photosynthesis (AP) may have altered the trajectory of oxygenation, yet the scope of their role in the Proterozoic is not well known. Modern cyanobacterial populations from Middle Island Sinkhole (MIS), Michigan and a handful of cultured cyanobacterial strains, are capable of OP and AP. With their metabolic versatility, these microbes may approximate ancient cyanobacterial assemblages that mediated Earth's oxygenation. To better characterize the taxonomic and genetic signatures of these modern AP/OP cyanobacteria, we sequenced 16S rRNA genes and conducted 'omics analyses on cultured strains, lab mesocosms, and MIS cyanobacterial mat samples collected over multiple years from May to September. Diversity in the MIS cyanobacterial mat is low, with one member of Oscillatoriales dominating at all times. However, Planktothrix members are more abundant in the cyanobacterial community in late summer and fall. The shift in cyanobacterial community composition may be linked to seasonally changing light intensity. In lab mesocosms of MIS microbial mat, we observed a shift in dominant cyanobacterial groups as well as the emergence of Chlorobium, bacteria that specialize in AP. These shifts in microbial community composition and metabolism are likely in response to changing environmental parameters such as the availability of light and sulfide. Further research is needed to understand the impacts of the changing photosynthetic community on oxygen production and the entire microbial consortium. Our study connects genes and genomes of AP cyanobacteria to their environment, and improves understanding of cyanobacterial metabolic strategies that may have shaped Earth's redox evolution.

Photoenergy Harvesting Organic PV Cells Using Modified Photosynthetic Light-Harvesting Complex for Energy Harvesting Materials

DTIC Science & Technology

2008-07-03

complex is still unclear even in the crystal structure of RC-LH1 core complex from Rhodopseudomonas (Rps.) palustris [1]. In this study, we use a...complex of R. palustris . 16 The NIR absorption spectra of these core complexes on the electrode indicate that these complexes are stable when...as the LH or the core complex. For example, the core complex, isolated from the photosynthetic bacterium, Rps. palustris , was successfully

Photosynthetic inhibition and oxidative stress to the toxic Phaeocystis globosa caused by a diketopiperazine isolated from products of algicidal bacterium metabolism.

PubMed

Tan, Shuo; Hu, Xiaoli; Yin, Pinghe; Zhao, Ling

2016-05-01

Algicidal bacteria have been turned out to be available for inhibiting Phaeocystis globosa which frequently caused harmful algal blooms and threatened to economic development and ecological balance. A marine bacterium Bacillus sp. Ts-12 exhibited significant algicidal activity against P. globosa by indirect attack. In present study, an algicidal compound was isolated by silica gel column, Sephadex G-15 column and HPLC, further identified as hexahydropyrrolo[1,2-a]pyrazine-1,4-dione, cyclo-(Pro-Gly), by GC-MS and (1)H-NMR. Cyclo-(Pro-Gly) significantly increased the level of reactive oxygen species (ROS) within P. globosa cells, further activating the enzymatic and non-enzymatic antioxidant systems, including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and ascorbic acid (AsA). The increase in methane dicarboxylic aldehyde (MDA) content showed that the surplus ROS induced lipid peroxidation on membrane system. Transmission electron microscope (TEM) and flow cytometry (FCM) analysis revealed that cyclo-(Pro-Gly) caused reduction of Chl-a content, destruction of cell membrane integrity, chloroplasts and nuclear structure. Real-time PCR assay showed that the transcriptions of photosynthesis related genes (psbA, psbD, rbcL) were significantly inhibited. This study indicated that cyclo-(Pro-Gly) from marine Bacillus sp. Ts-12 exerted photosynthetic inhibition and oxidative stress to P. globosa and eventually led to the algal cells lysis. This algicidal compound might be potential bio-agent for controlling P. globosa red tide.

Unifying principles in homodimeric type I photosynthetic reaction centers: properties of PscB and the FA, FB and FX iron-sulfur clusters in green sulfur bacteria.

PubMed

Jagannathan, Bharat; Golbeck, John H

2008-12-01

The photosynthetic reaction center from the green sulfur bacterium Chlorobium tepidum (CbRC) was solubilized from membranes using Triton X-100 and isolated by sucrose density ultra-centrifugation. The CbRC complexes were subsequently treated with 0.5 M NaCl and ultrafiltered over a 100 kDa cutoff membrane. The resulting CbRC cores did not exhibit the low-temperature EPR resonances from FA- and FB- and were unable to reduce NADP+. SDS-PAGE and mass spectrometric analysis showed that the PscB subunit, which harbors the FA and FB clusters, had become dissociated, and was now present in the filtrate. Attempts to rebind PscB onto CbRC cores were unsuccessful. Mössbauer spectroscopy showed that recombinant PscB contains a heterogeneous mixture of [4Fe-4S]2+,1+ and other types of Fe/S clusters tentatively identified as [2Fe-2S]2+,1+ clusters and rubredoxin-like Fe3+,2+ centers, and that the [4Fe-4S]2+,1+ clusters which were present were degraded at high ionic strength. Quantitative analysis confirmed that the amount of iron and sulfide in the recombinant protein was sub-stoichiometric. A heme-staining assay indicated that cytochrome c551 remained firmly attached to the CbRC cores. Low-temperature EPR spectroscopy of photoaccumulated CbRC complexes and CbRC cores showed resonances between g=5.4 and 4.4 assigned to a S=3/2 ground spin state [4Fe-4S]1+ cluster and at g=1.77 assigned to a S=1/2 ground spin state [4Fe-4S]1+ cluster, both from FX-. These results unify the properties of the acceptor side of the Type I homodimeric reaction centers found in green sulfur bacteria and heliobacteria: in both, the FA and FB iron-sulfur clusters are present on a salt-dissociable subunit, and FX is present as an interpolypeptide [4Fe-4S]2+,1+ cluster with a significant population in a S=3/2 ground spin state.

Spectroscopic and Thermodynamic Characterization of the Metal-Binding Sites in the LH1-RC Complex from Thermophilic Photosynthetic Bacterium Thermochromatium tepidum.

PubMed

Kimura, Yukihiro; Yura, Yuki; Hayashi, Yusuke; Li, Yong; Onoda, Moe; Yu, Long-Jiang; Wang-Otomo, Zheng-Yu; Ohno, Takashi

2016-12-15

The light-harvesting 1 reaction center (LH1-RC) complex from thermophilic photosynthetic bacterium Thermochromatium (Tch.) tepidum exhibits enhanced thermostability and an unusual LH1 Q y transition, both induced by Ca 2+ binding. In this study, metal-binding sites and metal-protein interactions in the LH1-RC complexes from wild-type (B915) and biosynthetically Sr 2+ -substituted (B888) Tch. tepidum were investigated by isothermal titration calorimetry (ITC), atomic absorption (AA), and attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopies. The ITC measurements revealed stoichiometric ratios of approximately 1:1 for binding of Ca 2+ , Sr 2+ , or Ba 2+ to the LH1 αβ-subunit, indicating the presence of 16 binding sites in both B915 and B888. The AA analysis provided direct evidence for Ca 2+ and Sr 2+ binding to B915 and B888, respectively, in their purified states. Metal-binding experiments supported that Ca 2+ and Sr 2+ (or Ba 2+ ) competitively associate with the binding sites in both species. The ATR-FTIR difference spectra upon Ca 2+ depletion and Sr 2+ substitution demonstrated that dissociation and binding of Ca 2+ are predominantly responsible for metal-dependent conformational changes of B915 and B888. The present results are largely compatible with the recent structural evidence that another binding site for Sr 2+ (or Ba 2+ ) exists in the vicinity of the Ca 2+ -binding site, a part of which is shared in both metal-binding sites.

Genome sequence of the photoarsenotrophic bacterium Ectothiorhodospira sp. strain BSL-9, isolated from a hypersaline alkaline arsenic-rich extreme environment

USGS Publications Warehouse

Hernandez-Maldonado, Jaime; Stoneburner, Brendon; Boren, Alison; Miller, Laurence; Rosen, Michael R.; Oremland, Ronald S.; Saltikov, Chad W

2016-01-01

The full genome sequence of Ectothiorhodospira sp. strain BSL-9 is reported here. This purple sulfur bacterium encodes an arxA-type arsenite oxidase within the arxB2AB1CD gene island and is capable of carrying out “photoarsenotrophy” anoxygenic photosynthetic arsenite oxidation. Its genome is composed of 3.5 Mb and has approximately 63% G+C content.

Isolation and Characterization of Canthaxanthin Biosynthesis Genes from the Photosynthetic Bacterium Bradyrhizobium sp. Strain ORS278

PubMed Central

Hannibal, Laure; Lorquin, Jean; D'Ortoli, Nicolas Angles; Garcia, Nelly; Chaintreuil, Clemence; Masson-Boivin, Catherine; Dreyfus, Bernard; Giraud, Eric

2000-01-01

A carotenoid biosynthesis gene cluster involved in canthaxanthin production was isolated from the photosynthetic Bradyrhizobium sp. strain ORS278. This cluster includes five genes identified as crtE, crtY, crtI, crtB, and crtW that are organized in at least two operons. The functional assignment of each open reading frame was confirmed by complementation studies. PMID:10851005

A monogalactosyldiacylglycerol synthase found in the green sulfur bacterium Chlorobaculum tepidum reveals important roles for galactolipids in photosynthesis.

PubMed

Masuda, Shinji; Harada, Jiro; Yokono, Makio; Yuzawa, Yuichi; Shimojima, Mie; Murofushi, Kazuhiro; Tanaka, Hironori; Masuda, Hanako; Murakawa, Masato; Haraguchi, Tsuyoshi; Kondo, Maki; Nishimura, Mikio; Yuasa, Hideya; Noguchi, Masato; Oh-Oka, Hirozo; Tanaka, Ayumi; Tamiaki, Hitoshi; Ohta, Hiroyuki

2011-07-01

Monogalactosyldiacylglycerol (MGDG), which is conserved in almost all photosynthetic organisms, is the most abundant natural polar lipid on Earth. In plants, MGDG is highly accumulated in the chloroplast membranes and is an important bulk constituent of thylakoid membranes. However, precise functions of MGDG in photosynthesis have not been well understood. Here, we report a novel MGDG synthase from the green sulfur bacterium Chlorobaculum tepidum. This enzyme, MgdA, catalyzes MGDG synthesis using UDP-Gal as a substrate. The gene encoding MgdA was essential for this bacterium; only heterozygous mgdA mutants could be isolated. An mgdA knockdown mutation affected in vivo assembly of bacteriochlorophyll c aggregates, suggesting the involvement of MGDG in the construction of the light-harvesting complex called chlorosome. These results indicate that MGDG biosynthesis has been independently established in each photosynthetic organism to perform photosynthesis under different environmental conditions. We complemented an Arabidopsis thaliana MGDG synthase mutant by heterologous expression of MgdA. The complemented plants showed almost normal levels of MGDG, although they also had abnormal morphological phenotypes, including reduced chlorophyll content, no apical dominance in shoot growth, atypical flower development, and infertility. These observations provide new insights regarding the importance of regulated MGDG synthesis in the physiology of higher plants.

Interactions between colloidal silver and photosynthetic pigments located in cyanobacteria fragments and in solution.

PubMed

Siejak, Przemysław; Frackowiak, Danuta

2007-09-25

Changes in the yield of the fluorescence emitted by pigments of photosynthetic organisms could be used for the establishment of the presence of some toxic substances. The presence of colloidal metals can be indicated by enhancement of pigments' emission as a result of plasmons generation. The spectra of the pigments of cyanobacterium Synechocystis located in the bacterium fragments and in solutions with and without colloidal silver additions have been measured. The quantum yield of the pigments' fluorescence in solution has been observed to increase at some wavelength of excitation, while the fluorescence of the pigments in the bacteria fragments has been only quenched as a consequence of interactions with colloidal silver particles. Close contact between pigment molecules located in bacteria fragments and silver particles is probably not possible. We plan in future to investigate the influence of other, more typical metal pollutants of water, using similar spectral methods and several other photosynthetic bacteria pigments, in solution, in cell fragments and in the whole bacteria organisms.

Conserved enzymes mediate the early reactions of carotenoid biosynthesis in nonphotosynthetic and photosynthetic prokaryotes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armstrong, G.A.; Hearst, J.E.; Alberti, M.

1990-12-01

Carotenoids comprise one of the most widespread classes of pigments found in nature. The first reactions of C{sub 40} carotenoid biosynthesis proceed through common intermediates in all organisms, suggesting the evolutionary conservation of early enzymes from this pathway. The authors report here the nucleotide sequence of three genes from the carotenoid biosynthesis gene cluster of Erwinia herbicola, a nonphotosynthetic epiphytic bacterium, which encode homologs of the CrtB, CrtE, and CrtI proteins of Rhodobacter capsulatus, a purple nonsulfur photosynthetic bacterium. CrtB (prephytoene pyrophosphate synthase), CrtE (phytoene synthase), and CrtI (phytoene dehydrogenase) are required for the first three reactions specific to themore » carotenoid branch of general isoprenoid metabolism. All three dehydrogenases possess a hydrophobic N-terminal domain containing a putative ADP-binding {beta}{alpha}{beta} fold characteristic of enzymes known to bind FAD or NAD(P) cofactors. These data indicate the structural conservation of early carotenoid biosynthesis enzymes in evolutionary diverse organisms.« less

Quantitative measurement of the growth rate of the PHA-producing photosynthetic bacterium Rhodocyclus gelatinous CBS-2[PolyHydroxyAlkanoate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfrum, E.J.; Weaver, P.F.

Researchers at the National Renewable Energy Laboratory (NREL) have been investigating the use of model photosynthetic microorganisms that use sunlight and two-carbon organic substrates (e.g., ethanol, acetate) to produce biodegradable polyhydroxyalkanoate (PHA) copolymers as carbon storage compounds. Use of these biological PHAs in single-use plastics applications, followed by their post-consumer composting or anaerobic digestion, could impact petroleum consumption as well as the overloading of landfills. The large-scale production of PHA polymers by photosynthetic bacteria will require large-scale reactor systems utilizing either sunlight or artificial illumination. The first step in the scale-up process is to quantify the microbial growth rates andmore » the PHA production rates as a function of reaction conditions such as nutrient concentration, temperature, and light quality and intensity.« less

Single Upconversion Nanoparticle-Bacterium Cotrapping for Single-Bacterium Labeling and Analysis.

PubMed

Xin, Hongbao; Li, Yuchao; Xu, Dekang; Zhang, Yueli; Chen, Chia-Hung; Li, Baojun

2017-04-01

Detecting and analyzing pathogenic bacteria in an effective and reliable manner is crucial for the diagnosis of acute bacterial infection and initial antibiotic therapy. However, the precise labeling and analysis of bacteria at the single-bacterium level are a technical challenge but very important to reveal important details about the heterogeneity of cells and responds to environment. This study demonstrates an optical strategy for single-bacterium labeling and analysis by the cotrapping of single upconversion nanoparticles (UCNPs) and bacteria together. A single UCNP with an average size of ≈120 nm is first optically trapped. Both ends of a single bacterium are then trapped and labeled with single UCNPs emitting green light. The labeled bacterium can be flexibly moved to designated locations for further analysis. Signals from bacteria of different sizes are detected in real time for single-bacterium analysis. This cotrapping method provides a new approach for single-pathogenic-bacterium labeling, detection, and real-time analysis at the single-particle and single-bacterium level. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Extracellular production of tellurium nanoparticles by the photosynthetic bacterium Rhodobacter capsulatus.

PubMed

Borghese, Roberto; Brucale, Marco; Fortunato, Gianuario; Lanzi, Massimiliano; Mezzi, Alessio; Valle, Francesco; Cavallini, Massimiliano; Zannoni, Davide

2016-05-15

The toxic oxyanion tellurite (TeO3(2-)) is acquired by cells of Rhodobacter capsulatus grown anaerobically in the light, via acetate permease ActP2 and then reduced to Te(0) in the cytoplasm as needle-like black precipitates. Interestingly, photosynthetic cultures of R. capsulatus can also generate Te(0) nanoprecipitates (TeNPs) outside the cells upon addition of the redox mediator lawsone (2-hydroxy-1,4-naphtoquinone). TeNPs generation kinetics were monitored to define the optimal conditions to produce TeNPs as a function of various carbon sources and lawsone concentration. We report that growing cultures over a 10 days period with daily additions of 1mM tellurite led to the accumulation in the growth medium of TeNPs with dimensions from 200 up to 600-700 nm in length as determined by atomic force microscopy (AFM). This result suggests that nucleation of TeNPs takes place over the entire cell growth period although the addition of new tellurium Te(0) to pre-formed TeNPs is the main strategy used by R. capsulatus to generate TeNPs outside the cells. Finally, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) analysis of TeNPs indicate they are coated with an organic material which keeps the particles in solution in aqueous solvents. Copyright © 2016 Elsevier B.V. All rights reserved.

Developing Research Capabilities in Energy Biosciences: Design principles of photosynthetic biofuel production.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donald D. Brown; David Savage

2012-06-30

The current fossil fuel-based energy infrastructure is not sustainable. Solar radiation is a plausible alternative, but realizing it as such will require significant technological advances in the ability to harvest light energy and convert it into suitable fuels. The biological system of photosynthesis can carry out these reactions, and in principle could be engineered using the tools of synthetic biology. One desirable implementation would be to rewire the reactions of a photosynthetic bacterium to direct the energy harvested from solar radiation into the synthesis of the biofuel H2. Proposed here is a series of experiments to lay the basic sciencemore » groundwork for such an attempt. The goal is to elucidate the transcriptional network of photosynthesis using a novel driver-reporter screen, evolve more robust hydrogenases for improved catalysis, and to test the ability of the photosynthetic machinery to directly produce H2 in vivo. The results of these experiments will have broad implications for the understanding of photosynthesis, enzyme function, and the engineering of biological systems for sustainable energy production. The ultimate impact could be a fundamental transformation of the world's energy economy.« less

The reaction center is the sensitive target of the mercury(II) ion in intact cells of photosynthetic bacteria.

PubMed

Asztalos, Emese; Sipka, Gábor; Kis, Mariann; Trotta, Massimo; Maróti, Péter

2012-06-01

The sensitivity of intact cells of purple photosynthetic bacterium Rhodobacter sphaeroides wild type to low level (<100 μM) of mercury (Hg²⁺) contamination was evaluated by absorption and fluorescence spectroscopies of the bacteriochlorophyll-protein complexes. All assays related to the function of the reaction center (RC) protein (induction of the bacteriochlorophyll fluorescence, delayed fluorescence and light-induced oxidation and reduction of the bacteriochlorophyll dimer and energization of the photosynthetic membrane) showed prompt and later effects of the mercury ions. The damage expressed by decrease of the magnitude and changes of rates of the electron transfer kinetics followed complex (spatial and temporal) pattern according to the different Hg²⁺ sensitivities of the electron transport (donor/acceptor) sites including the reduced bound and free cytochrome c₂ and the primary reduced quinone. In contrast to the RC, the light harvesting system and the bc₁ complex demonstrated much higher resistance against the mercury pollution. The 850 and 875 nm components of the peripheral and core complexes were particularly insensitive to the mercury(II) ions. The concentration of the photoactive RCs and the connectivity of the photosynthetic units decreased upon mercury treatment. The degree of inhibition of the photosynthetic apparatus was always higher when the cells were kept in the light than in the dark indicating the importance of metabolism in active transport of the mercury ions from outside to the intracytoplasmic membrane. Any of the tests applied in this study can be used for detection of changes in photosynthetic bacteria at the early stages of the action of toxicants.

Investigation of Stability of Photosynthetic Reaction Center and Quantum Dot Hybrid Films.

PubMed

Lukashev, E P; Knox, P P; Oleinikov, I P; Seifullina, N Kh; Grishanova, N P

2016-01-01

The efficiency of interaction (efficiency of energy transfer) between various quantum dots (QDs) and photosynthetic reaction centers (RCs) from the purple bacterium Rhodobacter sphaeroides and conditions of long-term stability of functioning of such hybrid complexes in film preparations were investigated. It was found that dry films containing RCs and QDs and maintained at atmospheric humidity are capable to keep their functional activity for at least some months as judging by results of measurement of their spectral characteristics, efficiency of energy transfer from QDs to RCs, and RC electron-transport activity. Addition of trehalose to the films giving them still greater stability is especially expressed for films maintained at low humidity. These stable hybrid film structures are promising for further biotechnological studies for developing new phototransformation devices.

Oxygen dynamics in photosynthetic membranes.

NASA Astrophysics Data System (ADS)

Savikhin, Sergei; Kihara, Shigeharu

2008-03-01

Production of oxygen by oxygenic photosynthetic organisms is expected to raise oxygen concentration within their photosynthetic membranes above normal aerobic values. These raised levels of oxygen may affect function of many proteins within photosynthetic cells. However, experiments on proteins in vitro are usually performed in aerobic (or anaerobic) conditions since the oxygen content of a membrane is not known. Using theory of diffusion and measured oxygen production rates we estimated the excess levels of oxygen in functioning photosynthetic cells. We show that for an individual photosynthetic cell suspended in water oxygen level is essentially the same as that for a non-photosynthetic sell. These data suggest that oxygen protection mechanisms may have evolved after the development of oxygenic photosynthesis in primitive bacteria and was driven by the overall rise of oxygen concentration in the atmosphere. Substantially higher levels of oxygen are estimated to occur in closely packed colonies of photosynthetic bacteria and in green leafs.

The light-harvesting antenna of Chlorobium tepidum: interactions between the FMO protein and the major chlorosome protein CsmA studied by surface plasmon resonance.

PubMed

Pedersen, Marie Østergaard; Borch, Jonas; Højrup, Peter; Cox, Raymond P; Miller, Mette

2006-09-01

Green sulfur bacteria possess two external light-harvesting antenna systems, the chlorosome and the FMO protein, which participate in a sequential energy transfer to the reaction centers embedded in the cytoplasmic membrane. However, little is known about the physical interaction between these two antenna systems. We have studied the interaction between the major chlorosome protein, CsmA, and the FMO protein in Chlorobium tepidum using surface plasmon resonance (SPR). Our results show an interaction between the FMO protein and an immobilized synthetic peptide corresponding to 17 amino acids at the C terminal of CsmA. This interaction is dependent on the presence of a motif comprising six amino acids that are highly conserved in all the currently available CsmA protein sequences.

Photosynthetic water splitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenbaum, E.

1981-01-01

The photosynthetic unit of hydrogen evolution, the turnover time of photosynthetic hydrogen production, and hydrogenic photosynthesis are discussed in the section on previous work. Recent results are given on simultaneous photoproduction of hydrogen and oxygen, kinetic studies, microscopic marine algae-seaweeds, and oxygen profiles.

Novel insights into the algicidal bacterium DH77-1 killing the toxic dinoflagellate Alexandrium tamarense.

PubMed

Yang, Xiaoru; Li, Xinyi; Zhou, Yanyan; Zheng, Wei; Yu, Changping; Zheng, Tianling

2014-06-01

Algicidal bacteria may play a major role in controlling harmful algal blooms (HABs) dynamics. Bacterium DH77-1 was isolated with high algicidal activity against the toxic dinoflagellate Alexandrium tamarense and identified as Joostella sp. DH77-1. The results showed that DH77-1 exhibited algicidal activity through indirect attack, which excreted active substance into the filtrate. It had a relatively wide host range and the active substance of DH77-1 was relatively stable since temperature, pH and storage condition had no obvious effect on the algicidal activity. The algicidal compound from bacterium DH77-1 was isolated based on activity-guided bioassay and the molecular weight was determined to be 125.88 by MALDI-TOF mass spectrometer, however further identification via nuclear magnetic resonance (NMR) spectra is ongoing. The physiological responses of algal cells after exposure to the DH77-1 algicidal substances were as follows: the antioxidant system of A. tamarense responded positively in self-defense; total protein content decreased significantly as did the photosynthetic pigment content; superoxide dismutase, peroxidase enzyme and malondialdehyde content increased extraordinarily and algal cell nucleic acid leaked seriously ultimately inducing cell death. Furthermore, DH77-1 is the first record of a Joostella sp. bacterium being algicidal to the harmful dinoflagellate A. tamarense, and the bacterial culture and the active compounds might be potentially used as a bio-agent for controlling harmful algal blooms. Copyright © 2014 Elsevier B.V. All rights reserved.

Role of PufX protein in photosynthetic growth of Rhodobacter sphaeroides. 1. PufX is required for efficient light-driven electron transfer and photophosphorylation under anaerobic conditions.

PubMed

Barz, W P; Francia, F; Venturoli, G; Melandri, B A; Verméglio, A; Oesterhelt, D

1995-11-21

The pufX gene is essential for photoheterotrophic growth of the purple bacterium Rhodobacter sphaeroides. In order to analyze the molecular function of the PufX membrane protein, we constructed a chromosomal pufX deletion mutant and phenotypically compared it to a pufX+ control strain and to two suppressor mutants which are able to grow photosynthetically in the absence of pufX. Using this genetic background, we confirmed that PufX is required for photoheterotrophic growth under anaerobic conditions, although all components of the photosynthetic apparatus were present in similar amounts in all strains investigated. We show that the deletion of PufX is not lethal for illuminated pufX- cells, suggesting that PufX is required for photosynthetic cell division. Since chromatophores isolated from the pufX- mutant were found to be unsealed vesicles, the role of PufX in photosynthetic energy transduction was studied in vivo. We show that PufX is essential for light-induced ATP synthesis (photophosphorylation) in anaerobically incubated cells. Measurements of absorption changes induced by a single turnover flash demonstrated that PufX is not required for electron flow through the reaction center and the cytochrome bc1 complex under anaerobic conditions. During prolonged illumination, however, PufX is essential for the generation of a sufficiently large membrane potential to allow photosynthetic growth. These in vivo results demonstrate that under anaerobic conditions PufX plays an essential role in facilitating effective interaction of the components of the photosynthetic apparatus.

Stark absorption spectroscopy on the carotenoids bound to B800-820 and B800-850 type LH2 complexes from a purple photosynthetic bacterium, Phaeospirillum molischianum strain DSM120.

PubMed

Horibe, Tomoko; Qian, Pu; Hunter, C Neil; Hashimoto, Hideki

2015-04-15

Stark absorption spectroscopy was applied to clarify the structural differences between carotenoids bound to the B800-820 and B800-850 LH2 complexes from a purple photosynthetic bacterium Phaeospirillum (Phs.) molischianum DSM120. The former complex is produced when the bacteria are grown under stressed conditions of low temperature and dim light. These two LH2 complexes bind carotenoids with similar composition, 10% lycopene and 80% rhodopin, each with the same number of conjugated CC double bonds (n=11). Quantitative classical and semi-quantum chemical analyses of Stark absorption spectra recorded in the carotenoid absorption region reveal that the absolute values of the difference dipole moments |Δμ| have substantial differences (2 [D/f]) for carotenoids bound to either B800-820 or B800-850 complexes. The origin of this striking difference in the |Δμ| values was analyzed using the X-ray crystal structure of the B800-850 LH2 complex from Phs. molischianum DSM119. Semi-empirical molecular orbital calculations predict structural deformations of the major carotenoid, rhodopin, bound within the B800-820 complex. We propose that simultaneous rotations around neighboring CC and CC bonds account for the differences in the 2 [D/f] of the |Δμ| value. The plausible position of the rotation is postulated to be located around C21-C24 bonds of rhodopin. Copyright © 2014 Elsevier Inc. All rights reserved.

Triplet excited state spectra and dynamics of carotenoids from the thermophilic purple photosynthetic bacterium Thermochromatium tepidum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niedzwiedzki, Dariusz; Kobayashi, Masayuki; Blankenship, R. E.

Light-harvesting complex 2 from the anoxygenic phototrophic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption, fluorescence and flash photolysis spectroscopy. Steady-state absorption and fluorescence measurements show that carotenoids play a negligible role as supportive energy donors and transfer excitation to bacteriochlorophyll-a with low energy transfer efficiency of ~30%. HPLC analysis determined that the dominant carotenoids in the complex are rhodopin and spirilloxanthin. Carotenoid excited triplet state formation upon direct (carotenoid) or indirect (bacteriochlorophyll-a Q{sub x} band) excitation shows that carotenoid triplets are mostly localized on spirilloxanthin. In addition, no triplet excitation transfer between carotenoids was observed. Suchmore » specific carotenoid composition and spectroscopic results strongly suggest that this organism optimized carotenoid composition in the light-harvesting complex 2 in order to maximize photoprotective capabilities of carotenoids but subsequently drastically suppressed their supporting role in light-harvesting process.« less

Photoinhibition of Phaeocystis globosa resulting from oxidative stress induced by a marine algicidal bacterium Bacillus sp. LP-10.

PubMed

Guan, Chengwei; Guo, Xiaoyun; Li, Yi; Zhang, Huajun; Lei, Xueqian; Cai, Guanjing; Guo, Jiajia; Yu, Zhiming; Zheng, Tianling

2015-11-25

Harmful algal blooms caused by Phaeocystis globosa have resulted in staggering losses to coastal countries because of their world-wide distribution. Bacteria have been studied for years to control the blooms of harmful alga, however, the action mechanism of them against harmful algal cells is still not well defined. Here, a previously isolated algicidal bacterium Bacillus sp. LP-10 was used to elucidate the potential mechanism involved in the dysfunction of P. globosa algal cells at physiological and molecular levels. Our results showed Bacillus sp. LP-10 induced an obvious rise of reactive oxygen species (ROS), which was supposed to be major reason for algal cell death. Meanwhile, the results revealed a significant decrease of photosynthetic physiological indexes and apparent down-regulated of photosynthesis-related genes (psbA and rbcS) and protein (PSII reaction center protein D1), after treated by Bacillus sp. LP-10 filtrates, suggesting photoinhibition occurred in the algal cells. Furthermore, our results indicated that light played important roles in the algal cell death. Our work demonstrated that the major lethal reason of P. globosa cells treated by the algicidal bacterium was the photoinhibition resulted from oxidative stress induced by Bacillus sp. LP-10.

Photosynthetic approaches to chemical biotechnology.

PubMed

Desai, Shuchi H; Atsumi, Shota

2013-12-01

National interest and environmental advocates encourage alternatives to petroleum-based products. Besides biofuels, many other valuable chemicals used in every-day life are petroleum derivatives or require petroleum for their production. A plausible alternative to production using petroleum for chemical production is to harvest the abundant carbon dioxide resources in the environment to produce valuable hydrocarbons. Currently, efforts are being made to utilize a natural biological system, photosynthetic microorganisms, to perform this task. Photosynthetic microorganisms are attractive to use for biochemical production because they utilize economical resources for survival: sunlight and carbon dioxide. This review examines the various compounds produced by photosynthetic microorganisms. Copyright © 2013 Elsevier Ltd. All rights reserved.

Clades of Photosynthetic Bacteria Belonging to the Genus Rhodopseudomonas Show Marked Diversity in Light-Harvesting Antenna Complex Gene Composition and Expression

DOE PAGES

Fixen, Kathryn R.; Oda, Yasuhiro; Harwood, Caroline S.; ...

2015-12-22

Many photosynthetic bacteria have peripheral light-harvesting (LH) antenna complexes that increase the efficiency of light energy capture. The purple nonsulfur photosynthetic bacteriumRhodopseudomonas palustrisproduces different types of LH complexes under high light intensities (LH2 complex) and low light intensities (LH3 and LH4 complexes). There are multiplepucBAoperons that encode the α and β peptides that make up these complexes. But, low-resolution structures, amino acid similarities between the complexes, and a lack of transcription analysis have made it difficult to determine the contributions of differentpucBAoperons to the composition and function of different LH complexes. It was also unclear how much diversity of LHmore » complexes exists inR. palustrisand affiliated strains. To address this, we undertook an integrative genomics approach using 20 sequenced strains. Gene content analysis revealed that even closely related strains have differences in theirpucBAgene content. Transcriptome analyses of the strains grown under high light and low light revealed that the patterns of expression of thepucBAoperons varied among strains grown under the same conditions. We also found that one set of LH2 complex proteins compensated for the lack of an LH4 complex under low light intensities but not under extremely low light intensities, indicating that there is functional redundancy between some of the LH complexes under certain light intensities. The variation observed in LH gene composition and expression inRhodopseudomonasstrains likely reflects how they have evolved to adapt to light conditions in specific soil and water microenvironments. ImportanceRhodopseudomonas palustrisis a phototrophic purple nonsulfur bacterium that adapts its photosystem to allow growth at a range of light intensities. It does this by adjusting the amount and composition of peripheral light-harvesting (LH) antenna complexes that it synthesizes.Rhodopseudomonasstrains are notable for

Clades of Photosynthetic Bacteria Belonging to the Genus Rhodopseudomonas Show Marked Diversity in Light-Harvesting Antenna Complex Gene Composition and Expression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fixen, Kathryn R.; Oda, Yasuhiro; Harwood, Caroline S.

Many photosynthetic bacteria have peripheral light-harvesting (LH) antenna complexes that increase the efficiency of light energy capture. The purple nonsulfur photosynthetic bacteriumRhodopseudomonas palustrisproduces different types of LH complexes under high light intensities (LH2 complex) and low light intensities (LH3 and LH4 complexes). There are multiplepucBAoperons that encode the α and β peptides that make up these complexes. But, low-resolution structures, amino acid similarities between the complexes, and a lack of transcription analysis have made it difficult to determine the contributions of differentpucBAoperons to the composition and function of different LH complexes. It was also unclear how much diversity of LHmore » complexes exists inR. palustrisand affiliated strains. To address this, we undertook an integrative genomics approach using 20 sequenced strains. Gene content analysis revealed that even closely related strains have differences in theirpucBAgene content. Transcriptome analyses of the strains grown under high light and low light revealed that the patterns of expression of thepucBAoperons varied among strains grown under the same conditions. We also found that one set of LH2 complex proteins compensated for the lack of an LH4 complex under low light intensities but not under extremely low light intensities, indicating that there is functional redundancy between some of the LH complexes under certain light intensities. The variation observed in LH gene composition and expression inRhodopseudomonasstrains likely reflects how they have evolved to adapt to light conditions in specific soil and water microenvironments. ImportanceRhodopseudomonas palustrisis a phototrophic purple nonsulfur bacterium that adapts its photosystem to allow growth at a range of light intensities. It does this by adjusting the amount and composition of peripheral light-harvesting (LH) antenna complexes that it synthesizes.Rhodopseudomonasstrains are notable for

Photosynthetic Units

PubMed Central

Schmid, Georg H.; Gaffron, Hans

1968-01-01

Leaf tissues of aurea mutants of tobacco and Lespedeza have been shown to have higher photosynthetic capacity per molecule of chlorophyll, a higher saturation intensity, a simpler lamellar structure, and the same quantum yield as their dark green parents. Here we report on the values of photosynthetic units for both types of plants and some algae. The unit has been assumed to be about as uniform and steady in the plant world as the quantum efficiency. The number on which all theoretical discussions have been based so far is 2400 per O2 evolved or CO2 reduced. With dark green plants and algae our determinations of units by means of 40 µsec flashes superimposed on a steady rate of background photosynthesis at 900 ergs cm-2 sec-1 of red light yielded mostly numbers between 2000 and 2700. However, the photosynthetic unit turned out to be very variable, even in these objects. In aurea mutants the unit was distinctly smaller, averaging 600 chl/CO2. By choosing the right combination of colors for flash and background light, units as low as 300 chl/CO2 or 40 chl/e- could be measured consistently. We found five well-defined groups of units composed of multiples of its smallest member. These new findings are discussed in terms of structural entities that double or divide under the influence of far-red light. PMID:5672002

Photosynthetic capacity regulation is uncoupled from nutrient limitation

NASA Astrophysics Data System (ADS)

Smith, N. G.; Keenan, T. F.; Prentice, I. C.; Wang, H.

2017-12-01

Ecosystem and Earth system models need information on leaf-level photosynthetic capacity, but to date typically rely on empirical estimates and an assumed dependence on nitrogen supply. Recent evidence suggests that leaf nitrogen is actively controlled though plant responses to photosynthetic demand. Here, we propose and test a theory of demand-driven coordination of photosynthetic processes, and use it to assess the relative roles of nutrient supply and photosynthetic demand. The theory captured 63% of observed variability in a global dataset of Rubisco carboxylation capacity (Vcmax; 3,939 values at 219 sites), suggesting that environmentally regulated biophysical costs and light availability are the first-order drivers of photosynthetic capacity. Leaf nitrogen, on the other hand, was a weak secondary driver of Vcmax, explaining less than 6% of additional observed variability. We conclude that leaf nutrient allocation is primarily driven by demand. Our theory offers a simple, robust strategy for dynamically predicting leaf-level photosynthetic capacity in global models.

Photoinhibition of Phaeocystis globosa resulting from oxidative stress induced by a marine algicidal bacterium Bacillus sp. LP-10

PubMed Central

Guan, Chengwei; Guo, Xiaoyun; Li, Yi; Zhang, Huajun; Lei, Xueqian; Cai, Guanjing; Guo, Jiajia; Yu, Zhiming; Zheng, Tianling

2015-01-01

Harmful algal blooms caused by Phaeocystis globosa have resulted in staggering losses to coastal countries because of their world-wide distribution. Bacteria have been studied for years to control the blooms of harmful alga, however, the action mechanism of them against harmful algal cells is still not well defined. Here, a previously isolated algicidal bacterium Bacillus sp. LP-10 was used to elucidate the potential mechanism involved in the dysfunction of P. globosa algal cells at physiological and molecular levels. Our results showed Bacillus sp. LP-10 induced an obvious rise of reactive oxygen species (ROS), which was supposed to be major reason for algal cell death. Meanwhile, the results revealed a significant decrease of photosynthetic physiological indexes and apparent down-regulated of photosynthesis-related genes (psbA and rbcS) and protein (PSII reaction center protein D1), after treated by Bacillus sp. LP-10 filtrates, suggesting photoinhibition occurred in the algal cells. Furthermore, our results indicated that light played important roles in the algal cell death. Our work demonstrated that the major lethal reason of P. globosa cells treated by the algicidal bacterium was the photoinhibition resulted from oxidative stress induced by Bacillus sp. LP-10. PMID:26601700

Regulation of Photosynthetic Electron Transport and Photoinhibition

PubMed Central

Roach, Thomas; Krieger-Liszkay, Anja Krieger

2014-01-01

Photosynthetic organisms and isolated photosystems are of interest for technical applications. In nature, photosynthetic electron transport has to work efficiently in contrasting environments such as shade and full sunlight at noon. Photosynthetic electron transport is regulated on many levels, starting with the energy transfer processes in antenna and ending with how reducing power is ultimately partitioned. This review starts by explaining how light energy can be dissipated or distributed by the various mechanisms of non-photochemical quenching, including thermal dissipation and state transitions, and how these processes influence photoinhibition of photosystem II (PSII). Furthermore, we will highlight the importance of the various alternative electron transport pathways, including the use of oxygen as the terminal electron acceptor and cyclic flow around photosystem I (PSI), the latter which seem particularly relevant to preventing photoinhibition of photosystem I. The control of excitation pressure in combination with the partitioning of reducing power influences the light-dependent formation of reactive oxygen species in PSII and in PSI, which may be a very important consideration to any artificial photosynthetic system or technical device using photosynthetic organisms. PMID:24678670

An x-ray absorption study of the iron site in bacterial photosynthetic reaction centers.

PubMed Central

Bunker, G; Stern, E A; Blankenship, R E; Parson, W W

1982-01-01

Measurements were made of the extended x-ray absorption fine structure (EXAFS) of the iron site in photosynthetic reaction centers from the bacterium Rhodopseudomonas sphaeroides. Forms with two quinones, two quinones with added o-phenanthroline, and one quinone were studied. Only the two forms containing two quinones maintained their integrity and were analyzed. The spectra show directly that the added o-phenanthroline does not chelate the iron atom. Further analysis indicates that the iron is octahedrally coordinated by nitrogen and/or oxygen atoms located at various distances, with the average value of about 2.14 A. The analysis suggests that most of the ligands are nitrogens and that three of the nitrogen ligands belong to histidine rings. This interpretation accounts for several unusual features of the EXAFS spectrum. We speculate that the quinones are bound to the histidine rings in some manner. Qualitative features of the absorption edge spectra also are discussed and are related to the Fe-ligand distance. PMID:6977382

Differential uptake of photosynthetic and non-photosynthetic proteins by pea root plastids.

PubMed

Yan, Xianxi; Khan, Sultan; Hase, Toshiharu; Emes, Michael J; Bowsher, Caroline G

2006-11-27

The photosynthetic proteins RuBiSCO, ferredoxin I and ferredoxin NADP(+)-oxidoreductase (pFNR) were efficiently imported into isolated pea chloroplasts but not into pea root plastids. By contrast non-photosynthetic ferredoxin III and heterotrophic FNR (hFNR) were efficiently imported into both isolated chloroplasts and root plastids. Chimeric ferredoxin I/III (transit peptide of ferredoxin I attached to the mature region of ferredoxin III) only imported into chloroplasts. Ferredoxin III/I (transit peptide of ferredoxin III attached to the mature region of ferredoxin I) imported into both chloroplasts and root plastids. This suggests that import depends on specific interactions between the transit peptide and the translocon apparatus.

Function of membrane protein in silica nanopores: incorporation of photosynthetic light-harvesting protein LH2 into FSM.

PubMed

Oda, Ippei; Hirata, Kotaro; Watanabe, Syoko; Shibata, Yutaka; Kajino, Tsutomu; Fukushima, Yoshiaki; Iwai, Satoshi; Itoh, Shigeru

2006-01-26

A high amount of functional membrane protein complex was introduced into a folded-sheet silica mesoporous material (FSM) that has nanometer-size pores of honeycomb-like hexagonal cylindrical structure inside. The photosynthetic light-harvesting complex LH2, which is a typical membrane protein, has a cylindrical structure of 7.3 nm diameter and contains 27 bacteriochlorophyll a and nine carotenoid molecules. The complex captures light energy in the anoxygenic thermophilic purple photosynthetic bacterium Thermochromatium tepidum. The amount of LH2 adsorbed to FSM was determined optically and by the adsorption isotherms of N2. The FSM compounds with internal pore diameters of 7.9 and 2.7 nm adsorbed LH2 at 1.11 and 0.24 mg/mg FSM, respectively, suggesting the high specific affinity of LH2 to the interior of the hydrophobic nanopores with a diameter of 7.9 nm. The LH2 adsorbed to FSM showed almost intact absorption bands of bacteriochlorophylls, and was fully active in the capture and transfer of excitation energy. The LH2 complex inside the FSM showed increased heat stability of the exciton-type absorption band of bacteriochlorophylls (B850), suggesting higher circular symmetry. The environment inside the hydrophobic silica nanopores can be a new matrix for the membrane proteins to reveal their functions. The silica-membrane protein adduct will be useful for the construction of new probes and reaction systems.

[Photosynthetic characteristics of five arbor species in Shenyang urban area].

PubMed

Li, Hai-Me; He, Xing-Yuan; Wang, Kui-Ling; Chen, Wei

2007-08-01

By using LI-6400 infrared gas analyzer, this paper studied the diurnal and seasonal variations of the photosynthetic rate of main arbor species (Populus alba x P. berolinensis, Salix matsudana, Ulmus pumila, Robinia pseudoacacia and Prunus davidiana) in Shenyang urban area. The correlations between net photosynthetic rate and environmental factors (photosynthetic active radiation, temperature, and stomatal conductance) were assessed by multivariate regression analysis, and related equations were constructed. The results showed that for test arbor species, the diurnal variation of photosynthetic rate mainly presented a single peak curve, and the seasonal variation was in the order of summer > autumn > spring. The major factors affecting the photosynthetic rate were photosynthetic active radiation, stomatal conductance, and intercellular CO2 concentration.

NREL Researchers Discover How a Bacterium, Clostridium thermocellum,

Science.gov Websites

containing the bacterium actually promotes the growth of C. thermocellum, yet its mechanistic details remained a puzzle. This enhanced growth implied the bacterium had the ability to use CO2 and prompted NREL researchers to investigate the phenomena enhancing the bacterium's growth. "It took us by surprise that

Morning reduction of photosynthetic capacity before midday depression.

PubMed

Koyama, Kohei; Takemoto, Shuhei

2014-03-17

Midday depression of photosynthesis has important consequences for ecosystem carbon exchange. Recent studies of forest trees have demonstrated that latent reduction of photosynthetic capacity can begin in the early morning, preceding the midday depression. We investigated whether such early morning reduction also occurs in an herbaceous species, Oenothera biennis. Diurnal changes of the photosynthetic light response curve (measured using a light-emitting diode) and incident sunlight intensity were measured under field conditions. The following results were obtained: (1) the light-saturated photosynthetic rate decreased beginning at sunrise; (2) the incident sunlight intensity on the leaves increased from sunrise; and (3) combining (1) and (2), the net photosynthetic rate under natural sunlight intensity increased from sunrise, reached a maximum at mid-morning, and then showed midday depression. Our results demonstrate that the latent morning reduction of photosynthetic capacity begins at sunrise, preceding the apparent midday depression, in agreement with previous studies of forest trees.

Biological optimization systems for enhancing photosynthetic efficiency and methods of use

DOEpatents

Hunt, Ryan W.; Chinnasamy, Senthil; Das, Keshav C.; de Mattos, Erico Rolim

2012-11-06

Biological optimization systems for enhancing photosynthetic efficiency and methods of use. Specifically, methods for enhancing photosynthetic efficiency including applying pulsed light to a photosynthetic organism, using a chlorophyll fluorescence feedback control system to determine one or more photosynthetic efficiency parameters, and adjusting one or more of the photosynthetic efficiency parameters to drive the photosynthesis by the delivery of an amount of light to optimize light absorption of the photosynthetic organism while providing enough dark time between light pulses to prevent oversaturation of the chlorophyll reaction centers are disclosed.

Effects of ultraviolet radiation (UVA+UVB) on young gametophytes of Gelidium floridanum: growth rate, photosynthetic pigments, carotenoids, photosynthetic performance, and ultrastructure.

PubMed

Simioni, Carmen; Schmidt, Eder C; Felix, Marthiellen R de L; Polo, Luz Karime; Rover, Ticiane; Kreusch, Marianne; Pereira, Debora T; Chow, Fungyi; Ramlov, Fernanda; Maraschin, Marcelo; Bouzon, Zenilda L

2014-01-01

This study investigated the effects of radiation (PAR+UVA+UVB) on the development and growth rates (GRs) of young gametophytes of Gelidium floridanum. In addition, photosynthetic pigments were quantified, carotenoids identified, and photosynthetic performance assessed. Over a period of 3 days, young gametophytes were cultivated under laboratory conditions and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m(-2) s(-1) and PAR+UVA (0.70 W m(-2))+UVB (0.35 W m(-2)) for 3 h per day. The samples were processed for light and electron microscopy to analyze the ultrastructure features, as well as carry out metabolic studies of GRs, quantify the content of photosynthetic pigments, identify carotenoids and assess photosynthetic performance. PAR+UVA+UVB promoted increase in cell wall thickness, accumulation of floridean starch grains in the cytoplasm and disruption of chloroplast internal organization. Algae exposed to PAR+UVA+UVB also showed a reduction in GR of 97%. Photosynthetic pigments, in particular, phycoerythrin and allophycocyanin contents, decreased significantly from UV radiation exposure. This result agrees with the decrease in photosynthetic performance observed after exposure to ultraviolet radiation, as measured by a decrease in the electron transport rate (ETR), where values of ETRmax declined approximately 44.71%. It can be concluded that radiation is a factor that affects the young gametophytes of G. floridanum at this stage of development. © 2014 The American Society of Photobiology.

Nonlinear spectral mixture effects for photosynthetic/non-photosynthetic vegetation cover estimates of typical desert vegetation in western China.

PubMed

Ji, Cuicui; Jia, Yonghong; Gao, Zhihai; Wei, Huaidong; Li, Xiaosong

2017-01-01

Desert vegetation plays significant roles in securing the ecological integrity of oasis ecosystems in western China. Timely monitoring of photosynthetic/non-photosynthetic desert vegetation cover is necessary to guide management practices on land desertification and research into the mechanisms driving vegetation recession. In this study, nonlinear spectral mixture effects for photosynthetic/non-photosynthetic vegetation cover estimates are investigated through comparing the performance of linear and nonlinear spectral mixture models with different endmembers applied to field spectral measurements of two types of typical desert vegetation, namely, Nitraria shrubs and Haloxylon. The main results were as follows. (1) The correct selection of endmembers is important for improving the accuracy of vegetation cover estimates, and in particular, shadow endmembers cannot be neglected. (2) For both the Nitraria shrubs and Haloxylon, the Kernel-based Nonlinear Spectral Mixture Model (KNSMM) with nonlinear parameters was the best unmixing model. In consideration of the computational complexity and accuracy requirements, the Linear Spectral Mixture Model (LSMM) could be adopted for Nitraria shrubs plots, but this will result in significant errors for the Haloxylon plots since the nonlinear spectral mixture effects were more obvious for this vegetation type. (3) The vegetation canopy structure (planophile or erectophile) determines the strength of the nonlinear spectral mixture effects. Therefore, no matter for Nitraria shrubs or Haloxylon, the non-linear spectral mixing effects between the photosynthetic / non-photosynthetic vegetation and the bare soil do exist, and its strength is dependent on the three-dimensional structure of the vegetation canopy. The choice of linear or nonlinear spectral mixture models is up to the consideration of computational complexity and the accuracy requirement.

Nonlinear spectral mixture effects for photosynthetic/non-photosynthetic vegetation cover estimates of typical desert vegetation in western China

PubMed Central

Jia, Yonghong; Gao, Zhihai; Wei, Huaidong

2017-01-01

Desert vegetation plays significant roles in securing the ecological integrity of oasis ecosystems in western China. Timely monitoring of photosynthetic/non-photosynthetic desert vegetation cover is necessary to guide management practices on land desertification and research into the mechanisms driving vegetation recession. In this study, nonlinear spectral mixture effects for photosynthetic/non-photosynthetic vegetation cover estimates are investigated through comparing the performance of linear and nonlinear spectral mixture models with different endmembers applied to field spectral measurements of two types of typical desert vegetation, namely, Nitraria shrubs and Haloxylon. The main results were as follows. (1) The correct selection of endmembers is important for improving the accuracy of vegetation cover estimates, and in particular, shadow endmembers cannot be neglected. (2) For both the Nitraria shrubs and Haloxylon, the Kernel-based Nonlinear Spectral Mixture Model (KNSMM) with nonlinear parameters was the best unmixing model. In consideration of the computational complexity and accuracy requirements, the Linear Spectral Mixture Model (LSMM) could be adopted for Nitraria shrubs plots, but this will result in significant errors for the Haloxylon plots since the nonlinear spectral mixture effects were more obvious for this vegetation type. (3) The vegetation canopy structure (planophile or erectophile) determines the strength of the nonlinear spectral mixture effects. Therefore, no matter for Nitraria shrubs or Haloxylon, the non-linear spectral mixing effects between the photosynthetic / non-photosynthetic vegetation and the bare soil do exist, and its strength is dependent on the three-dimensional structure of the vegetation canopy. The choice of linear or nonlinear spectral mixture models is up to the consideration of computational complexity and the accuracy requirement. PMID:29240777

Research on spatial distribution of photosynthetic characteristics of Winter Wheat

NASA Astrophysics Data System (ADS)

Yan, Q. Q.; Zhou, Q. Y.; Zhang, B. Z.; Han, X.; Han, N. N.; Li, S. M.

2018-03-01

In order to explore the spatial distribution of photosynthetic characteristics of winter wheat leaf, the photosynthetic rate on different parts of leaf (leaf base-leaf middle-leaf apex) and that on each canopy (top layer-middle layer-bottom layer) leaf during the whole growth period of winter wheat were measured. The variation of photosynthetic rate with PAR and the spatial distribution of winter wheat leaf during the whole growth periods were analysed. The results showed that the photosynthetic rate of different parts of winter wheat increased with the increase of PAR, which was showed as leaf base>leaf middle>leaf apex. In the same growth period, photosynthetic rate in different parts of the tablet was showed as leaf middle>leaf base>leaf apex. For the different canopy layer of winter wheat, the photosynthetic rate of the top layer leaf was significantly greater than that of the middle layer and lower layer leaf. The photosynthetic rate of the top layer leaf was the largest in the leaf base position. The photosynthetic rate of leaf of the same canopy layer at different growth stages were showed as tasseling stage >grain filling stage > maturation stage.

BOREAS TE-10 Photosynthetic Response Data

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Middleton, Elizabeth; Sullivan, Joseph

2000-01-01

The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-10 (Terrestrial Ecology) team collected several data sets in support of its efforts to characterize and interpret information on the gas exchange, reflectance, transmittance, chlorophyll content, carbon content, hydrogen content, nitrogen content, and photosynthetic response of boreal vegetation. This data set contains measurements of quantitative parameters and leaf photosynthetic response to increases in light conducted in the SSA during the growing seasons of 1994 and 1996 using an oxygen electrode system. Leaf photosynthetic responses were not collected in 1996. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Isotopic replacement of pigments and a lipid in chlorosomes from Chlorobium limicola: characterization of the resultant chlorosomes.

PubMed

Kakitani, Yoshinori; Harada, Ken-ichi; Mizoguchi, Tadashi; Koyama, Yasushi

2007-06-05

Pigments including bacteriochlorophyll (BChl) c, carotenoids, and a trace of BChl a together with a lipid, monogalactosyl diglyceride (MGDG), were extracted with chloroform/methanol (1:1 v/v) from an aqueous suspension (50 mM Tris-HCl, pH 8.0) of chlorosomes from Chlorobium limicola; other lipids and proteins were left behind in the aqueous layer by funnel separation. The chloroform layer was dried by purging N2 gas, dissolved in methanol, and rapidly injected into the aqueous layer to reassemble chlorosomes. This technique has been developed to replace one-half of the inherent 12C-BChl c by 13C-BChl c to identify the intermolecular 13C...13C magnetic dipole correlation peaks (that are supposed to reduce their intensities to one-fourth by reducing the 13C-BChl c concentration into one-half) and to determine the structure of BChl c aggregates in the rod elements by means of solid-state NMR spectroscopy. The isotopically replaced chlorosomes were characterized (1) by sucrose density gradient centrifugation, zeta potential measurement, electron microscopy, and dynamic light scattering measurement to determine the morphology of chlorosomes, (2) by 13C NMR spectroscopy, electronic absorption and circular dichroism spectroscopies, and low-angle X-ray diffraction to determine the pigment assembly in the rod elements, and (3) by subpicosecond time-resolved absorption spectroscopy to determine the excited-state dynamics in the pigment assembly. The results characterized the reassembled chlorosomes to have (1) similar but longer morphological structures, (2) almost the same pigment assembly in the rod elements, and (3) basically the same excited-state dynamics in the pigment assembly.

Adaptation to oxygen: role of terminal oxidases in photosynthesis initiation in the purple photosynthetic bacterium, Rubrivivax gelatinosus.

PubMed

Hassani, Bahia Khalfaoui; Steunou, Anne-Soisig; Liotenberg, Sylviane; Reiss-Husson, Françoise; Astier, Chantal; Ouchane, Soufian

2010-06-25

The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb(3), bd, and caa(3)) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb(3)(-)/bd(-) double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria. In oxygenated environments, this mutant survives nonphotosynthetically until the O(2) tension is reduced. The cbb(3) and bd oxidases are therefore required not only for respiration but also for reduction of the environmental O(2) pressure prior to anaerobic photosynthesis. Suppressor mutations that restore respiration simultaneously restore photosynthesis in nondeoxygenated medium. Furthermore, induction of photosystem in the cbb(3)(-) mutant led to a highly unstable strain. These results demonstrate that photosynthetic metabolism in environments exposed to oxygen is critically dependent on the O(2)-detoxifying action of terminal oxidases.

How to harvest solar energy with the photosynthetic reaction center

NASA Astrophysics Data System (ADS)

Balaeff, Alexander; Reyes, Justin

Photosynthetic reaction center (PRC) is a protein complex that performs a key step in photosynthesis: the electron-hole separation driven by photon absorbtion. The PRC has a great promise for applications in solar energy harvesting and photosensing. Such applications, however, are hampered by the difficulty in extracting the photogenerated electric charge from the PRC. To that end, it was proposed to attach the PRC to a molecular wire through which the charge could be collected. In order to find the attachment point for the wire that would maximize the rate of charge outflow from the PRC, we performed a computational study of the PRC from the R. virdis bacterium. An ensemble of PRC structures generated by a molecular dynamics simulation was used to calculate the rate of charge transport from the site of initial charge separation to several trial sites on the protein surface. The Pathways model was used to calculate the charge transfer rate in each step of the network of heme co-factors through which the charge transport was presumed to proceed. A simple kinetic model was then used to determine the overall rate of the multistep charge transport. The calculations revealed several candidate sites for the molecular wire attachment, recommended for experimental verification.

Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum.

PubMed

Niedzwiedzki, Dariusz M; Fuciman, Marcel; Kobayashi, Masayuki; Frank, Harry A; Blankenship, Robert E

2011-10-01

The light-harvesting complex 2 from the thermophilic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption and fluorescence, sub-nanosecond-time-resolved fluorescence and femtosecond time-resolved transient absorption spectroscopy. The measurements were performed at room temperature and at 10 K. The combination of both ultrafast and steady-state optical spectroscopy methods at ambient and cryogenic temperatures allowed the detailed study of carotenoid (Car)-to-bacteriochlorophyll (BChl) as well BChl-to-BChl excitation energy transfer in the complex. The studies show that the dominant Cars rhodopin (N=11) and spirilloxanthin (N=13) do not play a significant role as supportive energy donors for BChl a. This is related with their photophysical properties regulated by long π-electron conjugation. On the other hand, such properties favor some of the Cars, particularly spirilloxanthin (N=13) to play the role of the direct quencher of the excited singlet state of BChl. © Springer Science+Business Media B.V. 2011

Evolving a photosynthetic organelle.

PubMed

Nakayama, Takuro; Archibald, John M

2012-04-24

The evolution of plastids from cyanobacteria is believed to represent a singularity in the history of life. The enigmatic amoeba Paulinella and its 'recently' acquired photosynthetic inclusions provide a fascinating system through which to gain fresh insight into how endosymbionts become organelles.The plastids, or chloroplasts, of algae and plants evolved from cyanobacteria by endosymbiosis. This landmark event conferred on eukaryotes the benefits of photosynthesis--the conversion of solar energy into chemical energy--and in so doing had a huge impact on the course of evolution and the climate of Earth 1. From the present state of plastids, however, it is difficult to trace the evolutionary steps involved in this momentous development, because all modern-day plastids have fully integrated into their hosts. Paulinella chromatophora is a unicellular eukaryote that bears photosynthetic entities called chromatophores that are derived from cyanobacteria and has thus received much attention as a possible example of an organism in the early stages of organellogenesis. Recent studies have unlocked the genomic secrets of its chromatophore 23 and provided concrete evidence that the Paulinella chromatophore is a bona fide photosynthetic organelle 4. The question is how Paulinella can help us to understand the process by which an endosymbiont is converted into an organelle.

Electrostatic dominoes: long distance propagation of mutational effects in photosynthetic reaction centers of Rhodobacter capsulatus.

PubMed

Sebban, P; Maróti, P; Schiffer, M; Hanson, D K

1995-07-04

Two point mutants from the purple bacterium Rhodobacter capsulatus, both modified in the M protein of the photosynthetic reaction center, have been studied by flash-induced absorbance spectroscopy. These strains carry either the M231Arg --> Leu or M43ASN --> Asp mutations, which are located 9 and 15 A, respectively, from the terminal electron acceptor QB. In the wild-type Rb. sphaeroides structure, M231Arg is involved in a conserved salt bridge with H125Glu and H232Glu and M43Asn is located among several polar residues that form or surround the QB binding site. These substitutions were originally uncovered in phenotypic revertants isolated from the photosynthetically incompetent L212Glu-L213Asp --> Ala-Ala site-specific double mutant. As second-site suppressor mutations, they have been shown to restore the proton transfer function that is interrupted in the L212Ala-L213Ala double mutant. The electrostatic effects that are induced in reaction centers by the M231Arg --> Leu and M43Asn --> Asp substitutions are roughly the same in either the double-mutant or wild-type backgrounds. In a reaction center that is otherwise wild type in sequence, they decrease the free energy gap between the QA- and QB- states by 24 +/- 5 and 45 +/- 5 meV, respectively. The pH dependences of K2, the QA-QB <--> QAQB- equilibrium constant, are altered in reaction centers that carry either of these substitutions, revealing differences in the pKas of titratable groups compared to the wild type.(ABSTRACT TRUNCATED AT 250 WORDS)

Diversity and abundance of photosynthetic sponges in temperate Western Australia

PubMed Central

Lemloh, Marie-Louise; Fromont, Jane; Brümmer, Franz; Usher, Kayley M

2009-01-01

Background Photosynthetic sponges are important components of reef ecosystems around the world, but are poorly understood. It is often assumed that temperate regions have low diversity and abundance of photosynthetic sponges, but to date no studies have investigated this question. The aim of this study was to compare the percentages of photosynthetic sponges in temperate Western Australia (WA) with previously published data on tropical regions, and to determine the abundance and diversity of these associations in a range of temperate environments. Results We sampled sponges on 5 m belt transects to determine the percentage of photosynthetic sponges and identified at least one representative of each group of symbionts using 16S rDNA sequencing together with microscopy techniques. Our results demonstrate that photosynthetic sponges are abundant in temperate WA, with an average of 63% of sponge individuals hosting high levels of photosynthetic symbionts and 11% with low to medium levels. These percentages of photosynthetic sponges are comparable to those found on tropical reefs and may have important implications for ecosystem function on temperate reefs in other areas of the world. A diverse range of symbionts sometimes occurred within a small geographic area, including the three "big" cyanobacterial clades, Oscillatoria spongeliae, "Candidatus Synechococcus spongiarum" and Synechocystis species, and it appears that these clades all occur in a wide range of sponges. Additionally, spongin-permeating red algae occurred in at least 7 sponge species. This study provides the first investigation of the molecular phylogeny of rhodophyte symbionts in sponges. Conclusion Photosynthetic sponges are abundant and diverse in temperate WA, with comparable percentages of photosynthetic to non-photosynthetic sponges to tropical zones. It appears that there are three common generalist clades of cyanobacterial symbionts of sponges which occur in a wide range of sponges in a wide range

Oxygen Concentration Inside a Functioning Photosynthetic Cell

PubMed Central

Kihara, Shigeharu; Hartzler, Daniel A.; Savikhin, Sergei

2014-01-01

The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the oxygen level in the Earth’s atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere. PMID:24806920

Reductive evolution of chloroplasts in non-photosynthetic plants, algae and protists.

PubMed

Hadariová, Lucia; Vesteg, Matej; Hampl, Vladimír; Krajčovič, Juraj

2018-04-01

Chloroplasts are generally known as eukaryotic organelles whose main function is photosynthesis. They perform other functions, however, such as synthesizing isoprenoids, fatty acids, heme, iron sulphur clusters and other essential compounds. In non-photosynthetic lineages that possess plastids, the chloroplast genomes have been reduced and most (or all) photosynthetic genes have been lost. Consequently, non-photosynthetic plastids have also been reduced structurally. Some of these non-photosynthetic or "cryptic" plastids were overlooked or unrecognized for decades. The number of complete plastid genome sequences and/or transcriptomes from non-photosynthetic taxa possessing plastids is rapidly increasing, thus allowing prediction of the functions of non-photosynthetic plastids in various eukaryotic lineages. In some non-photosynthetic eukaryotes with photosynthetic ancestors, no traces of plastid genomes or of plastids have been found, suggesting that they have lost the genomes or plastids completely. This review summarizes current knowledge of non-photosynthetic plastids, their genomes, structures and potential functions in free-living and parasitic plants, algae and protists. We introduce a model for the order of plastid gene losses which combines models proposed earlier for land plants with the patterns of gene retention and loss observed in protists. The rare cases of plastid genome loss and complete plastid loss are also discussed.

RpoH2 sigma factor controls the photooxidative stress response in a non-photosynthetic rhizobacterium, Azospirillum brasilense Sp7.

PubMed

Kumar, Santosh; Rai, Ashutosh Kumar; Mishra, Mukti Nath; Shukla, Mansi; Singh, Pradhyumna Kumar; Tripathi, Anil Kumar

2012-12-01

Bacteria belonging to the Alphaproteobacteria normally harbour multiple copies of the heat shock sigma factor (known as σ(32), σ(H) or RpoH). Azospirillum brasilense, a non-photosynthetic rhizobacterium, harbours five copies of rpoH genes, one of which is an rpoH2 homologue. The genes around the rpoH2 locus in A. brasilense show synteny with that found in rhizobia. The rpoH2 of A. brasilense was able to complement the temperature-sensitive phenotype of the Escherichia coli rpoH mutant. Inactivation of rpoH2 in A. brasilense results in increased sensitivity to methylene blue and to triphenyl tetrazolium chloride (TTC). Exposure of A. brasilense to TTC and the singlet oxygen-generating agent methylene blue induced several-fold higher expression of rpoH2. Comparison of the proteome of A. brasilense with its rpoH2 deletion mutant and with an A. brasilense strain overexpressing rpoH2 revealed chaperone GroEL, elongation factors (Ef-Tu and EF-G), peptidyl prolyl isomerase, and peptide methionine sulfoxide reductase as the major proteins whose expression was controlled by RpoH2. Here, we show that the RpoH2 sigma factor-controlled photooxidative stress response in A. brasilense is similar to that in the photosynthetic bacterium Rhodobacter sphaeroides, but that RpoH2 is not involved in the detoxification of methylglyoxal in A. brasilense.

Principles of light harvesting from single photosynthetic complexes.

PubMed

Schlau-Cohen, G S

2015-06-06

Photosynthetic systems harness sunlight to power most life on Earth. In the initial steps of photosynthetic light harvesting, absorbed energy is converted to chemical energy with near-unity quantum efficiency. This is achieved by an efficient, directional and regulated flow of energy through a network of proteins. Here, we discuss the following three key principles of this flow and of photosynthetic light harvesting: thermal fluctuations of the protein structure; intrinsic conformational switches with defined functional consequences; and environmentally triggered conformational switches. Through these principles, photosynthetic systems balance two types of operational costs: metabolic costs, or the cost of maintaining and running the molecular machinery, and opportunity costs, or the cost of losing any operational time. Understanding how the molecular machinery and dynamics are designed to balance these costs may provide a blueprint for improved artificial light-harvesting devices. With a multi-disciplinary approach combining knowledge of biology, this blueprint could lead to low-cost and more effective solar energy conversion. Photosynthetic systems achieve widespread light harvesting across the Earth's surface; in the face of our growing energy needs, this is functionality we need to replicate, and perhaps emulate.

Tree Species with Photosynthetic Stems Have Greater Nighttime Sap Flux

PubMed Central

Chen, Xia; Gao, Jianguo; Zhao, Ping; McCarthy, Heather R.; Zhu, Liwei; Ni, Guangyan; Ouyang, Lei

2018-01-01

An increasing body of evidence has shown that nighttime sap flux occurs in most plants, but the physiological implications and regulatory mechanism are poorly known. The significance of corticular photosynthesis has received much attention during the last decade, however, the knowledge of the relationship between corticular photosynthesis and nocturnal stem sap flow is limited at present. In this study, we divided seven tree species into two groups according to different photosynthetic capabilities: trees of species with (Castanopsis hystrix, Michelia macclurei, Eucalyptus citriodora, and Eucalyptus grandis × urophylla) and without (Castanopsis fissa, Schima superba, and Acacia auriculiformis) photosynthetic stems, and the sap flux (Js) and chlorophyll fluorescence parameters for these species were measured. One-way ANOVA analysis showed that the Fv/Fm (Maximum photochemical quantum yield of PSII) and ΦPSII (effective photochemical quantum yield of PSII) values were lower in non-photosynthetic stem species compared to photosynthetic stem species. The linear regression analysis showed that Js,d (daytime sap flux) and Js,n (nighttime sap flux) of non-photosynthetic stem species was 87.7 and 60.9% of the stem photosynthetic species. Furthermore, for a given daytime transpiration water loss, total nighttime sap flux was higher in species with photosynthetic stems (SlopeSMA = 2.680) than in non-photosynthetic stems species (SlopeSMA = 1.943). These results mean that stem corticular photosynthesis has a possible effect on the nighttime water flow, highlighting the important eco-physiological relationship between nighttime sap flux and corticular photosynthesis. PMID:29416547

Exploration of the antioxidant system and photosynthetic system of a marine algicidal Bacillus and its effect on four harmful algal bloom species.

PubMed

Hou, Shaoling; Shu, Wanjiao; Tan, Shuo; Zhao, Ling; Yin, Pinghe

2016-01-01

A novel marine bacterium, strain B1, initially showed 96.4% algicidal activity against Phaeocystis globosa. Under this situation, 3 other harmful algal species (Skeletonema costatum, Heterosigma akashiwo, and Prorocentrum donghaiense) were chosen to study the algicidal effects of strain B1, and the algicidal activities were 91.4%, 90.7%, and 90.6%, respectively. To explore the algicidal mechanism of strain B1 on these 4 harmful algal species, the characteristics of the antioxidant system and photosynthetic system were studied. Sensitivity to strain B1 supernatant, enzyme activity, and gene expression varied with algal species, while the algicidal patterns were similar. Strain B1 supernatant increased malondialdehyde contents; decreased chlorophyll a contents; changed total antioxidant and superoxide dismutase activity; and restrained psbA, psbD, and rbcL genes expression, which eventually resulted in the algal cells death. The algicidal procedure was observed using field emission scanning electron microscopy, which indicated that algal cells were lysed and cellular substances were released. These findings suggested that the antioxidant and photosynthetic system of these 4 algal species was destroyed under strain B1 supernatant stress. This is the first report to explore and compare the mechanism of a marine Bacillus against harmful algal bloom species of covered 4 phyla.

Oxygen concentration inside a functioning photosynthetic cell.

PubMed

Kihara, Shigeharu; Hartzler, Daniel A; Savikhin, Sergei

2014-05-06

The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the oxygen level in the Earth's atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Regulation of the photosynthetic apparatus under fluctuating growth light.

PubMed

Tikkanen, Mikko; Grieco, Michele; Nurmi, Markus; Rantala, Marjaana; Suorsa, Marjaana; Aro, Eva-Mari

2012-12-19

Safe and efficient conversion of solar energy to metabolic energy by plants is based on tightly inter-regulated transfer of excitation energy, electrons and protons in the photosynthetic machinery according to the availability of light energy, as well as the needs and restrictions of metabolism itself. Plants have mechanisms to enhance the capture of energy when light is limited for growth and development. Also, when energy is in excess, the photosynthetic machinery slows down the electron transfer reactions in order to prevent the production of reactive oxygen species and the consequent damage of the photosynthetic machinery. In this opinion paper, we present a partially hypothetical scheme describing how the photosynthetic machinery controls the flow of energy and electrons in order to enable the maintenance of photosynthetic activity in nature under continual fluctuations in white light intensity. We discuss the roles of light-harvesting II protein phosphorylation, thermal dissipation of excess energy and the control of electron transfer by cytochrome b(6)f, and the role of dynamically regulated turnover of photosystem II in the maintenance of the photosynthetic machinery. We present a new hypothesis suggesting that most of the regulation in the thylakoid membrane occurs in order to prevent oxidative damage of photosystem I.

Characterization of the cellulose-degrading bacterium NCIMB 10462

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dees, C.; Scott, T.C.; Phelps, T.J.

The gram-negative cellulase-producing bacterium NCIMB 10462 has been previously named Pseudomonas fluorescens subsp. or var. cellulose. Because of renewed interest in cellulose-degrading bacteria for use in the bioconversion of cellulose to chemical feed stocks and fuels, we re-examined the characteristics of this microorganism to determine its true metabolic potential. Metabolic and physical characterization of NCIMB 10462 revealed that this is an alkalophilic, non-fermentative, gram-negative, oxidase-positive, motile, cellulose-degrading bacterium. The aerobic substrate utilization profile of this bacterium has few characteristics consistent with a classification of P. fluorescens and a very low probability match with the genus Sphingomonas. However, total lipid analysismore » did not reveal that any sphingolipid bases are produced by this bacterium. NCIMB 10462 grows best aerobically, but also grows well in complex media under reducing conditions. NCIMB 10462 grows slowly under anaerobic conditions on complex media, but growth on cellulosic media occurred only under aerobic conditions. Total fatty acid analysis (MIDI) of NCIMB 10462 failed to group this bacterium with a known pseudomonas species. However, fatty acid analysis of the bacteria when grown at temperatures below 37{degrees}C suggest that the organism is a pseudomonad. Since a predominant characteristic of this bacterium is its ability to degrade cellulose, we suggest that it be called Pseudomonas cellulosa.« less

Effects of photosynthetic photon flux density, frequency, duty ratio, and their interactions on net photosynthetic rate of cos lettuce leaves under pulsed light: explanation based on photosynthetic-intermediate pool dynamics.

PubMed

Jishi, Tomohiro; Matsuda, Ryo; Fujiwara, Kazuhiro

2018-06-01

Square-wave pulsed light is characterized by three parameters, namely average photosynthetic photon flux density (PPFD), pulsed-light frequency, and duty ratio (the ratio of light-period duration to that of the light-dark cycle). In addition, the light-period PPFD is determined by the averaged PPFD and duty ratio. We investigated the effects of these parameters and their interactions on net photosynthetic rate (P n ) of cos lettuce leaves for every combination of parameters. Averaged PPFD values were 0-500 µmol m -2  s -1 . Frequency values were 0.1-1000 Hz. White LED arrays were used as the light source. Every parameter affected P n and interactions between parameters were observed for all combinations. The P n under pulsed light was lower than that measured under continuous light of the same averaged PPFD, and this difference was enhanced with decreasing frequency and increasing light-period PPFD. A mechanistic model was constructed to estimate the amount of stored photosynthetic intermediates over time under pulsed light. The results indicated that all effects of parameters and their interactions on P n were explainable by consideration of the dynamics of accumulation and consumption of photosynthetic intermediates.

Optimization of Light-Harvesting Pigment Improves Photosynthetic Efficiency.

PubMed

Jin, Honglei; Li, Mengshu; Duan, Sujuan; Fu, Mei; Dong, Xiaoxiao; Liu, Bing; Feng, Dongru; Wang, Jinfa; Wang, Hong-Bin

2016-11-01

Maximizing light capture by light-harvesting pigment optimization represents an attractive but challenging strategy to improve photosynthetic efficiency. Here, we report that loss of a previously uncharacterized gene, HIGH PHOTOSYNTHETIC EFFICIENCY1 (HPE1), optimizes light-harvesting pigments, leading to improved photosynthetic efficiency and biomass production. Arabidopsis (Arabidopsis thaliana) hpe1 mutants show faster electron transport and increased contents of carbohydrates. HPE1 encodes a chloroplast protein containing an RNA recognition motif that directly associates with and regulates the splicing of target RNAs of plastid genes. HPE1 also interacts with other plastid RNA-splicing factors, including CAF1 and OTP51, which share common targets with HPE1. Deficiency of HPE1 alters the expression of nucleus-encoded chlorophyll-related genes, probably through plastid-to-nucleus signaling, causing decreased total content of chlorophyll (a+b) in a limited range but increased chlorophyll a/b ratio. Interestingly, this adjustment of light-harvesting pigment reduces antenna size, improves light capture, decreases energy loss, mitigates photodamage, and enhances photosynthetic quantum yield during photosynthesis. Our findings suggest a novel strategy to optimize light-harvesting pigments that improves photosynthetic efficiency and biomass production in higher plants. © 2016 American Society of Plant Biologists. All Rights Reserved.

Enhanced practical photosynthetic CO2 mitigation

DOEpatents

Bayless, David J.; Vis-Chiasson, Morgan L.; Kremer, Gregory G.

2003-12-23

This process is unique in photosynthetic carbon sequestration. An on-site biological sequestration system directly decreases the concentration of carbon-containing compounds in the emissions of fossil generation units. In this process, photosynthetic microbes are attached to a growth surface arranged in a containment chamber that is lit by solar photons. A harvesting system ensures maximum organism growth and rate of CO.sub.2 uptake. Soluble carbon and nitrogen concentrations delivered to the cyanobacteria are enhanced, further increasing growth rate and carbon utilization.

Tree Species with Photosynthetic Stems Have Greater Nighttime Sap Flux.

PubMed

Chen, Xia; Gao, Jianguo; Zhao, Ping; McCarthy, Heather R; Zhu, Liwei; Ni, Guangyan; Ouyang, Lei

2018-01-01

An increasing body of evidence has shown that nighttime sap flux occurs in most plants, but the physiological implications and regulatory mechanism are poorly known. The significance of corticular photosynthesis has received much attention during the last decade, however, the knowledge of the relationship between corticular photosynthesis and nocturnal stem sap flow is limited at present. In this study, we divided seven tree species into two groups according to different photosynthetic capabilities: trees of species with ( Castanopsis hystrix, Michelia macclurei, Eucalyptus citriodora , and Eucalyptus grandis × urophylla ) and without ( Castanopsis fissa, Schima superba , and Acacia auriculiformis ) photosynthetic stems, and the sap flux ( J s ) and chlorophyll fluorescence parameters for these species were measured. One-way ANOVA analysis showed that the F v / F m (Maximum photochemical quantum yield of PSII) and Φ PSII (effective photochemical quantum yield of PSII) values were lower in non-photosynthetic stem species compared to photosynthetic stem species. The linear regression analysis showed that J s,d (daytime sap flux) and J s,n (nighttime sap flux) of non-photosynthetic stem species was 87.7 and 60.9% of the stem photosynthetic species. Furthermore, for a given daytime transpiration water loss, total nighttime sap flux was higher in species with photosynthetic stems (Slope SMA = 2.680) than in non-photosynthetic stems species (Slope SMA = 1.943). These results mean that stem corticular photosynthesis has a possible effect on the nighttime water flow, highlighting the important eco-physiological relationship between nighttime sap flux and corticular photosynthesis.

Excitons in intact cells of photosynthetic bacteria.

PubMed

Freiberg, Arvi; Pajusalu, Mihkel; Rätsep, Margus

2013-09-26

Live cells and regular crystals seem fundamentally incompatible. Still, effects characteristic to ideal crystals, such as coherent sharing of excitation, have been recently used in many studies to explain the behavior of several photosynthetic complexes, especially the inner workings of the light-harvesting apparatus of the oldest known photosynthetic organisms, the purple bacteria. To this date, there has been no concrete evidence that the same effects are instrumental in real living cells, leaving a possibility that this is an artifact of unnatural study conditions, not a real effect relevant to the biological operation of bacteria. Hereby, we demonstrate survival of collective coherent excitations (excitons) in intact cells of photosynthetic purple bacteria. This is done by using excitation anisotropy spectroscopy for tracking the temperature-dependent evolution of exciton bands in light-harvesting systems of increasing structural complexity. The temperature was gradually raised from 4.5 K to ambient temperature, and the complexity of the systems ranged from detergent-isolated complexes to complete bacterial cells. The results provide conclusive evidence that excitons are indeed one of the key elements contributing to the energetic and dynamic properties of photosynthetic organisms.

Protein structure, electron transfer and evolution of prokaryotic photosynthetic reaction centers

NASA Technical Reports Server (NTRS)

Blankenship, R. E.

1994-01-01

Photosynthetic reaction centers from a variety of organisms have been isolated and characterized. The groups of prokaryotic photosynthetic organisms include the purple bacteria, the filamentous green bacteria, the green sulfur bacteria and the heliobacteria as anoxygenic representatives as well as the cyanobacteria and prochlorophytes as oxygenic representatives. This review focuses on structural and functional comparisons of the various groups of photosynthetic reaction centers and considers possible evolutionary scenarios to explain the diversity of existing photosynthetic organisms.

Seasonal photosynthetic activity in evergreen conifer leaves monitored with spectral reflectance

NASA Astrophysics Data System (ADS)

Wong, C. Y.; Gamon, J. A.

2013-12-01

Boreal evergreen conifers must maintain photosynthetic systems in environments where temperatures vary greatly across seasons from high temperatures in the summer to freezing levels in the winter. This involves seasonal downregulation and photoprotection during periods of extreme temperatures. To better understand this downregulation, seasonal dynamics of photosynthesis of lodgepole (Pinus contorta D.) and ponderosa pine (Pinus ponderosa D.) were monitored in Edmonton, Canada over two years. Spectral reflectance at the leaf and stand scales was measured weekly and the Photochemical Reflectance Index (PRI), often used as a proxy for chlorophyll and carotenoid pigment levels and photosynthetic light-use efficiency (LUE), was used to track the seasonal dynamics of photosynthetic activity. Additional physiological measurements included leaf pigment content, chlorophyll fluorescence, and gas exchange. All the metrics indicate large seasonal changes in photosynthetic activity, with a sharp transition from winter downregulation to active photosynthesis in the spring and a more gradual fall transition into winter. The PRI was a good indicator of several other variables including seasonally changing photosynthetic activity, chlorophyll fluorescence, photosynthetic LUE, and pigment pool sizes. Over the two-year cycle, PRI was primarily driven by changes in constitutive (chlorophyll:carotenoid) pigment levels correlated with seasonal photosynthetic activity, with a much smaller variation caused by diurnal changes in xanthophyll cycle activity (conversion between violaxanthin & zeaxanthin). Leaf and canopy scale PRI measurements exhibited parallel responses during the winter-spring transition. Together, our findings indicate that evergreen conifers photosynthetic system possesses a remarkable degree of resilience in response to large temperature changes across seasons, and that optical remote sensing can be used to observe the seasonal effects on photosynthesis and

Single Bacterium Detection Using Sers

NASA Astrophysics Data System (ADS)

Gonchukov, S. A.; Baikova, T. V.; Alushin, M. V.; Svistunova, T. S.; Minaeva, S. A.; Ionin, A. A.; Kudryashov, S. I.; Saraeva, I. N.; Zayarny, D. A.

2016-02-01

This work is devoted to the study of a single Staphylococcus aureus bacterium detection using surface-enhanced Raman spectroscopy (SERS) and resonant Raman spectroscopy (RS). It was shown that SERS allows increasing sensitivity of predominantly low frequency lines connected with the vibrations of Amide, Proteins and DNA. At the same time the lines of carotenoids inherent to this kind of bacterium are well-detected due to the resonance Raman scattering mechanism. The reproducibility and stability of Raman spectra strongly depend on the characteristics of nanostructured substrate, and molecular structure and size of the tested biological object.

Apparatus and method for measuring single cell and sub-cellular photosynthetic efficiency

DOEpatents

Davis, Ryan Wesley; Singh, Seema; Wu, Huawen

2013-07-09

Devices for measuring single cell changes in photosynthetic efficiency in algal aquaculture are disclosed that include a combination of modulated LED trans-illumination of different intensities with synchronized through objective laser illumination and confocal detection. Synchronization and intensity modulation of a dual illumination scheme were provided using a custom microcontroller for a laser beam block and constant current LED driver. Therefore, single whole cell photosynthetic efficiency, and subcellular (diffraction limited) photosynthetic efficiency measurement modes are permitted. Wide field rapid light scanning actinic illumination is provided for both by an intensity modulated 470 nm LED. For the whole cell photosynthetic efficiency measurement, the same LED provides saturating pulses for generating photosynthetic induction curves. For the subcellular photosynthetic efficiency measurement, a switched through objective 488 nm laser provides saturating pulses for generating photosynthetic induction curves. A second near IR LED is employed to generate dark adapted states in the system under study.

Global scale environmental control of plant photosynthetic capacity

DOE PAGES

Ali, Ashehad; Xu, Chonggang; Rogers, Alistair; ...

2015-12-01

Photosynthetic capacity, determined by light harvesting and carboxylation reactions, is a key plant trait that determines the rate of photosynthesis; however, in Earth System Models (ESMs) at a reference temperature, it is either a fixed value for a given plant functional type or derived from a linear function of leaf nitrogen content. In this study, we conducted a comprehensive analysis that considered correlations of environmental factors with photosynthetic capacity as determined by maximum carboxylation (V c,m) rate scaled to 25°C (i.e., V c,25; μmol CO 2·m –2·s –1) and maximum electron transport rate (Jmax) scaled to 25°C (i.e., J 25;more » μmol electron·m –2·s –1) at the global scale. Our results showed that the percentage of variation in observed Vc,25 and J25 explained jointly by the environmental factors (i.e., day length, radiation, temperature, and humidity) were 2–2.5 times and 6–9 times of that explained by area-based leaf nitrogen content, respectively. Environmental factors influenced photosynthetic capacity mainly through photosynthetic nitrogen use efficiency, rather than through leaf nitrogen content. The combination of leaf nitrogen content and environmental factors was able to explain ~56% and ~66% of the variation in V c,25 and J 25 at the global scale, respectively. As a result, our analyses suggest that model projections of plant photosynthetic capacity and hence land–atmosphere exchange under changing climatic conditions could be substantially improved if environmental factors are incorporated into algorithms used to parameterize photosynthetic capacity in ESMs.« less

Phototrophic Fe(II)-oxidation in the chemocline of a ferruginous meromictic lake

PubMed Central

Walter, Xavier A.; Picazo, Antonio; Miracle, Maria R.; Vicente, Eduardo; Camacho, Antonio; Aragno, Michel; Zopfi, Jakob

2014-01-01

Precambrian Banded Iron Formation (BIF) deposition was conventionally attributed to the precipitation of iron-oxides resulting from the abiotic reaction of ferrous iron (Fe(II)) with photosynthetically produced oxygen. Earliest traces of oxygen date from 2.7 Ga, thus raising questions as to what may have caused BIF precipitation before oxygenic photosynthesis evolved. The discovery of anoxygenic phototrophic bacteria thriving through the oxidation of Fe(II) has provided support for a biological origin for some BIFs, but despite reports suggesting that anoxygenic phototrophs may oxidize Fe(II) in the environment, a model ecosystem of an ancient ocean where they are demonstrably active was lacking. Here we show that anoxygenic phototrophic bacteria contribute to Fe(II) oxidation in the water column of the ferruginous sulfate-poor, meromictic lake La Cruz (Spain). We observed in-situ photoferrotrophic activity through stimulation of phototrophic carbon uptake in the presence of Fe(II), and determined light-dependent Fe(II)-oxidation by the natural chemocline microbiota. Moreover, a photoferrotrophic bacterium most closely related to Chlorobium ferrooxidans was enriched from the ferruginous water column. Our study for the first time demonstrates a direct link between anoxygenic photoferrotrophy and the anoxic precipitation of Fe(III)-oxides in a ferruginous water column, providing a plausible mechanism for the bacterial origin of BIFs before the advent of free oxygen. However, photoferrotrophs represent only a minor fraction of the anoxygenic phototrophic community with the majority apparently thriving by sulfur cycling, despite the very low sulfur content in the ferruginous chemocline of Lake La Cruz. PMID:25538702

The Photosynthetic Cycle

DOE R&D Accomplishments Database

Calvin, Melvin

1955-03-21

A cyclic sequence of transformations, including the carboxylation of RuDP (ribulose diphosphate) and its re-formation, has been deduced as the route for the creation of reduced carbon compounds in photosynthetic organisms. With the demonstration of RuDP as substrate for the carboxylation in a cell-free system, each of the reactions has now been carried out independently in vitro. Further purification of this last enzyme system has confirmed the deduction that the carboxylation of RuDP leads directly to the two molecules of PGA (phosphoglyceric acid) involving an internal dismutation and suggesting the name "carboxydismutase" for the enzyme. As a consequence of this knowledge of each of the steps in the photosynthetic CO{sub 2} reduction cycle, it is possible to define the reagent requirements to maintain it. The net requirement for the reduction of one molecule of CO{sub 2} is four equivalents of [H]and three molecules of ATP (adenine triphosphate). These must ultimately be supplied by the photochemical reaction. Some possible ways in which this may be accomplished are discussed.

Photosynthetic performance of restored and natural mangroves under different environmental constraints.

PubMed

Rovai, André Scarlate; Barufi, José Bonomi; Pagliosa, Paulo Roberto; Scherner, Fernando; Torres, Moacir Aluísio; Horta, Paulo Antunes; Simonassi, José Carlos; Quadros, Daiane Paula Cunha; Borges, Daniel Lázaro Gallindo; Soriano-Sierra, Eduardo Juan

2013-10-01

We hypothesized that the photosynthetic performance of mangrove stands restored by the single planting of mangroves species would be lowered due to residual stressors. The photosynthetic parameters of the vegetation of three planted mangrove stands, each with a different disturbance history, were compared to reference sites and correlated with edaphic environmental variables. A permutational analysis of variance showed significant interaction when the factors were compared, indicating that the photosynthetic parameters of the restoration areas differed from the reference sites. A univariate analysis of variance showed that all the photosynthetic parameters differed between sites and treatments, except for photosynthetic efficiency (αETR). The combination of environmental variables that best explained the variations observed in the photosynthetic performance indicators were Cu, Pb and elevation disruptions. Fluorescence techniques proved efficient in revealing important physiological differences, representing a powerful tool for rapid analysis of the effectiveness of initiatives aimed at restoring coastal environments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Flux coupling and transcriptional regulation within the metabolic network of the photosynthetic bacterium Synechocystis sp. PCC6803.

PubMed

Montagud, Arnau; Zelezniak, Aleksej; Navarro, Emilio; de Córdoba, Pedro Fernández; Urchueguía, Javier F; Patil, Kiran Raosaheb

2011-03-01

Synechocystis sp. PCC6803 is a model cyanobacterium capable of producing biofuels with CO(2) as carbon source and with its metabolism fueled by light, for which it stands as a potential production platform of socio-economic importance. Compilation and characterization of Synechocystis genome-scale metabolic model is a pre-requisite toward achieving a proficient photosynthetic cell factory. To this end, we report iSyn811, an upgraded genome-scale metabolic model of Synechocystis sp. PCC6803 consisting of 956 reactions and accounting for 811 genes. To gain insights into the interplay between flux activities and metabolic physiology, flux coupling analysis was performed for iSyn811 under four different growth conditions, viz., autotrophy, mixotrophy, heterotrophy, and light-activated heterotrophy (LH). Initial steps of carbon acquisition and catabolism formed the versatile center of the flux coupling networks, surrounded by a stable core of pathways leading to biomass building blocks. This analysis identified potential bottlenecks for hydrogen and ethanol production. Integration of transcriptomic data with the Synechocystis flux coupling networks lead to identification of reporter flux coupling pairs and reporter flux coupling groups - regulatory hot spots during metabolic shifts triggered by the availability of light. Overall, flux coupling analysis provided insight into the structural organization of Synechocystis sp. PCC6803 metabolic network toward designing of a photosynthesis-based production platform. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Noise induced quantum effects in photosynthetic complexes

NASA Astrophysics Data System (ADS)

Dorfman, Konstantin; Voronine, Dmitri; Mukamel, Shaul; Scully, Marlan

2012-02-01

Recent progress in coherent multidimensional optical spectroscopy revealed effects of quantum coherence coupled to population leading to population oscillations as evidence of quantum transport. Their description requires reevaluation of the currently used methods and approximations. We identify couplings between coherences and populations as the noise-induced cross-terms in the master equation generated via Agarwal-Fano interference that have been shown earlier to enhance the quantum yield in a photocell. We investigated a broad range of typical parameter regimes, which may be applied to a variety of photosynthetic complexes. We demonstrate that quantum coherence may be induced in photosynthetic complexes under natural conditions of incoherent light from the sun. This demonstrates that a photosynthetic reaction center may be viewed as a biological quantum heat engine that transforms high-energy thermal photon radiation into low entropy electron flux.

Coral bleaching independent of photosynthetic activity.

PubMed

Tolleter, Dimitri; Seneca, François O; DeNofrio, Jan C; Krediet, Cory J; Palumbi, Stephen R; Pringle, John R; Grossman, Arthur R

2013-09-23

The global decline of reef-building corals is due in part to the loss of algal symbionts, or "bleaching," during the increasingly frequent periods of high seawater temperatures. During bleaching, endosymbiotic dinoflagellate algae (Symbiodinium spp.) either are lost from the animal tissue or lose their photosynthetic pigments, resulting in host mortality if the Symbiodinium populations fail to recover. The >1,000 studies of the causes of heat-induced bleaching have focused overwhelmingly on the consequences of damage to algal photosynthetic processes, and the prevailing model for bleaching invokes a light-dependent generation of toxic reactive oxygen species (ROS) by heat-damaged chloroplasts as the primary trigger. However, the precise mechanisms of bleaching remain unknown, and there is evidence for involvement of multiple cellular processes. In this study, we asked the simple question of whether bleaching can be triggered by heat in the dark, in the absence of photosynthetically derived ROS. We used both the sea anemone model system Aiptasia and several species of reef-building corals to demonstrate that symbiont loss can occur rapidly during heat stress in complete darkness. Furthermore, we observed damage to the photosynthetic apparatus under these conditions in both Aiptasia endosymbionts and cultured Symbiodinium. These results do not directly contradict the view that light-stimulated ROS production is important in bleaching, but they do show that there must be another pathway leading to bleaching. Elucidation of this pathway should help to clarify bleaching mechanisms under the more usual conditions of heat stress in the light. Copyright © 2013 Elsevier Ltd. All rights reserved.

Tracking photosynthetic efficiency with narrow-band spectroradiometry

NASA Technical Reports Server (NTRS)

Gamon, John A.; Field, Christopher B.

1992-01-01

Narrow-waveband spectroradiometry presents the possibility of detecting subtle signals closely related to the current physiological state of vegetation. One such signal related to the epoxidation state of the xanthophyll cycle pigments, violaxanthin, antheraxanthin, and zeaxanthin is discussed. Recent advances in plant ecophysiology demonstrated a close relationship between these pigments and the regulatory state of photosystem 2 in photosynthesis. Our recent field studies of sunflower (Helianthus annuus) and oak (Quercus agrifolia) demonstrated that a 'xanthophyll signal' can be isolated from the diurnal reflectance spectra of intact canopies. Furthermore, the xanthophyll signal can be used to derive a 'physiological reflectance index' (PRI) that closely correlates with the actual photosynthetic efficiency (defined as the photosynthetic rate divided by the incident PAR) in closed canopies. If these signals were detectable in Airborne Visible/Infrared Imaging Spectrometers (AVIRIS) images, they could lead to improved remote estimates of photosynthetic fluxes.

High efficiency light harvesting by carotenoids in the LH2 complex from photosynthetic bacteria: unique adaptation to growth under low-light conditions.

PubMed

Magdaong, Nikki M; LaFountain, Amy M; Greco, Jordan A; Gardiner, Alastair T; Carey, Anne-Marie; Cogdell, Richard J; Gibson, George N; Birge, Robert R; Frank, Harry A

2014-09-25

Rhodopin, rhodopinal, and their glucoside derivatives are carotenoids that accumulate in different amounts in the photosynthetic bacterium, Rhodoblastus (Rbl.) acidophilus strain 7050, depending on the intensity of the light under which the organism is grown. The different growth conditions also have a profound effect on the spectra of the bacteriochlorophyll (BChl) pigments that assemble in the major LH2 light-harvesting pigment-protein complex. Under high-light conditions the well-characterized B800-850 LH2 complex is formed and accumulates rhodopin and rhodopin glucoside as the primary carotenoids. Under low-light conditions, a variant LH2, denoted B800-820, is formed, and rhodopinal and rhodopinal glucoside are the most abundant carotenoids. The present investigation compares and contrasts the spectral properties and dynamics of the excited states of rhodopin and rhodopinal in solution. In addition, the systematic differences in pigment composition and structure of the chromophores in the LH2 complexes provide an opportunity to explore the effect of these factors on the rate and efficiency of carotenoid-to-BChl energy transfer. It is found that the enzymatic conversion of rhodopin to rhodopinal by Rbl. acidophilus 7050 grown under low-light conditions results in nearly 100% carotenoid-to-BChl energy transfer efficiency in the LH2 complex. This comparative analysis provides insight into how photosynthetic systems are able to adapt and survive under challenging environmental conditions.

High Efficiency Light Harvesting by Carotenoids in the LH2 Complex from Photosynthetic Bacteria: Unique Adaptation to Growth under Low-Light Conditions

PubMed Central

2015-01-01

Rhodopin, rhodopinal, and their glucoside derivatives are carotenoids that accumulate in different amounts in the photosynthetic bacterium, Rhodoblastus (Rbl.) acidophilus strain 7050, depending on the intensity of the light under which the organism is grown. The different growth conditions also have a profound effect on the spectra of the bacteriochlorophyll (BChl) pigments that assemble in the major LH2 light-harvesting pigment–protein complex. Under high-light conditions the well-characterized B800-850 LH2 complex is formed and accumulates rhodopin and rhodopin glucoside as the primary carotenoids. Under low-light conditions, a variant LH2, denoted B800-820, is formed, and rhodopinal and rhodopinal glucoside are the most abundant carotenoids. The present investigation compares and contrasts the spectral properties and dynamics of the excited states of rhodopin and rhodopinal in solution. In addition, the systematic differences in pigment composition and structure of the chromophores in the LH2 complexes provide an opportunity to explore the effect of these factors on the rate and efficiency of carotenoid-to-BChl energy transfer. It is found that the enzymatic conversion of rhodopin to rhodopinal by Rbl. acidophilus 7050 grown under low-light conditions results in nearly 100% carotenoid-to-BChl energy transfer efficiency in the LH2 complex. This comparative analysis provides insight into how photosynthetic systems are able to adapt and survive under challenging environmental conditions. PMID:25171303

Climate controls photosynthetic capacity more than leaf nitrogen contents

NASA Astrophysics Data System (ADS)

Ali, A. A.; Xu, C.; McDowell, N. G.

2013-12-01

Global vegetation models continue to lack the ability to make reliable predictions because the photosynthetic capacity varies a lot with growth conditions, season and among species. It is likely that vegetation models link photosynthetic capacity to concurrent changes in leaf nitrogen content only. To improve the predictions of the vegetation models, there is an urgent need to review species growth conditions and their seasonal response to changing climate. We sampled the global distribution of the Vcmax (maximum carboxylation rates) data of various species across different environmental gradients from the literature and standardized its value to 25 degree Celcius. We found that species explained the largest variation in (1) the photosynthetic capacity and (2) the proportion of nitrogen allocated for rubisco (PNcb). Surprisingly, climate variables explained more variations in photosynthetic capacity as well as PNcb than leaf nitrogen content and/or specific leaf area. The chief climate variables that explain variation in photosynthesis and PNcb were radiation, temperature and daylength. Our analysis suggests that species have the greatest control over photosynthesis and PNcb. Further, compared to leaf nitrogen content and/or specific leaf area, climate variables have more control over photosynthesis and PNcb. Therefore, climate variables should be incorporated in the global vegetation models when making predictions about the photosynthetic capacity.

Engineered photosynthetic bacteria, method of manufacture of biofuels

DOEpatents

Laible, Philip D.; Snyder, Seth W.

2016-09-13

The invention provides for a novel type of biofuel; a method for cleaving anchors from photosynthetic organisms; and a method for producing biofuels using photosynthetic organisms, the method comprising identifying photosynthesis co-factors and their anchors in the organisms; modifying the organisms to increase production of the anchors; accumulating biomass of the organisms in growth media; and harvesting the anchors.

Cyanobacteria as photosynthetic biocatalysts: a systems biology perspective.

PubMed

Gudmundsson, Steinn; Nogales, Juan

2015-01-01

The increasing need to replace oil-based products and to address global climate change concerns has triggered considerable interest in photosynthetic microorganisms. Cyanobacteria, in particular, have great potential as biocatalysts for fuels and fine-chemicals. During the last few years the biotechnological applications of cyanobacteria have experienced an unprecedented increase and the use of these photosynthetic organisms for chemical production is becoming a tangible reality. However, the field is still immature and many concerns about the economic feasibility of the biotechnological potential of cyanobacteria remain. In this review we describe recent successes in biofuel and fine-chemical production using cyanobacteria. We discuss the role of the photosynthetic metabolism and highlight the need for systems-level metabolic optimization in order to achieve the true potential of cyanobacterial biocatalysts.

Detection of Salmonella bacterium in drinking water using microring resonator.

PubMed

Bahadoran, Mahdi; Noorden, Ahmad Fakhrurrazi Ahmad; Mohajer, Faeze Sadat; Abd Mubin, Mohamad Helmi; Chaudhary, Kashif; Jalil, Muhammad Arif; Ali, Jalil; Yupapin, Preecha

2016-01-01

A new microring resonator system is proposed for the detection of the Salmonella bacterium in drinking water, which is made up of SiO2-TiO2 waveguide embedded inside thin film layer of the flagellin. The change in refractive index due to the binding of the Salmonella bacterium with flagellin layer causes a shift in the output signal wavelength and the variation in through and drop port's intensities, which leads to the detection of Salmonella bacterium in drinking water. The sensitivity of proposed sensor for detecting of Salmonella bacterium in water solution is 149 nm/RIU and the limit of detection is 7 × 10(-4)RIU.

Growth and photosynthetic responses of wheat plants grown in space

NASA Technical Reports Server (NTRS)

Tripathy, B. C.; Brown, C. S.; Levine, H. G.; Krikorian, A. D.

1996-01-01

Growth and photosynthesis of wheat (Triticum aestivum L. cv Super Dwarf) plants grown onboard the space shuttle Discovery for 10 d were examined. Compared to ground control plants, the shoot fresh weight of space-grown seedlings decreased by 25%. Postflight measurements of the O2 evolution/photosynthetic photon flux density response curves of leaf samples revealed that the CO2-saturated photosynthetic rate at saturating light intensities in space-grown plants declined 25% relative to the rate in ground control plants. The relative quantum yield of CO2-saturated photosynthetic O2 evolution measured at limiting light intensities was not significantly affected. In space-grown plants, the light compensation point of the leaves increased by 33%, which likely was due to an increase (27%) in leaf dark-respiration rates. Related experiments with thylakoids isolated from space-grown plants showed that the light-saturated photosynthetic electron transport rate from H2O through photosystems II and I was reduced by 28%. These results demonstrate that photosynthetic functions are affected by the microgravity environment.

Photosynthetic strategies of two Mojave Desert shrubs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleinkopf, G.E.; Hartsock, T.L.; Wallace, A.

1980-01-01

Photosynthetic production of two Mojave Desert shrubs was measured under natural growing conditions. Measurements of photosynthesis, transpiration, resistances to water vapor flux, soil moisture potential, and tissue water potential were made. Atriplex canescens (Pursh) Nutt., a member of the C/sub 4/ biochemical carbon dioxide fixation group was highly competitive in growth rate and production during conditions of adequate soil moisture. As soil moisture conditions declined to minus 40 bars, the net photosynthetic rate of Atriplex decreased to zero. However, the C/sub 3/ shrub species Larrea tridentata (Sesse and Moc. ex DC.) Cov. was able to maintain positive net photosynthetic productionmore » during conditions of high temperature and extreme low soil moisture through the major part of the season. The comparative advantages of the C/sub 4/ versus the C/sub 3/ pathway of carbon fixation was lost between these two species as the soil moisture potential declined to minus 40 bars. Desert plants have diffferent strategies for survival, one of the strategies being the C/sub 4/ biochemical carbon fixation pathway. However, many of the plants are members of the C/sub 3/ group. In this instance, the C/sub 4/ fixation pathway does not confer an added advantage to the productivity of the species in the Mojave Desert. Species distribution based on comparative photosynthetic production is discussed« less

Photosynthetic antenna engineering to improve crop yields.

PubMed

Kirst, Henning; Gabilly, Stéphane T; Niyogi, Krishna K; Lemaux, Peggy G; Melis, Anastasios

2017-05-01

Evidence shows that decreasing the light-harvesting antenna size of the photosystems in tobacco helps to increase the photosynthetic productivity and plant canopy biomass accumulation under high-density cultivation conditions. Decreasing, or truncating, the chlorophyll antenna size of the photosystems can theoretically improve photosynthetic solar energy conversion efficiency and productivity in mass cultures of algae or plants by up to threefold. A Truncated Light-harvesting chlorophyll Antenna size (TLA), in all classes of photosynthetic organisms, would help to alleviate excess absorption of sunlight and the ensuing wasteful non-photochemical dissipation of excitation energy. Thus, solar-to-biomass energy conversion efficiency and photosynthetic productivity in high-density cultures can be increased. Applicability of the TLA concept was previously shown in green microalgae and cyanobacteria, but it has not yet been demonstrated in crop plants. In this work, the TLA concept was applied in high-density tobacco canopies. The work showed a 25% improvement in stem and leaf biomass accumulation for the TLA tobacco canopies over that measured with their wild-type counterparts grown under the same ambient conditions. Distinct canopy appearance differences are described between the TLA and wild type tobacco plants. Findings are discussed in terms of concept application to crop plants, leading to significant improvements in agronomy, agricultural productivity, and application of photosynthesis for the generation of commodity products in crop leaves.

Towards autotrophic tissue engineering: Photosynthetic gene therapy for regeneration.

PubMed

Chávez, Myra Noemi; Schenck, Thilo Ludwig; Hopfner, Ursula; Centeno-Cerdas, Carolina; Somlai-Schweiger, Ian; Schwarz, Christian; Machens, Hans-Günther; Heikenwalder, Mathias; Bono, María Rosa; Allende, Miguel L; Nickelsen, Jörg; Egaña, José Tomás

2016-01-01

The use of artificial tissues in regenerative medicine is limited due to hypoxia. As a strategy to overcome this drawback, we have shown that photosynthetic biomaterials can produce and provide oxygen independently of blood perfusion by generating chimeric animal-plant tissues during dermal regeneration. In this work, we demonstrate the safety and efficacy of photosynthetic biomaterials in vivo after engraftment in a fully immunocompetent mouse skin defect model. Further, we show that it is also possible to genetically engineer such photosynthetic scaffolds to deliver other key molecules in addition to oxygen. As a proof-of-concept, biomaterials were loaded with gene modified microalgae expressing the angiogenic recombinant protein VEGF. Survival of the algae, growth factor delivery and regenerative potential were evaluated in vitro and in vivo. This work proposes the use of photosynthetic gene therapy in regenerative medicine and provides scientific evidence for the use of engineered microalgae as an alternative to deliver recombinant molecules for gene therapy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Taxonomic characterization of the cellulose-degrading bacterium NCIB 10462

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dees, C.; Ringleberg, D.; Scott, T.C.

The gram negative cellulase-producing bacterium NCIB 10462 has been previously named Pseudomonas fluorescens subsp. or var. cellulosa. Since there is renewed interest in cellulose-degrading bacteria for use in bioconversion of cellulose to chemical feed stocks and fuels, we re-examined the characteristics of this microorganism to determine its proper taxonomic characterization and to further define it`s true metabolic potential. Metabolic and physical characterization of NCIB 10462 revealed that this was an alkalophilic, non-fermentative, gram negative, oxidase positive, motile, cellulose-degrading bacterium. The aerobic substrate utilization profile of this bacterium was found to have few characteristics consistent with a classification of P. fluorescensmore » with a very low probability match with the genus Sphingomonas. Total lipid analysis did not reveal that any sphingolipid bases are produced by this bacterium. NCIB 10462 was found to grow best aerobically but also grows well in complex media under reducing conditions. NCIB 10462 grew slowly under full anaerobic conditions on complex media but growth on cellulosic media was found only under aerobic conditions. Total fatty acid analysis (MIDI) of NCIB 10462 failed to group this bacterium with a known pseudomonas species. However, fatty acid analysis of the bacteria when grown at temperatures below 37{degrees}C suggest that the organism is a pseudomonad. Since a predominant characteristic of this bacterium is it`s ability to degrade cellulose, we suggest it be called Pseudomonas cellulosa.« less

Interactions between heavy metals and photosynthetic materials studied by optical techniques.

PubMed

Ventrella, Andrea; Catucci, Lucia; Piletska, Elena; Piletsky, Sergey; Agostiano, Angela

2009-11-01

In this work studies on rapid inhibitory interactions between heavy metals and photosynthetic materials at different organization levels were carried out by optical assay techniques, investigating the possibility of applications in the heavy metal detection field. Spinach chloroplasts, thylakoids and Photosystem II proteins were employed as biotools in combination with colorimetric assays based on dichlorophenol indophenole (DCIP) photoreduction and on fluorescence emission techniques. It was found that copper and mercury demonstrated a strong and rapid photosynthetic activity inhibition, that varied from proteins to membranes, while other metals like nickel, cobalt and manganese produced only slight inhibition effects on all tested photosynthetic materials. By emission measurements, only copper was found to rapidly influence the photosynthetic material signals. These findings give interesting information about the rapid effects of heavy metals on isolated photosynthetic samples, and are in addition to the literature data concerning the effects of growth in heavy metal enriched media.

Photosynthetic carbon metabolism in Enteromorpha compressa (Chlorophyta)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beer, S.; Shragge, B.

1987-12-01

The intertidal macroalga Enteromorpha compressa showed the ability to use HCO/sub 3//sup -/, as an exogenous inorganic carbon (Ci) source for photosynthesis. However, although the natural sea water concentration of this carbon form was saturating, additional CO/sub 2/ above ambient Ci levels doubled net photosynthetic rates. Therefore, the productivity of this alga, when submerged, is likely to be limited by Ci. When plants were exposed to air, photosynthetic rates saturated at air-levels of CO/sub 2/ during mild desiccation. Based on carbon fixing enzyme activities and Ci pulse-chase incorporation patterns, it was found that Enteromorpha is a C/sub 3/ plant. However,more » this alga did not show O/sub 2/ inhibited photosynthetic rates at natural sea water Ci conditions. It is suggested that such a C/sub 4/-like gas exchange response is due to the HCO/sub 3//sup -/ utilization system concentrating CO/sub 2/ intracellularly, thus alleviating apparent photorespiration.« less

Superradiance Transition and Nonphotochemical Quenching in Photosynthetic Complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berman, Gennady Petrovich; Nesterov, Alexander; Lopez, Gustavo

2015-04-23

Photosynthetic organisms have evolved protective strategies to allow them to survive in cases of intense sunlight fluctuation with the development of nonphotochemical quenching (NPQ). This process allows light harvesting complexes to transfer the excess sunlight energy to non-damaging quenching channels. This report compares the NPQ process with the superradiance transition (ST). We demonstrated that the maximum of the NPQ efficiency is caused by the ST to the sink associated with the CTS. However, experimental verifications are required in order to determine whether or not the NPQ regime is associated with the ST transition for real photosynthetic complexes. Indeed, it canmore » happen that, in the photosynthetic apparatus, the NPQ regime occurs in the “non-optimal” region of parameters, and it could be independent of the ST.« less

Optimization of Light-Harvesting Pigment Improves Photosynthetic Efficiency1[OPEN

PubMed Central

Jin, Honglei; Li, Mengshu; Duan, Sujuan; Fu, Mei; Dong, Xiaoxiao; Feng, Dongru; Wang, Jinfa

2016-01-01

Maximizing light capture by light-harvesting pigment optimization represents an attractive but challenging strategy to improve photosynthetic efficiency. Here, we report that loss of a previously uncharacterized gene, HIGH PHOTOSYNTHETIC EFFICIENCY1 (HPE1), optimizes light-harvesting pigments, leading to improved photosynthetic efficiency and biomass production. Arabidopsis (Arabidopsis thaliana) hpe1 mutants show faster electron transport and increased contents of carbohydrates. HPE1 encodes a chloroplast protein containing an RNA recognition motif that directly associates with and regulates the splicing of target RNAs of plastid genes. HPE1 also interacts with other plastid RNA-splicing factors, including CAF1 and OTP51, which share common targets with HPE1. Deficiency of HPE1 alters the expression of nucleus-encoded chlorophyll-related genes, probably through plastid-to-nucleus signaling, causing decreased total content of chlorophyll (a+b) in a limited range but increased chlorophyll a/b ratio. Interestingly, this adjustment of light-harvesting pigment reduces antenna size, improves light capture, decreases energy loss, mitigates photodamage, and enhances photosynthetic quantum yield during photosynthesis. Our findings suggest a novel strategy to optimize light-harvesting pigments that improves photosynthetic efficiency and biomass production in higher plants. PMID:27609860

Structure of Chlorobium tepidum sepiapterin reductase complex reveals the novel substrate binding mode for stereospecific production of L-threo-tetrahydrobiopterin.

PubMed

Supangat, Supangat; Seo, Kyung Hye; Choi, Yong Kee; Park, Young Shik; Son, Daeyoung; Han, Chang-deok; Lee, Kon Ho

2006-01-27

Sepiapterin reductase (SR) is involved in the last step of tetrahydrobiopterin (BH(4)) biosynthesis by reducing the di-keto group of 6-pyruvoyl tetrahydropterin. Chlorobium tepidum SR (cSR) generates a distinct BH(4) product, L-threo-BH(4) (6R-(1'S,2'S)-5,6,7,8-BH(4)), whereas animal enzymes produce L-erythro-BH(4) (6R-(1'R,2'S)-5,6,7,8-BH(4)) although it has high amino acid sequence similarities to the other animal enzymes. To elucidate the structural basis for the different reaction stereospecificities, we have determined the three-dimensional structures of cSR alone and complexed with NADP and sepiapterin at 2.1 and 1.7 A resolution, respectively. The overall folding of the cSR, the binding site for the cofactor NADP(H), and the positions of active site residues were quite similar to the mouse and the human SR. However, significant differences were found in the substrate binding region of the cSR. In comparison to the mouse SR complex, the sepiapterin in the cSR is rotated about 180 degrees around the active site and bound between two aromatic side chains of Trp-196 and Phe-99 so that its pterin ring is shifted to the opposite side, but its side chain position is not changed. The swiveled sepiapterin binding results in the conversion of the side chain configuration, exposing the opposite face for hydride transfer from NADPH. The different sepiapterin binding mode within the conserved catalytic architecture presents a novel strategy of switching the reaction stereospecificities in the same protein fold.

The Relationship between Anatomy and Photosynthetic Performance of Heterobaric Leaves1

PubMed Central

Nikolopoulos, Dimosthenis; Liakopoulos, Georgios; Drossopoulos, Ioannis; Karabourniotis, George

2002-01-01

Heterobaric leaves show heterogeneous pigmentation due to the occurrence of a network of transparent areas that are created from the bundle sheaths extensions (BSEs). Image analysis showed that the percentage of photosynthetically active leaf area (Ap) of the heterobaric leaves of 31 plant species was species dependent, ranging from 91% in Malva sylvestris to only 48% in Gynerium sp. Although a significant portion of the leaf surface does not correspond to photosynthetic tissue, the photosynthetic capacity of these leaves, expressed per unit of projected area (Pmax), was not considerably affected by the size of their transparent leaf area (At). This means that the photosynthetic capacity expressed per Ap (P*max) should increase with At. Moreover, the expression of P*max could be allowing the interpretation of the photosynthetic performance in relation to some critical anatomical traits. The P*max, irrespective of plant species, correlated with the specific leaf transparent volume (λt), as well as with the transparent leaf area complexity factor (CFAt), parameters indicating the volume per unit leaf area and length/density of the transparent tissues, respectively. Moreover, both parameters increased exponentially with leaf thickness, suggesting an essential functional role of BSEs mainly in thick leaves. The results of the present study suggest that although the Ap of an heterobaric leaf is reduced, the photosynthetic performance of each areole is increased, possibly due to the light transferring capacity of BSEs. This mechanism may allow a significant increase in leaf thickness and a consequent increase of the photosynthetic capacity per unit (projected) area, offering adaptive advantages in xerothermic environments. PMID:12011354

Characterization of a heat-tolerant Chlorella sp. GD mutant with enhanced photosynthetic CO2 fixation efficiency and its implication as lactic acid fermentation feedstock.

PubMed

Lee, Tse-Min; Tseng, Yu-Fei; Cheng, Chieh-Lun; Chen, Yi-Chuan; Lin, Chih-Sheng; Su, Hsiang-Yen; Chow, Te-Jin; Chen, Chun-Yen; Chang, Jo-Shu

2017-01-01

Fermentative production of lactic acid from algae-based carbohydrates devoid of lignin has attracted great attention for its potential as a suitable alternative substrate compared to lignocellulosic biomass. A Chlorella sp. GD mutant with enhanced thermo-tolerance was obtained by mutagenesis using N -methyl- N '-nitro- N -nitrosoguanidine to overcome outdoor high-temperature inhibition and it was used as a feedstock for fermentative lactic acid production. The indoor experiments showed that biomass, reducing sugar content, photosynthetic O 2 evolution rate, photosystem II activity ( F v / F m and F v '/ F m '), and chlorophyll content increased as temperature, light intensity, and CO 2 concentration increased. The mutant showed similar DIC affinity and initial slope of photosynthetic light response curve (α) as that of the wild type but had higher dissolved inorganic carbon (DIC) utilization capacity and maximum photosynthesis rate ( P max ). Moreover, the PSII activity ( F v '/ F m ') in the mutant remained normal without acclimation process after being transferred to photobioreactor. This suggests that efficient utilization of incident high light and enhanced carbon fixation with its subsequent flux to carbohydrates accumulation in the mutant contributes to higher sugar and biomass productivity under enriched CO 2 condition. The mutant was cultured outdoors in a photobioreactor with 6% CO 2 aeration in hot summer season in southern Taiwan. The harvested biomass was subjected to separate hydrolysis and fermentation (SHF) for lactic acid production with carbohydrate concentration equivalent to 20 g/L glucose using the lactic acid-producing bacterium Lactobacillus plantarum 23. The conversion rate and yield of lactic acid were 80% and 0.43 g/g Chlorella biomass, respectively. These results demonstrated that the thermo-tolerant Chlorella mutant with high photosynthetic efficiency and biomass productivity under hot outdoor condition is an efficient fermentative

Photosynthetic production of hydrogen. [Blue-green alga, Anabaena cylindrica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neil, G.; Nicholas, D.J.D.; Bockris, J.O.

A systematic investigation of photosynthetic hydrogen production using a blue-green alga, Anabaena cylindrica, was carried out. The results indicate that there are two important problems which must be overcome for large-scale hydrogen production using photosynthetic processes. These are (a) the development of a stable system, and (b) attainment of at least a fifty-fold increase in the rate of hydrogen evolution per unit area illuminated.

Leaf ontogeny and demography explain photosynthetic seasonality in Amazon evergreen forests

NASA Astrophysics Data System (ADS)

Wu, J.; Albert, L.; Lopes, A. P.; Restrepo-Coupe, N.; Hayek, M.; Wiedemann, K. T.; Guan, K.; Stark, S. C.; Prohaska, N.; Tavares, J. V.; Marostica, S. F.; Kobayashi, H.; Ferreira, M. L.; Campos, K.; Silva, R. D.; Brando, P. M.; Dye, D. G.; Huxman, T. E.; Huete, A. R.; Nelson, B. W.; Saleska, S. R.

2015-12-01

Photosynthetic seasonality couples the evolutionary ecology of plant leaves to large-scale rhythms of carbon and water exchanges that are important feedbacks to climate. However, the extent, magnitude, and controls on photosynthetic seasonality of carbon-rich tropical forests are poorly resolved, controversial in the remote sensing literature, and inadequately represented in most earth system models. Here we show that ecosystem-scale phenology (measured by photosynthetic capacity), rather than environmental seasonality, is the primary driver of photosynthetic seasonality at four Amazon evergreen forests spanning gradients in rainfall seasonality, forest composition, and flux seasonality. We further demonstrate that leaf ontogeny and demography explain most of this ecosystem phenology at two central Amazon evergreen forests, using a simple leaf-cohort canopy model that integrates eddy covariance-derived CO2 fluxes, novel near-surface camera-detected leaf phenology, and ground observations of litterfall and leaf physiology. The coordination of new leaf growth and old leaf divestment (litterfall) during the dry season shifts canopy composition towards younger leaves with higher photosynthetic efficiency, driving large seasonal increases (~27%) in ecosystem photosynthetic capacity. Leaf ontogeny and demography thus reconciles disparate observations of forest seasonality from leaves to eddy flux towers to satellites. Strategic incorporation of such whole-plant coordination processes as phenology and ontogeny will improve ecological, evolutionary and earth system theories describing tropical forests structure and function, allowing more accurate representation of forest dynamics and feedbacks to climate in earth system models.

Photosynthetic Photovoltaic Cells

DTIC Science & Technology

2007-06-21

OFF (T). B. SPR detection of the binding of Ni2+, RC, and cytochrome to NTA surface. The arrows indicate the periods of time ON (t) and OFF (1) when...photosynthesis. Structure and spectroscopy of reaction centers of purple bacteria . Physics Reports-Review Section of Physics Letters, 1997. 287(1-2): p. 2-247. 7...photosynthetic bacteria reaction centers. Journal of Photochemistry and Photobiology a-Chemistry, 1997. 111(1-3): p. 111-138. 27. Beratan, D.N., J.N. Betts, and

Stigmatellin Probes the Electrostatic Potential in the QB Site of the Photosynthetic Reaction Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerencsér, László; Boros, Bogáta; Derrien, Valerie

2015-01-01

The electrostatic potential in the secondary quinone (QB) binding site of the reaction center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides determines the rate and free energy change (driving force) of electron transfer to QB. It is controlled by the ionization states of residues in a strongly interacting cluster around the QB site. Reduction of the QB induces change of the ionization states of residues and binding of protons from the bulk. Stigmatellin, an inhibitor of the mitochondrial and photosynthetic respiratory chain, has been proven to be a unique voltage probe of the QB binding pocket. It binds to themore » QB site with high affinity, and the pK value of its phenolic group monitors the local electrostatic potential with high sensitivity. Investigations with different types of detergent as a model system of isolated RC revealed that the pK of stigmatellin was controlled overwhelmingly by electrostatic and slightly by hydrophobic interactions. Measurements showed a high pK value (>11) of stigmatellin in the QB pocket of the dark-state wild-type RC, indicating substantial negative potential. When the local electrostatics of the QB site was modulated by a single mutation, L213Asp/Ala, or double mutations, L213Asp-L212Glu/Ala-Ala (AA), the pK of stigmatellin dropped to 7.5 and 7.4, respectively, which corresponds to a >210 mV increase in the electrostatic potential relative to the wild-type RC. This significant pK drop (DpK > 3.5) decreased dramatically to (DpK > 0.75) in the RC of the compensatory mutant (AAþM44Asn/AAþM44Asp). Our results indicate that the L213Asp is the most important actor in the control of the electrostatic potential in the QB site of the dark-state wild-type RC, in good accordance with conclusions of former studies using theoretical calculations or light-induced charge recombination assay.« less

Photosynthetic Pigments in Diatoms

PubMed Central

Kuczynska, Paulina; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

2015-01-01

Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvesting pigments such as chlorophyll a, chlorophyll c, and fucoxanthin, there is a group of photoprotective carotenoids which includes β-carotene and the xanthophylls, diatoxanthin, diadinoxanthin, violaxanthin, antheraxanthin, and zeaxanthin, which are engaged in the xanthophyll cycle. Additionally, some intermediate products of biosynthetic pathways have been identified in diatoms as well as unusual pigments, e.g., marennine. Marine algae have become widely recognized as a source of unique bioactive compounds for potential industrial, pharmaceutical, and medical applications. In this review, we summarize current knowledge on diatom photosynthetic pigments complemented by some new insights regarding their physico-chemical properties, biological role, and biosynthetic pathways, as well as the regulation of pigment level in the cell, methods of purification, and significance in industries. PMID:26389924

[Engineering photosynthetic cyanobacterial chassis: a review].

PubMed

Wu, Qin; Chen, Lei; Wang, Jiangxin; Zhang, Weiwen

2013-08-01

Photosynthetic cyanobacteria possess a series of good properties, such as their abilities to capture solar energy for CO2 fixation, low nutritional requirements for growth, high growth rate, and relatively simple genetic background. Due to the high oil price and increased concern of the global warming in recent years, cyanobacteria have attracted widespread attention because they can serve as an 'autotrophic microbial factory' for producing renewable biofuels and fine chemicals directly from CO2. Particularly, significant progress has been made in applying synthetic biology techniques and strategies to construct and optimize cyanobacteria chassis. In this article, we critically summarized recent advances in developing new methods to optimize cyanobacteria chassis, improving cyanobacteria photosynthetic efficiency, and in constructing cyanobacteria chassis tolerant to products or environmental stresses. In addition, various industrial applications of cyanobacteria chassis are also discussed.

Non-photosynthetic plastids as hosts for metabolic engineering.

PubMed

Mellor, Silas Busck; Behrendorff, James B Y H; Nielsen, Agnieszka Zygadlo; Jensen, Poul Erik; Pribil, Mathias

2018-04-13

Using plants as hosts for production of complex, high-value compounds and therapeutic proteins has gained increasing momentum over the past decade. Recent advances in metabolic engineering techniques using synthetic biology have set the stage for production yields to become economically attractive, but more refined design strategies are required to increase product yields without compromising development and growth of the host system. The ability of plant cells to differentiate into various tissues in combination with a high level of cellular compartmentalization represents so far the most unexploited plant-specific resource. Plant cells contain organelles called plastids that retain their own genome, harbour unique biosynthetic pathways and differentiate into distinct plastid types upon environmental and developmental cues. Chloroplasts, the plastid type hosting the photosynthetic processes in green tissues, have proven to be suitable for high yield protein and bio-compound production. Unfortunately, chloroplast manipulation often affects photosynthetic efficiency and therefore plant fitness. In this respect, plastids of non-photosynthetic tissues, which have focused metabolisms for synthesis and storage of particular classes of compounds, might prove more suitable for engineering the production and storage of non-native metabolites without affecting plant fitness. This review provides the current state of knowledge on the molecular mechanisms involved in plastid differentiation and focuses on non-photosynthetic plastids as alternative biotechnological platforms for metabolic engineering. © 2018 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

Oxidation of Ethylene Glycol by a Salt-Requiring Bacterium

PubMed Central

Caskey, William H.; Taber, Willard A.

1981-01-01

Bacterium T-52, cultured on ethylene glycol, readily oxidized glycolate and glyoxylate and exhibited elevated activities of ethylene glycol dehydrogenase and glycolate oxidase. Labeled glyoxylate was identified in reaction mixtures containing [14C]-ethylene glycol, but no glycolate was detected. The most likely pathway of ethylene glycol catabolism by bacterium T-52 is sequential oxidation to glycolate and glyoxylate. PMID:16345810

Sun and Shade leaves, SIF, and Photosynthetic Capacity

NASA Astrophysics Data System (ADS)

Berry, J. A.; Badgley, G.

2016-12-01

Recent advances in retrieval of solar induced chlorophyll fluorescence (SIF) have opened up new possibilities for remote sensing of canopy physiology and structure. To date most of the emphasis has been placed on SIF as an indicator of stress and photosynthetic capacity. However, it is clear that canopy structure can also have an influence. To this point, simulations of SIF in land surface models tend to under predict observed variation in SIF. Also, large, systematic differences in SIF from different canopy types seem to correlate well with the photosynthetic capacity of these canopies. SIF emissions from pampered crops can be several-fold that from evergreen, needle-leaf forests. Yet, these may have similar vegetation indices and absorb a similar fraction of incident PAR. SIF photons produced in a conifer canopy do have a lower probability of escaping its dense, clumped foliage. However, this does not explain the correlated differences in photosynthetic rate and SIF. It is useful, in this regard, to consider the separate contributions of sun and shade leaves to the SIF emitted by a canopy. Sun leaves tend to be displayed to intercept the direct solar beam, and these highly illuminated leaves are often visible from above the canopy. Sun leaves produce more SIF and a large fraction of it escapes. Therefore, the intensity of SIF may be a sensitive indicator of the partitioning of absorbed PAR to sun and shade leaves. Many models account tor the different photosynthetic capacity of sun and shade leaves in calculating canopy responses. However, the fraction of leaves in each category is usually parameterized by an assumed leaf angle distribution (e.g. spherical). In reality, the sun/shade fraction can vary over a wide range, and it has been difficult to measure. SIF and possibly near-IR reflectance of canopies can be used to specify this key parameter with obvious importance to understanding photosynthetic rate.

Functional Implications of Photosystem II Crystal Formation in Photosynthetic Membranes*

PubMed Central

Tietz, Stefanie; Puthiyaveetil, Sujith; Enlow, Heather M.; Yarbrough, Robert; Wood, Magnus; Semchonok, Dmitry A.; Lowry, Troy; Li, Zhirong; Jahns, Peter; Boekema, Egbert J.; Lenhert, Steven; Niyogi, Krishna K.; Kirchhoff, Helmut

2015-01-01

The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystalline state is known to be triggered by abiotic factors, the functional significance of this protein organization has not yet been understood. Taking advantage of an Arabidopsis thaliana fatty acid desaturase mutant (fad5) that constitutively forms semicrystalline arrays, we systematically test the functional implications of protein crystals in photosynthetic membranes. Here, we show that the change into an ordered state facilitates molecular diffusion of photosynthetic components in crowded thylakoid membranes. The increased mobility of small lipophilic molecules like plastoquinone and xanthophylls has implications for diffusion-dependent electron transport and photoprotective energy-dependent quenching. The mobility of the large photosystem II supercomplexes, however, is impaired, leading to retarded repair of damaged proteins. Our results demonstrate that supramolecular changes into more ordered states have differing impacts on photosynthesis that favor either diffusion-dependent electron transport and photoprotection or protein repair processes, thus fine-tuning the photosynthetic energy conversion. PMID:25897076

Leaf maximum photosynthetic rate and venation are linked by hydraulics.

PubMed

Brodribb, Tim J; Feild, Taylor S; Jordan, Gregory J

2007-08-01

Leaf veins are almost ubiquitous across the range of terrestrial plant diversity, yet their influence on leaf photosynthetic performance remains uncertain. We show here that specific physical attributes of the vascular plumbing network are key limiters of the hydraulic and photosynthetic proficiency of any leaf. Following the logic that leaf veins evolved to bypass inefficient water transport through living mesophyll tissue, we examined the hydraulic pathway beyond the distal ends of the vein system as a possible limiter of water transport in leaves. We tested a mechanistic hypothesis that the length of this final traverse, as water moves from veins across the mesophyll to where it evaporates from the leaf, governs the hydraulic efficiency and photosynthetic carbon assimilation of any leaf. Sampling 43 species across the breadth of plant diversity from mosses to flowering plants, we found that the post-vein traverse as determined by characters such as vein density, leaf thickness, and cell shape, was strongly correlated with the hydraulic conductivity and maximum photosynthetic rate of foliage. The shape of this correlation provided clear support for the a priori hypothesis that vein positioning limits photosynthesis via its influence on leaf hydraulic efficiency.

Evolution of heliobacteria: implications for photosynthetic reaction center complexes

NASA Technical Reports Server (NTRS)

Vermaas, W. F.; Blankenship, R. E. (Principal Investigator)

1994-01-01

The evolutionary position of the heliobacteria, a group of green photosynthetic bacteria with a photosynthetic apparatus functionally resembling Photosystem I of plants and cyanobacteria, has been investigated with respect to the evolutionary relationship to Gram-positive bacteria and cyanobacteria. On the basis of 16S rRNA sequence analysis, the heliobacteria appear to be most closely related to Gram-positive bacteria, but also an evolutionary link to cyanobacteria is evident. Interestingly, a 46-residue domain including the putative sixth membrane-spanning region of the heliobacterial reaction center protein show rather strong similarity (33% identity and 72% similarity) to a region including the sixth membrane-spanning region of the CP47 protein, a chlorophyll-binding core antenna polypeptide of Photosystem II. The N-terminal half of the heliobacterial reaction center polypeptide shows a moderate sequence similarity (22% identity over 232 residues) with the CP47 protein, which is significantly more than the similarity with the Photosystem I core polypeptides in this region. An evolutionary model for photosynthetic reaction center complexes is discussed, in which an ancestral homodimeric reaction center protein (possibly resembling the heliobacterial reaction center protein) with 11 membrane-spanning regions per polypeptide has diverged to give rise to the core of Photosystem I, Photosystem II, and of the photosynthetic apparatus in green, purple, and heliobacteria.

Application of photosynthetic N(2)-fixing cyanobacteria to the CELSS program

NASA Technical Reports Server (NTRS)

Fry, Ian V.; Hrabeta, Jana; Dsouza, Joe; Packer, Lester

1987-01-01

The feasibility of using photosynthetic microalgae (cyanobacteria) as a subsystem component for the closed ecological life support system program, with particular emphasis on the manipulation of the biomass (protein/carbohydrate) was addressed. Using factors which retard growth rates, but not photosynthetic electron flux, the partitioning of photosynthetically derived reductant may be dictated towards CO2 fixation (carbohydrate formation) and away from N2 fixation (protein formation). Cold shock treatment of fairly dense cultures markedly increases the glycogen content from 1 to 35 percent (dry weight), and presents a useful technique to change the protein/carbohydrate ratio of these organisms to a more nutritionally acceptable form.

Photosynthetic Bradyrhizobia Are Natural Endophytes of the African Wild Rice Oryza breviligulata

PubMed Central

Chaintreuil, Clémence; Giraud, Eric; Prin, Yves; Lorquin, Jean; Bâ, Amadou; Gillis, Monique; de Lajudie, Philippe; Dreyfus, Bernard

2000-01-01

We investigated the presence of endophytic rhizobia within the roots of the wetland wild rice Oryza breviligulata, which is the ancestor of the African cultivated rice Oryza glaberrima. This primitive rice species grows in the same wetland sites as Aeschynomene sensitiva, an aquatic stem-nodulated legume associated with photosynthetic strains of Bradyrhizobium. Twenty endophytic and aquatic isolates were obtained at three different sites in West Africa (Senegal and Guinea) from nodal roots of O. breviligulata and surrounding water by using A. sensitiva as a trap legume. Most endophytic and aquatic isolates were photosynthetic and belonged to the same phylogenetic Bradyrhizobium/Blastobacter subgroup as the typical photosynthetic Bradyrhizobium strains previously isolated from Aeschynomene stem nodules. Nitrogen-fixing activity, measured by acetylene reduction, was detected in rice plants inoculated with endophytic isolates. A 20% increase in the shoot growth and grain yield of O. breviligulata grown in a greenhouse was also observed upon inoculation with one endophytic strain and one Aeschynomene photosynthetic strain. The photosynthetic Bradyrhizobium sp. strain ORS278 extensively colonized the root surface, followed by intercellular, and rarely intracellular, bacterial invasion of the rice roots, which was determined with a lacZ-tagged mutant of ORS278. The discovery that photosynthetic Bradyrhizobium strains, which are usually known to induce nitrogen-fixing nodules on stems of the legume Aeschynomene, are also natural true endophytes of the primitive rice O. breviligulata could significantly enhance cultivated rice production. PMID:11097925

On the photosynthetic potential in the very Early Archean oceans.

PubMed

Avila, Daile; Cardenas, Rolando; Martin, Osmel

2013-02-01

In this work we apply a mathematical model of photosynthesis to quantify the potential for photosynthetic life in the very Early Archean oceans. We assume the presence of oceanic blockers of ultraviolet radiation, specifically ferrous ions. For this scenario, our results suggest a potential for photosynthetic life greater than or similar to that in later eras/eons, such as the Late Archean and the current Phanerozoic eon.

Constrained parameterisation of photosynthetic capacity causes significant increase of modelled tropical vegetation surface temperature

NASA Astrophysics Data System (ADS)

Kattge, J.; Knorr, W.; Raddatz, T.; Wirth, C.

2009-04-01

Photosynthetic capacity is one of the most sensitive parameters of terrestrial biosphere models whose representation in global scale simulations has been severely hampered by a lack of systematic analyses using a sufficiently broad database. Due to its coupling to stomatal conductance changes in the parameterisation of photosynthetic capacity may potentially influence transpiration rates and vegetation surface temperature. Here, we provide a constrained parameterisation of photosynthetic capacity for different plant functional types in the context of the photosynthesis model proposed by Farquhar et al. (1980), based on a comprehensive compilation of leaf photosynthesis rates and leaf nitrogen content. Mean values of photosynthetic capacity were implemented into the coupled climate-vegetation model ECHAM5/JSBACH and modelled gross primary production (GPP) is compared to a compilation of independent observations on stand scale. Compared to the current standard parameterisation the root-mean-squared difference between modelled and observed GPP is substantially reduced for almost all PFTs by the new parameterisation of photosynthetic capacity. We find a systematic depression of NUE (photosynthetic capacity divided by leaf nitrogen content) on certain tropical soils that are known to be deficient in phosphorus. Photosynthetic capacity of tropical trees derived by this study is substantially lower than standard estimates currently used in terrestrial biosphere models. This causes a decrease of modelled GPP while it significantly increases modelled tropical vegetation surface temperatures, up to 0.8°C. These results emphasise the importance of a constrained parameterisation of photosynthetic capacity not only for the carbon cycle, but also for the climate system.

Insights into carotenoid dynamics in non-foliar photosynthetic tissues of avocado.

PubMed

Esteban, Raquel; Olascoaga, Beñat; Becerril, José M; García-Plazaola, José I

2010-09-01

Leaves are the main photosynthetically active tissues in most plants. However, stems and fruits are also important for the overall carbon balance of the plant because of their contribution to fixation of the CO(2) released by respiration. Photosynthesis could not be possible without a complete set of photoprotection mechanisms, which include the ubiquitous violaxanthin (V) cycle and the taxonomically restricted lutein epoxide (Lx) cycle. In this work, we characterise carotenoid stoichiometry in photosynthetic stems and fruits of avocado in comparison with that of leaves and specifically whether Lx is present in these tissues and also whether it is involved in a light-driven cycle. Avocado was selected as model species to study whether both cycles were functional in non-foliar photosynthetic structures (stems and fruits). An unusual pigment composition was observed in avocado fruit, with a high content of cis-V and cis-Lx, suggesting a different photosynthetic function. In stems, both xanthophylls de-epoxidated upon illumination, but only V recovered in the dark, indicating the existence of a possible 'truncated' Lx cycle. Lx in fruits was de-epoxidated only when its pool was higher than a threshold of 30 mmol mol(-1) chlorophyll, indicating a high non-photoconvertible pool of Lx. We conclude that, at least in stems, the dynamic regulation of photosynthetic activity could also depend on the Lx cycle.

Rhodoblastus sphagnicola sp. nov., a novel acidophilic purple non-sulfur bacterium from Sphagnum peat bog.

PubMed

Kulichevskaya, Irina S; Guzev, Vladimir S; Gorlenko, Vladimir M; Liesack, Werner; Dedysh, Svetlana N

2006-06-01

An isolate of purple non-sulfur bacteria was obtained from an acidic Sphagnum peat bog and designated strain RS(T). The colour of cell suspensions of this bacterium growing in the light under anaerobic conditions is purplish red. Cells of strain RS(T) are rod-shaped, 0.8-1.0 microm wide and 2.0-6.0 microm long, motile by means of polar flagella, reproduce by budding and have a tendency to form rosette-like clusters in older cultures. The cells contain lamellar intracytoplasmic membranes underlying, and parallel to, the cytoplasmic membrane. The photosynthetic pigments are bacteriochlorophyll a and carotenoids; the absorption spectrum of living cells shows maxima at 377, 463, 492, 527, 592, 806 and 867 nm. The cells grow photoheterotrophically under anaerobic or microaerobic conditions with various organic carbon sources or grow photolithoautotrophically with H(2) and CO(2). Strain RS(T) is a moderately acidophilic organism exhibiting growth at pH values between 4.8 and 7.0 (with an optimum at pH 5.2-5.5). The major fatty acids are 16 : 1omega7c and 18 : 1omega7c; the major quinones are Q-10 and Q-9. The DNA G + C content of strain RS(T) is 62.6 mol%. Analysis of the 16S rRNA gene sequence revealed that the novel isolate is most closely related (97.3 % sequence similarity) to the type strain ATCC 25092(T) of the moderately acidophilic purple non-sulfur bacterium Rhodoblastus acidophilus, formerly named Rhodopseudomonas acidophila. However, in contrast to Rbl. acidophilus, strain RS(T) is not capable of aerobic growth in the dark, has no spirilloxanthin among the carotenoids and differs in the pattern of substrate utilization. The value for DNA-DNA hybridization between strain RS(T) and Rbl. acidophilus ATCC 25092(T) is only 22 %. Thus, strain RS(T) represents a novel species of the genus Rhodoblastus, for which the name Rhodoblastus sphagnicola sp. nov. is proposed. Strain RS(T) (=DSM 16996(T) = VKM B-2361(T)) is the type strain.

Quantum transport in the FMO photosynthetic light-harvesting complex.

PubMed

Karafyllidis, Ioannis G

2017-06-01

The very high light-harvesting efficiency of natural photosynthetic systems in conjunction with recent experiments, which showed quantum-coherent energy transfer in photosynthetic complexes, raised questions regarding the presence of non-trivial quantum effects in photosynthesis. Grover quantum search, quantum walks, and entanglement have been investigated as possible effects that lead to this efficiency. Here we explain the near-unit photosynthetic efficiency without invoking non-trivial quantum effects. Instead, we use non-equilibrium Green's functions, a mesoscopic method used to study transport in nano-conductors to compute the transmission function of the Fenna-Matthews-Olson (FMO) complex using an experimentally derived exciton Hamiltonian. The chlorosome antenna and the reaction center play the role of input and output contacts, connected to the FMO complex. We show that there are two channels for which the transmission is almost unity. Our analysis also revealed a dephasing-driven regulation mechanism that maintains the efficiency in the presence of varying dephasing potentials.

Photovoltaic concepts inspired by coherence effects in photosynthetic systems

NASA Astrophysics Data System (ADS)

Brédas, Jean-Luc; Sargent, Edward H.; Scholes, Gregory D.

2017-01-01

The past decade has seen rapid advances in our understanding of how coherent and vibronic phenomena in biological photosynthetic systems aid in the efficient transport of energy from light-harvesting antennas to photosynthetic reaction centres. Such coherence effects suggest strategies to increase transport lengths even in the presence of structural disorder. Here we explore how these principles could be exploited in making improved solar cells. We investigate in depth the case of organic materials, systems in which energy and charge transport stand to be improved by overcoming challenges that arise from the effects of static and dynamic disorder -- structural and energetic -- and from inherently strong electron-vibration couplings. We discuss how solar-cell device architectures can evolve to use coherence-exploiting materials, and we speculate as to the prospects for a coherent energy conversion system. We conclude with a survey of the impacts of coherence and bioinspiration on diverse solar-energy harvesting solutions, including artificial photosynthetic systems.

Differential Allocation to Photosynthetic and Non-Photosynthetic Nitrogen Fractions among Native and Invasive Species

PubMed Central

Funk, Jennifer L.; Glenwinkel, Lori A.; Sack, Lawren

2013-01-01

Invasive species are expected to cluster on the “high-return” end of the leaf economic spectrum, displaying leaf traits consistent with higher carbon assimilation relative to native species. Intra-leaf nitrogen (N) allocation should support these physiological differences; however, N biochemistry has not been examined in more than a few invasive species. We measured 34 leaf traits including seven leaf N pools for five native and five invasive species from Hawaii under low irradiance to mimic the forest understory environment. We found several trait differences between native and invasive species. In particular, invasive species showed preferential N allocation to metabolism (amino acids) rather than photosynthetic light reactions (membrane-bound protein) by comparison with native species. The soluble protein concentration did not vary between groups. Under these low irradiance conditions, native species had higher light-saturated photosynthetic rates, possibly as a consequence of a greater investment in membrane-bound protein. Invasive species may succeed by employing a wide range of N allocation mechanisms, including higher amino acid production for fast growth under high irradiance or storage of N in leaves as soluble protein or amino acids. PMID:23700483

Capsule-Transmitted Gut Symbiotic Bacterium of the Japanese Common Plataspid Stinkbug, Megacopta punctatissima

PubMed Central

Fukatsu, Takema; Hosokawa, Takahiro

2002-01-01

The Japanese common plataspid stinkbug, Megacopta punctatissima, deposits small brown particles, or symbiont capsules, on the underside of the egg mass for the purpose of transmission of symbiotic bacteria to the offspring. We investigated the microbiological aspects of the bacteria contained in the capsule, such as microbial diversity, phylogenetic placement, localization in vivo, and fitness effects on the host insect. Restriction fragment length polymorphism analysis of 16S ribosomal DNA clones revealed that a single bacterial species dominates the microbiota in the capsule. The bacterium was not detected in the eggs but in the capsules, which unequivocally demonstrated that the bacterium is transmitted to the offspring of the insect orally rather than transovarially, through probing of the capsule content. Molecular phylogenetic analysis showed that the bacterium belongs to the γ-subdivision of the Proteobacteria. In adult insects the bacterium was localized in the posterior section of the midgut. Deprivation of the bacterium from the nymphs resulted in retarded development, arrested growth, abnormal body coloration, and other symptoms, suggesting that the bacterium is essential for normal development and growth of the host insect. PMID:11772649

Calculation of the radiative properties of photosynthetic microorganisms

NASA Astrophysics Data System (ADS)

Dauchet, Jérémi; Blanco, Stéphane; Cornet, Jean-François; Fournier, Richard

2015-08-01

A generic methodological chain for the predictive calculation of the light-scattering and absorption properties of photosynthetic microorganisms within the visible spectrum is presented here. This methodology has been developed in order to provide the radiative properties needed for the analysis of radiative transfer within photobioreactor processes, with a view to enable their optimization for large-scale sustainable production of chemicals for energy and chemistry. It gathers an electromagnetic model of light-particle interaction along with detailed and validated protocols for the determination of input parameters: morphological and structural characteristics of the studied microorganisms as well as their photosynthetic-pigment content. The microorganisms are described as homogeneous equivalent-particles whose shape and size distribution is characterized by image analysis. The imaginary part of their refractive index is obtained thanks to a new and quite extended database of the in vivo absorption spectra of photosynthetic pigments (that is made available to the reader). The real part of the refractive index is then calculated by using the singly subtractive Kramers-Krönig approximation, for which the anchor point is determined with the Bruggeman mixing rule, based on the volume fraction of the microorganism internal-structures and their refractive indices (extracted from a database). Afterwards, the radiative properties are estimated using the Schiff approximation for spheroidal or cylindrical particles, as a first step toward the description of the complexity and diversity of the shapes encountered within the microbial world. Finally, these predictive results are confronted to experimental normal-hemispherical transmittance spectra for validation. This entire procedure is implemented for Rhodospirillum rubrum, Arthrospira platensis and Chlamydomonas reinhardtii, each representative of the main three kinds of photosynthetic microorganisms, i.e. respectively

Swimming efficiency of bacterium Escherichia coli

PubMed Central

Chattopadhyay, Suddhashil; Moldovan, Radu; Yeung, Chuck; Wu, X. L.

2006-01-01

We use measurements of swimming bacteria in an optical trap to determine fundamental properties of bacterial propulsion. In particular, we directly measure the force required to hold the bacterium in the optical trap and determine the propulsion matrix, which relates the translational and angular velocity of the flagellum to the torques and forces propelling the bacterium. From the propulsion matrix, dynamical properties such as torques, swimming speed, and power can be obtained by measuring the angular velocity of the motor. We find significant heterogeneities among different individuals even though all bacteria started from a single colony. The propulsive efficiency, defined as the ratio of the propulsive power output to the rotary power input provided by the motors, is found to be ≈2%, which is consistent with the efficiency predicted theoretically for a rigid helical coil. PMID:16954194

Photosynthetic and ultrastructural responses of Ulva australis to Zn stress.

PubMed

Farias, D R; Schmidt, E; Simioni, C; Bouzon, Z L; Hurd, C L; Eriksen, R S; Macleod, C K

2017-12-01

This research evaluated the effect of zinc (Zn) on the ultrastructure and the photosynthetic efficiency of a common green alga. Ulva australis was grown in the laboratory for 7days under a range of different Zn concentrations (0, 25, 50 and 100μgL -1 ). Growth rate (Gr), photosynthetic efficiency (Fv/Fm and ETRmax), photosynthetic pigments, and metal accumulation were measured. Samples of 1mm length were taken to analyse the effect of Zn on the ultrastructure using transmission electron microscopy (TEM) and cytochemical responses (TB-O and PAS) were evaluated by light microscopy (LM). There were no significant differences in the growth rate, Fv/Fm, ETRmax and the photosynthetic pigments chlorophyll a, chlorophyll b and carotenoids (p>0.05) after 7days of Zn exposure. However, TEM revealed cytoplasm retraction, compression of cellulose fibrils, dissembled thylakoids and electron-dense bodies suggesting ultrastructural impacts from metal exposure and accumulation. Cytological analysis demonstrated that Zn affected U. australis cells at the three concentrations tested. The main effect was cytoplasm retraction and a decrease on the amount of starch granules, following exposure at 25μgL -1 and 50μgL -1 of Zn. We conclude that concentrations of Zn assessed in U. australis in this research has a short-term cellular effect as revealed by TEM and cytological analysis, demonstrating the importance of measuring a broad suite of endpoints to better understand species responses to environmentally relevant concentrations of Zn. However, U. australis was able to physiologically tolerate adverse conditions, since there was no effect on the photosynthetic performance and growth. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Correlation research of photosynthetic characteristics and medicinal materials production with 4 Uncariae Cum Uncis].

PubMed

Luo, Min; Song, Zhi-Qin; Yang, Ping-Fei; Liu, Hai; Yang, Zai-Gang; Wu, Ming-Kai

2017-01-01

Using four Uncariae Cum Uncis materials including Uncaria sinensis (HGT), U. hirsutea (MGT), Jianhe U. rhynchophylla (JHGT) and U. rhynchophylla(GT) as the research objects, the correlations between medicinal materials' yield and photosynthetic ecophysiology-factors in the plant exuberant growth period were studied. Results showed that the Uncaria plants net photosynthetic rate (Pn) changed by unimodal curve. There was not "midday depression" phenomenon. There was a different relationship among the photosynthetic ecophysiology-factors and between photosynthetic ecophysiology-factors and medicinal materials' yield. Pn,Tl,Gs had a significant correlation with medicinal materials' yield（M）and were the most important factors of growth. Copyright© by the Chinese Pharmaceutical Association.

Predicting Photosynthetic Fluxes from Spectral Reflectance of Leaves and Canopies

NASA Technical Reports Server (NTRS)

Gamon, John A.

1997-01-01

The central hypothesis of this study has been that photosynthetic efficiency and capacity can be predicted from 'physiological reflectance indices' derived from spectral reflectance of leaves and canopies. I have approached this topic with a combination of laboratory and field experiments, and have also explored the potential of deriving a meaningful physiological index from imaging spectrometry (e.g. AVIRIS). A few highlights are presented below. The main emphasis has been on the 'Photochemical Reflectance Index' (PRI), derived from reflectance at 531 nm and 570 nm. Unlike most 'conventional' vegetation indices (e.g. NDVI), PRI changes rapidly both with illumination and physiological state, because it detects the interconversion of xanthophyll cycle pigments, which serve as photoregulatory pigments and control energy distribution for the photosynthetic system. This approach has differed dramatically from most remote sensing in that it has emphasized temporal variation in narrow-band spectral signatures, instead of spatial patterns of broadband indices. Our primary conclusion has been that PRI works well as an index of photosynthetic light-use efficiency at the leaf scale, much in the same way as the fluorescence index DeltaF/Fm. However, unlike DeltaF/Fm which must be measured at close scales, PRI can be sampled at a range of spatial scales, presenting the possibility of monitoring photosynthetic fluxes remotely.

Coiled to diffuse: Brownian motion of a helical bacterium.

PubMed

Butenko, Alexander V; Mogilko, Emma; Amitai, Lee; Pokroy, Boaz; Sloutskin, Eli

2012-09-11

We employ real-time three-dimensional confocal microscopy to follow the Brownian motion of a fixed helically shaped Leptospira interrogans (LI) bacterium. We extract from our measurements the translational and the rotational diffusion coefficients of this bacterium. A simple theoretical model is suggested, perfectly reproducing the experimental diffusion coefficients, with no tunable parameters. An older theoretical model, where edge effects are neglected, dramatically underestimates the observed rates of translation. Interestingly, the coiling of LI increases its rotational diffusion coefficient by a factor of 5, compared to a (hypothetical) rectified bacterium of the same contour length. Moreover, the translational diffusion coefficients would have decreased by a factor of ~1.5, if LI were rectified. This suggests that the spiral shape of the spirochaete bacteria, in addition to being employed for their active twisting motion, may also increase the ability of these bacteria to explore the surrounding fluid by passive Brownian diffusion.

Synthesis of High-Molecular-Weight Polyhydroxyalkanoates by Marine Photosynthetic Purple Bacteria

PubMed Central

Higuchi-Takeuchi, Mieko; Morisaki, Kumiko; Toyooka, Kiminori; Numata, Keiji

2016-01-01

Polyhydroxyalkanoate (PHA) is a biopolyester/bioplastic that is produced by a variety of microorganisms to store carbon and increase reducing redox potential. Photosynthetic bacteria convert carbon dioxide into organic compounds using light energy and are known to accumulate PHA. We analyzed PHAs synthesized by 3 purple sulfur bacteria and 9 purple non-sulfur bacteria strains. These 12 purple bacteria were cultured in nitrogen-limited medium containing acetate and/or sodium bicarbonate as carbon sources. PHA production in the purple sulfur bacteria was induced by nitrogen-limited conditions. Purple non-sulfur bacteria accumulated PHA even under normal growth conditions, and PHA production in 3 strains was enhanced by nitrogen-limited conditions. Gel permeation chromatography analysis revealed that 5 photosynthetic purple bacteria synthesized high-molecular-weight PHAs, which are useful for industrial applications. Quantitative reverse transcription polymerase chain reaction analysis revealed that mRNA levels of phaC and PhaZ genes were low under nitrogen-limited conditions, resulting in production of high-molecular-weight PHAs. We conclude that all 12 tested strains are able to synthesize PHA to some degree, and we identify 5 photosynthetic purple bacteria that accumulate high-molecular-weight PHA molecules. Furthermore, the photosynthetic purple bacteria synthesized PHA when they were cultured in seawater supplemented with acetate. The photosynthetic purple bacteria strains characterized in this study should be useful as host microorganisms for large-scale PHA production utilizing abundant marine resources and carbon dioxide. PMID:27513570

[Partial biological characteristics and algicidal activity of an algicidal bacterium].

PubMed

Li, San-Hua; Zhang, Qi-Ya

2013-02-01

An algicidal bacterium was isolated from freshwater (Lake Donghu in Wuhan) and coded as A01. The morphology of the algicidal bacterium was observed using optical microscope and electron microscopes, the results showed that A01 was rod-shaped, approximately 1.5 microm in length and 0.45 microm in width and with no flagella structure. A01 was Gram-negative and belongs to the family Acinetobacter sp. though identification by Gram's staining and 16S rDNA gene analysis. A01 exhibited strong algicidal activity on the bloom-forming cyanobacterium Anabaena eucompacta under laboratory conditions. The removal rate of chlorophyll a after 7-day incubation with the culture supernatant of A01 and thalli were 77% and 61%, respectively. Microscopic observation showed that almost all cyanobacterial cells were destroyed within 3 d of co-incubation with the supernatant of algicidal bacterium, but a mass of the cyanobacterial cell lysis was observed only after 5 d of co-incubation with the thalli of algicidal bacterium. These results indicated that the main algicidal component of A01 was in its culture supernatant. In other words, the strain A01 could secrete algicidal component against Anabaena eucompacta.

Respiratory processes in non-photosynthetic plastids

PubMed Central

Renato, Marta; Boronat, Albert; Azcón-Bieto, Joaquín

2015-01-01

Chlororespiration is a respiratory process located in chloroplast thylakoids which consists in an electron transport chain from NAD(P)H to oxygen. This respiratory chain involves the NAD(P)H dehydrogenase complex, the plastoquinone pool and the plastid terminal oxidase (PTOX), and it probably acts as a safety valve to prevent the over-reduction of the photosynthetic machinery in stress conditions. The existence of a similar respiratory activity in non-photosynthetic plastids has been less studied. Recently, it has been reported that tomato fruit chromoplasts present an oxygen consumption activity linked to ATP synthesis. Etioplasts and amyloplasts contain several electron carriers and some subunits of the ATP synthase, so they could harbor a similar respiratory process. This review provides an update on the study about respiratory processes in chromoplasts, identifying the major gaps that need to be addressed in future research. It also reviews the proteomic data of etioplasts and amyloplasts, which suggest the presence of a respiratory electron transport chain in these plastids. PMID:26236317

Specific Interaction between Redox Phospholipid Polymers and Plastoquinone in Photosynthetic Electron Transport Chain.

PubMed

Tanaka, Kenya; Kaneko, Masahiro; Ishikawa, Masahito; Kato, Souichiro; Ito, Hidehiro; Kamachi, Toshiaki; Kamiya, Kazuhide; Nakanishi, Shuji

2017-04-19

Redox phospholipid polymers added in culture media are known to be capable of extracting electrons from living photosynthetic cells across bacterial cell membranes with high cytocompatibility. In the present study, we identify the intracellular redox species that transfers electrons to the polymers. The open-circuit electrochemical potential of an electrolyte containing the redox polymer and extracted thylakoid membranes shift to positive (or negative) under light irradiation, when an electron transport inhibitor specific to plastoquinone is added upstream (or downstream) in the photosynthetic electron transport chain. The same trend is also observed for a medium containing living photosynthetic cells of Synechococcus elongatus PCC7942. These results clearly indicate that the phospholipid redox polymers extract photosynthetic electrons mainly from plastoquinone. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Excitation energy transfer in photosynthetic protein-pigment complexes

NASA Astrophysics Data System (ADS)

Yeh, Shu-Hao

Quantum biology is a relatively new research area which investigates the rules that quantum mechanics plays in biology. One of the most intriguing systems in this field is the coherent excitation energy transport (EET) in photosynthesis. In this document I will discuss the theories that are suitable for describing the photosynthetic EET process and the corresponding numerical results on several photosynthetic protein-pigment complexes (PPCs). In some photosynthetic EET processes, because of the electronic coupling between the chromophores within the system is about the same order of magnitude as system-bath coupling (electron-phonon coupling), a non-perturbative method called hierarchy equation of motion (HEOM) is applied to study the EET dynamics. The first part of this thesis includes brief introduction and derivation to the HEOM approach. The second part of this thesis the HEOM method will be applied to investigate the EET process within the B850 ring of the light harvesting complex 2 (LH2) from purple bacteria, Rhodopseudomonas acidophila. The dynamics of the exciton population and coherence will be analyzed under different initial excitation configurations and temperatures. Finally, how HEOM can be implemented to simulate the two-dimensional electronic spectra of photosynthetic PPCs will be discussed. Two-dimensional electronic spectroscopy is a crucial experimental technique to probe EET dynamics in multi-chromophoric systems. The system we are interested in is the 7-chromophore Fenna-Matthews-Olson (FMO) complex from green sulfur bacteria, Prosthecochloris aestuarii. Recent crystallographic studies report the existence of an additional (eighth) chromophore in some of the FMO monomers. By applying HEOM we are able to calculate the two-dimensional electronic spectra of the 7-site and 8-site FMO complexes and investigate the functionality of the eighth chromophore.

The role of energy losses in photosynthetic light harvesting

NASA Astrophysics Data System (ADS)

Krüger, T. P. J.; van Grondelle, R.

2017-07-01

Photosynthesis operates at the bottom of the food chain to convert the energy of light into carbohydrates at a remarkable global rate of about 130 TW. Nonetheless, the overall photosynthetic process has a conversion efficiency of a few percent at best, significantly less than bottom-up photovoltaic cells. The primary photosynthetic steps, consisting of light harvesting and charge separation, are often presented as having near-unity quantum efficiency but this holds only true under ideal conditions. In this review, we discuss the importance of energy loss mechanisms to establish robustness in photosynthetic light harvesting. Thermal energy dissipation of light-harvesting complexes (LHCs) in different environments is investigated and the relationships and contrasts between concentration quenching of high pigment concentrations, photoprotection (non-photochemical quenching), quenching due to protein aggregation, and fluorescence blinking are discussed. The role of charge-transfer states in light harvesting and energy dissipation is highlighted and the importance of controlled protein structural disorder to switch the light-harvesting antennae between effective light harvesters and efficient energy quenchers is underscored. The main LHC of plants, LHCII, is used as a prime example.

[Photosynthetic physiological adaptabilities of Pinus tabulaeformis and Robinia pseudoacacia in the Loess Plateau].

PubMed

Zheng, Shu-xia; Shangguan, Zhou-ping

2007-01-01

With Yangling, Yongshou, Fuxian, Ansai, Mizhi and Shenmu, the s ix counties from the south to the north in the Loess Plateau as study sites, this paper studied thoe photosynthetic charac teristics and leaf traits of Pinus tabulaeformis and Robinia pseudoacacia. The results showed that among the six sites, there were significant differences in the photosynthetic rate (Pn), photosynthetic nitrogen use efficiency (PNUE), water use efficiency (WUE), leaf mass per area (LMA), nitrogen content (Nmass), and chlorophyll content (Chl) of P. tabulaeformis and R. pseudoacacia, suggesting that the photosynthetic capacity and leaf traits of the two species differed with sites. From the south to the north, the Pn, PNUE and WUE of P. tabulaeformis increased slightly while those of R. pseudoacacia decreased significantly, indicating that in drought habitat, P. tabulaef6rmis could still maintain high photosynthetic capacity, hut the photosynthetic capacity of R. pseudoacacia was greatly restrained. Also from the south to the north, the LMA of P. tabulaeformis and R. pseudoacacia had a slight increasing trend, while Nmass and Chl decreased slightly. The variation ranges of the three parameters were greater for R. pseudoacacia than for P. tabulaeformis, indicating that P. tabulaeformis had stronger drought-tolerant capability than R. pseudoacacia, which was not only exhibited in physiological metabolism, but also in leaf morphological acclimation. The correlation analysis between photosynthetic parameters and leaf traits of P. tabulaeformis and R. pseudoacacia in the six sites showed that there was a significant negative correlation between LMA and Nmass. The Pn and PNUE of both test species had no correlations with LMA and Nmass, but had significant positive correlation with Chl. The WUE of the species was negatively correlated with LMA, but positively correlated with Nmass.

Effects of pH and Oxygen on Photosynthetic Reactions of Intact Chloroplasts 1

PubMed Central

Heber, Ulrich; Andrews, T. John; Boardman, N. Keith

1976-01-01

Oxygen inhibition of photosynthesis was studied with intact spinach (Spinacia oleracea L.) chloroplasts which exhibited very high rates of photosynthetic CO2 reduction and were insensitive to additions of photosynthetic intermediates when CO2 was available at saturating concentrations. Photosynthetic rates were measured polarographically as O2 evolution, and the extent of the reduction of substrate was estimated from the amount of O2 evolved. With CO2 as substrate, inhibition of photosynthesis by O2 was dependent on pH. At pH values above 8, rates of O2 evolution were strongly inhibited by O2 and only a fraction of the added bicarbonate was reduced before O2 evolution ceased. The extent of O2 evolution declined with increasing O2 concentration and decreasing initial bicarbonate concentration. At pH 7.2, the initial photosynthetic rate was inhibited about 30% at high O2 levels, but the extent of O2 evolution was unaffected and most of the added bicarbonate was reduced. Photosynthetic O2 evolution with 3-phosphoglycerate as substrate was similarly dependent on pH and O2 concentration. In contrast, there was little effect of O2 and pH on oxaloacetate-dependent oxygen evolution. Acid-base shift experiments with osmotically shocked chloroplasts showed that ATP formation was not affected by O2. The results are discussed in terms of a balance between photosynthetic O2 evolution and O2 consumption by the ribulose diphosphate oxygenase reaction. PMID:16659466

Photosynthetic adaptation strategy of Ulva prolifera floating on the sea surface to environmental changes.

PubMed

Zhao, Xinyu; Tang, Xuexi; Zhang, Huanxin; Qu, Tongfei; Wang, Ying

2016-10-01

For 8 consecutive years, a green tide has originated in the southern Yellow Sea and spread to the Qingdao offshore area. The causative species, Ulva prolifera, always forms a very thick thallus mat that is capable of drifting long distances over long periods. During this process, although the thalli face disturbance by complex environmental factors, they maintain high biomass and proliferation. We hypothesized that some form of photosynthetic adaptation strategy must exist to protect the thalli. Therefore, we studied the different photosynthetic response characteristics of the surface and lower layers of the floating thallus mats, and investigated the physiological and molecular-level adaptation mechanisms. The results showed that: (1) U. prolifera has strong photosynthetic capability that ensures it can gain sufficient energy to increase its biomass and adapt to long-distance migration. (2) Surface layer thalli adapt to the complex environment by dissipating excess energy via photosynthetic quantum control (energy quenching and energy redistribution between PSII/PSI) to avoid irreversible damage to the photosynthetic system. (3) Lower layer thalli increase their contents of Chlorophyll a (Chl a) and Chlorophyll b (Chl b) and decrease their Chl a/Chl b ratio to improve their ability to use light energy. (4) U. prolifera has strong photosynthetic plasticity and can adapt to frequent exchange between the surface and lower layer environments because of wave disturbance. Pigment component changes, energy quenching, and energy redistribution between PSII/PSI contribute to this photosynthetic plasticity. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii.

PubMed

Allorent, Guillaume; Lefebvre-Legendre, Linnka; Chappuis, Richard; Kuntz, Marcel; Truong, Thuy B; Niyogi, Krishna K; Ulm, Roman; Goldschmidt-Clermont, Michel

2016-12-20

Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here, we report in the green alga Chlamydomonas reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast.

UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allorent, Guillaume; Lefebvre-Legendre, Linnka; Chappuis, Richard

Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here in this paper, we report in the green alga Chlamydomonasmore » reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast.« less

UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii

DOE PAGES

Allorent, Guillaume; Lefebvre-Legendre, Linnka; Chappuis, Richard; ...

2016-12-05

Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here in this paper, we report in the green alga Chlamydomonasmore » reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast.« less

UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii

PubMed Central

Allorent, Guillaume; Lefebvre-Legendre, Linnka; Chappuis, Richard; Kuntz, Marcel; Truong, Thuy B.; Niyogi, Krishna K.; Goldschmidt-Clermont, Michel

2016-01-01

Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here, we report in the green alga Chlamydomonas reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast. PMID:27930292

Light-Harvesting Antenna System from the Phototrophic Bacterium Roseiflexus castenholzii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, Aaron M.; Qian, Pu; Tang, Qun

Photosynthetic organisms have evolved diverse light-harvesting complexes to harness light of various qualities and intensities. Photosynthetic bacteria can have (bacterio)chlorophyll Q y antenna absorption bands ranging from ~650 to ~1100 nm. This broad range of wavelengths has allowed many organisms to thrive in unique light environments. Roseiflexus castenholzii is a niche-adapted, filamentous anoxygenic phototroph (FAP) that lacks chlorosomes, the dominant antenna found in most green bacteria, and here we describe the purification of a full complement of photosynthetic complexes: the light-harvesting (LH) antenna, reaction center (RC), and core complex (RC-LH). By high-performance liquid chromatography separation of bacteriochlorophyll and bacteriopheophytin pigmentsmore » extracted from the core complex and the RC, the number of subunits that comprise the antenna was determined to be 15 ± 1. Resonance Raman spectroscopy of the carbonyl stretching region displayed modes indicating that 3C-acetyl groups of BChl a are all involved in molecular interactions probably similar to those found in LH1 complexes from purple photosynthetic bacteria. Finally, two-dimensional projections of negatively stained core complexes and the LH antenna revealed a closed, slightly elliptical LH ring with an average diameter of 130 ± 10 Å surrounding a single RC that lacks an H-subunit but is associated with a tetraheme c-type cytochrome.« less

BOREAS TE-9 NSA Photosynthetic Response Data

NASA Technical Reports Server (NTRS)

Hall, Forrest G.; Curd, Shelaine (Editor); Dang, Qinglai; Margolis, Hank; Coyea, Marie

2000-01-01

The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-9 (Terrestrial Ecology) team collected several data sets related to chemical and photosynthetic properties of leaves. This data set describes: (1) the response of leaf and shoot-level photosynthesis to ambient and intercellular CO2 concentration, temperature, and incident photosynthetically active radiation (PAR) for black spruce, jack pine, and aspen during the three intensive field campaigns (IFCs) in 1994 in the Northern Study Area (NSA); (2) the response of stomatal conductance to vapor pressure difference throughout the growing season of 1994; and (3) a range of shoot water potentials (controlled in the laboratory) for black spruce and jack pine. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Older Thinopyrum intermedium (Poaceae) plants exhibit superior photosynthetic tolerance to cold stress and greater increases in two photosynthetic enzymes under freezing stress compared with young plants

PubMed Central

Jaikumar, Nikhil S.; Snapp, Sieglinde S.; Sharkey, Thomas D.

2016-01-01

Effects of plant age on resource acquisition and stress tolerance processes is a largely unstudied subject in herbaceous perennials. In a field experiment, we compared rates of photosynthesis (A), ribulose-1,5-bisphosphate (RuBP) carboxylation capacity (V Cmax), maximum electron transport rate (J max), and triose phosphate utilization (TPU), as well as concentrations of Rubisco and sucrose-phosphate synthase (SPS) in 5-year-old and 2-year-old intermediate wheatgrass (Thinopyrum intermedium) under both optimal growing conditions and cold stress in early spring and autumn. This species is a relative of wheat undergoing domestication. An additional experiment compared photosynthetic rates in different cohorts at mid-season and under colder conditions. We hypothesized that photosynthetic capacity in older plants would be lower under favorable conditions but higher under cold stress. Our hypothesis was generally supported. Under cold stress, 5-year-old plants exhibited higher A, TPU, and temperature-adjusted V Cmax than younger plants, as well as 50% more SPS and 37% more Rubisco. In contrast, at mid-season, photosynthetic capacities in older plants were lower than in younger plants in one experiment, and similar in the other, independent of differences in water status. Both cohorts increased A, temperature-adjusted TPU and J max, [Rubisco], and [SPS] under cold stress, but changes were greater in older plants. Photosynthetic differences were largest at 1.2 ºC in very early spring, where older plants had 200% higher A and maintained up to 17% of their peak photosynthetic capacity. We find evidence of increased cold tolerance in older cohorts of wheatgrass, consistent with a growing body of research in woody perennials. PMID:27401911

Mapping the spectral variability in photosynthetic and non-photosynthetic vegetation, soils, and shade using AVIRIS

NASA Technical Reports Server (NTRS)

Roberts, Dar A.; Smith, Milton O.; Sabol, Donald E.; Adams, John B.; Ustin, Susan L.

1992-01-01

The primary objective of this research was to map as many spectrally distinct types of green vegetation (GV), non-photosynthetic vegetation (NPV), shade, and soil (endmembers) in an Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) scene as is warranted by the spectral variability of the data. Once determined, a secondary objective was to interpret these endmembers and their abundances spatially and spectrally in an ecological context.

Gut bacterium of Dendrobaena veneta (Annelida: Oligochaeta) possesses antimycobacterial activity.

PubMed

Fiołka, Marta J; Zagaja, Mirosław P; Piersiak, Tomasz D; Wróbel, Marek; Pawelec, Jarosław

2010-09-01

The new bacterial strain with antimycobacterial activity has been isolated from the midgut of Dendrobaena veneta (Annelida). Biochemical and molecular characterization of isolates from 18 individuals identified all as Raoultella ornithinolytica genus with 99% similarity. The bacterium is a possible symbiont of the earthworm D. veneta. The isolated microorganism has shown the activity against four strains of fast-growing mycobacteria: Mycobacterium butiricum, Mycobacterium jucho, Mycobacterium smegmatis and Mycobacterium phlei. The multiplication of the gut bacterium on plates with Sauton medium containing mycobacteria has caused a lytic effect. After the incubation of the cell free extract prepared from the gut bacterium with four strains of mycobacteria in liquid Sauton medium, the cells of all tested strains were deformed and divided to small oval forms and sometimes created long filaments. The effect was observed by the use of light, transmission and scanning microscopy. Viability of all examined species of mycobacteria was significantly decreased. The antimycobacterial effect was probably the result of the antibiotic action produced by the gut bacterium of the earthworm. The application of ultrafiltration procedure allowed to demonstrate that antimicrobial substance with strong antimycobacterial activity from bacterial culture supernatant, is a protein with the molecular mass above 100 kDa. Copyright 2010 Elsevier Inc. All rights reserved.

Still acting green: continued expression of photosynthetic genes in the heterotrophic Dinoflagellate Pfiesteria piscicida (Peridiniales, Alveolata).

PubMed

Kim, Gwang Hoon; Jeong, Hae Jin; Yoo, Yeong Du; Kim, Sunju; Han, Ji Hee; Han, Jong Won; Zuccarello, Giuseppe C

2013-01-01

The loss of photosynthetic function should lead to the cessation of expression and finally loss of photosynthetic genes in the new heterotroph. Dinoflagellates are known to have lost their photosynthetic ability several times. Dinoflagellates have also acquired photosynthesis from other organisms, either on a long-term basis or as "kleptoplastids" multiple times. The fate of photosynthetic gene expression in heterotrophs can be informative into evolution of gene expression patterns after functional loss, and the dinoflagellates ability to acquire new photosynthetic function through additional endosymbiosis. To explore this we analyzed a large-scale EST database consisting of 151,091 unique sequences (29,170 contigs, 120,921 singletons) obtained from 454 pyrosequencing of the heterotrophic dinoflagellate Pfiesteria piscicida. About 597 contigs from P. piscicida showed significant homology (E-value photosynthetic function. Most of the genes involved in the Calvin-Benson cycle were found, genes of the light-dependent reaction were also identified. Also genes of associated pathways including the chorismate pathway and genes involved in starch metabolism were discovered. BLAST searches and phylogenetic analysis suggest that these plastid-associated genes originated from several different photosynthetic ancestors. The Calvin-Benson cycle genes are mostly associated with genes derived from the secondary plastids of peridinin-containing dinoflagellates, while the light-harvesting genes are derived from diatoms, or diatoms that are tertiary plastids in other dinoflagellates. The continued expression of many genes involved in photosynthetic pathways indicates that the loss of transcriptional regulation may occur well after plastid loss and could explain the organism's ability to "capture" new plastids (i.e. different secondary endosymbiosis or tertiary symbioses) to renew photosynthetic function.

Discussion of Yellow Starthistle Response to Photosynthetic Irradiance, Photoperiod, and CO2

NASA Technical Reports Server (NTRS)

Bubenheim, David

2017-01-01

Yellow Starthistle (Centaurea solstitialis) is a native annual weed of Eurasia and since introduction into the United STates has become an invasive and noxious weed. It grows in a rosette habit during the vegetative state and usually bolts in summer to produce a large and branched flowering stem. Time to flowering in Yellow Starthistle has been attributed to photoperiod, nitrogen nutrition, temperature, and water stress. We executed a series of studies to investigate the role of light, both photoperiod and photosynthetic photon flux, on flowering and development in Yellow Starthistle. Treatments were presented in 4 ways: 1) varying day length with constant photosynthetic photon flus (PPF) providing increasing daily integrated Photosynthetic Photon (PP) exposure with longer day lengths 2) varying day length while adjusting PPF to maintain daily PP exposure for all treatments 3) extending photoperiod treatments beyond common 12-h photosynthetic period with low light levels to maintain both PPF and daily PP across all treatments4)reciprocal exchange of plant among photoperiod treatments Yellow Starthistle appears to be a long-day plant with a critical day length requirement between 14-h and 16-h to induce transition from vegetative to floral stages in development. PPF and daily absorbed photons did not affect time to vegetative floral stage transition, but did affect factors such as biomass accumulation and canopy parameters such as specific leaf mass. Reciprocal exchange of plants between floral inducing and inhibiting photoperiod treatments, starting at 2-weeks post germination, had no effect on to flower. Flowering was determined by photoperiod experienced during the first 2-weeks (or less) post germination.Yellow Starthistle net photosynthetic response to elevated atmospheric CO2 concentrations over a range of photosynthetically active radiation flux rates and temperatures will also be presented and discussed.

Faster photosynthetic induction in tobacco by expressing cyanobacterial flavodiiron proteins in chloroplasts.

PubMed

Gómez, Rodrigo; Carrillo, Néstor; Morelli, María P; Tula, Suresh; Shahinnia, Fahimeh; Hajirezaei, Mohammad-Reza; Lodeyro, Anabella F

2018-05-01

Plants grown in the field experience sharp changes in irradiation due to shading effects caused by clouds, other leaves, etc. The excess of absorbed light energy is dissipated by a number of mechanisms including cyclic electron transport, photorespiration, and Mehler-type reactions. This protection is essential for survival but decreases photosynthetic efficiency. All phototrophs except angiosperms harbor flavodiiron proteins (Flvs) which relieve the excess of excitation energy on the photosynthetic electron transport chain by reducing oxygen directly to water. Introduction of cyanobacterial Flv1/Flv3 in tobacco chloroplasts resulted in transgenic plants that showed similar photosynthetic performance under steady-state illumination, but displayed faster recovery of various photosynthetic parameters, including electron transport and non-photochemical quenching during dark-light transitions. They also kept the electron transport chain in a more oxidized state and enhanced the proton motive force of dark-adapted leaves. The results indicate that, by acting as electron sinks during light transitions, Flvs contribute to increase photosynthesis protection and efficiency under changing environmental conditions as those found by plants in the field.

Detecting in-field variation in photosynthetic capacity of trangenically modifed plants with hyperspectral imaging.

NASA Astrophysics Data System (ADS)

Meacham, K.; Montes, C.; Pederson, T.; Wu, J.; Guan, K.; Bernacchi, C.

2017-12-01

Improved photosynthetic rates have been shown to increase crop biomass, making improved photosynthesis a focus for driving future grain yield increases. Improving the photosynthetic pathway offers opportunity to meet food demand, but requires high throughput measurement techniques to detect photosynthetic variation in natural accessions and transgenically modified plants. Gas exchange measurements are the most widely used method of measuring photosynthesis in field trials but this process is laborious and slow, and requires further modeling to estimate meaningful parameters and to upscale to the plot or canopy level. In field trials of tobacco with modifications made to the photosynthetic pathway, we infer the maximum carboxylation rate of Rubisco (Vcmax) and maximum electron transport rate (Jmax) and detect photosynthetic variation from hyperspectral imaging with a partial least squares regression technique. Ground-truth measurements from photosynthetic gas exchange, a full-range (400-2500nm) handheld spectroadiometer with leaf clip, hyperspectral indices, and extractions of leaf pigments support the model. The results from a range of wild-type cultivars and from genetically modified germplasm suggest that the opportunity for rapid selection of top performing genotypes from among thousands of plots. This research creates the opportunity to extend agroecosystem models from simplified "one-cultivar" generic parameterization to better represent a full suite of current and future crop cultivars for a wider range of environmental conditions.

Assessing the effects of ultraviolet radiation on the photosynthetic potential in Archean marine environments

NASA Astrophysics Data System (ADS)

Avila-Alonso, Dailé; Baetens, Jan M.; Cardenas, Rolando; de Baets, Bernard

2017-07-01

In this work, the photosynthesis model presented by Avila et al. in 2013 is extended and more scenarios inhabited by ancient cyanobacteria are investigated to quantify the effects of ultraviolet (UV) radiation on their photosynthetic potential in marine environments of the Archean eon. We consider ferrous ions as blockers of UV during the Early Archean, while the absorption spectrum of chlorophyll a is used to quantify the fraction of photosynthetically active radiation absorbed by photosynthetic organisms. UV could have induced photoinhibition at the water surface, thereby strongly affecting the species with low light use efficiency. A higher photosynthetic potential in early marine environments was shown than in the Late Archean as a consequence of the attenuation of UVC and UVB by iron ions, which probably played an important role in the protection of ancient free-floating bacteria from high-intensity UV radiation. Photosynthetic organisms in Archean coastal and ocean environments were probably abundant in the first 5 and 25 m of the water column, respectively. However, species with a relatively high efficiency in the use of light could have inhabited ocean waters up to a depth of 200 m and show a Deep Chlorophyll Maximum near 60 m depth. We show that the electromagnetic radiation from the Sun, both UV and visible light, could have determined the vertical distribution of Archean marine photosynthetic organisms.

Characterization of the promising poly(3-hydroxybutyrate) producing halophilic bacterium Halomonas halophila.

PubMed

Kucera, Dan; Pernicová, Iva; Kovalcik, Adriana; Koller, Martin; Mullerova, Lucie; Sedlacek, Petr; Mravec, Filip; Nebesarova, Jana; Kalina, Michal; Marova, Ivana; Krzyzanek, Vladislav; Obruca, Stanislav

2018-05-01

This work explores molecular, morphological as well as biotechnological features of the highly promising polyhydroxyalkanoates (PHA) producer Halomonas halophila. Unlike many other halophiles, this bacterium does not require expensive complex media components and it is capable to accumulate high intracellular poly(3-hydroxybutyrate) (PHB) fractions up to 82% of cell dry mass. Most remarkably, regulating the concentration of NaCl apart from PHB yields influences also the polymer's molecular mass and polydispersity. The bacterium metabolizes various carbohydrates including sugars predominant in lignocelluloses and other inexpensive substrates. Therefore, the bacterium was employed for PHB production on hydrolysates of cheese whey, spent coffee grounds, sawdust and corn stover, which were hydrolyzed by HCl; required salinity of cultivation media was set up during neutralization by NaOH. The bacterium was capable to use all the tested hydrolysates as well as sugar beet molasses for PHB biosynthesis, indicating its potential for industrial PHB production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Photosynthetic Energy Transfer at the Quantum/Classical Border.

PubMed

Keren, Nir; Paltiel, Yossi

2018-06-01

Quantum mechanics diverges from the classical description of our world when very small scales or very fast processes are involved. Unlike classical mechanics, quantum effects cannot be easily related to our everyday experience and are often counterintuitive to us. Nevertheless, the dimensions and time scales of the photosynthetic energy transfer processes puts them close to the quantum/classical border, bringing them into the range of measurable quantum effects. Here we review recent advances in the field and suggest that photosynthetic processes can take advantage of the sensitivity of quantum effects to the environmental 'noise' as means of tuning exciton energy transfer efficiency. If true, this design principle could be a base for 'nontrivial' coherent wave property nano-devices. Copyright © 2018 Elsevier Ltd. All rights reserved.

Micromachined microbial and photosynthetic fuel cells

NASA Astrophysics Data System (ADS)

Chiao, Mu; Lam, Kien B.; Lin, Liwei

2006-12-01

This paper presents two types of fuel cells: a miniature microbial fuel cell (µMFC) and a miniature photosynthetic electrochemical cell (µPEC). A bulk micromachining process is used to fabricate the fuel cells, and the prototype has an active proton exchange membrane area of 1 cm2. Two different micro-organisms are used as biocatalysts in the anode: (1) Saccharomyces cerevisiae (baker's yeast) is used to catalyze glucose and (2) Phylum Cyanophyta (blue-green algae) is used to produce electrons by a photosynthetic reaction under light. In the dark, the µPEC continues to generate power using the glucose produced under light. In the cathode, potassium ferricyanide is used to accept electrons and electric power is produced by the overall redox reactions. The bio-electrical responses of µMFCs and µPECs are characterized with the open-circuit potential measured at an average value of 300-500 mV. Under a 10 ohm load, the power density is measured as 2.3 nW cm-2 and 0.04 nW cm-2 for µMFCs and µPECs, respectively.

[Study on anti-bacterium activity of ginkgolic acids and their momomers].

PubMed

Yang, Xiaoming; Zhu, Wei; Chen, Jun; Qian, Zhiyu; Xie, Jimin

2004-09-01

Ginkgolic acids and their three monomers were separated from ginkgo sarcotestas. The anti-bacterium activity of ginkgolic acids were tested. The relation between the anti-bacterium activity and side chain of ginkgolic acid were studied. The MIC of ginkgolic acids and their three monomers and salicylic acid were tested. Ginkgolic acid has strong inhibitive effect on G+-bacterium. Salicylic acid has no side chain, so no anti-bacterial activity. When the length of gingkolic acid side chain is C13:0, it has the strongest anti-bacterial activity in three monomers. The side chain of ginkgolic acid is the key functional group that possessed anti-bacterial activity. The length of Ginkgolic acid was the main effective factor of anti-bacterial activity.

Photosynthetic Physiological Response of Radix Isatidis (Isatis indigotica Fort.) Seedlings to Nicosulfuron

PubMed Central

Ning, Na; Wen, Yinyuan; Dong, Shuqi; Yin, Meiqiang; Guo, Meijun; Wang, Binqiang; Feng, Lei; Guo, Pingyi

2014-01-01

Radix Isatidis (Isatis indigotica Fort.) is one of the most important traditional Chinese medicine plants. However, there is no suitable herbicide used for weed control in Radix Isatidis field during postemergence stage. To explore the safety of sulfonylurea herbicide nicosulfuron on Radix Isatidis (Isatis indigotica Fort.) seedlings and the photosynthetic physiological response of the plant to the herbicide, biological mass, leaf area, photosynthetic pigment content, photosynthetic rate, chlorophyll fluorescence characteristics, and P700 parameters of Radix Isatidis seedlings were analyzed 10 d after nicosulfuron treatment at 5th leaf stage in this greenhouse research. The results showed that biological mass, total chlorophyll, chlorophyll a, and carotenoids content, photosynthetic rate, stomatal conductance, PS II maximum quantum yield, PS II effective quantum yield, PS II electron transport rate, photochemical quenching, maximal P700 change, photochemical quantum yield of PS I, and PS I electron transport rate decreased with increasing herbicide concentrations, whereas initial fluorescence, quantum yield of non-regulated energy dissipation in PS II and quantum yield of non-photochemical energy dissipation due to acceptor side limitation in PS I increased. It suggests that nicosulfuron ≥1 mg L−1 causes the damage of chloroplast, PS II and PS I structure. Electron transport limitations in PS I receptor side, and blocked dark reaction process may be the main cause of the significantly inhibited growth and decreased photosynthetic rate of Radix Isatidis seedlings. PMID:25165819

Properties and structure of a low-potential, penta-heme cytochrome c 552 from a thermophilic purple sulfur photosynthetic bacterium Thermochromatium tepidum.

PubMed

Chen, Jing-Hua; Yu, Long-Jiang; Boussac, Alain; Wang-Otomo, Zheng-Yu; Kuang, Tingyun; Shen, Jian-Ren

2018-04-24

The thermophilic purple sulfur bacterium Thermochromatium tepidum possesses four main water-soluble redox proteins involved in the electron transfer behavior. Crystal structures have been reported for three of them: a high potential iron-sulfur protein, cytochrome c', and one of two low-potential cytochrome c 552 (which is a flavocytochrome c) have been determined. In this study, we purified another low-potential cytochrome c 552 (LPC), determined its N-terminal amino acid sequence and the whole gene sequence, characterized it with absorption and electron paramagnetic spectroscopy, and solved its high-resolution crystal structure. This novel cytochrome was found to contain five c-type hemes. The overall fold of LPC consists of two distinct domains, one is the five heme-containing domain and the other one is an Ig-like domain. This provides a representative example for the structures of multiheme cytochromes containing an odd number of hemes, although the structures of multiheme cytochromes with an even number of hemes are frequently seen in the PDB database. Comparison of the sequence and structure of LPC with other proteins in the databases revealed several characteristic features which may be important for its functioning. Based on the results obtained, we discuss the possible intracellular function of this LPC in Tch. tepidum.

Older Thinopyrum intermedium (Poaceae) plants exhibit superior photosynthetic tolerance to cold stress and greater increases in two photosynthetic enzymes under freezing stress compared with young plants.

PubMed

Jaikumar, Nikhil S; Snapp, Sieglinde S; Sharkey, Thomas D

2016-08-01

Effects of plant age on resource acquisition and stress tolerance processes is a largely unstudied subject in herbaceous perennials. In a field experiment, we compared rates of photosynthesis (A), ribulose-1,5-bisphosphate (RuBP) carboxylation capacity (V Cmax), maximum electron transport rate (J max), and triose phosphate utilization (TPU), as well as concentrations of Rubisco and sucrose-phosphate synthase (SPS) in 5-year-old and 2-year-old intermediate wheatgrass (Thinopyrum intermedium) under both optimal growing conditions and cold stress in early spring and autumn. This species is a relative of wheat undergoing domestication. An additional experiment compared photosynthetic rates in different cohorts at mid-season and under colder conditions. We hypothesized that photosynthetic capacity in older plants would be lower under favorable conditions but higher under cold stress. Our hypothesis was generally supported. Under cold stress, 5-year-old plants exhibited higher A, TPU, and temperature-adjusted V Cmax than younger plants, as well as 50% more SPS and 37% more Rubisco. In contrast, at mid-season, photosynthetic capacities in older plants were lower than in younger plants in one experiment, and similar in the other, independent of differences in water status. Both cohorts increased A, temperature-adjusted TPU and J max, [Rubisco], and [SPS] under cold stress, but changes were greater in older plants. Photosynthetic differences were largest at 1.2 ºC in very early spring, where older plants had 200% higher A and maintained up to 17% of their peak photosynthetic capacity. We find evidence of increased cold tolerance in older cohorts of wheatgrass, consistent with a growing body of research in woody perennials. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Hydraulic constraints modify optimal photosynthetic profiles in giant sequoia trees.

PubMed

Ambrose, Anthony R; Baxter, Wendy L; Wong, Christopher S; Burgess, Stephen S O; Williams, Cameron B; Næsborg, Rikke R; Koch, George W; Dawson, Todd E

2016-11-01

Optimality theory states that whole-tree carbon gain is maximized when leaf N and photosynthetic capacity profiles are distributed along vertical light gradients such that the marginal gain of nitrogen investment is identical among leaves. However, observed photosynthetic N gradients in trees do not follow this prediction, and the causes for this apparent discrepancy remain uncertain. Our objective was to evaluate how hydraulic limitations potentially modify crown-level optimization in Sequoiadendron giganteum (giant sequoia) trees up to 90 m tall. Leaf water potential (Ψ l ) and branch sap flow closely followed diurnal patterns of solar radiation throughout each tree crown. Minimum leaf water potential correlated negatively with height above ground, while leaf mass per area (LMA), shoot mass per area (SMA), leaf nitrogen content (%N), and bulk leaf stable carbon isotope ratios (δ(13)C) correlated positively with height. We found no significant vertical trends in maximum leaf photosynthesis (A), stomatal conductance (g s), and intrinsic water-use efficiency (A/g s), nor in branch-averaged transpiration (E L), stomatal conductance (G S), and hydraulic conductance (K L). Adjustments in hydraulic architecture appear to partially compensate for increasing hydraulic limitations with height in giant sequoia, allowing them to sustain global maximum summer water use rates exceeding 2000 kg day(-1). However, we found that leaf N and photosynthetic capacity do not follow the vertical light gradient, supporting the hypothesis that increasing limitations on water transport capacity with height modify photosynthetic optimization in tall trees.

Improving Models of Photosynthetic Thermal Acclimation: Which Parameters are Most Important and How Many Should Be Modified?

NASA Astrophysics Data System (ADS)

Stinziano, J. R.; Way, D.; Bauerle, W.

2017-12-01

Photosynthetic temperature acclimation could strongly affect coupled vegetation-atmosphere feedbacks in the global carbon cycle, especially as the climate warms. Thermal acclimation of photosynthesis can be modelled as changes in the parameters describing the direct effect of temperature on photosynthetic capacity (activation energy, Ea; deactivation energy, Hd; entropy parameter, ΔS) or the basal value of photosynthetic capacity (i.e. photosynthetic capacity measured at 25 °C), however the impact of acclimating these parameters (individually or in combination) on vegetative carbon gain is relatively unexplored. Here we compare the ability of 66 photosynthetic temperature acclimation scenarios to improve predictions of a spatially explicit canopy carbon flux model, MAESTRA, for eddy covariance data from a loblolly pine forest. We show that: 1) incorporating seasonal temperature acclimation of basal photosynthetic capacity improves the model's ability to capture seasonal changes in carbon fluxes; 2) multifactor scenarios of photosynthetic temperature acclimation provide minimal (if any) improvement in model performance over single factor acclimation scenarios; 3) acclimation of enzyme activation energies should be restricted to the temperature ranges of the data from which the equations are derived; and 4) model performance is strongly affected by the choice of deactivation energy. We suggest that a renewed effort be made into understanding the thermal acclimation of enzyme activation and deactivation energies across broad temperature ranges to better understand the mechanisms underlying thermal photosynthetic acclimation.

Engineering of cyanobacteria for the photosynthetic production of limonene from CO2.

PubMed

Kiyota, Hiroshi; Okuda, Yukiko; Ito, Michiho; Hirai, Masami Yokota; Ikeuchi, Masahiko

2014-09-20

Isoprenoids, major secondary metabolites in many organisms, are utilized in various applications. We constructed a model photosynthetic production system for limonene, a volatile isoprenoid, using a unicellular cyanobacterium that expresses the plant limonene synthase. This system produces limonene photosynthetically at a nearly constant rate and that can be efficiently recovered using a gas-stripping method. This production does not affect the growth of the cyanobacteria and is markedly enhanced by overexpression of three enzymes in the intrinsic pathway to provide the precursor of limonene, geranyl pyrophosphate. The photosynthetic production of limonene in our system is more or less sustained from the linear to stationary phase of cyanobacterial growth for up to 1 month. Copyright © 2014 Elsevier B.V. All rights reserved.

A Simple Method to Estimate Photosynthetic Radiation Use Efficiency of Canopies

PubMed Central

ROSATI, A.; METCALF, S. G.; LAMPINEN, B. D.

2004-01-01

• Background and Aims Photosynthetic radiation use efficiency (PhRUE) over the course of a day has been shown to be constant for leaves throughout a general canopy where nitrogen content (and thus photosynthetic properties) of leaves is distributed in relation to the light gradient. It has been suggested that this daily PhRUE can be calculated simply from the photosynthetic properties of a leaf at the top of the canopy and from the PAR incident on the canopy, which can be obtained from weather‐station data. The objective of this study was to investigate whether this simple method allows estimation of PhRUE of different crops and with different daily incident PAR, and also during the growing season. • Methods The PhRUE calculated with this simple method was compared with that calculated with a more detailed model, for different days in May, June and July in California, on almond (Prunus dulcis) and walnut (Juglans regia) trees. Daily net photosynthesis of 50 individual leaves was calculated as the daylight integral of the instantaneous photosynthesis. The latter was estimated for each leaf from its photosynthetic response to PAR and from the PAR incident on the leaf during the day. • Key Results Daily photosynthesis of individual leaves of both species was linearly related to the daily PAR incident on the leaves (which implies constant PhRUE throughout the canopy), but the slope (i.e. the PhRUE) differed between the species, over the growing season due to changes in photosynthetic properties of the leaves, and with differences in daily incident PAR. When PhRUE was estimated from the photosynthetic light response curve of a leaf at the top of the canopy and from the incident radiation above the canopy, obtained from weather‐station data, the values were within 5 % of those calculated with the more detailed model, except in five out of 34 cases. • Conclusions The simple method of estimating PhRUE is valuable as it simplifies calculation of canopy

Photosynthetic activity during olive (Olea europaea) leaf development correlates with plastid biogenesis and Rubisco levels.

PubMed

Maayan, Inbar; Shaya, Felix; Ratner, Kira; Mani, Yair; Lavee, Shimon; Avidan, Benjamin; Shahak, Yosepha; Ostersetzer-Biran, Oren

2008-11-01

Olive leaves are known to mature slowly, reaching their maximum photosynthetic activity only after full leaf expansion. Poor assimilation rates, typical to young olive leaves, were previously associated with low stomata conductance. Yet, very little is known about chloroplast biogenesis throughout olive leaf development. Here, the photosynthetic activity and plastids development throughout leaf maturation is characterized by biochemical and ultrastructural analyses. Although demonstrated only low photosynthetic activity, the plastids found in young leaves accumulated both photosynthetic pigments and proteins required for photophosphorylation and carbon fixation. However, Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase), which catalyzes the first major step of carbon fixation and one of the most abundant proteins in plants, could not be detected in the young leaves and only slowly accumulated throughout development. In fact, Rubisco levels seemed tightly correlated with the observed photosynthetic activities. Unlike Rubisco, numerous proteins accumulated in the young olive leaves. These included the early light induced proteins, which may be required to reduce the risk of photodamage, because of light absorption by photosynthetic pigments. Also, high levels of ribosomal L11 subunit, transcription factor elF-5A, Histones H2B and H4 were observed in the apical leaves, and in particular a plastidic-like aldolase, which accounted for approximately 30% of the total proteins. These proteins may upregulate in their levels to accommodate the high demand for metabolic energy in the young developing plant tissue, further demonstrating the complex sink-to-source relationship between young and photosynthetically active mature leaves.

Role of various hormones in photosynthetic responses of green plants under environmental stresses.

PubMed

Poonam; Bhardwaj, Renu; Kaur, Ravdeep; Bali, Shagun; Kaur, Parminder; Sirhindi, Geetika; Thukral, Ashwani K; Ohri, Puja; Vig, Adarsh P

2015-01-01

Environmental stress includes adverse factors like water deficit, high salinity, enhanced temperature and heavy metals etc. These stresses alter the normal growth and metabolic processes of plants including photosynthesis. Major photosynthetic responses under various stresses include inhibition of photosystems (I and II), changes in thylakoid complexes, decreased photosynthetic activity and modifications in structure and functions of chloroplasts etc. Various defense mechanisms are triggered inside the plants in response to these stresses that are regulated by plant hormones or plant growth regulators. These phytohormones include abscisic acid, auxins, cytokinins, ethylene, brassinosteroids, jasmonates and salicylic acid etc. The present review focuses on stress protective effects of plants hormones on the photosynthetic responses.

[Molecular responses of photosynthetic apparatus of plants to long term irradiance changes].

PubMed

Adamiec, Małgorzata; Jackowski, Grzegorz

2008-01-01

In response to long term (at least 1-3 h) irradiance changes the responses are elicited at the level of structure and function of photosynthetic apparatus of plants which are thought to be aimed to keep the balance between the level of excitation energy funneled to the reaction centers of the photosystems by energetic antennae and the utilization of this energy in the form of photosynthetic electron transfer and dark reactions. At high vs medium irradiances the rate of excitation energy transfer via LHCII is reduced while the rate of electron flow and photosynthetic dark reactions is increased. The reaction at LHCII level stems from the reduction of its pool per PSII reaction center and the regulatory events comprise changes in the expression of LHCII apoproteins and/or chi b biosynthesis. The basis for higher electron flow capabilities lies in significant increases in the content of some electron carriers and the catalytic activity of ATP synthase. The upregulation of photosynthetic dark reaction in turn is due to the activation of signaling pathways leading to the increase in the pool and catalytic activities of rubisco and other Calvin cycle enzymes.

A remotely sensed pigment index reveals photosynthetic phenology in evergreen conifers.

PubMed

Gamon, John A; Huemmrich, K Fred; Wong, Christopher Y S; Ensminger, Ingo; Garrity, Steven; Hollinger, David Y; Noormets, Asko; Peñuelas, Josep

2016-11-15

In evergreen conifers, where the foliage amount changes little with season, accurate detection of the underlying "photosynthetic phenology" from satellite remote sensing has been difficult, presenting challenges for global models of ecosystem carbon uptake. Here, we report a close correspondence between seasonally changing foliar pigment levels, expressed as chlorophyll/carotenoid ratios, and evergreen photosynthetic activity, leading to a "chlorophyll/carotenoid index" (CCI) that tracks evergreen photosynthesis at multiple spatial scales. When calculated from NASA's Moderate Resolution Imaging Spectroradiometer satellite sensor, the CCI closely follows the seasonal patterns of daily gross primary productivity of evergreen conifer stands measured by eddy covariance. This discovery provides a way of monitoring evergreen photosynthetic activity from optical remote sensing, and indicates an important regulatory role for carotenoid pigments in evergreen photosynthesis. Improved methods of monitoring photosynthesis from space can improve our understanding of the global carbon budget in a warming world of changing vegetation phenology.

Rhodobacter sphaeroides spd mutations allow cytochrome c2-independent photosynthetic growth.

PubMed Central

Rott, M A; Donohue, T J

1990-01-01

In Rhodobacter sphaeroides, cytochrome c2 (cyt c2) is a periplasmic redox protein required for photosynthetic electron transfer. cyt c2-deficient mutants created by replacing the gene encoding the apoprotein for cyt c2 (cycA) with a kanamycin resistance cartridge are photosynthetically incompetent. Spontaneous mutations that suppress this photosynthesis deficiency (spd mutants) arise at a frequency of 1 to 10 in 10(7). We analyzed the cytochrome content of several spd mutants spectroscopically and by heme peroxidase assays. These suppressors lacked detectable cyt c2, but they contained a new soluble cytochrome which was designated isocytochrome c2 (isocyt c2) that was not detectable in either cycA+ or cycA mutant cells. When spd mutants were grown photosynthetically, isocyt c2 was present at approximately 20 to 40% of the level of cyt c2 found in photosynthetically grown wild type cells, and it was found in the periplasm with cytochromes c' and c554. These spd mutants also had several other pleiotropic phenotypes. Although photosynthetic growth rates of the spd mutants were comparable to those of wild-type strains at all light intensities tested, they contained elevated levels of B800-850 pigment-protein complexes. Several spd mutants contained detectable amounts of isocyt c2 under aerobic conditions. Finally, heme peroxidase assays indicated that, under anaerobic conditions, the spd mutants may contain another new cytochrome in addition to isocyt c2. These pleiotropic phenotypes, the frequency at which the spd mutants arise, and the fact that a frameshift mutagen is very effective in generating the spd phenotype suggest that some spd mutants contain a mutation in loci which regulate cytochrome synthesis. Images FIG. 1 FIG. 2 FIG. 3 FIG. 4 PMID:2156806

Photosynthetic Rates of Citronella and Lemongrass 1

PubMed Central

Herath, H. M. Walter; Ormrod, Douglas P.

1979-01-01

Ten selections of citronella (Cymbopogon nardus [L.] Rendle) were grown at 32/27, 27/21, or 15/10 C day/night temperatures, and plants from three populations of lemongrass (Cymbopogon citratus [D.C.] Stapf from Japan or Sri Lanka and Cymbopogon flexuosus [D.C.] Stapf from India) were grown at 8- or 15-hour photoperiods. Net photosynthetic rates of mature leaves were measured in a controlled environment at 25 C and 260 microeinsteins per meter2 per second. Rates declined with increasing leaf age, and from the tip to the base of the leaf blade. Rates for citronella leaves grown at 15/10 C were extremely low for all selections. Highest rates of net photosynthesis were recorded for four selections grown at 27/21 C and for two selections grown at 32/27 C. Lemongrass grown at 8-hour photoperiod had higher photosynthetic rates than that grown at 15-hour photoperiod. PMID:16660737

Iron-mediated changes in phytoplankton photosynthetic competence during SOIREE

NASA Astrophysics Data System (ADS)

Boyd, P. W.; Abraham, E. R.

Active fluorescence (fast repetition rate fluorometry, FRRF) was used to follow the photosynthetic response of the phytoplankton community during the 13-day Southern Ocean Iron RElease Experiment (SOIREE). This in situ iron enrichment was conducted in the polar waters of the Australasian-Pacific sector of the Southern Ocean in February 1999. Iron fertilisation of these high nitrate low chlorophyll (HNLC) waters resulted in an increase in the photosynthetic competence ( Fv/ Fm) of the resident cells from around 0.20 to greater than 0.60 (i.e. close to the theoretical maximum) by 10/11 days after the first enrichment. Although a significant iron-mediated response in Fv/ Fm was detected as early as 24 h after the initial fertilisation, the increase in Fv/ Fm to double ambient levels took 6 days. This response was five-fold slower than observed in iron enrichments (in situ and in vitro) in the HNLC waters of the subarctic and equatorial Pacific. Although little is known about the relationship between water temperature and Fv/ Fm, it is likely that low water temperatures — and possibly the deep mixed layer — were responsible for this slow response time. During SOIREE, the photosynthetic competence of the resident phytoplankton in iron-enriched waters increased at dissolved iron levels above 0.2 nM, suggesting that iron limitation was alleviated at this concentration. Increases in Fv/ Fm of cells within four algal size classes suggested that all taxa displayed a photosynthetic response to iron enrichment. Other physiological proxies of algal iron stress (such as flavodoxin levels in diatoms) exhibited different temporal trends to iron-enrichment than Fv/ Fm during the time-course of SOIREE. The relationship between Fv/ Fm, algal growth rate and such proxies in Southern Ocean waters is discussed.

Photosynthetic light capture and processing from cell to canopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stenberg, P.; DeLucia, E.H.; Schoettle, A.W.

1995-07-01

We have addressed the unique structural features of conifers, as they relate to photosynthetic production, at different levels of organization (from needle to canopy). Many concepts and measures must be defined for conifers so that they are consistent with the structural properties of needles and shoots. Consistency is needed in comparing the photosynthetic performance of conifers and broad leaves, wherein it is important to distinguish the effect of structural factors on light capture from differences in the photosynthetic response at a fixed interception. Needles differ from broad leaves both with respect to inner structure and external shape, which includes amore » continuum from nearly flat to cylindrical. For nonflat three-dimensional objects such as for conifer needles, total surface area is the natural measure. The meaning of the one-sided area of needles is not clear, but consistency requires that it be defined as half the total needle surface area, as concluded. Characteristic structural factors of conifers that affect their ability to harvest light are a deep canopy combined with a small needle size, which create an important penumbra effect, and the clustering of needles on shoots, which creates a discontinuous distribution of needle area. These factors imply that, at a fixed leaf area index, the intercepted PAR would be smaller in coniferous than in broad-leafed canopies, but the vertical gradient of light in conifers is less steep and light reaching the lower canopy is all penumbral (diffuse). Conifers can maintain a higher leaf area index, and this may be accomplished by a more even distribution of light between shoots at different locations in the canopy and also because shade shoots have a structure that effectively intercepts light. Broad leaves in general have higher maximum photosynthetic rates than do needles, and yet conifers are at least equally productive on a stand basis. Possible reasons are discussed.« less

Stoichiometry and kinetics of mercury uptake by photosynthetic bacteria.

PubMed

Kis, Mariann; Sipka, Gábor; Maróti, Péter

2017-05-01

Mercury adsorption on the cell surface and intracellular uptake by bacteria represent the key first step in the production and accumulation of highly toxic mercury in living organisms. In this work, the biophysical characteristics of mercury bioaccumulation are studied in intact cells of photosynthetic bacteria by use of analytical (dithizone) assay and physiological photosynthetic markers (pigment content, fluorescence induction, and membrane potential) to determine the amount of mercury ions bound to the cell surface and taken up by the cell. It is shown that the Hg(II) uptake mechanism (1) has two kinetically distinguishable components, (2) includes co-opted influx through heavy metal transporters since the slow component is inhibited by Ca 2+ channel blockers, (3) shows complex pH dependence demonstrating the competition of ligand binding of Hg(II) ions with H + ions (low pH) and high tendency of complex formation of Hg(II) with hydroxyl ions (high pH), and (4) is not a passive but an energy-dependent process as evidenced by light activation and inhibition by protonophore. Photosynthetic bacteria can accumulate Hg(II) in amounts much (about 10 5 ) greater than their own masses by well-defined strong and weak binding sites with equilibrium binding constants in the range of 1 (μM) -1 and 1 (mM) -1 , respectively. The strong binding sites are attributed to sulfhydryl groups as the uptake is blocked by use of sulfhydryl modifying agents and their number is much (two orders of magnitude) smaller than the number of weak binding sites. Biofilms developed by some bacteria (e.g., Rvx. gelatinosus) increase the mercury binding capacity further by a factor of about five. Photosynthetic bacteria in the light act as a sponge of Hg(II) and can be potentially used for biomonitoring and bioremediation of mercury-contaminated aqueous cultures.

Endohyphal Bacterium Enhances Production of Indole-3-Acetic Acid by a Foliar Fungal Endophyte

PubMed Central

Hoffman, Michele T.; Gunatilaka, Malkanthi K.; Wijeratne, Kithsiri; Gunatilaka, Leslie; Arnold, A. Elizabeth

2013-01-01

Numerous plant pathogens, rhizosphere symbionts, and endophytic bacteria and yeasts produce the important phytohormone indole-3-acetic acid (IAA), often with profound effects on host plants. However, to date IAA production has not been documented among foliar endophytes -- the diverse guild of primarily filamentous Ascomycota that live within healthy, above-ground tissues of all plant species studied thus far. Recently bacteria that live within hyphae of endophytes (endohyphal bacteria) have been detected, but their effects have not been studied previously. Here we show not only that IAA is produced in vitro by a foliar endophyte (here identified as Pestalotiopsis aff. neglecta, Xylariales), but that IAA production is enhanced significantly when the endophyte hosts an endohyphal bacterium (here identified as Luteibacter sp., Xanthomonadales). Both the endophyte and the endophyte/bacterium complex appear to rely on an L-tryptophan dependent pathway for IAA synthesis. The bacterium can be isolated from the fungus when the symbiotic complex is cultivated at 36°C. In pure culture the bacterium does not produce IAA. Culture filtrate from the endophyte-bacterium complex significantly enhances growth of tomato in vitro relative to controls and to filtrate from the endophyte alone. Together these results speak to a facultative symbiosis between an endophyte and endohyphal bacterium that strongly influences IAA production, providing a new framework in which to explore endophyte-plant interactions. PMID:24086270

Photosynthetic pathway types of evergreen rosette plants (Liliaceae) of the Chihuahuan desert.

PubMed

Kemp, Paul R; Gardetto, Pietra E

1982-11-01

Diurnal patterns of CO 2 exchange and titratable acidity were monitored in six species of evergreen rosette plants growing in controlled environment chambers and under outdoor environmental conditions. These patterns indicated that two of the species, Yucca baccata and Y. torreyi, were constituitive CAM plants while the other species, Y. elata, Y. campestris, Nolina microcarpa and Dasylirion wheeleri, were C 3 plants. The C 3 species did not exhibit CAM when grown in any of several different temperature, photoperiod, and moisture regimes. Both photosynthetic pathway types appear adapted to desert environments and all species show environmentally induced changes in their photosynthetic responses consistent with desert adaptation. The results of this study do not indicate that changes in the photosynthetic pathway type are an adaptation in any of these species.

Photosynthetic capacity of red spruce during winter

Treesearch

P.G. Schaberg; J.B. Shane; P.F. Cali; J.R. Donnelly; G.R. Strimbeck

1998-01-01

We measured the photosynthetic capacity (Pmax) of plantation-grown red spruce (Picea rubens Sarg.) during two winter seasons (1993-94 and 1994-95) and monitored field photosynthesis of these trees during one winter (1993-94). We also measured Pmax for mature montane trees from January through May 1995....

Functional Inactivation of Putative Photosynthetic Electron Acceptor Ferredoxin C2 (FdC2) Induces Delayed Heading Date and Decreased Photosynthetic Rate in Rice

PubMed Central

Ruan, Banpu; Kang, Shujing; He, Lei; Zhang, Sen; Dong, Guojun; Hu, Jiang; Zeng, Dali; Zhang, Guangheng; Gao, Zhenyu; Ren, Deyong; Hu, Xingming; Chen, Guang; Guo, Longbiao; Qian, Qian; Zhu, Li

2015-01-01

Ferredoxin (Fd) protein as unique electron acceptor, involved in a variety of fundamental metabolic and signaling processes, which is indispensable for plant growth. The molecular mechanisms of Fd such as regulation of electron partitioning, impact of photosynthetic rate and involvement in the carbon fixing remain elusive in rice. Here we reported a heading date delay and yellowish leaf 1 (hdy1) mutant derived from Japonica rice cultivar “Nipponbare” subjected to EMS treatment. In the paddy field, the hdy1 mutant appeared at a significantly late heading date and had yellow-green leaves during the whole growth stage. Further investigation indicated that the abnormal phenotype of hdy1 was connected with depressed pigment content and photosynthetic rate. Genetic analysis results showed that the hdy1 mutant phenotype was caused by a single recessive nuclear gene mutation. Map-based cloning revealed that OsHDY1 is located on chromosome 3 and encodes an ortholog of the AtFdC2 gene. Complementation and overexpression, transgenic plants exhibited the mutant phenotype including head date, leaf color and the transcription levels of the FdC2 were completely rescued by transformation with OsHDY1. Real-time PCR revealed that the expression product of OsHDY1 was detected in almost all of the organs except root, whereas highest expression levels were observed in seeding new leaves. The lower expression levels of HDY1 and content of iron were detected in hdy1 than WT’s. The FdC2::GFP was detected in the chloroplasts of rice. Real-time PCR results showed that the expression of many photosynthetic electron transfer related genes in hdy1 were higher than WT. Our results suggest that OsFdC2 plays an important role in photosynthetic rate and development of heading date by regulating electron transfer and chlorophyll content in rice. PMID:26598971

Photoperiodic controls on ecosystem-level photosynthetic capacity

NASA Astrophysics Data System (ADS)

Stoy, P. C.; Trowbridge, A. M.; Bauerle, W.

2012-12-01

Most models of photosynthesis at the leaf or canopy level assume that temperature is the dominant control on the variability of photosynthetic parameters. Recent studies, however, have found that photoperiod is a better descriptor of the seasonal variability of photosynthetic function at the leaf and plant scale, and that spectral indices of leaf functionality are poor descriptors of this seasonality. We explored the variability of photosynthesic parameters at the ecosystem scale using over 100 site-years of air temperature and gross primary productivity (GPP) data from non-tropical forested sites in the Free/Fair Use LaThuille FLUXNET database (www.fluxdata.org), excluding sites that were classified as dry and/or with savanna vegetation, where we expected GPP to be driven by moisture availability. Both GPP and GPP normalized by daily photosynthetic photon flux density (GPPn) were considered, and photoperiod was calculated from eddy covariance tower coordinates. We performed a Granger causality analysis, a method based on the understanding that causes precede effects, on both the GPP and GPPn. Photoperiod Granger-caused GPP (GPPn) in 95% (87%) of all site-years. While temperature Granger-caused GPP in a mere 23% of site years, it Granger-caused GPPn 73% of the time. Both temperature values are significantly less than the percent of cases in which day length Granger-caused GPP (p<0.05, Student's t-test). An inverse analysis was performed for completeness, and it was found that GPP Granger-caused photoperiod (temperature) in 39% (78%) of all site years. Results demonstrate that incorporating simple photoperiod controls may be a logical step in improving ecosystem and global model output.

DAILY BUDGETS OF PHOTOSYNTHETICALLY FIXED CARBON IN SYMBIOTIC ZOANTHIDS.

PubMed

Steen, R Grant; Muscatine, L

1984-10-01

We tested the hypothesis that some zoanthids are able to meet a portion of their daily respiratory carbon requirement with photosynthetic carbon from symbiotic algal cells (= zooxanthellae). A daily budget was constructed for carbon (C) photosynthetically fixed by zooxanthellae of the Bermuda zoanthids Zoanthus sociatus and Palythoa variabilis. Zooxanthellae have an average net photosynthetic C fixation of 7.48 and 15.56 µgC·polyp -1 ·day -1 for Z. sociatus and P. variabilis respectively. The C-specific growth rate (µ c ) was 0.215·day -1 for Z. sociatus and 0.152·day -1 for P. variabilis. The specific growth rate (µ) of zooxanthellae in the zoanthids was measured to be 0.011 and 0.017·day -1 for Z. sociatus and P. variabilis zooxanthellae respectively. Z. sociatus zooxanthellae translocated 95.1% of the C assimilated in photosynthesis, while P. variabilis zooxanthellae translocated 88.8% of their fixed C. As the animal tissue of a polyp of Z. sociatus required 14.75 µgC·day -1 for respiration, and one of P. variabiis required 105.54 µgC·day -1 , the contribution of zooxanthellae to animal respiration (CZAR) was 48.2% for Z. sociatus and 13.1% for P. variabilis.

Auxenochlorella protothecoides and Prototheca wickerhamii plastid genome sequences give insight into the origins of non-photosynthetic algae

PubMed Central

Yan, Dong; Wang, Yun; Murakami, Tatsuya; Shen, Yue; Gong, Jianhui; Jiang, Huifeng; Smith, David R.; Pombert, Jean-Francois; Dai, Junbiao; Wu, Qingyu

2015-01-01

The forfeiting of photosynthetic capabilities has occurred independently many times throughout eukaryotic evolution. But almost all non-photosynthetic plants and algae still retain a colorless plastid and an associated genome, which performs fundamental processes apart from photosynthesis. Unfortunately, little is known about the forces leading to photosynthetic loss; this is largely because there is a lack of data from transitional species. Here, we compare the plastid genomes of two “transitional” green algae: the photosynthetic, mixotrophic Auxenochlorella protothecoides and the non-photosynthetic, obligate heterotroph Prototheca wickerhamii. Remarkably, the plastid genome of A. protothecoides is only slightly larger than that of P. wickerhamii, making it among the smallest plastid genomes yet observed from photosynthetic green algae. Even more surprising, both algae have almost identical plastid genomic architectures and gene compositions (with the exception of genes involved in photosynthesis), implying that they are closely related. This close relationship was further supported by phylogenetic and substitution rate analyses, which suggest that the lineages giving rise to A. protothecoides and P. wickerhamii diverged from one another around six million years ago. PMID:26403826

Auxenochlorella protothecoides and Prototheca wickerhamii plastid genome sequences give insight into the origins of non-photosynthetic algae.

PubMed

Yan, Dong; Wang, Yun; Murakami, Tatsuya; Shen, Yue; Gong, Jianhui; Jiang, Huifeng; Smith, David R; Pombert, Jean-Francois; Dai, Junbiao; Wu, Qingyu

2015-09-25

The forfeiting of photosynthetic capabilities has occurred independently many times throughout eukaryotic evolution. But almost all non-photosynthetic plants and algae still retain a colorless plastid and an associated genome, which performs fundamental processes apart from photosynthesis. Unfortunately, little is known about the forces leading to photosynthetic loss; this is largely because there is a lack of data from transitional species. Here, we compare the plastid genomes of two "transitional" green algae: the photosynthetic, mixotrophic Auxenochlorella protothecoides and the non-photosynthetic, obligate heterotroph Prototheca wickerhamii. Remarkably, the plastid genome of A. protothecoides is only slightly larger than that of P. wickerhamii, making it among the smallest plastid genomes yet observed from photosynthetic green algae. Even more surprising, both algae have almost identical plastid genomic architectures and gene compositions (with the exception of genes involved in photosynthesis), implying that they are closely related. This close relationship was further supported by phylogenetic and substitution rate analyses, which suggest that the lineages giving rise to A. protothecoides and P. wickerhamii diverged from one another around six million years ago.

Carbon, Hydrogen, and Oxygen Isotope Ratios of Cellulose from Plants Having Intermediary Photosynthetic Modes 1

PubMed Central

Sternberg, Leonel O'Reilly; Deniro, Michael J.; Ting, Irwin P.

1984-01-01

Carbon and hydrogen isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from species of greenhouse plants having different photosynthetic modes were determined. When hydrogen isotope ratios are plotted against carbon isotope ratios, four clusters of points are discernible, each representing different photosynthetic modes: C3 plants, C4 plants, CAM plants, and C3 plants that can shift to CAM or show the phenomenon referred to as CAM-cycling. The combination of oxygen and carbon isotope ratios does not distinguish among the different photosynthetic modes. Analysis of the carbon and hydrogen isotope ratios of cellulose nitrate should prove useful for screening different photosynthetic modes in field specimens that grew near one another. This method will be particularly useful for detection of plants which show CAM-cycling. PMID:16663360

A remotely sensed pigment index reveals photosynthetic phenology in evergreen conifers

PubMed Central

Huemmrich, K. Fred; Ensminger, Ingo; Garrity, Steven; Noormets, Asko; Peñuelas, Josep

2016-01-01

In evergreen conifers, where the foliage amount changes little with season, accurate detection of the underlying “photosynthetic phenology” from satellite remote sensing has been difficult, presenting challenges for global models of ecosystem carbon uptake. Here, we report a close correspondence between seasonally changing foliar pigment levels, expressed as chlorophyll/carotenoid ratios, and evergreen photosynthetic activity, leading to a “chlorophyll/carotenoid index” (CCI) that tracks evergreen photosynthesis at multiple spatial scales. When calculated from NASA’s Moderate Resolution Imaging Spectroradiometer satellite sensor, the CCI closely follows the seasonal patterns of daily gross primary productivity of evergreen conifer stands measured by eddy covariance. This discovery provides a way of monitoring evergreen photosynthetic activity from optical remote sensing, and indicates an important regulatory role for carotenoid pigments in evergreen photosynthesis. Improved methods of monitoring photosynthesis from space can improve our understanding of the global carbon budget in a warming world of changing vegetation phenology. PMID:27803333

Microfluidic high-throughput selection of microalgal strains with superior photosynthetic productivity using competitive phototaxis

PubMed Central

Kim, Jaoon Young Hwan; Kwak, Ho Seok; Sung, Young Joon; Choi, Hong Il; Hong, Min Eui; Lim, Hyun Seok; Lee, Jae-Hyeok; Lee, Sang Yup; Sim, Sang Jun

2016-01-01

Microalgae possess great potential as a source of sustainable energy, but the intrinsic inefficiency of photosynthesis is a major challenge to realize this potential. Photosynthetic organisms evolved phototaxis to find optimal light condition for photosynthesis. Here we report a microfluidic screening using competitive phototaxis of the model alga, Chlamydomonas reinhardtii, for rapid isolation of strains with improved photosynthetic efficiencies. We demonstrated strong relationship between phototaxis and photosynthetic efficiency by quantitative analysis of phototactic response at the single-cell level using a microfluidic system. Based on this positive relationship, we enriched the strains with improved photosynthetic efficiency by isolating cells showing fast phototactic responses from a mixture of 10,000 mutants, thereby greatly improving selection efficiency over 8 fold. Among 147 strains isolated after screening, 94.6% showed improved photoautotrophic growth over the parental strain. Two mutants showed much improved performances with up to 1.9- and 8.1-fold increases in photoautotrophic cell growth and lipid production, respectively, a substantial improvement over previous approaches. We identified candidate genes that might be responsible for fast phototactic response and improved photosynthesis, which can be useful target for further strain engineering. Our approach provides a powerful screening tool for rapid improvement of microalgal strains to enhance photosynthetic productivity. PMID:26852806

Genetic engineering of the Calvin cycle toward enhanced photosynthetic CO2 fixation in microalgae.

PubMed

Yang, Bo; Liu, Jin; Ma, Xiaonian; Guo, Bingbing; Liu, Bin; Wu, Tao; Jiang, Yue; Chen, Feng

2017-01-01

Photosynthetic microalgae are emerging as potential biomass feedstock for sustainable production of biofuels and value-added bioproducts. CO 2 biomitigation through these organisms is considered as an eco-friendly and promising alternative to the existing carbon sequestration methods. Nonetheless, the inherent relatively low photosynthetic capacity of microalgae has hampered the practical use of this strategy for CO 2 biomitigation applications. Here, we demonstrate the feasibility of improving photosynthetic capacity by the genetic manipulation of the Calvin cycle in the typical green microalga Chlorella vulgaris . Firstly, we fused a plastid transit peptide to upstream of the enhanced green fluorescent protein (EGFP) and confirmed its expression in the chloroplast of C. vulgaris . Then we introduced the cyanobacterial fructose 1,6-bisphosphate aldolase, guided by the plastid transit peptide, into C. vulgaris chloroplast, leading to enhanced photosynthetic capacity (~ 1.2-fold) and cell growth. Molecular and physiochemical analyses suggested a possible role for aldolase overexpression in promoting the regeneration of ribulose 1,5-bisphosphate in the Calvin cycle and energy transfer in photosystems. Our work represents a proof-of-concept effort to enhance photosynthetic capacity by the engineering of the Calvin cycle in green microalgae. Our work also provides insights into targeted genetic engineering toward algal trait improvement for CO 2 biomitigation uses.

Direct measurement of interaction forces between a single bacterium and a flat plate.

PubMed

Klein, Jonah D; Clapp, Aaron R; Dickinson, Richard B

2003-05-15

A technique for precisely measuring the equilibrium and viscous interaction forces between a single bacterium and a flat surface as functions of separation distance is described. A single-beam gradient optical trap was used to micromanipulate the bacterium against a flat surface while evanescent wave light scattering was used to measure separation distances. Calibrating the optical trap far from the surface allowed the trapped bacterium to be used as a force probe. Equilibrium force-distance profiles were determined by measuring the deflection of the cell from the center of the optical trap at various trap positions. Simultaneously, viscous forces were determined by measuring the relaxation time for the fluctuating bacterium. Absolute distances were determined using a best-fit approximation to the theoretical prediction for the hindered mobility of a diffusing sphere near a wall. Using this approach, forces in the range from 0.01 to 4 pN were measured at near-nanometer resolution between Staphylococcus aureus and glass that was bare or coated with adsorbed protein.

Complete genome sequence of "Thiodictyon syntrophicum" sp. nov. strain Cad16T, a photolithoautotrophic purple sulfur bacterium isolated from the alpine meromictic Lake Cadagno.

PubMed

Luedin, Samuel M; Pothier, Joël F; Danza, Francesco; Storelli, Nicola; Frigaard, Niels-Ulrik; Wittwer, Matthias; Tonolla, Mauro

2018-01-01

" Thiodictyon syntrophicum" sp. nov. strain Cad16 T is a photoautotrophic purple sulfur bacterium belonging to the family of Chromatiaceae in the class of Gammaproteobacteria . The type strain Cad16 T was isolated from the chemocline of the alpine meromictic Lake Cadagno in Switzerland. Strain Cad16 T represents a key species within this sulfur-driven bacterial ecosystem with respect to carbon fixation. The 7.74-Mbp genome of strain Cad16 T has been sequenced and annotated. It encodes 6237 predicted protein sequences and 59 RNA sequences. Phylogenetic comparison based on 16S rRNA revealed that Thiodictyon elegans strain DSM 232 T the most closely related species. Genes involved in sulfur oxidation, central carbon metabolism and transmembrane transport were found. Noteworthy, clusters of genes encoding the photosynthetic machinery and pigment biosynthesis are found on the 0.48 Mb plasmid pTs485. We provide a detailed insight into the Cad16 T genome and analyze it in the context of the microbial ecosystem of Lake Cadagno.

Study the effect of insecticide dimethoate on photosynthetic pigments and photosynthetic activity of pigeon pea: Laser-induced chlorophyll fluorescence spectroscopy.

PubMed

Pandey, Jitendra Kumar; Dubey, Gunjan; Gopal, R

2015-10-01

Pigeon pea is one of the most important legume crops in India and dimethoate is a widely used insecticide in various crop plants. We studied the effect of dimethoate on growth and photosynthetic activity of pigeon pea plants over a short and long term exposure. Plant growth parameters, photosynthetic pigment content and chlorophyll fluorescence response of pigeon pea (Cajanus cajan L.) plants treated with various concentrations of the insecticide dimethoate (10, 20, 40 and 80 ppm) have been compared for 30 days at regular intervals of 10 days each. Laser induced chlorophyll fluorescence spectra and fluorescence-induction kinetics (FIK) curve of dimethoate treated pigeon pea plants were recorded after 10, 20 and 30 days of treatment. Fluorescence intensity ratio at the two fluorescence maxima (F685/F730) was calculated by evaluating curve-fitted parameters. The variable chlorophyll fluorescence decrease ratio (Rfd) was determined from the FIK curves. Our study revealed that after 10 days of treatment, 10 ppm of dimethoate showed stimulatory response whereas 20, 40 and 80 ppm of dimethoate showed inhibitory response for growth and photosynthetic activity of pigeon pea plants, but after 20 and 30 days of treatment all the tested concentrations of dimethoate became inhibitory. This study clearly shows that dimethoate is highly toxic to the pigeon pea plant, even at very low concentration (10 ppm), if used for a prolonged duration. Our study may thus be helpful in determining the optimal dose of dimethoate in agricultural practices. Copyright © 2014 Elsevier B.V. All rights reserved.

Identification of Residual Structure in the Unfolded State of Ribonuclease H1 from the Moderately Thermophilic Chlorobium tepidum: Comparison with Thermophilic and Mesophilic Homologues†

PubMed Central

Ratcliff, Kathleen; Marqusee, Susan

2010-01-01

Ribonucleases H from organisms that grow at different temperatures demonstrate a variable change in heat capacity upon unfolding (ΔC°P) [Ratcliff, K., et al. (2009) Biochemistry 48, 5890–5898]. This ΔC°P has been shown to correlate with a tolerance to higher temperatures and residual structure in the unfolded state of the thermophilic proteins. In the RNase H from Thermus thermophilus, the low ΔC°P has been shown to arise from the same region as the folding core of the protein, and mutagenic studies have shown that loss of a hydrophobic residue in this region can disrupt this residual unfolded state structure and result in a return to a more mesophile-like ΔC°P [Robic, S., et al. (2002) Protein Sci. 11, 381–389; Robic, S., et al. (2003) Proc. Natl. Acad. Sci. U.S.A. 100, 11345–11349]. To understand further how residual structure in the unfolded state is encoded in the sequences of these thermophilic proteins, we subjected the RNase H from Chlorobium tepidum to similar studies. Analysis of new chimeric proteins reveals that like T. thermophilus RNase H, the folding core of C. tepidum RNaseH plays an important role in the unfolded state of this protein. Mutagenesis studies, based on both a computational investigation of the hydrophobic networks in the core region and comparisons with similar studies on T. thermophilus RNase H, identify new residues involved in this residual structure and suggest that the residual structure in the unfolded state of C. tepidum RNase H is more restricted than that of T. thermophilus. We conclude that while the folding core region determines the thermophilic-like behavior of this family of proteins, the residue-specific details vary. PMID:20491485

Toward understanding as photosynthetic biosignatures: light harvesting and energy transfer calculation

NASA Astrophysics Data System (ADS)

Komatsu, Y.; Umemura, M.; Shoji, M.; Shiraishi, K.; Kayanuma, M.; Yabana, K.

2014-03-01

Among several proposed biosignatures, red edge is a direct evidence of photosynthetic life if it is detected (Kiang et al 2007). Red edge is a sharp change in reflectance spectra of vegetation in NIR region (about 700-750 nm). The sign of red edge is observed by Earthshine or remote sensing (Wolstencroft & Raven 2002, Woolf et al 2002). But, why around 700-750 nm? The photosynthetic organisms on Earth have evolved to optimize the sunlight condition. However, if we consider about photosynthetic organism on extrasolar planets, they should have developed to utilize the spectra of its principal star. Thus, it is not strange even if it shows different vegetation spectra. In this study, we focused on the light absorption mechanism of photosynthetic organisms on Earth and investigated the fundamental properties of the light harvesting mechanisms, which is the first stage for the light absorption. Light harvesting complexes contain photosynthetic pigments like chlorophylls. Effective light absorption and the energy transfer are accomplished by the electronic excitations of collective photosynthetic pigments. In order to investigate this mechanism, we constructed an energy transfer model by using a dipole-dipole approximation for the interactions between electronic excitations. Transition moments and transition energies of each pigment are calculated at the time-dependent density functional theory (TDDFT) level (Marques & Gross 2004). Quantum dynamics simulation for the excitation energy transfer was calculated by the Liouvelle's equation. We adopted the model to purple bacteria, which has been studied experimentally and known to absorb lower energy. It is meaningful to focus on the mechanism of this bacteria, since in the future mission, M planets will become a important target. We calculated the oscillator strengths in one light harvesting complex and confirmed the validity by comparing to the experimental data. This complex is made of an inner and an outer ring. The

Reproduction reduces photosynthetic capacity in females of the subdioecious Honckenya peploides

NASA Astrophysics Data System (ADS)

Sánchez-Vilas, Julia; Retuerto, Rubén

2011-03-01

As a consequence of the different reproductive functions performed by the sexes, sexually dimorphic/polymorphic plants may exhibit gender-related variations in the energy and resources allocated to reproduction, and in the physiological processes that underlie these differences. This study investigated whether the sexes of the subdioecious plant Honckenya peploides differ in ecophysiological traits related to photosynthetic capacity and whether possible differences depend on reproductive status and on the plant's position (edge or centre) in the population. We registered in three sites in NW Spain, the sex and density of shoots of two segregated clumps of plants. These clumps represent an extreme case of sex-ratio variation across space, with separated single-sex clumps of plants. In two of these sites we measured photosynthetic efficiencies, chlorophyll content, and specific leaf areas. In females, reproduction reduced photochemical efficiency, chlorophyll content and increased the specific leaf area, which is a key leaf trait related to photosynthetic capacity. In males, no differences due to reproduction were detected. The position within the clump affected the specific leaf area of the shoots, with shoots growing at the edge having the lowest values, regardless of the sex. Finally, the effects of position in photosynthetic efficiency and chlorophyll content where highly variable among clumps. We conclude that the differential effects of reproduction on sexes may entail different costs that could be crucial in the outcome of interactions between them, contributing to their spatial segregation.

Automated systems to monitor space radiation effect on photosynthetic organisms

NASA Astrophysics Data System (ADS)

Esposito, D.; di Costa, F.; Faraloni, C.; Fasolo, F.; Pace, E.; Perosino, M.; Torzillo, G.; Touloupakis, E.; Zanini, A.; Giardi, M. T.

We developed automated biodevices to obtain, automatically, measures about the space radiation effect on living photosynthetic organisms, which can be used as biomass and oxygen-producing system on shuttles or ISS. Vitality measurements were performed by optical devices (fluorimeters) measuring fluorescence emission. Fluorescence methodology is a well known applied technique for studying photosynthetic activity, and in particular the oxygen-evolving process of photosynthetic organisms. Different strains of unicellular green algae are properly immobilized on agar growth medium and kept under survial light. The biodevices are characterised by the sensibility and selectivity of the biological component response, together with easy use, versatility, miniature size and low cost. We performed experiments in some facilities, in order to understand separately the effect of radiation of different LET, on the biochemical activity (gamma rays at Joint Research Centre -Varese, Italy; fast neutrons at CERF -- SPS beam at CERN -Geneva, Switzerland). The exposure to different radiation beams of the automatic devices, allowed us to test them under stress condition. In one year, these instrument are expected to be sent to space, inside a spacecraft, in order to study the effect of ionising cosmic radiation during an ESA flight.

Construction of hybrid photosynthetic units using peripheral and core antennae from two different species of photosynthetic bacteria: detection of the energy transfer from bacteriochlorophyll a in LH2 to bacteriochlorophyll b in LH1.

PubMed

Fujii, Ritsuko; Shimonaka, Shozo; Uchida, Naoko; Gardiner, Alastair T; Cogdell, Richard J; Sugisaki, Mitsuru; Hashimoto, Hideki

2008-01-01

Typical purple bacterial photosynthetic units consist of supra-molecular arrays of peripheral (LH2) and core (LH1-RC) antenna complexes. Recent atomic force microscopy pictures of photosynthetic units in intact membranes have revealed that the architecture of these units is variable (Scheuring et al. (2005) Biochim Bhiophys Acta 1712:109-127). In this study, we describe methods for the construction of heterologous photosynthetic units in lipid-bilayers from mixtures of purified LH2 (from Rhodopseudomonas acidophila) and LH1-RC (from Rhodopseudomonas viridis) core complexes. The architecture of these reconstituted photosynthetic units can be varied by controlling ratio of added LH2 to core complexes. The arrangement of the complexes was visualized by electron-microscopy in combination with Fourier analysis. The regular trigonal array of the core complexes seen in the native photosynthetic membrane could be regenerated in the reconstituted membranes by temperature cycling. In the presence of added LH2 complexes, this trigonal symmetry was replaced with orthorhombic symmetry. The small lattice lengths for the latter suggest that the constituent unit of the orthorhombic lattice is the LH2. Fluorescence and fluorescence-excitation spectroscopy was applied to the set of the reconstituted membranes prepared with various proportions of LH2 to core complexes. Remarkably, even though the LH2 complexes contain bacteriochlorophyll a, and the core complexes contain bacteriochlorophyll b, it was possible to demonstrate energy transfer from LH2 to the core complexes. These experiments provide a first step along the path toward investigating how changing the architecture of purple bacterial photosynthetic units affects the overall efficiency of light-harvesting.

Relationship between photosynthetic pigments and chlorophyll fluorescence in soybean under varying phosphorus nutrition at ambient and elevated CO2

USDA-ARS?s Scientific Manuscript database

Photosynthetic pigments such as chlorophyll (Chl) a, Chl b and carotenoids concentration, and chlorophyll fluorescence (CF) have widely been used as indicators of stress and photosynthetic performance in plants. Although photosynthetic pigments and CF are partly interdependent due to absorption and ...

Difference in leaf water use efficiency/photosynthetic nitrogen use efficiency of Bt-cotton and its conventional peer.

PubMed

Guo, Ruqing; Sun, Shucun; Liu, Biao

2016-09-15

This study is to test the effects of Bt gene introduction on the foliar water/nitrogen use efficiency in cotton. We measured leaf stomatal conductance, photosynthetic rate, and transpiration rate under light saturation condition at different stages of a conventional cultivar (zhongmian no. 16) and its counterpart Bt cultivar (zhongmian no. 30) that were cultured on three levels of fertilization, based on which leaf instantaneous water use efficiency was derived. Leaf nitrogen concentration was measured to calculate leaf photosynthetic nitrogen use efficiency, and leaf δ(13)C was used to characterize long term water use efficiency. Bt cultivar was found to have lower stomatal conductance, net photosynthetic rates and transpiration rates, but higher instantaneous and long time water use efficiency. In addition, foliar nitrogen concentration was found to be higher but net photosynthetic rate was lower in the mature leaves of Bt cultivar, which led to lower photosynthetic nitrogen use efficiency. This might result from the significant decrease of photosynthetic rate due to the decrease of stomatal conductance. In conclusion, our findings show that the introduction of Bt gene should significantly increase foliar water use efficiency but decrease leaf nitrogen use efficiency in cotton under no selective pressure.

Comprehensive comparative analysis of kinesins in photosynthetic eukaryotes

PubMed Central

Richardson, Dale N; Simmons, Mark P; Reddy, Anireddy SN

2006-01-01

Background Kinesins, a superfamily of molecular motors, use microtubules as tracks and transport diverse cellular cargoes. All kinesins contain a highly conserved ~350 amino acid motor domain. Previous analysis of the completed genome sequence of one flowering plant (Arabidopsis) has resulted in identification of 61 kinesins. The recent completion of genome sequencing of several photosynthetic and non-photosynthetic eukaryotes that belong to divergent lineages offers a unique opportunity to conduct a comprehensive comparative analysis of kinesins in plant and non-plant systems and infer their evolutionary relationships. Results We used the kinesin motor domain to identify kinesins in the completed genome sequences of 19 species, including 13 newly sequenced genomes. Among the newly analyzed genomes, six represent photosynthetic eukaryotes. A total of 529 kinesins was used to perform comprehensive analysis of kinesins and to construct gene trees using the Bayesian and parsimony approaches. The previously recognized 14 families of kinesins are resolved as distinct lineages in our inferred gene tree. At least three of the 14 kinesin families are not represented in flowering plants. Chlamydomonas, a green alga that is part of the lineage that includes land plants, has at least nine of the 14 known kinesin families. Seven of ten families present in flowering plants are represented in Chlamydomonas, indicating that these families were retained in both the flowering-plant and green algae lineages. Conclusion The increase in the number of kinesins in flowering plants is due to vast expansion of the Kinesin-14 and Kinesin-7 families. The Kinesin-14 family, which typically contains a C-terminal motor, has many plant kinesins that have the motor domain at the N terminus, in the middle, or the C terminus. Several domains in kinesins are present exclusively either in plant or animal lineages. Addition of novel domains to kinesins in lineage-specific groups contributed to the

The construction of an engineered bacterium to remove cadmium from wastewater.

PubMed

Chang, S; Shu, H

2014-01-01

The removal of cadmium (Cd) from wastewater before it is released from factories is important for protecting human health. Although some researchers have developed engineered bacteria, the resistance of these engineered bacteria to Cd have not been improved. In this study, two key genes involved in glutathione synthesis (gshA and gshB), a serine acetyltransferase gene (cysE), a Thlaspi caerulescens phytochelatin synthase gene (TcPCS1), and a heavy metal ATPase gene (TcHMA3) were transformed into Escherichia coli BL21. The resistance of the engineered bacterium to Cd was significantly greater than that of the initial bacterium and the Cd accumulation in the engineered bacterium was much higher than in the initial bacterium. In addition, the Cd resistance of the bacteria harboring gshB, gshA, cysE, and TcPCS1 was higher than that of the bacteria harboring gshA, cysE, and TcPCS1. This finding demonstrated that gshB played an important role in glutathione synthesis and that the reaction catalyzed by glutathione synthase was the limiting step for producing phytochelatins. Furthermore, TcPCS1 had a greater specificity and a higher capacity for removing Cd than SpPCS1, and TcHMA3 not only played a role in T. caerulescens but also functioned in E. coli.

Storage nitrogen co-ordinates leaf expansion and photosynthetic capacity in winter oilseed rape

PubMed Central

Liu, Tao; Ren, Tao; White, Philip J; Cong, Rihuan

2018-01-01

Abstract Storage nitrogen (N) is a buffer pool for maintaining leaf growth and synthesizing photosynthetic proteins, but the dynamics of its forms within the life cycle of a single leaf and how it is influenced by N supply remain poorly understood. A field experiment was conducted to estimate the influence of N supply on leaf growth, photosynthetic characteristics, and N partitioning inthe sixth leaf of winter oilseed rape (Brassica napus L.) from emergence through senescence. Storage N content (Nstore) decreased gradually along with leaf expansion. The relative growth rate based on leaf area (RGRa) was positively correlated with Nstore during leaf expansion. The water-soluble protein form of storage N was the main N source for leaf expansion. After the leaves fully expanded, the net photosynthetic rate (An) followed a linear–plateau response to Nstore, with An stabilizing at the highest value above a threshold and declining below the threshold. Non-protein and SDS (detergent)-soluble protein forms of storage N were the main N sources for maintaining photosynthesis. For the leaf N economy, storage N is used for co-ordinating leaf expansion and photosynthetic capacity. N supply can improve Nstore, thereby promoting leaf growth and biomass. PMID:29669007

Influence of thermal light correlations on photosynthetic structures

NASA Astrophysics Data System (ADS)

de Mendoza, Adriana; Manrique, Pedro; Caycedo-Soler, Felipe; Johnson, Neil F.; Rodríguez, Ferney J.; Quiroga, Luis

2014-03-01

The thermal light from the sun is characterized by both classical and quantum mechanical correlations. These correlations have left a fingerprint on the natural harvesting structures developed through five billion years of evolutionary pressure, specially in photosynthetic organisms. In this work, based upon previous extensive studies of spatio-temporal correlations of light fields, we hypothesize that structures involving photosensitive pigments like those present in purple bacteria vesicles emerge as an evolutionary response to the different properties of incident light. By using burstiness and memory as measures that quantify higher moments of the photon arrival statistics, we generate photon-time traces. They are used to simulate absorption on detectors spatially extended over regions comparable to these light fields coherence length. Finally, we provide some insights into the connection between these photo-statistical features with the photosynthetic membrane architecture and the lights' spatial correlation. Facultad de Ciencias Uniandes.

Dependence of Photosynthetic Capacity, Photosynthetic Pigment Allocation, and Carbon Storage on Nitrogen Levels in Foliage of Aspen Stands

NASA Technical Reports Server (NTRS)

Middleton, Elizabeth M.; Sullivan, Joseph H.; Papagno, Andrea J.

2000-01-01

The role of foliar nitrogen (N) in the seasonal dynamics and vertical canopy distribution of photosynthetic pigments, photosynthetic capacity, and carbon (C) storage was investigated in boreal broadleaved species. The study was conducted at two different aged stands (60 y and 15 y) in 1994 and 1996 in Saskatchewan, Canada as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). Foliage in upper and lower strata was examined for aspen (Populus tremuloides Michx.) and its associated hazelnut shrub (Corylus americana Walt.). We determined that C accumulation, expressed as dry mass per unit leaf area (mg C cm (exp -2)), was linearly dependent on N content (approximately 0.3- 3.5 mg N cm (exp -2))(r (exp 2) = 0.93, n=383, P less than 0.001) when eleven foliage groups were defined according to species, site, and developmental stage. C assembly was greatest in the upper aspen strata of both sites (seasonal average, 40.1 plus or minus 0.6 mg C cm (exp -2)), intermediate in the lower aspen strata (32.7 plus or minus 0.6), and considerably lower, and similar, in the hazelnut shrub layers (23.7 plus or minus 0.6) and in expanding aspen leaves (23.8 plus or minus 0.5); the lowest C assembly per unit N occurred in the two youngest, emerging leaf groups (17.1 plus or minus 0.6). Other relationships among physiological and biochemical variables were typically non-linear and were confounded by inclusion of the three groups of young (i.e., emerging or expanding) leaves, unless these were separately identified. Net C uptake, measured as photosynthetic capacity (A (sub max), micromole CO2 m (exp -2) s (exp -1)), was greater in aspen throughout the season, and optimal in mid-summer at a C:N ratio of approximately 18 (approximately 2.3 %N). When young leaves were excluded and logarithms of both variables were used, A (sub max) was approximately linearly dependent on N (mg N cm (exp-2) (r (exp 2) = 0.85, n= 193, P less than 0.001), attributed to incorporation of N into photosynthetic

Photosynthetic capacity and dry mass partitioning in dwarf and semi-dwarf wheat (Triticum aestivum L.)

NASA Technical Reports Server (NTRS)

Bishop, D. L.; Bugbee, B. G.

1998-01-01

Efficient use of space and high yields are critical for long-term food production aboard the International Space Station. The selection of a full dwarf wheat (less than 30 cm tall) with high photosynthetic and yield potential is a necessary prerequisite for growing wheat in the controlled, volume-limited environments available aboard long-term spaceflight missions. This study evaluated the photosynthetic capacity and carbon partitioning of a full-dwarf wheat cultivar, Super Dwarf, which is routinely used in spaceflight studies aboard U.S. space shuttle and NASA/Mir missions and made comparisons with other dwarf and semi-dwarf wheat cultivars utilized in other ground-based studies in plant space biology. Photosynthetic capacity of the flag leaf in two dwarf (Super Dwarf, BB-19), and three semi-dwarf (Veery-10, Yecora Rojo, IBWSN 199) wheat cultivars (Triticum aestivum L.) was assessed by measuring: net maximum photosynthetic rate, RuBP carboxylation efficiency, chlorophyll concentration and flag leaf area. Dry mass partitioning of carbohydrates to the leaves, sheaths, stems and ear was also assessed. Plants were grown under controlled environmental conditions in three replicate studies: slightly enriched CO2 (370 micromoles mol-1), high photosynthetic photon flux (1000 micromoles m-2 s-1; 58 mol m-2 d-1) for a 16 h photoperiod, 22/15 degrees C day/night temperatures, ample nutrients and water provided by one-half strength Hoagland's nutrient solution (Hoagland and Arnon, 1950). Photosynthetic capacity of the flag leaf was determined at anthesis using net CO2 exchange rate versus internal CO2 concentration curves measured under saturating light (2000 micromoles m-2 s-1) and CO2 (1000 micromoles mol-1). Dwarf wheat cultivars had greater photosynthetic capacities than the taller semi-dwarfs, they averaged 20% higher maximum net photosynthetic rates compared to the taller semi-dwarfs, but these higher rates occurred only at anthesis, had slightly greater carboxylation

Metabolomics evaluation of the impact of smokeless tobacco exposure on the oral bacterium Capnocytophaga sputigena

PubMed Central

Sun, Jinchun; Jin, Jinshan; Beger, Richard D.; Cerniglia, Carl E.; Yang, Maocheng; Chen, Huizhong

2017-01-01

The association between exposure to smokeless tobacco products (STP) and oral diseases is partially due to the physiological and pathological changes in the composition of the oral microbiome and its metabolic profile. However, it is not clear how STPs affect the physiology and ecology of oral microbiota. A UPLC/QTof-MS-based metabolomics study was employed to analyze metabolic alterations in oral bacterium, Capnocytophaga sputigena as a result of smokeless tobacco exposure and to assess the capability of the bacterium to metabolize nicotine. Pathway analysis of the metabolome profiles indicated that smokeless tobacco extracts caused oxidative stress in the bacterium. The metabolomics data also showed that the argininenitric oxide pathway was perturbed by the smokeless tobacco treatment. Results also showed that LC/MS was useful in identifying STP constituents and additives, including caffeine and many flavoring compounds. No significant changes in levels of nicotine and its major metabolites were found when C. sputigena was cultured in a nutrient rich medium, although hydroxylnicotine and cotinine N-oxide were detected in the bacterial metabolites suggesting that nicotine metabolism might be present as a minor degradation pathway in the bacterium. Study results provide new insights regarding the physiological and toxicological effects of smokeless tobacco on oral bacterium C. sputigena and associated oral health as well as measuring the ability of the oral bacterium to metabolize nicotine. PMID:27480511

Metabolomics evaluation of the impact of smokeless tobacco exposure on the oral bacterium Capnocytophaga sputigena.

PubMed

Sun, Jinchun; Jin, Jinshan; Beger, Richard D; Cerniglia, Carl E; Yang, Maocheng; Chen, Huizhong

2016-10-01

The association between exposure to smokeless tobacco products (STP) and oral diseases is partially due to the physiological and pathological changes in the composition of the oral microbiome and its metabolic profile. However, it is not clear how STPs affect the physiology and ecology of oral microbiota. A UPLC/QTof-MS-based metabolomics study was employed to analyze metabolic alterations in oral bacterium, Capnocytophaga sputigena as a result of smokeless tobacco exposure and to assess the capability of the bacterium to metabolize nicotine. Pathway analysis of the metabolome profiles indicated that smokeless tobacco extracts caused oxidative stress in the bacterium. The metabolomics data also showed that the arginine-nitric oxide pathway was perturbed by the smokeless tobacco treatment. Results also showed that LC/MS was useful in identifying STP constituents and additives, including caffeine and many flavoring compounds. No significant changes in levels of nicotine and its major metabolites were found when C. sputigena was cultured in a nutrient rich medium, although hydroxylnicotine and cotinine N-oxide were detected in the bacterial metabolites suggesting that nicotine metabolism might be present as a minor degradation pathway in the bacterium. Study results provide new insights regarding the physiological and toxicological effects of smokeless tobacco on oral bacterium C. sputigena and associated oral health as well as measuring the ability of the oral bacterium to metabolize nicotine. Published by Elsevier Ltd.

Near-complete genome sequence of the cellulolytic Bacterium Bacteroides ( Pseudobacteroides) cellulosolvens ATCC 35603

DOE PAGES

Dassa, Bareket; Utturkar, Sagar M.; Hurt, Richard A.; ...

2015-09-24

We report the single-contig genome sequence of the anaerobic, mesophilic, cellulolytic bacterium, Bacteroides cellulosolvens. The bacterium produces a particularly elaborate cellulosome system, whereas the types of cohesin-dockerin interactions are opposite of other known cellulosome systems: cell-surface attachment is thus mediated via type-I interactions whereas enzymes are integrated via type-II interactions.

Effects of deer on the photosynthetic performance of invasive and native forest herbs.

PubMed

Heberling, J Mason; Brouwer, Nathan L; Kalisz, Susan

2017-03-01

Overabundant generalist herbivores can facilitate non-native plant invasions, presumably through direct and indirect modifications to the environment that affect plant performance. However, ecophysiological mechanisms behind ungulate-mediated plant invasions have not been well-studied. At a long-term Odocoileus virginianus (white-tailed deer) exclusion site in a temperate deciduous forest, we quantified deer-mediated ecophysiological impacts on an invasive biennial Alliaria petiolata (garlic mustard) and two palatable native herbaceous perennials, Maianthemum racemosum and Trillium grandiflorum . In mid-summer, we found that leaf-level light availability was higher in unfenced areas compared with areas fenced to exclude deer. Alliaria in unfenced areas exhibited 50 % higher mean maximum photosynthetic rates compared with fenced areas. Further, specific leaf area decreased by 48 % on average in unfenced areas, suggesting leaf structural responses to higher light levels. Similarly, Maianthemum had 42 % higher mean photosynthetic rates and 33 % decreased mean specific leaf area in unfenced areas, but these functional advantages were likely countered by high rates of deer herbivory. By contrast, Trillium exhibited significantly lower (26 %) maximum photosynthetic rates in unfenced areas, but SLA did not differ. Deer-mediated differences in light saturated photosynthetic rates for all three species were only significant during months with overstory tree canopy cover, when light availability in the herb layer was significantly lower in fenced areas. Alliaria 's enhanced photosynthetic rates implicate overabundant deer, a situation that is nearly ubiquitous across its invaded range. Collectively, our results provide empirical evidence that generalist herbivores can alter non-native plant physiology to facilitate invasion.

[A rarely isolated bacterium in microbiology laboratories: Streptococcus uberis].

PubMed

Eryıldız, Canan; Bukavaz, Şebnem; Gürcan, Şaban; Hatipoğlu, Osman

2017-04-01

Streptococcus uberis is a gram-positive bacterium that is mostly responsible for mastitis in cattle. The bacterium rarely has been associated with human infections. Conventional phenotyphic methods can be inadequate for the identification of S.uberis; and in microbiology laboratories S.uberis is confused with the other streptococci and enterococci isolates. Recently, molecular methods are recommended for the accurate identification of S.uberis isolates. The aim of this report is to present a lower respiratory tract infection case caused by S.uberis and the microbiological methods for identification of this bacterium. A 66-year-old male patient with squamous cell lung cancer who received radiotherapy was admitted in our hospital for the control. According to the chest X-Ray, patient was hospitalized with the prediagnosis of ''cavitary tumor, pulmonary abscess''. In the first day of the hospitalization, blood and sputum cultures were drawn. Blood culture was negative, however, Candida albicans was isolated in the sputum culture and it was estimated to be due to oral lesions. After two weeks from the hospitalization, sputum sample was taken from the patient since he had abnormal respiratory sounds and cough complaint. In the Gram stained smear of the sputum there were abundant leucocytes and gram-positive cocci, and S.uberis was isolated in both 5% sheep blood and chocolate agar media. Bacterial identification and antibiotic susceptibility tests were performed by VITEK 2 (Biomerieux, France) and also, the bacterium was identified by matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) based VITEK MS system as S.uberis. The isolate was determined susceptible to ampicillin, erythromycin, clindamycin, levofloxacin, linezolid, penicillin, cefotaxime, ceftriaxone, tetracycline and vancomycin. 16S, 23S ribosomal RNA and 16S-23S intergenic spacer gene regions were amplified with specific primers and partial DNA sequence analysis of 16S

Trichloroethylene Biodegradation by a Methane-Oxidizing Bacterium †

PubMed Central

Little, C. Deane; Palumbo, Anthony V.; Herbes, Stephen E.; Lidstrom, Mary E.; Tyndall, Richard L.; Gilmer, Penny J.

1988-01-01

Trichloroethylene (TCE), a common groundwater contaminant, is a suspected carcinogen that is highly resistant to aerobic biodegradation. An aerobic, methane-oxidizing bacterium was isolated that degrades TCE in pure culture at concentrations commonly observed in contaminated groundwater. Strain 46-1, a type I methanotrophic bacterium, degraded TCE if grown on methane or methanol, producing CO2 and water-soluble products. Gas chromatography and 14C radiotracer techniques were used to determine the rate, methane dependence, and mechanism of TCE biodegradation. TCE biodegradation by strain 46-1 appears to be a cometabolic process that occurs when the organism is actively metabolizing a suitable growth substrate such as methane or methanol. It is proposed that TCE biodegradation by methanotrophs occurs by formation of TCE epoxide, which breaks down spontaneously in water to form dichloroacetic and glyoxylic acids and one-carbon products. Images PMID:16347616

Photosynthetic physiology and biomass partitioning in the model diatom Phaeodactylum tricornutum grown in a sinusoidal light regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jallet, Denis; Caballero, Michael A.; Gallina, Alessandra A.

Photosynthetic microbes respond to changing light environments to balance photosynthetic process with light induced damage and photoinhibition. There have been very few characterizations of photosynthetic physiology or biomass partitioning during the day in mass culture. Understanding the constraints on photosynthetic efficiency and biomass accumulation are necessary for engineering superior strains or cultivation methods. We observed the photosynthetic physiology of nutrient replete Phaeodactylum tricornutum growing in light environments that mimic those found in rapidly mixing, outdoor, low biomass photobioreactors. We found little evidence for photoinhibition or non-photochemical quenching in situ, suggesting photosynthesis remains highly efficient throughout the day. Cells doubled theirmore » organic carbon from dawn to dusk and a small percentage – around 20% – of this carbon was allocated to carbohydrates or triacylglycerol. We thus conclude that the self-shading provided by dense culturing of P. tricornutum inhibits the induction of photodamage, and energy dissipation processes that would otherwise lower productivity in an outdoor photobioreactor.« less

Photosynthetic physiology and biomass partitioning in the model diatom Phaeodactylum tricornutum grown in a sinusoidal light regime

DOE PAGES

Jallet, Denis; Caballero, Michael A.; Gallina, Alessandra A.; ...

2016-06-11

Photosynthetic microbes respond to changing light environments to balance photosynthetic process with light induced damage and photoinhibition. There have been very few characterizations of photosynthetic physiology or biomass partitioning during the day in mass culture. Understanding the constraints on photosynthetic efficiency and biomass accumulation are necessary for engineering superior strains or cultivation methods. We observed the photosynthetic physiology of nutrient replete Phaeodactylum tricornutum growing in light environments that mimic those found in rapidly mixing, outdoor, low biomass photobioreactors. We found little evidence for photoinhibition or non-photochemical quenching in situ, suggesting photosynthesis remains highly efficient throughout the day. Cells doubled theirmore » organic carbon from dawn to dusk and a small percentage – around 20% – of this carbon was allocated to carbohydrates or triacylglycerol. We thus conclude that the self-shading provided by dense culturing of P. tricornutum inhibits the induction of photodamage, and energy dissipation processes that would otherwise lower productivity in an outdoor photobioreactor.« less

Engineering cyanobacteria for photosynthetic production of 3-hydroxybutyrate directly from CO2.

PubMed

Wang, Bo; Pugh, Shawn; Nielsen, David R; Zhang, Weiwen; Meldrum, Deirdre R

2013-03-01

(S)- and (R)-3-hydroxybutyrate (3HB) are precursors to synthesize the biodegradable plastics polyhydroxyalkanoates (PHAs) and many fine chemicals. To date, however, their production has been restricted to petroleum-based chemical industry and sugar-based microbial fermentation, limiting its sustainability and economical feasibility. With the ability to fix CO2 photosynthetically, cyanobacteria have attracted increasing interest as a biosynthesis platform to produce fuels and chemicals from alternative renewable resources. To this end, synthesis metabolic pathways have been constructed and optimized in cyanobacterium Synechocystis sp. PCC 6803 to photosynthetically produce (S)- and (R)-3HB directly from CO2. Both types of 3HB molecules were produced and readily secreted from Synechocystis cells without over-expression of transporters. Additional inactivation of the competing pathway by deleting slr1829 and slr1830 (encoding PHB polymerase) from the Synechocystis genome further promoted the 3HB production. Up to 533.4mg/L 3HB has been produced after photosynthetic cultivation of the engineered cyanobacterium Synechocystis TABd for 21 days. Further analysis indicated that the phosphate consumption during the photoautrophic growth and the concomitant elevated acetyl-CoA pool acted as a key driving force for 3HB biosynthesis in Synechocystis. For the first time, the study has demonstrated the feasibility of photosynthetic production of (S)- and (R)-3HB directly from sunlight and CO2. Copyright © 2013 Elsevier Inc. All rights reserved.

Draft Genome Sequence of the Cellulolytic Bacterium Clostridium papyrosolvens C7 (ATCC 700395).

PubMed

Zepeda, Veronica; Dassa, Bareket; Borovok, Ilya; Lamed, Raphael; Bayer, Edward A; Cate, Jamie H D

2013-09-12

We report the draft genome sequence of the cellulose-degrading bacterium Clostridium papyrosolvens C7, originally isolated from mud collected below a freshwater pond in Massachusetts. This Gram-positive bacterium grows in a mesophilic anaerobic environment with filter paper as the only carbon source, and it has a simple cellulosome system with multiple carbohydrate-degrading enzymes.

Draft Genome Sequence of the Cellulolytic Bacterium Clostridium papyrosolvens C7 (ATCC 700395)

PubMed Central

Zepeda, Veronica; Dassa, Bareket; Borovok, Ilya; Lamed, Raphael; Bayer, Edward A.

2013-01-01

We report the draft genome sequence of the cellulose-degrading bacterium Clostridium papyrosolvens C7, originally isolated from mud collected below a freshwater pond in Massachusetts. This Gram-positive bacterium grows in a mesophilic anaerobic environment with filter paper as the only carbon source, and it has a simple cellulosome system with multiple carbohydrate-degrading enzymes. PMID:24029755

Photosynthetic capacity peaks at intermediate size in temperate deciduous trees.

PubMed

Thomas, Sean C

2010-05-01

Studies of age-related changes in leaf functional biology have generally been based on dichotomous comparisons of young and mature individuals (e.g., saplings and mature canopy trees), with little data available to describe changes through the entire ontogeny of trees, particularly of broadleaf angiosperms. Leaf-level gas-exchange and morphological parameters were quantified in situ in the upper canopy of trees acclimated to high light conditions, spanning a wide range of ontogenetic stages from saplings (approximately 1 cm in stem diameter) to trees >60 cm d.b.h. and nearing their maximum lifespan, in three temperate deciduous tree species in central Ontario, Canada. Traits associated with growth performance, including leaf photosynthetic capacity (expressed on either an area, mass or leaf N basis), stomatal conductance, leaf size and leaf N content, generally showed a unimodal ('hump-shaped') pattern, with peak values at an intermediate ontogenetic stage. In contrast, leaf mass per area (LMA) and related morphological parameters (leaf thickness, leaf tissue density, leaf C content) increased monotonically with tree size, as did water-use efficiency; these monotonic relationships were well described by simple allometric functions of the form Y = aX(b). For traits showing unimodal patterns, tree size corresponding to the trait maximum differed markedly among traits: all three species showed a similar pattern in which the peak for leaf size occurred in trees approximately 2-6 cm d.b.h., followed by leaf chemical traits and photosynthetic capacity on a mass or leaf N basis and finally by photosynthetic capacity on a leaf area basis, which peaked approximately at the size of reproductive onset. It is argued that ontogenetic increases in photosynthetic capacity and related traits early in tree ontogeny are general among relatively shade-tolerant tree species that have a low capacity for leaf-level acclimation, as are declines in this set of traits late in tree ontogeny.

Energy transfer in purple bacterial photosynthetic units from cells grown in various light intensities.

PubMed

Niedzwiedzki, Dariusz M; Gardiner, Alastair T; Blankenship, Robert E; Cogdell, Richard J

2018-05-03

Three photosynthetic membranes, called intra-cytoplasmic membranes (ICMs), from wild-type and the ∆pucBA abce mutant of the purple phototrophic bacterium Rps. palustris were investigated using optical spectroscopy. The ICMs contain identical light-harvesting complex 1-reaction centers (LH1-RC) but have various spectral forms of light-harvesting complex 2 (LH2). Spectroscopic studies involving steady-state absorption, fluorescence, and femtosecond time-resolved absorption at room temperature and at 77 K focused on inter-protein excitation energy transfer. The studies investigated how energy transfer is affected by altered spectral features of the LH2 complexes as those develop under growth at different light conditions. The study shows that LH1 → LH2 excitation energy transfer is strongly affected if the LH2 complex alters its spectroscopic signature. The LH1 → LH2 excitation energy transfer rate modeled with the Förster mechanism and kinetic simulations of transient absorption of the ICMs demonstrated that the transfer rate will be 2-3 times larger for ICMs accumulating LH2 complexes with the classical B800-850 spectral signature (grown in high light) compared to the ICMs from the same strain grown in low light. For the ICMs from the ∆pucBA abce mutant, in which the B850 band of the LH2 complex is blue-shifted and almost degenerate with the B800 band, the LH1 → LH2 excitation energy transfer was not observed nor predicted by calculations.

Effects of ploidy level and haplotype on variation of photosynthetic traits: Novel evidence from two Fragaria species

PubMed Central

Gao, Song; Yan, Qiaodi; Chen, Luxi; Song, Yaobin; Fu, Chengxin; Dong, Ming

2017-01-01

To reveal the effects of ploidy level and haplotype on photosynthetic traits, we chose 175 genotypes of wild strawberries belonging to two haplotypes at two types of ploidy levels (diploidy and tetraploidy) and measured photosynthetic traits. Our results revealed that ploidy significantly affected the characteristics of light-response curves, CO2-response curves, and leaf gas exchange parameters, except intercellular CO2 concentration (Ci). Tetraploid species had a lower light saturation point (LSP) and CO2 saturation point (CSP), higher light compensation point (LCP), dark respiration (Rd), and CO2 compensation point (CCP) than diploid species. Furthermore, tetraploid species have lower photosynthetic capacity than diploid species, including net photosynthetic rate (Pn), stomatal conductivity (Gs), and transpiration rate (Tr). In addition, haplotype had a significant effect on LSP, CSP, Tr, and Ci as well as a significant interactive effect between ploidy and haplotype on the maximal photosynethic rate of the light-response curve and Rd. Most of the variance existed within haplotypes among individuals. These results suggest that polyploidization was the main driver for the evolution of photosynthesis with increasing ploidy level (i.e. from diploidy to tetraploidy in Fragaria species), while the origin of a chromosome could also affect the photosynthetic traits and the polyploidization effect on photosynthetic traits. PMID:28644876

Effects of ploidy level and haplotype on variation of photosynthetic traits: Novel evidence from two Fragaria species.

PubMed

Gao, Song; Yan, Qiaodi; Chen, Luxi; Song, Yaobin; Li, Junmin; Fu, Chengxin; Dong, Ming

2017-01-01

To reveal the effects of ploidy level and haplotype on photosynthetic traits, we chose 175 genotypes of wild strawberries belonging to two haplotypes at two types of ploidy levels (diploidy and tetraploidy) and measured photosynthetic traits. Our results revealed that ploidy significantly affected the characteristics of light-response curves, CO2-response curves, and leaf gas exchange parameters, except intercellular CO2 concentration (Ci). Tetraploid species had a lower light saturation point (LSP) and CO2 saturation point (CSP), higher light compensation point (LCP), dark respiration (Rd), and CO2 compensation point (CCP) than diploid species. Furthermore, tetraploid species have lower photosynthetic capacity than diploid species, including net photosynthetic rate (Pn), stomatal conductivity (Gs), and transpiration rate (Tr). In addition, haplotype had a significant effect on LSP, CSP, Tr, and Ci as well as a significant interactive effect between ploidy and haplotype on the maximal photosynethic rate of the light-response curve and Rd. Most of the variance existed within haplotypes among individuals. These results suggest that polyploidization was the main driver for the evolution of photosynthesis with increasing ploidy level (i.e. from diploidy to tetraploidy in Fragaria species), while the origin of a chromosome could also affect the photosynthetic traits and the polyploidization effect on photosynthetic traits.

Insights from Placing Photosynthetic Light Harvesting into Context.

PubMed

Demmig-Adams, Barbara; Stewart, Jared J; Burch, Tyson A; Adams, William W

2014-08-21

Solar-energy conversion through natural photosynthesis forms the base of virtually all food chains on Earth and provides fiber, materials, and fuels, as well as inspiration for the design of biomimetic energy-conversion systems. We summarize well-known as well as recently discovered feedback loops between natural light-harvesting systems and whole-organism function in natural settings. We propose that the low effective quantum yield of natural light-harvesting systems in high light is caused by downstream limitations rather than unavoidable intrinsic vulnerabilities. We evaluate potential avenues, and their costs and benefits, for increasing the maximal rate and photon yield of photosynthesis in high light in plants and photosynthetic microbes. By summarizing mechanisms observable only in complex systems (whole plants, algae, or, in some cases, intact leaves), we aim to stimulate future research efforts on reciprocal feedback loops between light harvesting and downstream processes in whole organisms and to provide additional arguments for the significance of research on photosynthetic light harvesting.

An allosteric photoredox catalyst inspired by photosynthetic machinery

DOE PAGES

Lifschitz, Alejo M.; Young, Ryan M.; Mendez-Arroyo, Jose; ...

2015-03-30

Biological photosynthetic machinery allosterically regulate light harvesting via conformational and electronic changes at the antenna protein complexes as a response to specific chemical inputs. Fundamental limitations in current approaches to regulating inorganic light-harvesting mimics prevent their use in catalysis. Here we show that a light-harvesting antenna/reaction centre mimic can be regulated by utilizing a coordination framework incorporating antenna hemilabile ligands and assembled via a high-yielding, modular approach. As in nature, allosteric regulation is afforded by coupling the conformational changes to the disruptions in the electrochemical landscape of the framework upon recognition of specific coordinating analytes. The hemilabile ligands enable switchingmore » using remarkably mild and redox-inactive inputs, allowing one to regulate the photoredox catalytic activity of the photosynthetic mimic reversibly and in situ. Furthermore, we demonstrate that bioinspired regulatory mechanisms can be applied to inorganic light-harvesting arrays displaying switchable catalytic properties and with potential uses in solar energy conversion and photonic devices.« less

Engineering photosynthetic organisms for the production of biohydrogen

DOE PAGES

Dubini, Alexandra; Ghirardi, Maria L.

2014-03-27

Oxygenic photosynthetic organisms such as green algae are capable of absorbing sunlight and converting the chemical energy into hydrogen gas. This process takes advantage of the photosynthetic apparatus of these organisms which links water oxidation to H 2 production. Biological H 2 has therefore the potential to be an alternative fuel of the future and shows great promise for generating large scale sustainable energy. Microalgae are able to produce H 2 under light anoxic or dark anoxic condition by activating 3 different pathways that utilize the hydrogenases as catalysts. In this review, we highlight the principal barriers that prevent hydrogenmore » production in green algae and how those limitations are being addressed, through metabolic and genetic engineering. We also discuss the major challenges and bottlenecks facing the development of future commercial algal photobiological systems for H 2 production. Lastly we provide suggestions for future strategies and potential new techniques to be developed towards an integrated system with optimized hydrogen production.« less

An allosteric photoredox catalyst inspired by photosynthetic machinery

PubMed Central

Lifschitz, Alejo M.; Young, Ryan M.; Mendez-Arroyo, Jose; Stern, Charlotte L.; McGuirk, C. Michael; Wasielewski, Michael R.; Mirkin, Chad A.

2015-01-01

Biological photosynthetic machinery allosterically regulate light harvesting via conformational and electronic changes at the antenna protein complexes as a response to specific chemical inputs. Fundamental limitations in current approaches to regulating inorganic light-harvesting mimics prevent their use in catalysis. Here we show that a light-harvesting antenna/reaction centre mimic can be regulated by utilizing a coordination framework incorporating antenna hemilabile ligands and assembled via a high-yielding, modular approach. As in nature, allosteric regulation is afforded by coupling the conformational changes to the disruptions in the electrochemical landscape of the framework upon recognition of specific coordinating analytes. The hemilabile ligands enable switching using remarkably mild and redox-inactive inputs, allowing one to regulate the photoredox catalytic activity of the photosynthetic mimic reversibly and in situ. Thus, we demonstrate that bioinspired regulatory mechanisms can be applied to inorganic light-harvesting arrays displaying switchable catalytic properties and with potential uses in solar energy conversion and photonic devices. PMID:25817586

Estimation of photosynthetic capacity using MODIS polarization: 1988 proposal to NASA Headquarters

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern C.

1992-01-01

The remote sensing community has clearly identified the utility of NDVI (normalized difference vegetation index) and SR (simple ratio) and other vegetation indices for estimating such metrics of landscape ecology as green foliar biomass, photosynthetic capacity, and net primary production. Both theoretical and empirical investigations have established cause and effect relationships between the photosynthetic process in plant canopies and these combinations of remotely sensed data. Yet it has also been established that the relationships exhibit considerable variability that appears to be ecosystem-dependent and may represent a source of ecologically important information. The overall hypothesis of this proposal is that the ecosystem-dependent variability in the various vegetation indices is in part attributable to the effects of specular reflection. The polarization channels on MODIS provide the potential to estimate this specularly reflected light and allow the modification of the vegetation indices to better measure the photosynthetic process in plant canopies. In addition, these polarization channels potentially provide additional ecologically important information about the plant canopy.

Designer organisms for photosynthetic production of ethanol from carbon dioxide and water

DOEpatents

Lee, James Weifu [Knoxville, TN

2011-07-05

The present invention provides a revolutionary photosynthetic ethanol production technology based on designer transgenic plants, algae, or plant cells. The designer plants, designer algae, and designer plant cells are created such that the endogenous photosynthesis regulation mechanism is tamed, and the reducing power (NADPH) and energy (ATP) acquired from the photosynthetic water splitting and proton gradient-coupled electron transport process are used for immediate synthesis of ethanol (CH.sub.3CH.sub.2OH) directly from carbon dioxide (CO.sub.2) and water (H.sub.2O). The ethanol production methods of the present invention completely eliminate the problem of recalcitrant lignocellulosics by bypassing the bottleneck problem of the biomass technology. The photosynthetic ethanol-production technology of the present invention is expected to have a much higher solar-to-ethanol energy-conversion efficiency than the current technology and could also help protect the Earth's environment from the dangerous accumulation of CO.sub.2 in the atmosphere.

Photosynthetic parameters in the Beaufort Sea in relation to the phytoplankton community structure

NASA Astrophysics Data System (ADS)

Huot, Y.; Babin, M.; Bruyant, F.

2013-05-01

To model phytoplankton primary production from remotely sensed data, a method to estimate photosynthetic parameters describing the photosynthetic rates per unit biomass is required. Variability in these parameters must be related to environmental variables that are measurable remotely. In the Arctic, a limited number of measurements of photosynthetic parameters have been carried out with the concurrent environmental variables needed. Such measurements and their relationship to environmental variables will be required to improve the accuracy of remotely sensed estimates of phytoplankton primary production and our ability to predict future changes. During the MALINA cruise, a large dataset of these parameters was obtained. Together with previously published datasets, we use environmental and trophic variables to provide functional relationships for these parameters. In particular, we describe several specific aspects: the maximum rate of photosynthesis (Pmaxchl) normalized to chlorophyll decreases with depth and is higher for communities composed of large cells; the saturation parameter (Ek) decreases with depth but is independent of the community structure; and the initial slope of the photosynthesis versus irradiance curve (αchl) normalized to chlorophyll is independent of depth but is higher for communities composed of larger cells. The photosynthetic parameters were not influenced by temperature over the range encountered during the cruise (-2 to 8 °C).

Photosynthetic parameters in the Beaufort Sea in relation to the phytoplankton community structure

NASA Astrophysics Data System (ADS)

Huot, Y.; Babin, M.; Bruyant, F.

2013-01-01

To model phytoplankton primary production from remotely sensed data a method to estimate photosynthetic parameters describing the photosynthetic rates per unit biomass is required. Variability in these parameters must be related to environmental variables that are measurable remotely. In the Arctic, a limited number of measurements of photosynthetic parameter have been carried out with the concurrent environmental variables needed. Therefore, to improve the accuracy of remote estimates of phytoplankton primary production as well as our ability to predict changes in the future such measurements and relationship to environmental variables are required. During the MALINA cruise, a large dataset of these parameters were obtained. Together with previously published datasets, we use environmental and trophic variables to provide functional relationships for these parameters. In particular, we describe several specific aspects: the maximum rate of photosynthesis (Pmaxchl) normalized to chlorophyll decreases with depth and is higher for communities composed of large cells; the saturation parameter (Ek) decreases with depth but is independent of the community structure; and the initial slope of the photosynthesis versus irradiance curve (αchl) normalized to chlorophyll is independent of depth but is higher for communities composed of larger cells. The photosynthetic parameters were not influenced by temperature over the range encountered during the cruise (-2 to 8 °C).

Evidence for anoxygenic photosynthesis from the distribution of bacteriochlorophylls in the Black Sea.

PubMed

Repeta, D J; Simpson, D J; Jorgensen, B B; Jannasch, H W

1989-11-02

The contribution of anoxygenic photosynthesis to carbon cycling in the Black Sea, the world's largest body of anoxic marine water, has been vigorously investigated and debated for over four decades. Penetration of light into the sulphide-containing deep water may result in a zone of anaerobic primary production by photosynthetic bacteria. We report here the results of analyses of photosynthetic pigments in samples of suspended particulate matter collected from two stations in the western basin of the Black Sea. Our data demonstrate high concentrations of a bacterio-chlorophyll at the chemocline, and thus the potential for anoxygenic photosynthesis as a component of primary production in the carbon cycle of the Black Sea. More than 95% of the pigments in the bacteriochlorophyll-maximum are accounted for by a series of aromatic carotenoids and bacteriochlorophylls-e, including a previously unreported geranyl ester of 4-i-butyl bacteriochlorophyll-e. The distribution of pigments is characteristic of the obligate phototrophs Chlorobium phaeobacteroides and C. phaeovibriodes. Total depth-integrated bacteriochlorophyll at one station exceeded total chlorophyll-a in the overlying oxygenated portion of the euphotic zone. We suggest that anoxygenic photosynthesis is a relatively recent phenomenon in the Black Sea initiated by shallowing of the chemocline over the past decade and development of an anoxic layer devoid of O2 and H2S.

Field-cycling NMR with high-resolution detection under magic-angle spinning: determination of field-window for nuclear hyperpolarization in a photosynthetic reaction center.

PubMed

Gräsing, Daniel; Bielytskyi, Pavlo; Céspedes-Camacho, Isaac F; Alia, A; Marquardsen, Thorsten; Engelke, Frank; Matysik, Jörg

2017-09-21

Several parameters in NMR depend on the magnetic field strength. Field-cycling NMR is an elegant way to explore the field dependence of these properties. The technique is well developed for solution state and in relaxometry. Here, a shuttle system with magic-angle spinning (MAS) detection is presented to allow for field-dependent studies on solids. The function of this system is demonstrated by exploring the magnetic field dependence of the solid-state photochemically induced nuclear polarization (photo-CIDNP) effect. The effect allows for strong nuclear spin-hyperpolarization in light-induced spin-correlated radical pairs (SCRPs) under solid-state conditions. To this end, 13 C MAS NMR is applied to a photosynthetic reaction center (RC) of the purple bacterium Rhodobacter (R.) sphaeroides wildtype (WT). For induction of the effect in the stray field of the magnet and its subsequent observation at 9.4 T under MAS NMR conditions, the sample is shuttled by the use of an aerodynamically driven sample transfer technique. In the RC, we observe the effect down to 0.25 T allowing to determine the window for the occurrence of the effect to be between about 0.2 and 20 T.

Co-regulation of photosynthetic capacity by nitrogen, phosphorus and magnesium in a subtropical Karst forest in China.

PubMed

Wang, Jing; Wen, Xuefa; Zhang, Xinyu; Li, Shenggong; Zhang, Da-Yong

2018-05-09

Leaf photosynthetic capacity is mainly constrained by nitrogen (N) and phosphorus (P). Little attention has been given to the photosynthetic capacity of mature forests with high calcium (Ca) and magnesium (Mg) in the Karst critical zone. We measured light-saturated net photosynthesis (A sat ), photosynthetic capacity (maximum carboxylation rate [V cmax ], and maximum electron transport rate [J max ]) as well as leaf nutrient contents (N, P, Ca, Mg, potassium [K], and sodium [Na]), leaf mass per area (LMA), and leaf thickness (LT) in 63 dominant plants in a mature subtropical forest in the Karst critical zone in southwestern China. Compared with global data, plants showed higher A sat for a given level of P. V cmax and J max were mainly co-regulated by N, P, Mg, and LT. The ratios of V cmax to N or P, and J max to N or P were significantly positively related to Mg. We speculate that the photosynthetic capacity of Karst plants can be modified by Mg because Mg can enhance photosynthetic N and P use efficiency.

Overproduction of Hydrogen From an Anaerobic Bacterium

DTIC Science & Technology

2008-12-01

fixation of nitrogen ( Haber - Bosch process), mostly to produce fertilizer. Nitrogenase provides a catalytic alternative to the commercial fixation of...the culture and suggests a uniquely simple hydrogen reactor design based on renewable feedstocks. 1. INTRODUCTION Hydrogen is an ideal... renewable feedstocks. Clostridium phytofermentans is a recently- discovered anaerobic bacterium, reported to possess cellulase enzymes that degrade

The mechanisms by which phenanthrene affects the photosynthetic apparatus of cucumber leaves.

PubMed

Jin, Liqiao; Che, Xingkai; Zhang, Zishan; Li, Yuting; Gao, Huiyuan; Zhao, Shijie

2017-02-01

Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) that is widely distributed in the environment and seriously affects the growth and development of plants. To clarify the mechanisms of the direct effects of phenanthrene on the plant photosynthetic apparatus, we measured short-term phenanthrene-treated cucumber leaves. Phenanthrene inhibited Rubisco carboxylation activity, decreasing photosynthesis rates (Pn). And phenanthrene inhibited photosystem II (PSII) activity, thereby blocking photosynthetic electron transport. The inhibition of the light and dark reactions decreased the photosynthetic electron transport rate (ETR) and increased the excitation pressure (1-qP). Under high light, the maximum photochemical efficiency of photosystem II (F v /F m ) in phenanthrene-treated cucumber leaves decreased significantly, but photosystem I (PSI) activity (Δ I/I o ) did not. Phenanthrene also caused a J-point rise in the OJIP curve under high light, which indicated that the acceptor side of PSII Q A to Q B electron transfer was restricted. This was primarily due to the net degradation of D1 protein, which is caused by the accumulation of reactive oxygen species (ROS) in phenanthrene-treated cucumber leaves under high light. This study demonstrated that phenanthrene could directly inhibit photosynthetic electron transport and Rubisco carboxylation activity to decrease net Pn. Under high light, phenanthrene caused the accumulation of ROS, resulting in net increases in D1 protein degradation and consequently causing PSII photoinhibition. Copyright © 2016 Elsevier Ltd. All rights reserved.

Changes in growth, photosynthetic activities, biochemical parameters and amino acid profile of Thompson Seedless grapes (Vitis vinifera L.).

PubMed

Somkuwar, R G; Bahetwar, Anita; Khan, I; Satisha, J; Ramteke, S D; Itroutwar, Prerna; Bhongale, Aarti; Oulkar, Dashrath

2014-11-01

The study on photosynthetic activity and biochemical parameters in Thompson Seedless grapes grafted on Dog Ridge rootstock and its impact on growth, yield and amino acid profile at various stages of berry development was conducted during the year 2012-2013. Leaf and berry samples from ten year old vines of Thompson Seedless were collected at different growth and berry developmental stages. The analysis showed difference in photosynthetic activity, biochemical parameters and amino acid status with the changes in berry development stage. Higher photosynthetic rate of 17.39 umol cm(-2) s(-1) was recorded during 3-4mm berry size and the lowest (10.08 umol cm(-2) s(-1)) was recorded during the veraison stage. The photosynthetic activity showed gradual decrease with the onset of harvest while the different biochemical parameters showed increase and decrease from one stage to another in both berry and leaves. Changes in photosynthetic activity and biochemical parameters thereby affected the growth, yield and amino acid content of the berry. Positive correlation of leaf area and photosynthetic rate was recorded during the period of study. Reducing sugar (352.25 mg g(-1)) and total carbohydrate (132.52 mg g(-1)) was more in berries as compared to leaf. Amino acid profile showed variations in different stages of berry development. Marked variations in photosynthetic as well as biochemical and amino acid content at various berry development stages was recorded and thereby its cumulative effect on the development of fruit quality.

Leaf Photosynthetic Parameters Related to Biomass Accumulation in a Global Rice Diversity Survey1[OPEN

PubMed Central

Zheng, Guangyong; Hamdani, Saber; Essemine, Jemaa; Song, Qingfeng; Wang, Hongru

2017-01-01

Mining natural variations is a major approach to identify new options to improve crop light use efficiency. So far, successes in identifying photosynthetic parameters positively related to crop biomass accumulation through this approach are scarce, possibly due to the earlier emphasis on properties related to leaf instead of canopy photosynthetic efficiency. This study aims to uncover rice (Oryza sativa) natural variations to identify leaf physiological parameters that are highly correlated with biomass accumulation, a surrogate of canopy photosynthesis. To do this, we systematically investigated 14 photosynthetic parameters and four morphological traits in a rice population, which consists of 204 U.S. Department of Agriculture-curated minicore accessions collected globally and 11 elite Chinese rice cultivars in both Beijing and Shanghai. To identify key components responsible for the variance of biomass accumulation, we applied a stepwise feature-selection approach based on linear regression models. Although there are large variations in photosynthetic parameters measured in different environments, we observed that photosynthetic rate under low light (Alow) was highly related to biomass accumulation and also exhibited high genomic inheritability in both environments, suggesting its great potential to be used as a target for future rice breeding programs. Large variations in Alow among modern rice cultivars further suggest the great potential of using this parameter in contemporary rice breeding for the improvement of biomass and, hence, yield potential. PMID:28739819

Internal and external factors affecting photosynthetic pigment composition in plants: a meta-analytical approach.

PubMed

Esteban, Raquel; Barrutia, Oihana; Artetxe, Unai; Fernández-Marín, Beatriz; Hernández, Antonio; García-Plazaola, José Ignacio

2015-04-01

Photosynthetic pigment composition has been a major study target in plant ecophysiology during the last three decades. Although more than 2000 papers have been published, a comprehensive evaluation of the responses of photosynthetic pigment composition to environmental conditions is not yet available. After an extensive survey, we compiled data from 525 papers including 809 species (subkingdom Viridiplantae) in which pigment composition was described. A meta-analysis was then conducted to assess the ranges of photosynthetic pigment content. Calculated frequency distributions of pigments were compared with those expected from the theoretical pigment composition. Responses to environmental factors were also analysed. The results revealed that lutein and xanthophyll cycle pigments (VAZ) were highly responsive to the environment, emphasizing the high phenotypic plasticity of VAZ, whereas neoxanthin was very stable. The present meta-analysis supports the existence of relatively narrow limits for pigment ratios and also supports the presence of a pool of free 'unbound' VAZ. Results from this study provide highly reliable ranges of photosynthetic pigment contents as a framework for future research on plant pigments. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Photosynthetic performance in Sphagnum transplanted along a latitudinal nitrogen deposition gradient.

PubMed

Granath, Gustaf; Strengbom, Joachim; Breeuwer, Angela; Heijmans, Monique M P D; Berendse, Frank; Rydin, Håkan

2009-04-01

Increased N deposition in Europe has affected mire ecosystems. However, knowledge on the physiological responses is poor. We measured photosynthetic responses to increasing N deposition in two peatmoss species (Sphagnum balticum and Sphagnum fuscum) from a 3-year, north-south transplant experiment in northern Europe, covering a latitudinal N deposition gradient ranging from 0.28 g N m(-2) year(-1) in the north, to 1.49 g N m(-2) year(-1) in the south. The maximum photosynthetic rate (NP(max)) increased southwards, and was mainly explained by tissue N concentration, secondly by allocation of N to the photosynthesis, and to a lesser degree by modified photosystem II activity (variable fluorescence/maximum fluorescence yield). Although climatic factors may have contributed, these results were most likely attributable to an increase in N deposition southwards. For S. fuscum, photosynthetic rate continued to increase up to a deposition level of 1.49 g N m(-2) year(-1), but for S. balticum it seemed to level out at 1.14 g N m(-2) year(-1). The results for S. balticum suggested that transplants from different origin (with low or intermediate N deposition) respond differently to high N deposition. This indicates that Sphagnum species may be able to adapt or physiologically adjust to high N deposition. Our results also suggest that S. balticum might be more sensitive to N deposition than S. fuscum. Surprisingly, NP(max) was not (S. balticum), or only weakly (S. fuscum) correlated with biomass production, indicating that production is to a great extent is governed by factors other than the photosynthetic capacity.

Ecohydrology of the different photosynthetic pathways and implication for sustainable agriculture

NASA Astrophysics Data System (ADS)

Porporato, A. M.; Bartlett, M. S., Jr.; Hartzell, S. R.

2016-12-01

We use a recently proposed model that can simulate the different photosynthetic pathways coupled to the soil-plant-atmosphere continuum (SPAC) to discuss their ecohydrological implications in relation to water use and plant water stress in both natural and agricultural ecosystems. Built around the classical C3 photosynthesis core model (light reactions and Calvin cycle), the model includes a simple CO2-pump parameterization for C4 plants and a circadian rhythm and carbon storage components for the CAM (Crassulacean Acid Metabolism) plants. Its architecture takes advantage of the interesting modularity in which photosynthesis evolved in geological times to provide a relatively simple but comprehensive framework to explore the advantages and tradeoffs in water energy and carbon fluxes of the three photosynthetic pathways under fluctuating environmental forcing. We calibrate the model with reference to a series of C3,C4 and CAM plants, and discuss the trade-offs in water use and plan productivity and the related impact on hydrologic fluxes and soil biogeochemistry. We also consider some important crop species to analyze the implications of choosing crops with different photosynthetic pathways to improve sustainability of agriculture and irrigation in semiarid systems.

BOREAS TE-9 NSA Photosynthetic Capacity and Foliage Nitrogen Data

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Dang, Qinglai; Margolis, Hank; Coyea, Marie

2000-01-01

The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-9 (Terrestrial Ecology) team collected several data sets related to chemical and photosynthetic properties of leaves in boreal forest tree species. This data set describes the spatial and temporal relationship between foliage nitrogen concentration and photosynthetic capacity in the canopies of black spruce, jack pine, and aspen located within the Northern Study Area (NSA). The data were collected from June to September 1994 and are useful for modeling the vertical distribution of carbon fixation for different forest types in the boreal forest. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Photosynthetic carbon reduction by seagrasses exposed to ultraviolet A radiation

NASA Technical Reports Server (NTRS)

1979-01-01

The seagrasses Halophila engelmannii, Halodule wrightii, and Syringodium filiforme were examined for their intrinsic sensitivity to ultraviolet-A-UV-A and ultraviolet-B-UV-B radiation. The effect of UV-A on photosynthetically active radiation (PAR) was also determined. Ultraviolet-A and ultraviolet-B were studied with emphasis on the greater respective environmental consequence in terms of seagrass distribution and abundance. Results indicate that an intrinsic sensitivity to UV-A alone is apparent only in Halophila, while net photosynthesis in Halodule and Syringodium seems unaffected by the level of UV-A provided. The sensitivity of Halophila to UV-A in the absense of (PAR) indicates that the photosynthetic reaction does not need to be in operation for damage to occur. Other significant results are reported.

The making of a photosynthetic animal

PubMed Central

Rumpho, Mary E.; Pelletreau, Karen N.; Moustafa, Ahmed; Bhattacharya, Debashish

2011-01-01

Symbiotic animals containing green photobionts challenge the common perception that only plants are capable of capturing the sun's rays and converting them into biological energy through photoautotrophic CO2 fixation (photosynthesis). ‘Solar-powered’ sacoglossan molluscs, or sea slugs, have taken this type of symbiotic association one step further by solely harboring the photosynthetic organelle, the plastid (=chloroplast). One such sea slug, Elysia chlorotica, lives as a ‘plant’ when provided with only light and air as a result of acquiring plastids during feeding on its algal prey Vaucheria litorea. The captured plastids (kleptoplasts) are retained intracellularly in cells lining the digestive diverticula of the sea slug, a phenomenon sometimes referred to as kleptoplasty. Photosynthesis by the plastids provides E. chlorotica with energy and fixed carbon for its entire lifespan of ∼10 months. The plastids are not transmitted vertically (i.e. are absent in eggs) and do not undergo division in the sea slug. However, de novo protein synthesis continues, including plastid- and nuclear-encoded plastid-targeted proteins, despite the apparent absence of algal nuclei. Here we discuss current data and provide hypotheses to explain how long-term photosynthetic activity is maintained by the kleptoplasts. This fascinating ‘green animal’ provides a unique model to study the evolution of photosynthesis in a multicellular heterotrophic organism. PMID:21177950

Systemic regulation of leaf anatomical structure, photosynthetic performance, and high-light tolerance in sorghum.

PubMed

Jiang, Chuang-Dao; Wang, Xin; Gao, Hui-Yuan; Shi, Lei; Chow, Wah Soon

2011-03-01

Leaf anatomy of C3 plants is mainly regulated by a systemic irradiance signal. Since the anatomical features of C4 plants are different from that of C3 plants, we investigated whether the systemic irradiance signal regulates leaf anatomical structure and photosynthetic performance in sorghum (Sorghum bicolor), a C4 plant. Compared with growth under ambient conditions (A), no significant changes in anatomical structure were observed in newly developed leaves by shading young leaves alone (YS). Shading mature leaves (MS) or whole plants (S), on the other hand, caused shade-leaf anatomy in newly developed leaves. By contrast, chloroplast ultrastructure in developing leaves depended only on their local light conditions. Functionally, shading young leaves alone had little effect on their net photosynthetic capacity and stomatal conductance, but shading mature leaves or whole plants significantly decreased these two parameters in newly developed leaves. Specifically, the net photosynthetic rate in newly developed leaves exhibited a positive linear correlation with that of mature leaves, as did stomatal conductance. In MS and S treatments, newly developed leaves exhibited severe photoinhibition under high light. By contrast, newly developed leaves in A and YS treatments were more resistant to high light relative to those in MS- and S-treated seedlings. We suggest that (1) leaf anatomical structure, photosynthetic capacity, and high-light tolerance in newly developed sorghum leaves were regulated by a systemic irradiance signal from mature leaves; and (2) chloroplast ultrastructure only weakly influenced the development of photosynthetic capacity and high-light tolerance. The potential significance of the regulation by a systemic irradiance signal is discussed.

Dynamic control of photosynthetic photon flux for lettuce production in CELSS

NASA Technical Reports Server (NTRS)

Chun, C.; Mitchell, C. A.

1996-01-01

A new dynamic control of photosynthetic photon flux (PPF) was tested using lettuce canopies growing in the Minitron II plant-growth/canopy gas-exchange system. Canopy photosynthetic rates (Pn) were measured in real time and fedback for further environment control. Pn can be manipulated by changing PPF, which is a good environmental parameter for dynamic control of crop production in a Controlled Ecological Life-Support Systems CELSS. Decision making that combines empirical mathematical models with rule sets developed from recent experimental data was tested. With comparable yield indices and potential for energy savings, dynamic control strategies will contribute greatly to the sustainability of space-deployed CELSS.

Mechanism and analyses for extracting photosynthetic electrons using exogenous quinones - what makes a good extraction pathway?

PubMed

Longatte, G; Rappaport, F; Wollman, F-A; Guille-Collignon, M; Lemaître, F

2016-08-04

Plants or algae take many benefits from oxygenic photosynthesis by converting solar energy into chemical energy through the synthesis of carbohydrates from carbon dioxide and water. However, the overall yield of this process is rather low (about 4% of the total energy available from sunlight is converted into chemical energy). This is the principal reason why recently many studies have been devoted to extraction of photosynthetic electrons in order to produce a sustainable electric current. Practically, the electron transfer occurs between the photosynthetic organism and an electrode and can be assisted by an exogenous mediator, mainly a quinone. In this regard, we recently reported on a method involving fluorescence measurements to estimate the ability of different quinones to extract photosynthetic electrons from a mutant of Chlamydomonas reinhardtii. In the present work, we used the same kind of methodology to establish a zone diagram for predicting the most suitable experimental conditions to extract photoelectrons from intact algae (quinone concentration and light intensity) as a function of the purpose of the study. This will provide further insights into the extraction mechanism of photosynthetic electrons using exogenous quinones. Indeed fluorescence measurements allowed us to model the capacity of photosynthetic algae to donate electrons to an exogenous quinone by considering a numerical parameter called "open center ratio" which is related to the Photosystem II acceptor redox state. Then, using it as a proxy for investigating the extraction of photosynthetic electrons by means of an exogenous quinone, 2,6-DCBQ, we suggested an extraction mechanism that was globally found consistent with the experimentally extracted parameters.

Leaf-level photosynthetic capacity in lowland Amazonian and high-elevation Andean tropical moist forests of Peru.

PubMed

Bahar, Nur H A; Ishida, F Yoko; Weerasinghe, Lasantha K; Guerrieri, Rossella; O'Sullivan, Odhran S; Bloomfield, Keith J; Asner, Gregory P; Martin, Roberta E; Lloyd, Jon; Malhi, Yadvinder; Phillips, Oliver L; Meir, Patrick; Salinas, Norma; Cosio, Eric G; Domingues, Tomas F; Quesada, Carlos A; Sinca, Felipe; Escudero Vega, Alberto; Zuloaga Ccorimanya, Paola P; Del Aguila-Pasquel, Jhon; Quispe Huaypar, Katherine; Cuba Torres, Israel; Butrón Loayza, Rosalbina; Pelaez Tapia, Yulina; Huaman Ovalle, Judit; Long, Benedict M; Evans, John R; Atkin, Owen K

2017-05-01

We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests (TMFs) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco (V cmax ), and the maximum rate of electron transport (J max )), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area (M a , N a and P a , respectively), and chlorophyll from 210 species at 18 field sites along a 3300-m elevation gradient. Western blots were used to quantify the abundance of the CO 2 -fixing enzyme Rubisco. Area- and N-based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMFs, underpinned by greater investment of N in photosynthesis in high-elevation trees. Soil [P] and leaf P a were key explanatory factors for models of area-based V cmax and J max but did not account for variations in photosynthetic N-use efficiency. At any given N a and P a , the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil- and leaf-P in defining the photosynthetic capacity of TMFs, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N-use efficiency of these critically important forests. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Sustained Photosynthetic Performance of Coffea spp. under Long-Term Enhanced [CO2

PubMed Central

Ramalho, José C.; Rodrigues, Ana P.; Semedo, José N.; Pais, Isabel P.; Martins, Lima D.; Simões-Costa, Maria C.; Leitão, António E.; Fortunato, Ana S.; Batista-Santos, Paula; Palos, Isabel M.; Tomaz, Marcelo A.; Scotti-Campos, Paula; Lidon, Fernando C.; DaMatta, Fábio M.

2013-01-01

Coffee is one of the world’s most traded agricultural products. Modeling studies have predicted that climate change will have a strong impact on the suitability of current cultivation areas, but these studies have not anticipated possible mitigating effects of the elevated atmospheric [CO2] because no information exists for the coffee plant. Potted plants from two genotypes of Coffea arabica and one of C. canephora were grown under controlled conditions of irradiance (800 μmol m-2 s-1), RH (75%) and 380 or 700 μL CO2 L-1 for 1 year, without water, nutrient or root development restrictions. In all genotypes, the high [CO2] treatment promoted opposite trends for stomatal density and size, which decreased and increased, respectively. Regardless of the genotype or the growth [CO2], the net rate of CO2 assimilation increased (34-49%) when measured at 700 than at 380 μL CO2 L-1. This result, together with the almost unchanged stomatal conductance, led to an instantaneous water use efficiency increase. The results also showed a reinforcement of photosynthetic (and respiratory) components, namely thylakoid electron transport and the activities of RuBisCo, ribulose 5-phosphate kinase, malate dehydrogenase and pyruvate kinase, what may have contributed to the enhancements in the maximum rates of electron transport, carboxylation and photosynthetic capacity under elevated [CO2], although these responses were genotype dependent. The photosystem II efficiency, energy driven to photochemical events, non-structural carbohydrates, photosynthetic pigment and membrane permeability did not respond to [CO2] supply. Some alterations in total fatty acid content and the unsaturation level of the chloroplast membranes were noted but, apparently, did not affect photosynthetic functioning. Despite some differences among the genotypes, no clear species-dependent responses to elevated [CO2] were observed. Overall, as no apparent sign of photosynthetic down-regulation was found, our data

Biotechnological Approaches to Enhance Halotolerance and Photosynthetic Efficacy in the Cyanobacterium, Fremyella diplosiphon

NASA Astrophysics Data System (ADS)

Tabatabai, Ben

Growing concerns over dwindling energy supplies linked to nonrenewable fossil fuels have driven profound interest in biofuels as a clean and sustainable alternative. Cyanobacteria are a promising source of third-generation biofuel due to their fast generation time and high net biomass conversion. In this study, the effect of salinity stress on Fremyella diplosiphon, a model organism for studying photosynthetic pathways, was investigated and nanobiotechnological approaches undertaken to enhance its halotolerance and photosynthetic efficacy. Heat-induced mutagenesis resulted in a mutant strain that could survive in 20 g L-1 sodium chloride (NaCl) with no loss in pigmentation. To further enhance F. diplosiphon halotolerance, expression plasmids harboring the hlyB and mdh genes were overexpressed in the wild type resulting in two transformants that thrived in 35 g L-1 NaCl, the average salinity of sea water. In addition, no significant reduction in photosynthetic efficacy was detected in the halotolerant strains relative to the wild type. Total lipid content and fatty acid methyl ester composition of wild type and halotolerant strains were assessed for their potential as a production-scale biofuel agent. Methyl palmitate, the methyl ester of hexodeconoate (C16:0), was found to be most abundant in the wild type and transformants accounting for 60-70% of total FAMEs produced. Efforts to enhance the photosynthetic efficiency of the strains revealed that gold nanoparticle-derived surface plasmon resonance augmented culture growth and pigment accumulation. Cell-nanoparticles interactions were visualized using scanning and transmission electron microscopy. Our findings address two key challenges that cyanobacterial biofuel agents need to overcome: enhanced halotolerance and photosynthetic efficacy to minimize freshwater input and artificial light supply. These innovations have paved the way for an efficient cyanobacterial cultivation system for large-scale production of

Autumn photosynthetic decline and growth cessation in seedlings of white spruce are decoupled under warming and photoperiod manipulations.

PubMed

Stinziano, Joseph R; Way, Danielle A

2017-08-01

Climate warming is expected to increase the seasonal duration of photosynthetic carbon fixation and tree growth in high-latitude forests. However, photoperiod, a crucial cue for seasonality, will remain constant, which may constrain tree responses to warming. We investigated the effects of temperature and photoperiod on weekly changes in photosynthetic capacity, leaf biochemistry and growth in seedlings of a boreal evergreen conifer, white spruce [Picea glauca (Moench) Voss]. Warming delayed autumn declines in photosynthetic capacity, extending the period when seedlings had high carbon uptake. While photoperiod was correlated with photosynthetic capacity, short photoperiods did not constrain the maintenance of high photosynthetic capacity under warming. Rubisco concentration dynamics were affected by temperature but not photoperiod, while leaf pigment concentrations were unaffected by treatments. Respiration rates at 25 °C were stimulated by photoperiod, although respiration at the growth temperatures was increased in warming treatments. Seedling growth was stimulated by increased photoperiod and suppressed by warming. We demonstrate that temperature is a stronger control on the seasonal timing of photosynthetic down-regulation than is photoperiod. Thus, while warming can stimulate carbon uptake in boreal conifers, the extra carbon may be directed towards respiration rather than biomass, potentially limiting carbon sequestration under climate change. © 2017 John Wiley & Sons Ltd.

Determination of phenanthrene bioavailability by using a self-dying reporter bacterium: test with model solids and soil.

PubMed

Shin, Doyun; Nam, Kyoungphile

2012-02-20

The present study was conducted to investigate the performance and feasibility of a self-dying reporter bacterium to visualize and quantify phenanthrene bioavailability in soil. The self-dying reporter bacterium was designed to die on the initiation of phenanthrene biodegradation. The viability of the reporter bacterium was determined by a fluorescence live/dead cell staining method and visualized by confocal laser scanning microscopic observation. Phenanthrene was spiked into four types of model solids and a sandy loam. The bioavailability of phenanthrene to the reporter bacterium was remarkably declined with the hydrophobicity of the model solids: essentially no phenanthrene was biodegraded in the presence of 9-nm pores and about 35.8% of initial phenanthrene was biodegraded without pores. Decrease in bioavailability was not evident in the nonporous hydrophilic bead, but a small decrease was observed in the porous hydrophilic bead at 1000 mg/kg of phenanthrene. The fluorescence intensity was commensurate with the extent of phenanthrene biodegradation by the reporter bacterium at the concentration range from 50 to 500 mg/kg. Such a quantitative relationship was also confirmed with a sandy loam spiked up to 1000 mg/kg of phenanthrene. This reporter bacterium may be a useful means to determine phenanthrene bioavailability in soil. Copyright © 2011 Elsevier B.V. All rights reserved.

Phosphate enhances levan production in the endophytic bacterium Gluconacetobacter diazotrophicus Pal5

PubMed Central

Idogawa, Nao; Amamoto, Ryuta; Murata, Kousaku; Kawai, Shigeyuki

2014-01-01

Gluconacetobacter diazotrophicus is a gram-negative and endophytic nitrogen-fixing bacterium that has several beneficial effects in host plants; thus, utilization of this bacterium as a biofertilizer in agriculture may be possible. G. diazotrophicus synthesizes levan, a D-fructofuranosyl polymer with β-(2→6) linkages, as an exopolysaccharide and the synthesized levan improves the stress tolerance of the bacterium. In this study, we found that phosphate enhances levan production by G. diazotrophicus Pal5, a wild type strain that showed a stronger mucous phenotype on solid medium containing 28 mM phosphate than on solid medium containing 7 mM phosphate. A G. diazotrophicus Pal5 levansucrase disruptant showed only a weak mucous phenotype regardless of the phosphate concentration, indicating that the mucous phenotype observed on 28 mM phosphate medium was caused by levan. To our knowledge, this is the first report of the effect of a high concentration of phosphate on exopolysaccharide production. PMID:24717418

Photosynthetic light reactions--an adjustable hub in basic production and plant immunity signaling.

PubMed

Kangasjärvi, Saijaliisa; Tikkanen, Mikko; Durian, Guido; Aro, Eva-Mari

2014-08-01

Photosynthetic efficiency is a key trait that influences the sustainable utilization of plants for energy and nutrition. By now, extensive research on photosynthetic processes has underscored important structural and functional relationships among photosynthetic thylakoid membrane protein complexes, and their roles in determining the productivity and stress resistance of plants. Photosystem II photoinhibition-repair cycle, for example, has arisen vital in protecting also Photosystem I against light-induced damage. Availability of highly sophisticated genetic, biochemical and biophysical tools has greatly expanded the catalog of components that carry out photoprotective functions in plants. On thylakoid membranes, these components encompass a network of overlapping systems that allow delicate regulation of linear and cyclic electron transfer pathways, balancing of excitation energy distribution between the two photosystems and dissipation of excess light energy in the antenna system as heat. An increasing number of reports indicate that the above mentioned mechanisms also mediate important functions in the regulation of biotic stress responses in plants. Particularly the handling of excitation energy in the light harvesting II antenna complexes appears central to plant immunity signaling. Comprehensive understanding of the underlying mechanisms and regulatory cross-talk, however, still remain elusive. This review highlights the current understanding of components that regulate the function of photosynthetic light reactions and directly or indirectly also modulate disease resistance in higher plants. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Photophysiology of kleptoplasts: photosynthetic use of light by chloroplasts living in animal cells.

PubMed

Serôdio, João; Cruz, Sónia; Cartaxana, Paulo; Calado, Ricardo

2014-04-19

Kleptoplasty is a remarkable type of photosynthetic association, resulting from the maintenance of functional chloroplasts--the 'kleptoplasts'--in the tissues of a non-photosynthetic host. It represents a biologically unique condition for chloroplast and photosynthesis functioning, occurring in different phylogenetic lineages, namely dinoflagellates, ciliates, foraminiferans and, most interestingly, a single taxon of metazoans, the sacoglossan sea slugs. In the case of sea slugs, chloroplasts from macroalgae are often maintained as intracellular organelles in cells of these marine gastropods, structurally intact and photosynthetically competent for extended periods of time. Kleptoplasty has long attracted interest owing to the longevity of functional kleptoplasts in the absence of the original algal nucleus and the limited number of proteins encoded by the chloroplast genome. This review updates the state-of-the-art on kleptoplast photophysiology, focusing on the comparative analysis of the responses to light of the chloroplasts when in their original, macroalgal cells, and when sequestered in animal cells and functioning as kleptoplasts. It covers fundamental but ecologically relevant aspects of kleptoplast light responses, such as the occurrence of photoacclimation in hospite, operation of photoprotective processes and susceptibility to photoinhibition. Emphasis is given to host-mediated processes unique to kleptoplastic associations, reviewing current hypotheses on behavioural photoprotection and host-mediated enhancement of photosynthetic performance, and identifying current gaps in sacoglossan kleptoplast photophysiology research.

Identification of large variation in the photosynthetic induction response among 37 soybean genotypes that is not correlated with steady-state photosynthetic capacity

USDA-ARS?s Scientific Manuscript database

Irradiance continuously fluctuates during the day in the field, potentially resulting in photosynthetic induction of leaves as they transition from low to high light. The speed of the induction response affects the cumulative carbon gain of the plants and could impact growth and yield. The photosynt...

Continuous cultivation of photosynthetic microorganisms: Approaches, applications and future trends.

PubMed

Fernandes, Bruno D; Mota, Andre; Teixeira, Jose A; Vicente, Antonio A

2015-11-01

The possibility of using photosynthetic microorganisms, such as cyanobacteria and microalgae, for converting light and carbon dioxide into valuable biochemical products has raised the need for new cost-efficient processes ensuring a constant product quality. Food, feed, biofuels, cosmetics and pharmaceutics are among the sectors that can profit from the application of photosynthetic microorganisms. Biomass growth in a photobioreactor is a complex process influenced by multiple parameters, such as photosynthetic light capture and attenuation, nutrient uptake, photobioreactor hydrodynamics and gas-liquid mass transfer. In order to optimize productivity while keeping a standard product quality, a permanent control of the main cultivation parameters is necessary, where the continuous cultivation has shown to be the best option. However it is of utmost importance to recognize the singularity of continuous cultivation of cyanobacteria and microalgae due to their dependence on light availability and intensity. In this sense, this review provides comprehensive information on recent breakthroughs and possible future trends regarding technological and process improvements in continuous cultivation systems of microalgae and cyanobacteria, that will directly affect cost-effectiveness and product quality standardization. An overview of the various applications, techniques and equipment (with special emphasis on photobioreactors) in continuous cultivation of microalgae and cyanobacteria are presented. Additionally, mathematical modeling, feasibility, economics as well as the applicability of continuous cultivation into large-scale operation, are discussed. Copyright © 2015 Elsevier Inc. All rights reserved.

Highly oriented photosynthetic reaction centers generate a proton gradient in synthetic protocells

PubMed Central

Altamura, Emiliano; Milano, Francesco; Tangorra, Roberto R.; Trotta, Massimo; Omar, Omar Hassan; Stano, Pasquale

2017-01-01

Photosynthesis is responsible for the photochemical conversion of light into the chemical energy that fuels the planet Earth. The photochemical core of this process in all photosynthetic organisms is a transmembrane protein called the reaction center. In purple photosynthetic bacteria a simple version of this photoenzyme catalyzes the reduction of a quinone molecule, accompanied by the uptake of two protons from the cytoplasm. This results in the establishment of a proton concentration gradient across the lipid membrane, which can be ultimately harnessed to synthesize ATP. Herein we show that synthetic protocells, based on giant lipid vesicles embedding an oriented population of reaction centers, are capable of generating a photoinduced proton gradient across the membrane. Under continuous illumination, the protocells generate a gradient of 0.061 pH units per min, equivalent to a proton motive force of 3.6 mV⋅min−1. Remarkably, the facile reconstitution of the photosynthetic reaction center in the artificial lipid membrane, obtained by the droplet transfer method, paves the way for the construction of novel and more functional protocells for synthetic biology. PMID:28320948

Photosynthetic performance of a helical tubular photobioreactor incorporating the cyanobacterium Spirulina platensis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Yoshitomo; Hall, D.O.; Nouee, J. De La

1995-07-20

The photosynthetic performance of a helical tubular photobioreactor (``Biocoil``), incorporating the filamentous cyanobacterium Spirulina platensis, was investigated. The photobioreactor was constructed in a cylindrical shape with a 0.25-m{sup 2} basal area and a photostage comprising 60 m of transparent PVC tubing of 1.6-cm inner diameter. The inner surface of the cylinder was illuminated with cool white fluorescent lamps; the energy input of photosynthetically active radiation into the photobioreactor was 2,920 kJ per day. An air-lift system incorporating 4% CO{sub 2} was used to circulate the growth medium in the tubing. The maximum productivity achieved in batch culture was 7.18 gmore » dry biomass per day which corresponded to a photosynthetic (PAR) efficiency of 5.45%. The CO{sub 2} was efficiently removed from the gaseous stream; monitoring the CO{sub 2} in the outlet and inlet gas streams showed a 70% removal of CO{sub 2} from the inlet gas over an 8-h period with almost maximum growth rate.« less

Artificial Photosynthetic Reaction Center Exhibiting Acid-Responsive Regulation of Photoinduced Charge Separation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pahk, Ian; Kodis, Gerdenis; Fleming, Graham R.

Charge separation (CS) is the primary light-driven reaction in photosynthesis whereas onphotochemical quenching (NPQ) is a photoprotective regulatory mechanism employed by many photosynthetic organisms to dynamically modulate energy flow within the photosynthetic apparatus in response to fluctuating light conditions. Activated by decreases in lumen pH produced during periods of high photon flux, NPQ induces rapid thermal dissipation of excess excitation energy. As a result, the rate of CS decreases, thereby limiting the accumulation of potentially deleterious reactive intermediates and byproducts. In this article, a molecular triad that functionally mimics the effects of NPQ associated with an artificial photosynthetic reaction centermore » is described. Steady-state absorption and emission, time-resolved fluorescence, and transient absorption spectroscopies have been used to demonstrate a 1 order of magnitude reduction in the CS quantum yield via reversible protonation of an excited-state-quenching molecular switch moiety. As in the natural system, the populations of unquenched and quenched states and therefore the overall yields of CS were found to be dependent on acid concentration.« less

LHCII organization and thylakoid lipids affect the sensitivity of the photosynthetic apparatus to high-light treatment.

PubMed

Dankov, Kolyo G; Dobrikova, Anelia G; Ughy, Bettina; Bogos, Balázs; Gombos, Zoltan; Apostolova, Emilia L

2011-06-01

Pulse-amplitude-modulated (PAM) chlorophyll fluorescence and photosynthetic oxygen evolution were used to investigate the role of the different amount and organization of light-harvesting complexes of photosystem II (LHCII) in four pea species on the susceptibility of the photosynthetic apparatus to high-light treatment. In this work we analyzed the thylakoid membrane lipid composition of the studied pea plants. A relationship between the structural organization of LHCII proteins, the amount of the main lipid classes and the sensitivity of the photosynthetic apparatus to high-light treatment was found. The results reveal that the photosynthetic apparatus, enriched in oligomeric forms of LHCII concomitant with decreased amount of anionic lipids and increased content of the monogalactosyldiacylglycerol (MGDG), is less sensitive to high light. Our data also suggest that the degree of LHCII oligomerization, as well as the lipid composition do not influence the degree of recovery of the PSII photochemistry after excess light exposure. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Decrease in the Photosynthetic Performance of Temperate Grassland Species Does Not Lead to a Decline in the Gross Primary Production of the Ecosystem

PubMed Central

Digrado, Anthony; de la Motte, Louis G.; Bachy, Aurélie; Mozaffar, Ahsan; Schoon, Niels; Bussotti, Filippo; Amelynck, Crist; Dalcq, Anne-Catherine; Fauconnier, Marie-Laure; Aubinet, Marc; Heinesch, Bernard; du Jardin, Patrick; Delaplace, Pierre

2018-01-01

Plants, under stressful conditions, can proceed to photosynthetic adjustments in order to acclimatize and alleviate the detrimental impacts on the photosynthetic apparatus. However, it is currently unclear how adjustment of photosynthetic processes under environmental constraints by plants influences CO2 gas exchange at the ecosystem-scale. Over a 2-year period, photosynthetic performance of a temperate grassland ecosystem was characterized by conducting frequent chlorophyll fluorescence (ChlF) measurements on three primary grassland species (Lolium perenne L., Taraxacum sp., and Trifolium repens L.). Ecosystem photosynthetic performance was estimated from measurements performed on the three dominant grassland species weighed based on their relative abundance. In addition, monitoring CO2 fluxes was performed by eddy covariance. The highest decrease in photosynthetic performance was detected in summer, when environmental constraints were combined. Dicot species (Taraxacum sp. and T. repens) presented the strongest capacity to up-regulate PSI and exhibited the highest electron transport efficiency under stressful environmental conditions compared with L. perenne. The decline in ecosystem photosynthetic performance did not lead to a reduction in gross primary productivity, likely because increased light energy was available under these conditions. The carbon amounts fixed at light saturation were not influenced by alterations in photosynthetic processes, suggesting photosynthesis was not impaired. Decreased photosynthetic performance was associated with high respiration flux, but both were influenced by temperature. Our study revealed variation in photosynthetic performance of a grassland ecosystem responded to environmental constraints, but alterations in photosynthetic processes appeared to exhibit a negligible influence on ecosystem CO2 fluxes. PMID:29459875

Bio-inspired photo-electronic material based on photosynthetic proteins

NASA Astrophysics Data System (ADS)

Lebedev, Nikolai; Trammell, Scott A.; Tsoi, Stanislav; Spano, Anthony; Kim, Jin Ho; Xu, Jimmy; Twigg, Mark E.; Schnur, Joel M.

2009-08-01

The construction of efficient light energy converting (photovoltaic and photo-electronic) devices is a current and great challenge in science and technology and one that will have important economic consequences. Several innovative nanoelectronic materials were proposed to achieve this goal, semiconductor quantum dots, metallic nanowires and carbon nanotubes (CNT) are among them. As a charge separating unit for light energy conversion, we propose the utilization of the most advanced photoelectronic material developed by nature, photosynthetic reaction center proteins. As a first step in this direction, we constructed a novel bioinorganic nanophotoelectronic material with photoactive photosynthetic reaction center (RC) proteins encapsulated inside a multiwall CNT arrayed electrode. The material consists of photosynthetic RC-cytochrome complexes acting as charge separating units bound to the inner walls of a CNT electrode and ubiquinone-10 (Q2) serving as a soluble electron-transfer mediator to the counter electrode. The proteins were immobilized inside carbon nanotubes by a Ni(NTA)-alkane-pyrene linker, forming a self-assembled monolayer (SAM) on the surface of inner CNT walls and allowing for unidirectional protein orientation. The material demonstrates an enhanced photoinduced electron transfer rate and shows substantial improvement in photocurrent density compared to that obtained with the same proteins when immobilized on planar graphite (HOPG) electrode. The results suggest that protein encapsulation in precisely organized arrayed tubular electrode architecture can considerably improve the performance of photovoltaic, photoelectronic, or biofuel cell devices. They demonstrate the potential for substantial advantages of precisely organized nano electrode tubular arrayed architecture for variety biotechnological applications.

Purple non-sulfur photosynthetic bacteria monitor environmental stresses.

PubMed

Kis, Mariann; Sipka, Gábor; Asztalos, Emese; Rázga, Zsolt; Maróti, Péter

2015-10-01

Heavy metal ion pollution and oxygen deficiency are major environmental risks for microorganisms in aqueous habitat. The potential of purple non-sulfur photosynthetic bacteria for biomonitoring and bioremediation was assessed by investigating the photosynthetic capacity in heavy metal contaminated environments. Cultures of bacterial strains Rhodobacter sphaeroides, Rhodospirillum rubrum and Rubrivivax gelatinosus were treated with heavy metal ions in micromolar (Hg(2+)), submillimolar (Cr(6+)) and millimolar (Pb(2+)) concentration ranges. Functional assays (flash-induced absorption changes and bacteriochlorophyll fluorescence induction) and electron micrographs were taken to specify the harmful effects of pollution and to correlate to morphological changes of the membrane. The bacterial strains and functional tests showed differentiated responses to environmental stresses, revealing that diverse mechanisms of tolerance and/or resistance are involved. The microorganisms were vulnerable to the prompt effect of Pb(2+), showed weak tolerance to Hg(2+) and proved to be tolerant to Cr(6+). The reaction center controlled electron transfer in Rvx. gelatinosus demonstrated the highest degree of resistance against heavy metal exposure. Copyright © 2015 Elsevier B.V. All rights reserved.

Role of interference in the photosynthetic heat engine

NASA Astrophysics Data System (ADS)

Xu, Y. Y.; Liu, J.

2014-11-01

The observation of quantum coherence in pigment-protein complexes has attracted considerable interest. One such endeavor entails applying a quantum heat engine to model the photosynthetic reaction center, but the definition of work used is inconsistent with that defined in quantum thermodynamics. Using the definition of work proposed in Weimer et al. [Europhys. Lett. 83, 30008 (2008), 10.1209/0295-5075/83/30008], we investigated two proposals for enhancing the performance of the photosynthetic reaction center. In proposal A, which is similar to that in Dorfman et al. [Proc. Natl. Acad. Sci. USA 110, 2746 (2013), 10.1073/pnas.1212666110], we found that the power and current-voltage characteristic of the heat engine can be increased by Fano interference but the efficiency cannot. In proposal B, which is similar to that in Creatore et al. [Phys. Rev. Lett. 111, 253601 (2013), 10.1103/PhysRevLett.111.253601], we found that the mechanism of strengthening the performance of the heat engine is invalid; i.e., the dipole-dipole interaction between two electron donors could not increase the power, efficiency, or current-voltage characteristic.

Mycorrhiza Symbiosis Increases the Surface for Sunlight Capture in Medicago truncatula for Better Photosynthetic Production

PubMed Central

Adolfsson, Lisa; Keresztes, Áron; Uddling, Johan; Schoefs, Benoît; Spetea, Cornelia

2015-01-01

Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with Pi fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with Pi fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased Pi supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and Pi-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by Pi fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and Pi-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area. PMID:25615871

Mycorrhiza symbiosis increases the surface for sunlight capture in Medicago truncatula for better photosynthetic production.

PubMed

Adolfsson, Lisa; Solymosi, Katalin; Andersson, Mats X; Keresztes, Áron; Uddling, Johan; Schoefs, Benoît; Spetea, Cornelia

2015-01-01

Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with P(i) fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with P(i) fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased P(i) supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and P(i)-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by P(i) fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and P(i)-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area.

Warming delays autumn declines in photosynthetic capacity in a boreal conifer, Norway spruce (Picea abies).

PubMed

Stinziano, Joseph R; Hüner, Norman P A; Way, Danielle A

2015-12-01

Climate change, via warmer springs and autumns, may lengthen the carbon uptake period of boreal tree species, increasing the potential for carbon sequestration in boreal forests, which could help slow climate change. However, if other seasonal cues such as photoperiod dictate when photosynthetic capacity declines, warmer autumn temperatures may have little effect on when carbon uptake capacity decreases in these species. We investigated whether autumn warming would delay photosynthetic decline in Norway spruce (Picea abies (L.) H. Karst.) by growing seedlings under declining weekly photoperiods and weekly temperatures either at ambient temperature or a warming treatment 4 °C above ambient. Photosynthetic capacity was relatively constant in both treatments when weekly temperatures were >8 °C, but declined rapidly at lower temperatures, leading to a delay in the autumn decline in photosynthetic capacity in the warming treatment. The decline in photosynthetic capacity was not related to changes in leaf nitrogen or chlorophyll concentrations, but was correlated with a decrease in the apparent fraction of leaf nitrogen invested in Rubisco, implicating a shift in nitrogen allocation away from the Calvin cycle at low autumn growing temperatures. Our data suggest that as the climate warms, the period of net carbon uptake will be extended in the autumn for boreal forests dominated by Norway spruce, which could increase total carbon uptake in these forests. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Importance of Fluctuations in Light on Plant Photosynthetic Acclimation1[CC-BY

PubMed Central

2017-01-01

The acclimation of plants to light has been studied extensively, yet little is known about the effect of dynamic fluctuations in light on plant phenotype and acclimatory responses. We mimicked natural fluctuations in light over a diurnal period to examine the effect on the photosynthetic processes and growth of Arabidopsis (Arabidopsis thaliana). High and low light intensities, delivered via a realistic dynamic fluctuating or square wave pattern, were used to grow and assess plants. Plants subjected to square wave light had thicker leaves and greater photosynthetic capacity compared with fluctuating light-grown plants. This, together with elevated levels of proteins associated with electron transport, indicates greater investment in leaf structural components and photosynthetic processes. In contrast, plants grown under fluctuating light had thinner leaves, lower leaf light absorption, but maintained similar photosynthetic rates per unit leaf area to square wave-grown plants. Despite high light use efficiency, plants grown under fluctuating light had a slow growth rate early in development, likely due to the fact that plants grown under fluctuating conditions were not able to fully utilize the light energy absorbed for carbon fixation. Diurnal leaf-level measurements revealed a negative feedback control of photosynthesis, resulting in a decrease in total diurnal carbon assimilated of at least 20%. These findings highlight that growing plants under square wave growth conditions ultimately fails to predict plant performance under realistic light regimes and stress the importance of considering fluctuations in incident light in future experiments that aim to infer plant productivity under natural conditions in the field. PMID:28184008

Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux

NASA Technical Reports Server (NTRS)

Barnes, C.; Tibbitts, T.; Sager, J.; Deitzer, G.; Bubenheim, D.; Koerner, G.; Bugbee, B.; Knott, W. M. (Principal Investigator)

1993-01-01

Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

Evidence for compensatory photosynthetic and yield response of soybeans to aphid herbivory

DOE PAGES

Kucharik, Christopher J.; Mork, Amelia C.; Meehan, Timothy D.; ...

2016-04-13

The soybean aphid, Aphis glycines Matsumura, an exotic species in North America that has been detected in 21 U.S. states and Canada, is a major pest for soybean that can reduce maximum photosynthetic capacity and yields. Our existing knowledge is based on relatively few studies that do not span a wide variety of environmental conditions, and often focus on relatively high and damaging population pressure. We examined the effects of varied populations and duration of soybean aphids on soybean photosynthetic rates and yield in two experiments. In a 2011 field study, we found that plants with low cumulative aphid daysmore » (CAD, less than 2,300) had higher yields than plants not experiencing significant aphid pressure, suggesting a compensatory growth response to low aphid pressure. This response did not hold at higher CAD, and yields declined. In a 2013 controlled-environment greenhouse study, soybean plants were well-watered and fertilized with nitrogen (N), and aphid populations were manipulated to reach moderate to high levels (8,000–50,000 CAD). Plants tolerated these population levels when aphids were introduced during the vegetative or reproductive phenological stages of the plant, showing no significant reduction in yield. Leaf N concentration and CAD were positively and significantly correlated with increasing ambient photosynthetic rates. Our findings suggest that, given the right environmental conditions, modern soybean plants can withstand higher aphid pressure than previously assumed. Moreover, soybean plants also responded positively through a compensatory photosynthetic effect to moderate population pressure, contributing to stable or increased yield.« less

Ultra-broadband 2D electronic spectroscopy of carotenoid-bacteriochlorophyll interactions in the LH1 complex of a purple bacterium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maiuri, Margherita; Department of Chemistry, Princeton University, Washington Road, Princeton, New Jersey 08544; Réhault, Julien

We investigate the excitation energy transfer (EET) pathways in the photosynthetic light harvesting 1 (LH1) complex of purple bacterium Rhodospirillum rubrum with ultra-broadband two-dimensional electronic spectroscopy (2DES). We employ a 2DES apparatus in the partially collinear geometry, using a passive birefringent interferometer to generate the phase-locked pump pulse pair. This scheme easily lends itself to two-color operation, by coupling a sub-10 fs visible pulse with a sub-15-fs near-infrared pulse. This unique pulse combination allows us to simultaneously track with extremely high temporal resolution both the dynamics of the photoexcited carotenoid spirilloxanthin (Spx) in the visible range and the EET betweenmore » the Spx and the B890 bacterio-chlorophyll (BChl), whose Q{sub x} and Q{sub y} transitions peak at 585 and 881 nm, respectively, in the near-infrared. Global analysis of the one-color and two-color 2DES maps unravels different relaxation mechanisms in the LH1 complex: (i) the initial events of the internal conversion process within the Spx, (ii) the parallel EET from the first bright state S{sub 2} of the Spx towards the Q{sub x} state of the B890, and (iii) the internal conversion from Q{sub x} to Q{sub y} within the B890.« less

Orientations of Iron-Sulfur Clusters FA and FB in the Homodimeric Type-I Photosynthetic Reaction Center of Heliobacterium modesticaldum.

PubMed

Kondo, Toru; Matsuoka, Masahiro; Azai, Chihiro; Itoh, Shigeru; Oh-Oka, Hirozo

2016-05-12

Orientations of the FA and FB iron-sulfur (FeS) clusters in a structure-unknown type-I homodimeric heriobacterial reaction center (hRC) were studied in oriented membranes of the thermophilic anaerobic photosynthetic bacterium Heliobacterium modesticaldum by electron paramagnetic resonance (EPR), and compared with those in heterodimeric photosystem I (PS I). The Rieske-type FeS center in the cytochrome b/c complex showed a well-oriented EPR signal. Illumination at 14 K induced an FB(-) signal with g-axes of gz = 2.066, gy = 1.937, and gx = 1.890, tilted at angles of 60°, 60°, and 45°, respectively, with respect to the membrane normal. Chemical reduction with dithionite produced an additional signal of FA(-), which magnetically interacted with FB(-), with gz = 2.046, gy = 1.942, and gx = 1.911 at 30°, 60°, and 90°, respectively. The angles and redox properties of FA(-) and FB(-) in hRC resemble those of FB(-) and FA(-), respectively, in PS I. Therefore, FA and FB in hRC, named after their g-value similarities, seem to be located like FB and FA, not like FA and FB, respectively, in PS I. The reducing side of hRC could resemble those in PS I, if the names of FA and FB are interchanged with each other.

Nitrate and Ammonium Induced Photosynthetic Suppression in N-Limited Selenastrum minutum.

PubMed

Elrifi, I R; Turpin, D H

1986-05-01

Nitrate-limited chemostat cultures of Selenastrum minutum Naeg. Collins (Chlorophyta) were used to determine the effects of nitrogen addition on photosynthesis, dark respiration, and dark carbon fixation. Addition of NO(3) (-) or NH(4) (+) induced a transient suppression of photosynthetic carbon fixation (70 and 40% respectively). Intracellular ribulose bisphosphate levels decreased during suppression and recovered in parallel with photosynthesis. Photosynthetic oxygen evolution was decreased by N-pulsing under saturating light (650 microeinsteins per square meter per second). Under subsaturating light intensities (<165 microeinsteins per square meter per second) NH(4) (+) addition resulted in O(2) consumption in the light which was alleviated by the presence of the tricarboxylic acid cycle inhibitor fluoroacetate. Addition of NO(3) (-) or NH(4) (+) resulted in a large stimulation of dark respiration (67 and 129%, respectively) and dark carbon fixation (360 and 2080%, respectively). The duration of N-induced perturbations was dependent on the concentration of added N. Inhibition of glutamine 2-oxoglutarate aminotransferase by azaserine alleviated all these effects. It is proposed that suppression of photosynthetic carbon fixation in response to N pulsing was the result of a competition for metabolites between the Calvin cycle and nitrogen assimilation. Carbon skeletons required for nitrogen assimilation would be derived from tricarboxylic acid cycle intermediates. To maintain tricarboxylic acid cycle activity triose phosphates would be exported from the chloroplast. This would decrease the rate of ribulose bisphosphate regeneration and consequently decrease net photosynthetic carbon accumulation. Stoichiometric calculations indicate that the Calvin cycle is one source of triose phosphates for N assimilation; however, during transient N resupply the major demand for triose phosphates must be met by starch or sucrose breakdown. The effects of N-pulsing on O(2

Plastid genome structure and loss of photosynthetic ability in the parasitic genus Cuscuta.

PubMed

Revill, Meredith J W; Stanley, Susan; Hibberd, Julian M

2005-09-01

The genus Cuscuta (dodder) is composed of parasitic plants, some species of which appear to be losing the ability to photosynthesize. A molecular phylogeny was constructed using 15 species of Cuscuta in order to assess whether changes in photosynthetic ability and alterations in structure of the plastid genome relate to phylogenetic position within the genus. The molecular phylogeny provides evidence for four major clades within Cuscuta. Although DNA blot analysis showed that Cuscuta species have smaller plastid genomes than tobacco, and that plastome size varied significantly even within one Cuscuta clade, dot blot analysis indicated that the dodders possess homologous sequence to 101 genes from the tobacco plastome. Evidence is provided for significant rates of DNA transfer from plastid to nucleus in Cuscuta. Size and structure of Cuscuta plastid genomes, as well as photosynthetic ability, appear to vary independently of position within the phylogeny, thus supporting the hypothesis that within Cuscuta photosynthetic ability and organization of the plastid genome are changing in an unco-ordinated manner.

[Diversity analysis of desulfuration bacterium from the oxidation ditch of city sewage treatment plant with SO2 gas].

PubMed

Huang, Bing; Zhang, Shi-Ling; Zhang, Jiang-Hong; Ao, Yong; Shi, Zhe

2011-07-01

A group of removing SO2 bacterium was obtained from the oxidation ditch of city sewage treatment plant by inductive domestication over 6 d with low concentration SO2 gas, and they have an ability with biodegradation rate of 888 mg x (L x h)(-1) and a degradation efficiency of 85% during 1.5 h for SO2 dissolved in water with their synergy. The clone library and two phylogenetic trees of the removing SO2 bacterium communities were obtained based on 16S rRNA DNA comparison by DNA extraction of the sample and in situ polymerase chain reaction (PCR). The phylogenetic analysis showed that 8 dominant desulfuration bacterium occupy about 69% of all removing SO2 bacterium, and some of them have a kindred with discovered desulfuration bacterium but not homogeneity, and there are four belong to alpha-Proteobacteria, another four belong to beta-Proteobacteria in them. The gene information about 16S rRNA sequence of the dominant desulfuration bacteria and domestication method provide a basic of looking for or domesticating removing SO2 bacterium for development microbial desulfurization technology of contained SO2 tail gas.

Elevated CO2 differentially affects photosynthetic induction response in two Populus species with different stomatal behavior.

PubMed

Tomimatsu, Hajime; Tang, Yanhong

2012-08-01

To understand dynamic photosynthetic characteristics in response to fluctuating light under a high CO(2) environment, we examined photosynthetic induction in two poplar genotypes from two species, Populus koreana 9 trichocarpa cv. Peace and Populus euramericana cv. I-55, respectively. Stomata of cv. Peace barely respond to changes in photosynthetic photon flux density (PFD), whereas those of cv. I-55 show a normal response to variations in PFD at ambient CO(2). The plants were grown under three CO2 regimes (380, 700, and 1,020 μmol CO(2) mol(-1) in air) for approximately 2 months. CO2 gas exchange was measured in situ in the three CO2 regimes under a sudden PFD increase from 20 to 800 μmol m(-2) s(-1). In both genotypes, plants grown under higher CO(2) conditions had a higher photosynthetic induction state, shorter induction time, and reduced induction limitation to photosynthetic carbon gain. Plants of cv. I-55 showed a much larger increase in induction state and decrease in induction time under high CO(2) regimes than did plants of cv. Peace. These showed that, throughout the whole induction process, genotype cv. I-55 had a much smaller reduction of leaf carbon gain under the two high CO(2) regimes than under the ambient CO(2) regime, while the high CO(2) effect was smaller in genotype cv. Peace. The results suggest that a high CO(2) environment can reduce both biochemical and stomatal limitations of leaf carbon gain during the photosynthetic induction process, and that a rapid stomatal response can further enhance the high CO(2) effect.

Remote sensing of vegetation canopy photosynthetic and stomatal conductance efficiencies

NASA Technical Reports Server (NTRS)

Myneni, R. B.; Ganapol, B. D.; Asrar, G.

1992-01-01

The problem of remote sensing the canopy photosynthetic and stomatal conductance efficiencies is investigated with the aid of one- and three-dimensional radiative transfer methods coupled to a semi-empirical mechanistic model of leaf photosynthesis and stomatal conductance. Desertlike vegetation is modeled as clumps of leaves randomly distributed on a bright dry soil with partial ground cover. Normalized difference vegetation index (NDVI), canopy photosynthetic (Ep), and stomatal efficiencies (Es) are calculated for various geometrical, optical, and illumination conditions. The contribution of various radiative fluxes to estimates of Ep is evaluated and the magnitude of errors in bulk canopy formulation of problem parameters are quantified. The nature and sensitivity of the relationship between Ep and Es to NDVI is investigated, and an algorithm is proposed for use in operational remote sensing.

Characterization of a bacterium of the genus Azospirillum from cellulolytic nitrogen-fixing mixed cultures.

PubMed

Wong, P P; Stenberg, N E; Edgar, L

1980-03-01

A bacterium with the taxonomic characteristics of the genus Azospirillum was isolated from celluloytic N2-fixing mixed cultures. Its characteristics fit the descriptions of both Azopirillum lipoferum (Beijerinck) comb. nov. and Azospirillum brasilense sp. nov. It may be a variant strain of A. lipoferum. In mixed cultures with cellulolytic organisms, the bacterium grew and fixed N2 with cellelose as a sole source of energy and carbon. The mixed cultures used cellulose from leaves of wheat (Triticum aestivum L.), corn (Zea mays L.), and big bluestem grass (Andropogon gerardii Vitm). Microaerophilic N2-fixing bacteria of the genus Azospirillum, such as the bacterium we isolated, may be important contributors of fixed N2 in soil with partial anaerobiosis and cellulose decomposition.

Height-related changes in leaf photosynthetic traits in diverse Bornean tropical rain forest trees.

PubMed

Kenzo, Tanaka; Inoue, Yuta; Yoshimura, Mitsunori; Yamashita, Megumi; Tanaka-Oda, Ayumi; Ichie, Tomoaki

2015-01-01

Knowledge of variations in morphophysiological leaf traits with forest height is essential for quantifying carbon and water fluxes from forest ecosystems. Here, we examined changes in leaf traits with forest height in diverse tree species and their role in environmental acclimation in a tropical rain forest in Borneo that does not experience dry spells. Height-related changes in leaf physiological and morphological traits [e.g., maximum photosynthetic rate (Amax), stomatal conductance (gs), dark respiration rate (Rd), carbon isotope ratio (δ(13)C), nitrogen (N) content, and leaf mass per area (LMA)] from understory to emergent trees were investigated in 104 species in 29 families. We found that many leaf area-based physiological traits (e.g., A(max-area), Rd, gs), N, δ(13)C, and LMA increased linearly with tree height, while leaf mass-based physiological traits (e.g., A(max-mass)) only increased slightly. These patterns differed from other biomes such as temperate and tropical dry forests, where trees usually show decreased photosynthetic capacity (e.g., A(max-area), A(max-mass)) with height. Increases in photosynthetic capacity, LMA, and δ(13)C are favored under bright and dry upper canopy conditions with higher photosynthetic productivity and drought tolerance, whereas lower R d and LMA may improve shade tolerance in lower canopy trees. Rapid recovery of leaf midday water potential to theoretical gravity potential during the night supports the idea that the majority of trees do not suffer from strong drought stress. Overall, leaf area-based photosynthetic traits were associated with tree height and the degree of leaf drought stress, even in diverse tropical rain forest trees.

Effects of gold nanoparticles on the photophysical and photosynthetic parameters of leaves and chloroplasts.

PubMed

Torres, Rocio; Diz, Virginia E; Lagorio, M Gabriela

2018-04-18

Effects of gold nanoparticles (average diameter: 10-14 nm) on leaves and chloroplasts have been studied. Gold nanoparticles (AuNPs) quenched significantly chlorophyll fluorescence when introduced both in intact leaves and isolated chloroplasts. Additionally, the fluorescence spectra corrected for light re-absorption processes showed a net decrease in the fluorescence ratio calculated as the quotient between the maximum fluorescence at 680 and 735 nm. This fact gave evidence for a reduction in the fluorescence emission of the PSII relative to that of the PSI. Strikingly, the photosynthetic parameters derived from the analysis of the slow phase of Kautsky's kinetics, the rate of oxygen evolution and the rate of photo-reduction of 2,6-dichlorophenolindophenol were increased in the presence of AuNPs indicating an apparent greater photosynthetic capacity. The observed results were consistent with an electron transfer process from the excited PSII, which was thermodynamically possible, and which competed with both the electron transport process that initiated photosynthesis and the deactivation of the excited PSII by fluorescence emission. Additionally, it is here explained, in terms of a completely rational kinetic scheme and their corresponding algebraic expressions, why the photosynthetic parameters and the variable and non-variable fluorescence of chlorophyll are modified in a photosynthetic tissue containing gold nanoparticles.

Acclimatization of Photosynthetic Apparatus of Tor Grass (Brachypodium pinnatum) during Expansion

PubMed Central

Bąba, Wojciech; Kalaji, Hazem M.; Kompała-Bąba, Agnieszka; Goltsev, Vasilij

2016-01-01

The aim of this study was to understand the acclimatization mechanisms of photosynthetic apparatus in Brachypodium pinnatum (L.) P. Beauv grass during its expansion. Twelve populations differentiated by age: young (30–50 years old), intermediate age (ca. 100 y) and old (>300 y) were studied. It was confirmed that the decrease of the number of genotypes as a result of environmental stress and competition were reflected in changes in chlorophyll fluorescence (ChlF) parameters. The old stands were dominated by a few genotypes which seem to be the best acclimatized to the self-shading/competition by lowering their photosynthetic performance during light-phase of photosynthesis. On the other hand, the 'high-speed' photosynthetic rate observed in the young populations can be seen as acclimatization to very adverse conditions. Our results clearly confirm that ChlF is a powerful method of inferring physiological mechanisms of the expansion of tor grass. The Principal Component and Redundancy Analyses, followed with k-means classification, allowed to find the differentiation of groups of distinct ChlF parameters and enabled us to relate them to changes in genotypic diversity of populations. We conclude that the plastic morphological and physiological response to changeable habitat light conditions with its optimum in half-shade refers to its forest-steppe origin. PMID:27275605

Acclimatization of Photosynthetic Apparatus of Tor Grass (Brachypodium pinnatum) during Expansion.

PubMed

Bąba, Wojciech; Kalaji, Hazem M; Kompała-Bąba, Agnieszka; Goltsev, Vasilij

2016-01-01

The aim of this study was to understand the acclimatization mechanisms of photosynthetic apparatus in Brachypodium pinnatum (L.) P. Beauv grass during its expansion. Twelve populations differentiated by age: young (30-50 years old), intermediate age (ca. 100 y) and old (>300 y) were studied. It was confirmed that the decrease of the number of genotypes as a result of environmental stress and competition were reflected in changes in chlorophyll fluorescence (ChlF) parameters. The old stands were dominated by a few genotypes which seem to be the best acclimatized to the self-shading/competition by lowering their photosynthetic performance during light-phase of photosynthesis. On the other hand, the 'high-speed' photosynthetic rate observed in the young populations can be seen as acclimatization to very adverse conditions. Our results clearly confirm that ChlF is a powerful method of inferring physiological mechanisms of the expansion of tor grass. The Principal Component and Redundancy Analyses, followed with k-means classification, allowed to find the differentiation of groups of distinct ChlF parameters and enabled us to relate them to changes in genotypic diversity of populations. We conclude that the plastic morphological and physiological response to changeable habitat light conditions with its optimum in half-shade refers to its forest-steppe origin.

Boron nitride nanotube-based biosensing of various bacterium/viruses: continuum modelling-based simulation approach.

PubMed

Panchal, Mitesh B; Upadhyay, Sanjay H

2014-09-01

In this study, the feasibility of single walled boron nitride nanotube (SWBNNT)-based biosensors has been ensured considering the continuum modelling-based simulation approach, for mass-based detection of various bacterium/viruses. Various types of bacterium or viruses have been taken into consideration at the free-end of the cantilevered configuration of the SWBNNT, as a biosensor. Resonant frequency shift-based analysis has been performed with the adsorption of various bacterium/viruses considered as additional mass to the SWBNNT-based sensor system. The continuum mechanics-based analytical approach, considering effective wall thickness has been considered to validate the finite element method (FEM)-based simulation results, based on continuum volume-based modelling of the SWBNNT. As a systematic analysis approach, the FEM-based simulation results are found in excellent agreement with the analytical results, to analyse the SWBNNTs for their wide range of applications such as nanoresonators, biosensors, gas-sensors, transducers and so on. The obtained results suggest that by using the SWBNNT of smaller size the sensitivity of the sensor system can be enhanced and detection of the bacterium/virus having mass of 4.28 × 10⁻²⁴ kg can be effectively performed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deisenhofer, J.; Michel, H.

The history and methods of membrane protein crystallization are described. The solution of the structure of the photosynthetic reaction center from the bacterium Rhodopseudomonas viridis is described, and the structure of this membrane protein complex is correlated with its function as a light-driven electron pump across the photosynthetic membrane. Conclusions about the structure of the photosystem II reaction center from plants are drawn, and aspects of membrane protein structure are discussed. 68 refs., 15 figs., 2 tabs.

Ocean acidification alters the photosynthetic responses of a coccolithophorid to fluctuating ultraviolet and visible radiation.

PubMed

Jin, Peng; Gao, Kunshan; Villafañe, Virginia E; Campbell, Douglas A; Helbling, E Walter

2013-08-01

Mixing of seawater subjects phytoplankton to fluctuations in photosynthetically active radiation (400-700 nm) and ultraviolet radiation (UVR; 280-400 nm). These irradiance fluctuations are now superimposed upon ocean acidification and thinning of the upper mixing layer through stratification, which alters mixing regimes. Therefore, we examined the photosynthetic carbon fixation and photochemical performance of a coccolithophore, Gephyrocapsa oceanica, grown under high, future (1,000 μatm) and low, current (390 μatm) CO₂ levels, under regimes of fluctuating irradiances with or without UVR. Under both CO₂ levels, fluctuating irradiances, as compared with constant irradiance, led to lower nonphotochemical quenching and less UVR-induced inhibition of carbon fixation and photosystem II electron transport. The cells grown under high CO₂ showed a lower photosynthetic carbon fixation rate but lower nonphotochemical quenching and less ultraviolet B (280-315 nm)-induced inhibition. Ultraviolet A (315-400 nm) led to less enhancement of the photosynthetic carbon fixation in the high-CO₂-grown cells under fluctuating irradiance. Our data suggest that ocean acidification and fast mixing or fluctuation of solar radiation will act synergistically to lower carbon fixation by G. oceanica, although ocean acidification may decrease ultraviolet B-related photochemical inhibition.

An Energy Balance Model to Predict Chemical Partitioning in a Photosynthetic Microbial Mat

NASA Technical Reports Server (NTRS)

Hoehler, Tori M.; Albert, Daniel B.; DesMarais, David J.

2006-01-01

Studies of biosignature formation in photosynthetic microbial mat communities offer potentially useful insights with regards to both solar and extrasolar astrobiology. Biosignature formation in such systems results from the chemical transformation of photosynthetically fixed carbon by accessory microorganisms. This fixed carbon represents a source not only of reducing power, but also energy, to these organisms, so that chemical and energy budgets should be coupled. We tested this hypothesis by applying an energy balance model to predict the fate of photosynthetic productivity under dark, anoxic conditions. Fermentation of photosynthetically fixed carbon is taken to be the only source of energy available to cyanobacteria in the absence of light and oxygen, and nitrogen fixation is the principal energy demand. The alternate fate for fixed carbon is to build cyanobacterial biomass with Redfield C:N ratio. The model predicts that, under completely nitrogen-limited conditions, growth is optimized when 78% of fixed carbon stores are directed into fermentative energy generation, with the remainder allocated to growth. These predictions were compared to measurements made on microbial mats that are known to be both nitrogen-limited and populated by actively nitrogen-fixing cyanobacteria. In these mats, under dark, anoxic conditions, 82% of fixed carbon stores were diverted into fermentation. The close agreement between these independent approaches suggests that energy balance models may provide a quantitative means of predicting chemical partitioning within such systems - an important step towards understanding how biological productivity is ultimately partitioned into biosignature compounds.

Effect of arsenite-oxidizing bacterium B. laterosporus on arsenite toxicity and arsenic translocation in rice seedlings.

PubMed

Yang, Gui-Di; Xie, Wan-Ying; Zhu, Xi; Huang, Yi; Yang, Xiao-Jun; Qiu, Zong-Qing; Lv, Zhen-Mao; Wang, Wen-Na; Lin, Wen-Xiong

2015-10-01

Arsenite [As (III)] oxidation can be accelerated by bacterial catalysis, but the effects of the accelerated oxidation on arsenic toxicity and translocation in rice plants are poorly understood. Herein we investigated how an arsenite-oxidizing bacterium, namely Brevibacillus laterosporus, influences As (III) toxicity and translocation in rice plants. Rice seedlings of four cultivars, namely Guangyou Ming 118 (GM), Teyou Hang II (TH), Shanyou 63 (SY) and Minghui 63 (MH), inoculated with or without the bacterium were grown hydroponically with As (III) to investigate its effects on arsenic toxicity and translocation in the plants. Percentages of As (III) oxidation in the solutions with the bacterium (100%) were all significantly higher than those without (30-72%). The addition of the bacterium significantly decreased As (III) concentrations in SY root, GM root and shoot, while increased the As (III) concentrations in the shoot of SY, MH and TH and in the root of MH. Furthermore, the As (III) concentrations in the root and shoot of SY were both the lowest among the treatments with the bacterium. On the other hand, its addition significantly alleviated the As (III) toxicity on four rice cultivars. Among the treatments amended with B. laterosporus, the bacterium showed the best remediation on SY seedlings, with respect to the subdued As (III) toxicity and decreased As (III) concentration in its roots. These results indicated that As (III) oxidation accelerated by B. laterosporus could be an effective method to alleviate As (III) toxicity on rice seedlings. Copyright © 2015 Elsevier Inc. All rights reserved.

Triplet–triplet energy transfer in artificial and natural photosynthetic antennas

DOE PAGES

Ho, Junming; Kish, Elizabeth; Méndez-Hernandez, Dalvin D.; ...

2017-06-26

In photosynthetic organisms, protection against photo-oxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll to carotenoid triplet-triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, while it is ultrafast in the oxygen-rich chloroplasts of oxygen evolving photosynthetic organisms. In order to better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomericmore » carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET including a resonance Raman based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by DFT calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). In conclusion, both DFT and EPR analysis further indicates that upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.« less

Triplet–triplet energy transfer in artificial and natural photosynthetic antennas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Junming; Kish, Elizabeth; Méndez-Hernandez, Dalvin D.

In photosynthetic organisms, protection against photo-oxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll to carotenoid triplet-triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, while it is ultrafast in the oxygen-rich chloroplasts of oxygen evolving photosynthetic organisms. In order to better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomericmore » carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET including a resonance Raman based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by DFT calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). In conclusion, both DFT and EPR analysis further indicates that upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.« less

Triplet–triplet energy transfer in artificial and natural photosynthetic antennas

PubMed Central

Ho, Junming; Kish, Elizabeth; Méndez-Hernández, Dalvin D.; WongCarter, Katherine; Pillai, Smitha; Kodis, Gerdenis; Niklas, Jens; Poluektov, Oleg G.; Gust, Devens; Moore, Thomas A.; Moore, Ana L.; Batista, Victor S.

2017-01-01

In photosynthetic organisms, protection against photooxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll-to-carotenoid triplet–triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, whereas it is ultrafast in the oxygen-rich chloroplasts of oxygen-evolving photosynthetic organisms. To better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomeric carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET, including a resonance Raman-based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by density functional theory (DFT) calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light-harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). Both DFT and electron paramagnetic resonance (EPR) analyses further indicate that, upon T-TET, the triplet wave function is localized on the carotenoid in both dyads. PMID:28652359

Photosynthetic tolerance to non-resource stress influences competition importance and intensity in an invaded estuary.

PubMed

Tang, Long; Wolf, Amelia A; Gao, Yang; Wang, Cheng Huan

2018-06-01

In an attempt to clarify the role of environmental and biotic interactions on plant growth, there has been a long-running ecological debate over whether the intensity and importance of competition stabilizes, increases or decreases across environmental gradients. We conducted an experiment in a Chinese estuary to investigate the effects of a non-resource stress gradient, soil salinity (from 1.4‰ to 19.0‰ salinity), on the competitive interactions between native Phragmites australis and invasive Spartina alterniflora. We linked these effects to measurements of photosynthetic activities to further elucidate the underlying physiological mechanism behind the competitive interactions and the driver of invasion. The experiments revealed that while biomass of both species decreased in the presence of the other, competition did not alter photosynthetic activity of either species over time. P. australis exhibited high photosynthetic activity, including low chlorophyllase activity, high chlorophyll content, high stomatal conductance and high net photosynthetic rate, at low salinity. Under these conditions, P. australis experienced low competitive intensity, leading to high biomass production and competitive exclusion of S. alterniflora. The opposite was observed for S. alterniflora: while competitive intensity experienced by P. australis increased with increasing salinity, and photosynthetic activity, biomass, competitive dominance and the importance of competition for P. australis growth decreased, those of S. alterniflora were stable. These findings demonstrate that S. alterniflora invasion driven by competitive exclusion are likely to occur and expand in high salinity zones. The change in the nature of competition along a non-resource stress gradient differs between competitors likely due to differences in photosynthetic tolerance to salinity. The driver of growth of the less-tolerant species changes from competition to non-resource stress factors with

Impacts of genetically engineered alterations in carbon sink pathways on photosynthetic performance

DOE PAGES

Holland, Steven C.; Artier, Juliana; Miller, Neil T.; ...

2016-10-05

Genetic engineering of photosynthetic organisms typically redirects native metabolism towards desirable products, which thereby represent new metabolic sinks. There is limited information on how these modifications impact the evolved mechanisms of photosynthetic energy metabolism and cellular growth. Two engineered strains of Synechocystis sp. PCC 6803 with altered carbon sink capacity were assayed for their photosynthetic and CO 2 concentrating mechanism properties in conditions of high and low inorganic carbon (Ci) availability. In the ΔglgC mutant, glycogen cannot be synthesized and a carbon sink pathway has been effectively removed. The JU547 strain has been engineered by integration of the Pseudomonas syringaemore » ethylene forming enzyme and provides a new sink. When cultured under high carbon conditions, ΔglgC displayed diminished photochemical efficiency, a more reduced NADPH pool, delayed initiation of the Calvin-Benson-Bassham cycle, and impairment of linear and cyclic electron flows. It also exhibited a large decrease in photochemical quenching indicative of the accumulation of Q A-, normally associated with a reduced PQ pool, but appears instead to be the result of an undefined dissipative mechanism to spill excess energy. In the case of carbon sink integration, JU547 displayed slightly more oxidized PQ and NADPH pools and increased rates of cyclic electron flow and an enhanced demand for inorganic carbon as suggested by increase in the expression of the bicarbonate transporter, SbtA. Overall, the results highlight the importance of the native regulatory network of autotrophic metabolism in governing photosynthetic performance and provide cogent examples of both predicable and difficult to predict phenotypic consequences upon installation of new pathways in autotrophs.« less

Methyl Jasmonate Alleviates Cadmium-Induced Photosynthetic Damages through Increased S-Assimilation and Glutathione Production in Mustard

PubMed Central

Per, Tasir S.; Khan, Nafees A.; Masood, Asim; Fatma, Mehar

2016-01-01

The effect of methyl jasmonate (MeJA) in mitigation of 50 μM cadmium (Cd) toxicity on structure and function of photosynthetic apparatus in presence or absence of 1.0 mM SO42– was investigated in mustard (Brassica juncea L. cv. Ro Agro 4001) at 30 days after sowing. Plants exhibited increased oxidative stress, impaired photosynthetic function when grown with Cd, but MeJA in presence of sulfur (S) more prominently ameliorated Cd effects through increased S-assimilation and production of reduced glutathione (GSH) and promoted photosynthetic functions. The transmission electron microscopy showed that MeJA protected chloroplast structure against Cd-toxicity. The use of GSH biosynthetic inhibitor, buthionine sulfoximine (BSO) substantiated the findings that ameliorating effect of MeJA was through GSH production. MeJA could not alleviate Cd effects when BSO was used due to unavailability of GSH even with the input of S. The study shows that MeJA regulates S-assimilation and GSH production for protection of structure and function of photosynthetic apparatus in mustard plants under Cd stress. PMID:28066485

Interaction between photosynthetic electron transport and chloroplast sinks triggers protection and signalling important for plant productivity

PubMed Central

Gollan, Peter J.; Lima-Melo, Yugo; Tiwari, Arjun; Tikkanen, Mikko

2017-01-01

The photosynthetic light reactions provide energy that is consumed and stored in electron sinks, the products of photosynthesis. A balance between light reactions and electron consumption in the chloroplast is vital for plants, and is protected by several photosynthetic regulation mechanisms. Photosystem I (PSI) is particularly susceptible to photoinhibition when these factors become unbalanced, which can occur in low temperatures or in high light. In this study we used the pgr5 Arabidopsis mutant that lacks ΔpH-dependent regulation of photosynthetic electron transport as a model to study the consequences of PSI photoinhibition under high light. We found that PSI damage severely inhibits carbon fixation and starch accumulation, and attenuates enzymatic oxylipin synthesis and chloroplast regulation of nuclear gene expression after high light stress. This work shows that modifications to regulation of photosynthetic light reactions, which may be designed to improve yield in crop plants, can negatively impact metabolism and signalling, and thereby threaten plant growth and stress tolerance. This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’. PMID:28808104

Comparing photosynthetic characteristics of Isoetes sinensis Palmer under submerged and terrestrial conditions.

PubMed

Yang, Tao; Liu, Xing

2015-12-04

Crassulacean acid metabolism (CAM) is widespread in terrestrial and aquatic species, plastic in response to environmental changes. Isoetes L. is one of the earliest basal vascular plants and CAM is popular in this genus. Isoetes sinensis Palmer is an amphibious species, alternating frequently between terrestrial and aquatic environments. Given this, we investigated and compared photosynthetic characteristics over a diurnal cycle under submerged condition (SC) and terrestrial condition (TC). The results suggest that I. sinensis possesses a stronger CAM capacity under SC. Compared with under TC, titratable acidity levels and organic acid concentrations were more enriched under SC, whereas soluble sugar or starch and protein levels were lower under SC. Transcript analyses for nine photosynthetic genes revealed that CAM-associated genes possessed high transcripts under SC, but C3-related transcripts were highly expressed under TC. In addition, the enzyme activity measurements demonstrated that PEPC activity over a diurnal cycle was slightly higher under SC, whereas Rubisco activity during the daytime was greater under TC. This comprehensive study probably facilitates general understandings about the CAM photosynthetic characteristics of Isoetes in response to the environmental changes.

Methods and constructs for expression of foreign proteins in photosynthetic organisms

DOEpatents

Laible, Philip D.; Hanson, Deborah K.

2002-01-01

A method for expressing and purifying foreign proteins in photosynthetic organisms comprising the simultaneous expression of both the heterologous protein and a means for compartmentalizing or sequestering of the protein.

Characterization of a novel extremely alkalophilic bacterium

NASA Technical Reports Server (NTRS)

Souza, K. A.; Deal, P. H.

1977-01-01

A new alkalophilic bacterium, isolated from a natural spring of high pH is characterized. It is a Gram-positive, non-sporulating, motile rod requiring aerobic and alkaline conditions for growth. The characteristics of this organism resemble those of the coryneform group of bacteria; however, there are no accepted genera within this group with which this organism can be closely matched. Therefore, a new genus may be warranted.

A hairy-leaf gene, BLANKET LEAF, of wild Oryza nivara increases photosynthetic water use efficiency in rice.

PubMed

Hamaoka, Norimitsu; Yasui, Hideshi; Yamagata, Yoshiyuki; Inoue, Yoko; Furuya, Naruto; Araki, Takuya; Ueno, Osamu; Yoshimura, Atsushi

2017-12-01

High water use efficiency is essential to water-saving cropping. Morphological traits that affect photosynthetic water use efficiency are not well known. We examined whether leaf hairiness improves photosynthetic water use efficiency in rice. A chromosome segment introgression line (IL-hairy) of wild Oryza nivara (Acc. IRGC105715) with the genetic background of Oryza sativa cultivar 'IR24' had high leaf pubescence (hair). The leaf hairs developed along small vascular bundles. Linkage analysis in BC 5 F 2 and F 3 populations showed that the trait was governed by a single gene, designated BLANKET LEAF (BKL), on chromosome 6. IL-hairy plants had a warmer leaf surface in sunlight, probably due to increased boundary layer resistance. They had a lower transpiration rate under moderate and high light intensities, resulting in higher photosynthetic water use efficiency. Introgression of BKL on chromosome 6 from O. nivara improved photosynthetic water use efficiency in the genetic background of IR24.

Measuring indigenous photosynthetic organisms to detect chemical warefare agents in water

DOEpatents

Greenbaum, Elias; Sanders, Charlene A.

2005-11-15

A method of testing water to detect the presence of a chemical or biological warfare agent is disclosed. The method is carried out by establishing control data by providing control water containing indigenous organisms but substantially free of a chemical and a biological warfare agent. Then measuring photosynthetic activity of the control water with a fluorometer to obtain control data to compare with test data to detect the presence of the chemical or agent. The test data is gathered by providing test water comprising the same indigenous organisms as contained in the control water. Further, the test water is suspected of containing the chemical or agent to be tested for. Photosynthetic activity is also measured by fluorescence induction in the test water using a fluorometer.

Leaf development and demography explain photosynthetic seasonality in Amazon evergreen forests

USGS Publications Warehouse

Wu, Jin; Albert, Lauren; Lopes, Aline; Restrepo-Coupe, Natalia; Hayek, Matthew; Wiedemann, Kenia T.; Guan, Kaiyu; Stark, Scott C.; Christoffersen, Bradley; Prohaska, Neill; Tavares, Julia V.; Marostica, Suelen; Kobayashi, Hideki; Ferreira, Maurocio L.; Campos, Kleber Silva; da Silva, Rodrigo; Brando, Paulo M.; Dye, Dennis G.; Huxman, Travis E.; Huete, Alfredo; Nelson, Bruce; Saleska, Scott

2016-01-01

In evergreen tropical forests, the extent, magnitude, and controls on photosynthetic seasonality are poorly resolved and inadequately represented in Earth system models. Combining camera observations with ecosystem carbon dioxide fluxes at forests across rainfall gradients in Amazônia, we show that aggregate canopy phenology, not seasonality of climate drivers, is the primary cause of photosynthetic seasonality in these forests. Specifically, synchronization of new leaf growth with dry season litterfall shifts canopy composition toward younger, more light-use efficient leaves, explaining large seasonal increases (~27%) in ecosystem photosynthesis. Coordinated leaf development and demography thus reconcile seemingly disparate observations at different scales and indicate that accounting for leaf-level phenology is critical for accurately simulating ecosystem-scale responses to climate change.

Extracellular nucleic acids of the marine bacterium Rhodovulum sulfidophilum and recombinant RNA production technology using bacteria.

PubMed

Kikuchi, Yo; Umekage, So

2018-02-01

Extracellular nucleic acids of high molecular weight are detected ubiquitously in seawater. Recent studies have indicated that these nucleic acids are, at least in part, derived from active production by some bacteria. The marine bacterium Rhodovulum sulfidophilum is one of those bacteria. Rhodovulumsulfidophilum is a non-sulfur phototrophic marine bacterium that is known to form structured communities of cells called flocs, and to produce extracellular nucleic acids in culture media. Recently, it has been revealed that this bacterium produces gene transfer agent-like particles and that this particle production may be related to the extracellular nucleic acid production mechanism. This review provides a summary of recent physiological and genetic studies of these phenomena and also introduces a new method for extracellular production of artificial and biologically functional RNAs using this bacterium. In addition, artificial RNA production using Escherichia coli, which is related to this topic, will also be described. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Involvement of ethylene in gibberellic acid-induced sulfur assimilation, photosynthetic responses, and alleviation of cadmium stress in mustard.

PubMed

Masood, Asim; Khan, M Iqbal R; Fatma, Mehar; Asgher, Mohd; Per, Tasir S; Khan, Nafees A

2016-07-01

The role of gibberellic acid (GA) or sulfur (S) in stimulation of photosynthesis is known. However, information on the involvement of ethylene in GA-induced photosynthetic responses and cadmium (Cd) tolerance is lacking. This work shows that ethylene is involved in S-assimilation, photosynthetic responses and alleviation of Cd stress by GA in mustard (Brassica juncea L.). Plants grown with 200 mg Cd kg(-1) soil were less responsive to ethylene despite high ethylene evolution and showed photosynthetic inhibition. Plants receiving 10 μM GA spraying plus 100 mg S kg(-1) soil supplementation exhibited increased S-assimilation and photosynthetic responses under Cd stress. Application of GA plus S decreased oxidative stress of plants grown with Cd and limited stress ethylene formation to the range suitable for promoting sulfur use efficiency (SUE), glutathione (GSH) production and photosynthesis. The role of ethylene in GA-induced S-assimilation and reversal of photosynthetic inhibition by Cd was substantiated by inhibiting ethylene biosynthesis with the use of aminoethoxyvinylglycine (AVG). The suppression of S-assimilation and photosynthetic responses by inhibiting ethylene in GA plus S treated plants under Cd stress indicated the involvement of ethylene in GA-induced S-assimilation and Cd stress alleviation. The outcome of the study is important to unravel the interaction between GA and ethylene and their role in Cd tolerance in plants. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Complete Genome Sequence of the p-Nitrophenol-Degrading Bacterium Pseudomonas putida DLL-E4

PubMed Central

Hu, Xiaojun; Wang, Jue; Wang, Fei; Chen, Qiongzhen; Huang, Yan

2014-01-01

The first complete genome sequence of a p-nitrophenol (PNP)-degrading bacterium is reported here. Pseudomonas putida DLL-E4, a Gram-negative bacterium isolated from methyl-parathion-polluted soil, can utilize PNP as the sole carbon and nitrogen source. P. putida DLL-E4 has a 6,484,062 bp circular chromosome that contains 5,894 genes, with a G+C content of 62.46%. PMID:24948765

Differential Mechanisms of Photosynthetic Acclimation to Light and Low Temperature in Arabidopsis and the Extremophile Eutrema salsugineum

PubMed Central

Khanal, Nityananda; Bray, Geoffrey E.; Grisnich, Anna; Moffatt, Barbara A.; Gray, Gordon R.

2017-01-01

Photosynthetic organisms are able to sense energy imbalances brought about by the overexcitation of photosystem II (PSII) through the redox state of the photosynthetic electron transport chain, estimated as the chlorophyll fluorescence parameter 1-qL, also known as PSII excitation pressure. Plants employ a wide array of photoprotective processes that modulate photosynthesis to correct these energy imbalances. Low temperature and light are well established in their ability to modulate PSII excitation pressure. The acquisition of freezing tolerance requires growth and development a low temperature (cold acclimation) which predisposes the plant to photoinhibition. Thus, photosynthetic acclimation is essential for proper energy balancing during the cold acclimation process. Eutrema salsugineum (Thellungiella salsuginea) is an extremophile, a close relative of Arabidopsis thaliana, but possessing much higher constitutive levels of tolerance to abiotic stress. This comparative study aimed to characterize the photosynthetic properties of Arabidopsis (Columbia accession) and two accessions of Eutrema (Yukon and Shandong) isolated from contrasting geographical locations at cold acclimating and non-acclimating conditions. In addition, three different growth regimes were utilized that varied in temperature, photoperiod and irradiance which resulted in different levels of PSII excitation pressure. This study has shown that these accessions interact differentially to instantaneous (measuring) and long-term (acclimation) changes in PSII excitation pressure with regard to their photosynthetic behaviour. Eutrema accessions contained a higher amount of photosynthetic pigments, showed higher oxidation of P700 and possessed more resilient photoprotective mechanisms than that of Arabidopsis, perhaps through the prevention of PSI acceptor-limitation. Upon comparison of the two Eutrema accessions, Shandong demonstrated the greatest PSII operating efficiency (ΦPSII) and P700 oxidizing

Pathogenicity of Moraxella osloensis, a bacterium associated with the nematode Phasmarhabditis hermaphrodita, to the slug Deroceras reticulatum.

PubMed

Tan, L; Grewal, P S

2001-11-01

Moraxella osloensis, a gram-negative bacterium, is associated with Phasmarhabditis hermaphrodita, a nematode parasite of slugs. This bacterium-feeding nematode has potential for the biological control of slugs, especially the grey garden slug, Deroceras reticulatum. Infective juveniles of P. hermaphrodita invade the shell cavity of the slug, develop into self-fertilizing hermaphrodites, and produce progeny, resulting in host death. However, the role of the associated bacterium in the pathogenicity of the nematode to the slug is unknown. We discovered that M. osloensis alone is pathogenic to D. reticulatum after injection into the shell cavity or hemocoel of the slug. The bacteria from 60-h cultures were more pathogenic than the bacteria from 40-h cultures, as indicated by the higher and more rapid mortality of the slugs injected with the former. Coinjection of penicillin and streptomycin with the 60-h bacterial culture reduced its pathogenicity to the slug. Further work suggested that the reduction and loss of pathogenicity of the aged infective juveniles of P. hermaphrodita to D. reticulatum result from the loss of M. osloensis from the aged nematodes. Also, axenic J1/J2 nematodes were nonpathogenic after injection into the shell cavity. Therefore, we conclude that the bacterium is the sole killing agent of D. reticulatum in the nematode-bacterium complex and that P. hermaphrodita acts only as a vector to transport the bacterium into the shell cavity of the slug. The identification of the toxic metabolites produced by M. osloensis is being pursued.

Tufted hairgrass (Deschampsia caespitosa) exhibits a lower photosynthetic plasticity than Antarctic hairgrass (D. antarctica).

PubMed

Bystrzejewska-Piotrowska, Grazyna; Urban, Pawel L

2009-06-01

The aim of our work was to assess photosynthetic plasticity of two hairgrass species with different ecological origins (a temperate zone species, Deschampsia caespitosa (L.) Beauv. and an Antarctic species, D. antarctica) and to consider how the anticipated climate change may affect vitality of these plants. Measurements of chlorophyll fluorescence showed that the photosystem II (PSII) quantum efficiency of D. caespitosa decreased during 4 d of incubation at 4 degrees C but it remained stable in D. antarctica. The fluorescence half-rise times were almost always lower in D. caespitosa than in D. antarctica, irrespective of the incubation temperature. These results indicate that the photosynthetic apparatus of D. caespitosa has poorer performance in these conditions. D. caespitosa reached the maximum photosynthesis rate at a higher temperature than D. antarctica although the values obtained at 8 degrees C were similar in both species. The photosynthetic water-use efficiency (photosynthesis-to-transpiration ratio, P/E) emerges as an important factor demonstrating presence of mechanisms which facilitate functioning of a plant in non-optimal conditions. Comparison of the P/E values, which were higher in D. antarctica than in D. caespitosa at low and medium temperatures, confirms a high degree of adjustability of the photosynthetic apparatus in D. antarctica and unveils the lack of such a feature in D. caespitosa.

Cultivar variation in cotton photosynthetic performance under different temperature regimes

USDA-ARS?s Scientific Manuscript database

Cotton (Gossypium hirsutum L.) yields are impacted by overall photosynthetic production. Factors that influence crop photosynthesis are the plants genetic makeup and the environmental conditions. This study investigated cultivar variation in photosynthesis when plants were grown in the field under...

Elucidation of Genetic Backgrounds Necessary for Chlorophyll a Biosynthesis Toward Artificial Creation of Oxygenic Photosynthesis

NASA Astrophysics Data System (ADS)

Tsukatani, Yusuke; Masuda, Shinji

2015-09-01

We succeeded to create the genetically modified purple photosynthetic bacterium capable of synthesizing chlorophyll a. The results indicate that not only chlorophyll synthase, but also an enzyme for galactolipid synthesis and reaction center proteins are required for accumulating chlorophyll a.

Halomonas maura is a physiologically versatile bacterium of both ecological and biotechnological interest.

PubMed

Llamas, Inmaculada; del Moral, Ana; Martínez-Checa, Fernando; Arco, Yolanda; Arias, Soledad; Quesada, Emilia

2006-01-01

Halomonas maura is a bacterium of great metabolic versatility. We summarise in this work some of the properties that make it a very interesting microorganism both from an ecological and biotechnological point of view. It plays an active role in the nitrogen cycle, is capable of anaerobic respiration in the presence of nitrate and has recently been identified as a diazotrophic bacterium. Of equal interest is mauran, the exopolysaccharide produced by H. maura, which contributes to the formation of biofilms and thus affords the bacterium advantages in the colonisation of its saline niches. Mauran is highly viscous, shows thixotropic and pseudoplastic behaviour, has the capacity to capture heavy metals and exerts a certain immunomodulator effect in medicine. All these attributes have prompted us to make further investigations into its molecular characteristics. To date we have described 15 open reading frames (ORF's) related to exopolysaccharide production, nitrogen fixation and nitrate reductase activity among others.

Deinococcus mumbaiensis sp. nov., a radiation-resistant pleomorphic bacterium isolated from Mumbai, India.

PubMed

Shashidhar, Ravindranath; Bandekar, Jayant R

2006-01-01

A radiation-resistant, Gram-negative and pleomorphic bacterium (CON-1) was isolated from a contaminated tryptone glucose yeast extract agar plate in the laboratory. It was red pigmented, nonmotile, nonsporulating, and aerobic, and contained MK-8 as respiratory quinone. The cell wall of this bacterium contained ornithine. The major fatty acids were C16:0, C16:1, C17:0, C18:1 and iso C18:0. The DNA of CON-1 had a G+C content of 70 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that CON-1 exhibited a maximum similarity (94.72%) with Deinococcus grandis. Based on the genotypic, phenotypic and chemotaxonomic characteristics, the bacterium CON-1 was identified as a new species of the genus Deinococcus, for which the name Deinococcus mumbaiensis sp. nov. is proposed. The type strain of D. mumbaiensis is CON-1 (MTCC 7297(T)=DSM 17424(T)).

[Primary study on photosynthetic characteristics of Dendrobium nobile].

PubMed

Su, Wenhua; Zhang, Guangfei

2003-03-01

With LiCor-6400 Portable Photosynthesis System, carbon dioxide exchange pattern for leaves of Dendrobium nobile during 24 hours were studied in sunny day and rainy day, and the variation of CO2 exchange rate to light intensity was analysed. The results showed that in sunny day D. nobile absorbed CO2 in all day except at midday, at noon photorespiration took place. The CO2 exchange pattern was similar to Crassulacean Acid Metabolism(CAM). In rainy day CO2 uptake was in all day, at night CO2 uptake was monitored at 21:00, then CO2 released from 23:00 to dawn. Light saturation point was 1000 mumol/m2s. Over light saturation point photosynthesis, photoinhibition of photosynthesis will be induced by high-light. Exposed to high-light, the light saturation point and the CO2 uptake velocity would be decreased. With variation of environmental factors, photosynthetic pathway in D. nobile could change from CAM to C3 photosynthetic metabolism. It may be one of main reasons for D. nobile to adapt to the shade-requiring environment, the slow growth and rareness in nature.

PS2013 Satellite Workshop on Photosynthetic Light-Harvesting Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niederman, Robert A.; Blankenship, Robert E.; Frank, Harry A.

These funds were used for partial support of the PS2013 Satellite Workshop on Photosynthetic Light-Harvesting Systems, that was held on 8-11 August, 2013, at Washington University, St. Louis, MO. This conference, held in conjunction with the 16th International Congress on Photosynthesis/St. Louis, continued a long tradition of light-harvesting satellite conferences that have been held prior to the previous six international photosynthesis congresses. In this Workshop, the basis was explored for the current interest in replacing fossil fuels with energy sources derived form direct solar radiation, coupled with light-driven electron transport in natural photosynthetic systems and how they offer a valuablemore » blueprint for conversion of sunlight to useful energy forms. This was accomplished through sessions on the initial light-harvesting events in the biological conversion of solar energy to chemically stored energy forms, and how these natural photosynthetic processes serve as a guide to the development of robust bio-hybrid and artificial systems for solar energy conversion into both electricity or chemical fuels. Organized similar to a Gordon Research Conference, a lively, informal and collegial setting was established, highlighting the exchange of exciting new data and unpublished results from ongoing studies. A significant amount of time was set aside for open discussion and interactive poster sessions, with a special session devoted to oral presentations by talented students and postdoctoral fellows judged to have the best posters. This area of research has seen exceptionally rapid progress in recent years, with the availability of a number of antenna protein structures at atomic resolution, elucidation of the molecular surface architecture of native photosynthetic membranes by atomic force microscopy and the maturing of ultrafast spectroscopic and molecular biological techniques for the investigation and manipulation of photosynthetic systems. The

From Genome to Function: Systematic Analysis of the Soil Bacterium Bacillus Subtilis

PubMed Central

Crawshaw, Samuel G.; Wipat, Anil

2001-01-01

Bacillus subtilis is a sporulating Gram-positive bacterium that lives primarily in the soil and associated water sources. Whilst this bacterium has been studied extensively in the laboratory, relatively few studies have been undertaken to study its activity in natural environments. The publication of the B. subtilis genome sequence and subsequent systematic functional analysis programme have provided an opportunity to develop tools for analysing the role and expression of Bacillus genes in situ. In this paper we discuss analytical approaches that are being developed to relate genes to function in environments such as the rhizosphere. PMID:18628943

Complete Genome Sequence of a thermotolerant sporogenic lactic acid bacterium, Bacillus coagulans strain 36D1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Gary; Dalin, Eileen; Tice, Hope

Bacillus coagulans is a ubiquitous soil bacterium that grows at 50-55 C and pH 5.0 and fer-ments various sugars that constitute plant biomass to L (+)-lactic acid. The ability of this sporogenic lactic acid bacterium to grow at 50-55 C and pH 5.0 makes this organism an attractive microbial biocatalyst for production of optically pure lactic acid at industrial scale not only from glucose derived from cellulose but also from xylose, a major constituent of hemi-cellulose. This bacterium is also considered as a potential probiotic. Complete genome squence of a representative strain, B. coagulans strain 36D1, is presented and discussed.

Genome Sequence of the Soil Bacterium Janthinobacterium sp. KBS0711

PubMed Central

Shoemaker, William R.; Muscarella, Mario E.

2015-01-01

We present a draft genome of Janthinobacterium sp. KBS0711 that was isolated from agricultural soil. The genome provides insight into the ecological strategies of this bacterium in free-living and host-associated environments. PMID:26089434

Interactive effects of cadmium and acid rain on photosynthetic light reaction in soybean seedlings.

PubMed

Sun, Zhaoguo; Wang, Lihong; Chen, Minmin; Wang, Lei; Liang, Chanjuan; Zhou, Qing; Huang, Xiaohua

2012-05-01

Interactive effects of cadmium (Cd(2+)) and acid rain on photosynthetic light reaction in soybean seedlings were investigated under hydroponic conditions. Single treatment with Cd(2+) or acid rain and the combined treatment decreased the content of chlorophyll, Hill reaction rate, the activity of Mg(2+)-ATPase, maximal photochemical efficiency and maximal quantum yield, increased initial fluorescence and damaged the chloroplast structure in soybean seedlings. In the combined treatment, the change in the photosynthetic parameters and the damage of chloroplast structure were stronger than those of any single pollution. Meanwhile, Cd(2+) and acid rain had the interactive effects on the test indices in soybean seedlings. The results indicated that the combined pollution of Cd(2+) and acid rain aggravated the toxic effect of the single pollution of Cd(2+) or acid rain on the photosynthetic parameters due to the serious damage to the chloroplast structure. Copyright © 2011 Elsevier Inc. All rights reserved.

EmbRS a new two-component system that inhibits biofilm formation and saves Rubrivivax gelatinosus from sinking.

PubMed

Steunou, Anne Soisig; Liotenberg, Sylviane; Soler, Marie-Noêlle; Briandet, Romain; Barbe, Valérie; Astier, Chantal; Ouchane, Soufian

2013-06-01

Photosynthetic bacteria can switch from planktonic lifestyle to phototrophic biofilm in mats in response to environmental changes. The mechanisms of phototrophic biofilm formation are, however, not characterized. Herein, we report a two-component system EmbRS that controls the biofilm formation in a photosynthetic member of the Burkholderiales order, the purple bacterium Rubrivivax gelatinosus. EmbRS inactivation results in cells that form conspicuous bacterial veils and fast-sinking aggregates in liquid. Biofilm analyses indicated that EmbRS represses the production of an extracellular matrix and biofilm formation. Mapping of transposon mutants that partially or completely restore the wild-type (WT) phenotype allowed the identification of two gene clusters involved in polysaccharide synthesis, one fully conserved only in Thauera sp., a floc-forming wastewater bacterium. A second two-component system BmfRS and a putative diguanylate cyclase BdcA were also identified in this screen suggesting their involvement in biofilm formation in this bacterium. The role of polysaccharides in sinking of microorganisms and organic matter, as well as the importance and the evolution of such regulatory system in phototrophic microorganisms are discussed. © 2013 The Authors. Microbiology Open published by John Wiley & Sons Ltd.

Direct laser immobilization of photosynthetic material on screen printed electrodes for amperometric biosensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boutopoulos, Christos; Zergioti, Ioanna; Touloupakis, Eleftherios

This letter demonstrates the direct laser printing of photosynthetic material onto low cost nonfunctionalized screen printed electrodes for the fabrication of photosynthesis-based amperometric biosensors. The high kinetic energy of the transferred material induces direct immobilization of the thylakoids onto the electrodes without the use of linkers. This type of immobilization is able to establish efficient electrochemical contact between proteins and electrode, stabilizing the photosynthetic biomolecule and transporting electrons to the solid state device with high efficiency. The functionality of the laser printed biosensors was evaluated by the detection of a common herbicide such as Linuron.

Structure and morphology of magnetite anaerobically-produced by a marine magnetotactic bacterium and a dissimilatory iron-reducing bacterium

USGS Publications Warehouse

Sparks, N.H.C.; Mann, S.; Bazylinski, D.A.; Lovley, D.R.; Jannasch, H.W.; Frankel, R.B.

1990-01-01

Intracellular crystals of magnetite synthesized by cells of the magnetotactic vibroid organism, MV-1, and extracellular crystals of magnetite produced by the non-magnetotactic dissimilatory iron-reducing bacterium strain GS-15, were examined using high-resolution transmission electron microscopy, electron diffraction and 57Fe Mo??ssbauer spectroscopy. The magnetotactic bacterium contained a single chain of approximately 10 crystals aligned along the long axis of the cell. The crystals were essentially pure stoichiometric magnetite. When viewed along the crystal long axis the particles had a hexagonal cross-section whereas side-on they appeared as rectangules or truncated rectangles of average dimension, 53 ?? 35 nm. These findings are explained in terms of a three-dimensional morphology comprising a hexagonal prism of {110} faces which are capped and truncated by {111} end faces. Electron diffraction and lattice imaging studies indicated that the particles were structurally well-defined single crystals. In contrast, magnetite particles produced by the strain, GS-15 were irregular in shape and had smaller mean dimensions (14 nm). Single crystals were imaged but these were not of high structural perfection. These results highlight the influence of intracellular control on the crystallochemical specificity of bacterial magnetites. The characterization of these crystals is important in aiding the identification of biogenic magnetic materials in paleomagnetism and in studies of sediment magnetization. ?? 1990.

Nitrate and Ammonium Induced Photosynthetic Suppression in N-Limited Selenastrum minutum1

PubMed Central

Elrifi, Ivor R.; Turpin, David H.

1986-01-01

Nitrate-limited chemostat cultures of Selenastrum minutum Naeg. Collins (Chlorophyta) were used to determine the effects of nitrogen addition on photosynthesis, dark respiration, and dark carbon fixation. Addition of NO3− or NH4+ induced a transient suppression of photosynthetic carbon fixation (70 and 40% respectively). Intracellular ribulose bisphosphate levels decreased during suppression and recovered in parallel with photosynthesis. Photosynthetic oxygen evolution was decreased by N-pulsing under saturating light (650 microeinsteins per square meter per second). Under subsaturating light intensities (<165 microeinsteins per square meter per second) NH4+ addition resulted in O2 consumption in the light which was alleviated by the presence of the tricarboxylic acid cycle inhibitor fluoroacetate. Addition of NO3− or NH4+ resulted in a large stimulation of dark respiration (67 and 129%, respectively) and dark carbon fixation (360 and 2080%, respectively). The duration of N-induced perturbations was dependent on the concentration of added N. Inhibition of glutamine 2-oxoglutarate aminotransferase by azaserine alleviated all these effects. It is proposed that suppression of photosynthetic carbon fixation in response to N pulsing was the result of a competition for metabolites between the Calvin cycle and nitrogen assimilation. Carbon skeletons required for nitrogen assimilation would be derived from tricarboxylic acid cycle intermediates. To maintain tricarboxylic acid cycle activity triose phosphates would be exported from the chloroplast. This would decrease the rate of ribulose bisphosphate regeneration and consequently decrease net photosynthetic carbon accumulation. Stoichiometric calculations indicate that the Calvin cycle is one source of triose phosphates for N assimilation; however, during transient N resupply the major demand for triose phosphates must be met by starch or sucrose breakdown. The effects of N-pulsing on O2 evolution, dark respiration

Insight into the radiotolerance of the life support bacterium Rhodospirillum rubrum S1H by means of phenotypic and transcriptomic methods

NASA Astrophysics Data System (ADS)

Mastroleo, Felice; Monsieurs, Pieter; Leys, Natalie

The MELiSSA life support system from the European Space Agency is targeting the produc-tion of oxygen, water and food by recycling organic waste. Among different types of pro-cesses, MELiSSA uses several interconnected bioreactors inhabited by microorganisms and higher plants (Hendrickx et al., 2006; Mergeay et al., 1988). Because this loop is foreseen to be functional in space where it will be exposed to higher doses and different spectra of ionizing radiation, it was decided to screen the radiotolerance of the organisms used. In this study, the radiotolerance (i.e. tolerance to ionizing radiation) of the photosynthetic bacterium Rho-dospirillum rubrum S1H was investigated. In this test, first the effect of low energy Cobalt-60 gamma rays, were tested. To assess the radiotolerance of bacterium S1H, the survival rate after increasing exposure was determined. R. rubrum S1H appeared relatively radiosensitive, as the radiation dose at which 90% of the population was killed (D10 value) was 4 times lower than the model bacterium Escherichia coli. It was demonstrate that the culture medium has an impact on radiation tolerance. This survival curve also permitted to select a number of sub-lethal ionizing radiation doses (¡ D10 ), that were used to analyze the gene expression response of R. rubrum S1H after gamma irradiation. The microarray transcriptome analysis results ob-tained from different doses and different culture medium showed a significant response of the bacterium to sublethal doses. Potential marker genes for ionizing radiation stress in R. rubrum S1H were identified. By quantitative PCR, it was shown that the expression of these marker genes increased with the recovery time after exposure to ionizing radiation. In other words, the radiation tolerance and the response of R. rubrum S1H to low energy Cobalt-60 gamma ionizing radiation was characterized. Therefore to ensure MELiSSA process robustness during extended space exploration mission, it is advised that

Transcriptome analysis of the rhizosphere bacterium Azospirillum brasilense reveals an extensive auxin response.

PubMed

Van Puyvelde, Sandra; Cloots, Lore; Engelen, Kristof; Das, Frederik; Marchal, Kathleen; Vanderleyden, Jos; Spaepen, Stijn

2011-05-01

The rhizosphere bacterium Azospirillum brasilense produces the auxin indole-3-acetic acid (IAA) through the indole-3-pyruvate pathway. As we previously demonstrated that transcription of the indole-3-pyruvate decarboxylase (ipdC) gene is positively regulated by IAA, produced by A. brasilense itself or added exogenously, we performed a microarray analysis to study the overall effects of IAA on the transcriptome of A. brasilense. The transcriptomes of A. brasilense wild-type and the ipdC knockout mutant, both cultured in the absence and presence of exogenously added IAA, were compared.Interfering with the IAA biosynthesis/homeostasis in A. brasilense through inactivation of the ipdC gene or IAA addition results in much broader transcriptional changes than anticipated. Based on the multitude of changes observed by comparing the different transcriptomes, we can conclude that IAA is a signaling molecule in A. brasilense. It appears that the bacterium, when exposed to IAA, adapts itself to the plant rhizosphere, by changing its arsenal of transport proteins and cell surface proteins. A striking example of adaptation to IAA exposure, as happens in the rhizosphere, is the upregulation of a type VI secretion system (T6SS) in the presence of IAA. The T6SS is described as specifically involved in bacterium-eukaryotic host interactions. Additionally, many transcription factors show an altered regulation as well, indicating that the regulatory machinery of the bacterium is changing.

Pathogenicity of Moraxella osloensis, a Bacterium Associated with the Nematode Phasmarhabditis hermaphrodita, to the Slug Deroceras reticulatum

PubMed Central

Tan, Li; Grewal, Parwinder S.

2001-01-01

Moraxella osloensis, a gram-negative bacterium, is associated with Phasmarhabditis hermaphrodita, a nematode parasite of slugs. This bacterium-feeding nematode has potential for the biological control of slugs, especially the grey garden slug, Deroceras reticulatum. Infective juveniles of P. hermaphrodita invade the shell cavity of the slug, develop into self-fertilizing hermaphrodites, and produce progeny, resulting in host death. However, the role of the associated bacterium in the pathogenicity of the nematode to the slug is unknown. We discovered that M. osloensis alone is pathogenic to D. reticulatum after injection into the shell cavity or hemocoel of the slug. The bacteria from 60-h cultures were more pathogenic than the bacteria from 40-h cultures, as indicated by the higher and more rapid mortality of the slugs injected with the former. Coinjection of penicillin and streptomycin with the 60-h bacterial culture reduced its pathogenicity to the slug. Further work suggested that the reduction and loss of pathogenicity of the aged infective juveniles of P. hermaphrodita to D. reticulatum result from the loss of M. osloensis from the aged nematodes. Also, axenic J1/J2 nematodes were nonpathogenic after injection into the shell cavity. Therefore, we conclude that the bacterium is the sole killing agent of D. reticulatum in the nematode-bacterium complex and that P. hermaphrodita acts only as a vector to transport the bacterium into the shell cavity of the slug. The identification of the toxic metabolites produced by M. osloensis is being pursued. PMID:11679319

Development of a novel artificial medium based on utilization of algal photosynthetic metabolites by symbiotic heterotrophs.

PubMed

Watanabe, K; Imase, M; Aoyagi, H; Ohmura, N; Saiki, H; Tanaka, H

2008-09-01

(i) Quantitative and qualitative analyses of photosynthetic metabolites of Chlorella sorokiniana and elucidation of the mechanism of their utilization by algal symbionts. (ii) Development of artificial medium that imitates photoautotroph-heterotroph interaction and investigation of its suitability for isolation of novel microbes from the environment. Various components, including free dissolved carbohydrates, nitrogenous compounds and vitamin, were detected and together contributed 11.1% (as carbon content) of the total photosynthetic metabolites in the medium. Utilization of these photosynthetic metabolites in algal culture broth by algal symbionts was studied. Many symbionts showed specific utilization patterns. A novel artificial extracellular released organic carbon medium, which imitated the nutritional conditions surrounding algae, was developed based on the pattern of utilization of the algal metabolites by the symbiotic heterotrophs. About 42.9% of the isolates were closely related to photoautotrophic-dependent and oligotrophic bacteria. With the novel artificial medium, it was possible to selectively isolate some bacterial strains. Synthetic bacterial growth medium is an important and basic tool for bacterial isolation from environmental samples. The current study shows that preferential separation of typical bacterial subset can be achieved by using artificial medium that mimics photosynthetic metabolites.

Enzymes involved in organellar DNA replication in photosynthetic eukaryotes.

PubMed

Moriyama, Takashi; Sato, Naoki

2014-01-01

Plastids and mitochondria possess their own genomes. Although the replication mechanisms of these organellar genomes remain unclear in photosynthetic eukaryotes, several organelle-localized enzymes related to genome replication, including DNA polymerase, DNA primase, DNA helicase, DNA topoisomerase, single-stranded DNA maintenance protein, DNA ligase, primer removal enzyme, and several DNA recombination-related enzymes, have been identified. In the reference Eudicot plant Arabidopsis thaliana, the replication-related enzymes of plastids and mitochondria are similar because many of them are dual targeted to both organelles, whereas in the red alga Cyanidioschyzon merolae, plastids and mitochondria contain different replication machinery components. The enzymes involved in organellar genome replication in green plants and red algae were derived from different origins, including proteobacterial, cyanobacterial, and eukaryotic lineages. In the present review, we summarize the available data for enzymes related to organellar genome replication in green plants and red algae. In addition, based on the type and distribution of replication enzymes in photosynthetic eukaryotes, we discuss the transitional history of replication enzymes in the organelles of plants.

Impact of nitrophenols on the photosynthetic electron transport chain and ATP content in Nostoc muscorum and Chlorella vulgaris.

PubMed

Umamaheswari, A; Venkateswarlu, K

2004-06-01

Concentration-dependent inhibition of the photosynthetic electron transport chain (photosystem I (PS I), photosystem II (PS II) and whole chain reaction) and ATP content was observed in Nostoc muscorum and Chlorella vulgaris grown with o-nitrophenol, m-nitrophenol, or 2,4-dinitrophenol. Although the extents of inhibition of the photosynthetic electron transport chain in both organisms were similar, PS II was more sensitive than PS I and whole chain reaction to the nitrophenols. Depletion of the ATP pool was noted in nitrophenol-grown cultures, probably as a consequence of nearly complete inhibition of the photosynthetic electron transport chain.

Understanding the interaction between an obligate hyperparasitic bacterium, Pasteuria penetrans and its obligate plant-parasitic nematode host, Meloidogyne spp.

PubMed

Davies, Keith G

2009-01-01

Pasteuria penetrans is an endospore-forming bacterium, which is a hyperparasite of root-knot nematodes Meloidogyne spp. that are economically important pests of a wide range of crops. The life cycle of the bacterium and nematode are described with emphasis on the bacterium's potential as a biocontrol agent. Two aspects that currently prohibit the commercial development of the bacterium as a biocontrol agent are the inability to culture it outside its host and its host specificity. Vegetative growth of the bacterium is possible in vitro; however, getting the vegetative stages of the bacterium to enter sporogenesis has been problematic. Insights from genomic survey sequences regarding the role of cation concentration and the phosphorylation of Spo0F have proved useful in inducing vegetative bacteria to sporulate. Similarly, genomic data have also proved useful in understanding the attachment of endospores to the cuticle of infective nematode juveniles, and a Velcro-like model of spore attachment is proposed that involves collagen-like fibres on the surface of the endospore interacting with mucins on the nematode cuticle. Ecological studies of the interactions between Daphnia and Pasteuria ramosa are examined and similarities are drawn between the co-evolution of virulence in the Daphnia system and that of plant-parasitic nematodes.

Description of a bacterium associated with redmouth disease of rainbow trout (Salmo gairdneri)

USGS Publications Warehouse

Ross, A.J.; Rucker, R.R.; Ewing, W.H.

1966-01-01

A description was given of a gram-negative, peritrichously flagellated, fermentative bacterium that was isolated on numerous occasions from kidney tissues of rainbow trout (Salmo gairdneri) afflicted with redmouth disease. Although the bacteria apparently were members of the family Enterobacteriaceae, it was impossible to determine their taxonomic position within the family with certainty. Hence it was recommended that their taxonomic position remain sub judice for the present. As a temporary designation RM bacterium was used. Redmouth disease was transmitted from infected to normal fish through the medium of water.

A Sabbatical Journey into the Microbial World.

ERIC Educational Resources Information Center

Lundgren, Linda

1991-01-01

Presents research results on photosynthetic, carbon monoxide utilizing bacteria. Discusses applications of the research and offers three sets of experimental procedures and data that students analyze to determine which bacterium from a soil sample uses carbon monoxide fastest. (Contains 21 references.) (MDH)

[Effects of lead stress on net photosynthetic rate, SPAD value and ginsenoside production in Ginseng (Panax ginseng)].

PubMed

Liang, Yao; Jiang, Xiao-Li; Yang, Fen-Tuan; Cao, Qing-Jun; Li, Gang

2014-08-01

The paper aimed to evaluate the effects of lead stress on photosynthetic performance and ginsenoside content in ginseng (Panax ginseng). To accomplish this, three years old ginseng were cultivated in pot and in phytotron with different concentrations of lead, ranging from 0 to 1000 mg x kg(-1) soil for a whole growth period (about 150 days). The photosynthetic parameters in leaves and ginsenoside content in roots of ginseng were determined in green fruit stage and before withering stage, respectively. In comparison with the control, net photosynthetic rate and SPAD value in ginseng leaves cultivated with 100 and 250 mg x kg(-1) of lead changed insignificantly, however, ginseng supplied with 500 and 1 000 mg x kg(-1) of lead showed a noticeably decline in the net rate of photosynthesis and SPAD value (P < 0.05), the lowest net photosynthetic rate and SPAD value showed in the treatment supplied with 1 000 mg x kg(-1) of lead, with decline of 57.8%,11.0%, respectively. Total content of ginsenoside in ginseng roots cultivated with 100 mg x kg(-1) of lead showed insignificantly change compared to the control, but the content increased remarkably in treatments supplied with 250, 500, 1 000 mg x kg(-1) of lead (P < 0.05), and highest content appeared in these ginsengs exposed to 1000 mg x kg(-1) of lead. The net photosynthetic rate and SPAD value in leaves of ginseng both showed significantly negative linear correlations with lead stress level (P < 0.01), and significant positive linear correlations between total content of ginsenoside and lead concentration was also observed (P < 0.05). These results strongly indicate that exposing to high level of lead negatively affects photosynthetic performance in ginseng leaves, but benefits for accumulation of secondary metabolism (total content of ginsenoside) in ginseng root.

Cadherin Domains in the Polysaccharide-Degrading Marine Bacterium Saccharophagus degradans 2-40 Are Carbohydrate-Binding Modules▿

PubMed Central

Fraiberg, Milana; Borovok, Ilya; Bayer, Edward A.; Weiner, Ronald M.; Lamed, Raphael

2011-01-01

The complex polysaccharide-degrading marine bacterium Saccharophagus degradans strain 2-40 produces putative proteins that contain numerous cadherin and cadherin-like domains involved in intercellular contact interactions. The current study reveals that both domain types exhibit reversible calcium-dependent binding to different complex polysaccharides which serve as growth substrates for the bacterium. PMID:21036994

Thylakoid-Deposited Micro-Pillar Electrodes for Enhanced Direct Extraction of Photosynthetic Electrons

PubMed Central

Ryu, DongHyun; Kim, Yong Jae; Kim, Seon Il; Hong, Hyeonaug; Ahn, Hyun S.

2018-01-01

Photosynthesis converts solar energy to electricity in a highly efficient manner. Since only water is needed as fuel for energy conversion, this highly efficient energy conversion process has been rigorously investigated. In particular, photosynthetic apparatus, such as photosystem II (PSII), photosystem I (PSI), or thylakoids, have been isolated from various plants to construct bio-hybrid anodes. Although PSII or PSI decorated anodes have shown potentials, there still remain challenges, such as poor stability of PSII-based systems or need for electron donors other than water molecules of PSI-based systems. Thylakoid membranes are relatively stable after isolation and they contain all the necessary photosynthetic apparatus including the PSII and PSI. To increase electrical connections between thylakoids and anodes, nanomaterials such as carbon nanotubes, nanowires, nanoparticles, or graphene have been employed. However, since they rely on the secondary electrical connections between thylakoids and anodes; it is desired to achieve larger direct contacts between them. Here, we aimed to develop micro-pillar (MP) array anodes to maximize direct contact with thylakoids. The thylakoid morphology was analyzed and the MP array was designed to maximize direct contact with thylakoids. The performance of MP anodes and a photosynthetic fuel cell based on MP electrodes was demonstrated and analyzed. PMID:29587387

Photosynthetic and Biochemical Changes in Response to Short Interval High ``g'' Exposure in Wheat

NASA Astrophysics Data System (ADS)

Dixit, Jyotsana; Vidyasagar, Pandit; Jagtap, Sagar; Kamble, Shailendra

We have investigated the effect of short interval post imbibition high “g” exposure on wheat seeds (Triticum aestivum var.Lok-1) by evaluating the photosynthetic performance, chlorophyll “a” fluorescence biochemical indices and antioxidant response. Imbibed wheat seeds were exposed to high “g” ranging from 500 g to 2500 g for 10 min, allowed to germinate and grown for 5 days under normal gravity i.e. 1 g. Chlorophyll “a” fluorescence transient was examined in wheat seedling raised from hyper gravity treated seeds. Fv/Fm, PI, Fv/Fo decreased in high “g” treated seeds compared to control. Photosynthetic performance indices such as Transpiration rate, Stomatal conductance, Net photosynthetic rate, Intracellular CO2 concentration, Intrinsic water use efficiency also declined in wheat seedlings raised from High “g” treated seeds suggesting that high g reduces efficiency of photosynthesis in wheat seedlings. Results of Biochemical analysis showed reduced alpha- amylase activity in wheat seeds subjected to high “g” ranging from 500 g to 2500 g in a magnitude dependent manner. Decline in enzyme activity was positively correlated with higher starch content and lower reducing sugars in high “g” exposed wheat seeds. This possibly explains the reduced percent germination and growth in response to high “g”. Antioxidant enzyme activity (CAT and POX) significantly increased as a result of hypergravity exposure In conclusion, short interval high “g” exposure results in reduced growth and photosynthetic activity in wheat seedlings.

Complete Genome Sequence of a thermotolerant sporogenic lactic acid bacterium, Bacillus coagulans strain 36D1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rhee, Mun Su; Moritz, Brelan E.; Xie, Gary

Bacillus coagulans is a ubiquitous soil bacterium that grows at 50-55 C and pH 5.0 and fer- ments various sugars that constitute plant biomass to L (+)-lactic acid. The ability of this spo- rogenic lactic acid bacterium to grow at 50-55 C and pH 5.0 makes this organism an attrac- tive microbial biocatalyst for production of optically pure lactic acid at industrial scale not only from glucose derived from cellulose but also from xylose, a major constituent of hemi- cellulose. This bacterium is also considered as a potential probiotic. Complete genome se- quence of a representative strain, B. coagulans strainmore » 36D1, is presented and discussed.« less

Complete Genome Sequence of a thermotolerant sporogenic lactic acid bacterium, Bacillus coagulans strain 36D1

PubMed Central

Rhee, Mun Su; Moritz, Brélan E.; Xie, Gary; Glavina del Rio, T.; Dalin, E.; Tice, H.; Bruce, D.; Goodwin, L.; Chertkov, O.; Brettin, T.; Han, C.; Detter, C.; Pitluck, S.; Land, Miriam L.; Patel, Milind; Ou, Mark; Harbrucker, Roberta; Ingram, Lonnie O.; Shanmugam, K. T.

2011-01-01

Bacillus coagulans is a ubiquitous soil bacterium that grows at 50-55 °C and pH 5.0 and ferments various sugars that constitute plant biomass to L (+)-lactic acid. The ability of this sporogenic lactic acid bacterium to grow at 50-55 °C and pH 5.0 makes this organism an attractive microbial biocatalyst for production of optically pure lactic acid at industrial scale not only from glucose derived from cellulose but also from xylose, a major constituent of hemicellulose. This bacterium is also considered as a potential probiotic. Complete genome sequence of a representative strain, B. coagulans strain 36D1, is presented and discussed. PMID:22675583

Calibration of the Odyssey Photosynthetic Irradiance Recorder for Absolute Irradiance Measures

EPA Science Inventory

Researchers are increasingly interested in measuring hotosynthetically active radiation (PAR) because of its importance in determining the structure and function of lotic ecosystems. The Odyssey Photosynthetic Irradiance Recorder is an affordable PAR meter gaining popularity am...

Paradigms: examples from the bacterium Xylella fastidiosa.

PubMed

Purcell, Alexander

2013-01-01

The history of advances in research on Xylella fastidiosa provides excellent examples of how paradigms both advance and limit our scientific understanding of plant pathogens and the plant diseases they cause. I describe this from a personal perspective, having been directly involved with many persons who made paradigm-changing discoveries, beginning with the discovery that a bacterium, not a virus, causes Pierce's disease of grape and other plant diseases in numerous plant species, including important crop and forest species.

Metabolic flux analysis of the mixotrophic metabolisms in the green sulfur bacterium Chlorobaculum tepidum.

PubMed

Feng, Xueyang; Tang, Kuo-Hsiang; Blankenship, Robert E; Tang, Yinjie J

2010-12-10

The photosynthetic green sulfur bacterium Chlorobaculum tepidum assimilates CO(2) and organic carbon sources (acetate or pyruvate) during mixotrophic growth conditions through a unique carbon and energy metabolism. Using a (13)C-labeling approach, this study examined biosynthetic pathways and flux distributions in the central metabolism of C. tepidum. The isotopomer patterns of proteinogenic amino acids revealed an alternate pathway for isoleucine synthesis (via citramalate synthase, CimA, CT0612). A (13)C-assisted flux analysis indicated that carbons in biomass were mostly derived from CO(2) fixation via three key routes: the reductive tricarboxylic acid (RTCA) cycle, the pyruvate synthesis pathway via pyruvate:ferredoxin oxidoreductase, and the CO(2)-anaplerotic pathway via phosphoenolpyruvate carboxylase. During mixotrophic growth with acetate or pyruvate as carbon sources, acetyl-CoA was mainly produced from acetate (via acetyl-CoA synthetase) or citrate (via ATP citrate lyase). Pyruvate:ferredoxin oxidoreductase converted acetyl-CoA and CO(2) to pyruvate, and this growth-rate control reaction is driven by reduced ferredoxin generated during phototrophic growth. Most reactions in the RTCA cycle were reversible. The relative fluxes through the RTCA cycle were 80∼100 units for mixotrophic cultures grown on acetate and 200∼230 units for cultures grown on pyruvate. Under the same light conditions, the flux results suggested a trade-off between energy-demanding CO(2) fixation and biomass growth rate; C. tepidum fixed more CO(2) and had a higher biomass yield (Y(X/S), mole carbon in biomass/mole substrate) in pyruvate culture (Y(X/S) = 9.2) than in acetate culture (Y(X/S) = 6.4), but the biomass growth rate was slower in pyruvate culture than in acetate culture.

Growth, photosynthetic acclimation and yield quality in legumes under climate change simulations: an updated survey.

PubMed

Irigoyen, J J; Goicoechea, N; Antolín, M C; Pascual, I; Sánchez-Díaz, M; Aguirreolea, J; Morales, F

2014-09-01

Continued emissions of CO2, derived from human activities, increase atmospheric CO2 concentration. The CO2 rise stimulates plant growth and affects yield quality. Effects of elevated CO2 on legume quality depend on interactions with N2-fixing bacteria and mycorrhizal fungi. Growth at elevated CO2 increases photosynthesis under short-term exposures in C3 species. Under long-term exposures, however, plants generally acclimate to elevated CO2 decreasing their photosynthetic capacity. An updated survey of the literature indicates that a key factor, perhaps the most important, that characteristically influences this phenomenon, its occurrence and extent, is the plant source-sink balance. In legumes, the ability of exchanging C for N at nodule level with the N2-fixing symbionts creates an extra C sink that avoids the occurrence of photosynthetic acclimation. Arbuscular mycorrhizal fungi colonizing roots may also result in increased C sink, preventing photosynthetic acclimation. Defoliation (Anthyllis vulneraria, simulated grazing) or shoot cutting (alfalfa, usual management as forage) largely increases root/shoot ratio. During re-growth at elevated CO2, new shoots growth and nodule respiration function as strong C sinks that counteracts photosynthetic acclimation. In the presence of some limiting factor, the legumes response to elevated CO2 is weakened showing photosynthetic acclimation. This survey has identified limiting factors that include an insufficient N supply from bacterial strains, nutrient-poor soils, low P supply, excess temperature affecting photosynthesis and/or nodule activity, a genetically determined low nodulation capacity, an inability of species or varieties to increase growth (and therefore C sink) at elevated CO2 and a plant phenological state or season when plant growth is stopped. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Photoautotrophic Culture of Coffea arabusta Somatic Embryos: Photosynthetic Ability and Growth of Different Stage Embryos

PubMed Central

AFREEN, F.; ZOBAYED, S. M. A.; KOZAI, T.

2002-01-01

Coffea arabusta somatic embryos were cultured and development of stomata, rate of CO2 fixation or production, chlorophyll content and chlorophyll fluorescence were studied in embryos at different stages of development. Cotyledonary and germinated embryos have photosynthetic capacity, although pretreatment at a high photosynthetic photon flux (PPF) (100 µmol m–2 s–1) for 14 d increased photosynthetic ability. Except in a very small number of cases, stomata did not develop fully in precotyledonary stage embryos and were absent in torpedo stage embryos. Low chlorophyll content (90–130 µg g–1 fresh mass) was noted in torpedo and precotyledonary stage embryos compared with cotyledonary and germinated embryos (300–500 µg g–1 fresh mass). Due to the absence of stomata and low chlorophyll content in the torpedo and precotyledonary stage embryos, the photosynthetic rate was low and, in some cases, CO2 production was observed. These data suggest that the cotyledonary stage is the earliest stage that can be cultured photoautotrophically to ensure plantlet development. When grown photoautotrophically (in a sugar‐free medium with CO2 enrichment in the culture headspace and high photosynthetic photon flux), torpedo and precotyledonary stage embryos lost 20–25 % of their initial dry mass after 60 d of culture. However, in cotyledonary and germinated embryos, the dry mass of each embryo increased by 10 and 50 %, respectively. By using a porous supporting material, growth (especially root growth) was increased in cotyledonary stage embryos. In addition, photoautotrophic conditions, high PPF (100–150 µmol m–2 s–1) and increased CO2 concentration (1100 µmol mol–1) were found to be necessary for the development of plantlets from cotyledonary stage embryos. PMID:12125763

Biomaterials based on photosynthetic membranes as potential sensors for herbicides.

PubMed

Ventrella, Andrea; Catucci, Lucia; Placido, Tiziana; Longobardi, Francesco; Agostiano, Angela

2011-08-15

In this study, ultrathin film multilayers of Photosystem II-enriched photosynthetic membranes (BBY) were prepared and immobilized on quartz substrates by means of a Layer by Layer procedure exploiting electrostatic interactions with poly(ethylenimine) as polyelectrolyte. The biomaterials thus obtained were characterized by means of optical techniques and Atomic Force Microscopy, highlighting the fact that the Layer by Layer approach allowed the BBYs to be immobilized with satisfactory results. The activity of these hybrid materials was evaluated by means of optical assays based on the Hill Reaction, indicating that the biosamples, which preserved about 65% of their original activity even ten weeks after preparation, were both stable and active. Furthermore, an investigation of the biochips' sensitivity to the herbicide terbutryn, as a model analyte, gave interesting results: inhibition of photosynthetic activity was observed at terbutryn concentrations higher than 10(-7)M, thus evidencing the potential of such biomaterials in the environmental biosensor field. Copyright © 2011 Elsevier B.V. All rights reserved.

Changes of Photosynthetic Behaviors in Kappaphycus alvarezii Infected by Epiphyte.

PubMed

Pang, Tong; Liu, Jianguo; Liu, Qian; Lin, Wei

2011-01-01

Epiphytic filamentous algae (EFA) were noted as a serious problem to reduce the production and quality of K. alvarezii. The morphological studies revealed that the main epiphyte on K. alvarezii was Neosiphonia savatieri in China. Though the harmful effects of EFA on the production of K. alvarezii have been reported, the detailed mechanism of the N. savatieri in limiting the production of K. alvarezii has not been studied yet. The present paper studied the effects of N. savatieri infection on photosynthetic behaviors in K. alvarezii by detecting chlorophyll fluorescence transient in vivo. The results revealed that damage of oxygen-evolving complex (OEC), decrease of active reaction centers (RCs), and the plastoquinone (PQ) pool as well as significant reduction in the performance indexes (PI) of PSII were caused by the infection of N. savatieri. The influence of N. savatieri on photosynthetic activity of K. alvarezii should be one of the important reasons to reduce the production of K. alvarezii infected by N. savatieri.

Changes of Photosynthetic Behaviors in Kappaphycus alvarezii Infected by Epiphyte

PubMed Central

Pang, Tong; Liu, Jianguo; Liu, Qian; Lin, Wei

2011-01-01

Epiphytic filamentous algae (EFA) were noted as a serious problem to reduce the production and quality of K. alvarezii. The morphological studies revealed that the main epiphyte on K. alvarezii was Neosiphonia savatieri in China. Though the harmful effects of EFA on the production of K. alvarezii have been reported, the detailed mechanism of the N. savatieri in limiting the production of K. alvarezii has not been studied yet. The present paper studied the effects of N. savatieri infection on photosynthetic behaviors in K. alvarezii by detecting chlorophyll fluorescence transient in vivo. The results revealed that damage of oxygen-evolving complex (OEC), decrease of active reaction centers (RCs), and the plastoquinone (PQ) pool as well as significant reduction in the performance indexes (PI) of PSII were caused by the infection of N. savatieri. The influence of N. savatieri on photosynthetic activity of K. alvarezii should be one of the important reasons to reduce the production of K. alvarezii infected by N. savatieri. PMID:21845201

Worldwide variation in within-canopy photosynthetic acclimation: differences in temporal and environmental controls among plant functional types

NASA Astrophysics Data System (ADS)

Niinemets, Ülo; Keenan, Trevor

2017-04-01

Major light gradients, characteristically 10- to 50-fold, constitute the most prominent feature of plant canopies. These gradients drive within-canopy variation in foliage structural, chemical and physiological traits. As a key acclimation response to variation in light availability, foliage photosynthetic capacity per area (Aarea) increases with increasing light availability within the canopy, maximizing whole canopy photosynthesis. Recently, a worldwide database including 831 within-canopy gradients with standardized light estimates for 304 species belonging to major vascular plant functional types was constructed and within-canopy variation in photosynthetic acclimation was characterized (Niinemets Ü, Keenan TF, Hallik L (2015) Tansley review. A worldwide analysis of within-canopy variations in leaf structural, chemical and physiological traits across plant functional types. The New Phytologist 205: 973-993). However, the understanding of how within-canopy photosynthetic gradients vary during the growing season and in response to site and stand characteristics is still limited. Here we analyzed temporal, environmental and site (nutrient availability, stand density, ambient CO2 concentration, water availability) sources of variation in within-canopy photosynthetic acclimation in different plant functional types. Variation in key structural (leaf dry mass per unit area, MA), chemical (nitrogen content per dry mass, NM, and area, NA) and physiological (photosynthetic nitrogen use efficiency, EN) photosynthetic capacity per dry mass, Amass and area, Aarea) was examined. The analysis demonstrates major, typically 1.5-2-fold, time-, environment and site-dependent modifications in within-canopy variation in foliage photosynthetic capacity. However, the magnitude and direction of temporal and environmental variations in plasticity significantly varied among functional types. Species with longer leaf life span and low rates of canopy expansion or flush-type canopy

Progress in Remote Sensing of Photosynthetic Activity over the Amazon Basin

NASA Technical Reports Server (NTRS)

Resende de Sousa, Celio Helder; Hilker, Thomas; Waring, Richard; Mendes De Moura, Yhasmin; Lyapustin, Alexei

2017-01-01

Although quantifying the massive exchange of carbon that takes place over the Amazon Basin remains a challenge, progress is being made as the remote sensing community moves from using traditional, reflectance-based vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), to the more functional Photochemical Reflectance Index (PRI). This new index, together with satellite-derived estimates of canopy light interception and Sun-Induced Fluorescence (SIF), provide improved estimates of Gross Primary Production (GPP). This paper traces the development of these new approaches, compares the results of their analyses from multiple years of data acquired across the Amazon Basin and suggests further improvements in instrument design, data acquisition and processing. We demonstrated that our estimates of PRI are in generally good agreement with eddy-flux tower measurements of photosynthetic light use efficiency (epsilon) at four sites in the Amazon Basin: r(exp 2) values ranged from 0.37 to 0.51 for northern flux sites and to 0.78for southern flux sites. This is a significant advance over previous approaches seeking to establish a link between global-scale photosynthetic activity and remotely-sensed data. When combined with measurements of Sun-Induced Fluorescence (SIF), PRI provides realistic estimates of seasonal variation in photosynthesis over the Amazon that relate well to the wet and dry seasons. We anticipate that our findings will steer the development of improved approaches to estimate photosynthetic activity over the tropics.

Progress in Remote Sensing of Photosynthetic Activity over the Amazon Basin

PubMed Central

de Sousa, Celio Helder Resende; Hilker, Thomas; Waring, Richard; de Moura, Yhasmin Mendes; Lyapustin, Alexei

2017-01-01

Although quantifying the massive exchange of carbon that takes place over the Amazon Basin remains a challenge, progress is being made as the remote sensing community moves from using traditional, reflectance-based vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), to the more functional Photochemical Reflectance Index (PRI). This new index, together with satellite-derived estimates of canopy light interception and Sun-Induced Fluorescence (SIF), provide improved estimates of Gross Primary Production (GPP). This paper traces the development of these new approaches, compares the results of their analyses from multiple years of data acquired across the Amazon Basin and suggests further improvements in instrument design, data acquisition and processing. We demonstrated that our estimates of PRI are in generally good agreement with eddy-flux tower measurements of photosynthetic light use efficiency (ε) at four sites in the Amazon Basin: r2 values ranged from 0.37 to 0.51 for northern flux sites and to 0.78 for southern flux sites. This is a significant advance over previous approaches seeking to establish a link between global-scale photosynthetic activity and remotely-sensed data. When combined with measurements of Sun-Induced Fluorescence (SIF), PRI provides realistic estimates of seasonal variation in photosynthesis over the Amazon that relate well to the wet and dry seasons. We anticipate that our findings will steer the development of improved approaches to estimate photosynthetic activity over the tropics. PMID:29375895

Progress in Remote Sensing of Photosynthetic Activity over the Amazon Basin.

PubMed

de Sousa, Celio Helder Resende; Hilker, Thomas; Waring, Richard; de Moura, Yhasmin Mendes; Lyapustin, Alexei

2017-01-01

Although quantifying the massive exchange of carbon that takes place over the Amazon Basin remains a challenge, progress is being made as the remote sensing community moves from using traditional, reflectance-based vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), to the more functional Photochemical Reflectance Index (PRI). This new index, together with satellite-derived estimates of canopy light interception and Sun-Induced Fluorescence (SIF), provide improved estimates of Gross Primary Production (GPP). This paper traces the development of these new approaches, compares the results of their analyses from multiple years of data acquired across the Amazon Basin and suggests further improvements in instrument design, data acquisition and processing. We demonstrated that our estimates of PRI are in generally good agreement with eddy-flux tower measurements of photosynthetic light use efficiency (ε) at four sites in the Amazon Basin: r 2 values ranged from 0.37 to 0.51 for northern flux sites and to 0.78 for southern flux sites. This is a significant advance over previous approaches seeking to establish a link between global-scale photosynthetic activity and remotely-sensed data. When combined with measurements of Sun-Induced Fluorescence (SIF), PRI provides realistic estimates of seasonal variation in photosynthesis over the Amazon that relate well to the wet and dry seasons. We anticipate that our findings will steer the development of improved approaches to estimate photosynthetic activity over the tropics.

Managing the cellular redox hub in photosynthetic organisms.

PubMed

Foyer, Christine H; Noctor, Graham

2012-02-01

Light-driven redox chemistry is a powerful source of redox signals that has a decisive input into transcriptional control within the cell nucleus. Like photosynthetic electron transport pathways, the respiratory electron transport chain exerts a profound control over gene function, in order to balance energy (reductant and ATP) supply with demand, while preventing excessive over-reduction or over-oxidation that would be adversely affect metabolism. Photosynthetic and respiratory redox chemistries are not merely housekeeping processes but they exert a controlling influence over every aspect of plant biology, participating in the control of gene transcription and translation, post-translational modifications and the regulation of assimilatory reactions, assimilate partitioning and export. The number of processes influenced by redox controls and signals continues to increase as do the components that are recognized participants in the associated signalling pathways. A step change in our understanding of the overall importance of the cellular redox hub to plant cells has occurred in recent years as the complexity of the management of the cellular redox hub in relation to metabolic triggers and environmental cues has been elucidated. This special issue describes aspects of redox regulation and signalling at the cutting edge of current research in this dynamic and rapidly expanding field. © 2011 Blackwell Publishing Ltd.

Atomic Detail Visualization of Photosynthetic Membranes with GPU-Accelerated Ray Tracing

PubMed Central

Vandivort, Kirby L.; Barragan, Angela; Singharoy, Abhishek; Teo, Ivan; Ribeiro, João V.; Isralewitz, Barry; Liu, Bo; Goh, Boon Chong; Phillips, James C.; MacGregor-Chatwin, Craig; Johnson, Matthew P.; Kourkoutis, Lena F.; Hunter, C. Neil

2016-01-01

The cellular process responsible for providing energy for most life on Earth, namely photosynthetic light-harvesting, requires the cooperation of hundreds of proteins across an organelle, involving length and time scales spanning several orders of magnitude over quantum and classical regimes. Simulation and visualization of this fundamental energy conversion process pose many unique methodological and computational challenges. We present, in two accompanying movies, light-harvesting in the photosynthetic apparatus found in purple bacteria, the so-called chromatophore. The movies are the culmination of three decades of modeling efforts, featuring the collaboration of theoretical, experimental, and computational scientists. We describe the techniques that were used to build, simulate, analyze, and visualize the structures shown in the movies, and we highlight cases where scientific needs spurred the development of new parallel algorithms that efficiently harness GPU accelerators and petascale computers. PMID:27274603

Atomic detail visualization of photosynthetic membranes with GPU-accelerated ray tracing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stone, John E.; Sener, Melih; Vandivort, Kirby L.

The cellular process responsible for providing energy for most life on Earth, namely, photosynthetic light-harvesting, requires the cooperation of hundreds of proteins across an organelle, involving length and time scales spanning several orders of magnitude over quantum and classical regimes. Simulation and visualization of this fundamental energy conversion process pose many unique methodological and computational challenges. We present, in two accompanying movies, light-harvesting in the photosynthetic apparatus found in purple bacteria, the so-called chromatophore. The movies are the culmination of three decades of modeling efforts, featuring the collaboration of theoretical, experimental, and computational scientists. We describe the techniques that weremore » used to build, simulate, analyze, and visualize the structures shown in the movies, and we highlight cases where scientific needs spurred the development of new parallel algorithms that efficiently harness GPU accelerators and petascale computers.« less

A novel strategy for acetonitrile wastewater treatment by using a recombinant bacterium with biofilm-forming and nitrile-degrading capability.

PubMed

Li, Chunyan; Yue, Zhenlei; Feng, Fengzhao; Xi, Chuanwu; Zang, Hailian; An, Xuejiao; Liu, Keran

2016-10-01

There is a great need for efficient acetonitrile removal technology in wastewater treatment to reduce the discharge of this pollutant in untreated wastewater. In this study, a nitrilase gene (nit) isolated from a nitrile-degrading bacterium (Rhodococcus rhodochrous BX2) was cloned and transformed into a biofilm-forming bacterium (Bacillus subtilis N4) that expressed the recombinant protein upon isopropylthio-β-galactoside (IPTG) induction. The recombinant bacterium (B. subtilis N4-pHT01-nit) formed strong biofilms and had nitrile-degrading capability. Further testing demonstrated that biofilms formed by B. subtilis N4-pHT01-nit were highly resistant to loading shock from acetonitrile and almost completely degraded the initial concentration of acetonitrile (800 mg L(-1)) within 24 h in a moving bed biofilm reactor (MBBR) after operation for 35 d. The bacterial composition of the biofilm, identified by high-throughput sequencing, in a reactor in which the B. subtilis N4-pHT01-nit bacterium was introduced indicated that the engineered bacterium was successfully immobilized in the reactor and became dominant genus. This work demonstrates that an engineered bacterium with nitrile-degrading and biofilm-forming capacity can improve the degradation of contaminants in wastewater. This approach offers a novel strategy for enhancing the biological oxidation of toxic pollutants in wastewater. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Rhodobaculum claviforme gen. nov., sp. nov., a New Alkaliphilic Nonsulfur Purple Bacterium].

PubMed

Bryantseva, I A; Gaisin, V A; Gorlenko, V M

2015-01-01

Two alkaliphilic strains of nonsulfur purple bacteria (NPB), B7-4 and B8-2, were isolated from southeast Siberia moderately saline alkaline steppe lakes with pH values above 9.0. The isolates were motile, polymorphous cells (from short rods to long spindly cells) 2.0-3.2 x 9.6-20.0 μm. Intracellular membranes of vesicular type were mostly located at the cell periphery. The microorganisms contained bacteriochlorophyll a and carotenoids of the spheroidene and spirilloxanthin series. The photosynthetic apparatus was represented by LH2 and LH1 light-harvesting complexes. In the presence of organic compounds, the strains grew aerobically in the dark or anaerobically in the light. Capacity for photo- and chemoautotrophic growth was not detected. The cbbl gene encoding RuBisCO was not revealed. Optimal growth of both strains occurred at 2% NaCl (range from 0.5 to 4%), pH 8.0-8.8 (range from 7.5 to 9.7), and 25-35 degrees C. The DNA G+C content was 67.6-69.8 mol %. Pairwise comparison of the nucleotides of the 16S rRNA genes revealed that strains B7-4 and B8-2 belonged to the same species (99.9% homology) and were most closely related to the aerobic alkaliphilic bacteriochlorophyll a-containing anoxygenic phototrophic bacterium (APB) Roseibacula alcaliphilum De (95.2%) and to NPB strains Rhodobaca barguzinensis VKM B-2406(T) (94.2%) and Rbc. bogoriensis LBB1(T) (93.9%). The isolates were closely related to the NPB Rhodobacter veldkampii DSM 11550(T) (94.8%) and to aerobic bacteriochlorophyll a-containing bacteria Roseinatronobacter monicus ROS 35(T) and Roseicitreum antarcticul ZS2-28(T) (93.5 and 93.9%, respectively). New strains were described as a new NPB genus and species of the family Rhodobacteriaceae, Rhodobaculum claviforme gen. nov., sp. nov., with B7-4(T) (VKM B-2708, LMG 28126) as the type strain.

Estimation of Whole Plant Photosynthetic Rate of Irwin Mango under Artificial and Natural Lights Using a Three-Dimensional Plant Model and Ray-Tracing.

PubMed

Jung, Dae Ho; Lee, Joon Woo; Kang, Woo Hyun; Hwang, In Ha; Son, Jung Eek

2018-01-04

Photosynthesis is an important physiological response for determination of CO₂ fertilization in greenhouses and estimation of crop growth. In order to estimate the whole plant photosynthetic rate, it is necessary to investigate how light interception by crops changes with environmental and morphological factors. The objectives of this study were to analyze plant light interception using a three-dimensional (3D) plant model and ray-tracing, determine the spatial distribution of the photosynthetic rate, and estimate the whole plant photosynthetic rate of Irwin mango ( Mangifera indica L. cv. Irwin) grown in greenhouses. In the case of mangoes, it is difficult to measure actual light interception at the canopy level due to their vase shape. A two-year-old Irwin mango tree was used to measure the whole plant photosynthetic rate. Light interception and whole plant photosynthetic rate were measured under artificial and natural light conditions using a closed chamber (1 × 1 × 2 m). A 3D plant model was constructed and ray-tracing simulation was conducted for calculating the photosynthetic rate with a two-variable leaf photosynthetic rate model of the plant. Under artificial light, the estimated photosynthetic rate increased from 2.0 to 2.9 μmolCO₂·m -2 ·s -1 with increasing CO₂ concentration. On the other hand, under natural light, the photosynthetic rate increased from 0.2 μmolCO₂·m -2 ·s -1 at 06:00 to a maximum of 7.3 μmolCO₂·m -2 ·s -1 at 09:00, then gradually decreased to -1.0 μmolCO₂·m -2 ·s -1 at 18:00. In validation, simulation results showed good agreement with measured results with R ² = 0.79 and RMSE = 0.263. The results suggest that this method could accurately estimate the whole plant photosynthetic rate and be useful for pruning and adequate CO₂ fertilization.

Genome Sequence of Lactobacillus delbrueckii subsp. lactis CNRZ327, a Dairy Bacterium with Anti-Inflammatory Properties.

PubMed

El Kafsi, Hela; Binesse, Johan; Loux, Valentin; Buratti, Julien; Boudebbouze, Samira; Dervyn, Rozenn; Hammani, Amal; Maguin, Emmanuelle; van de Guchte, Maarten

2014-07-17

Lactobacillus delbrueckii subsp. lactis CNRZ327 is a dairy bacterium with anti-inflammatory properties both in vitro and in vivo. Here, we report the genome sequence of this bacterium, which appears to contain no less than 215 insertion sequence (IS) elements, an exceptionally high number regarding the small genome size of the strain. Copyright © 2014 El Kafsi et al.

Chitin utilization by the insect-transmitted bacterium Xylella fastidiosa.

PubMed

Killiny, Nabil; Prado, Simone S; Almeida, Rodrigo P P

2010-09-01

Xylella fastidiosa is an insect-borne bacterium that colonizes xylem vessels of a large number of host plants, including several crops of economic importance. Chitin is a polysaccharide present in the cuticle of leafhopper vectors of X. fastidiosa and may serve as a carbon source for this bacterium. Biological assays showed that X. fastidiosa reached larger populations in the presence of chitin. Additionally, chitin induced phenotypic changes in this bacterium, notably increasing adhesiveness. Quantitative PCR assays indicated transcriptional changes in the presence of chitin, and an enzymatic assay demonstrated chitinolytic activity by X. fastidiosa. An ortholog of the chitinase A gene (chiA) was identified in the X. fastidiosa genome. The in silico analysis revealed that the open reading frame of chiA encodes a protein of 351 amino acids with an estimated molecular mass of 40 kDa. chiA is in a locus that consists of genes implicated in polysaccharide degradation. Moreover, this locus was also found in the genomes of closely related bacteria in the genus Xanthomonas, which are plant but not insect associated. X. fastidiosa degraded chitin when grown on a solid chitin-yeast extract-agar medium and grew in liquid medium with chitin as the sole carbon source; ChiA was also determined to be secreted. The gene encoding ChiA was cloned into Escherichia coli, and endochitinase activity was detected in the transformant, showing that the gene is functional and involved in chitin degradation. The results suggest that X. fastidiosa may use its vectors' foregut surface as a carbon source. In addition, chitin may trigger X. fastidiosa's gene regulation and biofilm formation within vectors. Further work is necessary to characterize the role of chitin and its utilization in X. fastidiosa.

Photosynthetic and stomatal acclimation to elevated CO{sub 2} depends on soil type in Quercus prinus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bunce, J.A.

1995-06-01

Quercus prinus (L.) seedlings grown outdoors at ambient and elevated (ambient + 350 ppm) CO{sub 2} with a fertile soil had no photosynthetic acclimation to elevated CO{sub 2} and no stomatal response to growth or measurement CO{sub 2}. In contrast, seedlings grown with soil collected from a Q. prinus stand had photosynthetic and stomatal acclimation, and stomatal conductance was sensitive to measurement CO{sub 2}. In plants grown with the native soil, light-saturated stomatal conductance measured at the growth CO{sub 2} was reduced by 54% at elevated CO{sub 2}, compared to the short-term reduction of 36%. Photosynthetic acclimation in plants grownmore » with the native soil reduced the stimulation of light-saturated photosynthesis at elevated CO{sub 2} from a factor of 1.9 to a factor of 1.3. In contrast to the dependence of photosynthetic and stomatal acclimation on soil type, the response of leaf respiration to elevated CO{sub 2} was the same for both soils. Respiration of leaves was reduced in the elevated CO{sub 2} treatment by 41 % on a leaf area basis. However, this effect was immediately reversible by altering the measurement CO{sub 2}, indicating that no acclimation of respiration occurred.« less

Growth, nutrient status, and photosynthetic response to diesel-contaminated soil of a cordgrass, Spartina argentinensis.

PubMed

Redondo-Gómez, Susana; Petenello, María C; Feldman, Susana R

2014-02-15

The present study was conduced to investigate the tolerance limits of Spartina argentinensis, which occurs in inland marshes of the Chaco-Pampean regions of Argentina, to diesel-contaminated soil. A glasshouse experiment was designed to investigate the effect of diesel fuel from 0% to 3% on growth and photosynthetic apparatus of S. densiflora by measuring gas exchange and photosynthetic pigments. We also performed chemical analysis of plant samples, and determined mycorrhizal index. Tiller and root biomasses declined with increasing diesel fuel concentration, as well as photosynthetic rate (A). Reductions in A could be accounted for by non-stomatal limitations. Mycorrhizal roots of S. argentinensis were reduced by the presence of diesel fuel, but did not affect its nutritional status; in fact, most element concentrations increased with diesel contamination. Despite the negative effect of diesel-contaminated soil, S. argentinensis continued growing, which could be useful management options for phytorremediation of diesel-contaminated soils. Copyright © 2014 Elsevier Ltd. All rights reserved.

Photosynthetic electron partitioning between [FeFe]-hydrogenase and ferredoxin:NADP+-oxidoreductase (FNR) enzymes in vitro

PubMed Central

Yacoby, Iftach; Pochekailov, Sergii; Toporik, Hila; Ghirardi, Maria L.; King, Paul W.; Zhang, Shuguang

2011-01-01

Photosynthetic water splitting, coupled to hydrogenase-catalyzed hydrogen production, is considered a promising clean, renewable source of energy. It is widely accepted that the oxygen sensitivity of hydrogen production, combined with competition between hydrogenases and NADPH-dependent carbon dioxide fixation are the main limitations for its commercialization. Here we provide evidence that, under the anaerobic conditions that support hydrogen production, there is a significant loss of photosynthetic electrons toward NADPH production in vitro. To elucidate the basis for competition, we bioengineered a ferredoxin-hydrogenase fusion and characterized hydrogen production kinetics in the presence of Fd, ferredoxin:NADP+-oxidoreductase (FNR), and NADP+. Replacing the hydrogenase with a ferredoxin-hydrogenase fusion switched the bias of electron transfer from FNR to hydrogenase and resulted in an increased rate of hydrogen photoproduction. These results suggest a new direction for improvement of biohydrogen production and a means to further resolve the mechanisms that control partitioning of photosynthetic electron transport. PMID:21606330

Leaf photosynthetic and water-relations responses for 'Valencia' orange trees exposed to oxidant air pollution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olszyk, D.M.; Takemoto, B.K.; Poe, M.

1991-01-01

Leaf responses were measured to test a hypothesis that reduced photosynthetic capacity and/or altered water relations were associated with reductions in yield for 'Valencia' orange trees (Citrus sinensis (L.), Osbeck) exposed to ambient oxidant air pollution. Exposures were continuous for 4 years to three levels of oxidants (in charcoal-filtered, half-filtered, and non-filtered air). Oxidants had no effect on net leaf photosynthetic rates or on photosynthetic pigment concentrations. A single set of measurements indicated that oxidants increased leaf starch concentrations (24%) prior to flowering, suggesting a change in photosynthate allocation. Leaves exposed to oxidants had small, but consistent, changes in watermore » relations over the summer growing season, compared to trees growing in filtered air. Other changes included decreased stomatal conductance (12%) and transpiration (9%) rates, and increased water pressure potentials (5%). While all responses were subtle, their cumulative impact over 4 years indicated that 'Valencia' orange trees were subject to increased ambient oxidant stress.« less

Complete genome of Martelella sp. AD-3, a moderately halophilic polycyclic aromatic hydrocarbons-degrading bacterium.

PubMed

Cui, Changzheng; Li, Zhijie; Qian, Jiangchao; Shi, Jie; Huang, Ling; Tang, Hongzhi; Chen, Xin; Lin, Kuangfei; Xu, Ping; Liu, Yongdi

2016-05-10

Martelella sp. strain AD-3, a moderate halophilic bacterium, was isolated from a petroleum-contaminated soil with high salinity in China. Here, we report the complete genome of strain AD-3, which contains one circular chromosome and two circular plasmids. An array of genes related to metabolism of polycyclic aromatic hydrocarbons and halophilic mechanism in this bacterium was identified by the whole genome analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Treatment of anaerobically digested swine wastewater by Rhodobacter blasticus and Rhodobacter capsulatus.

PubMed

Wen, Shan; Liu, Hongyu; He, Huijun; Luo, Le; Li, Xiang; Zeng, Guangming; Zhou, Zili; Lou, Wei; Yang, Chunping

2016-12-01

Two strains of photosynthetic bacteria, Rhodobacter blasticus and Rhodobacter capsulatus, were used in this work to investigate the feasibility of using photosynthetic bacteria for the treatment of anaerobically digested swine wastewater. The effects of crucial factors which influence the pollutants removal efficiency were also examined. Results showed that anaerobically digested swine wastewater could be treated effectively by photosynthetic bacteria. The treatment efficiency was significantly higher by the mixed photosynthetic bacteria than that by any unitary bacterium. The optimal treatment condition by mixed bacteria was inoculation of 10.0%(v/v) of the two bacteria by 1:1, initial pH of 7.0 and initial chemical oxygen demand of 4800mgL -1 . Under these conditions, the removal rate of chemical oxygen demand was 83.3%, which was 19.3% higher than when using Rhodobacter blasticus or 10.6% higher than when using Rhodobacter capsulatus separately. This mixed photosynthetic bacteria achieved high chemical oxygen demand removal and cell yields. Copyright © 2016 Elsevier Ltd. All rights reserved.

Zooxanthellae harvested by ciliates associated with brown band syndrome of corals remain photosynthetically competent.

PubMed

Ulstrup, Karin E; Kühl, Michael; Bourne, David G

2007-03-01

Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae.

Zooxanthellae Harvested by Ciliates Associated with Brown Band Syndrome of Corals Remain Photosynthetically Competent▿

PubMed Central

Ulstrup, Karin E.; Kühl, Michael; Bourne, David G.

2007-01-01

Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae. PMID:17259357

An Improved Method for Extraction and Separation of Photosynthetic Pigments

ERIC Educational Resources Information Center

Katayama, Nobuyasu; Kanaizuka, Yasuhiro; Sudarmi, Rini; Yokohama, Yasutsugu

2003-01-01

The method for extracting and separating hydrophobic photosynthetic pigments proposed by Katayama "et al." ("Japanese Journal of Phycology," 42, 71-77, 1994) has been improved to introduce it to student laboratories at the senior high school level. Silica gel powder was used for removing water from fresh materials prior to…

Proton-Coupled Electron Transfer in Artificial Photosynthetic Systems.

PubMed

Mora, S Jimena; Odella, Emmanuel; Moore, Gary F; Gust, Devens; Moore, Thomas A; Moore, Ana L

2018-02-20

Artificial photosynthetic constructs can in principle operate more efficiently than natural photosynthesis because they can be rationally designed to optimize solar energy conversion for meeting human demands rather than the multiple needs of an organism competing for growth and reproduction in a complex ecosystem. The artificial photosynthetic constructs described in this Account consist primarily of covalently linked synthetic chromophores, electron donors and acceptors, and proton donors and acceptors that carry out the light absorption, electron transfer, and proton-coupled electron transfer (PCET) processes characteristic of photosynthetic cells. PCET is the movement of an electron from one site to another accompanied by proton transfer. PCET and the transport of protons over tens of angstroms are important in all living cells because they are a fundamental link between redox processes and the establishment of transmembrane gradients of proton electrochemical potential, known as proton-motive force (PMF), which is the unifying concept in bioenergetics. We have chosen a benzimidazole phenol (BIP) system as a platform for the study of PCET because with appropriate substitutions it is possible to design assemblies in which one or multiple proton transfers can accompany oxidation of the phenol. In BIP, oxidation of the phenol increases its acidity by more than ten pK a units; thus, electrochemical oxidation of the phenol is associated with a proton transfer to the imidazole. This is an example of a PCET process involving transfer of one electron and one proton, known as electron-proton transfer (EPT). When the benzimidazole moiety of BIP is substituted at the 4-position with good proton acceptor groups such as aliphatic amines, experimental and theoretical results indicate that two proton transfers occur upon one-electron oxidation of the phenol. This phenomenon is described as a one-electron-two-proton transfer (E2PT) process and results in translocation of

Photosynthetic Response to Long- and Short-Term Changes in Carbon Dioxide in Sweetpotatoes Grown Hydroponically with Enhanced Mineral Nutrition

NASA Technical Reports Server (NTRS)

Hamilton, Casey; Terse, Anita; Hileman, Douglas R.; Mortley, Desmond G.; Hill, Jill

1998-01-01

Sweetpotato [Ipomoea batatas L.(Lam.)] has been selected by NASA as a potential food for long-term space missions. In previous experiments, sweetpotato plants grown hydroponically under elevated levels of CO2 depleted the nitrogen in the nutrient solution between the hi-weekly solution replacements. In this experiment, the effect of enhanced nutrient replenishment on photosynthetic rates of sweetpotato was determined. CO2 response curves were determined for "TU-82-155" and "Georgia-Jet" sweetpotatoes grown hydroponically in growth chambers at three different CO2 concentrations (400, 750, and 1000 micro-mol/mol CO2). Gas exchange measurements were made using infrared gas analysis, an open-flow gas exchange system, and a controlled-climate cuvette. Photosynthetic measurements were made at CO2 concentrations from 50-1000 micro-mol/mol CO2. Net photosynthetic rates showed an increase with increasing measurement CO2 in all nutrient regimes, but the response of photosynthetic rates to the growth CO2 conditions varied among the experiments and between the two varieties. Enhanced mineral nutrition led to increased net photosynthetic rates in "Georgia Jet" plants, but not in "TU-82-155" plants. The results of this study will help to determine the CO2 requirements for growth of sweetpotato on proposed space missions.

A global scale mechanistic model of photosynthetic capacity (LUNA V1.0)

DOE PAGES

Ali, Ashehad A.; Xu, Chonggang; Rogers, Alistair; ...

2016-02-12

Although plant photosynthetic capacity as determined by the maximum carboxylation rate (i.e., V c,max25) and the maximum electron transport rate (i.e., J max25) at a reference temperature (generally 25 °C) is known to vary considerably in space and time in response to environmental conditions, it is typically parameterized in Earth system models (ESMs) with tabulated values associated with plant functional types. In this study, we have developed a mechanistic model of leaf utilization of nitrogen for assimilation (LUNA) to predict photosynthetic capacity at the global scale under different environmental conditions. We adopt an optimality hypothesis to nitrogen allocation among lightmore » capture, electron transport, carboxylation and respiration. The LUNA model is able to reasonably capture the measured spatial and temporal patterns of photosynthetic capacity as it explains ~55 % of the global variation in observed values of V c,max25 and ~65 % of the variation in the observed values of J max25. Model simulations with LUNA under current and future climate conditions demonstrate that modeled values of V c,max25 are most affected in high-latitude regions under future climates. In conclusion, ESMs that relate the values of V c,max25 or J max25 to plant functional types only are likely to substantially overestimate future global photosynthesis.« less

Impact of heavy metals on photosynthetic pigment content in roadside plant communities

NASA Astrophysics Data System (ADS)

Popova, Elena

2017-11-01

The research is dedicated to the study of the impact of heavy metals (As, Cr, Cu, Mo, Ni, Pb, Sr, Zn) found in plant samples on photosynthetic pigments in anthropogenic roadside plant communities. In the process of research, the anthropogenic load intensity for the selected sites (1 < 6 < 5 < 4 < 2 < 3) was determined. The analysis of the results showed that the impact of heavy metals on photosynthetic pigment content depends not only on metal toxicity but also on its concentration. A high level was noted for Pb (7.2-10.6), Cr (2.6-4.5), As (0.1-0.9) and Sr (9.4-12.1) mg/kg. The inverse relation between the heavy metal and photosynthetic pigment concentrations was revealed. The research showed that the concentration of chlorophyll a, b and carotenoids changes depending on the growing conditions. Carotenoids are less vulnerable to the negative impact of heavy metals as compared to chlorophylls. A higher concentration of carotenoids is noted in stressing environment. On the one hand, it decreases stress effect; on the other hand, it performs a protective function by preventing destruction of chlorophyll molecules and other organic substances. The obtained data may be used to forecast dynamics of plant populations and communities in the polluted areas and to monitor conditions of natural ecosystems.

Arrangement Analysis of Leaves Optimized on Photon Flux Density or Photosynthetic Rate

NASA Astrophysics Data System (ADS)

Obara, Shin'ya; Tanno, Itaru

By clarifying a plant evolutive process, useful information may be obtained on engineering. Consequently, an analysis algorithm that investigates the optimal arrangement of plant leaves was developed. In the developed algorithm, the Monte Carlo method is introduced and sunlight is simulated. Moreover, the arrangement optimization of leaves is analyzed using a Genetic Algorithm (GA). The number of light quanta (photon flux density) that reaches leaves, or the average photosynthetic rate of the same was set as the objective function, and leaf models of a dogwood and a ginkgo tree were analyzed. The number of leaf models was set between two to four, and the position of the leaf was expressed in terms of the angle of direction, elevation angle, rotation angle, and the representative length of the branch of a leaf. The chromosome model introduced into GA consists of information concerning the position of the leaf. Based on the analysis results, the characteristics of the leaf of an actual plant could be simulated by ensuring the algorithm had multiple constrained conditions. The optimal arrangement of leaves differs in maximization of the photon flux density, and that of the average value of a photosynthetic rate. Furthermore, the leaf form affecting the optimal arrangement of leave and also having a significant influence also on a photosynthetic rate was shown.

Quantum effects in energy and charge transfer in an artificial photosynthetic complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Pulak Kumar; Smirnov, Anatoly Yu.; Nori, Franco

2011-06-28

We investigate the quantum dynamics of energy and charge transfer in a wheel-shaped artificial photosynthetic antenna-reaction center complex. This complex consists of six light-harvesting chromophores and an electron-acceptor fullerene. To describe quantum effects on a femtosecond time scale, we derive the set of exact non-Markovian equations for the Heisenberg operators of this photosynthetic complex in contact with a Gaussian heat bath. With these equations we can analyze the regime of strong system-bath interactions, where reorganization energies are of the order of the intersite exciton couplings. We show that the energy of the initially excited antenna chromophores is efficiently funneled tomore » the porphyrin-fullerene reaction center, where a charge-separated state is set up in a few picoseconds, with a quantum yield of the order of 95%. In the single-exciton regime, with one antenna chromophore being initially excited, we observe quantum beatings of energy between two resonant antenna chromophores with a decoherence time of {approx}100 fs. We also analyze the double-exciton regime, when two porphyrin molecules involved in the reaction center are initially excited. In this regime we obtain pronounced quantum oscillations of the charge on the fullerene molecule with a decoherence time of about 20 fs (at liquid nitrogen temperatures). These results show a way to directly detect quantum effects in artificial photosynthetic systems.« less

What limits photosynthetic energy conversion efficiency in nature? Lessons from the oceans.

PubMed

Falkowski, Paul G; Lin, Hanzhi; Gorbunov, Maxim Y

2017-09-26

Constraining photosynthetic energy conversion efficiency in nature is challenging. In principle, two yield measurements must be made simultaneously: photochemistry, fluorescence and/or thermal dissipation. We constructed two different, extremely sensitive and precise active fluorometers: one measures the quantum yield of photochemistry from changes in variable fluorescence, the other measures fluorescence lifetimes in the picosecond time domain. By deploying the pair of instruments on eight transoceanic cruises over six years, we obtained over 200 000 measurements of fluorescence yields and lifetimes from surface waters in five ocean basins. Our results revealed that the average quantum yield of photochemistry was approximately 0.35 while the average quantum yield of fluorescence was approximately 0.07. Thus, closure on the energy budget suggests that, on average, approximately 58% of the photons absorbed by phytoplankton in the world oceans are dissipated as heat. This extraordinary inefficiency is associated with the paucity of nutrients in the upper ocean, especially dissolved inorganic nitrogen and iron. Our results strongly suggest that, in nature, most of the time, most of the phytoplankton community operates at approximately half of its maximal photosynthetic energy conversion efficiency because nutrients limit the synthesis or function of essential components in the photosynthetic apparatus.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'. © 2017 The Author(s).

Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis.

PubMed

Shimizu, Takayuki; Shen, Jiangchuan; Fang, Mingxu; Zhang, Yixiang; Hori, Koichi; Trinidad, Jonathan C; Bauer, Carl E; Giedroc, David P; Masuda, Shinji

2017-02-28

Sulfide was used as an electron donor early in the evolution of photosynthesis, with many extant photosynthetic bacteria still capable of using sulfur compounds such as hydrogen sulfide (H 2 S) as a photosynthetic electron donor. Although enzymes involved in H 2 S oxidation have been characterized, mechanisms of regulation of sulfide-dependent photosynthesis have not been elucidated. In this study, we have identified a sulfide-responsive transcriptional repressor, SqrR, that functions as a master regulator of sulfide-dependent gene expression in the purple photosynthetic bacterium Rhodobacter capsulatus SqrR has three cysteine residues, two of which, C41 and C107, are conserved in SqrR homologs from other bacteria. Analysis with liquid chromatography coupled with an electrospray-interface tandem-mass spectrometer reveals that SqrR forms an intramolecular tetrasulfide bond between C41 and C107 when incubated with the sulfur donor glutathione persulfide. SqrR is oxidized in sulfide-stressed cells, and tetrasulfide-cross-linked SqrR binds more weakly to a target promoter relative to unmodified SqrR. C41S and C107S R. capsulatus SqrRs lack the ability to respond to sulfide, and constitutively repress target gene expression in cells. These results establish that SqrR is a sensor of H 2 S-derived reactive sulfur species that maintain sulfide homeostasis in this photosynthetic bacterium and reveal the mechanism of sulfide-dependent transcriptional derepression of genes involved in sulfide metabolism.

Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light.

PubMed

Lichtenberg, Mads; Brodersen, Kasper E; Kühl, Michael

2017-01-01

We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O 2 , temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, E k , i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the

Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light

PubMed Central

Lichtenberg, Mads; Brodersen, Kasper E.; Kühl, Michael

2017-01-01

We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O2, temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, Ek, i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the

Variations in morphology and PSII photosynthetic capabilities during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi) Papenfuss (Gracilariales, Rhodophyta)

PubMed Central

2010-01-01

Background Red algae are primitive photosynthetic eukaryotes, whose spores are ideal subjects for studies of photosynthesis and development. Although the development of red alga spores has received considerable research attention, few studies have focused on the detailed morphological and photosynthetic changes that occur during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi) Papenfuss (Gracilariales, Rhodophyta). Herein, we documented these changes in this species of red algae. Results In the tetraspores, we observed two types of division, cruciate and zonate, and both could develop into multicellular bodies (disks). During the first 84 hours, tetraspores divided several times, but the diameter of the disks changed very little; thereafter, the diameter increased significantly. Scanning electron microscopy observations and analysis of histological sections revealed that the natural shape of the disk remains tapered over time, and the erect frond grows from the central protrusion of the disk. Cultivation of tissue from excised disks demonstrated that the central protrusion of the disk is essential for initiation of the erect frond. Photosynthetic (i.e., PSII) activities were measured using chlorophyll fluorescence analysis. The results indicated that freshly released tetraspores retained limited PSII photosynthetic capabilities; when the tetraspores attached to a substrate, those capabilities increased significantly. In the disk, the PSII activity of both marginal and central cells was similar, although some degree of morphological polarity was present; the PSII photosynthetic capabilities in young germling exhibited an apico-basal gradient. Conclusions Attachment of tetraspores to a substrate significantly enhanced their PSII photosynthetic capabilities, and triggered further development. The central protrusion of the disk is the growth point, may have transfer of nutritive material with the marginal cells. Within the young germling, the

Complete genome of the cellulolytic ruminal bacterium Ruminococcus albus 7

USDA-ARS?s Scientific Manuscript database

Ruminococcus albus 7 is a highly cellulolytic rumen bacterium that is a member of the phylum Firmicutes. Here, we describe the complete genome for this microbe. This genome will be useful for rumen microbiology, cellulosome biology, and in biofuel production, as one of its major fermentation product...

Atomic detail visualization of photosynthetic membranes with GPU-accelerated ray tracing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stone, John E.; Sener, Melih; Vandivort, Kirby L.

The cellular process responsible for providing energy for most life on Earth, namely, photosynthetic light-harvesting, requires the cooperation of hundreds of proteins across an organelle, involving length and time scales spanning several orders of magnitude over quantum and classical regimes. Simulation and visualization of this fundamental energy conversion process pose many unique methodological and computational challenges. In this paper, we present, in two accompanying movies, light-harvesting in the photosynthetic apparatus found in purple bacteria, the so-called chromatophore. The movies are the culmination of three decades of modeling efforts, featuring the collaboration of theoretical, experimental, and computational scientists. Finally, we describemore » the techniques that were used to build, simulate, analyze, and visualize the structures shown in the movies, and we highlight cases where scientific needs spurred the development of new parallel algorithms that efficiently harness GPU accelerators and petascale computers.« less

Atomic detail visualization of photosynthetic membranes with GPU-accelerated ray tracing

DOE PAGES

Stone, John E.; Sener, Melih; Vandivort, Kirby L.; ...

2015-12-12

The cellular process responsible for providing energy for most life on Earth, namely, photosynthetic light-harvesting, requires the cooperation of hundreds of proteins across an organelle, involving length and time scales spanning several orders of magnitude over quantum and classical regimes. Simulation and visualization of this fundamental energy conversion process pose many unique methodological and computational challenges. In this paper, we present, in two accompanying movies, light-harvesting in the photosynthetic apparatus found in purple bacteria, the so-called chromatophore. The movies are the culmination of three decades of modeling efforts, featuring the collaboration of theoretical, experimental, and computational scientists. Finally, we describemore » the techniques that were used to build, simulate, analyze, and visualize the structures shown in the movies, and we highlight cases where scientific needs spurred the development of new parallel algorithms that efficiently harness GPU accelerators and petascale computers.« less

A kinetic model for estimating net photosynthetic rates of cos lettuce leaves under pulsed light.

PubMed

Jishi, Tomohiro; Matsuda, Ryo; Fujiwara, Kazuhiro

2015-04-01

Time-averaged net photosynthetic rate (P n) under pulsed light (PL) is known to be affected by the PL frequency and duty ratio, even though the time-averaged photosynthetic photon flux density (PPFD) is unchanged. This phenomenon can be explained by considering that photosynthetic intermediates (PIs) are pooled during light periods and then consumed by partial photosynthetic reactions during dark periods. In this study, we developed a kinetic model to estimate P n of cos lettuce (Lactuca sativa L. var. longifolia) leaves under PL based on the dynamics of the amount of pooled PIs. The model inputs are average PPFD, duty ratio, and frequency; the output is P n. The rates of both PI accumulation and consumption at a given moment are assumed to be dependent on the amount of pooled PIs at that point. Required model parameters and three explanatory variables (average PPFD, frequency, and duty ratio) were determined for the simulation using P n values under PL based on several combinations of the three variables. The model simulation for various PL levels with a wide range of time-averaged PPFDs, frequencies, and duty ratios further demonstrated that P n under PL with high frequencies and duty ratios was comparable to, but did not exceed, P n under continuous light, and also showed that P n under PL decreased as either frequency or duty ratio was decreased. The developed model can be used to estimate P n under various light environments where PPFD changes cyclically.

Dynamic optimization of CELSS crop photosynthetic rate by computer-assisted feedback control

NASA Astrophysics Data System (ADS)

Chun, C.; Mitchell, C. A.

1997-01-01

A procedure for dynamic optimization of net photosynthetic rate (Pn) for crop production in Controlled Ecological Life-Support Systems (CELSS) was developed using leaf lettuce as a model crop. Canopy Pn was measured in real time and fed back for environmental control. Setpoints of photosynthetic photon flux (PPF) and CO_2 concentration for each hour of the crop-growth cycle were decided by computer to reach a targeted Pn each day. Decision making was based on empirical mathematical models combined with rule sets developed from recent experimental data. Comparisons showed that dynamic control resulted in better yield per unit energy input to the growth system than did static control. With comparable productivity parameters and potential for significant energy savings, dynamic control strategies will contribute greatly to the sustainability of space-deployed CELSS.

Draft Genome Sequence of an Anaerobic and Extremophilic Bacterium, Caldanaerobacter yonseiensis, Isolated from a Geothermal Hot Stream

PubMed Central

Lee, Sang-Jae; Lee, Yong-Jik; Park, Gun-Seok; Kim, Byoung-Chan; Lee, Sang Jun; Shin, Jae-Ho

2013-01-01

Caldanaerobacter yonseiensis is a strictly anaerobic, thermophilic, spore-forming bacterium, which was isolated from a geothermal hot stream in Indonesia. This bacterium utilizes xylose and produces a variety of proteases. Here, we report the draft genome sequence of C. yonseiensis, which reveals insights into the pentose phosphate pathway and protein degradation metabolism in thermophilic microorganisms. PMID:24201201

Effect of carbon limitation on photosynthetic electron transport in Nannochloropsis oculata.

PubMed

Zavřel, Tomáš; Szabó, Milán; Tamburic, Bojan; Evenhuis, Christian; Kuzhiumparambil, Unnikrishnan; Literáková, Petra; Larkum, Anthony W D; Raven, John A; Červený, Jan; Ralph, Peter J

2018-04-01

This study describes the impacts of inorganic carbon limitation on the photosynthetic efficiency and operation of photosynthetic electron transport pathways in the biofuel-candidate microalga Nannochloropsis oculata. Using a combination of highly-controlled cultivation setup (photobioreactor), variable chlorophyll a fluorescence and transient spectroscopy methods (electrochromic shift (ECS) and P 700 redox kinetics), we showed that net photosynthesis and effective quantum yield of Photosystem II (PSII) decreased in N. oculata under carbon limitation. This was accompanied by a transient increase in total proton motive force and energy-dependent non-photochemical quenching as well as slightly elevated respiration. On the other hand, under carbon limitation the rapid increase in proton motive force (PMF, estimated from the total ECS signal) was also accompanied by reduced conductivity of ATP synthase to protons (estimated from the rate of ECS decay in dark after actinic illumination). This indicates that the slow operation of ATP synthase results in the transient build-up of PMF, which leads to the activation of fast energy dissipation mechanisms such as energy-dependent non-photochemical quenching. N. oculata also increased content of lipids under carbon limitation, which compensated for reduced NAPDH consumption during decreased CO 2 fixation. The integrated knowledge of the underlying energetic regulation of photosynthetic processes attained with a combination of biophysical methods may be used to identify photo-physiological signatures of the onset of carbon limitation in microalgal cultivation systems, as well as to potentially identify microalgal strains that can better acclimate to carbon limitation. Copyright © 2018 Elsevier B.V. All rights reserved.

Non-cooperative immobilization of residual water bound in lyophilized photosynthetic lamellae.

PubMed

Harańczyk, Hubert; Baran, Ewelina; Nowak, Piotr; Florek-Wojciechowska, Małgorzata; Leja, Anna; Zalitacz, Dorota; Strzałka, Kazimierz

2015-12-01

This study applied 1H-NMR in time and in frequency domain measurements to monitor the changes that occur in bound water dynamics at decreased temperature and with increased hydration level in lyophilizates of native wheat photosynthetic lamellae and in photosynthetic lamellae reconstituted from lyophilizate. Proton relaxometry (measured as free induction decay = FID) distinguishes a Gaussian component S within the NMR signal (o). This comes from protons of the solid matrix of the lamellae and consists of (i) an exponentially decaying contribution L1 from mobile membrane protons, presumably from lipids, and from water that is tightly bound to the membrane surface and thus restricted in mobility; and (ii) an exponentially decaying component L2 from more mobile, loosely bound water pool. Both proton relaxometry data and proton spectroscopy show that dry lyophilizate incubated in dry air, i.e., at a relative humidity (p/p0) of 0% reveals a relatively high hydration level. The observed liquid signal most likely originates from mobile membrane protons and a tightly bound water fraction that is sealed in pores of dry lyophilizate and thus restricted in mobility. The estimations suggest that the amount of sealed water does not exceed the value characteristic for the main hydration shell of a phospholipid. Proton spectra collected for dry lyophilizate of photosynthetic lamellae show a continuous decrease in the liquid signal component without a distinct freezing transition when it is cooled down to -60ºC, which is significantly lower than the homogeneous ice nucleation temperature [Bronshteyn, V.L. et al. Biophys. J. 65 (1993) 1853].

In vitro assembly of a prohead-like structure of the Rhodobacter capsulatus gene transfer agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spano, Anthony J.; Chen, Frank S.; Goodman, Benjamin E.

2007-07-20

The gene transfer agent (GTA) is a phage-like particle capable of exchanging double-stranded DNA fragments between cells of the photosynthetic bacterium Rhodobacter capsulatus. Here we show that the major capsid protein of GTA, expressed in E. coli, can be assembled into prohead-like structures in the presence of calcium ions in vitro. Transmission electron microscopy (TEM) of uranyl acetate staining material and thin sections of glutaraldehyde-fixed material demonstrates that these associates have spherical structures with diameters in the range of 27-35 nm. The analysis of scanning TEM images revealed particles of mass {approx} 4.3 MDa, representing 101 {+-} 11 copies ofmore » the monomeric subunit. The establishment of this simple and rapid method to form prohead-like particles permits the GTA system to be used for genome manipulation within the photosynthetic bacterium, for specific targeted drug delivery, and for the construction of biologically based distributed autonomous sensors for environmental monitoring.« less

Fine Structure and Host-Virus Relationship of a Marine Bacterium and Its Bacteriophage

PubMed Central

Valentine, Artrice F.; Chapman, George B.

1966-01-01

Valentine, Artrice F. (Georgetown University, Washington, D.C.), and George B. Chapman. Fine structure and host-virus relationship of a marine bacterium and its bacteriophage. J. Bacteriol. 92:1535–1554. 1966.—The fine structure of a gram-negative marine bacterium, Cytophaga marinoflava sp. n., has been revealed by ultrathin sectioning and electron microscopy. Stages in the morphogenesis of the bacterial virus NCMB 385, which has been shown to be highly specific for this organism, were also demonstrated in bacterial cells fixed according to the Kellenberger technique. The bacterium possessed a cell wall, cytoplasmic membrane, and nuclear and cytoplasmic regions typical of bacterial cells. Both the cell wall and the cytoplasmic membrane showed a tripartite structure, i.e., each was composed of two dense layers separated by a low-density zone. Intracytoplasmic membrane systems were also observed, especially in dividing cells and in cells in which new viruses were being formed. As many as 18 hexagonally shaped, empty phage heads (membranes only) were observed in untreated, infected bacterial cells. Phage heads, intermediate in density to empty heads and fully condensed ones, possibly representing stages in the morphological development of the virus, were also seen. Images PMID:5924277

Contrasting Strategies of Photosynthetic Energy Utilization Drive Lifestyle Strategies in Ecologically Important Picoeukaryotes

PubMed Central

Halsey, Kimberly H.; Milligan, Allen J.; Behrenfeld, Michael J.

2014-01-01

The efficiency with which absorbed light is converted to net growth is a key property for estimating global carbon production. We previously showed that, despite considerable evolutionary distance, Dunaliella tertiolecta (Chlorophyceae) and Thalassiosira weissflogii (Bacillariophyceae) share a common strategy of photosynthetic energy utilization and nearly identical light energy conversion efficiencies. These findings suggested that a single model might be appropriate for describing relationships between measures of phytoplankton production. This conclusion was further evaluated for Ostreococcus tauri RCC1558 and Micromonas pusilla RCC299 (Chlorophyta, Prasinophyceae), two picoeukaryotes with contrasting geographic distributions and swimming abilities. Nutrient-dependent photosynthetic efficiencies in O. tauri were similar to the previously studied larger algae. Specifically, absorption-normalized gross oxygen and carbon production and net carbon production were independent of nutrient limited growth rate. In contrast, all measures of photosynthetic efficiency were strongly dependent on nutrient availability in M. pusilla. This marked difference was accompanied by a diminished relationship between Chla:C and nutrient limited growth rate and a remarkably greater efficiency of gross-to-net energy conversion than the other organisms studied. These results suggest that the cost-benefit of decoupling pigment concentration from nutrient availability enables motile organisms to rapidly exploit more frequent encounters with micro-scale nutrient patches in open ocean environments. PMID:24957026

Are Photosynthetic Characteristics and Energetic Cost Important Invasive Traits for Alien Sonneratia Species in South China?

PubMed

Li, Feng-Lan; Zan, Qi-Jie; Hu, Zheng-Yu; Shin, Paul-K S; Cheung, Siu-Gin; Wong, Yuk-Shan; Tam, Nora Fung-Yee; Lei, An-Ping

2016-01-01

A higher photosynthesis and lower energetic cost are recognized as important characteristics for invasive species, but whether these traits are also important for the ability of alien mangrove species to become invasive has seldom been reported. A microcosm study was conducted to compare the photosynthetic characteristics, energetic cost indices and other growth traits between two alien species (Sonneratia apetala and S. caseolaris) and four native mangrove species over four seasons in a subtropical mangrove nature reserve in Shenzhen, South China. The aim of the study was to evaluate the invasive potential of Sonneratia based on these physiological responses. The annual average net photosynthetic rate (Pn), stomatal conductance (Gs) and total carbon assimilation per unit leaf area (Atotal) of the two alien Sonneratia species were significantly higher than the values of the native mangroves. In contrast, the opposite results were obtained for the leaf construction cost (CC) per unit dry mass (CCM) and CC per unit area (CCA) values. The higher Atotal and lower CC values resulted in a 72% higher photosynthetic energy-use efficiency (PEUE) for Sonneratia compared to native mangroves, leading to a higher relative growth rate (RGR) of the biomass and height of Sonneratia with the respective values being 51% and 119% higher than those of the native species. Higher photosynthetic indices for Sonneratia compared to native species were found in all seasons except winter, whereas lower CC values were found in all four seasons. The present findings reveal that alien Sonneratia species may adapt well and become invasive in subtropical mangrove wetlands in Shenzhen due to their higher photosynthetic characteristics coupled with lower costs in energy use, leading to a higher PEUE. The comparison of these physiological responses between S. apetala and S. caseolaris reveal that the former species is more invasive than the latter one, thus requiring more attention in future.

Are Photosynthetic Characteristics and Energetic Cost Important Invasive Traits for Alien Sonneratia Species in South China?

PubMed Central

Li, Feng-Lan; Zan, Qi-Jie; Hu, Zheng-Yu; Shin, Paul-K. S.; Cheung, Siu-Gin; Wong, Yuk-Shan; Tam, Nora Fung-Yee; Lei, An-Ping

2016-01-01

A higher photosynthesis and lower energetic cost are recognized as important characteristics for invasive species, but whether these traits are also important for the ability of alien mangrove species to become invasive has seldom been reported. A microcosm study was conducted to compare the photosynthetic characteristics, energetic cost indices and other growth traits between two alien species (Sonneratia apetala and S. caseolaris) and four native mangrove species over four seasons in a subtropical mangrove nature reserve in Shenzhen, South China. The aim of the study was to evaluate the invasive potential of Sonneratia based on these physiological responses. The annual average net photosynthetic rate (Pn), stomatal conductance (Gs) and total carbon assimilation per unit leaf area (Atotal) of the two alien Sonneratia species were significantly higher than the values of the native mangroves. In contrast, the opposite results were obtained for the leaf construction cost (CC) per unit dry mass (CCM) and CC per unit area (CCA) values. The higher Atotal and lower CC values resulted in a 72% higher photosynthetic energy-use efficiency (PEUE) for Sonneratia compared to native mangroves, leading to a higher relative growth rate (RGR) of the biomass and height of Sonneratia with the respective values being 51% and 119% higher than those of the native species. Higher photosynthetic indices for Sonneratia compared to native species were found in all seasons except winter, whereas lower CC values were found in all four seasons. The present findings reveal that alien Sonneratia species may adapt well and become invasive in subtropical mangrove wetlands in Shenzhen due to their higher photosynthetic characteristics coupled with lower costs in energy use, leading to a higher PEUE. The comparison of these physiological responses between S. apetala and S. caseolaris reveal that the former species is more invasive than the latter one, thus requiring more attention in future. PMID

[Photosynthetic rate, transpiration rate, and water use efficiency of cotton canopy in oasis edge of Linze].

PubMed

Xie, Ting-Ting; Su, Pei-Xi; Gao, Song

2010-06-01

The measurement system of Li-8100 carbon flux and the modified assimilation chamber were used to study the photosynthetic characteristics of cotton (Gossypium hirsutum L.) canopy in the oasis edge region in middle reach of Heihe River Basin, mid Hexi Corridor of Gansu. At the experimental site, soil respiration and evaporation rates were significantly higher in late June than in early August, and the diurnal variation of canopy photosynthetic rate showed single-peak type. The photosynthetic rate was significantly higher (P < 0.01) in late June than in early August, with the daily average value being (43.11 +/- 1.26) micromol CO2 x m(-2) x s(-1) and (24.53 +/- 0.60) micromol CO2 x m(-2) x s(-1), respectively. The diurnal variation of canopy transpiration rate also presented single-peak type, with the daily average value in late June and early August being (3.10 +/- 0.34) mmol H2O x m(-2) x s(-1) and (1.60 +/- 0.26) mmol H2O x m(-2) x s(-1), respectively, and differed significantly (P < 0.01). The daily average value of canopy water use efficiency in late June and early August was (15.67 +/- 1.77) mmol CO2 x mol(-1) H2O and (23.08 +/- 5.54) mmol CO2 x mol(-1) H2O, respectively, but the difference was not significant (P > 0.05). Both in late June and in early August, the canopy photosynthetic rate was positively correlated with air temperature, PAR, and soil moisture content, suggesting that there was no midday depression of photosynthesis in the two periods. In August, the canopy photosynthetic rate and transpiration rate decreased significantly, because of the lower soil moisture content and leaf senescence, but the canopy water use efficiency had no significant decrease.

Complete genome sequence of the haloalkaliphilic, hydrogen-producing bacterium Halanaerobium hydrogeniformans.

PubMed

Brown, Steven D; Begemann, Matthew B; Mormile, Melanie R; Wall, Judy D; Han, Cliff S; Goodwin, Lynne A; Pitluck, Samuel; Land, Miriam L; Hauser, Loren J; Elias, Dwayne A

2011-07-01

Halanaerobium hydrogenoformans is an alkaliphilic bacterium capable of biohydrogen production at pH 11 and 7% (wt/vol) salt. We present the 2.6-Mb genome sequence to provide insights into its physiology and potential for bioenergy applications.

Biogeography of photosynthetic light-harvesting genes in marine phytoplankton.

PubMed

Bibby, Thomas S; Zhang, Yinan; Chen, Min

2009-01-01

Photosynthetic light-harvesting proteins are the mechanism by which energy enters the marine ecosystem. The dominant prokaryotic photoautotrophs are the cyanobacterial genera Prochlorococcus and Synechococcus that are defined by two distinct light-harvesting systems, chlorophyll-bound protein complexes or phycobilin-bound protein complexes, respectively. Here, we use the Global Ocean Sampling (GOS) Project as a unique and powerful tool to analyze the environmental diversity of photosynthetic light-harvesting genes in relation to available metadata including geographical location and physical and chemical environmental parameters. All light-harvesting gene fragments and their metadata were obtained from the GOS database, aligned using ClustalX and classified phylogenetically. Each sequence has a name indicative of its geographic location; subsequent biogeographical analysis was performed by correlating light-harvesting gene budgets for each GOS station with surface chlorophyll concentration. Using the GOS data, we have mapped the biogeography of light-harvesting genes in marine cyanobacteria on ocean-basin scales and show that an environmental gradient exists in which chlorophyll concentration is correlated to diversity of light-harvesting systems. Three functionally distinct types of light-harvesting genes are defined: (1) the phycobilisome (PBS) genes of Synechococcus; (2) the pcb genes of Prochlorococcus; and (3) the iron-stress-induced (isiA) genes present in some marine Synechococcus. At low chlorophyll concentrations, where nutrients are limited, the Pcb-type light-harvesting system shows greater genetic diversity; whereas at high chlorophyll concentrations, where nutrients are abundant, the PBS-type light-harvesting system shows higher genetic diversity. We interpret this as an environmental selection of specific photosynthetic strategy. Importantly, the unique light-harvesting system isiA is found in the iron-limited, high-nutrient low-chlorophyll region of

Differential accumulation of photosynthetic proteins regulates diurnal photochemical adjustments of PSII in common fig (Ficus carica L.) leaves.

PubMed

Mlinarić, Selma; Antunović Dunić, Jasenka; Skendrović Babojelić, Martina; Cesar, Vera; Lepeduš, Hrvoje

2017-02-01

Molecular processes involved in photosystem II adaptation of woody species to diurnal changes in light and temperature conditions are still not well understood. Regarding this, here we investigated differences between young and mature leaves of common fig (Ficus carica L.) in photosynthetic performance as well as accumulation of the main photosynthetic proteins: light harvesting complex II, D1 protein and Rubisco large subunit. Investigated leaf types revealed different adjustment mechanisms to keep effective photosynthesis. Rather stable diurnal accumulation of light harvesting complex II in mature leaves enabled efficient excitation energy utilization (negative L-band) what triggered faster D1 protein degradation at high light. However, after photoinhibition, greater accumulation of D1 during the night enabled them faster recovery. So, the most photosynthetic parameters, as the maximum quantum yield for primary photochemistry, electron transport and overall photosynthetic efficiency in mature leaves successfully restored to their initial values at 1a.m. Reduced connectivity of light harvesting complexes II to its reaction centers (positive L-band) in young leaves increased dissipation of excess light causing less pressure to D1 and its slower degradation. Decreased electron transport in young leaves, due to reduced transfer beyond primary acceptor Q A - most probably additionally induced degradation of Rubisco large subunit what consequently led to the stronger decrease of overall photosynthetic efficiency in young leaves at noon. Copyright © 2016 Elsevier GmbH. All rights reserved.

Isolation and biological characteristics of aerobic marine magnetotactic bacterium YSC-1

NASA Astrophysics Data System (ADS)

Gao, Jun; Pan, Hongmiao; Yue, Haidong; Song, Tao; Zhao, Yong; Chen, Guanjun; Wu, Longfei; Xiao, Tian

2006-12-01

Magnetotactic bacteria have become a hot spot of research in microbiology attracting intensive interest of researchers in multiple disciplinary fields. However, the studies were limited in few fastidious bacteria. The objective of this study aims at isolating new marine magnetic bacteria and better comprehension of magnetotactic bacteria. In this study, an aerobic magnetotactic bacterium YSC-1 was isolated from sediments in the Yellow Sea Cold Water Mass (YSCWM). In TEM, magnetic cells have one or several circular magnetosomes in diameter of 100nm, and consist of Fe and Co shown on energy dispersive X-ray spectrum. The biological and physiological characteristics of this bacterium were also described. The colour of YSC-1 colony is white in small rod. The gram stain is negative. Results showed that Strain YSC-1 differs from microaerophile magnetotactic bacteria MS-1 and WD-1 in biology.

Alternating electron and proton transfer steps in photosynthetic water oxidation

PubMed Central

Klauss, André; Haumann, Michael; Dau, Holger

2012-01-01

Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on Earth, and is the paradigm for engineering solar fuel–production systems. Each complete reaction cycle of photosynthetic water oxidation requires the removal of four electrons and four protons from the catalytic site, a manganese–calcium complex and its protein environment in photosystem II. In time-resolved photothermal beam deflection experiments, we monitored apparent volume changes of the photosystem II protein associated with charge creation by light-induced electron transfer (contraction) and charge-compensating proton relocation (expansion). Two previously invisible proton removal steps were detected, thereby filling two gaps in the basic reaction-cycle model of photosynthetic water oxidation. In the S2 → S3 transition of the classical S-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (). The rate-determining elementary step (τ, approximately 30 µs at 20 °C) in the long-distance proton relocation toward the protein–water interface is characterized by a high activation energy (Ea = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the S0 → S1 transition are similar (τ, approximately 100 µs; Ea = 0.34 ± 0.08 eV; kinetic isotope effect, approximately 3); however, the proton removal from the Mn complex proceeds after electron transfer to . By discovery of the transient formation of two further intermediate states in the reaction cycle of photosynthetic water oxidation, a temporal sequence of strictly alternating removal of electrons and protons from the catalytic site is established. PMID:22988080

Alternating electron and proton transfer steps in photosynthetic water oxidation.

PubMed

Klauss, André; Haumann, Michael; Dau, Holger

2012-10-02

Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on Earth, and is the paradigm for engineering solar fuel-production systems. Each complete reaction cycle of photosynthetic water oxidation requires the removal of four electrons and four protons from the catalytic site, a manganese-calcium complex and its protein environment in photosystem II. In time-resolved photothermal beam deflection experiments, we monitored apparent volume changes of the photosystem II protein associated with charge creation by light-induced electron transfer (contraction) and charge-compensating proton relocation (expansion). Two previously invisible proton removal steps were detected, thereby filling two gaps in the basic reaction-cycle model of photosynthetic water oxidation. In the S(2) → S(3) transition of the classical S-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (Y Z OX). The rate-determining elementary step (τ, approximately 30 µs at 20 °C) in the long-distance proton relocation toward the protein-water interface is characterized by a high activation energy (E(a) = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the S(0) → S(1) transition are similar (τ, approximately 100 µs; E(a) = 0.34 ± 0.08 eV; kinetic isotope effect, approximately 3); however, the proton removal from the Mn complex proceeds after electron transfer to . By discovery of the transient formation of two further intermediate states in the reaction cycle of photosynthetic water oxidation, a temporal sequence of strictly alternating removal of electrons and protons from the catalytic site is established.

Species-specific photosynthetic responses of four coniferous seedlings to open-field experimental warming

NASA Astrophysics Data System (ADS)

Han, S.; Yoon, S. J.; Yoon, T. K.; Han, S. H.; Lee, J.; Lee, D.; Kim, S.; Hwang, J.; Cho, M.; Son, Y.

2014-12-01

Temperature increase under climate change is expected to affect photosynthesis of tree species. Biochemical models generally suggest that the elevated temperature increases the photosynthetic carbon fixation, however, many opposing results were reported as well. We aimed to examine the photosynthetic responses of four coniferous seedlings to projected future temperature increase, by conducting an open-field warming experiment. Experimental warming set-up using infra-red heater was built in 2011 and the temperature in warming plots has been regulated to be consistently 3oC higher than that of control plots. The seeds of Abies holophylla (AH), A. koreana (AK), Pinus densiflora (PD), and P. koraiensis (PK) were planted in each 1 m × 1 m plot (n=3) in April, 2012. Monthly net photosynthetic rates (Pn; μmol CO2 m-2 s-1) of 1-year-old seedlings (n=9) from June to November, 2013 were measured using CIRAS-2 (PP-Systems, UK) and photosynthetic parameters (the apparent quantum yield; ф; µmol CO2 mol-1, the dark respiration rate; Rd; µmol CO2 mol-1, and the light compensation point; LCP; µmol mol-1 s-1) were also calculated from the light-response curve of photosynthesis in August, 2013. Chlorophyll contents were measured using DMSO extraction method. Monthly Pn was generally higher for PD and decreased for AK in warmed plots than in control plots (Fig. 1). Pn of AK and PK did not show any significant difference, however, Pn of PK in October and November increased by experimental warming. Pn of PD also showed the highest increase in November and this distinct increase of Pn in autumn might be caused by delayed cessation of photosynthesis by temperature elevation. ф and Rd in warmed plots were higher for PD and lower for AK, while LCP did not significantly differ by treatments for all species. Because ф is considered to be related to the efficiency of harvesting and using light, the change in ф might have caused the response of Pn to warming in this study. Decreases

Photosynthetic Activity and Adaptation Capacities of Lichens and Cyanobacteria to Martian Surface Conditions

NASA Astrophysics Data System (ADS)

De Vera, Jean-Pierre; Schulze-Makuch, D.; Khan, A.; Lorek, A.; Koncz, A.; Stivaletta, N.; Möhlmann, D.; Spohn, T.

2012-05-01

We observed an increase in photosynthetic activity in the lichen Pleopsidium chlorophanum but a strong negative effect on the photosynthetic activity of endolithic cyanobacteria when subjected for 34 days to environmental stresses likely to be encountered in semi-protected habitats on the Martian surface. Stresses were simulated in a Mars Simulation Chamber (MSC) and included high UV fluxes, low temperatures, low water activity, high atmospheric CO2 concentrations, and an atmospheric pressure of about 6 mbar. P. chlorophanum is an extremophile: it lives in very cold, dry, high-altitude habitats which are Earth's best approximation of the Martian surface. Our lichen samples came from North Victoria Land in Antarctica whereas the investigated samples of cyanobacteria came from tropic regions in the Sahara. Three samples of each group of organisms were exposed uninterruptedly to simulated conditions (as above) of the naked, unprotected Martian surface for 34 days, receiving the full Martian solar spectrum (200 - 2500 nm) for a cumulative UV dose of 6343.6 kJm-2. For a second sample set - containing also three lichen thalli and three endolithic cyanobacteria communities - the cumulative (34-day) UV dose was reduced to 268.8 kJm-2, to reasonably simulate the amount the microorganisms might receive in (semi-) protected surface sites (e.g., fissures, cracks and micro-caves within rocks or permafrost soil). In the 'unprotected' experiment it was unclear if the lichen was still actively photosynthesizing but still clear that the cyanobacteria were affected. However, under 'protected site' conditions, the cyanobacteria had no clear photosynthetic response under and after simulated Martian conditions but the lichen not only survived and remained photosynthetically active, it even adapted physiologically by increasing its photosynthetic activity over 34 days. Comparison with other Mars simulation experiments on exposure platforms in space and in the laboratory with other

A novel subfamily of monomeric inorganic pyrophosphatases in photosynthetic eukaryotes

PubMed Central

Gómez-García, María R.; Losada, Manuel; Serrano, Aurelio

2005-01-01

Two sPPases (soluble inorganic pyrophosphatases, EC 3.6.1.1) have been isolated from the microalga Chlamydomonas reinhardtii. Both are monomeric proteins of organellar localization, the chloroplastic sPPase I [Cr (Ch. reinhardtii)-sPPase I, 30 kDa] is a major isoform and slightly larger protein than the mitochondrial sPPase II (Cr-sPPase II, 24 kDa). They are members of sPPase family I and are encoded by two different cDNAs, as demonstrated by peptide mass fingerprint analysis. Molecular phylogenetic analyses indicated that Cr-sPPase I is closely related to other eukaryotic sPPases, whereas Cr-sPPase II resembles its prokaryotic counterparts. Chloroplastic sPPase I may have replaced a cyanobacterial ancestor very early during plastid evolution. Cr-sPPase II orthologues are found in members of the green photosynthetic lineage, but not in animals or fungi. These two sPPases from photosynthetic eukaryotes are novel monomeric family I sPPases with different molecular phylogenies and cellular localizations. PMID:16313235

Spring photosynthetic onset and net CO2 uptake in Alaska triggered by landscape thawing.

PubMed

Parazoo, Nicholas C; Arneth, Almut; Pugh, Thomas A M; Smith, Ben; Steiner, Nicholas; Luus, Kristina; Commane, Roisin; Benmergui, Josh; Stofferahn, Eric; Liu, Junjie; Rödenbeck, Christian; Kawa, Randy; Euskirchen, Eugenie; Zona, Donatella; Arndt, Kyle; Oechel, Walt; Miller, Charles

2018-04-24

The springtime transition to regional-scale onset of photosynthesis and net ecosystem carbon uptake in boreal and tundra ecosystems are linked to the soil freeze-thaw state. We present evidence from diagnostic and inversion models constrained by satellite fluorescence and airborne CO 2 from 2012 to 2014 indicating the timing and magnitude of spring carbon uptake in Alaska correlates with landscape thaw and ecoregion. Landscape thaw in boreal forests typically occurs in late April (DOY 111 ± 7) with a 29 ± 6 day lag until photosynthetic onset. North Slope tundra thaws 3 weeks later (DOY 133 ± 5) but experiences only a 20 ± 5 day lag until photosynthetic onset. These time lag differences reflect efficient cold season adaptation in tundra shrub and the longer dehardening period for boreal evergreens. Despite the short transition from thaw to photosynthetic onset in tundra, synchrony of tundra respiration with snow melt and landscape thaw delays the transition from net carbon loss (at photosynthetic onset) to net uptake by 13 ± 7 days, thus reducing the tundra net carbon uptake period. Two global CO 2 inversions using a CASA-GFED model prior estimate earlier northern high latitude net carbon uptake compared to our regional inversion, which we attribute to (i) early photosynthetic-onset model prior bias, (ii) inverse method (scaling factor + optimization window), and (iii) sparsity of available Alaskan CO 2 observations. Another global inversion with zero prior estimates the same timing for net carbon uptake as the regional model but smaller seasonal amplitude. The analysis of Alaskan eddy covariance observations confirms regional scale findings for tundra, but indicates that photosynthesis and net carbon uptake occur up to 1 month earlier in evergreens than captured by models or CO 2 inversions, with better correlation to above-freezing air temperature than date of primary thaw. Further collection and analysis of boreal evergreen species over

Coordination between leaf CO2 diffusion and Rubisco properties allows maximizing photosynthetic efficiency in Limonium species.

PubMed

Galmés, Jeroni; Molins, Arántzazu; Flexas, Jaume; Conesa, Miquel À

2017-10-01

High photosynthetic efficiency intrinsically demands tight coordination between traits related to CO 2 diffusion capacity and leaf biochemistry. Although this coordination constitutes the basis of existing mathematical models of leaf photosynthesis, it has been barely explored among closely related species, which could reveal rapid adaptation clues in the recent past. With this aim, we characterized the photosynthetic capacity of 12 species of Limonium, possessing contrasting Rubisco catalytic properties, grown under optimal (WW) and extreme drought conditions (WD). The availability of CO 2 at the site of carboxylation (C c ) determined the photosynthetic capacity of Limonium under WD, while both diffusional and biochemical components governed the photosynthetic performance under WW. The variation in the in vivo caboxylation efficiency correlated with both the concentration of active Rubisco sites and the in vitro-based properties of Rubisco, such as the maximum carboxylase turnover rate (k cat c ) and the Michaelis-Menten constant for CO 2 (K c ). Notably, the results confirmed the hypothesis of coordination between the CO 2 offer and demand functions of photosynthesis: those Limonium species with high total leaf conductance to CO 2 have evolved towards increased velocity (i.e. higher k cat c ), at the penalty of lower affinity for CO 2 (i.e. lower specificity factor, S c/o ). © 2017 John Wiley & Sons Ltd.

Direct and selective small-molecule inhibition of photosynthetic PEP carboxylase: New approach to combat C4 weeds in arable crops.

PubMed

Paulus, Judith Katharina; Förster, Kerstin; Groth, Georg

2014-06-05

Phosphoenolpyruvate carboxylase (PEPC) is a key enzyme of C4 photosynthesis. Besides, non-photosynthetic isoforms of PEPC are found in bacteria and all types of plants, although not in animals or fungi. A single residue in the allosteric feedback inhibitor site of PEPC was shown to adjust the affinity of the photosynthetic and non-photosynthetic isoforms for feedback inhibition by metabolites of the C4 pathway. Here, we applied computational screening and biochemical analyses to identify molecules that selectively inhibit C4 PEPC, but have no effect on the activity of non-photosynthetic PEPCs. We found two types of selective inhibitors, catechins and quinoxalines. Binding constants in the lower μM range and a strong preference for C4 PEPC qualify the quinoxaline compounds as potential selective herbicides to combat C4 weeds. Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Engineering cyanobacteria as photosynthetic feedstock factories

PubMed Central

Hays, Stephanie G.; Ducat, Daniel C.

2018-01-01

Carbohydrate feedstocks are at the root of bioindustrial production and are needed in greater quantities than ever due to increased prioritization of renewable fuels and reduction of carbon emissions. Cyanobacteria possess a number of features that make them well-suited as an alternative feedstock crop in comparison to traditional, terrestrial plant species. Recent advances in genetic engineering, as well as promising preliminary investigations of cyanobacteria in a number of distinct production regimes have illustrated the potential of these aquatic phototrophs as biosynthetic chasses. Further improvements in strain productivities and design, along with enhanced understanding of photosynthetic metabolism in cyanobacteria may pave the way to translate cyanobacterial theoretical potential into realized application. PMID:24526260

A Comparison of Photosynthetic Characteristics of Encelia Species Possessing Glabrous and Pubescent Leaves 1

PubMed Central

Ehleringer, James R.; Björkman, Olle

1978-01-01

Measurements of the dependence of photosynthesis on light, CO2, and temperature are reported for two species of Encelia (Compositae) which differ in leaf pubescence and in geographical distribution. Encelia californica is glabrous and occurs in relatively mild, but arid habitats and Encelia farinosa is heavily pubescent and occurs in hot, arid habitats. Both species possess the C3 photosynthetic pathway. Under high irradiances and normal atmospheric conditions the two species have high photosynthetic rates, exceeding 3 nanomoles of CO2 per square centimeter per second (48 milligrams of CO2 per square decimeter per hour) and complete light saturation does not occur by full noon sunlight. The high photosynthetic capacity is related to a high efficiency of utilization of intercellular CO2 combined with high stomatal conductance. Leaf estimates of total soluble protein and fraction I protein are higher in these species than in most plants, although the proportion of fraction I protein is not higher. Both E. californica and E. farinosa attain a maximum rate of photosynthesis between 25 and 30 C, despite the fact that the two species grow in very different thermal habitats. Neither E. californica nor E. farinosa shows significant acclimation in the temperature dependence of photosynthesis when grown under different temperature regimes. The presence of leaf hairs which reduce leaf absorptance and consequently leaf temperature plays an important part in the ability of E. farinosa to survive in its native high temperature environment. When the effects of pubescence are taken into account, there are few if any significant differences in the photosynthetic characteristics of the two species. PMID:16660483

A hemiparasite in the forest understorey: photosynthetic performance and carbon balance of Melampyrum pratense.

PubMed

Světlíková, P; Hájek, T; Těšitel, J

2018-01-01

Melampyrum pratense is an annual root-hemiparasitic plant growing mostly in forest understorey, an environment with unstable light conditions. While photosynthetic responses of autotrophic plants to variable light conditions are in general well understood, light responses of root hemiparasites have not been investigated. We carried out gas exchange measurements (light response and photosynthetic induction curves) to assess the photosynthetic performance of M. pratense in spring and summer. These data and recorded light dynamics data were subsequently used to model carbon balance of the hemiparasite throughout the entire growth season. Summer leaves had significantly lower rates of saturated photosynthesis and dark respiration than spring leaves, a pattern expected to reflect the difference between sun- and shade-adapted leaves. However, even the summer leaves of the hemiparasite exhibited a higher rate of light-saturated photosynthesis than reported in non-parasitic understorey herbs. This is likely related to its annual life history, rare among other understorey herbs. The carbon balance model considering photosynthetic induction still indicated insufficient autotrophic carbon gain for seed production in the summer months due to limited light availability and substantial carbon loss through dark respiration. The results point to potentially high importance of heterotrophic carbon acquisition in M. pratense, which could be of at least comparable importance as in other mixotrophic plants growing in forests - mistletoes and partial mycoheterotrophs. It is remarkable that despite apparent evolutionary pressure towards improved carbon acquisition from the host, M. pratense retains efficient photosynthesis and high transpiration rate, the ecophysiological traits typical of related root hemiparasites in the Orobanchaceae. © 2017 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

Thermal responses of Symbiodinium photosynthetic carbon assimilation

NASA Astrophysics Data System (ADS)

Oakley, Clinton A.; Schmidt, Gregory W.; Hopkinson, Brian M.

2014-06-01

The symbiosis between hermatypic corals and their dinoflagellate endosymbionts, genus Symbiodinium, is based on carbon exchange. This symbiosis is disrupted by thermally induced coral bleaching, a stress response in which the coral host expels its algal symbionts as they become physiologically impaired. The disruption of the dissolved inorganic carbon (DIC) supply or the thermal inactivation of Rubisco have been proposed as sites of initial thermal damage that leads to the bleaching response. Symbiodinium possesses a highly unusual Form II ribulose bisphosphate carboxylase/oxygenase (Rubisco), which exhibits a lower CO2:O2 specificity and may be more thermally unstable than the Form I Rubiscos of other algae and land plants. Components of the CO2 concentrating mechanism (CCM), which supplies inorganic carbon for photosynthesis, may also be temperature sensitive. Here, we examine the ability of four cultured Symbiodinium strains to acquire and fix DIC across a temperature gradient. Surprisingly, the half-saturation constant of photosynthesis with respect to DIC concentration ( K P), an index of CCM function, declined with increasing temperature in three of the four strains, indicating a greater potential for photosynthetic carbon acquisition at elevated temperatures. In the fourth strain, there was no effect of temperature on K P. Finding no evidence for thermal inhibition of the CCM, we conclude that CCM components are not likely to be the primary sites of thermal damage. Reduced photosynthetic quantum yields, a hallmark of thermal bleaching, were observed at low DIC concentrations, leaving open the possibility that reduced inorganic carbon availability is involved in bleaching.

Comparison of Photoacoustic Signals in Photosynthetic and Nonphotosynthetic Leaf Tissues of Variegated Pelargonium zonale

NASA Astrophysics Data System (ADS)

Veljović-Jovanović, S.; Vidović, M.; Morina, F.; Prokić, Lj.; Todorović, D. M.

2016-09-01

Green-white variegated leaves of Pelargonium zonale were studied using the photoacoustic method. Our aim was to characterize photosynthetically active green tissue and nonphotosynthetically active white tissue by the photoacoustic amplitude signals. We observed lower stomatal conductance and higher leaf temperature in white tissue than in green tissue. Besides these thermal differences, significantly higher absorbance in green tissue was based on chlorophyll and carotenoids which were absent in white tissue. However, optical properties of epidermal layers of both tissues were equal. The photoacoustic amplitude of white tissue was over four times higher compared to green tissue, which was correlated with lower stomatal conductance. In addition, at frequencies >700 Hz, the significant differences between the photoacoustic signals of green and white tissue were obtained. We identified the photoacoustic signal deriving from photosynthetic oxygen evolution in green tissue, using high intensity of red light modulated at 10 Hz. Moreover, the photoacoustic amplitude of green tissue increased progressively with time which corresponded to the period of induction of photosynthetic oxygen evolution. For the first time, very high frequencies (1 kHz to 5 kHz) were applied on leaf material.

Relationship between symbiont density and photosynthetic carbon acquisition in the temperate coral Cladocora caespitosa

NASA Astrophysics Data System (ADS)

Hoogenboom, M.; Beraud, E.; Ferrier-Pagès, C.

2010-03-01

This study quantified variation in net photosynthetic carbon gain in response to natural fluctuations in symbiont density for the Mediterranean coral Cladocora caespitosa, and evaluated which density maximized photosynthetic carbon acquisition. To do this, carbon acquisition was modeled as an explicit function of symbiont density. The model was parameterized using measurements of rates of photosynthesis and respiration for small colonies with a broad range of zooxanthella concentrations. Results demonstrate that rates of net photosynthesis increase asymptotically with symbiont density, whereas rates of respiration increase linearly. In combination, these functional responses meant that colony energy acquisition decreased at both low and at very high zooxanthella densities. However, there was a wide range of symbiont densities for which net daily photosynthesis was approximately equivalent. Therefore, significant changes in symbiont density do not necessarily cause a change in autotrophic energy acquisition by the colony. Model estimates of the optimal range of cell densities corresponded well with independent observations of symbiont concentrations obtained from field and laboratory studies of healthy colonies. Overall, this study demonstrates that the seasonal fluctuations, in symbiont numbers observed in healthy colonies of the Mediterranean coral investigated, do not have a strong effect on photosynthetic energy acquisition.

Natural Genetic Variation for Acclimation of Photosynthetic Light Use Efficiency to Growth Irradiance in Arabidopsis1[OPEN

PubMed Central

Harbinson, Jeremy

2015-01-01

Plants are known to be able to acclimate their photosynthesis to the level of irradiance. Here, we present the analysis of natural genetic variation for photosynthetic light use efficiency (ΦPSII) in response to five light environments among 12 genetically diverse Arabidopsis (Arabidopsis thaliana) accessions. We measured the acclimation of ΦPSII to constant growth irradiances of four different levels (100, 200, 400, and 600 µmol m−2 s−1) by imaging chlorophyll fluorescence after 24 d of growth and compared these results with acclimation of ΦPSII to a step-wise change in irradiance where the growth irradiance was increased from 100 to 600 µmol m−2 s−1 after 24 d of growth. Genotypic variation for ΦPSII is shown by calculating heritability for the short-term ΦPSII response to different irradiance levels as well as for the relation of ΦPSII measured at light saturation (a measure of photosynthetic capacity) to growth irradiance level and for the kinetics of the response to a step-wise increase in irradiance from 100 to 600 µmol m−2 s−1. A genome-wide association study for ΦPSII measured 1 h after a step-wise increase in irradiance identified several new candidate genes controlling this trait. In conclusion, the different photosynthetic responses to a changing light environment displayed by different Arabidopsis accessions are due to genetic differences, and we have identified candidate genes for the photosynthetic response to an irradiance change. The genetic variation for photosynthetic acclimation to irradiance found in this study will allow future identification and analysis of the causal genes for the regulation of ΦPSII in plants. PMID:25670817

PSI Mehler reaction is the main alternative photosynthetic electron pathway in Symbiodinium sp., symbiotic dinoflagellates of cnidarians.

PubMed

Roberty, Stéphane; Bailleul, Benjamin; Berne, Nicolas; Franck, Fabrice; Cardol, Pierre

2014-10-01

Photosynthetic organisms have developed various photoprotective mechanisms to cope with exposure to high light intensities. In photosynthetic dinoflagellates that live in symbiosis with cnidarians, the nature and relative amplitude of these regulatory mechanisms are a matter of debate. In our study, the amplitude of photosynthetic alternative electron flows (AEF) to oxygen (chlororespiration, Mehler reaction), the mitochondrial respiration and the Photosystem I (PSI) cyclic electron flow were investigated in strains belonging to three clades (A1, B1 and F1) of Symbiodinium. Cultured Symbiodinium strains were maintained under identical environmental conditions, and measurements of oxygen evolution, fluorescence emission and absorption changes at specific wavelengths were used to evaluate PSI and PSII electron transfer rates (ETR). A light- and O2 -dependent ETR was observed in all strains. This electron transfer chain involves PSII and PSI and is insensitive to inhibitors of mitochondrial activity and carbon fixation. We demonstrate that in all strains, the Mehler reaction responsible for photoreduction of oxygen by the PSI under high light, is the main AEF at the onset and at the steady state of photosynthesis. This sustained photosynthetic AEF under high light intensities acts as a photoprotective mechanism and leads to an increase of the ATP/NADPH ratio. © 2014 The Authors New Phytologist © 2014 New Phytologist Trust.

Ocean Acidification Alters the Photosynthetic Responses of a Coccolithophorid to Fluctuating Ultraviolet and Visible Radiation1[OPEN

PubMed Central

Jin, Peng; Gao, Kunshan; Villafañe, Virginia E.; Campbell, Douglas A.; Helbling, E. Walter

2013-01-01

Mixing of seawater subjects phytoplankton to fluctuations in photosynthetically active radiation (400–700 nm) and ultraviolet radiation (UVR; 280–400 nm). These irradiance fluctuations are now superimposed upon ocean acidification and thinning of the upper mixing layer through stratification, which alters mixing regimes. Therefore, we examined the photosynthetic carbon fixation and photochemical performance of a coccolithophore, Gephyrocapsa oceanica, grown under high, future (1,000 μatm) and low, current (390 μatm) CO2 levels, under regimes of fluctuating irradiances with or without UVR. Under both CO2 levels, fluctuating irradiances, as compared with constant irradiance, led to lower nonphotochemical quenching and less UVR-induced inhibition of carbon fixation and photosystem II electron transport. The cells grown under high CO2 showed a lower photosynthetic carbon fixation rate but lower nonphotochemical quenching and less ultraviolet B (280–315 nm)-induced inhibition. Ultraviolet A (315–400 nm) led to less enhancement of the photosynthetic carbon fixation in the high-CO2-grown cells under fluctuating irradiance. Our data suggest that ocean acidification and fast mixing or fluctuation of solar radiation will act synergistically to lower carbon fixation by G. oceanica, although ocean acidification may decrease ultraviolet B-related photochemical inhibition. PMID:23749851

Photosynthetic Machineries in Nano-Systems

PubMed Central

Nagy, László; Magyar, Melinda; Szabó, Tibor; Hajdu, Kata; Giotta, Livia; Dorogi, Márta; Milano, Francesco

2014-01-01

Photosynthetic reaction centres are membrane-spanning proteins, found in several classes of autotroph organisms, where a photoinduced charge separation and stabilization takes place with a quantum efficiency close to unity. The protein remains stable and fully functional also when extracted and purified in detergents thereby biotechnological applications are possible, for example, assembling it in nano-structures or in optoelectronic systems. Several types of bionanocomposite materials have been assembled by using reaction centres and different carrier matrices for different purposes in the field of light energy conversion (e.g., photovoltaics) or biosensing (e.g., for specific detection of pesticides). In this review we will summarize the current status of knowledge, the kinds of applications available and the difficulties to be overcome in the different applications. We will also show possible research directions for the close future in this specific field. PMID:24678673

Coupled hydraulic and photosynthetic feedbacks on forest transpiration throughout the growing season

NASA Astrophysics Data System (ADS)

Mackay, D. S.; Ewers, B. E.

2007-12-01

Ecosystem models account for vegetative controls on water fluxes using environmental drivers and hydraulic and/or biochemical limits on canopy stomatal conductance (Gs), variations in space and time of leaf area index (L), and species or biome specific parameters. However, some parameters, such as maximum stomatal conductance or its reference proxy at vapor pressure deficit of 1 kPa (Gsref), may not be strictly time-independent suggesting as yet undefined mechanisms in the models. We developed a model of coupled canopy water and carbon exchange, which allowed us to examine photosynthetic and hydraulic feedbacks on Gsref spanning the whole growing season for several dominant tree species in wetland and upland positions that collectively account for most a 1600 square km region centered on the WLEF AmeriFlux tower in Wisconsin, USA. The model assimilated half-hourly sap flux and micrometeorological data to quantify and explain temporal variations in Gsref for trembling aspen, sugar maple, and red pine in upland sites, and speckled alder and white cedar in wetland sites. Results show (1) phenological effects on photosynthetic activity with feedback on Gsref in all species, and (2) lags of up to two months between maximum per unit leaf area photosynthetic rates for conifer versus deciduous species. These results show that for given environmental conditions canopy transpiration depends on both L and timing of biochemical activation, both of which have implications for regional ecosystem water cycling.

Photosynthetic capacities of mature tropical forest trees in Rwanda are linked to successional group identity rather than to leaf nutrient content

NASA Astrophysics Data System (ADS)

Dusenge, Mirindi Eric; Wallin, Göran; Gårdesten, Johanna; Adolfsson, Lisa; Niyonzima, Felix; Nsabimana, Donat; Uddling, Johan

2014-05-01

Tropical forests are crucial in the global carbon balance, yet information required to estimate how much carbon that enter these ecosystems through photosynthesis is very limited, in particular for Africa and for tropical montane forests. In order to increases the knowledge of natural variability of photosynthetic capacities in tropical tree species in tropical Africa, measurements of leaf traits and gas exchange were conducted on sun and shade leaves of ten tree species growing in two tropical forests in Rwanda in central Africa. Seven species were studied in Ruhande Arboretum, a forest plantation at mid altitude (1700 m), and six species in Nyungwe National Park, a cooler and higher altitude (at 2500 m) montane rainforest. Three species were common to both sites. At Nyungwe, three species each belonged to the successional groups pioneer and climax species. Climax species had considerably lower maximum rates of photosynthetic carboxylation (Vcmax) and electron transport (Jmax) than pioneer species. This difference was not related to leaf nutrient content, but rather seemed to be caused by differences in within-leaf N allocation between the two successional groups. With respect to N, leaves of climax species invested less N into photosynthetic enzymes (as judged by lower Vcmax and Jmax values) and more N into chlorophyll (as judged by higher SPAD values). Photosynthetic capacities, (i.e., Jmax and Vcmax), Jmax to Vcmax ratio and P content were significantly higher in Nyungwe than in Arboretum. Sun leaves had higher photosynthetic capacities and nutrient content than shade leaves. Across the entire dataset, variation in photosynthetic capacities among species was not related to leaf nutrient content, although significant relationships were found within individual species. This study contributes critical tropical data for global carbon models and suggests that, for montane rainforest trees of different functional types, successional group identity is a better

Salt stress-induced protein pattern associated with photosynthetic parameters and andrographolide content in Andrographis paniculata Nees.

PubMed

Talei, Daryush; Valdiani, Alireza; Maziah, Mahmood; Sagineedu, Sreenivasa Rao; Abiri, Rambod

2015-01-01

Andrographis paniculata is a multifunctional medicinal plant and a potent source of bioactive compounds. Impact of environmental stresses such as salinity on protein diversification, as well as the consequent changes in the photosynthetic parameters and andrographolide content (AG) of the herb, has not yet been thoroughly investigated. The present study showed that the salinity affects the protein pattern, and subsequently, it decreased the photosynthetic parameters, protein content, total dry weight, and total crude extract. Exceptionally, the AG content was increased (p ≤ 0.01). Moreover, it was noticed that the salinity at 12 dS m(-1) led to the maximum increase in AG content in all accessions. Interestingly, the leaf protein analysis revealed that the two polymorphic protein bands as low- and medium-sized of 17 and 45 kDa acted as the activator agents for the photosynthetic parameters and AG content. Protein sequencing and proteomic analysis can be conducted based on the present findings in the future.

Polysaccharide degradation systems of the saprophytic bacterium Cellvibrio japonicus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gardner, Jeffrey G.

Study of recalcitrant polysaccharide degradation by bacterial systems is critical for understanding biological processes such as global carbon cycling, nutritional contributions of the human gut microbiome, and the production of renewable fuels and chemicals. One bacterium that has a robust ability to degrade polysaccharides is the Gram-negative saprophyte Cellvibrio japonicus. A bacterium with a circuitous history, C. japonicus underwent several taxonomy changes from an initially described Pseudomonas sp. Most of the enzymes described in the pre-genomics era have also been renamed. Furthermore, this review aims to consolidate the biochemical, structural, and genetic data published on C. japonicus and its remarkablemore » ability to degrade cellulose, xylan, and pectin substrates. Initially, C. japonicus carbohydrate-active enzymes were studied biochemically and structurally for their novel polysaccharide binding and degradation characteristics, while more recent systems biology approaches have begun to unravel the complex regulation required for lignocellulose degradation in an environmental context. Also included is a discussion for the future of C. japonicus as a model system, with emphasis on current areas unexplored in terms of polysaccharide degradation and emerging directions for C. japonicus in both environmental and biotechnological applications.« less

Polysaccharide degradation systems of the saprophytic bacterium Cellvibrio japonicus

DOE PAGES

Gardner, Jeffrey G.

2016-06-04

Study of recalcitrant polysaccharide degradation by bacterial systems is critical for understanding biological processes such as global carbon cycling, nutritional contributions of the human gut microbiome, and the production of renewable fuels and chemicals. One bacterium that has a robust ability to degrade polysaccharides is the Gram-negative saprophyte Cellvibrio japonicus. A bacterium with a circuitous history, C. japonicus underwent several taxonomy changes from an initially described Pseudomonas sp. Most of the enzymes described in the pre-genomics era have also been renamed. Furthermore, this review aims to consolidate the biochemical, structural, and genetic data published on C. japonicus and its remarkablemore » ability to degrade cellulose, xylan, and pectin substrates. Initially, C. japonicus carbohydrate-active enzymes were studied biochemically and structurally for their novel polysaccharide binding and degradation characteristics, while more recent systems biology approaches have begun to unravel the complex regulation required for lignocellulose degradation in an environmental context. Also included is a discussion for the future of C. japonicus as a model system, with emphasis on current areas unexplored in terms of polysaccharide degradation and emerging directions for C. japonicus in both environmental and biotechnological applications.« less

Biodegradation of polyethylene by the thermophilic bacterium Brevibacillus borstelensis.

PubMed

Hadad, D; Geresh, S; Sivan, A

2005-01-01

To select a polyethylene-degrading micro-organism and to study the factors affecting its biodegrading activity. A thermophilic bacterium Brevibaccillus borstelensis strain 707 (isolated from soil) utilized branched low-density polyethylene as the sole carbon source and degraded it. Incubation of polyethylene with B. borstelensis (30 days, 50 degrees C) reduced its gravimetric and molecular weights by 11 and 30% respectively. Brevibaccillus borstelensis also degraded polyethylene in the presence of mannitol. Biodegradation of u.v. photo-oxidized polyethylene increased with increasing irradiation time. Fourier Transform Infra-Red (FTIR) analysis of photo-oxidized polyethylene revealed a reduction in carbonyl groups after incubation with the bacteria. This study demonstrates that polyethylene--considered to be inert--can be biodegraded if the right microbial strain is isolated. Enrichment culture methods were effective for isolating a thermophilic bacterium capable of utilizing polyethylene as the sole carbon and energy source. Maximal biodegradation was obtained in combination with photo-oxidation, which showed that carbonyl residues formed by photo-oxidation play a role in biodegradation. Brevibaccillus borstelensis also degraded the CH2 backbone of nonirradiated polyethylene. Biodegradation of polyethylene by a single bacterial strain contributes to our understanding of the process and the factors affecting polyethylene biodegradation.

Photosynthetic temperature responses of tree species in Rwanda: evidence of pronounced negative effects of high temperature in montane rainforest climax species

NASA Astrophysics Data System (ADS)

Vårhammar, Angelica; Wallin, Göran; McLean, Christopher M.; Dusenge, Mirindi Eric; Medlyn, Belinda E.; Hasper, Thomas B.; Nsabimana, Donat; Uddling, Johan

2015-04-01

The sensitivity of photosynthetic metabolism to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial feedback on future climate change. While temperature responses of photosynthetic capacities have been comparatively well investigated in temperate species, the responses of tropical tree species remain unexplored. We compared the responses of seedlings of native cold-adapted tropical montane rainforest tree species to exotic warm-adapted plantation species, all growing in an intermediate temperature common garden in Rwanda. Leaf gas exchange responses to CO2 at different temperatures (20 - 40 C) were used to assess the temperature responses of biochemical photosynthetic capacities. Analyses revealed a lower optimum temperature for photosynthetic electron transport rates than for Rubisco carboxylation rates, along with lower electron transport optima in the native cold-adapted than in the exotic warm-adapted species. The photosynthetic optimum temperatures were generally exceeded by daytime peak leaf temperatures, in particular in the native montane rainforest climax species. This study thus provides evidence of pronounced negative effects of high temperature in tropical trees and indicates high susceptibility of montane rainforest climax species to future global warming. (Reference: New Phytologist, in press)

Aerobic Reduction of Arsenate by a Bacterium Isolated From Activated Sludge

NASA Astrophysics Data System (ADS)

Kozai, N.; Ohnuki, T.; Hanada, S.; Nakamura, K.; Francis, A. J.

2006-12-01

Microlunatus phosphovorus strain NM-1 is a polyphosphate-accumulating bacterium isolated from activated sludge. This bacterium takes up a large amount of polyphosphate under aerobic conditions and release phosphate ions by hydrolysis of polyphosphate to orthophosphate under anaerobic conditions to derive energy for taking up substrates. To understand the nature of this strain, especially, influence of potential contaminants in sewage and wastewater on growth, we have been investigating behavior of this bacterium in media containing arsenic. The present paper mainly reports reduction of arsenate by this bacterium under aerobic conditions. The strain NM-1 (JCM 9379) was aerobically cultured at 30 °C in a nutrient medium containing 2.5 g/l peptone, 0.5 g/l glucose, 1.5 g/l yeast extract, and arsenic [Na2HAsO4 (As(V)) or Na3AsO3 (As(III))] at concentrations between 0 and 50 mM. The cells collected from arsenic-free media were dispersed in buffer solutions containing 2mM HEPES, 10mM NaCl, prescribed concentrations of As(V), and 0-0.2 percent glucose. Then, this cell suspension was kept at 20 °C under aerobic or anaerobic conditions. The speciation of arsenic was carried out by ion chromatography and ICP-MS. The growth of the strain under aerobic conditions was enhanced by the addition of As(V) at the concentration between 1 and 10 mM. The maximum optical density of the culture in the medium containing 5mM As(V) was 1.4 times greater than that of the control culture. Below the As(V) concentration of 10mM, most of the As(V) was reduced to As(III). The growth of the strain under anaerobic conditions has not been observed so far. The cells in the buffer solutions reduced As(V) under aerobic condition. The reduction was enhanced by the addition of glucose. However, the cell did not reduce As(V) under anaerobic conditions. The strain NM-1 showed high resistance to As(V) and As(III). The maximum optical density of the culture grown in a medium containing 50 mM As(V) was only

Thermostable purified endoglucanase from thermophilic bacterium acidothermus cellulolyticus

DOEpatents

Tucker, Melvin P.; Grohmann, Karel; Himmel, Michael E.; Mohagheghi, Ali

1992-01-01

A substantially purified high molecular weight cellulase enzyme having a molecular weight of between about 156,000 to about 203,400 daltons isolated from the bacterium Acidothermus cellulolyticus (ATCC 43068) and a method of producing it are disclosed. The enzyme is water soluble, possesses both C.sub.1 and C.sub.x types of enzymatic activity, has a high degree of stability toward heat and exhibits both a high optimum temperature activity and high inactivation characteristics.

Photosynthetic responses of C3 and C4 species to seasonal water variability and competition.

PubMed

Niu, Shuli; Yuan, Zhiyou; Zhang, Yanfang; Liu, Weixing; Zhang, Lei; Huang, Jianhui; Wan, Shiqiang

2005-11-01

This study examined the impacts of seasonal water variability and interspecific competition on the photosynthetic characteristics of a C3 (Leymus chinensis) and a C4 (Chloris virgata) grass species. Plants received the same amount of water but in three seasonal patterns, i.e. the one-peak model (more water in the summer than in the spring and autumn), the two-peak model (more water in the spring and autumn than in the summer), and the average model (water evenly distributed over the growing season). The effects of water variability on the photosynthetic characteristics of the C3 and C4 species were dependent on season. There were significant differences in the photosynthetic characteristics of the C4 species in the summer and the C3 species in the autumn among the three water treatments. Interspecific competition exerted negative impacts on the C3 species in August and September but had no effects on the C4 species in any of the four measuring dates. The relative competitive capability of the two species was not altered by water availability. The assimilation rate, the maximum quantum yield of net CO2 assimilation, and the maximum rate of carboxylation of the C3 species were 13-56%, 5-11%, and 11-48% greater, respectively, in a monoculture than in a mixture in August and September. The results demonstrated that the photosynthetic characteristics of the C3 and C4 species were affected by water availability, but the effects varied considerably with season.

Biome-specific effects of nitrogen and phosphorus on the photosynthetic characteristics of trees at a forest-savanna boundary in Cameroon.

PubMed

Domingues, Tomas Ferreira; Ishida, F Yoko; Feldpausch, Ted R; Grace, John; Meir, Patrick; Saiz, Gustavo; Sene, Olivier; Schrodt, Franziska; Sonké, Bonaventure; Taedoumg, Herman; Veenendaal, Elmar M; Lewis, Simon; Lloyd, Jon

2015-07-01

Photosynthesis/nutrient relationships of proximally growing forest and savanna trees were determined in an ecotonal region of Cameroon (Africa). Although area-based foliar N concentrations were typically lower for savanna trees, there was no difference in photosynthetic rates between the two vegetation formation types. Opposite to N, area-based P concentrations were-on average-slightly lower for forest trees; a dependency of photosynthetic characteristics on foliar P was only evident for savanna trees. Thus savanna trees use N more efficiently than their forest counterparts, but only in the presence of relatively high foliar P. Along with some other recent studies, these results suggest that both N and P are important modulators of woody tropical plant photosynthetic capacities, influencing photosynthetic metabolism in different ways that are also biome specific. Attempts to find simple unifying equations to describe woody tropical vegetation photosynthesis-nutrient relationships are likely to meet with failure, with ecophysiological distinctions between forest and savanna requiring acknowledgement.

Genome sequence of the algicidal bacterium Kordia algicida OT-1.

PubMed

Lee, Hyun Sook; Kang, Sung Gyun; Kwon, Kae Kyoung; Lee, Jung-Hyun; Kim, Sang-Jin

2011-08-01

Kordia algicida OT-1 is an algicidal bacterium against the bloom-forming microalgae. The genome sequence of K. algicida revealed a number of interesting features, including the degradation of macromolecules, the biosynthesis of carotenoid pigment and secondary metabolites, and the capacity for gliding motility, which might facilitate the understanding of algicidal mechanisms.

Photoprotection Conferred by Changes in Photosynthetic Protein Levels and Organization during Dehydration of a Homoiochlorophyllous Resurrection Plant1

PubMed Central

Charuvi, Dana; Nevo, Reinat; Shimoni, Eyal; Naveh, Leah; Zia, Ahmad; Adam, Zach; Farrant, Jill M.; Kirchhoff, Helmut; Reich, Ziv

2015-01-01

During desiccation, homoiochlorophyllous resurrection plants retain most of their photosynthetic apparatus, allowing them to resume photosynthetic activity quickly upon water availability. These plants rely on various mechanisms to prevent the formation of reactive oxygen species and/or protect their tissues from the damage they inflict. In this work, we addressed the issue of how homoiochlorophyllous resurrection plants deal with the problem of excessive excitation/electron pressures during dehydration using Craterostigma pumilum as a model plant. To investigate the alterations in the supramolecular organization of photosynthetic protein complexes, we examined cryoimmobilized, freeze-fractured leaf tissues using (cryo)scanning electron microscopy. These examinations revealed rearrangements of photosystem II (PSII) complexes, including a lowered density during moderate dehydration, consistent with a lower level of PSII proteins, as shown by biochemical analyses. The latter also showed a considerable decrease in the level of cytochrome f early during dehydration, suggesting that initial regulation of the inhibition of electron transport is achieved via the cytochrome b6f complex. Upon further dehydration, PSII complexes are observed to arrange into rows and semicrystalline arrays, which correlates with the significant accumulation of sucrose and the appearance of inverted hexagonal lipid phases within the membranes. As opposed to PSII and cytochrome f, the light-harvesting antenna complexes of PSII remain stable throughout the course of dehydration. Altogether, these results, along with photosynthetic activity measurements, suggest that the protection of retained photosynthetic components is achieved, at least in part, via the structural rearrangements of PSII and (likely) light-harvesting antenna complexes into a photochemically quenched state. PMID:25713340

Evidence of carbon fixation pathway in a bacterium from candidate phylum SBR1093 revealed with genomic analysis.

PubMed

Wang, Zhiping; Guo, Feng; Liu, Lili; Zhang, Tong

2014-01-01

Autotrophic CO2 fixation is the most important biotransformation process in the biosphere. Research focusing on the diversity and distribution of relevant autotrophs is significant to our comprehension of the biosphere. In this study, a draft genome of a bacterium from candidate phylum SBR1093 was reconstructed with the metagenome of an industrial activated sludge. Based on comparative genomics, this autotrophy may occur via a newly discovered carbon fixation path, the hydroxypropionate-hydroxybutyrate (HPHB) cycle, which was demonstrated in a previous work to be uniquely possessed by some genera from Archaea. This bacterium possesses all of the thirteen enzymes required for the HPHB cycle; these enzymes share 30∼50% identity with those in the autotrophic species of Archaea that undergo the HPHB cycle and 30∼80% identity with the corresponding enzymes of the mixotrophic species within Bradyrhizobiaceae. Thus, this bacterium might have an autotrophic growth mode in certain conditions. A phylogenetic analysis based on the 16S rRNA gene reveals that the phylotypes within candidate phylum SBR1093 are primarily clustered into 5 clades with a shallow branching pattern. This bacterium is clustered with phylotypes from organically contaminated environments, implying a demand for organics in heterotrophic metabolism. Considering the types of regulators, such as FnR, Fur, and ArsR, this bacterium might be a facultative aerobic mixotroph with potential multi-antibiotic and heavy metal resistances. This is the first report on Bacteria that may perform potential carbon fixation via the HPHB cycle, thus may expand our knowledge of the distribution and importance of the HPHB cycle in the biosphere.

Towards quantification of vibronic coupling in photosynthetic antenna complexes

NASA Astrophysics Data System (ADS)

Singh, V. P.; Westberg, M.; Wang, C.; Dahlberg, P. D.; Gellen, T.; Gardiner, A. T.; Cogdell, R. J.; Engel, G. S.

2015-06-01

Photosynthetic antenna complexes harvest sunlight and efficiently transport energy to the reaction center where charge separation powers biochemical energy storage. The discovery of existence of long lived quantum coherence during energy transfer has sparked the discussion on the role of quantum coherence on the energy transfer efficiency. Early works assigned observed coherences to electronic states, and theoretical studies showed that electronic coherences could affect energy transfer efficiency—by either enhancing or suppressing transfer. However, the nature of coherences has been fiercely debated as coherences only report the energy gap between the states that generate coherence signals. Recent works have suggested that either the coherences observed in photosynthetic antenna complexes arise from vibrational wave packets on the ground state or, alternatively, coherences arise from mixed electronic and vibrational states. Understanding origin of coherences is important for designing molecules for efficient light harvesting. Here, we give a direct experimental observation from a mutant of LH2, which does not have B800 chromophores, to distinguish between electronic, vibrational, and vibronic coherence. We also present a minimal theoretical model to characterize the coherences both in the two limiting cases of purely vibrational and purely electronic coherence as well as in the intermediate, vibronic regime.

Enhancing soybean photosynthetic CO2 assimilation using a cyanobacterial membrane protein, ictB.

PubMed

Hay, William T; Bihmidine, Saadia; Mutlu, Nedim; Hoang, Khang Le; Awada, Tala; Weeks, Donald P; Clemente, Tom E; Long, Stephen P

2017-05-01

Soybean C 3 photosynthesis can suffer a severe loss in efficiency due to photorespiration and the lack of a carbon concentrating mechanism (CCM) such as those present in other plant species or cyanobacteria. Transgenic soybean (Glycine max cv. Thorne) plants constitutively expressing cyanobacterial ictB (inorganic carbon transporter B) gene were generated using Agrobacterium-mediated transformation. Although more recent data suggest that ictB does not actively transport HCO3-/CO 2 , there is nevertheless mounting evidence that transformation with this gene can increase higher plant photosynthesis. The hypothesis that expression of the ictB gene would improve photosynthesis, biomass production and seed yield in soybean was tested, in two independent replicated greenhouse and field trials. Results showed significant increases in photosynthetic CO 2 uptake (A net ) and dry mass in transgenic relative to wild type (WT) control plants in both the greenhouse and field trials. Transgenic plants also showed increased photosynthetic rates and biomass production during a drought mimic study. The findings presented herein demonstrate that ictB, as a single-gene, contributes to enhancement in various yield parameters in a major commodity crop and point to the significant role that biotechnological approaches to increasing photosynthetic efficiency can play in helping to meet increased global demands for food. Copyright © 2017 Elsevier GmbH. All rights reserved.

Communication: Coherences observed in vivo in photosynthetic bacteria using two-dimensional electronic spectroscopy

NASA Astrophysics Data System (ADS)

Dahlberg, Peter D.; Norris, Graham J.; Wang, Cheng; Viswanathan, Subha; Singh, Ved P.; Engel, Gregory S.

2015-09-01

Energy transfer through large disordered antenna networks in photosynthetic organisms can occur with a quantum efficiency of nearly 100%. This energy transfer is facilitated by the electronic structure of the photosynthetic antennae as well as interactions between electronic states and the surrounding environment. Coherences in time-domain spectroscopy provide a fine probe of how a system interacts with its surroundings. In two-dimensional electronic spectroscopy, coherences can appear on both the ground and excited state surfaces revealing detailed information regarding electronic structure, system-bath coupling, energy transfer, and energetic coupling in complex chemical systems. Numerous studies have revealed coherences in isolated photosynthetic pigment-protein complexes, but these coherences have not been observed in vivo due to the small amplitude of these signals and the intense scatter from whole cells. Here, we present data acquired using ultrafast video-acquisition gradient-assisted photon echo spectroscopy to observe quantum beating signals from coherences in vivo. Experiments were conducted on isolated light harvesting complex II (LH2) from Rhodobacter sphaeroides, whole cells of R. sphaeroides, and whole cells of R. sphaeroides grown in 30% deuterated media. A vibronic coherence was observed following laser excitation at ambient temperature between the B850 and the B850∗ states of LH2 in each of the 3 samples with a lifetime of ˜40-60 fs.

Leaf Photosynthetic Rate of Tropical Ferns Is Evolutionarily Linked to Water Transport Capacity

PubMed Central

Cao, Kun-Fang; Hu, Hong; Zhang, Jiao-Lin

2014-01-01

Ferns usually have relatively lower photosynthetic potential than angiosperms. However, it is unclear whether low photosynthetic potential of ferns is linked to leaf water supply. We hypothesized that there is an evolutionary association of leaf water transport capacity with photosynthesis and stomatal density in ferns. In the present study, a series of functional traits relating to leaf anatomy, hydraulics and physiology were assessed in 19 terrestrial and 11 epiphytic ferns in a common garden, and analyzed by a comparative phylogenetics method. Compared with epiphytic ferns, terrestrial ferns had higher vein density (Dvein), stomatal density (SD), stomatal conductance (gs), and photosynthetic capacity (Amax), but lower values for lower epidermal thickness (LET) and leaf thickness (LT). Across species, all traits varied significantly, but only stomatal length (SL) showed strong phylogenetic conservatism. Amax was positively correlated with Dvein and gs with and without phylogenetic corrections. SD correlated positively with Amax, Dvein and gs, with the correlation between SD and Dvein being significant after phylogenetic correction. Leaf water content showed significant correlations with LET, LT, and mesophyll thickness. Our results provide evidence that Amax of the studied ferns is linked to leaf water transport capacity, and there was an evolutionary association between water supply and demand in ferns. These findings add new insights into the evolutionary correlations among traits involving carbon and water economy in ferns. PMID:24416265

Characterization of a potentially novel 'blown pack' spoilage bacterium isolated from bovine hide.

PubMed

Moschonas, G; Bolton, D J

2013-03-01

To characterize a psychrotrophic bacterium, designated TC1, previously isolated from a cattle hide in Ireland, and to investigate the ability of this strain to cause 'blown pack' spoilage (BPS) of vacuum-packaged beef primals. TC1 was characterized using a combination of phenotypic, chemotaxonomic and genotypic analyses and was assessed for its ability to spoil vacuum-packaged beef at refrigerated temperatures. TC1 was Gram-positive and formed elliptical subterminal endospores. The strain was able to grow between 0 and 33 °C, with optimal growth between 23 and 24 °C. TC1 could be differentiated from its phylogenetically closest neighbour (Clostridium lituseburense DSM 797(T)) by 16S rRNA gene sequencing, pulsed-field gel electrophoresis and cellular fatty acid composition. TC1 spoiled (BPS) beef within 42 days when inoculated in cold-stored (1 °C) vacuum-packed beef. The phenotypic, chemotaxonomic and genotypic characterization indicated that TC1 may represent a potentially novel, cold-tolerant, gas-producing bacterium of considerable economic significance to the beef industry. This study reports and characterizes an emerging BPS bacterium, which should be considered in future activities designed to minimize the psychrophilic and psychrotrophic spoilage of vacuum-packaged beef. © 2012 The Society for Applied Microbiology.

The gene transfer agent-like particle of the marine phototrophic bacterium Rhodovulum sulfidophilum.

PubMed

Nagao, Nobuyoshi; Yamamoto, Junya; Komatsu, Hiroyuki; Suzuki, Hiromichi; Hirose, Yuu; Umekage, So; Ohyama, Takashi; Kikuchi, Yo

2015-12-01

Gene transfer agents (GTAs) are shaped like bacteriophage particles but have many properties that distinguish them from bacteriophages. GTAs play a role in horizontal gene transfer in nature and thus affect the evolution of prokaryotic genomes. In the course of studies on the extracellular production of designed RNAs using the marine bacterium Rhodovulum sulfidophilum , we found that this bacterium produces a GTA-like particle. The particle contains DNA fragments of 4.5 kb, which consist of randomly fragmented genomic DNA from the bacterium. This 4.5-kb DNA production was prevented while quorum sensing was inhibited. Direct observation of the particle by transmission electron microscopy revealed that the particle resembles a tailed phage and has a head diameter of about 40 nm and a tail length of about 60 nm. We also identified the structural genes for the GTA in the genome. Translated amino acid sequences and gene positions are closely related to those of the genes that encode the Rhodobacter capsulatus GTA. This is the first report of a GTA-like particle from the genus Rhodovulum . However, gene transfer activity of this particle has not yet been confirmed. The differences between this particle and other GTAs are discussed.

A critical review on the improvement of photosynthetic carbon assimilation in C3 plants using genetic engineering.

PubMed

Ruan, Cheng-Jiang; Shao, Hong-Bo; Teixeira da Silva, Jaime A

2012-03-01

Global warming is one of the most serious challenges facing us today. It may be linked to the increase in atmospheric CO2 and other greenhouse gases (GHGs), leading to a rise in sea level, notable shifts in ecosystems, and in the frequency and intensity of wild fires. There is a strong interest in stabilizing the atmospheric concentration of CO2 and other GHGs by decreasing carbon emission and/or increasing carbon sequestration. Biotic sequestration is an important and effective strategy to mitigate the effects of rising atmospheric CO2 concentrations by increasing carbon sequestration and storage capacity of ecosystems using plant photosynthesis and by decreasing carbon emission using biofuel rather than fossil fuel. Improvement of photosynthetic carbon assimilation, using transgenic engineering, potentially provides a set of available and effective tools for enhancing plant carbon sequestration. In this review, firstly different biological methods of CO2 assimilation in C3, C4 and CAM plants are introduced and three types of C4 pathways which have high photosynthetic performance and have evolved as CO2 pumps are briefly summarized. Then (i) the improvement of photosynthetic carbon assimilation of C3 plants by transgenic engineering using non-C4 genes, and (ii) the overexpression of individual or multiple C4 cycle photosynthetic genes (PEPC, PPDK, PCK, NADP-ME and NADP-MDH) in transgenic C3 plants (e.g. tobacco, potato, rice and Arabidopsis) are highlighted. Some transgenic C3 plants (e.g. tobacco, rice and Arabidopsis) overexpressing the FBP/SBPase, ictB and cytochrome c6 genes showed positive effects on photosynthetic efficiency and growth characteristics. However, over the last 28 years, efforts to overexpress individual, double or multiple C4 enzymes in C3 plants like tobacco, potato, rice, and Arabidopsis have produced mixed results that do not confirm or eliminate the possibility of improving photosynthesis of C3 plants by this approach. Finally, a prospect

Chitin Utilization by the Insect-Transmitted Bacterium Xylella fastidiosa▿ †

PubMed Central

Killiny, Nabil; Prado, Simone S.; Almeida, Rodrigo P. P.

2010-01-01

Xylella fastidiosa is an insect-borne bacterium that colonizes xylem vessels of a large number of host plants, including several crops of economic importance. Chitin is a polysaccharide present in the cuticle of leafhopper vectors of X. fastidiosa and may serve as a carbon source for this bacterium. Biological assays showed that X. fastidiosa reached larger populations in the presence of chitin. Additionally, chitin induced phenotypic changes in this bacterium, notably increasing adhesiveness. Quantitative PCR assays indicated transcriptional changes in the presence of chitin, and an enzymatic assay demonstrated chitinolytic activity by X. fastidiosa. An ortholog of the chitinase A gene (chiA) was identified in the X. fastidiosa genome. The in silico analysis revealed that the open reading frame of chiA encodes a protein of 351 amino acids with an estimated molecular mass of 40 kDa. chiA is in a locus that consists of genes implicated in polysaccharide degradation. Moreover, this locus was also found in the genomes of closely related bacteria in the genus Xanthomonas, which are plant but not insect associated. X. fastidiosa degraded chitin when grown on a solid chitin-yeast extract-agar medium and grew in liquid medium with chitin as the sole carbon source; ChiA was also determined to be secreted. The gene encoding ChiA was cloned into Escherichia coli, and endochitinase activity was detected in the transformant, showing that the gene is functional and involved in chitin degradation. The results suggest that X. fastidiosa may use its vectors' foregut surface as a carbon source. In addition, chitin may trigger X. fastidiosa's gene regulation and biofilm formation within vectors. Further work is necessary to characterize the role of chitin and its utilization in X. fastidiosa. PMID:20656858

Participation of intracellular and extracellular pH changes in photosynthetic response development induced by variation potential in pumpkin seedlings.

PubMed

Sherstneva, O N; Vodeneev, V A; Katicheva, L A; Surova, L M; Sukhov, V S

2015-06-01

Electrical signals presented in plants by action potential and by variation potential (VP) can induce a reversible inactivation of photosynthesis. Changes in the intracellular and extracellular pH during VP generation are a potential mechanism of photosynthetic response induction; however, this hypothesis requires additional experimental investigation. The purpose of the present work was to analyze the influence of pH changes on induction of the photosynthetic response in pumpkin. It was shown that a burning of the cotyledon induced VP propagation into true leaves of pumpkin seedlings inducing a decrease in the photosynthetic CO2 assimilation and an increase in non-photochemical quenching of fluorescence, whereas respiration was activated insignificantly. The photosynthetic response magnitude depended linearly on the VP amplitude. The intracellular and extracellular concentrations of protons were analyzed using pH-sensitive fluorescent probes, and the VP generation was shown to be accompanied by apoplast alkalization (0.4 pH unit) and cytoplasm acidification (0.3 pH unit). The influence of changes in the incubation medium pH on the non-photochemical quenching of fluorescence of isolated chloroplasts was also investigated. It was found that acidification of the medium stimulated the non-photochemical quenching, and the magnitude of this increase depended on the decrease in pH. Our results confirm the contribution of changes in intracellular and extracellular pH to induction of the photosynthetic response caused by VP. Possible mechanisms of the influence of pH changes on photosynthesis are discussed.

Preillumination of lettuce seedlings with red light enhances the resistance of photosynthetic apparatus to UV-A.

PubMed

Kreslavski, Vladimir D; Lyubimov, Valery Yu; Shirshikova, Galina N; Shmarev, Alexander N; Kosobryukhov, Anatoly A; Schmitt, Franz-Josef; Friedrich, Thomas; Allakhverdiev, Suleyman I

2013-05-05

Seedlings of 10-day-old lettuce (Lactuca sativa L., cultivar Berlin) were preilluminated by low intensity red light (λmax=660 nm, 10 min, 5 μmol quanta m(-2) s(-1)) and far-red light (λmax=730 nm, 10 min, 5 μmol quanta m(-2) s(-1)) to study the effect of pre-treatment on photosynthesis, photochemical activity of photosystem II (PSII), the contents of photosynthetic and UV-A-absorbing pigments (UAPs) and H2O2, as well as total and ascorbate peroxidase activities in cotyledonary leaves of seedlings exposed to UV-A. UV radiation reduced the photosynthetic rate (Pn), the activity of PSII, and the contents of Chl a and b, carotenoids and UAPs in the leaves, but increased the content of H2O2 and the total peroxidase activity. Preillumination with red light removed these effects of UV. In turn, the illumination with red light, then far-red light removed the effect of the red light. Illumination with red light alone increased the content of UAPs, as well as peroxidase activity. It is suggested that higher resistance of the lettuce photosynthetic apparatus to UV-A radiation is associated with involvement of the active form of phytochrome B, thereby increasing peroxidase activities as well as UAPs and saving preservation of photosynthetic pigment contents due to pre-illumination with red light. Copyright © 2013 Elsevier B.V. All rights reserved.

Temperature-Induced Remodeling of the Photosynthetic Machinery Tunes Photosynthesis in the Thermophilic Alga Cyanidioschyzon merolae1

PubMed Central

Nikolova, Denitsa; Weber, Dieter; Scholz, Martin

2017-01-01

The thermophilic alga C. merolae thrives in extreme environments (low pH and temperature between 40°C and 56°C). In this study, we investigated the acclimation process of the alga to a colder temperature (25°C). A long-term cell growth experiment revealed an extensive remodeling of the photosynthetic apparatus in the first 250 h of acclimation, which was followed by cell growth to an even higher density than the control (grown at 42°C) cell density. Once the cells were shifted to the lower temperature, the proteins of the light-harvesting antenna were greatly down-regulated and the phycobilisome composition was altered. The amount of PSI and PSII subunits was also decreased, but the chlorophyll to photosystems ratio remained unchanged. The 25°C cells possessed a less efficient photon-to-oxygen conversion rate and require a 2.5 times higher light intensity to reach maximum photosynthetic efficiency. With respect to chlorophyll, however, the photosynthetic oxygen evolution rate of the 25°C culture was 2 times higher than the control. Quantitative proteomics revealed that acclimation requires, besides remodeling of the photosynthetic apparatus, also adjustment of the machinery for protein folding, degradation, and homeostasis. In summary, these remodeling processes tuned photosynthesis according to the demands placed on the system and revealed the capability of C. merolae to grow under a broad range of temperatures. PMID:28270628

Effects of water stress on photosynthetic electron transport, photophosphorylation, and metabolite levels of Xanthium strumarium mesophyll cells.

PubMed

Sharkey, T D; Badger, M R

1982-12-01

Several component processes of photosynthesis were measured in osmotically stressed mesophyll cells of Xanthium strumarium L. The ribulose-1,5-bisphosphate regeneration capacity was reduced by water stress. Photophoshorylation was sensitive to water stress but photosynthetic electron transport was unaffected by water potentials down to-40 bar (-4 MPa). The concentrations of several intermediates of the photosynthetic carbon-reduction cycle remained relatively constant and did not indicate that ATP supply was limiting photosynthesis in the water-stressed cells.

Investigations of Iron Minerals Formed by Dissimilatory Alkaliphilic Bacterium with 57Fe Mössbauer Spectroscopy

NASA Astrophysics Data System (ADS)

Chistyakova, N. I.; Rusakov, V. S.; Shapkin, A. A.; Zhilina, T. N.; Zavarzina, D. G.; Lančok, A.; Kohout, J.

2010-07-01

Anaerobic alkaliphilic bacterium of Geoalkalibacter ferrihydriticus type (strain Z-0531), isolated from a bottom sediment sample from the weakly mineralized soda Lake Khadyn, have been analyzed. The strain uses the amorphous Fe(III)-hydroxide (AFH) as an electron acceptor and acetate CH3COO- as an electron donor. Mössbauer investigations of solid phase samples obtained during the process of the bacterium growth were carried out at room temperature, 77.8 K, 4.2 K without and with the presence of an external magnetic field (6 T) applied perpendicular to the γ-bebam.

Methods of mesophyll conductance estimation: its impact on key biochemical parameters and photosynthetic limitations in phosphorus-stressed soybean across CO2

USDA-ARS?s Scientific Manuscript database

Photosynthetic potential in C3 plants is largely limited by CO2 diffusion through stomata (Ls) and mesophyll (Lm) and photo-biochemical (Lb) processes. Accurate estimation of mesophyll conductance (gm) using gas exchange (GE) and chlorophyll fluorescence (CF) parameters of the photosynthetic proces...

Removal of Anabaena spiroides by potassium permanganate pre-oxidation: effect on photosynthetic capacity and molecular weight distribution.

PubMed

Qiao, Junlian; Zhang, Xiaodong; Lv, Liping

2017-11-01

Bench scale tests were conducted to investigate the effect of potassium permanganate pre-oxidation on the photosynthetic activity and molecular weight distribution of Anabaena spiroides. Different concentrations of potassium permanganate were added into the suspension of Anabaena spiroides, one of the dominant algae in water bloom, and after pre-oxidation of permanganate for 1 h, the results show that the removal rate significantly increases by 33.99~36.35% compared to direct coagulation. Then, the algal characteristics, including photosynthetic ability, the changes in extracellular organic matter three-dimensional fluorescence, and the distribution of molecular weight were conducted and the results show that along with increasing concentration of potassium permanganate, the photosynthetic ability of algae decreases, more extracellular organic matter is secreted, and large molecular weight matter (humic-like and fulvic-like substances) are generated. Therefore, this study demonstrates that potassium permanganate could be used in addressing the algae-rich water.

A photosynthetic-plasmonic-voltaic cell: Excitation of photosynthetic bacteria and current collection through a plasmonic substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samsonoff, Nathan; Ooms, Matthew D.; Sinton, David

2014-01-27

Excitation of photosynthetic biofilms using surface-confined evanescent light fields enables energy dense photobioreactors, while electrode-adhered biofilms can provide electricity directly. Here, we demonstrate concurrent light delivery and electron transport through a plasmonically excited metal film. Biofilms of cyanobacterium Synechococcus bacillaris on 50-nm gold films are excited via the Kretschmann configuration at λ = 670 nm. Cells show light/dark response to plasmonic excitation and grow denser biofilms, closer to the electrode surface, as compared to the direct irradiated case. Directly irradiated biofilms produced average electrical powers of 5.7 μW/m{sup 2} and plasmonically excited biofilms produced average electrical powers of 5.8 μW/m{sup 2}, with individual biofilmsmore » producing as much as 12 μW/m{sup 2}.« less

Studying the Symbiotic Bacterium Xenorhabdus nematophila in Individual, Living Steinernema carpocapsae Nematodes Using Microfluidic Systems.

PubMed

Stilwell, Matthew D; Cao, Mengyi; Goodrich-Blair, Heidi; Weibel, Douglas B

2018-01-01

Animal-microbe symbioses are ubiquitous in nature and scientifically important in diverse areas, including ecology, medicine, and agriculture. Steinernema nematodes and Xenorhabdus bacteria compose an established, successful model system for investigating microbial pathogenesis and mutualism. The bacterium Xenorhabdus nematophila is a species-specific mutualist of insect-infecting Steinernema carpocapsae nematodes. The bacterium colonizes a specialized intestinal pocket within the infective stage of the nematode, which transports the bacteria between insects that are killed and consumed by the pair for reproduction. Current understanding of the interaction between the infective-stage nematode and its bacterial colonizers is based largely on population-level, snapshot time point studies on these organisms. This limitation arises because investigating temporal dynamics of the bacterium within the nematode is impeded by the difficulty of isolating and maintaining individual living nematodes and tracking colonizing bacterial cells over time. To overcome this challenge, we developed a microfluidic system that enables us to spatially isolate and microscopically observe individual, living Steinernema nematodes and monitor the growth and development of the associated X. nematophila bacterial communities-starting from a single cell or a few cells-over weeks. Our data demonstrate, to our knowledge, the first direct, temporal, in vivo visual analysis of a symbiosis system and the application of this system to reveal continuous dynamics of the symbiont population in the living host animal. IMPORTANCE This paper describes an experimental system for directly investigating population dynamics of a symbiotic bacterium, Xenorhabdus nematophila , in its host-the infective stage of the entomopathogenic nematode Steinernema carpocapsae . Tracking individual and groups of bacteria in individual host nematodes over days and weeks yielded insight into dynamic growth and topology changes

Photosynthetic Activity in US Midwest

NASA Image and Video Library

2014-03-31

Amazing the things you can 'see' from space, if you just know how to look ... Satellite data show that during the Northern Hemisphere's growing season, the U.S. Midwest boasts more photosynthetic activity than any other spot on Earth. The magnitude of fluorescence portrayed in this visualization prompted researchers to take a closer look at the productivity of the U.S. Corn Belt. The glow represents fluorescence measured from land plants in early July, over a period from 2007 to 2011. Credit: NASA's Goddard Space Flight Center More here: go.nasa.gov/1jstros NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Tyrosine sulfation in a Gram-negative bacterium

PubMed Central

Han, Sang-Wook; Lee, Sang-Won; Bahar, Ofir; Schwessinger, Benjamin; Robinson, Michelle R.; Shaw, Jared B.; Madsen, James A.; Brodbelt, Jennifer S.; Ronald, Pamela C.

2015-01-01

Tyrosine sulfation, a well-characterized post-translation modification in eukaryotes, has not previously been reported in prokaryotes. Here we demonstrate that the RaxST protein from the Gram-negative bacterium, Xanthomonas oryzae pv. oryzae, is a tyrosine sulfotransferase. We used a newly developed sulfotransferase assay and ultraviolet photodissociation mass spectrometry (UVPD) to demonstrate that RaxST catalyzes sulfation of tyrosine 22 of the Xoo Ax21 (activator of XA21-mediated immunity). These results demonstrate a previously undescribed post-translational modification in a prokaryotic species with implications extending to host immune response and bacterial cell-cell communication system. PMID:23093190

Nuclear Photosynthetic Gene Expression Is Synergistically Modulated by Rates of Protein Synthesis in Chloroplasts and Mitochondria[W

PubMed Central

Pesaresi, Paolo; Masiero, Simona; Eubel, Holger; Braun, Hans-Peter; Bhushan, Shashi; Glaser, Elzbieta; Salamini, Francesco; Leister, Dario

2006-01-01

Arabidopsis thaliana mutants prors1-1 and -2 were identified on the basis of a decrease in effective photosystem II quantum yield. Mutations were localized to the 5′-untranslated region of the nuclear gene PROLYL-tRNA SYNTHETASE1 (PRORS1), which acts in both plastids and mitochondria. In prors1-1 and -2, PRORS1 expression is reduced, along with protein synthesis in both organelles. PRORS1 null alleles (prors1-3 and -4) result in embryo sac and embryo development arrest. In mutants with the leaky prors1-1 and -2 alleles, transcription of nuclear genes for proteins involved in photosynthetic light reactions is downregulated, whereas genes for other chloroplast proteins are upregulated. Downregulation of nuclear photosynthetic genes is not associated with a marked increase in the level of reactive oxygen species in leaves and persists in the dark, suggesting that the transcriptional response is light and photooxidative stress independent. The mrpl11 and prpl11 mutants are impaired in the mitochondrial and plastid ribosomal L11 proteins, respectively. The prpl11 mrpl11 double mutant, but neither of the single mutants, resulted in strong downregulation of nuclear photosynthetic genes, like that seen in leaky mutants for PRORS1, implying that, when organellar translation is perturbed, signals derived from both types of organelles cooperate in the regulation of nuclear photosynthetic gene expression. PMID:16517761

Chloroplastic ATP synthase optimizes the trade-off between photosynthetic CO2 assimilation and photoprotection during leaf maturation.

PubMed

Huang, Wei; Tikkanen, Mikko; Cai, Yan-Fei; Wang, Ji-Hua; Zhang, Shi-Bao

2018-06-11

In the present study, we studied the role of chloroplastic ATP synthase in photosynthetic regulation during leaf maturation. We measured gas exchange, chlorophyll fluorescence, P700 redox state, and the electrochromic shift signal in mature and immature leaves. Under high light, the immature leaves displayed high levels of non-photochemical quenching (NPQ) and P700 oxidation ratio, and higher values for proton motive force (pmf) and proton gradient (ΔpH) across the thylakoid membranes but lower values for the activity of chloroplastic ATP synthase (g H + ) than the mature leaves. Furthermore, g H + was significantly and positively correlated with CO 2 assimilation rate and linear electron flow (LEF), but negatively correlated with pmf and ΔpH. ΔpH was significantly correlated with LEF and the P700 oxidation ratio. These results indicated that g H + was regulated to match photosynthetic capacity during leaf maturation, and the formation of pmf and ΔpH was predominantly regulated by the alterations in g H + . In the immature leaves, the high steady-state ΔpH increased lumen acidification, which, in turn, stimulated photoprotection for the photosynthetic apparatus via NPQ induction and photosynthetic control. Our results highlighted the importance of chloroplastic ATP synthase in optimizing the trade-off between CO 2 assimilation and photoprotection during leaf maturation. Copyright © 2018. Published by Elsevier B.V.

Partial proteome of the corynetoxin-producing Gram-positive bacterium, Rathayibacter toxicus

USDA-ARS?s Scientific Manuscript database

Rathayibacter toxicus is a Gram-positive bacterium that is the causative agent of annual ryegrass toxicity (ARGT), a disease that causes devastating losses in the Australian livestock industry. R. toxicus exhibits a complex life cycle, using the nematode Anguina funesta as a physical vector to carry...

Light Affects the Chloroplast Ultrastructure and Post-Storage Photosynthetic Performance of Watermelon (Citrullus lanatus) Plug Seedlings

PubMed Central

Duan, Qingqing; Jiang, Wu; Ding, Ming; Lin, Ye; Huang, Danfeng

2014-01-01

Watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] plug seedlings were stored at 15°C in the light at a photosynthetic photon flux density of 15 µmol·m−2·s−1 or in darkness for 6 days, to evaluate their chloroplast ultrastructure, and associated photosynthetic characteristics. Storage in the dark caused swelling, disordered granal arrangement, and starch grain disappearance in the chloroplasts. In contrast, the chloroplasts stored in the light were relatively normal. As a result, the light-stored seedlings had a significantly higher chlorophyll content, Fv/Fm, and Pn than did dark-stored seedlings. Regardless of whether the seedlings were stored in light or darkness, the Gs and Ls of the seedlings significantly decreased, while the Ci obviously increased when the Pn decreased after 6 days of storage. This result suggests that the decreased Pn is not solely a stomatal effect, as the effects on the chloroplasts contributed to this photosynthetic inhibition. Six days after transplanting, seedlings that were stored in the light or darkness for 2 or 4 days showed complete recovery of chloroplast ultrastructure, chlorophyll content, Fv/Fm, Gs and Pn. When the storage period increased to 6 days, the dark-stored seedlings had a significantly lower Fv/Fm and Pn than the light-stored and control seedlings 6 days after transplanting, which was mainly ascribed to incomplete recovery of chloroplast ultrastructure. Furthermore, the light-stored seedlings exhibited a significantly higher shoot dry weight during storage and a higher percentage dry weight increase after transplanting than the dark-stored seedlings. These effects were enhanced by prolonged storage (4 to 6 days). This study demonstrated that dim light during storage is beneficial for maintaining chloroplast ultrastructure as well as photosynthetic efficiency in watermelon seedlings, thus contributing to the rapid recovery of post-storage photosynthetic performance, which ensures the transplant quality

Photosynthetic temperature responses of tree species in Rwanda: evidence of pronounced negative effects of high temperature in montane rainforest climax species.

PubMed

Vårhammar, Angelica; Wallin, Göran; McLean, Christopher M; Dusenge, Mirindi Eric; Medlyn, Belinda E; Hasper, Thomas B; Nsabimana, Donat; Uddling, Johan

2015-05-01

The sensitivity of photosynthetic metabolism to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial feedback on future climate change. While temperature responses of photosynthetic capacities have been comparatively well investigated in temperate species, the responses of tropical tree species remain unexplored. We compared the responses of seedlings of native cold-adapted tropical montane rainforest tree species with those of exotic warm-adapted plantation species, all growing in an intermediate temperature common garden in Rwanda. Leaf gas exchange responses to carbon dioxide (CO2 ) at different temperatures (20-40°C) were used to assess the temperature responses of biochemical photosynthetic capacities. Analyses revealed a lower optimum temperature for photosynthetic electron transport rates than for Rubisco carboxylation rates, along with lower electron transport optima in the native cold-adapted than in the exotic warm-adapted species. The photosynthetic optimum temperatures were generally exceeded by daytime peak leaf temperatures, in particular in the native montane rainforest climax species. This study thus provides evidence of pronounced negative effects of high temperature in tropical trees and indicates high susceptibility of montane rainforest climax species to future global warming. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Photosynthetic microbial mats in the 3,416-Myr-old ocean

NASA Astrophysics Data System (ADS)

Tice, Michael M.; Lowe, Donald R.

2004-09-01

Recent re-evaluations of the geological record of the earliest life on Earth have led to the suggestion that some of the oldest putative microfossils and carbonaceous matter were formed through abiotic hydrothermal processes. Similarly, many early Archaean (more than 3,400-Myr-old) cherts have been reinterpreted as hydrothermal deposits rather than products of normal marine sedimentary processes. Here we present the results of a field, petrographic and geochemical study testing these hypotheses for the 3,416-Myr-old Buck Reef Chert, South Africa. From sedimentary structures and distributions of sand and mud, we infer that deposition occurred in normal open shallow to deep marine environments. The siderite enrichment that we observe in deep-water sediments is consistent with a stratified early ocean. We show that most carbonaceous matter was formed by photosynthetic mats within the euphotic zone and distributed as detrital matter by waves and currents to surrounding environments. We find no evidence that hydrothermal processes had any direct role in the deposition of either the carbonaceous matter or the enclosing sediments. Instead, we conclude that photosynthetic organisms had evolved and were living in a stratified ocean supersaturated in dissolved silica 3,416Myr ago.

Photosynthetic microbial mats in the 3,416-Myr-old ocean.

PubMed

Tice, Michael M; Lowe, Donald R

2004-09-30

Recent re-evaluations of the geological record of the earliest life on Earth have led to the suggestion that some of the oldest putative microfossils and carbonaceous matter were formed through abiotic hydrothermal processes. Similarly, many early Archaean (more than 3,400-Myr-old) cherts have been reinterpreted as hydrothermal deposits rather than products of normal marine sedimentary processes. Here we present the results of a field, petrographic and geochemical study testing these hypotheses for the 3,416-Myr-old Buck Reef Chert, South Africa. From sedimentary structures and distributions of sand and mud, we infer that deposition occurred in normal open shallow to deep marine environments. The siderite enrichment that we observe in deep-water sediments is consistent with a stratified early ocean. We show that most carbonaceous matter was formed by photosynthetic mats within the euphotic zone and distributed as detrital matter by waves and currents to surrounding environments. We find no evidence that hydrothermal processes had any direct role in the deposition of either the carbonaceous matter or the enclosing sediments. Instead, we conclude that photosynthetic organisms had evolved and were living in a stratified ocean supersaturated in dissolved silica 3,416 Myr ago.

An Inexpensive Apparatus for Growing Photosynthetic Microorganisms in Exotic Atmospheres

NASA Astrophysics Data System (ADS)

Thomas, David J.; Herbert, Stephen K.

2005-02-01

Given the need for a light source, cyanobacteria and other photosynthetic microorganisms can be difficult and expensive to grow in large quantities. Lighted growth chambers and incubators typically cost 50-100% more than standard microbiological incubators. Self-shading of cells in liquid cultures prevents the growth of dense suspensions. Growing liquid cultures on a shaker table or lighted shaker incubator achieves greater cell densities, but adds considerably to the cost. For experiments in which gases other than air are required, the cost for conventional incubators increases even more. We describe an apparatus for growing photosynthetic organisms in exotic atmospheres that can be built relatively inexpensively (approximately $100 U.S.) using parts available from typical hardware or department stores (e.g., Wal-mart or K-mart). The apparatus uses microfiltered air (or other gases) to aerate, agitate, and mix liquid cultures, thus achieving very high cell densities (A750 > 3). Because gases are delivered to individual culture tubes, a variety of gas mixes can be used without the need for enclosed chambers. The apparatus works with liquid cultures of unicellular and filamentous species, and also works with agar slants.

Application of agglomerative clustering for analyzing phylogenetically on bacterium of saliva

NASA Astrophysics Data System (ADS)

Bustamam, A.; Fitria, I.; Umam, K.

2017-07-01

Analyzing population of Streptococcus bacteria is important since these species can cause dental caries, periodontal, halitosis (bad breath) and more problems. This paper will discuss the phylogenetically relation between the bacterium Streptococcus in saliva using a phylogenetic tree of agglomerative clustering methods. Starting with the bacterium Streptococcus DNA sequence obtained from the GenBank, then performed characteristic extraction of DNA sequences. The characteristic extraction result is matrix form, then performed normalization using min-max normalization and calculate genetic distance using Manhattan distance. Agglomerative clustering technique consisting of single linkage, complete linkage and average linkage. In this agglomerative algorithm number of group is started with the number of individual species. The most similar species is grouped until the similarity decreases and then formed a single group. Results of grouping is a phylogenetic tree and branches that join an established level of distance, that the smaller the distance the more the similarity of the larger species implementation is using R, an open source program.

Melanin from the Nitrogen-Fixing Bacterium Azotobacter chroococcum: A Spectroscopic Characterization

PubMed Central

Banerjee, Raja

2014-01-01

Melanins, the ubiquitous hetero-polymer pigments found widely dispersed among various life forms, are usually dark brown/black in colour. Although melanins have variety of biological functions, including protection against ultraviolet radiation of sunlight and are used in medicine, cosmetics, extraction of melanin from the animal and plant kingdoms is not an easy task. Using complementary physicochemical techniques (i.e. MALDI-TOF, FTIR absorption and cross-polarization magic angle spinning solid-state 13C NMR), we report here the characterization of melanins extracted from the nitrogen-fixing non-virulent bacterium Azotobacter chroococcum, a safe viable source. Moreover, considering dihydroxyindole moiety as the main constituent, an effort is made to propose the putative molecular structure of the melanin hetero-polymer extracted from the bacterium. Characterization of the melanin obtained from Azotobacter chroococcum would provide an inspiration in extending research activities on these hetero-polymers and their use as protective agent against UV radiation. PMID:24416247

Draft Genome Sequence of Arthrobacter sp. Strain SPG23, a Hydrocarbon-Degrading and Plant Growth-Promoting Soil Bacterium.

PubMed

Gkorezis, Panagiotis; Bottos, Eric M; Van Hamme, Jonathan D; Thijs, Sofie; Rineau, Francois; Franzetti, Andrea; Balseiro-Romero, Maria; Weyens, Nele; Vangronsveld, Jaco

2015-12-23

We report here the 4.7-Mb draft genome of Arthrobacter sp. SPG23, a hydrocarbonoclastic Gram-positive bacterium belonging to the Actinobacteria, isolated from diesel-contaminated soil at the Ford Motor Company site in Genk, Belgium. Strain SPG23 is a potent plant growth promoter useful for diesel fuel remediation applications based on plant-bacterium associations. Copyright © 2015 Gkorezis et al.

Draft Genome Sequence of Bacillus licheniformis Strain GB2, a Hydrocarbon-Degrading and Plant Growth-Promoting Soil Bacterium.

PubMed

Gkorezis, Panagiotis; Van Hamme, Jonathan; Bottos, Eric; Thijs, Sofie; Balseiro-Romero, Maria; Monterroso, Carmela; Kidd, Petra Suzan; Rineau, Francois; Weyens, Nele; Sillen, Wouter; Vangronsveld, Jaco

2016-06-23

We report the 4.39 Mb draft genome of Bacillus licheniformis GB2, a hydrocarbonoclastic Gram-positive bacterium of the family Bacillaceae, isolated from diesel-contaminated soil at the Ford Motor Company site in Genk, Belgium. Strain GB2 is an effective plant-growth promoter useful for diesel fuel remediation applications based on plant-bacterium associations. Copyright © 2016 Gkorezis et al.

Contributions of photosynthetic and non-photosynthetic cell types to leaf respiration in Vicia faba L. and their responses to growth temperature.

PubMed

Long, Benedict M; Bahar, Nur H A; Atkin, Owen K

2015-11-01

In intact leaves, mitochondrial populations are highly heterogeneous among contrasting cell types; how such contrasting populations respond to sustained changes in the environment remains, however, unclear. Here, we examined respiratory rates, mitochondrial protein composition and response to growth temperature in photosynthetic (mesophyll) and non-photosynthetic (epidermal) cells from fully expanded leaves of warm-developed (WD) and cold-developed (CD) broad bean (Vicia faba L.). Rates of respiration were significantly higher in mesophyll cell protoplasts (MCPs) than epidermal cell protoplasts (ECPs), with both protoplast types exhibiting capacity for cytochrome and alternative oxidase activity. Compared with ECPs, MCPs contained greater relative quantities of porin, suggesting higher mitochondrial surface area in mesophyll cells. Nevertheless, the relative quantities of respiratory proteins (normalized to porin) were similar in MCPs and ECPs, suggesting that ECPs have lower numbers of mitochondria yet similar protein complement to MCP mitochondria (albeit with lower abundance serine hydroxymethyltransferase). Several mitochondrial proteins (both non-photorespiratory and photorespiratory) exhibited an increased abundance in response to cold in both protoplast types. Based on estimates of individual protoplast respiration rates, combined with leaf cell abundance data, epidermal cells make a small but significant (2%) contribution to overall leaf respiration which increases twofold in the cold. Taken together, our data highlight the heterogeneous nature of mitochondrial populations in leaves, both among contrasting cell types and in how those populations respond to growth temperature. © 2015 John Wiley & Sons Ltd.