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Sample records for efficient symbiotic n-2-fixation

  1. A single evolutionary innovation drives the deep evolution of symbiotic N2-fixation in angiosperms.

    PubMed

    Werner, Gijsbert D A; Cornwell, William K; Sprent, Janet I; Kattge, Jens; Kiers, E Toby

    2014-06-10

    Symbiotic associations occur in every habitat on earth, but we know very little about their evolutionary histories. Current models of trait evolution cannot adequately reconstruct the deep history of symbiotic innovation, because they assume homogenous evolutionary processes across millions of years. Here we use a recently developed, heterogeneous and quantitative phylogenetic framework to study the origin of the symbiosis between angiosperms and nitrogen-fixing (N2) bacterial symbionts housed in nodules. We compile the largest database of global nodulating plant species and reconstruct the symbiosis' evolution. We identify a single, cryptic evolutionary innovation driving symbiotic N2-fixation evolution, followed by multiple gains and losses of the symbiosis, and the subsequent emergence of 'stable fixers' (clades extremely unlikely to lose the symbiosis). Originating over 100 MYA, this innovation suggests deep homology in symbiotic N2-fixation. Identifying cryptic innovations on the tree of life is key to understanding the evolution of complex traits, including symbiotic partnerships.

  2. A single evolutionary innovation drives the deep evolution of symbiotic N2-fixation in angiosperms

    PubMed Central

    Werner, Gijsbert D. A.; Cornwell, William K.; Sprent, Janet I.; Kattge, Jens; Kiers, E. Toby

    2014-01-01

    Symbiotic associations occur in every habitat on earth, but we know very little about their evolutionary histories. Current models of trait evolution cannot adequately reconstruct the deep history of symbiotic innovation, because they assume homogenous evolutionary processes across millions of years. Here we use a recently developed, heterogeneous and quantitative phylogenetic framework to study the origin of the symbiosis between angiosperms and nitrogen-fixing (N2) bacterial symbionts housed in nodules. We compile the largest database of global nodulating plant species and reconstruct the symbiosis’ evolution. We identify a single, cryptic evolutionary innovation driving symbiotic N2-fixation evolution, followed by multiple gains and losses of the symbiosis, and the subsequent emergence of ‘stable fixers’ (clades extremely unlikely to lose the symbiosis). Originating over 100 MYA, this innovation suggests deep homology in symbiotic N2-fixation. Identifying cryptic innovations on the tree of life is key to understanding the evolution of complex traits, including symbiotic partnerships. PMID:24912610

  3. Malic Enzyme Cofactor and Domain Requirements for Symbiotic N2 Fixation by Sinorhizobium meliloti▿ †

    PubMed Central

    Mitsch, Michael J.; Cowie, Alison; Finan, Turlough M.

    2007-01-01

    The NAD+-dependent malic enzyme (DME) and the NADP+-dependent malic enzyme (TME) of Sinorhizobium meliloti are representatives of a distinct class of malic enzymes that contain a 440-amino-acid N-terminal region homologous to other malic enzymes and a 330-amino-acid C-terminal region with similarity to phosphotransacetylase enzymes (PTA). We have shown previously that dme mutants of S. meliloti fail to fix N2 (Fix−) in alfalfa root nodules, whereas tme mutants are unimpaired in their N2-fixing ability (Fix+). Here we report that the amount of DME protein in bacteroids is 10 times greater than that of TME. We therefore investigated whether increased TME activity in nodules would allow TME to function in place of DME. The tme gene was placed under the control of the dme promoter, and despite elevated levels of TME within bacteroids, no symbiotic nitrogen fixation occurred in dme mutant strains. Conversely, expression of dme from the tme promoter resulted in a large reduction in DME activity and symbiotic N2 fixation. Hence, TME cannot replace the symbiotic requirement for DME. In further experiments we investigated the DME PTA-like domain and showed that it is not required for N2 fixation. Thus, expression of a DME C-terminal deletion derivative or the Escherichia coli NAD+-dependent malic enzyme (sfcA), both of which lack the PTA-like region, restored wild-type N2 fixation to a dme mutant. Our results have defined the symbiotic requirements for malic enzyme and raise the possibility that a constant high ratio of NADPH + H+ to NADP in nitrogen-fixing bacteroids prevents TME from functioning in N2-fixing bacteroids. PMID:17071765

  4. Isotopic Fractionation Associated With Symbiotic N2 Fixation and Uptake of NO3− by Plants 1

    PubMed Central

    Kohl, Daniel H.; Shearer, Georgia

    1980-01-01

    Isotopic fractionation associated with N2 fixation and NO3− uptake by plants are relevant to the accuracy of estimates of N2 fixation based on differences in the natural abundance of 15N between N2 fixing and nonfixing plants. The isotope effect on N2 fixation by soybeans (Glycine max [L] Merrill, variety Harosoy) and red clover (Trifolium pratense [L]) was determined from the difference in 15N abundance between atmospheric N2 and the total N of plants grown hydroponically with N-free nutrient solution. In soybeans the isotope effect was found to be +0.98 ± 0.18‰ (β = 0.99902). In clover the isotope effect was +1.88 ± 0.14‰ (β = 0.99812). The magnitude of these inverse isotope effects is small. However, they would lead to an underestimation of the amount of N2 fixed, since the N of atmospheric origin which finally appears in the plant is made richer in 15N by the inverse isotope effects than is atmospheric N2, and, to that degree, is attributed to soil-derived N in the calculation. Isotopic fractionation associated with NO3− uptake by plants does not have a critical effect on estimates of N2 fixation which are based on natural abundance of 15N since the 15N abundance of soil-derived N in plants is measured directly (i.e. after the N has undergone fractionation). Nevertheless, such fractionation is of some interest from the point of view of deciding upon the most appropriate sampling time. The isotope effect on NO3− uptake by a nonnodulating isoline of soybeans (variety Harosoy), marigold (Tagetes erecta [L]) and ryegrass (Lolium perenne [L]) was estimated from the difference between the 15N abundance of the total N of plants grown hydroponically and that of NO3− supplied in the medium. It was found to be about −5‰ (β = ∼1.005). PMID:16661392

  5. [Effectiveness of symbiotic n2-fixation in leguminous plants, as affected by inoculation with rhizobia, by substrate, n-fertilizing, and 14c-sucrose application (author's transl)].

    PubMed

    Merbach, W; Schilling, G

    1980-01-01

    Cultivation experiments (Mitscherlich-vessels, quartz sand, 15N-labelled soil, 15N-fertilizer) showed, that various strains of Rhizobium lupini (white and yellow lupines) and of Rhizobium leguminosarum (field beans and peas) induced a different N2-fixation of the inoculated plants, the most effective Rhizobium strains being 367a, Cz, T3, 271 (Rh. lupini), and Azotogen (Rh, leguminosarum). Yellow lupines and field bean plants were supplied with N2 from the air considerably better than white lupines and peas after inoculation with the most effective Rhizobium strains. Application of mineral N to the white lupines and peas not only substituted the inhibited N2-fixation, but increased N amounts in the plants. White lupines fixed more N2 under soil conditions than in quartz sand. An experiment with steam-sterilized and 15-labelled soil as a comparative substrate showed, that this finding was mainly caused by an additional Rhizobium infection from the soil. Contrary to field beans and yellow lupines which fix N2 up to ripeness, white lupines and peas finished N2-fixation in the time of flowering. Mineral-N applied at that time was an additional source of N for last-named plants and they utilized it for production of higher protein yields. Continual spraying of white lupine plants with 14C-labelled sucrose solution after the time of flowering caused continuance of N2-fixation up to the stage of ripeness. It is assumed that the cause of this effect was the competition of growing seeds and nodules for the photosynthates. The supply of nodules was inadequate without external sucrose application. Mineral N inhibited the sucrose-induced N2-fixation of white lupine nodules and their consumption of photosynthates. Consequently, the applied 14C was transported into seeds to a larger extent. The investigations allow the following conclusion: Effective N2-fixation requires nodules being a powerful sink for assimilates on the basis of a highly efficient photosynthetic system of the

  6. NAD(P)+-Malic Enzyme Mutants of Sinorhizobium sp. Strain NGR234, but Not Azorhizobium caulinodans ORS571, Maintain Symbiotic N2 Fixation Capabilities

    PubMed Central

    Zhang, Ye; Aono, Toshihiro; Poole, Phillip

    2012-01-01

    C4-dicarboxylic acids appear to be metabolized via the tricarboxylic acid (TCA) cycle in N2-fixing bacteria (bacteroids) within legume nodules. In Sinorhizobium meliloti bacteroids from alfalfa, NAD+-malic enzyme (DME) is required for N2 fixation, and this activity is thought to be required for the anaplerotic synthesis of pyruvate. In contrast, in the pea symbiont Rhizobium leguminosarum, pyruvate synthesis occurs via either DME or a pathway catalyzed by phosphoenolpyruvate carboxykinase (PCK) and pyruvate kinase (PYK). Here we report that dme mutants of the broad-host-range Sinorhizobium sp. strain NGR234 formed nodules whose level of N2 fixation varied from 27 to 83% (plant dry weight) of the wild-type level, depending on the host plant inoculated. NGR234 bacteroids had significant PCK activity, and while single pckA and single dme mutants fixed N2 at reduced rates, a pckA dme double mutant had no N2-fixing activity (Fix−). Thus, NGR234 bacteroids appear to synthesize pyruvate from TCA cycle intermediates via DME or PCK pathways. These NGR234 data, together with other reports, suggested that the completely Fix− phenotype of S. meliloti dme mutants may be specific to the alfalfa-S. meliloti symbiosis. We therefore examined the ME-like genes azc3656 and azc0119 from Azorhizobium caulinodans, as azc3656 mutants were previously shown to form Fix− nodules on the tropical legume Sesbania rostrata. We found that purified AZC3656 protein is an NAD(P)+-malic enzyme whose activity is inhibited by acetyl-coenzyme A (acetyl-CoA) and stimulated by succinate and fumarate. Thus, whereas DME is required for symbiotic N2 fixation in A. caulinodans and S. meliloti, in other rhizobia this activity can be bypassed via another pathway(s). PMID:22307295

  7. Symbiotic N2-Fixation Estimated by the 15N Tracer Technique and Growth of Pueraria phaseoloides (Roxb.) Benth. Inoculated with Bradyrhizobium Strain in Field Conditions

    PubMed Central

    Sarr, Papa Saliou; Okon, Judith Wase; Begoude, Didier Aime Boyogueno; Araki, Shigeru; Ambang, Zachée; Shibata, Makoto; Funakawa, Shinya

    2016-01-01

    This field experiment was established in Eastern Cameroon to examine the effect of selected rhizobial inoculation on N2-fixation and growth of Pueraria phaseoloides. Treatments consisted of noninoculated and Bradyrhizobium yuanmingense S3-4-inoculated Pueraria with three replications each. Ipomoea batatas as a non-N2-fixing reference was interspersed in each Pueraria plot. All the twelve plots received 2 gN/m2 of 15N ammonium sulfate 10% atom excess. At harvest, dry matter yields and the nitrogen derived from atmospheric N2-fixation (%Ndfa) of inoculated Pueraria were significantly (P < 0.05) higher (81% and 10.83%, resp.) than those of noninoculated Pueraria. The inoculation enhanced nodule dry weight 2.44-fold. Consequently, the harvested N significantly (P < 0.05) increased by 83% in inoculated Pueraria, resulting from the increase in N2-fixation and soil N uptake. A loss of 55 to 60% of the N fertilizer was reported, and 36 to 40% of it was immobilized in soil. Here, we demonstrated that both N2-fixing potential of P. phaseoloides and soil N uptake are improved through field inoculations using efficient bradyrhizobial species. In practice, the inoculation contributes to maximize N input in soils by the cover crop's biomass and represent a good strategy to improve soil fertility for subsequent cultivation. PMID:26904363

  8. Symbiotic N2 fixation activity in relation to C economy of Pisum sativum L. as a function of plant phenology.

    PubMed

    Voisin, A S; Salon, C; Jeudy, C; Warembourg, F R

    2003-12-01

    The relationships between symbiotic nitrogen fixation (SNF) activity and C fluxes were investigated in pea plants (Pisum sativum L. cv. Baccara) using simultaneous 13C and 15N labelling. Analysis of the dynamics of labelled CO2 efflux from the nodulated roots allowed the different components associated with SNF activity to be calculated, together with root and nodule synthetic and maintenance processes. The carbon costs for the synthesis of roots and nodules were similar and decreased with time. Carbon lost by turnover, associated with maintenance processes, decreased with time for nodules while it increased in the roots. Nodule turnover remained higher than root turnover until flowering. The effect of the N source on SNF was investigated using plants supplied with nitrate or plants only fixing N2. SNF per unit nodule biomass (nodule specific activity) was linearly related to the amount of carbon allocated to the nodulated roots regardless of the N source, with regression slopes decreasing across the growth cycle. These regression slopes permitted potential values of SNF specific activity to be defined. SNF activity decreased as the plants aged, presumably because of the combined effects of both increasing C costs of SNF (from 4.0 to 6.7 g C g-1 N) and the limitation of C supply to the nodules. SNF activity competed for C against synthesis and maintenance processes within the nodulated roots. Synthesis was the main limiting factor of SNF, but its importance decreased as the plant aged. At seed-filling, SNF was probably more limited by nodule age than by C supply to the nodulated roots.

  9. The model symbiotic association between Medicago truncatula cv. Jemalong and Rhizobium meliloti strain 2011 leads to N-stressed plants when symbiotic N2 fixation is the main N source for plant growth.

    PubMed

    Moreau, Delphine; Voisin, Anne-Sophie; Salon, Christophe; Munier-Jolain, Nathalie

    2008-01-01

    A better knowledge of the nitrogen nutrition of Medicago truncatula at the whole plant level and its modulation by environmental factors is a crucial step to reach a complete understanding of legume nitrogen nutrition. This study was based on the symbiotic system that is the most commonly used by the research community (M. truncatula cv. Jemalong A17 x Rhizobium meliloti strain 2011). Plant nitrogen nutrition was analysed in relation to carbon nutrition, under a range of nitrate concentrations in the nutrient solution and different light conditions. This study shows that this 'model symbiotic association' does not allow the plant to meet its nitrogen requirements, when dinitrogen fixation is the main nitrogen source for plant growth. A strong interaction between nitrogen and carbon nutrition was shown: when plant nitrogen requirements were not sustained, plant leaf area was much affected whereas photosynthesis per unit leaf area remained relatively stable. Both total nitrogen uptake and leaf area increased with increasing nitrate concentration in the nutrient solution; the magnitude of these responses varied according to the light conditions. Interestingly, the plant nitrogen nutrition level remained nearly unaffected by the light conditions. The observed nitrogen-limitation in this 'model symbiotic association' is an important finding for the research community. Based on practical recommendations regarding both the experimental conditions and the phenotypic traits to consider, a methodological framework was proposed to (i) help genomicists to assess plant nitrogen nutrition better, and (ii) assist in the detection of new genetic variants affected for nitrogen uptake in large-scale phenotyping studies.

  10. Genotypic Variation for N2-FIXATION in Voandzou (vigna Subterranea) Under P Deficiency and P Sufficiency

    NASA Astrophysics Data System (ADS)

    Andry, A.; Mahamadou, M.; Lilia, R.; Laurie, A.; Hélène, V.; Dominique, M.; Christian, M.; Jean-Jacques, D.

    2011-12-01

    Genetic variation associated with N2 fixation exists in numerous legume species (Graham, 2004). High symbiotic N2 fixation under P deficiency is related closely to nodulation which was used in legume selection for N2 fixation (Herridge and Rose, 2000). Until now, study of genetic potential of neglected crops like Vigna subterranea (bambara groundnut or voandzou) is often limited while its agronomic properties is interesting for the farmers of Africa. In order to assess the genotypic variation of voandzou for tolerance to phosphorus deficiency, a physiological approach of cultivar selection was performed with 54 cultivars from Madagascar, Niger and Mali in hydroponic culture under P deficiency and P sufficiency and inoculated with the reference strain of Bradyrhizobium sp. Vigna CB756. The results of nodulation and plant biomass, which are closely related, showed a large dispersion between cultivars (0.05-0.43 g nodule dry weight per plant and 0.50-5.51 g shoot dry weight per plant). The cultivars which presented the maximum growth during the experiment presented a high efficiency in use of the rhizobial symbiosis calculated as the slope of plant biomass regression as a function of nodulation. A large increase in nodulated-root O2 consumption under P deficiency was observed for the two most tolerant cultivars. The microscopic analysis with in situ RT-PCR of the nodule sections showed an increase of a phytase gene expression with tolerance of cultivars to P deficiency. From two most contrasting cultivars, an isotopic exchange method 32P was carried out on rhizosphere soil in rhizotron culture in order to assess the direct effect induced by the roots in terms of phosphorus mobilization. The rhizospheric effect was observed under P deficiency marked by a strong re-supplying capacity of soil solution in the diffusive phosphate ion between solid phase and soil solution leading to great phosphorus nutrition. These results highlight the genotypic variability among voandzou

  11. Salt-tolerant rhizobia isolated from a Tunisian oasis that are highly effective for symbiotic N2-fixation with Phaseolus vulgaris constitute a novel biovar (bv. mediterranense) of Sinorhizobium meliloti.

    PubMed

    Mnasri, Bacem; Mrabet, Moncef; Laguerre, Gisèle; Aouani, Mohamed Elarbi; Mhamdi, Ridha

    2007-01-01

    Nodulation of common bean was explored in six oases in the south of Tunisia. Nineteen isolates were characterized by PCR-RFLP of 16S rDNA. Three species of rhizobia were identified, Rhizobium etli, Rhizobium gallicum and Sinorhizobium meliloti. The diversity of the symbiotic genes was then assessed by PCR-RFLP of nodC and nifH genes. The majority of the symbiotic genotypes were conserved between oases and other soils of the north of the country. Sinorhizobia isolated from bean were then compared with isolates from Medicago truncatula plants grown in the oases soils. All the nodC types except for nodC type p that was specific to common bean isolates were shared by both hosts. The four isolates with nodC type p induced N(2)-fixing effective nodules on common bean but did not nodulate M. truncatula and Medicago sativa. The phylogenetic analysis of nifH and nodC genes showed that these isolates carry symbiotic genes different from those previously characterized among Medicago and bean symbionts, but closely related to those of S. fredii Spanish and Tunisian isolates effective in symbiosis with common bean but unable to nodulate soybean. The creation of a novel biovar shared by S. meliloti and S. fredii, bv. mediterranense, was proposed.

  12. Biological N2 fixation mainly controlled by Sphagnum tissue N:P ratio in ombrotrophic bogs

    NASA Astrophysics Data System (ADS)

    Zivkovic, Tatjana; Moore, Tim R.

    2017-04-01

    Most of the 18 Pg nitrogen (N) accumulated in northern nutrient-poor and Sphagnum-dominated peatlands (bogs and fens) can be attributed to N2-fixation by diazotrophs either associated with the live Sphagnum or non-symbiotically in the deeper peat such as through methane consumption close to the water table. Where atmospheric N deposition is low (< 0.2 g m-2 y-1), ombrotrophic bogs rely on N2-fixation as the primary source of N that sustains primary production. Due to high energetic requirements, N2-fixation depends on the available phosphorus (P). Anthropogenic impacts in the last 200 years increased atmospheric N deposition, resulting in a switch from N to P limitation in Sphagnum, suggested by the increase in tissue N:P to >16. It is unclear how Sphagnum-hosted diazotrophic activity may be affected by N deposition and thus changes in N:P ratio. First, we investigated the effects of long-term addition of different sources of nitrogen (0, 1.6, 3.2 and 6.4 g N m-2 y-1as NH4Cl and NaNO3), and phosphorus (5 g P m-2 y-1as KH2PO4) on Sphagnum nutrient status (N, P and N:P ratio), net primary productivity (NPP) and Sphagnum-associated N2fixation at Mer Bleue, a temperate ombrotrophic bog. We show that N concentration in Sphagnum tissue increased with larger rates of N addition, with a stronger effect on Sphagnum from NH4 than NO3. The addition of P created a 3.5 fold increase in Sphagnum P content compared to controls. Sphagnum NPP decreased linearly with the rise in N:P ratio, while linear growth declined exponentially with increase in Sphagnum N content. Rates of N2-fixation determined in the laboratory significantly decreased in response to even the smallest addition of both N species. In contrast, the addition of P increased N2 fixation by up to 100 times compared to N treatments and up to 5-30 times compared to controls. The change in N2-fixation was best modeled by the N:P ratio, across all experimental treatments. Secondly, to test the role of N:P ratio on N2

  13. Benthic N2 fixation in coral reefs and the potential effects of human-induced environmental change

    PubMed Central

    Cardini, Ulisse; Bednarz, Vanessa N; Foster, Rachel A; Wild, Christian

    2014-01-01

    Tropical coral reefs are among the most productive and diverse ecosystems, despite being surrounded by ocean waters where nutrients are in short supply. Benthic dinitrogen (N2) fixation is a significant internal source of “new” nitrogen (N) in reef ecosystems, but related information appears to be sparse. Here, we review the current state (and gaps) of knowledge on N2 fixation associated with coral reef organisms and their ecosystems. By summarizing the existing literature, we show that benthic N2 fixation is an omnipresent process in tropical reef environments. Highest N2 fixation rates are detected in reef-associated cyanobacterial mats and sea grass meadows, clearly showing the significance of these functional groups, if present, to the input of new N in reef ecosystems. Nonetheless, key benthic organisms such as hard corals also importantly contribute to benthic N2 fixation in the reef. Given the usually high coral coverage of healthy reef systems, these results indicate that benthic symbiotic associations may be more important than previously thought. In fact, mutualisms between carbon (C) and N2 fixers have likely evolved that may enable reef communities to mitigate N limitation. We then explore the potential effects of the increasing human interferences on the process of benthic reef N2 fixation via changes in diazotrophic populations, enzymatic activities, or availability of benthic substrates favorable to these microorganisms. Current knowledge indicates positive effects of ocean acidification, warming, and deoxygenation and negative effects of increased ultraviolet radiation on the amount of N fixed in coral reefs. Eutrophication may either boost or suppress N2 fixation, depending on the nutrient becoming limiting. As N2 fixation appears to play a fundamental role in nutrient-limited reef ecosystems, these assumptions need to be expanded and confirmed by future research efforts addressing the knowledge gaps identified in this review. PMID:24967086

  14. Benthic N2 fixation in coral reefs and the potential effects of human-induced environmental change.

    PubMed

    Cardini, Ulisse; Bednarz, Vanessa N; Foster, Rachel A; Wild, Christian

    2014-05-01

    Tropical coral reefs are among the most productive and diverse ecosystems, despite being surrounded by ocean waters where nutrients are in short supply. Benthic dinitrogen (N2) fixation is a significant internal source of "new" nitrogen (N) in reef ecosystems, but related information appears to be sparse. Here, we review the current state (and gaps) of knowledge on N2 fixation associated with coral reef organisms and their ecosystems. By summarizing the existing literature, we show that benthic N2 fixation is an omnipresent process in tropical reef environments. Highest N2 fixation rates are detected in reef-associated cyanobacterial mats and sea grass meadows, clearly showing the significance of these functional groups, if present, to the input of new N in reef ecosystems. Nonetheless, key benthic organisms such as hard corals also importantly contribute to benthic N2 fixation in the reef. Given the usually high coral coverage of healthy reef systems, these results indicate that benthic symbiotic associations may be more important than previously thought. In fact, mutualisms between carbon (C) and N2 fixers have likely evolved that may enable reef communities to mitigate N limitation. We then explore the potential effects of the increasing human interferences on the process of benthic reef N2 fixation via changes in diazotrophic populations, enzymatic activities, or availability of benthic substrates favorable to these microorganisms. Current knowledge indicates positive effects of ocean acidification, warming, and deoxygenation and negative effects of increased ultraviolet radiation on the amount of N fixed in coral reefs. Eutrophication may either boost or suppress N2 fixation, depending on the nutrient becoming limiting. As N2 fixation appears to play a fundamental role in nutrient-limited reef ecosystems, these assumptions need to be expanded and confirmed by future research efforts addressing the knowledge gaps identified in this review.

  15. Nitrogen and Phosphorus Addition Affects Biological N2 Fixation and Sphagnum Moss in an Ombrotrophic Bog

    NASA Astrophysics Data System (ADS)

    Zivkovic, T.; Ardichvili, A.; Moore, T. R.

    2016-12-01

    Most of the 18 Pg nitrogen (N) accumulated in northern nutrient-poor and Sphagnum-dominated peatlands (bogs and fens) can be attributed to N2 fixation by diazotrophs either associated with the live Sphagnum or non-symbiotically in the deeper peat. Where atmospheric N deposition is low (< 0.2 g m-2 y-1), ombrotrophic bogs rely on N2 fixation as the primary source of N that sustains primary production. The industrial revolution and anthropogenic impacts in the last 200 years have resulted in larger atmospheric N deposition as ammonium (NH4) and nitrate (NO3). One effect of increased N deposition in Sphagnum is a switch from N to phosphorus (P) limitation suggested by the increase in tissue N:P>16. It is unclear how Sphagnum hosted diazotrophic activity may be affected by N deposition and thus changes in N:P ratio. We investigated the effects of long-term addition of different sources of nitrogen (0, 1.6, 3.2 and 6.4 g N m-2 y-1 as NH4Cl and NaNO3), and phosphorus (5 g P m-2 y-1 as KH2PO4) on Sphagnum nutrient status (N, P and N:P), net primary productivity (NPP) and Sphagnum-associated N2 fixation at Mer Bleue, a temperate ombrotrophic bog. Our study shows that N concentration in Sphagnum tissue increased with larger rates of N addition, with a stronger effect on Sphagnum from NH4 than NO3. The addition of P created a 3.5 fold increase in Sphagnum P content compared to controls. Sphagnum NPP decreased linearly with the rise in N:P ratio, while linear growth declined exponentially with increase in Sphagnum N content. N2 fixation significantly decreased in response to even the smallest addition of both N species. In contrast, the addition of P increased N2 fixation by up to 100 times compared to N treatments and up to 5-30 times compared to controls. The change in N2 fixation was best modeled by the N:P ratio, across all experimental treatments. Although elevated N deposition substantially decreases N2 fixation, the N:P ratio in Sphagnum may be a good predictor, likely

  16. Strong stimulation of N2 fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms

    NASA Astrophysics Data System (ADS)

    Ridame, C.; Guieu, C.; L'Helguen, S.

    2013-06-01

    The response of N2 fixation to contrasted (wet and dry) Saharan dust deposition was studied in the framework of the DUNE project "a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem" during which realistic simulations of dust deposition (10 g mN2 fixation indicating that both wet and dry Saharan dust depositions were able to relieve efficiently the nutrient limitation(s) of N2 fixation. This means in particular that N2 fixation activity was not inhibited by the NO3- input associated with the simulated wet deposition. The contribution of N2 fixation to primary production was negligible before (on average 0.4%) and after (on average 1%) dust additions in all experiments indicating that N2 fixation was a poor contributor to the N demand for primary production. Before seedings, new production (NP) was mainly supported by NO3- as a source of N as shown by the low contribution of N2 fixation to NP (on average 3%). Despite the stimulation of N2 fixation by dust, the rates remained low, and did not allow to significantly change the contribution of N2 fixation to NP as a maximum of 10% contribution was evidenced. A comparison of the responses of N2 fixation by diazotrophs and CO2 fixation by the whole phytoplankton community suggests that those metabolic processes were limited or co-limited by different nutrients. The estimated input of new nitrogen (NO3-) from simulated wet deposition was much higher than that associated with N2 fixation. We confirm that although the biogeochemical

  17. Assessing N2 fixation in estuarine mangrove soils

    NASA Astrophysics Data System (ADS)

    Shiau, Yo-Jin; Lin, Ming-Fen; Tan, Chen-Chung; Tian, Guanglong; Chiu, Chih-Yu

    2017-04-01

    Nitrogen (N) limited mangrove forest may have a high potential for microbial N2 fixation. Previous research has focused on soil nitrogenase activity in pristine mangrove forests with little anthropogenic impact. This research was designed to evaluate the magnitude of nitrogenase activity of mangrove soils in a high anthropogenic N-loading environment and the way in which soil N2 fixation in mangrove forest may be related to organic carbon and salinity. The test involved an acetylene reduction method under controlled laboratory conditions. The mangrove forests with high anthropogenic N loading may have high nitrogenase activity in the soils. The diazotrophs in these mangrove soils were mostly heterotrophs and the sulfate-reducing bacteria were the major N2-fixing bacteria. The nitrogenase activity was little affected by the soil salinity, which suggests that these groups of N2 fixation bacteria adapted well to saline conditions in the estuary.

  18. Strong stimulation of N2 fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms

    NASA Astrophysics Data System (ADS)

    Ridame, C.; Guieu, C.; L'Helguen, S.

    2013-11-01

    The response of N2 (dinitrogen) fixation to contrasted (wet and dry) Saharan dust deposition was studied in the framework of the DUNE project (a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem) during which realistic simulations of dust deposition (10 g m-2) into large mesocosms (52 m3) were performed. Three distinct experimental dust additions were conducted in June 2008 (DUNE-1-P: simulation of a wet deposition, DUNE-1-Q: simulation of a dry deposition) and 2010 (DUNE-2-R: simulation of 2 successive wet depositions) in the northwestern oligotrophic Mediterranean Sea. Here we show that wet and dry dust deposition induced a rapid (24 h or 48 h after dust additions), strong (from 2- to 5.3-fold) and long (at least 4-6 days duration) increase in N2 fixation, indicating that both wet and dry Saharan dust deposition was able to relieve efficiently the nutrient limitation(s) of N2 fixation. This means in particular that N2 fixation activity was not inhibited by the significant input of nitrate associated with the simulated wet deposition (~ 9 mmol NO3- m-2). The input of new nitrogen associated with N2 fixation was negligible relative to the atmospheric NO3- input associated with the dust. The contribution of N2 fixation to primary production was negligible (≤ 1%) before and after dust addition in all experiments, indicating that N2 fixation was a poor contributor to the nitrogen demand for primary production. Despite the stimulation of N2 fixation by dust addition, the rates remained low, and did not significantly change the contribution of N2 fixation to new production since only a maximum contribution of 10% was observed. The response of N2 fixation by diazotrophs and CO2 fixation by the whole phytoplankton community suggests that these metabolic processes were limited or co-limited by different nutrients. With this novel approach, which allows us to study processes as a function of time while atmospheric particles are sinking, we show that new

  19. Legumes, N2 fixation and the H2 cycle

    NASA Astrophysics Data System (ADS)

    Layzell, D. B.

    2004-12-01

    Legume plants such as soybean or pea can form symbiotic, N2 fixing associations with bacteria that exist in root nodules. For every N2 fixed, 1 to 3 H2 are produced as a by-product of the nitrogenase reaction. Therefore, a typical N2 fixing legume crop produces about 200,000 L H2 gas (at STP) per hectare per crop season. This paper will summarize our current understanding of the processes leading to H2 production in legumes, the magnitude of H2 production associated with global cropping systems, and the implications for its production and oxidation on both the legumes and the soils in which they grow. Specific points may include: ˜ In symbioses lacking uptake hydrogenase (HUP) activity (thought to be the majority of crop legumes), the H2 diffuses into the soil where it is oxidized by soil microbes that grow up around the legume nodules. The kinetic properties of these microbes are very different (higher Km and Vmax) from that of microbes in soils exposed to normal air (ca. 0.5 ppm H2); ˜ Laboratory studies indicate that 60% of the reducing power from H2 is coupled to O2 uptake, whereas 40% is coupled to autotrophic CO2 fixation. The latter process should increase soil carbon stocks by about 25 kg C/ha/yr; ˜ At the site of the nitrogenase enzyme, H2 production is autocatalytic such that the higher the H2 concentration, the more H2 is produced and the less N2 fixed. The variable O2 diffusion barrier in legumes can act to restrict H2 diffusion from the nodule, thereby increasing the relative magnitude of H2 production versus N2 fixation; ˜ Studies to understand why legume symbioses make such an energy investment in H2 production have led to the discovery that H2 treated soils have improved fertility, supporting the growth and yield of legume and non-legume crops. This observation may account for the benefits of legumes when used in rotation with cereal crops, a phenomenon that has been used by farmers for over 2000 years, but which has remained unexplained. An

  20. N2 fixation in the rhizosphere of Thalassia testudinum.

    PubMed

    Capone, D G; Taylor, B F

    1980-08-01

    N2 fixation (C2H2 reduction) associated with the roots, rhizomes, and sediments (rhizosphere cores) of the seagrass Thalassia testudinum was measured at sites in South Florida (Soldier Key, Biscayne Bay) and the Bahamas (Bimini Harbor). Rates of C2H2 reduction were higher in anaerobic than in aerobic assays and were linear for several hours after an initial lag period of 1-2h. Nitrogenase activity was proportional to the weight of rhizomes plus roots but showed no correlation with the total weight of the rhizosphere cores. C2H2 reduction occurred to depths of at least 30 cm but the majority (<85%) of the activity was in the 0- to 20-cm fraction; also the ratio of activities for the 0- to 10- and 10- to 20-cm depths was about 2:1. Most investigations were carried out using anaerobic assays of the 0- to 10-cm fractions and rates calculated for the period of 3-6 h after adding C2H2. These rates were not stimulated by organic compounds (glucose, lactate, succinate) but were approximately halved by a decrease in temperature of 10 degrees C. In a seasonal study at Soldier Key the rates of N2 fixation varied about 20-fold with maximal rates in late summer and minimal rates in winter (January). On a diurnal basis, C2H2 reduction increased in the morning but was depressed in midafternoon, probably due to O2 buildup in the rhizosphere. Daily rates of N2 fixation, during the summer months of 1975-1978, varied between 5 and 24 mg N (-2)m and the estimated annual rates of N2 fixation were 10-50 kg N (-1)ha, taking into account seasonal variations and activities to a depth of 20 cm.

  1. Global N2 fixation and its response to global climate change and increasing CO2 level

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Houlton, B. Z.; Field, C. B.; Vitousek, P. M.

    2007-12-01

    Biological nitrogen fixation is the largest nitrogen input to many natural terrestrial ecosystems, particularly tropical ecosystems, thereby influencing primary production, CO2 uptake, and responses to climate change. However, our understanding of biological nitrogen fixation is still very limited, and the dominant plant family capable of fixing N2 symbiotically, the Leguminasae, exhibits considerable geographic variation in the terrestrial biosphere. Based on the principles of resource optimization, we developed a new model to constrain our understanding of the geographic distribution of N fixation globally. Our model treats N fixation according to the C cost of fixing N, coupled with the N cost associated with acquiring P from the soil for plant growth. The model was used to estimate the rate of global symbiotic N2 fixation and the response of symbiotic N2 fixers to changes in climate and rising atmospheric CO2. We shall discuss global N limitation of terrestrial carbon uptake and its implications for climate-carbon cycle feedbacks from present to year 2100.

  2. Isotope evidence for N2-fixation in Sphagnum peat bogs

    NASA Astrophysics Data System (ADS)

    Novak, Martin; Jackova, Ivana; Buzek, Frantisek; Stepanova, Marketa; Veselovsky, Frantisek; Curik, Jan; Prechova, Eva

    2016-04-01

    Waterlogged organic soils store as much as 30 % of the world's soil carbon (C), and 15 % of the world's soil nitrogen (N). In the era of climate change, wetlands are vulnerable to increasing temperatures and prolonged periods of low rainfall. Higher rates of microbial processes and/or changing availability of oxygen may lead to peat thinning and elevated emissions of greenhouse gases (mostly CO2, but also CH4 and N2O). Biogeochemical cycling of C and N in peat bogs is coupled. Under low levels of pollution by reactive nitrogen (NO3-, NH4+), increasing N inputs may positively affect C storage in peat. Recent studies in North America and Scandinavia have suggested that pristine bogs are characterized by significant rates of microbial N2 fixation that augments C storage in the peat substrate. We present a nitrogen isotope study aimed at corroborating these findings. We conducted an isotope inventory of N fluxes and pools at two Sphagnum-dominated ombrotrophic peat bogs in the Czech Republic (Central Europe). For the first time, we present a time-series of del15N values of atmospheric input at the same locations as del15N values of living Sphagnum and peat. The mean del15N values systematically increased in the order: input NH4+ (-10.0 ‰) < input NO3- (-7.9 ‰) < peat porewater (-5.6 ‰) < Sphagnum (-5.0 ‰) < shallow peat (-4.2 ‰) < deep peat (-2.2 ‰) < runoff (-1.4 ‰) < porewater N2O (1.4 ‰). Importantly, N of Sphagnum was isotopically heavier than N of the atmospheric input (p < 0.001). If partial incorporation of reactive N from the atmosphere into Sphagnum was isotopically selective, the residual N would have to be isotopically extremely light. Such N, however, was not identified anywhere in the ecosystem. Alternatively, Sphagnum may have contained an admixture of isotopically heavier N from atmospheric N2 (del15N N2 = 0 ‰). We conlude that the N isotope systematics at the two Czech sites is consistent with the concept of significant N2 fixation

  3. Are watershed and lacustrine controls on planktonic N2 fixation hierarchically structured?

    PubMed

    Scott, J Thad; Doyle, Robert D; Prochnow, Shane J; White, Joseph D

    2008-04-01

    N2 fixation can be an important source of N to limnetic ecosystems and can influence the structure of phytoplankton communities. However, watershed-scale conditions that favor N2 fixation in lakes and reservoirs have not been well studied. We measured N2 fixation and lacustrine variables monthly over a 19-month period in Waco Reservoir, Texas, USA, and linked these data with nutrient-loading estimates from a physically based watershed model. Readily available topographic, soil, land cover, effluent discharge, and climate data were used in the Soil and Water Assessment Tool (SWAT) to derive watershed nutrient-loading estimates. Categorical and regression tree (CART) analysis revealed that lacustrine and watershed correlates of N2 fixation were hierarchically structured. Lacustrine conditions showed greater predictive capability temporally. For instance, low NO3(-) concentration (<25 microg N/L) and high water temperatures (>27 degrees C) in the reservoir were correlated with the initiation of N2 fixation seasonally. When lacustrine conditions were favorable for N2 fixation, watershed conditions appeared to influence spatial patterns of N2 fixation within the reservoir. For example, spatially explicit patterns of N2 fixation were correlated with the ratio of N:P in nutrient loadings and the N loading rate, which were driven by anthropogenic activity in the watershed and periods of low stream flow, respectively. Although N2 fixation contributed <5% of the annual N load to the reservoir, 37% of the N load was derived from atmospheric N2 fixation during summertime when stream flow in the watershed was low. This study provides evidence that watershed anthropogenic activity can exert control on planktonic N2 fixation, but that temporality is controlled by lacustrine conditions. Furthermore, this study also supports suggestions that reduced inflows may increase the propensity of N2-fixing cyanobacterial blooms in receiving waters of anthropogenically modified landscapes.

  4. Diurnal variation in n(2) fixation and photosynthesis by aquatic blue-green algae.

    PubMed

    Peterson, R B; Friberg, E E; Burris, R H

    1977-01-01

    Rates of (14)CO(2) fixation, O(2) evolution, and N(2) fixation (acetylene reduction) by natural populations of blue-green algae recovered from Lake Mendota were measured at frequent intervals between sunrise and sunset. Photosynthesis and N(2) fixation were depressed during midday when light intensity was greatest. As the light intensity rose, most of the algal population migrated to deeper, light-limited waters where radiation damage would be diminished. As the relative rate of N(2) fixation compared to CO(2) fixation increases with depth, it is suggested that the algae maintain balanced growth by migrating vertically via buoyancy regulation. High concentrations of dissolved O(2) in lake water may inhibit N(2) fixation by enhancing photorespiration. Several factors such as photosynthetic rate, light intensity, dissolved O(2), species composition, and vertical and horizontal migration all affect observed rates of in situ N(2) fixation.

  5. Inhibition of N2 fixation in soybean is associated with elevated ureides and amino acids.

    PubMed

    King, C Andy; Purcell, Larry C

    2005-04-01

    Decreased N2 fixation in soybean (Glycine max) L. Merr. during water deficits has been associated with increases in ureides and free amino acids in plant tissues, indicating a potential feedback inhibition by these compounds in response to drought. We evaluated concentrations of ureides and amino acids in leaf and nodule tissue and the concurrent change in N2 fixation in response to exogenous ureides and soil-water treatments for the cultivars Jackson and KS4895. Exogenous ureides applied to the soil and water-deficit treatments inhibited N2 fixation by 85% to 90%. Mn fertilization increased the apparent catabolism of ureides in leaves and hastened the recovery of N2 fixation following exogenous ureide application for both cultivars. Ureides and total free amino acids in leaves and nodules increased during water deficits and coincided with a decline in N2 fixation for both cultivars. N2 fixation recovered to 74% to 90% of control levels 2 d after rewatering drought-stressed plants, but leaf ureides and total nodule amino acids remained elevated in KS4895. Asparagine accounted for 82% of the increase in nodule amino acids relative to well-watered plants at 2 d after rewatering. These results indicate that leaf ureides and nodule asparagine do not feedback inhibit N2 fixation. Compounds whose increase and decrease in concentration mirrored the decline and recovery of N2 fixation included nodule ureides, nodule aspartate, and several amino acids in leaves, indicating that these are potential candidate molecules for feedback inhibition of N2 fixation.

  6. Inhibition of N2 Fixation in Soybean Is Associated with Elevated Ureides and Amino Acids1

    PubMed Central

    King, C. Andy; Purcell, Larry C.

    2005-01-01

    Decreased N2 fixation in soybean (Glycine max) L. Merr. during water deficits has been associated with increases in ureides and free amino acids in plant tissues, indicating a potential feedback inhibition by these compounds in response to drought. We evaluated concentrations of ureides and amino acids in leaf and nodule tissue and the concurrent change in N2 fixation in response to exogenous ureides and soil-water treatments for the cultivars Jackson and KS4895. Exogenous ureides applied to the soil and water-deficit treatments inhibited N2 fixation by 85% to 90%. Mn fertilization increased the apparent catabolism of ureides in leaves and hastened the recovery of N2 fixation following exogenous ureide application for both cultivars. Ureides and total free amino acids in leaves and nodules increased during water deficits and coincided with a decline in N2 fixation for both cultivars. N2 fixation recovered to 74% to 90% of control levels 2 d after rewatering drought-stressed plants, but leaf ureides and total nodule amino acids remained elevated in KS4895. Asparagine accounted for 82% of the increase in nodule amino acids relative to well-watered plants at 2 d after rewatering. These results indicate that leaf ureides and nodule asparagine do not feedback inhibit N2 fixation. Compounds whose increase and decrease in concentration mirrored the decline and recovery of N2 fixation included nodule ureides, nodule aspartate, and several amino acids in leaves, indicating that these are potential candidate molecules for feedback inhibition of N2 fixation. PMID:15778462

  7. Growth, N2 fixation and photosynthesis in a cyanobacterium, Trichodesmium sp., under Fe stress.

    PubMed

    Fu, Fei-xue; Bell, P R

    2003-04-01

    Trichodesmium sp., isolated from the Great Barrier Reef lagoon, was cultured in artificial seawater media containing a range of Fe concentration. Fe additions stimulated growth, N2 fixation, cellular chlorophyll a content, light-saturated chlorophyll a-specific gross photosynthetic capacity (Pmchl a) and the dark respiration rate (Rdchl a). Cell yields only doubled for 9 nM Fe relative to zero added Fe, whereas N2 fixation increased 11-fold considerably for 450 nM Fe. The results suggest that N2 fixation of Trichodesmium is more sensitive to Fe limitation than are the cell yields.

  8. Novel Lipid Biomarkers for Past Oceanic N2 Fixation

    NASA Astrophysics Data System (ADS)

    Bale, N. J.; Hopmans, E. C.; Villareal, T. A.; Zell, C. I.; Sinninghe Damsté, , J.; Schouten, S.

    2014-12-01

    Nitrogen-fixing cyanobacteria play important roles in the biogeochemical cycles of aquatic systems. Both heterocystous and non-heterocystous N2-fixing cyanobacteria are symbiotic with marine diatoms and thrive in low nutrient environments. These associations are significant exporters of carbon to the deep-sea, but suitable tracers for reconstructing their importance in past environments are lacking. We recently analyzed the heterocyst glycolipids (HGs) of the heterocystous Richelia intracellularis symbiont of the marine diatoms Hemiaulus hauckii and H. membranaceus and found unique C5 glycolipids with C30-32 carbon chains, a structure different from the C6 glycolipids detected in freshwater heterocystous cyanobacteria. We developed a high performance liquid chromatography/ multiple reaction monitoring mass spectrometry (HPLC/MS) method specific for trace analysis of long chain C5 HGs and applied it to suspended particulate matter (SPM) and surface sediment from the Amazon plume, a region known to harbor marine diatoms carrying heterocystous cyanobacteria as endosymbionts. C5 HGs were detected in both SPM and sediments demonstrating their biomarker potential. They were not detected in SPM or sediment from freshwater settings in the region. Rather, limnetic SPM and sediments contained C6 HGs which are established biomarkers for free-living heterocystous cyanobacteria. Glycolipids have been found preserved in sediments of up to 49 Ma old. Our development of the C5 biomarkers has the potential to improve our knowledge of the contribution of symbiotic cyanobacteria to the paleo-N-cycle.

  9. Root exudates drive interspecific facilitation by enhancing nodulation and N2 fixation

    PubMed Central

    Li, Bai; Li, Yu-Ying; Wu, Hua-Mao; Zhang, Fang-Fang; Li, Chun-Jie; Li, Xue-Xian; Lambers, Hans; Li, Long

    2016-01-01

    Plant diversity in experimental systems often enhances ecosystem productivity, but the mechanisms causing this overyielding are only partly understood. Intercropping faba beans (Vicia faba L.) and maize (Zea mays L.) result in overyielding and also, enhanced nodulation by faba beans. By using permeable and impermeable root barriers in a 2-y field experiment, we show that root–root interactions between faba bean and maize significantly increase both nodulation and symbiotic N2 fixation in intercropped faba bean. Furthermore, root exudates from maize promote faba bean nodulation, whereas root exudates from wheat and barley do not. Thus, a decline of soil nitrate concentrations caused by intercropped cereals is not the sole mechanism for maize promoting faba bean nodulation. Intercropped maize also caused a twofold increase in exudation of flavonoids (signaling compounds for rhizobia) in the systems. Roots of faba bean treated with maize root exudates exhibited an immediate 11-fold increase in the expression of chalcone–flavanone isomerase (involved in flavonoid synthesis) gene together with a significantly increased expression of genes mediating nodulation and auxin response. After 35 d, faba beans treated with maize root exudate continued to show up-regulation of key nodulation genes, such as early nodulin 93 (ENOD93), and promoted nitrogen fixation. Our results reveal a mechanism for how intercropped maize promotes nitrogen fixation of faba bean, where maize root exudates promote flavonoid synthesis in faba bean, increase nodulation, and stimulate nitrogen fixation after enhanced gene expression. These results indicate facilitative root–root interactions and provide a mechanism for a positive relationship between species diversity and ecosystem productivity. PMID:27217575

  10. Root exudates drive interspecific facilitation by enhancing nodulation and N2 fixation.

    PubMed

    Li, Bai; Li, Yu-Ying; Wu, Hua-Mao; Zhang, Fang-Fang; Li, Chun-Jie; Li, Xue-Xian; Lambers, Hans; Li, Long

    2016-06-07

    Plant diversity in experimental systems often enhances ecosystem productivity, but the mechanisms causing this overyielding are only partly understood. Intercropping faba beans (Vicia faba L.) and maize (Zea mays L.) result in overyielding and also, enhanced nodulation by faba beans. By using permeable and impermeable root barriers in a 2-y field experiment, we show that root-root interactions between faba bean and maize significantly increase both nodulation and symbiotic N2 fixation in intercropped faba bean. Furthermore, root exudates from maize promote faba bean nodulation, whereas root exudates from wheat and barley do not. Thus, a decline of soil nitrate concentrations caused by intercropped cereals is not the sole mechanism for maize promoting faba bean nodulation. Intercropped maize also caused a twofold increase in exudation of flavonoids (signaling compounds for rhizobia) in the systems. Roots of faba bean treated with maize root exudates exhibited an immediate 11-fold increase in the expression of chalcone-flavanone isomerase (involved in flavonoid synthesis) gene together with a significantly increased expression of genes mediating nodulation and auxin response. After 35 d, faba beans treated with maize root exudate continued to show up-regulation of key nodulation genes, such as early nodulin 93 (ENOD93), and promoted nitrogen fixation. Our results reveal a mechanism for how intercropped maize promotes nitrogen fixation of faba bean, where maize root exudates promote flavonoid synthesis in faba bean, increase nodulation, and stimulate nitrogen fixation after enhanced gene expression. These results indicate facilitative root-root interactions and provide a mechanism for a positive relationship between species diversity and ecosystem productivity.

  11. N2 fixation in eddies of the eastern tropical South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Loscher, Carolin R.; Bourbonnais, Annie; Dekaezemacker, Julien; Charoenpong, Chawalit N.; Altabet, Mark A.; Bange, Hermann W.; Czeschel, Rena; Hoffmann, Chris; Schmitz, Ruth

    2016-05-01

    Mesoscale eddies play a major role in controlling ocean biogeochemistry. By impacting nutrient availability and water column ventilation, they are of critical importance for oceanic primary production. In the eastern tropical South Pacific Ocean off Peru, where a large and persistent oxygen-deficient zone is present, mesoscale processes have been reported to occur frequently. However, investigations into their biological activity are mostly based on model simulations, and direct measurements of carbon and dinitrogen (N2) fixation are scarce.We examined an open-ocean cyclonic eddy and two anticyclonic mode water eddies: a coastal one and an open-ocean one in the waters off Peru along a section at 16° S in austral summer 2012. Molecular data and bioassay incubations point towards a difference between the active diazotrophic communities present in the cyclonic eddy and the anticyclonic mode water eddies.In the cyclonic eddy, highest rates of N2 fixation were measured in surface waters but no N2 fixation signal was detected at intermediate water depths. In contrast, both anticyclonic mode water eddies showed pronounced maxima in N2 fixation below the euphotic zone as evidenced by rate measurements and geochemical data. N2 fixation and carbon (C) fixation were higher in the young coastal mode water eddy compared to the older offshore mode water eddy. A co-occurrence between N2 fixation and biogenic N2, an indicator for N loss, indicated a link between N loss and N2 fixation in the mode water eddies, which was not observed for the cyclonic eddy. The comparison of two consecutive surveys of the coastal mode water eddy in November 2012 and December 2012 also revealed a reduction in N2 and C fixation at intermediate depths along with a reduction in chlorophyll by half, mirroring an aging effect in this eddy. Our data indicate an important role for anticyclonic mode water eddies in stimulating N2 fixation and thus supplying N offshore.

  12. N2 fixation in eddies of the eastern tropical South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Löscher, C. R.; Bourbonnais, A.; Dekaezemacker, J.; Charoenpong, C. N.; Altabet, M. A.; Bange, H. W.; Czeschel, R.; Hoffmann, C.; Schmitz, R. A.

    2015-11-01

    Mesoscale eddies play a major role in controlling ocean biogeochemistry. By impacting nutrient availability and water column ventilation, they are of critical importance for oceanic primary production. In the eastern tropical South Pacific Ocean off Peru, where a large and persistent oxygen deficient zone is present, mesoscale processes have been reported to occur frequently. However, investigations on their biological activity are mostly based on model simulations, and direct measurements of carbon and dinitrogen (N2) fixation are scarce. We examined an open ocean cyclonic eddy and two anticyclonic mode water eddies: a coastal one and an open ocean one in the waters off Peru along a section at 16° S in austral summer 2012. Molecular data and bioassay incubations point towards a difference between the active diazotrophic communities present in the cyclonic eddy and the anticyclonic mode water eddies. In the cyclonic eddy, highest rates of N2 fixation were measured in surface waters but no N2 fixation signal was detected at intermediate water depths. In contrast, both anticyclonic mode water eddies showed pronounced maxima in N2 fixation below the euphotic zone as evidenced by rate measurements and geochemical data. N2 fixation and carbon (C) fixation were higher in the young coastal mode water eddy compared to the older offshore mode water eddy. A co-occurrence between N2 fixation and biogenic N2, an indicator for N loss, indicated a link between N loss and N2 fixation in the mode water eddies, which was not observed for the cyclonic eddy. The comparison of two consecutive surveys of the coastal mode water eddy in November and December 2012 revealed also a reduction of N2 and C fixation at intermediate depths along with a reduction in chlorophyll by half, mirroring an aging effect in this eddy. Our data indicate an important role for anticyclonic mode water eddies in stimulating N2 fixation and thus supplying N offshore.

  13. Significant N2 fixation by heterotrophs, photoheterotrophs and heterocystous cyanobacteria in two temperate estuaries

    PubMed Central

    Bentzon-Tilia, Mikkel; Traving, Sachia J; Mantikci, Mustafa; Knudsen-Leerbeck, Helle; Hansen, Jørgen LS; Markager, Stiig; Riemann, Lasse

    2015-01-01

    Nitrogen (N) fixation is fueling planktonic production in a multitude of aquatic environments. In meso- and poly-haline estuaries, however, the contribution of N by pelagic N2 fixation is believed to be insignificant due to the high input of N from land and the presumed absence of active N2-fixing organisms. Here we report N2 fixation rates, nifH gene composition and nifH gene transcript abundance for key diazotrophic groups over 1 year in two contrasting, temperate, estuarine systems: Roskilde Fjord (RF) and the Great Belt (GB) strait. Annual pelagic N2 fixation rates averaged 17 and 61 mmol N m−2 per year at the two sites, respectively. In RF, N2 fixation was mainly accompanied by transcripts related to heterotrophic (for example, Pseudomonas sp.) and photoheterotrophic bacteria (for example, unicellular diazotrophic cyanobacteria group A). In the GB, the first of two N2 fixation peaks coincided with a similar nifH-expressing community as in RF, whereas the second peak was synchronous with increased nifH expression by an array of diazotrophs, including heterotrophic organisms as well as the heterocystous cyanobacterium Anabaena. Thus, we show for the first time that significant planktonic N2 fixation takes place in mesohaline, temperate estuaries and that the importance of heterotrophic, photoheterotrophic and photosynthetic diazotrophs is clearly variable in space and time. PMID:25026373

  14. Effect of Glyphosate on Symbiotic N2 Fixation and Nickel Concentration in Glyphosate-Resistant Soybean

    USDA-ARS?s Scientific Manuscript database

    The impact of widespread cultivation of glyphosate-resistant (GR) soybean and the use of one herbicide class on biological processes has received considerable attention. Decreased biological nitrogen fixation in GR soybean has been attributed directly to toxicity of glyphosate or its metabolites to ...

  15. Basin-wide N2 fixation in the deep waters of the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Benavides, Mar; Bonnet, Sophie; Hernández, Nauzet; Martínez-Pérez, Alba María.; Nieto-Cid, Mar; Álvarez-Salgado, Xosé Antón; Baños, Isabel; Montero, María. F.; Mazuecos, Ignacio P.; Gasol, Josep M.; Osterholz, Helena; Dittmar, Thorsten; Berman-Frank, Ilana; Arístegui, Javier

    2016-06-01

    Recent findings indicate that N2 fixation is significant in aphotic waters, presumably due to heterotrophic diazotrophs depending on organic matter for their nutrition. However, the relationship between organic matter and heterotrophic N2 fixation remains unknown. Here we explore N2 fixation in the deep chlorophyll maximum and underneath deep waters across the whole Mediterranean Sea and relate it to organic matter composition, characterized by optical and molecular methods. Our N2 fixation rates were in the range of those previously reported for the euphotic zone of the Mediterranean Sea (up to 0.43 nmol N L-1 d-1) and were significantly correlated to the presence of relatively labile organic matter with fluorescence and molecular formula properties representative for peptides and unsaturated aliphatics and associated with the presence of more oxygenated ventilated water masses. Finally, and despite that the aphotic N2 fixation contributes largely to total water column diazotrophic activity (>50%), its contribution to overall nitrogen inputs to the basin is negligible (<0.5%).

  16. Summer surface waters in the Gulf of California: Prime habitat for biological N2 fixation

    NASA Astrophysics Data System (ADS)

    White, Angelicque E.; Prahl, Fredrick G.; Letelier, Ricardo M.; Popp, Brian N.

    2007-06-01

    We report significant rates of dinitrogen (N2) fixation in the central basins of the Gulf of California (GC) during July-August 2005. Mixing model estimates based upon δ15N values of particulate matter in the surface mixed layer indicate that N2 fixation provides as much as 35% to 48% of the phytoplankton-based nitrogen demand in the central Guaymas and Carmen basins. Microscopic analyses identify the responsible genera as the N2-fixing endosymbiont, Richelia intracellularis, with lesser contributions from the large nonheterocystous diazotroph Trichodesmium. Analyses of remotely sensed chlorophyll a and sea surface temperature indicate that primary production levels are elevated in regions of the GC where oceanographic conditions are ideal in summertime for the growth of N2-fixing organisms. These findings suggest that biological N2 fixation must be taken into account when assessing past and present nitrogen dynamics in this environmentally important region.

  17. Bacterial N2-fixation in mangrove ecosystems: insights from a diazotroph-mangrove interaction.

    PubMed

    Alfaro-Espinoza, Gabriela; Ullrich, Matthias S

    2015-01-01

    Mangrove forests are highly productive ecosystems but represent low nutrient environments. Nitrogen availability is one of the main factors limiting mangrove growth. Diazotrophs have been identified as key organisms that provide nitrogen to these environments. N2-fixation by such organisms was found to be higher in the mangrove roots than in surrounding rhizosphere. Moreover, previous studies showed that mangroves grew better in the presence of N2-fixers indicating a potentially mutualistic relationship. However, the molecular signals and mechanisms that govern these interactions are still poorly understood. Here we present novel insights in the interaction of a diazotroph with a mangrove species to improve our understanding of the molecular and ecophysiological relationship between these two organisms under controlled conditions. Our results showed that Marinobacterium mangrovicola is a versatile organism capable of competing with other organisms to survive for long periods in mangrove soils. N2-fixation by this bacterium was up-regulated in the presence of mangrove roots, indicating a possible beneficial interaction. The increase in N2-fixation was limited to cells of the exponential growth phase suggesting that N2-fixation differs over the bacterial growth cycle. Bacterial transformants harboring a transcriptional nifH::gusA fusion showed that M. mangrovicola successfully colonized mangrove roots and simultaneously conducted N2-fixation. The colonization process was stimulated by the lack of an external carbon source suggesting a possible mutualistic relationship. M. mangrovicola represents an interesting genetically accessible diazotroph, which colonize mangrove roots and exhibit higher N2-fixation in the presence of mangrove roots. Consequently, we propose this microorganism as a tool to study molecular interactions between N2-fixers and mangrove plants and to better understand how changes in the environment could impact these important and relatively unknown

  18. Bacterial N2-fixation in mangrove ecosystems: insights from a diazotroph–mangrove interaction

    PubMed Central

    Alfaro-Espinoza, Gabriela; Ullrich, Matthias S.

    2015-01-01

    Mangrove forests are highly productive ecosystems but represent low nutrient environments. Nitrogen availability is one of the main factors limiting mangrove growth. Diazotrophs have been identified as key organisms that provide nitrogen to these environments. N2-fixation by such organisms was found to be higher in the mangrove roots than in surrounding rhizosphere. Moreover, previous studies showed that mangroves grew better in the presence of N2-fixers indicating a potentially mutualistic relationship. However, the molecular signals and mechanisms that govern these interactions are still poorly understood. Here we present novel insights in the interaction of a diazotroph with a mangrove species to improve our understanding of the molecular and ecophysiological relationship between these two organisms under controlled conditions. Our results showed that Marinobacterium mangrovicola is a versatile organism capable of competing with other organisms to survive for long periods in mangrove soils. N2-fixation by this bacterium was up-regulated in the presence of mangrove roots, indicating a possible beneficial interaction. The increase in N2-fixation was limited to cells of the exponential growth phase suggesting that N2-fixation differs over the bacterial growth cycle. Bacterial transformants harboring a transcriptional nifH::gusA fusion showed that M. mangrovicola successfully colonized mangrove roots and simultaneously conducted N2-fixation. The colonization process was stimulated by the lack of an external carbon source suggesting a possible mutualistic relationship. M. mangrovicola represents an interesting genetically accessible diazotroph, which colonize mangrove roots and exhibit higher N2-fixation in the presence of mangrove roots. Consequently, we propose this microorganism as a tool to study molecular interactions between N2-fixers and mangrove plants and to better understand how changes in the environment could impact these important and relatively unknown

  19. Nitrogen Stress and Apparent Photosynthesis in Symbiotically Grown Pisum sativum L. 1

    PubMed Central

    Dejong, Ted M.; Phillips, Donald A.

    1981-01-01

    Pea plants (Pisum sativum L. cv. Alaska) were inoculated individually with one of 15 Rhizobium leguminosarum strains and grown under uniform environmental conditions in the absence of combined N. Differences in effectiveness of the Rhizobium strains produced plants with differing rates of whole plant apparent N2 fixation and total N content at the same morphological stage of development. Plants were analyzed to determine interactions between N2 fixation, N allocation, apparent photosynthesis, and growth. Total leaf N increased linearly with total N2 fixation (R2 = 0.994). The proportion of total N allocated to leaves, the per cent N content of individual leaves, and the photosynthetic efficiency of individual leaves showed a curvilinear response with increasing plant N content. Differences in allocation patterns of leaf N between plants with low and high N content resulted in differences in the relationship between total N content and plant dry weight. Results from this study show that N2 fixation interacts with leaf photosynthetic efficiency and plant growth in a manner that is dependent upon the allocation of symbiotically fixed N. PMID:16661907

  20. Malonate Catabolism Does Not Drive N2 Fixation in Legume Nodules

    PubMed Central

    Karunakaran, Ramakrishnan; East, Alison K.

    2013-01-01

    Malonyl-coenzyme A (CoA) decarboxylase, malonyl-CoA synthetase, and malonate transporter mutants of Rhizobium leguminosarum bv. viciae and trifolii fixed N2 at wild-type rates on pea and clover, respectively. Thus, malonate does not drive N2 fixation in legume nodules. PMID:23666330

  1. Association between aflatoxin contamination and N2 fixation in peanut under drought conditions

    USDA-ARS?s Scientific Manuscript database

    Traits related to nitrogen fixation may be used as indirect selection criteria for aflatoxin resistance in peanut. The aim of this study was to investigate the relationship between N2 fixation traits and aflatoxin contamination in peanut under different drought conditions. Eleven peanut genotypes we...

  2. Malonate catabolism does not drive N2 fixation in legume nodules.

    PubMed

    Karunakaran, Ramakrishnan; East, Alison K; Poole, Philip S

    2013-07-01

    Malonyl-coenzyme A (CoA) decarboxylase, malonyl-CoA synthetase, and malonate transporter mutants of Rhizobium leguminosarum bv. viciae and trifolii fixed N2 at wild-type rates on pea and clover, respectively. Thus, malonate does not drive N2 fixation in legume nodules.

  3. Growth and N2 fixation in an Alnus hirsuta (Turcz.) var. sibirica stand in Japan.

    PubMed

    Tobita, Hiroyuki; Hasegawa, Shigeaki F; Yazaki, Kenichi; Komatsu, Masabumi; Kitao, Mitsutoshi

    2013-11-01

    To estimate the N2 fixation ability of the alder (Alnus hirsuta (Turcz.) var. sibirica), we examined the seasonal variation in nitrogenase activity of nodules using the acetylene reduction method in an 18-year-old stand naturally regenerated after disturbance by road construction in Japan. To evaluate the contribution of N2 fixation to the nitrogen (N) economy in this alder stand, we also measured the phenology of the alder, the litterfall, the decomposition rate of the leaf litter, and N accumulation in the soil. The acetylene reduction activity per unit nodule mass (ARA) under field conditions appeared after bud break, peaked the maximum in midsummer after full expansion of the leaves, and disappeared after all leaves had fallen. There was no consistent correlation between ARA and tree size (dbh). The amount of N2 fixed in this alder stand was estimated at 56.4 kg ha-1 year-1 when a theoretical molar ratio of 3 was used to convert the amount of reduced acetylene to the amount of fixed N2. This amount of N2 fixation corresponded to the 66.4 percent of N in the leaf litter produced in a year. These results suggested that N2 fixation still contributed to the large portion of N economy in this alder stand.

  4. Contribution of mono and polysaccharides to heterotrophic N2 fixation at the eastern Mediterranean coastline.

    PubMed

    Rahav, E; Giannetto, M J; Bar-Zeev, E

    2016-06-16

    N2 fixation should be a critical process in the nitrogen-poor surface water of the eastern Mediterranean Sea. Despite favorable conditions, diazotroph abundance and N2 fixation rates remains low for reasons yet explained. The main goal of this study was to investigate the limiting nutrients for diazotrophy in this oligotrophic environment. Hence, we conducted dedicated bottle-microcosms with eastern Mediterranean Sea water that were supplemented with mono and polysaccharides as well as inorganic nitrogen and phosphorous. Our results indicate that the diazotrophic community expressing nifH was primarily represented by heterotrophic Proteobacteria. N2 fixation and heterotrophic bacterial activity increased up-to tenfold following two days of dark incubations, once seawater was supplemented with organic carbon substrate in the form of glucose (monosaccharides) or gum-xanthan (polysaccharide surrogate). Furthermore, our results point that carbon-rich polysaccharides, such as transparent exopolymer particles, enhance heterotrophic N2 fixation, by forming microenvironments of intense metabolic activity, high carbon: nitrogen ratio, and possibly low O2 levels. The conclusions of this study indicate that diazotrophs in the eastern Mediterranean coast are primarily limited by organic carbon substrates, as possibly in many other marine regions.

  5. Contribution of mono and polysaccharides to heterotrophic N2 fixation at the eastern Mediterranean coastline

    PubMed Central

    Rahav, E.; Giannetto, M. J.; Bar-Zeev, E.

    2016-01-01

    N2 fixation should be a critical process in the nitrogen-poor surface water of the eastern Mediterranean Sea. Despite favorable conditions, diazotroph abundance and N2 fixation rates remains low for reasons yet explained. The main goal of this study was to investigate the limiting nutrients for diazotrophy in this oligotrophic environment. Hence, we conducted dedicated bottle-microcosms with eastern Mediterranean Sea water that were supplemented with mono and polysaccharides as well as inorganic nitrogen and phosphorous. Our results indicate that the diazotrophic community expressing nifH was primarily represented by heterotrophic Proteobacteria. N2 fixation and heterotrophic bacterial activity increased up-to tenfold following two days of dark incubations, once seawater was supplemented with organic carbon substrate in the form of glucose (monosaccharides) or gum-xanthan (polysaccharide surrogate). Furthermore, our results point that carbon-rich polysaccharides, such as transparent exopolymer particles, enhance heterotrophic N2 fixation, by forming microenvironments of intense metabolic activity, high carbon: nitrogen ratio, and possibly low O2 levels. The conclusions of this study indicate that diazotrophs in the eastern Mediterranean coast are primarily limited by organic carbon substrates, as possibly in many other marine regions. PMID:27306501

  6. Aphotic N2 Fixation in the Eastern Tropical South Pacific Ocean

    PubMed Central

    Bonnet, Sophie; Dekaezemacker, Julien; Turk-Kubo, Kendra A.; Moutin, Thierry; Hamersley, Robert M.; Grosso, Olivier; Zehr, Jonathan P.; Capone, Douglas G.

    2013-01-01

    We examined rates of N2 fixation from the surface to 2000 m depth in the Eastern Tropical South Pacific (ETSP) during El Niño (2010) and La Niña (2011). Replicated vertical profiles performed under oxygen-free conditions show that N2 fixation takes place both in euphotic and aphotic waters, with rates reaching 155 to 509 µmol N m−2 d−1 in 2010 and 24±14 to 118±87 µmol N m−2 d−1 in 2011. In the aphotic layers, volumetric N2 fixation rates were relatively low (<1.00 nmol N L−1 d−1), but when integrated over the whole aphotic layer, they accounted for 87–90% of total rates (euphotic+aphotic) for the two cruises. Phylogenetic studies performed in microcosms experiments confirm the presence of diazotrophs in the deep waters of the Oxygen Minimum Zone (OMZ), which were comprised of non-cyanobacterial diazotrophs affiliated with nifH clusters 1K (predominantly comprised of α-proteobacteria), 1G (predominantly comprised of γ-proteobacteria), and 3 (sulfate reducing genera of the δ-proteobacteria and Clostridium spp., Vibrio spp.). Organic and inorganic nutrient addition bioassays revealed that amino acids significantly stimulated N2 fixation in the core of the OMZ at all stations tested and as did simple carbohydrates at stations located nearest the coast of Peru/Chile. The episodic supply of these substrates from upper layers are hypothesized to explain the observed variability of N2 fixation in the ETSP. PMID:24349048

  7. Effects of elevated carbon dioxide concentration on growth and N2 fixation of young Robinia pseudoacacia.

    PubMed

    Feng, Z; Dyckmans, J; Flessa, H

    2004-03-01

    Effects of elevated CO2 concentration ([CO2]) on carbon (C) and nitrogen (N) uptake and N source partitioning (N2 fixation versus mineral soil N uptake) of 1-year-old Robinia pseudoacacia were determined in a dual 13C and 15N continuous labeling experiment. Seedlings were grown for 16 weeks in ambient (350 ppm) or elevated [CO2] (700 ppm) with 15NH4 15NO3 as the only mineral nitrogen source. Elevated [CO2] increased the fraction of new C in total C, but it did not alter C partitioning among plant compartments. Elevated [CO2] also increased the fraction of new N in total N and this was coupled with a shift in N source partitioning toward N2 fixation. Soil N uptake was unaffected by elevated [CO2], whereas N2 fixation was markedly increased by the elevated [CO2] treatment, mainly because of increased specific fixation (mg N mg(-1) nodule). As a result of increased N2 fixation, the C/N ratio of tree biomass tended to decrease in the elevated [CO2] treatment. Partitioning of N uptake among plant compartments was unaffected by elevated [CO2]. Total dry mass of root nodules doubled in response to elevated [CO2], but this effect was not significant because of the great variability of root nodule formation. Our results show that, in the N2-fixing R. pseudoacacia, increased C uptake in response to increased [CO2] is matched by increased N2 fixation, indicating that enhanced growth in elevated [CO2] might not be restricted by N limitations.

  8. Nitrogen fixation in boreal peatlands: the effects of increased N deposition on N2-fixation

    NASA Astrophysics Data System (ADS)

    Popma, J. M.; Wieder, R.; Lamers, L.; Vile, M. A.

    2013-12-01

    Boreal peatlands are of great importance to global carbon and nitrogen cycling. While covering only 3-4 % of the terrestrial surface, they account for 25-30 % of the world's soil C and 9-15 % of the world's soil N. In Western Canada atmospheric dry deposition rates are extremely low: approximately 1 kg N ha-1 yr-1. Though these systems have been functioning as net sinks over the past 11,000 years, natural and anthropogenic disturbances might compromise the historical balance of C and N. Biological N2-fixation has recently been shown to represent a very significant input of N into these systems, contributing to 62% of total N in Western Canada. Interactions between N deposition and biological N2-fixation are as yet, unknown, but the impact of elevated deposition of N-compounds from increased industrial expansion of oil sands mining to peatlands, is concerning. Given that nitrogenase, the enzyme responsible for catalyzing N2-fixation, is energetically costly when active, enhanced inputs of atmospheric N deposition could be a major determinant for enzyme activity and rates of biological N input to these bogs. Understanding interactions between N deposition and N2 fixation in boreal peatlands can aid in predicting the consequences of increased N deposition and setting critical loads. We conducted a field-fertilization experiment in a poor fen in Alberta, Canada, to determine the effects of enhanced N deposition on a dominant fen species Sphagnum angustifolium. The experiment consisted of seven N treatments: Control, 0, 5, 10, 15, 20 and 25 kg N ha-1 y1, n=3. N2-fixation was measured during summer 2012 and 2013 using the acetylene reduction assay (ARA). ARA rates were converted to rates of N2-fixation by calibrating ARA with paired 15N2-incubations. In both 2012 and 2013, with increasing N deposition from 0 kg N ha-1 yr-1 to 25 kg N ha-1 yr-1, rates of N2 fixation decreased, with highest rates in the 0 kg N ha-1 yr-1 treatment mosses (54.2 × 1.40; 48.58 × 7.12 kg N ha

  9. Nutrient control of N2 fixation in the oligotrophic Mediterranean Sea and the impact of Saharan dust events

    NASA Astrophysics Data System (ADS)

    Ridame, C.; Le Moal, M.; Guieu, C.; Ternon, E.; Biegala, I. C.; L'Helguen, S.; Pujo-Pay, M.

    2011-03-01

    A better understanding of the factors controlling N2 fixation is a pre-requisite for improving our knowledge on the contribution of N2 fixation in the nitrogen cycling in the Mediterranean Sea. Trace-metal clean nutrient/dust additions bioassays (+P, +PFe, +dust) were performed at three stations located in the western, central and eastern Mediterranean Sea, in summer 2008 as part of the BOUM cruise. The main goals were to investigate the nutrient factor(s) limiting N2 fixation (uptake of 15N2) and to evaluate the potential impact of a Saharan dust event on this biological process during the stratification period. Initially, surface waters at the three stations were DIP-depleted (<10 nM) while the DFe concentrations were relatively high (from 1.2 to 2.3 nM) most likely due to atmospheric iron accumulation in the surface mixed layer. At all stations, Saharan dust input relieved the ambient nutrient limitation of diazotrophic activity as demonstrated by the strong stimulation of N2 fixation (from x2.3 to x5.3). The highest dust stimulation of N2 fixation was recorded at the station located in the eastern basin (x5.3). The responses of diazotrophic activity to nutrients addition were contrasted at the sampled stations suggesting a spatial variability of the factor controlling N2 fixation over the whole basin. At all stations, N2 fixation was not limited by Fe nor co-limited by P and Fe. At the western station, N2 fixation was DIP limited while at the eastern one, N2 fixation was first DIP limited then was limited by one or several chemical element(s) released by dust. Our results demonstrated that a Saharan dust input was able to relieve the successive on-going N2 fixation limitations. Very interestingly, at the station located in the central basin, N2 fixation was not limited by the availability of P yet it was strongly stimulated by dust additions (up to x3.1). A chemical element or a combination of several, released by the added dust may have been responsible for

  10. Determination of total N 2 fixation rates in the ocean taking into account both the particulate and filtrate fractions

    NASA Astrophysics Data System (ADS)

    Konno, U.; Tsunogai, U.; Komatsu, D. D.; Daita, S.; Nakagawa, F.; Tsuda, A.; Matsui, T.; Eum, Y.-J.; Suzuki, K.

    2010-08-01

    Using the 15N2 tracer method and high-sensitivity δ15N analytical systems, we determined N2 fixation rates for ocean samples by dividing them into particulate (>0.7 μm) and filtrate (<0.7 μm) fractions. While N2 fixation in the filtrate fraction had been ignored in previous studies, we found a significant N2 fixation rates in the filtrate fraction in our study. The areal N2 fixation rates in the western North Pacific Ocean estimated from the particulate fraction varied from <1 to 160 μmol N m-2 d-1, and those rates estimated from the filtrate fraction ranged from <0.5 to 54 μmol N m-2 d-1. Thus, N2 fixation in the filtrate fraction accounts for on average 50% (ranging from <10% to 84%) of the total N2 fixation rates. If these results are confirmed generally in the ocean, the new total N2 fixation flux, which includes fixation in the filtrate fraction, possibly doubles the original estimates; therefore, the revised influx may reduce the imbalance in the global oceanic fixed nitrogen budget.

  11. Diazotrophy in the Deep: Measuring Rates and Identifying Biological Mediators of N2 fixation in Deep-Sea Sediments

    NASA Astrophysics Data System (ADS)

    Dekas, A. E.; Fike, D. A.; Chadwick, G.; Connon, S. A.; Orphan, V. J.

    2013-12-01

    Biological N2 fixation (the conversion of N2 to NH3) is the largest natural source of bioavailable nitrogen to the biosphere, and dictates the rate of community productivity in many nitrogen-limited environments. Deep-sea sediments are traditionally not thought to host N2 fixation, however evidence from a metagenomics dataset targeting deep-sea methanotrophic archaea (ANME) suggested their ability to fix N2 (Pernthaler, et al., PNAS 2008). Using stable isotope labeling experiments and FISH-NanoSIMS, a technique which allows the visualization of isotopic composition within phylogenetically identified cells on the nanometer scale, we demonstrated that the ANME are capable of N2 fixation (Dekas et al., Science 2009). In the present work, we use FISH-NanoSIMS and bulk Isotope Ratio Mass Spectrometry (IRMS) to show that the ANME are the most significant source of new nitrogen at a Costa Rican methane seep. This suggests that the ANME may play a significant role in N2 fixation in methane seeps worldwide. We expand our investigation of deep-sea diazotrophy to include diverse habitats, including sulfide- and carbon-rich whalefalls, and observe that N2 fixation is widespread in sediments on the seafloor. Outside of methane seeps, N2 fixation appears to be mediated by a diversity of anaerobic microbes potentially including methanogens and sulfate reducing bacteria. Interestingly, deep-sea N2 fixation often occurs in the presence of high levels of NH4+. Our observations challenge long-held hypotheses about where and when N2 fixation occurs, and suggest a bigger role for N2 fixation on the seafloor - and potentially the deep-biosphere - than previously realized.

  12. Nutrient control of N2 fixation in the oligotrophic Mediterranean Sea and the impact of Saharan dust events

    NASA Astrophysics Data System (ADS)

    Ridame, C.; Le Moal, M.; Guieu, C.; Ternon, E.; Biegala, I. C.; L'Helguen, S.; Pujo-Pay, M.

    2011-09-01

    A better understanding of the factors controlling N2 fixation is a pre-requisite for improving our knowledge on the contribution of N2 fixation process in the nitrogen cycling. Trace-metal clean nutrient/dust addition bioassays (+P, +PFe, +dust) were performed at three stations located in the western, central and eastern Mediterranean Sea, in summer 2008 as part of the BOUM cruise. The main goals were (1) to investigate the nutrient factor(s) limiting N2 fixation (uptake of 15N2) and (2) to evaluate the potential impact of a Saharan dust event on this biological process during the stratification period. Initially, surface waters at the three stations were DIP-depleted (<10 nM) while the DFe concentrations were relatively high (from 1.2 to 2.3 nM) most likely due to atmospheric iron accumulation in the surface mixed layer. At all stations, Saharan dust input relieved the ambient nutrient limitation of the diazotrophic activity as demonstrated by the strong stimulation of N2 fixation (from 130 % to 430 %). The highest dust stimulation of N2 fixation was recorded at the station located in the eastern basin. The response of diazotrophic activity to nutrient additions was variable between the sampled stations suggesting a spatial variability of the factor controlling N2 fixation over the whole basin. At all stations, N2 fixation was not limited by Fe nor co-limited by P and Fe. At the western station, N2 fixation was DIP limited while at the eastern one, N2 fixation was first DIP limited, then was limited by one or several chemical element(s) released by dust. Our results demonstrated that a Saharan dust input was able to relieve these successive on going limitations. Very interestingly, at the station located in the central basin, N2 fixation was not limited by the availability of P yet it was strongly stimulated by dust addition (x3.1). A chemical element or a combination of several, released by the added dust may have been responsible for the observed stimulations of

  13. N2 fixation in marine heterotrophic bacteria: dynamics of environmental and molecular regulation.

    PubMed

    Coyer, J A; Cabello-Pasini, A; Swift, H; Alberte, R S

    1996-04-16

    Molecular and immunological techniques were used to examine N2 fixation in a ubiquitous heterotrophic marine bacterium, the facultative anaerobic Vibrio natriegens. When batch cultures were shifted from aerobic N-replete to anaerobic N-deplete conditions, transcriptional and post-translational regulation of N2 fixation was observed. Levels of nifHDK mRNA encoding the nitrogenase enzyme were highest at 140 min postshift and undetectable between 6 and 9 h later. Immunologically determined levels of nitrogenase enzyme (Fe protein) were highest between 6 and 15 h postshift, and nitrogenase activity peaked between 6 and 9 h postshift, declining by a factor of 2 after 12-15 h. Unlike their regulation in cyanobacteria, Fe protein and nitrogenase activity were present when nifHDK mRNA was absent in V. natriegens, indicating that nitrogenase is stored and stable under anaerobic conditions. Both nifHDK mRNA and Fe protein disappeared within 40 min after cultures were shifted from N2-fixing conditions (anaerobic, N-deplete) to non- N2-fixing conditions (aerobic, N-enriched) but reappeared when shifted to conditions favoring N2 fixation. Thus, unlike other N2-fixing heterotrophic bacteria, nitrogenase must be resynthesized after aerobic exposure in V. natriegens. Immunological detection based on immunoblot (Western) analysis and immunogold labeling correlated positively with nitrogenase activity; no localization of nitrogenase was observed. Because V. natriegens continues to fix N2 for many hours after anaerobic induction, this species may play an important role in providing "new" nitrogen in marine ecosystems.

  14. Constraining the origin and prevalence of biological N2 fixation in the Precambrian

    NASA Astrophysics Data System (ADS)

    Stüeken, Eva; Buick, Roger; Guy, Bradley; Koehler, Matthew

    2015-04-01

    Nitrogen is an essential nutrient for all life on Earth; however, atmospheric N2, the largest nitrogen reservoir at the Earth's surface, is chemically inert and only accessible to some prokaryotic microbes that possess a nitrogenase enzyme. Prior to the origin of this metabolism, bioavailable nitrogen may have been derived from hydrothermal activity, lightning or photochemical reactions, but these sources are minor today and probably became limiting with the expansion of the biosphere. The origin of biological N2 fixation was therefore of paramount importance for early evolution. Geochemical and phylogenetic data, however, suggest that this event may have been delayed until the early Proterozoic, possibly by the lack of dissolved Mo, an essential co-factor in nitrogenase. Here we show new nitrogen isotopic data from low-grade sedimentary rocks of the Soanesville Group (~3.2 Ga, Western Australia), the Witwatersrand Supergroup (~2.9 Ga, South Africa), and the lower Fortescue Group (~2.75 Ga, Western Australia), with a total mean of 0.0 ± 1.2 ‰ relative to atmospheric N2. These values are inconsistent with abiotic sources of fixed nitrogen and difficult to reconcile with alternative nitrogenase enzymes that do not depend on Mo. Instead it is most likely that Mo-based nitrogenase had already evolved and was widespread in the mid-Archean. Combined with a literature database of δ15N values through time, our results suggest that other forms of fixed nitrogen became available in the late Archean and persisted throughout the Paleoproterozoic. In the Mesoproterozoic ocean, fixed nitrogen was likely restricted to shallow waters, while offshore environments were dominated by Mo-based N2 fixation. This basinal gradient likely disappeared in the Neoproterozoic. In conclusion, biological N2 fixation is a much more ancient metabolism than previously proposed and Mo has been bioavailable in at least small amounts throughout the Precambrian.

  15. N2 fixation in marine heterotrophic bacteria: dynamics of environmental and molecular regulation.

    PubMed Central

    Coyer, J A; Cabello-Pasini, A; Swift, H; Alberte, R S

    1996-01-01

    Molecular and immunological techniques were used to examine N2 fixation in a ubiquitous heterotrophic marine bacterium, the facultative anaerobic Vibrio natriegens. When batch cultures were shifted from aerobic N-replete to anaerobic N-deplete conditions, transcriptional and post-translational regulation of N2 fixation was observed. Levels of nifHDK mRNA encoding the nitrogenase enzyme were highest at 140 min postshift and undetectable between 6 and 9 h later. Immunologically determined levels of nitrogenase enzyme (Fe protein) were highest between 6 and 15 h postshift, and nitrogenase activity peaked between 6 and 9 h postshift, declining by a factor of 2 after 12-15 h. Unlike their regulation in cyanobacteria, Fe protein and nitrogenase activity were present when nifHDK mRNA was absent in V. natriegens, indicating that nitrogenase is stored and stable under anaerobic conditions. Both nifHDK mRNA and Fe protein disappeared within 40 min after cultures were shifted from N2-fixing conditions (anaerobic, N-deplete) to non- N2-fixing conditions (aerobic, N-enriched) but reappeared when shifted to conditions favoring N2 fixation. Thus, unlike other N2-fixing heterotrophic bacteria, nitrogenase must be resynthesized after aerobic exposure in V. natriegens. Immunological detection based on immunoblot (Western) analysis and immunogold labeling correlated positively with nitrogenase activity; no localization of nitrogenase was observed. Because V. natriegens continues to fix N2 for many hours after anaerobic induction, this species may play an important role in providing "new" nitrogen in marine ecosystems. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:11607653

  16. N2-fixation dynamics during ecosystem recovery in longleaf pine savannas

    NASA Astrophysics Data System (ADS)

    Tierney, J. A.

    2016-12-01

    Biological nitrogen fixation (BNF) can alleviate nitrogen (N) deficiencies that inhibit ecosystem recovery. BNF may be particularly important in ecosystems recovering from land-use change and perturbations from fire, as these disturbances can exacerbate N limitation. Here, we investigated how BNF dynamics change throughout ecosystem development in restored longleaf pine savannas, and how BNF responds to fire. We conducted this study in 59 1-ha plots of longleaf pine distributed across gradients of stand age and fire frequency at two sites in the southeastern US. We determined BNF contributions by three functional groups of N2-fixers (herbaceous legumes, biological soil crusts, and asymbiotic N2-fixing bacteria) by quantifying their abundances, assessing nitrogenase activity, and scaling these estimates up to the plot-level. To determine aboveground N demands, we measured tree growth using diameter increments and allometric equations paired with tissue-specific N concentrations. We fit linear models to evaluate the effects of stand age and time since fire on BNF and N demands throughout stand development, and performed separate analyses on mature stands to determine how fire return interval affects BNF. We observed distinct temporal patterns of N2-fixation across stand development among the three groups of N2 fixers. N2-fixation by legumes and asymbiotic bacteria remained low until stands reached maturity, while N2-fixation by biological soil crusts (BSCs) was high in juvenile stands and decreased with stand age. These patterns suggest a compensatory shift in the importance of these functional groups throughout stand development such that contributions from BSCs are critical for meeting N demands when disturbances may hinder the establishment of legumes and asymbiotic bacteria. N2-fixation by BSCs and asymbiotic bacteria throughout stand development was not affected by time since fire, but legume abundance increased the year following fire, suggesting a recovery

  17. New estimation of N2 fixation in the western and central Pacific Ocean and its marginal seas

    NASA Astrophysics Data System (ADS)

    Shiozaki, Takuhei; Furuya, Ken; Kodama, Taketoshi; Kitajima, Satoshi; Takeda, Shigenobu; Takemura, Toshihiko; Kanda, Jota

    2010-03-01

    The distribution of N2 fixation was examined using a 15N2 tracer with accompanying measurements of abundance of Trichodesmium spp. and Richelia intracellularis, nitrate plus nitrite (N+N) and soluble reactive phosphorus at the nanomolar level, and primary production in the western and central Pacific Ocean. N2 fixation occurred only in >˜20°C oligotrophic (i.e., N+N < 100 nM) waters except at a station in the equatorial upwelling zone where N+N was 1880 nM. High N2 fixation rates were observed in the Kuroshio and East China Sea (KECS) and near Fiji and other isolated islands with concomitant high abundance of Trichodesmium spp. In contrast, N2 fixation in the western and central oligotrophic North Pacific (WCONP) was significantly lower, and Trichodesmium spp. were rarely observed. These observations hint that KECS and waters around isolated islands are N2 fixation "hot spots" because of the occurrence of Trichodesmium spp. The average N2 fixation rate in the KECS of 232 ± 54.8 (±SE, n = 13) μmol N m-2 d-1 was almost 1 order of magnitude higher than that in the WCONP of 39.2 ± 7.51 (n = 26) μmol N m-2 d-1. On the basis of these estimates and reported values obtained using 15N2, depth-integrated N2 fixation in the North Pacific was estimated to be 2.6 ± 0.3 × 109 (n = 63) mol N d-1, which is less than half of previous estimates. This difference was ascribed primarily to the unavailability of N2 fixation rates in the WCONP, which occupies a vast area of the subtropical North Pacific, and the use of data obtained in the hot spots which represent small areas that likely led to the previous overestimation.

  18. Nitrate isotopic composition between Bermuda and Puerto Rico: Implications for N2 fixation in the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Knapp, Angela N.; Difiore, Peter J.; Deutsch, Curtis; Sigman, Daniel M.; Lipschultz, Fredric

    2008-09-01

    N and O isotope analyses of water column nitrate between Bermuda and Puerto Rico document a bolus of low-δ15N nitrate throughout the Sargasso Sea thermocline, which we attribute primarily to the input of recently fixed N. Although previous work suggests southward increases in N2 fixation and ventilation age, no meridional trend in nitrate δ15N is apparent. In the upper 200 m, the algal uptake-driven increase in nitrate δ18O is greater than in δ15N, because of (1) a higher fraction of nitrate from N2 fixation at shallower depths and/or (2) cycling of N between nitrate assimilation and nitrification. A mean depth profile of newly fixed nitrate estimated from the nitrate isotope data is compared with results from an ocean circulation model forced with different Atlantic fields of N2 fixation. The nitrate from N2 fixation is communicated between the model's North and South Atlantic and suggests a whole Atlantic N2 fixation rate between 15 and 24 Tg N a-1. One important caveat is that fixed N in atmospheric deposition may contribute a significant proportion of the low-δ15N N in the Sargasso Sea thermocline, in which case the relatively low rate we estimate for N2 fixation would still be too high.

  19. Oxygen-poor microzones as potential sites of microbial n(2) fixation in nitrogen-depleted aerobic marine waters.

    PubMed

    Paerl, H W; Prufert, L E

    1987-05-01

    The nitrogen-deficient coastal waters of North Carolina contain suspended bacteria potentially able to fix N(2). Bioassays aimed at identifying environmental factors controlling the development and proliferation of N(2) fixation showed that dissolved organic carbon (as simple sugars and sugar alcohols) and particulate organic carbon (derived from Spartina alterniflora) additions elicited and enhanced N(2) fixation (nitrogenase activity) in these waters. Nitrogenase activity occurred in samples containing flocculent, mucilage-covered bacterial aggregates. Cyanobacterium-bacterium aggregates also revealed N(2) fixation. In all cases bacterial N(2) fixation occurred in association with surficial microenvironments or microzones. Since nitrogenase is oxygen labile, we hypothesized that the aggregates themselves protected their constituent microbes from O(2). Microelectrode O(2) profiles revealed that aggregates had lower internal O(2) tensions than surrounding waters. Tetrazolium salt (2,3,5-triphenyl-3-tetrazolium chloride) reduction revealed that patchy zones existed both within microbes and extracellularly in the mucilage surrounding microbes where free O(2) was excluded. Triphenyltetrazolium chloride reduction also strongly inhibited nitrogenase activity. These findings suggest that N(2) fixation is mediated by the availability of the appropriate types of reduced microzones. Organic carbon enrichment appears to serve as an energy and structural source for aggregate formation, both of which were required for eliciting N(2) fixation responses of these waters.

  20. Oxygen-Poor Microzones as Potential Sites of Microbial N2 Fixation in Nitrogen-Depleted Aerobic Marine Waters

    PubMed Central

    Paerl, Hans W.; Prufert, Leslie E.

    1987-01-01

    The nitrogen-deficient coastal waters of North Carolina contain suspended bacteria potentially able to fix N2. Bioassays aimed at identifying environmental factors controlling the development and proliferation of N2 fixation showed that dissolved organic carbon (as simple sugars and sugar alcohols) and particulate organic carbon (derived from Spartina alterniflora) additions elicited and enhanced N2 fixation (nitrogenase activity) in these waters. Nitrogenase activity occurred in samples containing flocculent, mucilage-covered bacterial aggregates. Cyanobacterium-bacterium aggregates also revealed N2 fixation. In all cases bacterial N2 fixation occurred in association with surficial microenvironments or microzones. Since nitrogenase is oxygen labile, we hypothesized that the aggregates themselves protected their constituent microbes from O2. Microelectrode O2 profiles revealed that aggregates had lower internal O2 tensions than surrounding waters. Tetrazolium salt (2,3,5-triphenyl-3-tetrazolium chloride) reduction revealed that patchy zones existed both within microbes and extracellularly in the mucilage surrounding microbes where free O2 was excluded. Triphenyltetrazolium chloride reduction also strongly inhibited nitrogenase activity. These findings suggest that N2 fixation is mediated by the availability of the appropriate types of reduced microzones. Organic carbon enrichment appears to serve as an energy and structural source for aggregate formation, both of which were required for eliciting N2 fixation responses of these waters. Images PMID:16347337

  1. The importance of nodule CO2 fixation for the efficiency of symbiotic nitrogen fixation in pea at vegetative growth and during pod formation.

    PubMed

    Fischinger, Stephanie Anastasia; Schulze, Joachim

    2010-05-01

    Nodule CO2 fixation is of pivotal importance for N2 fixation. The process provides malate for bacteroids and oxaloacetate for nitrogen assimilation. The hypothesis of the present paper was that grain legume nodules would adapt to higher plant N demand and more restricted carbon availability at pod formation through increased nodule CO2 fixation and a more efficient N2 fixation. Growth, N2 fixation, and nodule composition during vegetative growth and at pod formation were studied in pea plants (Pisum sativum L.). In parallel experiments, 15N2 and 13CO2 uptake, as well as nodule hydrogen and CO2 release, was measured. Plants at pod formation showed higher growth rates and N2 fixation per plant when compared with vegetative growth. The specific activity of active nodules was about 25% higher at pod formation. The higher nodule activity was accompanied by higher amino acid concentration in nodules and xylem sap with a higher share of asparagine. Nodule 13CO2 fixation was increased at pod formation, both per plant and per 15N2 fixed unit. However, malate concentration in nodules was only 40% of that during vegetative growth and succinate was no longer detectable. The data indicate that increased N2 fixation at pod formation is connected with strongly increased nodule CO2 fixation. While the sugar concentration in nodules at pod formation was not altered, the concentration of organic acids, namely malate and succinate, was significantly lower. It is concluded that strategies to improve the capability of nodules to fix CO2 and form organic acids might prolong intensive N2 fixation into the later stages of pod formation and pod filling in grain legumes.

  2. The importance of nodule CO2 fixation for the efficiency of symbiotic nitrogen fixation in pea at vegetative growth and during pod formation

    PubMed Central

    Fischinger, Stephanie Anastasia; Schulze, Joachim

    2010-01-01

    Nodule CO2 fixation is of pivotal importance for N2 fixation. The process provides malate for bacteroids and oxaloacetate for nitrogen assimilation. The hypothesis of the present paper was that grain legume nodules would adapt to higher plant N demand and more restricted carbon availability at pod formation through increased nodule CO2 fixation and a more efficient N2 fixation. Growth, N2 fixation, and nodule composition during vegetative growth and at pod formation were studied in pea plants (Pisum sativum L.). In parallel experiments, 15N2 and 13CO2 uptake, as well as nodule hydrogen and CO2 release, was measured. Plants at pod formation showed higher growth rates and N2 fixation per plant when compared with vegetative growth. The specific activity of active nodules was about 25% higher at pod formation. The higher nodule activity was accompanied by higher amino acid concentration in nodules and xylem sap with a higher share of asparagine. Nodule 13CO2 fixation was increased at pod formation, both per plant and per 15N2 fixed unit. However, malate concentration in nodules was only 40% of that during vegetative growth and succinate was no longer detectable. The data indicate that increased N2 fixation at pod formation is connected with strongly increased nodule CO2 fixation. While the sugar concentration in nodules at pod formation was not altered, the concentration of organic acids, namely malate and succinate, was significantly lower. It is concluded that strategies to improve the capability of nodules to fix CO2 and form organic acids might prolong intensive N2 fixation into the later stages of pod formation and pod filling in grain legumes. PMID:20363863

  3. Co-occurrence of methanogenesis and N2 fixation in oil sands tailings.

    PubMed

    Collins, C E Victoria; Foght, Julia M; Siddique, Tariq

    2016-09-15

    Oil sands tailings ponds in northern Alberta, Canada have been producing biogenic gases via microbial metabolism of hydrocarbons for decades. Persistent methanogenic activity in tailings ponds without any known replenishment of nutrients such as fixed nitrogen (N) persuaded us to investigate whether N2 fixation or polyacrylamide (PAM; used as a tailings flocculant) could serve as N sources. Cultures comprising mature fine tailings (MFT) plus methanogenic medium supplemented with or deficient in fixed N were incubated under an N2 headspace. Some cultures were further amended with citrate, which is used in oil sands processing, as a relevant carbon source, and/or with PAM. After an initial delay, N-deficient cultures with or without PAM produced methane (CH4) at the same rate as N-containing cultures, indicating a mechanism of overcoming apparent N-deficiency. Acetylene reduction and (15)N2 incorporation in all N-deficient cultures (with or without PAM) suggested active N2 fixation concurrently with methanogenesis but inability to use PAM as a N source. 16S rRNA gene pyrosequencing revealed little difference between archaeal populations regardless of N content. However, bacterial sequences in N-deficient cultures showed enrichment of Hyphomicrobiaceae and Clostridium members that might contain N2-fixing species. The results are important in understanding long-term production of biogenic greenhouse gases in oil sands tailings. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Contribution of airborne microbes to bacterial production and N2 fixation in seawater upon aerosol deposition

    NASA Astrophysics Data System (ADS)

    Rahav, Eyal; Ovadia, Galit; Paytan, Adina; Herut, Barak

    2016-01-01

    Aerosol deposition may supply a high diversity of airborne microbes, which can affect surface microbial composition and biological production. This study reports a diverse microbial community associated with dust and other aerosol particles, which differed significantly according to their geographical air mass origin. Microcosm bioassay experiments, in which aerosols were added to sterile (0.2 µm filtered and autoclaved) SE Mediterranean Sea (SEMS) water, were performed to assess the potential impact of airborne bacteria on bacterial abundance, production, and N2 fixation. Significant increase was observed in all parameters within a few hours, and calculations suggest that airborne microbes can account for one third in bacterial abundance and 50-100% in bacterial production and N2-fixation rates following dust/aerosol amendments in the surface SEMS. We show that dust/aerosol deposition can be a potential source of a wide array of microorganisms, which may impact microbial composition and food web dynamics in oligotrophic marine systems such as the SEMS.

  5. Stress-Induced Declines in Soybean N2 Fixation Are Related to Nodule Sucrose Synthase Activity.

    PubMed Central

    Gordon, A. J.; Minchin, F. R.; Skot, L.; James, C. L.

    1997-01-01

    Soybean (Glycine max L.) plants were subjected to a number of treatments (drought, 10 mM nitrate, 150 mM NaCl, shoot meristem removal, and removal of approximately 50% of the nodules) to test the hypothesis that metabolic responses contribute to the regulation of N2 fixation. Nitrogenase activity was correlated with the activity of nodule sucrose synthase (SS), but not with that of glutamine oxoglutarate amino transferase. Leghemoglobin levels and other enzyme activities were not significantly or consistently affected by the treatments. SS mRNA was greatly reduced in nodules of drought-, salt-, and nitrate-treated plants; however, this was not correlated with changes in soluble carbohydrate, starch, amino acids, or ureides. Leghemoglobin mRNA was only slightly affected by the treatments. The time course of drought stress showed a decline in the SS transcript level by 1 d, but levels of leghemoglobin, glutamine synthetase, and ascorbate peroxidase mRNA were not markedly affected by 4 d. SS activity at 4 d was reduced by 46%. We propose that N2 fixation in soybean nodules is mediated by both the oxygen-diffusion barrier and the potential to metabolize sucrose via SS. The response to environmental perturbation may involve down-regulation of the nodule SS gene. PMID:12223754

  6. N2-fixation and seedling growth promotion of lodgepole pine by endophytic Paenibacillus polymyxa.

    PubMed

    Anand, Richa; Grayston, Susan; Chanway, Christopher

    2013-08-01

    We inoculated lodgepole pine (Pinus contorta var. latifolia (Dougl.) Engelm.) with Paenibacillus polymyxa P2b-2R, a diazotrophic bacterium previously isolated from internal stem tissue of a naturally regenerating pine seedling to evaluate biological nitrogen fixation and seedling growth promotion by this microorganism. Seedlings generated from pine seed inoculated with strain P2b-2R were grown for up to 13 months in a N-limited soil mix containing 0.7 mM available N labeled as Ca((15)NO3)2 to facilitate detection of N2-fixation. Strain P2b-2R developed a persistent endophytic population comprising 10(2)-10(6) cfu g(-1) plant tissue inside pine roots, stems, and needles during the experiment. At the end of the growth period, P2b-2R had reduced seedling mortality by 14 % and (15)N foliar N abundance 79 % and doubled foliar N concentration and seedling biomass compared to controls. Our results suggest that N2-fixation by P. polymyxa enhanced growth of pine seedlings and support the hypothesis that plant-associated diazotrophs capable of endophytic colonization can satisfy a significant proportion of the N required by tree seedlings growing under N-limited conditions.

  7. Will rising CO2 influence how nutrients interact to control tropical N2-fixation?

    NASA Astrophysics Data System (ADS)

    Trierweiler, A.; Winter, K.; Wright, S. J.; Wurzburger, N.; Hedin, L.

    2013-12-01

    The response of terrestrial tropical carbon sinks to increasing CO2 is a pressing question in biogeochemistry. Limitation of nutrients such as N may constrain these sinks. Biological N2-fixation, an important biogeochemical process that provides new nitrogen to ecosystems, potentially plays an important role in supporting tropical carbon sinks. Despite the importance of N2-fixation to the linked nitrogen and carbon cycles, we know little about how nutrient limitation of the process of biological N2-fixation, itself, will affect tropical fixation and N2-fixing plants. While rising CO2 levels may increase tree growth and N2-fixation when nutrients are abundant, at the same time, the increased growth may force N2-fixing plants into phosphorus (P) and molybdenum (Mo) limitation, both elements that are scarce in tropical forests and critical to N2-fixers. This study improves our understanding on what controls fixation through a series of greenhouse and in situ field experiments. First, we used a greenhouse experiment where we manipulated CO2 levels combined with a field study in forest gaps. In the greenhouse study we grew a N2-fixing seedling and a non-fixing seedling at pre-industrial (280 ppm), current (400 ppm), and double (800 ppm) CO2 concentrations with and without P, Mo, or both. In the year-long field study, we applied the same nutrient treatments to seedlings planting in natural light gaps and ambient CO2. To supplement our year-long seedling experiment, we also examined 11 years of growth data from a long-term N x P x K factorial fertilization experiment also on the Gigante Peninsula. In the greenhouse study, we found nutrient limitation was minimal at pre-industrial CO2 levels, but that limitation appeared with increasing CO2. Phosphorus limitation of tree growth and N2-fixation significantly increased with higher CO2. The additions of Mo and P together allowed for even greater growth and fixation, suggesting Mo-P co-limitation at elevated CO2. Compared to

  8. Methanotrophic N2-Fixation in Boreal Peatlands: Master Regulation of Newly Fixed N and Moderation of CH4 Fluxes to the Atmosphere

    NASA Astrophysics Data System (ADS)

    Schlesinger, M.; Fillingim, H. M.; Wieder, R. K.; Vile, M. A.

    2015-12-01

    Boreal peatlands are important to global carbon (C) and nitrogen (N) cycling. While they cover only 3-4% of the terrestrial surface, they account for 25-30% and 9-15% of the world's soil C and N, respectively. Globally, peatlands function as a net sink for atmospheric CO2, but also act as a net source of CH4. In peatlands of Alberta, Canada, rates of atmospheric N deposition are low: ~1 kg·ha-1·yr-1, however, NPP of Sphagnum mosses is surprisingly high. Sphagnum mosses are able to maintain high levels of NPP due to their symbiotic relationship with N2-fixing methanotrophs. Annually, rates of N2-fixation typically provide between 10-30 kg of newly fixed N per ha, while also oxidizing CH4. CH4 fluxes from boreal peatlands in Canada are typically quite low, however, fluxes also can be high during rare episodic ebullition events. CH4 accumulation and storage is substantial, especially at depth as CH4 concentrations in peat pore water typically exceed 1000 μM at 1-m below the peat surface. Given that CH4 fluxes are typically low, we wanted to examine the importance of CH4 oxidation in these same peats. We hypothesized that methanotrophic N2-fixation may be important not only in providing inputs of newly fixed N, but also in regulating CH4 emissions from peatlands. We measured concentrations of CH4 in peat porewaters, CH4 flux rates, CH4 oxidation rates, biological N2-fixation rates. Porewater CH4 concentrations were highest at depth and decreased to negligible amounts closer to the surface of the water table. CH4 flux rates were low and ranged from -2.6 to +8.7 μmol·m-2·min-1 (negative values indicate net CH4 consumption). In Sphagnum incubations, rates of CH4 oxidation (0.6-10.2 mmol·m-2·min-1) were ~2-3 orders of magnitude higher than CH4 flux rates. Additionally, N2-fixation rates in paired cores ranged from 11.7-63.3 kg·ha-1·yr-1; CH4 oxidation rates in these same units ranged from ~3.1-622 kg·CH4 oxidized ha-1·yr-1. Additionally, we confirmed that N2

  9. Photosynthesis, N(2) fixation and taproot reserves during the cutting regrowth cycle of alfalfa under elevated CO(2) and temperature.

    PubMed

    Erice, G; Sanz-Sáez, A; Aranjuelo, I; Irigoyen, J J; Aguirreolea, J; Avice, J-C; Sánchez-Díaz, M

    2011-11-15

    Future climatic conditions, including rising atmospheric CO(2) and temperature may increase photosynthesis and, consequently, plant production. A larger knowledge of legume performance under the predicted growth conditions will be crucial for safeguarding crop management and extending the area under cultivation with these plants in the near future. N(2) fixation is a key process conditioning plant responsiveness to varying growth conditions. Moreover, it is likely to increase under future environments, due to the higher photosynthate availability, as a consequence of the higher growth rate under elevated CO(2). However, as described in the literature, photosynthesis performance is frequently down-regulated (acclimated) under long-term exposure to CO(2), especially when affected by stressful temperature and water availability conditions. As growth responses to elevated CO(2) are dependent on sink-source status, it is generally accepted that down-regulation occurs in situations with insufficient plant C sink capacity. Alfalfa management involves the cutting of shoots, which alters the source-sink relationship and thus the photosynthetic behaviour. As the growth rate decreases at the end of the pre-cut vegetative growth period, nodulated alfalfa plants show photosynthetic down-regulation, but during regrowth following defoliation, acclimation to elevated CO(2) disappears. The shoot harvest also leads to a drop in mineral N uptake and C translocation to the roots, resulting in a reduction in N(2) fixation due to the dependence on photosynthate supply to support nodule function. Therefore, the production of new shoots during the first days following cutting requires the utilization of reduced C and N compounds that have been stored previously in reserve organs. The stored reserves are mediated by phytohormones such as methyl jasmonate and abscisic acid and in situations where water stress reduces shoot production this potentially enables the enhancement of taproot

  10. Symbiotic nitrogen fixation in a tropical rainforest: 15N natural abundance measurements supported by experimental isotopic enrichment.

    PubMed

    Pons, Thijs L; Perreijn, Kristel; van Kessel, Chris; Werger, Marinus J A

    2007-01-01

    * Leguminous trees are very common in the tropical rainforests of Guyana. Here, species-specific differences in N(2) fixation capability among nodulating legumes growing on different soils and a possible limitation of N(2) fixation by a relatively high nitrogen (N) and low phosphorus (P) availability in the forest were investigated. * Leaves of 17 nodulating species and 17 non-nodulating reference trees were sampled and their delta(15)N values measured. Estimates of N(2) fixation rates were calculated using the (15)N natural abundance method. Pot experiments were conducted on the effect of N and P availability on N(2) fixation using the (15)N-enriched isotope dilution method. * Nine species showed estimates of > 33% leaf N derived from N(2) fixation, while the others had low or undetectable N(2) fixation rates. High N and low P availability reduced N(2) fixation substantially. * The results suggest that a high N and low P availability in the forest limit N(2) fixation. At the forest ecosystem level, N(2) fixation was estimated at c. 6% of total N uptake by the tree community. We conclude that symbiotic N(2) fixation plays an important role in maintaining high amounts of soil available N in undisturbed forest.

  11. Symbiotic nitrogen fixation in a tropical rainforest: (15) N natural abundance measurements supported by experimental isotopic enrichment.

    PubMed

    Pons, Thijs L; Perreijn, Kristel; Van Kessel, Chris; Werger, Marinus J A

    2007-01-01

    •  Leguminous trees are very common in the tropical rainforests of Guyana. Here, species-specific differences in N2 fixation capability among nodulating legumes growing on different soils and a possible limitation of N2 fixation by a relatively high nitrogen (N) and low phosphorus (P) availability in the forest were investigated. •  Leaves of 17 nodulating species and 17 non-nodulating reference trees were sampled and their δ(15) N values measured. Estimates of N2 fixation rates were calculated using the (15) N natural abundance method. Pot experiments were conducted on the effect of N and P availability on N2 fixation using the (15) N-enriched isotope dilution method. •  Nine species showed estimates of > 33% leaf N derived from N2 fixation, while the others had low or undetectable N2 fixation rates. High N and low P availability reduced N2 fixation substantially. •  The results suggest that a high N and low P availability in the forest limit N2 fixation. At the forest ecosystem level, N2 fixation was estimated at c. 6% of total N uptake by the tree community. We conclude that symbiotic N2 fixation plays an important role in maintaining high amounts of soil available N in undisturbed forest.

  12. Effects of elevated CO2 and N addition on growth and N2 fixation of a legume subshrub (Caragana microphylla Lam.) in temperate grassland in China.

    PubMed

    Zhang, Lin; Wu, Dongxiu; Shi, Huiqiu; Zhang, Canjuan; Zhan, Xiaoyun; Zhou, Shuangxi

    2011-01-01

    It is well demonstrated that the responses of plants to elevated atmospheric CO(2) concentration are species-specific and dependent on environmental conditions. We investigated the responses of a subshrub legume species, Caragana microphylla Lam., to elevated CO(2) and nitrogen (N) addition using open-top chambers in a semiarid temperate grassland in northern China for three years. Measured variables include leaf photosynthetic rate, shoot biomass, root biomass, symbiotic nitrogenase activity, and leaf N content. Symbiotic nitrogenase activity was determined by the C(2)H(2) reduction method. Elevated CO(2) enhanced photosynthesis and shoot biomass by 83% and 25%, respectively, and the enhancement of shoot biomass was significant only at a high N concentration. In addition, the photosynthetic capacity of C. microphylla did not show down-regulation under elevated CO(2). Elevated CO(2) had no significant effect on root biomass, symbiotic nitrogenase activity and leaf N content. Under elevated CO(2), N addition stimulated photosynthesis and shoot biomass. By contrast, N addition strongly inhibited symbiotic nitrogenase activity and slightly increased leaf N content of C. microphylla under both CO(2) levels, and had no significant effect on root biomass. The effect of elevated CO(2) and N addition on C. microphylla did not show interannual variation, except for the effect of N addition on leaf N content. These results indicate that shoot growth of C. microphylla is more sensitive to elevated CO(2) than is root growth. The stimulation of shoot growth of C. microphylla under elevated CO(2) or N addition is not associated with changes in N(2)-fixation. Additionally, elevated CO(2) and N addition interacted to affect shoot growth of C. microphylla with a stimulatory effect occurring only under combination of these two factors.

  13. Sphagnum N and P Stoichiometry Indicates P-limitation on N2 Fixation in Ombrotrophic Bogs

    NASA Astrophysics Data System (ADS)

    Zivkovic, T.; Moore, T. R.; Disney, K.

    2015-12-01

    Biological N2 fixation is an important N input in ombrotrophic, nutrient poor and Sphagnum dominated bogs. As an energetically costly process, by which each N2 molecule is fixed to a cost of 16ATP molecules, N2 fixation might be P limited process. In this study we tested whether moss P and N concentrations, and N:P ratios could explain N2 fixation in the top 6cm photosynthetically active Sphagnum moss across eight ombrotrophic bogs along south-north geographical gradient in Ontario and Quebec. Under constant environmental conditions, we incubated subsamples of the surface Sphagnum mosses by using both, acetylene reduction assays (ARA) and 15N2 enriched method to measure N2 fixation rates. Same subsamples were later analyzed for N and P concentrations. Our preliminary data show that the increase of P concentration within moss capitula is related to a significant linear increase of ARA rates (R2=0.18, p<0.0001, N=150). N:P ratios showed a significant negative linear relationship with ARA (R2=0.34, p<0.0001, N=150) indicating that P limitation in the photosynthetically active part of mosses in bogs may also indicate P limitation on microbial N2 fixation

  14. The effect of acidity on the distribution and symbiotic efficiency of rhizobia in Lithuanian soils

    NASA Astrophysics Data System (ADS)

    Lapinskas, E. B.

    2007-04-01

    The distribution and symbiotic efficiency of nodule bacteria Rhizobium leguminosarum_bv. trifolii F., Sinorhizobium meliloti D., Rhizobium galegae L., and Rhizobium leguminosarum bv. viciae F. in Lithuanian soils as dependent on the soil acidity were studied in the long-term field, pot, and laboratory experiments. The critical and optimal pH values controlling the distribution of rhizobia and the symbiotic nitrogen fixation were determined for every bacterial species. The relationship was found between the soil pH and the nitrogen-fixing capacity of rhizobia. A positive effect of liming of acid soils in combination with inoculation of legumes on the efficiency of symbiotic nitrogen fixation was demonstrated.

  15. Biological N2-Fixation Increases with Peatland Age and Decreases with N Deposition in Bogs of Western Canada

    NASA Astrophysics Data System (ADS)

    Fillingim, H.; Popma, J. M.; Dynarski, K. A.; Wieder, R.; Vile, M. A.

    2013-12-01

    Most terrestrial ecosystems are thought be limited primarily by nitrogen, including boreal peatlands located in pristine regions. Bogs receive nutrients solely from atmospheric deposition. Because of the historically low rates of atmospheric nitrogen deposition in Alberta, Canada, the Sphagnum mosses that dominate bog ground cover in this region have formed relationships with diazotrophs in order to meet their nitrogen needs, making biological N2- fixation the dominant input of new nitrogen to these bogs. The process of N2-fixation is highly variable and is governed by a number of environmental factors. In Alberta, one factor is water availability, as these bogs occur in some of the driest climates in which peatlands are known to exist. More recent factors with the potential to greatly alter N2-fixation dynamics include increasing nitrogen deposition associated with the growing oil sands mining operations and wildfires increasing in frequency and severity with global climate change. To determine the potential importance of N2-fixation to the overall peatland nitrogen balance under current and future conditions, we incubated the moss Sphagnum fuscum, using the acetylene reduction assay calibrated with 15N2, from 3 bogs representing ages of 3, 13, and 30 years since fire. Each bog was fertilized 8 times throughout the growing season with 0, 10, and 20 kg N/ha/yr. N2-fixation rates were measured 5 times at each site throughout the summer of 2013 to account for variation due to season and weather. Mean rates of N2-fixation increased with bog age, with higher rates in the 30 year old bog (36.90 × 8.38) and subsequently lower rates in the 13 yr (25.08 × 5.63) and 3 yr (11.58 × 6.33) old bogs. As expected, we saw decreasing rates of N2-fixation in the 10 (16.96 × 5.39) and 20 kg N/ha/yr treatments (3.35 × 1.34), as compared to water-only controls (47.62 × 12.18). These results indicate that N2-fixation supplies abundant N to support net primary productivity for bogs

  16. SYMBIOTIC N2 FIXATION IN ALPINE TUNDRA: ECOSYSTEM INPUT AND VARIATION IN FIXATION RATES AMONG PLANT COMMUNITIES (R823442)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  17. Assessment of nutrient limitation on the primary production and N2 fixation across the tropical Atlantic

    NASA Astrophysics Data System (ADS)

    Ridame, C.; Mills, M. M.; Davey, M.; Laroche, J.; Geider, R.

    2003-04-01

    In the surface layer of the Tropical North Atlantic, Saharan dust inputs, as a source of iron and phosphate, might preferentially stimulate the growth of diazotrophs. The availability of iron, essential for the synthesis of the nitrogenase enzyme, and/or phosphorus through dust inputs is suspected to impose additional control on N_2 fixation in these waters chronically low in dissolved inorganic nitrogen. Here, we present results from the cruise M-55 (October--November 2002, SOLAS Program) in the tropical Atlantic (11^oN) between Curacao and Cameroon that address this hypothesis. The studied area was particularly interesting because it is characterized by a nutrient gradient from oligotrophic waters (Caribbean Sea) to upwelling dominated regions (NW Africa) and is also subject to a strong lateral gradient of inputs from Saharan mineral aerosol. Using trace metal clean methods, nutrient addition bioassays were used to asses which nutrient (N, P, and Fe) most likely limits of phytoplankton biomass, primary productivity and dinitrogen fixation in incubation experiments along the transect. An additional Saharan dust treatment, considered as a proxy for Saharan aerosol, was used to simulate an atmospheric Saharan dust input into the surface layer.

  18. Heterocystous Cyanobacteria in Microbialites Play an Important Role in N2 Fixation and Carbonate Mineral Precipitation

    NASA Astrophysics Data System (ADS)

    Alcantara-Hernandez, R. J.

    2015-12-01

    Lake Alchichica is a maars type crater-lake located in Central Mexico (pH > 8.9, EC ~13.39 mS cm-1). This limnological system harbors two types of microbialites that can be found around the entire perimeter of the lake (Fig. 1). These structures are representative examples of complex and diverse microbiological assemblages, where microbial activity promotes lithification by trapping, binding and/or precipitating detrital or chemical sediments. Previous studies determined that the microbialites of Lake Alchichica fix N2 to thrive under the N-limiting conditions of the lake, and that these nitrogenase activity peaks are related to heterocystous cyanobacteria that couple photosynthesis to N2 fixation during daylight periods. Heterocystous cyanobacteria (Nostocales) together with Oscillatoriales (non-heterocystous filamentous cyanobacteria) and other cyanobacterial groups have been described as the most abundant cyanobacteria in Alchichica microbialites, and in lithifying mats. Our results suggest that heterocystous cyanobacteria play an important role not only by fixing N2 for biomass construction, but also because their heterocysts host in their external cell membranes main sites for carbonate mineral precipitation including calcium carbonates and siderite. Previous research has shown that the heterocyst is the specialized site for cellular respiration associated to the pH decrease of vegetative/photosynthetic cells, contributing thus to the precipitation of carbonates and the accretion of the organosedimentary structure

  19. Revisiting N2 fixation in Guerrero Negro intertidal microbial mats with a functional single-cell approach

    DOE PAGES

    Woebken, Dagmar; Burow, Luke C.; Behnam, Faris; ...

    2014-10-10

    Photosynthetic microbial mats are complex, stratified ecosystems in which high rates of primary production create a demand for nitrogen, met partially by N2 fixation. Dinitrogenase reductase (nifH) genes and transcripts from Cyanobacteria and heterotrophic bacteria (for example, Deltaproteobacteria) were detected in these mats, yet their contribution to N2 fixation is poorly understood. We used a combined approach of manipulation experiments with inhibitors, nifH sequencing and single-cell isotope analysis to investigate the active diazotrophic community in intertidal microbial mats at Laguna Ojo de Liebre near Guerrero Negro, Mexico. Acetylene reduction assays with specific metabolic inhibitors suggested that both sulfate reducers andmore » members of the Cyanobacteria contributed to N2 fixation, whereas 15N2 tracer experiments at the bulk level only supported a contribution of Cyanobacteria. Cyanobacterial and nifH Cluster III (including deltaproteobacterial sulfate reducers) sequences dominated the nifH gene pool, whereas the nifH transcript pool was dominated by sequences related to Lyngbya spp. Single-cell isotope analysis of 15N2-incubated mat samples via high-resolution secondary ion mass spectrometry (NanoSIMS) revealed that Cyanobacteria were enriched in 15N, with the highest enrichment being detected in Lyngbya spp. filaments (on average 4.4 at% 15N), whereas the Deltaproteobacteria (identified by CARD-FISH) were not significantly enriched. We investigated the potential dilution effect from CARD-FISH on the isotopic composition and concluded that the dilution bias was not substantial enough to influence our conclusions. As a result, our combined data provide evidence that members of the Cyanobacteria, especially Lyngbya spp., actively contributed to N2 fixation in the intertidal mats, whereas support for significant N2 fixation activity of the targeted deltaproteobacterial sulfate reducers could not be found.« less

  20. Revisiting N2 fixation in Guerrero Negro intertidal microbial mats with a functional single-cell approach

    PubMed Central

    Woebken, Dagmar; Burow, Luke C; Behnam, Faris; Mayali, Xavier; Schintlmeister, Arno; Fleming, Erich D; Prufert-Bebout, Leslie; Singer, Steven W; Cortés, Alejandro López; Hoehler, Tori M; Pett-Ridge, Jennifer; Spormann, Alfred M; Wagner, Michael; Weber, Peter K; Bebout, Brad M

    2015-01-01

    Photosynthetic microbial mats are complex, stratified ecosystems in which high rates of primary production create a demand for nitrogen, met partially by N2 fixation. Dinitrogenase reductase (nifH) genes and transcripts from Cyanobacteria and heterotrophic bacteria (for example, Deltaproteobacteria) were detected in these mats, yet their contribution to N2 fixation is poorly understood. We used a combined approach of manipulation experiments with inhibitors, nifH sequencing and single-cell isotope analysis to investigate the active diazotrophic community in intertidal microbial mats at Laguna Ojo de Liebre near Guerrero Negro, Mexico. Acetylene reduction assays with specific metabolic inhibitors suggested that both sulfate reducers and members of the Cyanobacteria contributed to N2 fixation, whereas 15N2 tracer experiments at the bulk level only supported a contribution of Cyanobacteria. Cyanobacterial and nifH Cluster III (including deltaproteobacterial sulfate reducers) sequences dominated the nifH gene pool, whereas the nifH transcript pool was dominated by sequences related to Lyngbya spp. Single-cell isotope analysis of 15N2-incubated mat samples via high-resolution secondary ion mass spectrometry (NanoSIMS) revealed that Cyanobacteria were enriched in 15N, with the highest enrichment being detected in Lyngbya spp. filaments (on average 4.4 at% 15N), whereas the Deltaproteobacteria (identified by CARD-FISH) were not significantly enriched. We investigated the potential dilution effect from CARD-FISH on the isotopic composition and concluded that the dilution bias was not substantial enough to influence our conclusions. Our combined data provide evidence that members of the Cyanobacteria, especially Lyngbya spp., actively contributed to N2 fixation in the intertidal mats, whereas support for significant N2 fixation activity of the targeted deltaproteobacterial sulfate reducers could not be found. PMID:25303712

  1. Molybdenum isotope fractionation by cyanobacterial assimilation during nitrate utilization and N2fixation

    PubMed Central

    Zerkle, A L; Scheiderich, K; Maresca, J A; Liermann, L J; Brantley, S L

    2011-01-01

    We measured the δ98Mo of cells and media from molybdenum (Mo) assimilation experiments with the freshwater cyanobacterium Anabaena variabilis, grown with nitrate as a nitrogen (N) source or fixing atmospheric N2. This organism uses a Mo-based nitrate reductase during nitrate utilization and a Mo-based dinitrogenase during N2 fixation under culture conditions here. We also demonstrate that it has a high-affinity Mo uptake system (ModABC) similar to other cyanobacteria, including marine N2-fixing strains. Anabaena variabilis preferentially assimilated light isotopes of Mo in all experiments, resulting in fractionations of −0.2‰ to −1.0‰ ± 0.2‰ between cells and media (εcells–media), extending the range of biological Mo fractionations previously reported. The fractionations were internally consistent within experiments, but varied with the N source utilized and for different growth phases sampled. During growth on nitrate, A. variabilis consistently produced fractionations of −0.3 ± 0.1‰ (mean ± standard deviation between experiments). When fixing N2, A. variabilis produced fractionations of −0.9 ± 0.1‰ during exponential growth, and −0.5 ± 0.1‰ during stationary phase. This pattern is inconsistent with a simple kinetic isotope effect associated with Mo transport, because Mo is likely transported through the ModABC uptake system under all conditions studied. We present a reaction network model for Mo isotope fractionation that demonstrates how Mo transport and storage, coordination changes during enzymatic incorporation, and the distribution of Mo inside the cell could all contribute to the total biological fractionations. Additionally, we discuss the potential importance of biologically incorporated Mo to organic matter-bound Mo in marine sediments. PMID:21092069

  2. [Symbiotic efficiency and genetic diversity of the rhizobia isolated from Leucaena leucocephala in Liangshan Prefecture].

    PubMed

    Xu, Kaiwei; Zhang, Xiaoping; Chen, Yuanxue; Gu, Feiyue; Zhou, Dehai; Tang, Chengyi

    2014-05-04

    We analyzed the symbiotic efficiency and genetic diversity of rhizobia isolated from Leucaena leucocephala in Liangshan Prefecture of SichuanProvince. We studied genetic diversity of these isolates with 16S rRNA RFLP, BOX-PCR and AFLP fingerprinting, and constructed phylogenetic tree based on the concatenated sequences of the four housekeeping genes 16S rRNA, recA, atpD and glnII. The nodulation ability and the symbiotic efficiency of the isolates were tested by plant inoculation assay on their original host plant. Genetic diversity and phylogenetic tree indicate that 26 isolates were assigned as Sinorhizobium, 3 Bradyrhizobium, 3 Rhizobium and 1 Mesorhizobium. SCAU203 might represent a new Rhizobium group, SCAU211 might represent a new Bradyrhizobium group, the other three representative strains were located in three phylogenic branches and closely related to S. americanum, M. plurifarium and R. huautlense, respectively. In the nodulation and symbiotic efficiency assay, only 2 of the 20 isolates promoted the growth of L. leucocephala, but 3 isolates had a growth slowing effect on the host, while the other isolates (84%) were ineffective on symbiotic nitrogen fixation. The majority of rhizobia isolated from L. leucocephala in Liangshan Prefecture were ineffective on symbiotic nitrogen fixation.

  3. Rates and Controls of N2 Fixation in Sphagnum spp. along the Hydrological Gradient - Beaver Pond to Bog Transition at Mer Bleue, Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Zivkovic, T.; Moore, T. R.

    2014-12-01

    Many northern bogs with low atmospheric N inputs acquire N only via N2-fixation. Little is known about rates and controls on N2-fixation in bogs. The aim of this study was to: 1) test the important ecological drivers for N2-fixation, 2) investigate seasonal and temporal patterns of N2 fixation, and 3) to estimate current N2-fixation rates at Mer Bleue bog. We used acetylene reduction assay (ARA) to measure N2-fixation from June-October 2013 and 2014 (currently ongoing field season) along a hydrological gradient (beaver pond, hollows and hummocks). The highest ARA rates in 2013 growing season occurred in the pond in floating Sphagnum cuspidatum mats (50.3 ± 12.9 μmol m-2 d-1 Mean ± Std Err) which were up to 2.5 times latger than the rates found in the hummock with the lowest water table depth throughout the season. Two rain events during the summer 2013 increased ARA rates in all plots by 1 to 4 times, suggesting that moisture availability may play a crucial role on N2 fixation potential in the field. We are currently investigating the role of moisture, temperature, PAR and nutrient content (N, phosphorous and metals) on ARA along the gradient. In addition, we are using 15N2 enrichment method to estimate N2 fixation rates and compare them to ARA method at Mer Bleue bog.

  4. Low contribution of N2 fixation to new production and excess nitrogen in the subtropical northeast Atlantic margin

    NASA Astrophysics Data System (ADS)

    Benavides, Mar; Arístegui, Javier; Agawin, Nona S. R.; Álvarez-Salgado, Xosé Antón; Álvarez, Marta; Troupin, Charles

    2013-11-01

    We used 15N-labeled substrates to measure dinitrogen (N2) fixation, nitrate (NO3-) and ammonium () uptake, regeneration and associated dissolved organic nitrogen (DON) release in a coastal upwelling system (Cape Ghir, ˜31°N) and an open ocean grid (bounded between 25°-42°N and 20°W) in the Canary Current region during the summer of 2009. New production (Pnew=NO3-uptake+N2 fixation+DON released from NO3uptake-NO3- regeneration) was higher in the upwelling than in the open ocean zone (0.126 and 0.014 µmol N L-1 h-1, respectively), while regenerated production (Preg=NH4+ uptake+DON released from NH4+uptake+NH4+ regeneration) was similar in both zones (0.157 and 0.133 µmol N L-1 h-1, respectively). The resulting f-ratio (Pnew/Pnew+Preg) for the open ocean and upwelling zones was 0.08 and 0.48, respectively. The availability of nitrogen in excess of that expected from Redfield stoichiometry is generally attributed to N2 fixation. A previous study indicated that our open ocean grid zone had an excess nitrogen production rate of 40±22×1010 mol N yr-1. We revisited this budget including new dissolved organic matter and NO3-fluxes through the Strait of Gibraltar and estimated a revised nitrogen excess rate of 22±19×1010 mol N yr-1. The average volumetric rate of N2 fixation for this zone was only 1.3×10-3 nmol N L-1 d-1, indicating that its influence in Pnew and nitrogen excess production in this part of the Atlantic is negligible.

  5. Enhanced N2-fixation and NH4+ recycling during oceanic anoxic event 2 in the proto-North Atlantic

    NASA Astrophysics Data System (ADS)

    Ruvalcaba Baroni, I.; Tsandev, I.; Slomp, C. P.

    2014-10-01

    from sediment core records and model studies suggests that increased nutrient supply played a key role in the initiation of the Cenomanian-Turonian oceanic anoxic event 2 (OAE2; 94 Ma). However, the relative roles of nitrogen (N) and phosphorus (P) availability in controlling primary productivity during the event are not fully understood. Here we expand an existing multibox model of the coupled cycles of P, carbon, and oxygen in the proto-North Atlantic by adding the marine N cycle. With the updated version of the model, we test the hypothesis that enhanced availability of P can fuel N2-fixation, increase primary productivity and drive large parts of the proto-North Atlantic to anoxia during OAE2. In a sensitivity analysis, we demonstrate that N dynamics in the proto-North Atlantic respond strongly to variations in oxygen and P supply from the Pacific Ocean and to changes in circulation. The implemented N cycle weakly modifies the carbon cycle, implying that P was the major nutrient controlling primary productivity during OAE2. Our model suggests that both N2-fixation and upwelling of recycled NH4+ were enhanced during OAE2 and that N2-fixation was the major source of N in the proto-North Atlantic. Denitrification was more important in the water column than in sediments, with high rates in the open ocean and in the Western Interior. High P inputs in the proto-North Atlantic led to widespread N2-fixation, which more than compensated for the loss of N through denitrification. As a consequence, rates of primary productivity and organic carbon burial were high.

  6. N2-fixation, ammonium release and N-transfer to the microbial and classical food web within a plankton community.

    PubMed

    Adam, Birgit; Klawonn, Isabell; Svedén, Jennie B; Bergkvist, Johanna; Nahar, Nurun; Walve, Jakob; Littmann, Sten; Whitehouse, Martin J; Lavik, Gaute; Kuypers, Marcel M M; Ploug, Helle

    2016-02-01

    We investigated the role of N2-fixation by the colony-forming cyanobacterium, Aphanizomenon spp., for the plankton community and N-budget of the N-limited Baltic Sea during summer by using stable isotope tracers combined with novel secondary ion mass spectrometry, conventional mass spectrometry and nutrient analysis. When incubated with (15)N2, Aphanizomenon spp. showed a strong (15)N-enrichment implying substantial (15)N2-fixation. Intriguingly, Aphanizomenon did not assimilate tracers of (15)NH4(+) from the surrounding water. These findings are in line with model calculations that confirmed a negligible N-source by diffusion-limited NH4(+) fluxes to Aphanizomenon colonies at low bulk concentrations (<250 nm) as compared with N2-fixation within colonies. No N2-fixation was detected in autotrophic microorganisms <5 μm, which relied on NH4(+) uptake from the surrounding water. Aphanizomenon released about 50% of its newly fixed N2 as NH4(+). However, NH4(+) did not accumulate in the water but was transferred to heterotrophic and autotrophic microorganisms as well as to diatoms (Chaetoceros sp.) and copepods with a turnover time of ~5 h. We provide direct quantitative evidence that colony-forming Aphanizomenon releases about half of its recently fixed N2 as NH4(+), which is transferred to the prokaryotic and eukaryotic plankton forming the basis of the food web in the plankton community. Transfer of newly fixed nitrogen to diatoms and copepods furthermore implies a fast export to shallow sediments via fast-sinking fecal pellets and aggregates. Hence, N2-fixing colony-forming cyanobacteria can have profound impact on ecosystem productivity and biogeochemical processes at shorter time scales (hours to days) than previously thought.

  7. N2-fixation, ammonium release and N-transfer to the microbial and classical food web within a plankton community

    PubMed Central

    Adam, Birgit; Klawonn, Isabell; Svedén, Jennie B; Bergkvist, Johanna; Nahar, Nurun; Walve, Jakob; Littmann, Sten; Whitehouse, Martin J; Lavik, Gaute; Kuypers, Marcel M M; Ploug, Helle

    2016-01-01

    We investigated the role of N2-fixation by the colony-forming cyanobacterium, Aphanizomenon spp., for the plankton community and N-budget of the N-limited Baltic Sea during summer by using stable isotope tracers combined with novel secondary ion mass spectrometry, conventional mass spectrometry and nutrient analysis. When incubated with 15N2, Aphanizomenon spp. showed a strong 15N-enrichment implying substantial 15N2-fixation. Intriguingly, Aphanizomenon did not assimilate tracers of 15NH4+ from the surrounding water. These findings are in line with model calculations that confirmed a negligible N-source by diffusion-limited NH4+ fluxes to Aphanizomenon colonies at low bulk concentrations (<250 nm) as compared with N2-fixation within colonies. No N2-fixation was detected in autotrophic microorganisms <5 μm, which relied on NH4+ uptake from the surrounding water. Aphanizomenon released about 50% of its newly fixed N2 as NH4+. However, NH4+ did not accumulate in the water but was transferred to heterotrophic and autotrophic microorganisms as well as to diatoms (Chaetoceros sp.) and copepods with a turnover time of ~5 h. We provide direct quantitative evidence that colony-forming Aphanizomenon releases about half of its recently fixed N2 as NH4+, which is transferred to the prokaryotic and eukaryotic plankton forming the basis of the food web in the plankton community. Transfer of newly fixed nitrogen to diatoms and copepods furthermore implies a fast export to shallow sediments via fast-sinking fecal pellets and aggregates. Hence, N2-fixing colony-forming cyanobacteria can have profound impact on ecosystem productivity and biogeochemical processes at shorter time scales (hours to days) than previously thought. PMID:26262817

  8. Mesopelagic N2 Fixation Related to Organic Matter Composition in the Solomon and Bismarck Seas (Southwest Pacific).

    PubMed

    Benavides, Mar; Moisander, Pia H; Berthelot, Hugo; Dittmar, Thorsten; Grosso, Olivier; Bonnet, Sophie

    2015-01-01

    Dinitrogen (N2) fixation was investigated together with organic matter composition in the mesopelagic zone of the Bismarck (Transect 1) and Solomon (Transect 2) Seas (Southwest Pacific). Transparent exopolymer particles (TEP) and the presence of compounds sharing molecular formulae with saturated fatty acids and sugars, as well as dissolved organic matter (DOM) compounds containing nitrogen (N) and phosphorus (P) were higher on Transect 1 than on Transect 2, while oxygen concentrations showed an opposite pattern. N2 fixation rates (up to ~1 nmol N L-1 d-1) were higher in Transect 1 than in Transect 2, and correlated positively with TEP, suggesting a dependence of diazotroph activity on organic matter. The scores of the multivariate ordination of DOM molecular formulae and their relative abundance correlated negatively with bacterial abundances and positively with N2 fixation rates, suggesting an active bacterial exploitation of DOM and its use to sustain diazotrophic activity. Sequences of the nifH gene clustered with Alpha-, Beta-, Gamma- and Deltaproteobacteria, and included representatives from Clusters I, III and IV. A third of the clone library included sequences close to the potentially anaerobic Cluster III, suggesting that N2 fixation was partially supported by presumably particle-attached diazotrophs. Quantitative polymerase chain reaction (qPCR) primer-probe sets were designed for three phylotypes and showed low abundances, with a phylotype within Cluster III at up to 103 nifH gene copies L-1. These results provide new insights into the ecology of non-cyanobacterial diazotrophs and suggest that organic matter sustains their activity in the mesopelagic ocean.

  9. Does N2 Fixation in the Oligotrophic SE Pacific Influence N Isotopic Signals in the Peru-Chile OMZ?

    NASA Astrophysics Data System (ADS)

    Altabet, M. A.; Ryabenko, E.; Wallace, D.

    2010-12-01

    Nitrate reduction leading to fixed N loss (‘denitrification’) in open ocean O2 minimum zones (OMZ’s) produces large N isotope enrichments in the residual nitrate. Through upwelling, phytoplankton assimilation, and downward particle flux, this signal is transferred to the underlying sediments and has been used to reconstruct past changes in denitrification and OMZ intensity in relation to climate change. However, there remain a number of impediments to quantitative interpretation of downcore δ15N records from OMZ’s with respect to past magnitude of N loss. One of these is knowledge of initial δ15N for nitrate prior to denitrification which cannot be assumed to be the modern oceanic average. In the case of the Peru-Chile OMZ, δ15N for nitrate in source waters from the Equatorial Undercurrent average 7‰ as compared to the oceanic average of ~5‰. This suggests processes external to the OMZ leading to isotopic enrichment such as partial phytoplankton nitrate utilization in the Subantarctic water mass formation region. In contrast, it has been surmised that initial δ15N for OMZ denitrification could be relatively low as a result of N2 fixation in geographically adjacent oligotrophic regions. High N2 fixation rates in the SE Pacifc Gyre are thought to be stimulated by low N/P waters upwelled from the Peru-Chile OMZ. As seen in the Sargasso Sea, subsurface remineralization of export production influenced by near-surface N2 fixation produces 15N-depleted nitrate in the subtropical mode water and the upper thermocline. Potentially, these SE Pacific gyre waters could mix back into the Peru-Chile OMZ at its southern boundary. We have investigated the relevance of such a phenomenon in the SE Pacific by examining samples collected during two CLIVAR repeat section (P6 and P18) which transected these highly oligotrophic water adjacent to the Peru-Chile OMZ in both the N-S and Ε-W directions. Surprisingly, nutrient data shows no positive subsurface nitrate anomaly

  10. Longitudinal variability of size-fractionated N2 fixation and DON release rates along 24.5°N in the subtropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Benavides, Mar; Bronk, Deborah A.; Agawin, Nona S. R.; PéRez-HernáNdez, M. Dolores; HernáNdez-Guerra, Alonso; AríStegui, Javier

    2013-07-01

    Dinitrogen (N2) fixation and dissolved organic nitrogen (DON) release rates were measured on fractionated samples (>10 µm and <10 µm) along 24.5∘N in the subtropical North Atlantic. Net N2 fixation rates (N2 assimilation into biomass) ranged from 0.01 to 0.4 nmol N L-1 h-1, and DON release rates ranged from 0.001 to 0.09 nmol N L-1 h-1. DON release represented ˜14% and ˜23% of >10 µm and <10 µm gross N2 fixation (assimilation into biomass plus DON release), respectively. This implies that by overlooking DON release, N2 fixation rates are underestimated. Net N2 fixation rates were higher in the east and decreased significantly toward the west (rs = -0.487, p = 0.002, and rs = -0.496, p = 0.001, for the >10 µm and <10 µm fractions, respectively). The sum of both fractions correlated with aerosol optical depth at 550 nm (AOD 550 nm) (rs = 0.382, p = 0.017) and phosphate (PO43-) concentrations (rs = 0.453, p = 0.018), suggesting an enhancement of diazotrophy as a response to aerosol inputs and phosphorus availability. In contrast, DON release was constant among size fractions and did not correlate with any of these variables. We also compared N2 fixation rates obtained using the 15N2 dissolved and bubble methods. The first gave average rates 50% (49% ± 39) higher than the latter, which supports the finding that previously published N2 fixation rates are likely underestimated. We suggest that by combining N2 fixation and DON release measurements using dissolved 15N2, global N2 fixation rates could increase enough to balance oceanic fixed nitrogen budget disequilibria.

  11. Genetic Diversity and Symbiotic Efficiency of Indigenous Common Bean Rhizobia in Croatia

    PubMed Central

    Pohajda, Ines; Babić, Katarina Huić; Rajnović, Ivana; Kajić, Sanja

    2016-01-01

    Summary Nodule bacteria (rhizobia) in symbiotic associations with legumes enable considerable entries of biologically fixed nitrogen into soil. Efforts are therefore made to intensify the natural process of symbiotic nitrogen fixation by legume inoculation. Studies of field populations of rhizobia open up the possibility to preserve and probably exploit some indigenous strains with hidden symbiotic or ecological potentials. The main aim of the present study is to determine genetic diversity of common bean rhizobia isolated from different field sites in central Croatia and to evaluate their symbiotic efficiency and compatibility with host plants. The isolation procedure revealed that most soil samples contained no indigenous common bean rhizobia. The results indicate that the cropping history had a significant impact on the presence of indigenous strains. Although all isolates were found to belong to species Rhizobium leguminosarum, significant genetic diversity at the strain level was determined. Application of both random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus–polymerase chain reaction (ERIC- -PCR) methods resulted in similar grouping of strains. Symbiotic efficiency of indigenous rhizobia as well as their compatibility with two commonly grown bean varieties were tested in field experiments. Application of indigenous rhizobial strains as inoculants resulted in significantly different values of nodulation, seed yield as well as plant nitrogen and seed protein contents. The most abundant nodulation and the highest plant nitrogen and protein contents were determined in plants inoculated with R. leguminosarum strains S17/2 and S21/6. Although, in general, the inoculation had a positive impact on seed yield, differences depending on the applied strain were not determined. The overall results show the high degree of symbiotic efficiency of the specific indigenous strain S21/6. These results indicate different

  12. Genetic Diversity and Symbiotic Efficiency of Indigenous Common Bean Rhizobia in Croatia.

    PubMed

    Pohajda, Ines; Babić, Katarina Huić; Rajnović, Ivana; Kajić, Sanja; Sikora, Sanja

    2016-12-01

    Nodule bacteria (rhizobia) in symbiotic associations with legumes enable considerable entries of biologically fixed nitrogen into soil. Efforts are therefore made to intensify the natural process of symbiotic nitrogen fixation by legume inoculation. Studies of field populations of rhizobia open up the possibility to preserve and probably exploit some indigenous strains with hidden symbiotic or ecological potentials. The main aim of the present study is to determine genetic diversity of common bean rhizobia isolated from different field sites in central Croatia and to evaluate their symbiotic efficiency and compatibility with host plants. The isolation procedure revealed that most soil samples contained no indigenous common bean rhizobia. The results indicate that the cropping history had a significant impact on the presence of indigenous strains. Although all isolates were found to belong to species Rhizobium leguminosarum, significant genetic diversity at the strain level was determined. Application of both random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC- -PCR) methods resulted in similar grouping of strains. Symbiotic efficiency of indigenous rhizobia as well as their compatibility with two commonly grown bean varieties were tested in field experiments. Application of indigenous rhizobial strains as inoculants resulted in significantly different values of nodulation, seed yield as well as plant nitrogen and seed protein contents. The most abundant nodulation and the highest plant nitrogen and protein contents were determined in plants inoculated with R. leguminosarum strains S17/2 and S21/6. Although, in general, the inoculation had a positive impact on seed yield, differences depending on the applied strain were not determined. The overall results show the high degree of symbiotic efficiency of the specific indigenous strain S21/6. These results indicate different symbiotic

  13. Development of a new biofertilizer with a high capacity for N2 fixation, phosphate and potassium solubilization and auxin production.

    PubMed

    Leaungvutiviroj, Chaveevan; Ruangphisarn, Pimtida; Hansanimitkul, Pikul; Shinkawa, Hidenori; Sasaki, Ken

    2010-01-01

    Biofertilizers that possess a high capacity for N(2) fixation (Azotobacter tropicalis), and consist of phosphate solubilizing bacteria (Burkhoderia unamae), and potassium solubilizing bacteria (Bacillus subtilis) and produce auxin (KJB9/2 strain), have a high potential for growth and yield enhancement of corn and vegetables (Chinese kale). For vegetables, the addition of biofertilizer alone enhanced growth 4 times. Moreover, an enhancement of growth by 7 times was observed due to the addition of rock phosphate and K-feldspar, natural mineral fertilizers, in combination with the biofertilizer.

  14. Free-air CO2 enrichment (FACE) reduces the inhibitory effect of soil nitrate on N2 fixation of Pisum sativum

    PubMed Central

    Butterly, Clayton R.; Armstrong, Roger; Chen, Deli; Tang, Caixian

    2016-01-01

    Background and Aims Additional carbohydrate supply resulting from enhanced photosynthesis under predicted future elevated CO2 is likely to increase symbiotic nitrogen (N) fixation in legumes. This study examined the interactive effects of atmospheric CO2 and nitrate (NO3–) concentration on the growth, nodulation and N fixation of field pea (Pisum sativum) in a semi-arid cropping system. Methods Field pea was grown for 15 weeks in a Vertosol containing 5, 25, 50 or 90 mg NO3–-N kg–1 under either ambient CO2 (aCO2; 390 ppm) or elevated CO2 (eCO2; 550 ppm) using free-air CO2 enrichment (SoilFACE). Key Results Under aCO2, field pea biomass was significantly lower at 5 mg NO3–-N kg–1 than at 90 mg NO3–-N kg–1 soil. However, increasing the soil N level significantly reduced nodulation of lateral roots but not the primary root, and nodules were significantly smaller, with 85 % less nodule mass in the 90 NO3–-N kg–1 than in the 5 mg NO3–-N kg–1 treatment, highlighting the inhibitory effects of NO3–. Field pea grown under eCO2 had greater biomass (approx. 30 %) than those grown under aCO2, and was not affected by N level. Overall, the inhibitory effects of NO3– on nodulation and nodule mass appeared to be reduced under eCO2 compared with aCO2, although the effects of CO2 on root growth were not significant. Conclusions Elevated CO2 alleviated the inhibitory effect of soil NO3– on nodulation and N2 fixation and is likely to lead to greater total N content of field pea growing under future elevated CO2 environments. PMID:26346721

  15. Levels of daily light doses under changed day-night cycles regulate temporal segregation of photosynthesis and N2 Fixation in the cyanobacterium Trichodesmium erythraeum IMS101.

    PubMed

    Cai, Xiaoni; Gao, Kunshan

    2015-01-01

    While the diazotrophic cyanobacterium Trichodesmium is known to display inverse diurnal performances of photosynthesis and N2 fixation, such a phenomenon has not been well documented under different day-night (L-D) cycles and different levels of light dose exposed to the cells. Here, we show differences in growth, N2 fixation and photosynthetic carbon fixation as well as photochemical performances of Trichodesmium IMS101 grown under 12L:12D, 8L:16D and 16L:8D L-D cycles at 70 μmol photons m-2 s-1 PAR (LL) and 350 μmol photons m-2 s-1 PAR (HL). The specific growth rate was the highest under LL and the lowest under HL under 16L:8D, and it increased under LL and decreased under HL with increased levels of daytime light doses exposed under the different light regimes, respectively. N2 fixation and photosynthetic carbon fixation were affected differentially by changes in the day-night regimes, with the former increasing directly under LL with increased daytime light doses and decreased under HL over growth-saturating light levels. Temporal segregation of N2 fixation from photosynthetic carbon fixation was evidenced under all day-night regimes, showing a time lag between the peak in N2 fixation and dip in carbon fixation. Elongation of light period led to higher N2 fixation rate under LL than under HL, while shortening the light exposure to 8 h delayed the N2 fixation peaking time (at the end of light period) and extended it to night period. Photosynthetic carbon fixation rates and transfer of light photons were always higher under HL than LL, regardless of the day-night cycles. Conclusively, diel performance of N2 fixation possesses functional plasticity, which was regulated by levels of light energy supplies either via changing light levels or length of light exposure.

  16. Levels of Daily Light Doses Under Changed Day-Night Cycles Regulate Temporal Segregation of Photosynthesis and N2 Fixation in the Cyanobacterium Trichodesmium erythraeum IMS101

    PubMed Central

    Cai, Xiaoni; Gao, Kunshan

    2015-01-01

    While the diazotrophic cyanobacterium Trichodesmium is known to display inverse diurnal performances of photosynthesis and N2 fixation, such a phenomenon has not been well documented under different day-night (L-D) cycles and different levels of light dose exposed to the cells. Here, we show differences in growth, N2 fixation and photosynthetic carbon fixation as well as photochemical performances of Trichodesmium IMS101 grown under 12L:12D, 8L:16D and 16L:8D L-D cycles at 70 μmol photons m-2 s-1 PAR (LL) and 350 μmol photons m-2 s-1 PAR (HL). The specific growth rate was the highest under LL and the lowest under HL under 16L:8D, and it increased under LL and decreased under HL with increased levels of daytime light doses exposed under the different light regimes, respectively. N2 fixation and photosynthetic carbon fixation were affected differentially by changes in the day-night regimes, with the former increasing directly under LL with increased daytime light doses and decreased under HL over growth-saturating light levels. Temporal segregation of N2 fixation from photosynthetic carbon fixation was evidenced under all day-night regimes, showing a time lag between the peak in N2 fixation and dip in carbon fixation. Elongation of light period led to higher N2 fixation rate under LL than under HL, while shortening the light exposure to 8 h delayed the N2 fixation peaking time (at the end of light period) and extended it to night period. Photosynthetic carbon fixation rates and transfer of light photons were always higher under HL than LL, regardless of the day-night cycles. Conclusively, diel performance of N2 fixation possesses functional plasticity, which was regulated by levels of light energy supplies either via changing light levels or length of light exposure. PMID:26258473

  17. Symbiosis revisited: phosphorus and acid buffering stimulate N2 fixation but not Sphagnum growth

    NASA Astrophysics Data System (ADS)

    van den Elzen, Eva; Kox, Martine A. R.; Harpenslager, Sarah F.; Hensgens, Geert; Fritz, Christian; Jetten, Mike S. M.; Ettwig, Katharina F.; Lamers, Leon P. M.

    2017-03-01

    In pristine Sphagnum-dominated peatlands, (di)nitrogen (N2) fixing (diazotrophic) microbial communities associated with Sphagnum mosses contribute substantially to the total nitrogen input, increasing carbon sequestration. The rates of symbiotic nitrogen fixation reported for Sphagnum peatlands, are, however, highly variable, and experimental work on regulating factors that can mechanistically explain this variation is largely lacking. For two common fen species (Sphagnum palustre and S. squarrosum) from a high nitrogen deposition area (25 kg N ha-1 yr-1), we found that diazotrophic activity (as measured by 15 - 15N2 labeling) was still present at a rate of 40 nmol N gDW-1 h-1. This was surprising, given that nitrogen fixation is a costly process. We tested the effects of phosphorus availability and buffering capacity by bicarbonate-rich water, mimicking a field situation in fens with stronger groundwater or surface water influence, as potential regulators of nitrogen fixation rates and Sphagnum performance. We expected that the addition of phosphorus, being a limiting nutrient, would stimulate both diazotrophic activity and Sphagnum growth. We indeed found that nitrogen fixation rates were doubled. Plant performance, in contrast, did not increase. Raised bicarbonate levels also enhanced nitrogen fixation, but had a strong negative impact on Sphagnum performance. These results explain the higher nitrogen fixation rates reported for minerotrophic and more nutrient-rich peatlands. In addition, nitrogen fixation was found to strongly depend on light, with rates 10 times higher in light conditions suggesting high reliance on phototrophic organisms for carbon. The contrasting effects of phosphorus and bicarbonate on Sphagnum spp. and their diazotrophic communities reveal strong differences in the optimal niche for both partners with respect to conditions and resources. This suggests a trade-off for the symbiosis of nitrogen fixing microorganisms with their Sphagnum

  18. A putative 3-hydroxyisobutyryl-CoA hydrolase is required for efficient symbiotic nitrogen fixation in Sinorhizobium meliloti and Sinorhizobium fredii NGR234.

    PubMed

    Zamani, Maryam; diCenzo, George C; Milunovic, Branislava; Finan, Turlough M

    2017-01-01

    We report that the smb20752 gene of the alfalfa symbiont Sinorhizobium meliloti is a novel symbiotic gene required for full N2 -fixation. Deletion of smb20752 resulted in lower nitrogenase activity and smaller nodules without impacting overall nodule morphology. Orthologs of smb20752 were present in all alpha and beta rhizobia, including the ngr_b20860 gene of Sinorhizobium fredii NGR234. A ngr_b20860 mutant formed Fix(-) determinate nodules that developed normally to a late stage of the symbiosis on the host plants Macroptilium atropurpureum and Vigna unguiculata. However an early symbiotic defect was evident during symbiosis with Leucaena leucocephala, producing Fix(-) indeterminate nodules. The smb20752 and ngr_b20860 genes encode putative 3-hydroxyisobutyryl-CoA (HIB-CoA) hydrolases. HIB-CoA hydrolases are required for l-valine catabolism and appear to prevent the accumulation of toxic metabolic intermediates, particularly methacrylyl-CoA. Evidence presented here and elsewhere (Curson et al., , PLoS ONE 9:e97660) demonstrated that Smb20752 and NGR_b20860 can also prevent metabolic toxicity, are required for l-valine metabolism, and play an undefined role in 3-hydroxybutyrate catabolism. We present evidence that the symbiotic defect of the HIB-CoA hydrolase mutants is independent of the inability to catabolize l-valine and suggest it relates to the toxicity resulting from metabolism of other compounds possibly related to 3-hydroxybutyric acid.

  19. The efficiency of nitrogen fixation of the model legume Medicago truncatula (Jemalong A17) is low compared to Medicago sativa.

    PubMed

    Sulieman, Saad; Schulze, Joachim

    2010-06-15

    Medicago truncatula (Gaertn.) (barrel medic) serves as a model legume in plant biology. Numerous studies have addressed molecular aspects of the biology of M. truncatula, while comparatively little is known about the efficiency of N(2) fixation at the whole plant level. The objective of the present study was to compare the efficiency of N(2) fixation of M. truncatula to the genetically closely related Medicago sativa (L.) (alfalfa). The relative growth of both species relying exclusively on N(2) fixation versus nitrate nutrition, H(2) evolution, nitrogen assimilation, the concentration of amino acids and organic acids in nodules, and (15)N(2) uptake and distribution were studied. M. truncatula showed much lower efficiency of N(2) fixation. Nodule-specific activity was several-fold lower when compared to M. sativa, partially as a result of a lower electron allocation to N(2) versus H(+). M. truncatula or M. sativa plants grown solely on N(2) fixation as a nitrogen source reached about 30% or 80% of growth, respectively, when compared to plants supplied with sufficient nitrate. Moreover, M. truncatula had low %N in shoots and a lower allocation of (15)N to shoots during 1h (15)N(2) labeling period. Amino acid concentration was about 20% higher in M. sativa nodules, largely as a result of more asparagine, while the organic acid concentration was about double in M. sativa, coinciding with a six-fold higher concentration of malate. Total soluble protein in nodules was about three times lower in M. truncatula and the pattern of enzyme activity in that fraction was strongly different. Sucrose cleaving enzymes displayed higher activity in M. truncatula nodules, while the activity of phosphoenolpyruvate carboxylase (PEPC) was much lower. It is concluded that the low efficiency of the M. truncatula symbiotic system is related to a low capacity of organic acid formation and limited nitrogen export from nodules.

  20. Soil nutrients, land use history and species composition interact to influence tropical N2 fixation

    NASA Astrophysics Data System (ADS)

    Batterman, S. A.; Hall, J.; Van Breugel, M.; Hedin, L. O.

    2011-12-01

    Symbiotic di-nitrogen fixation plays an important role in terrestrial biogeochemical cycles as it can bring in large quantities of nitrogen into ecosystems and provide the nitrogen required for individual plant growth in nitrogen limited environments. Of particular interest is how fixation interacts with nitrogen and phosphorus cycles in heterogeneous tropical forests. Recent advances on this topic using plants grown in a shadehouse show that the interaction of nitrogen and phosphorus control fixation at the level of individual plants and that plants adjust nutrient acquisition strategies with some successes at overcoming nutrient limitation on biomass growth depending on nutrient availability and the strategy employed (Batterman et al. unpublished). Exactly how these results translate to biodiverse tropical forests with heterogeneous resource availabilities and a history of land use disturbances, however, remains largely unresolved. We surveyed fixation across a chronosequence of forest stands in Panama that were at various stages of recovery from the abandonment of cattle pasture. Stands ranged in age from new secondary regrowth to mature forest. We examined nine common species of putative N2 fixing trees and lianas for nodulation, tree size, and abundance for four stands each of four forest ages to determine if species differ in strategies and function. In addition, we measured light availability to each tree and total and bioavailable phosphorus and nitrogen for each stand to examine the interactions of fixation with these biogeochemical cycles. Results were scaled to estimate stand level fixation. We found unique patterns in fixation that contrasted with predictions based on evidence of how fixation interacts with land use and biogeochemical cycles in extra-tropical forests. Soil nutrients showed unexpected patterns in availability across the chronosequence and interacted with fixation. Finally, species displayed distinct differences in temporal patterns in

  1. Contrasted geographical distribution of N2 fixation rates and nifH phylotypes in the Coral and Solomon Seas (southwestern Pacific) during austral winter conditions

    NASA Astrophysics Data System (ADS)

    Bonnet, Sophie; Rodier, Martine; Turk-Kubo, Kendra A.; Germineaud, Cyril; Menkes, Christophe; Ganachaud, Alexandre; Cravatte, Sophie; Raimbault, Patrick; Campbell, Ellen; Quéroué, Fabien; Sarthou, Géraldine; Desnues, Anne; Maes, Christophe; Eldin, Gerard

    2015-11-01

    Biological dinitrogen (N2) fixation and the distribution of diazotrophic phylotypes were investigated during two cruises in the Coral Sea and the Solomon Sea (southwestern Pacific) during austral winter conditions. N2 fixation rates were measurable at every station, but integrated (0-150 m) rates were an order of magnitude higher in the Solomon Sea (30 to 5449 µmol N m-2 d-1) compared to those measured in the Coral Sea (2 to 109 µmol N m-2 d-1). Rates measured in the Solomon Sea were in the upper range (100-1000 µmol N m-2 d-1) or higher than rates compiled in the global MARine Ecosystem biomass DATa database, indicating that this region has some of the highest N2 fixation rates reported in the global ocean. While unicellular diazotrophic cyanobacteria from group A (UCYN-A1 and UCYN-A2) and the proteobacteria γ-24774A11 dominated in the Coral Sea and were correlated with N2 fixation rates (p < 0.05), Trichodesmium and UCYN-B dominated in the Solomon Sea and were correlated (p < 0.05) with N2 fixation rates. UCYN-A were totally absent in the Solomon Sea. The biogeographical distribution of diazotrophs is discussed within the context of patterns in measured environmental parameters.

  2. Pesticide side effect on the symbiotic efficiency and nitrogenase activity of Rhizobiaceae bacteria family.

    PubMed

    Niewiadomska, Alicja; Klama, Justyna

    2005-01-01

    The laboratory experiments tested the influence of selected pesticides on the symbiotic efficiency and nitrogenase activity of Rhizobium leguminosarumin bv. trifolii KGL, Sinorhizobiuni melilotii Bp and Badyrhizobium sp. Ornithopus B bacteria entering into symbiosis with clover, lucerne and serradella, respectively. The results obtained indicate that the pesticides used in the experiments (Funaben T seed dressing and Pivot 100SL herbicide) caused reduced nitrogenase activity in active strains tested. In addition, a toxic effect of the applied pesticides on the nodulation and root growth of the tested plants was observed.

  3. The Endophytic Fungus Phomopsis liquidambari Increases Nodulation and N2 Fixation in Arachis hypogaea by Enhancing Hydrogen Peroxide and Nitric Oxide Signalling.

    PubMed

    Xie, Xing-Guang; Fu, Wan-Qiu; Zhang, Feng-Min; Shi, Xiao-Min; Zeng, Ying-Ting; Li, Hui; Zhang, Wei; Dai, Chuan-Chao

    2017-08-01

    The continuous cropping obstacles in monoculture fields are a major production constraint for peanuts. Application of the endophytic fungus Phomopsis liquidambari has increased peanut yields, and nodulation and N2 fixation increases have been considered as important factors for P. liquidambari infection-improved peanut yield. However, the mechanisms involved in this process remain unknown. This work showed that compared with only Bradyrhizobium inoculation, co-inoculation with P. liquidambari significantly elevated endogenous H2O2 and NO levels in peanut roots. Pre-treatment of seedlings with specific scavengers of H2O2 (CAT) and NO (cPTIO) blocked P. liquidambari-induced nodulation and N2 fixation. CAT not only suppressed the P. liquidambari-induced nodulation and N2 fixation, but also suppressed the enhanced H2O2 and NO generation. Nevertheless, the cPTIO did not significantly inhibit the induced H2O2 biosynthesis, implying that H2O2 acted upstream of NO production. These results were confirmed by observations that exogenous H2O2 and sodium nitroprusside (SNP) reversed the inhibition of P. liquidambari-increased nodulation and N2 fixation by the specific scavengers. The transcriptional activities of the symbiosis-related genes SymRK and CCaMK of peanut-Bradyrhizobium interactions also increased significantly in response to P. liquidambari, H2O2 and SNP treatments. The pot experiment further confirmed that the P. liquidambari infection-enhanced H2O2 and NO signalling pathways were significantly related to the increase in peanut nodulation and N2 fixation. This is the first report that endophytic fungus P. liquidambari can increase peanut-Bradyrhizobium interactions via enhanced H2O2/NO-dependent signalling crosstalk, which is conducive to the alleviation of continuous cropping obstacles via an increase in nodulation and N2 fixation.

  4. Elevated CO2 concentration around alfalfa nodules increases N2 fixation.

    PubMed

    Fischinger, Stephanie A; Hristozkova, Marieta; Mainassara, Zaman-Allah; Schulze, Joachim

    2010-01-01

    Nodule CO2 fixation via PEPC provides malate for bacteroids and oxaloacetate for N assimilation. The process is therefore of central importance for efficient nitrogen fixation. Nodule CO2 fixation is known to depend on external CO2 concentration. The hypothesis of the present paper was that nitrogen fixation in alfalfa plants is enhanced when the nodules are exposed to elevated CO2 concentrations. Therefore nodulated plants of alfalfa were grown in a hydroponic system that allowed separate aeration of the root/nodule compartment that avoided any gas leakage to the shoots. The root/nodule compartments were aerated either with a 2500 microl l(-1) (+CO2) or zero microl l(-1) (-CO2) CO2-containing N2/O2 gas flow (80/20, v/v). Nodule CO2 fixation, nitrogen fixation, and growth were strongly increased in the +CO2 treatment in a 3-week experimental period. More intensive CO2 and nitrogen fixation coincided with higher per plant amounts of amino acids and organic acids in the nodules. Moreover, the concentration of asparagine was increased in both the nodules and the xylem sap. Plants in the +CO2 treatment tended to develop nodules with higher %N concentration and individual activity. In a parallel experiment on plants with inefficient nodules (fix-) the +CO2 treatment remained without effect. Our data support the thesis that nodule CO2 fixation is pivotal for efficient nitrogen fixation. It is concluded that strategies which enhance nodule CO2 fixation will improve nitrogen fixation and nodule formation. Moreover, sufficient CO2 application to roots and nodules is necessary for growth and efficient nitrogen fixation in hydroponic and aeroponic growth systems.

  5. Free-air CO2 enrichment (FACE) reduces the inhibitory effect of soil nitrate on N2 fixation of Pisum sativum.

    PubMed

    Butterly, Clayton R; Armstrong, Roger; Chen, Deli; Tang, Caixian

    2016-01-01

    Additional carbohydrate supply resulting from enhanced photosynthesis under predicted future elevated CO2 is likely to increase symbiotic nitrogen (N) fixation in legumes. This study examined the interactive effects of atmospheric CO2 and nitrate (NO3(-)) concentration on the growth, nodulation and N fixation of field pea (Pisum sativum) in a semi-arid cropping system. Field pea was grown for 15 weeks in a Vertosol containing 5, 25, 50 or 90 mg NO3(-)-N kg(-1) under either ambient CO2 (aCO2; 390 ppm) or elevated CO2 (eCO2; 550 ppm) using free-air CO2 enrichment (SoilFACE). Under aCO2, field pea biomass was significantly lower at 5 mg NO3(-)-N kg(-1) than at 90 mg NO3(-)-N kg(-1) soil. However, increasing the soil N level significantly reduced nodulation of lateral roots but not the primary root, and nodules were significantly smaller, with 85% less nodule mass in the 90 NO3(-)-N kg(-1) than in the 5 mg NO3(-)-N kg(-1) treatment, highlighting the inhibitory effects of NO3(-). Field pea grown under eCO2 had greater biomass (approx. 30%) than those grown under aCO2, and was not affected by N level. Overall, the inhibitory effects of NO3(-) on nodulation and nodule mass appeared to be reduced under eCO2 compared with aCO2, although the effects of CO2 on root growth were not significant. Elevated CO2 alleviated the inhibitory effect of soil NO3(-) on nodulation and N2 fixation and is likely to lead to greater total N content of field pea growing under future elevated CO2 environments. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  6. Revisiting N2 fixation in the North Atlantic Ocean: Significance of deviations from the Redfield Ratio, atmospheric deposition and climate variability

    NASA Astrophysics Data System (ADS)

    Singh, Arvind; Lomas, M. W.; Bates, N. R.

    2013-09-01

    The average oceanic nitrate-to-phosphate molar ratio (NO3-:PO43-≈16:1, referred to as the Redfield Ratio) in subsurface waters, which is similar to the average ratio of particulate nitrogen (N)-to-phosphorus (P) in phytoplankton, is the cornerstone in calculating geochemical estimates of N2 fixation and denitrification rates. Any deviations from this canonical Redfield Ratio in intermediate ocean waters, expressed as N* (a measure of NO3- in excess or deficit of 16×PO43-), provides an integrated estimate of net N fluxes into and out of the ocean. In well-oxygenated ocean basins such as the North Atlantic Ocean, N* estimates are usually positive and can be used to infer that rates of N2 fixation exceed rates of denitrification. We use this approach to estimate N2 fixation over the last two decades (1988-2009) based on data collected at the Bermuda Atlantic Time-series Study (BATS) site in the North Atlantic Ocean near Bermuda. Our results indicate that interpretation of the N* tracer as an estimate of N2 fixation should be undertaken with caution, as N2 fixation is not the only process that results in a positive N* estimate. The impacts of a locally variable nitrogen-to-phosphorus ratio, relative to the fixed Redfield Ratio, in the suspended particulate matter as well as in the subsurface water nutrients and atmospheric N deposition on N* variability were examined. Furthermore, we explored the role of climate modes (i.e., North Atlantic Oscillation and Arctic Oscillation) on N* variability. We found that N* in the subsurface waters was significantly affected by these factors and hence previous estimates of N2 fixation using this technique might have been substantially overestimated. Our revised estimate of N2 fixation in the North Atlantic Ocean (0°N-50°N, 20°W-80°W) is 12.2±0.9×1011 mol N yr-1, and based on long-term BATS data provides better constraints than both earlier indirect and direct estimates N2 fixation.

  7. Potential Trace Metal Co-Limitation Controls on N2 Fixation and [Formula: see text] Uptake in Lakes with Varying Trophic Status.

    PubMed

    Romero, I C; Klein, N J; Sañudo-Wilhelmy, S A; Capone, D G

    2013-01-01

    The response of N2 fixation and [Formula: see text] uptake to environmental conditions and nutrient enrichment experiments in three western U.S. lake systems was studied (eutrophic Clear Lake; mesotrophic Walker Lake; oligotrophic Lake Tahoe). We tested the effect of additions of bioactive trace metals molybdenum as Mo(V) and iron (Fe) as well as phosphate (P), N2 fixation, [Formula: see text], carbon (C) fixation, chlorophyll a (Chla), and bacterial cell counts under both natural conditions and in mesocosm experiments. We found distinct background N2 fixation and [Formula: see text] uptake rates: highest at Clear Lake (N2 fixation: 44.7 ± 1.8 nmol N L(-1) h(-1)), intermediate at Walker Lake (N2 fixation: 1.7 ± 1.1 nmol N L(-1) h(-1); [Formula: see text] uptake: 113 ± 37 nmol N L(-1) h(-1)), and lowest at Lake Tahoe (N2 fixation: 0.1 ± 0.07 nmol N L(-1) h(-1); [Formula: see text] uptake: 37.2 ± 10.0 nmol N L(-1) h(-1)). N2 fixation was stimulated above control values with the addition of Fe and Pin Clear Lake (up to 50 and 63%, respectively); with Mo(V), Fe, and P in Walker Lake (up to 121, 990, and 85%, respectively); and with Mo(V) and P in Lake Tahoe (up to 475 and 21%, respectively). [Formula: see text] uptake showed the highest stimulation in Lake Tahoe during September 2010, with the addition of P and Mo(V) (∼84% for both). High responses to Mo(V) additions were also observed at some sites for C fixation (Lake Tahoe: 141%), Chla (Walker Lake: 54% and Clear Lake: 102%), and bacterial cell counts (Lake Tahoe: 61%). Overall our results suggest that co-limitation of nutrients is probably a common feature in lakes, and that some trace metals may play a crucial role in limiting N2 fixation and [Formula: see text] uptake activity, though primarily in non-eutrophic lakes.

  8. Symbiotic Efficiency of Native Rhizobia Nodulating Common Bean (Phaseolus vulgaris L.) in Soils of Western Kenya

    PubMed Central

    Kawaka, Fanuel; Dida, Mathews M.; Opala, Peter A.; Ombori, Omwoyo; Maingi, John; Osoro, Newton; Muthini, Morris; Amoding, Alice; Mukaminega, Dative; Muoma, John

    2014-01-01

    This study was conducted to determine the abundance and symbiotic efficiency of native rhizobia nodulating common bean in Kisumu and Kakamega, Kenya. Soil sampling was carried out in three farms that had been used for growing common bean for at least two seasons and one fallow land with no known history of growing common bean or inoculation. Abundance of soil rhizobia and symbiotic efficiency (SE) were determined in a greenhouse experiment. Native rhizobia populations ranged from 3.2 × 101 to 3.5 × 104 cells per gram of soil. Pure bacterial cultures isolated from fresh and healthy root nodules exhibited typical characteristics of Rhizobium sp. on yeast extract mannitol agar media supplemented with Congo red. Bean inoculation with the isolates significantly (p < 0.05) increased the shoot dry weight and nitrogen (N) concentration and content. The SE of all the native rhizobia were higher when compared to a reference strain, CIAT 899 (67%), and ranged from 74% to 170%. Four isolates had SE above a second reference strain, Strain 446 (110%). Our results demonstrate the presence of native rhizobia that are potentially superior to the commercial inoculants. These can be exploited to enhance bean inoculation programmes in the region. PMID:27355005

  9. Comparing Symbiotic Efficiency between Swollen versus Nonswollen Rhizobial Bacteroids1[C][W][OA

    PubMed Central

    Oono, Ryoko; Denison, R. Ford

    2010-01-01

    Symbiotic rhizobia differentiate physiologically and morphologically into nitrogen-fixing bacteroids inside legume host nodules. The differentiation is apparently terminal in some legume species, such as peas (Pisum sativum) and peanuts (Arachis hypogaea), likely due to extreme cell swelling induced by the host. In other legume species, such as beans (Phaseolus vulgaris) and cowpeas (Vigna unguiculata), differentiation into bacteroids, which are similar in size and shape to free-living rhizobia, is reversible. Bacteroid modification by plants may affect the effectiveness of the symbiosis. Here, we compare symbiotic efficiency of rhizobia in two different hosts where the rhizobia differentiate into swollen nonreproductive bacteroids in one host and remain nonswollen and reproductive in the other. Two such dual-host strains were tested: Rhizobium leguminosarum A34 in peas and beans and Bradyrhizobium sp. 32H1 in peanuts and cowpeas. In both comparisons, swollen bacteroids conferred more net host benefit by two measures: return on nodule construction cost (plant growth per gram nodule growth) and nitrogen fixation efficiency (H2 production by nitrogenase per CO2 respired). Terminal bacteroid differentiation among legume species has evolved independently multiple times, perhaps due to the increased host fitness benefits observed in this study. PMID:20837702

  10. Symbiotic Efficiency of Native Rhizobia Nodulating Common Bean (Phaseolus vulgaris L.) in Soils of Western Kenya.

    PubMed

    Kawaka, Fanuel; Dida, Mathews M; Opala, Peter A; Ombori, Omwoyo; Maingi, John; Osoro, Newton; Muthini, Morris; Amoding, Alice; Mukaminega, Dative; Muoma, John

    2014-01-01

    This study was conducted to determine the abundance and symbiotic efficiency of native rhizobia nodulating common bean in Kisumu and Kakamega, Kenya. Soil sampling was carried out in three farms that had been used for growing common bean for at least two seasons and one fallow land with no known history of growing common bean or inoculation. Abundance of soil rhizobia and symbiotic efficiency (SE) were determined in a greenhouse experiment. Native rhizobia populations ranged from 3.2 × 10(1) to 3.5 × 10(4) cells per gram of soil. Pure bacterial cultures isolated from fresh and healthy root nodules exhibited typical characteristics of Rhizobium sp. on yeast extract mannitol agar media supplemented with Congo red. Bean inoculation with the isolates significantly (p < 0.05) increased the shoot dry weight and nitrogen (N) concentration and content. The SE of all the native rhizobia were higher when compared to a reference strain, CIAT 899 (67%), and ranged from 74% to 170%. Four isolates had SE above a second reference strain, Strain 446 (110%). Our results demonstrate the presence of native rhizobia that are potentially superior to the commercial inoculants. These can be exploited to enhance bean inoculation programmes in the region.

  11. The impact of simulated chronic nitrogen deposition on the biomass and N2-fixation activity of two boreal feather moss–cyanobacteria associations

    PubMed Central

    Gundale, Michael J.; Bach, Lisbet H.; Nordin, Annika

    2013-01-01

    Bryophytes achieve substantial biomass and play several key functional roles in boreal forests that can influence how carbon (C) and nitrogen (N) cycling respond to atmospheric deposition of reactive nitrogen (Nr). They associate with cyanobacteria that fix atmospheric N2, and downregulation of this process may offset anthropogenic Nr inputs to boreal systems. Bryophytes also promote soil C accumulation by thermally insulating soils, and changes in their biomass influence soil C dynamics. Using a unique large-scale (0.1 ha forested plots), long-term experiment (16 years) in northern Sweden where we simulated anthropogenic Nr deposition, we measured the biomass and N2-fixation response of two bryophyte species, the feather mosses Hylocomium splendens and Pleurozium schreberi. Our data show that the biomass declined for both species; however, N2-fixation rates per unit mass and per unit area declined only for H. splendens. The low and high treatments resulted in a 29% and 54% reduction in total feather moss biomass, and a 58% and 97% reduction in total N2-fixation rate per unit area, respectively. These results help to quantify the sensitivity of feather moss biomass and N2 fixation to chronic Nr deposition, which is relevant for modelling ecosystem C and N balances in boreal ecosystems. PMID:24196519

  12. Root-Associated N2 Fixation (Acetylene Reduction) by Enterobacteriaceae and Azospirillum Strains in Cold-Climate Spodosols

    PubMed Central

    Haahtela, Kielo; Wartiovaara, Tuula; Sundman, Veronica; Skujiņš, J.

    1981-01-01

    N2 fixation by bacteria in associative symbiosis with washed roots of 13 Poaceae and 8 other noncultivated plant species in Finland was demonstrated by the acetylene reduction method. The roots most active in C2H2 reduction were those of Agrostis stolonifera, Calamagrostis lanceolata, Elytrigia repens, and Phalaris arundinacea, which produced 538 to 1,510 nmol of C2H4·g−1 (dry weight)· h−1 when incubated at pO2 0.04 with sucrose (pH 6.5), and 70 to 269 nmol of C2H4· g−1 (dry weight)·h−1 without an added energy source and unbuffered. Azospirillum lipferum, Enterobacter agglomerans, Klebsiella pneumoniae, and a Pseudomonas sp. were the acetylene-reducing organisms isolated. The results demonstrate the presence of N2-fixing organisms in associative symbiosis with plant roots found in a northern climatic region in acidic soils ranging down to pH 4.0. PMID:16345687

  13. Cyanobacterial lactate oxidases serve as essential partners in N2 fixation and evolved into photorespiratory glycolate oxidases in plants.

    PubMed

    Hackenberg, Claudia; Kern, Ramona; Hüge, Jan; Stal, Lucas J; Tsuji, Yoshinori; Kopka, Joachim; Shiraiwa, Yoshihiro; Bauwe, Hermann; Hagemann, Martin

    2011-08-01

    Glycolate oxidase (GOX) is an essential enzyme involved in photorespiratory metabolism in plants. In cyanobacteria and green algae, the corresponding reaction is catalyzed by glycolate dehydrogenases (GlcD). The genomes of N(2)-fixing cyanobacteria, such as Nostoc PCC 7120 and green algae, appear to harbor genes for both GlcD and GOX proteins. The GOX-like proteins from Nostoc (No-LOX) and from Chlamydomonas reinhardtii showed high L-lactate oxidase (LOX) and low GOX activities, whereas glycolate was the preferred substrate of the phylogenetically related At-GOX2 from Arabidopsis thaliana. Changing the active site of No-LOX to that of At-GOX2 by site-specific mutagenesis reversed the LOX/GOX activity ratio of No-LOX. Despite its low GOX activity, No-LOX overexpression decreased the accumulation of toxic glycolate in a cyanobacterial photorespiratory mutant and restored its ability to grow in air. A LOX-deficient Nostoc mutant grew normally in nitrate-containing medium but died under N(2)-fixing conditions. Cultivation under low oxygen rescued this lethal phenotype, indicating that N(2) fixation was more sensitive to O(2) in the Δlox Nostoc mutant than in the wild type. We propose that LOX primarily serves as an O(2)-scavenging enzyme to protect nitrogenase in extant N(2)-fixing cyanobacteria, whereas in plants it has evolved into GOX, responsible for glycolate oxidation during photorespiration.

  14. Heterotrophic 15N2 Fixation and Distribution of Newly Fixed Nitrogen in a Rice-Flooded Soil System 1

    PubMed Central

    Eskew, David L.; Eaglesham, Allan R. J.; App, A. A.

    1981-01-01

    Rice (Oryza sativa L.) plants growing in pots of flooded soil were exposed to a 15N2-enriched atmosphere for 3 to 13 days in a gas-tight chamber. The floodwater and soil surface were shaded with a black cloth to reduce the activity of phototrophic N2-fixing micro-organisms. The highest 15N enrichments were consistently observed in the roots, although the total quantity of 15N incorporated into the soil was much greater. The rate of 15N incorporation into roots was much higher at the heading than at the tillering stage of growth. Definite enrichments were also found in the basal node and in the lower outer leaf sheath fractions after 3 days of exposure at the heading stage. Thirteen days was the shortest time period in which definite 15N enrichment was observed in the leaves and panicle. When plants were exposed to 15N2 for 13 days just before heading and then allowed to mature in a normal atmosphere, 11.3% of the total 15N in the system was found in the panicles, 2.3% in the roots, and 80.7% in the subsurface soil. These results provide direct evidence of heterotrophic N2 fixation associated with rice roots and the flooded soil and demonstrate that part of the newly fixed N is available to the plant. PMID:16661887

  15. N2 Fixation, Carbon Metabolism, and Oxidative Damage in Nodules of Dark-Stressed Common Bean Plants.

    PubMed Central

    Gogorcena, Y.; Gordon, A. J.; Escuredo, P. R.; Minchin, F. R.; Witty, J. F.; Moran, J. F.; Becana, M.

    1997-01-01

    Common beans (Phaseolus vulgaris L.) were exposed to continuous darkness to induce nodule senescence, and several nodule parameters were investigated to identify factors that may be involved in the initial loss of N2 fixation. After only 1 d of darkness, total root respiration decreased by 76% and in vivo nitrogenase (N2ase) activity decreased by 95%. This decline coincided with the almost complete depletion (97%) of sucrose and fructose in nodules. At this stage, the O2 concentration in the infected zone increased to 1%, which may be sufficient to inactivate N2ase; however, key enzymes of carbon and nitrogen metabolism were still active. After 2 d of dark stress there was a significant decrease in the level of N2ase proteins and in the activities of enzymes involved in carbon and nitrogen assimilation. However, the general collapse of nodule metabolism occurred only after 4 d of stress, with a large decline in leghemoglobin and antioxidants. At this final senescent stage, there was an accumulation of oxidatively modified proteins. This oxidative stress may have originated from the decrease in antioxidant defenses and from the Fe-catalyzed generation of activated oxygen due to the increased availability of catalytic Fe and O2 in the infected region. PMID:12223669

  16. Biological N2-fixation in Boreal Peatlands of Alberta Canada Following Acute N-Deposition: Down-Regulation and Subsequent Post-Recovery Projections.

    NASA Astrophysics Data System (ADS)

    Vile, M. A.; Fillingim, H.

    2015-12-01

    Globally, boreal peatlands cover a mere 3-4 % of the Earth's land surface, yet store ~ 30% of the world's soil carbon and ~9-16% of global soil nitrogen. Biological N2-fixation is the primary input of new nitrogen (N) to bogs in Alberta. We have demonstrated that this process is down regulated in the presence of enhanced atmospheric N deposition such as that from the growing Oil Sands Mining Operations in northern Alberta Canada. An important question for understanding the long term function of bogs in Alberta is whether N2-fixation can recover upon cessation of N pollution, and if so, how quickly? Here we present our preliminary findings in pursuit of this question. We measured rates of biological N2-fixation using the acetylene reduction assay (ARA), with subsequent calibration using 15N2 on separate, but paired incubations. Sphagnum fuscum from bogs at two different sites from northern Alberta were incubated over the course of 3 years, in 3 experimentally added treatments in the field; controls, plots receiving no added N and no water, water only treatments (no added N), and plots that were fertilized with N at a rate of 20 kg·ha-1·yr-1, and plots which had been fertilized with 20 kg·ha-1·yr-1in 2012-2013, but not since. In 2014, the rates of N2-fixation in the 20 kg·ha-1·yr-1plots and the recovering 20 kg·ha-1·yr-1plots were not significantly different, but both were significantly lower than the controls (p<0.05). In 2015, control plots had significantly higher rates of N2-fixation than the plots that had previously received 20 kg·ha-1·yr-1 in 2012 and 2013, and the plots that had not received 20 kg·ha-1·yr-1 since 2013 had significantly higher rates of biological N2-fixation. These data suggest that in a low atmospheric N deposition scenario, and over a short time frame, peatlands of northern Alberta may be able to recover from chronic atmospheric N deposition.

  17. Trophic cascades in the bryosphere: the impact of global change factors on top-down control of cyanobacterial N2 -fixation.

    PubMed

    Kardol, Paul; Spitzer, Clydecia M; Gundale, Michael J; Nilsson, Marie-Charlotte; Wardle, David A

    2016-08-01

    Trophic cascades in which predators regulate densities of organisms at lower trophic levels are important drivers of population dynamics, but effects of trophic cascades on ecosystem-level fluxes and processes, and the conditions under which top-down control is important, remain unresolved. We manipulated the structure of a food web in boreal feather mosses and found that moss-inhabiting microfauna exerted top-down control of N2 -fixation by moss-associated cyanobacteria. However, the presence of higher trophic levels alleviated this top-down control, likely through feeding on bacterivorous microfauna. These effects of food-web structure on cyanobacterial N2 -fixation were dependent on global change factors and strongly suppressed under N fertilisation. Our findings illustrate how food web interactions and trophic cascades can regulate N cycling in boreal ecosystems, where carbon uptake is generally strongly N-limited, and shifting trophic control of N cycling under global change is therefore likely to impact ecosystem functioning.

  18. Importance of N2-Fixation on the Productivity at the North-Western Azores Current/Front System, and the Abundance of Diazotrophic Unicellular Cyanobacteria

    PubMed Central

    Riou, Virginie; Fonseca-Batista, Debany; Roukaerts, Arnout; Biegala, Isabelle C.; Prakya, Shree Ram; Magalhães Loureiro, Clara; Santos, Mariana; Muniz-Piniella, Angel E.; Schmiing, Mara; Elskens, Marc; Brion, Natacha; Martins, M. Ana; Dehairs, Frank

    2016-01-01

    To understand the impact of the northwestern Azores Current Front (NW-AzC/AzF) system on HCO3−-and N2-fixation activities and unicellular diazotrophic cyanobacteria (UCYN) distribution, we combined geochemical and biological approaches from the oligotrophic surface to upper mesopelagic waters. N2-fixation was observed to sustain 45–85% of the HCO3−-fixation in the picoplanktonic fraction performing 47% of the total C-fixation at the deep chlorophyll maximum north and south of the AzF. N2-fixation rates as high as 10.9 μmol N m-3 d-1 and surface nitrate δ15N as low as 2.7‰ were found in the warm (18–24°C), most saline (36.5–37.0) and least productive waters south of the AzF, where UCYN were the least abundant. However, picoplanktonic UCYN abundances up to 55 cells mL-1 were found at 45–200m depths in the coolest nutrient-rich waters north of the AzF. In this area, N2-fixation rates up to 4.5 μmol N m-3 d-1 were detected, associated with depth-integrated H13CO3−-fixation rates at least 50% higher than observed south of the AzF. The numerous eddies generated at the NW-AzC/AzF seem to enhance exchanges of plankton between water masses, as well as vertical and horizontal diapycnal diffusion of nutrients, whose increase probably enhances the growth of diazotrophs and the productivity of C-fixers. PMID:26958844

  19. Importance of N2-Fixation on the Productivity at the North-Western Azores Current/Front System, and the Abundance of Diazotrophic Unicellular Cyanobacteria.

    PubMed

    Riou, Virginie; Fonseca-Batista, Debany; Roukaerts, Arnout; Biegala, Isabelle C; Prakya, Shree Ram; Magalhães Loureiro, Clara; Santos, Mariana; Muniz-Piniella, Angel E; Schmiing, Mara; Elskens, Marc; Brion, Natacha; Martins, M Ana; Dehairs, Frank

    2016-01-01

    To understand the impact of the northwestern Azores Current Front (NW-AzC/AzF) system on HCO3--and N2-fixation activities and unicellular diazotrophic cyanobacteria (UCYN) distribution, we combined geochemical and biological approaches from the oligotrophic surface to upper mesopelagic waters. N2-fixation was observed to sustain 45-85% of the HCO3--fixation in the picoplanktonic fraction performing 47% of the total C-fixation at the deep chlorophyll maximum north and south of the AzF. N2-fixation rates as high as 10.9 μmol N m-3 d-1 and surface nitrate δ15N as low as 2.7‰ were found in the warm (18-24°C), most saline (36.5-37.0) and least productive waters south of the AzF, where UCYN were the least abundant. However, picoplanktonic UCYN abundances up to 55 cells mL-1 were found at 45-200m depths in the coolest nutrient-rich waters north of the AzF. In this area, N2-fixation rates up to 4.5 μmol N m-3 d-1 were detected, associated with depth-integrated H13CO3--fixation rates at least 50% higher than observed south of the AzF. The numerous eddies generated at the NW-AzC/AzF seem to enhance exchanges of plankton between water masses, as well as vertical and horizontal diapycnal diffusion of nutrients, whose increase probably enhances the growth of diazotrophs and the productivity of C-fixers.

  20. Environmental controls on N2 fixation by Trichodesmium in the tropical eastern North Atlantic Ocean-A model-based study

    NASA Astrophysics Data System (ADS)

    Ye, Ying; Völker, Christoph; Bracher, Astrid; Taylor, Bettina; Wolf-Gladrow, Dieter A.

    2012-06-01

    The low surface nitrate concentration and high atmospheric iron input in the tropical eastern North Atlantic provide beneficial conditions for N2 fixation. Varying abundances of diazotrophs have been observed and an Fe- and P-colimitation of N2 fixation was reported in this ocean region. It is however unclear, how different limiting factors control the temporal variability of N2 fixation and what the role of Fe-limitation is in a region with high fluxes of dust deposition. To study the environmental controls on N2 fixation, an one-dimensional ecosystem model is coupled with a physical model for the Tropical Eastern North Atlantic Times-series Station (TENATSO), north of the Cape Verde Islands. The model describes diazotrophy according to the physiology of Trichodesmium, taking into account a growth dependence on light, temperature, iron, dissolved inorganic (DIP) and organic phosphorus (DOP). The modelled total Chl a is compared with satellite-derived total Chl a and modelled Trichodesmium (Tri) compared with satellite-derived cyanobacterial Chl a as well as with High Performance Liquid Chromatography data. Model results show a complex pattern of competitive as well as mutually beneficial interactions between diazotrophs and non-diazotrophic phytoplankton. High DOP availability after spring blooms of non-diazotrophic phytoplankton and the ability of Trichodesmium to take up DOP are crucial for allowing a maximal abundance of Tri in autumn. Part of the reactive nitrogen newly fixed by diazotrophs is directly excreted or released through mortality, significantly fuelling the growth of non-diazotrophic phytoplankton in autumn and winter. Fe consumption by non-diazotrophic phytoplankton earlier in the year makes Fe limitation of Tri in late summer more acute, whereas Tri growth in surface waters reduces phytoplankton abundance deeper in the water column by light limitation. Overall, the atmospheric iron input at the TENATSO site is required to enable diazotrophic

  1. The Effect of NaCl on growth, N2 fixation (acetylene reduction), and percentage total nitrogen in Leucaena leucocephala (Leguminosae) var. K-8.

    PubMed

    Anthraper, Annie; Dubois, John D

    2003-05-01

    Leucaena leucocephala var. K-8 is a fast-growing, tropical leguminous tree that has multiple economic uses. This study was conducted to evaluate the effect(s) of varying NaCl concentrations on growth, N(2) fixation, and percentage of total tissue nitrogen in different organs in L. leucocephala. Seeds were germinated and grown for 10 wk with a nitrogen-free fertilizer applied every 2 wk. At 10 wk, plants were treated for either 0, 7, 14, 21, or 28 wk with either deionized water (control), 0.00625 mol/L, 0.0125 mol/L, 0.025 mol/L, 0.05 mol/L, or 0.1 mol/L NaCl in addition to the fertilizer every 2 wk. Growth was measured as plant height, nodule number and mass, and dry tissue mass. N(2) fixation was measured by the acetylene reduction assay. Percentage of tissue nitrogen was determined using Kjeldahl analysis. In younger plants (7-wk treatment), major fluctuations in NaCl tolerance were observed in the different plant organs. As plants matured (14- and 21-wk treatment) NaCl concentrations of 0.025 mol/L and higher caused the greatest reduction in growth and tissue nitrogen. We conclude that NaCl concentrations of 0.025 mol/L and greater caused a major decrease in growth, N(2) fixation, and percentage of tissue nitrogen in L. leucocephala plants that were less than 1 yr old.

  2. Estimates of N2 Fixation Based on Differences in the Natural Abundance of 15N in Nodulating and Nonnodulating Isolines of Soybeans 1

    PubMed Central

    Kohl, Daniel H.; Shearer, Georgia; Harper, James E.

    1980-01-01

    Estimates of the contribution of biologically fixed N to the total N of nodulating soybeans (Glycine max (L) Merrill, variety Harosoy) grown under a variety of conditions were made from: (a) differences in N yield between nodulating and nonnodulating isolines; and (b) differences in 15N abundance between the two isolines. For plants grown in a greenhouse in nutrient-poor soil, both estimates showed a high level of N2 fixation; from 58 to 89% N fixed by differences in N yield and from 51 to 95% by differences in 15N abundance. Decreasing contributions of fixed N were estimated by both methods with increasing levels of added NO3−. Results of field experiments carried out over two years on an unamended highly fertile midwestern soil showed a modest level of N2 fixation by both methods (7.3 to 51% by differences in N yield, and 5.4 to 46% by differences in 15N abundance). When the soil was amended with ground corn cobs, both methods showed higher contributions of fixed N. The two methods of estimating N2 fixation gave similar results. Both appear to be semiquantitative and the standard errors of the estimates were about the same (6% on the average). PMID:16661394

  3. Flavone Limitations to Root Nodulation and Symbiotic Nitrogen Fixation in Alfalfa 1

    PubMed Central

    Kapulnik, Yoram; Joseph, Cecillia M.; Phillips, Donald A.

    1987-01-01

    Transcription of the nodABC genes in Rhizobium meliloti is required for root nodule formation in alfalfa (Medicago sativa L.) and occurs when specific compounds, such as the flavone luteolin, are supplied by the host plant. Results reported here indicate how luteolin in the root and rhizosphere can affect subsequent N2 fixation and plant growth. Previous experiments with `Hairy Peruvian 32' (HP32), an alfalfa population produced from `Hairy Peruvian' (HP) by two generations of selection for increased N2 fixation and growth, found that HP32 had more root nodules and fixed more N2 than the parental HP population. In the present study, flavonoid extracts of HP32 seedling roots are shown to contain a 60% higher concentration of compounds that induce transcription of a nodABC-lacZ fusion in R. meliloti than comparable extracts of HP roots. Chromatographic data indicated that HP32 roots had a 77% higher concentration of luteolin than HP roots. Adding 10 micromolar luteolin to the rhizosphere of HP seedlings increased nodulation, N2 fixation, total N, and total dry weight but had no effect on nitrate assimilation. These data show that normal levels of flavone nodulation signals in the rhizosphere of HP alfalfa can limit root nodulation, symbiotic N2 fixation, and seedling growth and suggest that one mechanism for increasing N2 fixation can be the genetic enhancement of specific biochemical signals which induce nodulation genes in Rhizobium. PMID:16665583

  4. Efficient Inactivation of Symbiotic Nitrogen Fixation Related Genes in Lotus japonicus Using CRISPR-Cas9

    PubMed Central

    Wang, Longxiang; Wang, Longlong; Tan, Qian; Fan, Qiuling; Zhu, Hui; Hong, Zonglie; Zhang, Zhongming; Duanmu, Deqiang

    2016-01-01

    The targeted genome editing technique, CRISPR/Cas9 system, has been widely used to modify genes of interest in a predictable and precise manner. In this study, we describe the CRISPR/Cas9-mediated efficient editing of representative SNF (symbiotic nitrogen fixation) related genes in the model legume Lotus japonicus via Agrobacterium-mediated stable or hairy root transformation. We first predicted nine endogenous U6 genes in Lotus and then demonstrated the efficacy of the LjU6-1 gene promoter in driving expression of single guide RNAs (sgRNAs) by using a split yellow fluorescence protein (YFP) reporter system to restore the fluorescence in Arabidopsis protoplasts. Next, we chose a customized sgRNA targeting SYMRK (symbiosis receptor-like kinase) loci and achieved ~35% mutagenic efficiency in 20 T0 transgenic plants, two of them containing biallelic homozygous mutations with a 2-bp deletion near the PAM region. We further designed two sgRNAs targeting three homologous leghemoglobin loci (LjLb1, LjLb2, LjLb3) for testing the possibility of generating multi-gene knockouts. 20 out of 70 hairy root transgenic plants exhibited white nodules, with at least two LjLbs disrupted in each plant. Compared with the constitutively active CaMV 35S promoter, the nodule-specific LjLb2 promoter was also effective in gene editing in nodules by hairy root transformation. Triple mutant knockout of LjLbs was also obtained by stable transformation using two sgRNAs. Collectively, these studies demonstrate that the CRISPR/Cas9 system should greatly facilitate functional analyses of SNF related genes in Lotus japonicus. PMID:27630657

  5. Efficient Inactivation of Symbiotic Nitrogen Fixation Related Genes in Lotus japonicus Using CRISPR-Cas9.

    PubMed

    Wang, Longxiang; Wang, Longlong; Tan, Qian; Fan, Qiuling; Zhu, Hui; Hong, Zonglie; Zhang, Zhongming; Duanmu, Deqiang

    2016-01-01

    The targeted genome editing technique, CRISPR/Cas9 system, has been widely used to modify genes of interest in a predictable and precise manner. In this study, we describe the CRISPR/Cas9-mediated efficient editing of representative SNF (symbiotic nitrogen fixation) related genes in the model legume Lotus japonicus via Agrobacterium-mediated stable or hairy root transformation. We first predicted nine endogenous U6 genes in Lotus and then demonstrated the efficacy of the LjU6-1 gene promoter in driving expression of single guide RNAs (sgRNAs) by using a split yellow fluorescence protein (YFP) reporter system to restore the fluorescence in Arabidopsis protoplasts. Next, we chose a customized sgRNA targeting SYMRK (symbiosis receptor-like kinase) loci and achieved ~35% mutagenic efficiency in 20 T0 transgenic plants, two of them containing biallelic homozygous mutations with a 2-bp deletion near the PAM region. We further designed two sgRNAs targeting three homologous leghemoglobin loci (LjLb1, LjLb2, LjLb3) for testing the possibility of generating multi-gene knockouts. 20 out of 70 hairy root transgenic plants exhibited white nodules, with at least two LjLbs disrupted in each plant. Compared with the constitutively active CaMV 35S promoter, the nodule-specific LjLb2 promoter was also effective in gene editing in nodules by hairy root transformation. Triple mutant knockout of LjLbs was also obtained by stable transformation using two sgRNAs. Collectively, these studies demonstrate that the CRISPR/Cas9 system should greatly facilitate functional analyses of SNF related genes in Lotus japonicus.

  6. Biological N2-FIXATION and Mineral N-Fertilization Effects on Soybean (Glicine max L. Merr.) Yield Under Temperate Climate Conditions

    NASA Astrophysics Data System (ADS)

    László Phd, M., ,, Dr.

    2009-04-01

    continues to increase) and allewiate world hunger is to increase the intensity of production in those ecosystems that lend themselves to sustainable intensification while decreasing the intensity of production in the more fragile ecologies (Reeves 1998). Most plants depend entirely for growth on fixed nitrogen absorbed from the soil, mainly as nitrate but also as ammonium. Therefore to the methods of crop production now dominant in the agricultural systems of many developed countries strongly depend upon a sustained input of N. Economic and environmental considerations surrounding fertilizer use then empasize the need to increase the efficiency of N- utilization by plants. On the other hand the biological nitrogen fixation (BNF) is important under all imput conditions to ensure an optimal supply of nitrogen to the farming system. A well-founded understanding of the mechanistic interactions between BNF and N limitations is presently lacking. Synbiotic nitrogen fixation by legumes makes a valuable contribution to N-inputs, especially in countries like Hungary where effective rhizobia-inoculation techniques have been developed in the context of the new sustainable agricultural system. It is widely known that soya bean -Glycine max (L.) Merr.-, is an important legume. This plant able to fix the atmospheric nitrogen (N2) it needs for growth through the agency of specific bacteria Rhizobium japonicum. Under field conditions fixation usually accounts for only 25-30% of the total nitrogen accumulated by these plants at harvest. Therefore to marginal yield have to optimalise the nitrogen supply of these legume by N-fertilization. Objectives for our experiments were to (1.) comparisons of the plant nutrition performance of different soil nitrogen supply levels by N- fertilization and N- fixation under Mediterranean climate conditions at Hungary, (2.) evaluates the potential for N2 fixation imputs by grain legume based on the soya bean as a means of improving soil fertility, (3

  7. Genetic Diversity and Symbiotic Efficiency of Nodulating Rhizobia Isolated from Root Nodules of Faba Bean in One Field

    PubMed Central

    Lan, Qin; Wang, Ke; Liu, Ming; Peng, Dan; Zhang, Xiaoping; Chen, Qiang; Zhao, Ke; Zeng, Xiangzhong; Xu, Kai Wei

    2016-01-01

    Thirty-one nodulating rhizobium strains were collected from root nodules of spring and winter type faba bean cultivars grown in micro ecoarea, i.e. the same field in Chengdu plain, China. The symbiotic efficiency and phylogeny of these strains were studied. Effectively nitrogen fixing strains were isolated from both winter type and spring type cultivars. Based on phylogenetic analysis of 16S rRNA gene and concatenated sequence of atpD, glnII and recA genes, the isolates were assigned as Rhizobium anhuiense and a potential new Rhizobium species. The isolates were diverse on symbiosis related gene level, carrying five, four and three variants of nifH, nodC and nodD, respectively. Strains carrying similar gene combinations were trapped by both winter and spring cultivars, disagreeing with the specificity of symbiotic genotypes to reported earlier faba bean ecotypes. PMID:27936180

  8. High rate of N2 fixation by East Siberian cryophilic soil bacteria as determined by measuring acetylene reduction in nitrogen-poor medium solidified with gellan gum.

    PubMed

    Hara, Shintaro; Hashidoko, Yasuyuki; Desyatkin, Roman V; Hatano, Ryusuke; Tahara, Satoshi

    2009-05-01

    For evaluating N(2) fixation of diazotrophic bacteria, nitrogen-poor liquid media supplemented with at least 0.5% sugar and 0.2% agar are widely used for acetylene reduction assays. In such a soft gel medium, however, many N(2)-fixing soil bacteria generally show only trace acetylene reduction activity. Here, we report that use of a N(2) fixation medium solidified with gellan gum instead of agar promoted growth of some gellan-preferring soil bacteria. In a soft gel medium solidified with 0.3% gellan gum under appropriate culture conditions, bacterial microbiota from boreal forest bed soils and some free-living N(2)-fixing soil bacteria isolated from the microbiota exhibited 10- to 200-fold-higher acetylene reduction than those cultured in 0.2% agar medium. To determine the N(2) fixation-activating mechanism of gellan gum medium, qualitative differences in the colony-forming bacterial components from tested soil microbiota were investigated in plate cultures solidified with either agar or gellan gum for use with modified Winogradsky's medium. On 1.5% agar plates, apparently cryophilic bacterial microbiota showed strictly distinguishable microbiota according to the depth of soil in samples from an eastern Siberian Taiga forest bed. Some pure cultures of proteobacteria, such as Pseudomonas fluorescens and Burkholderia xenovorans, showed remarkable acetylene reduction. On plates solidified with 1.0% gellan gum, some soil bacteria, including Luteibacter sp., Janthinobacterium sp., Paenibacillus sp., and Arthrobacter sp., uniquely grew that had not grown in the presence of the same inoculants on agar plates. In contrast, Pseudomonas spp. and Burkholderia spp. were apparent only as minor colonies on the gellan gum plates. Moreover, only gellan gum plates allowed some bacteria, particularly those isolated from the shallow organic soil layer, to actively swarm. In consequence, gellan gum is a useful gel matrix to bring out growth potential capabilities of many soil

  9. RNA-seq transcriptome profiling reveals that Medicago truncatula nodules acclimate N2 fixation before emerging P deficiency reaches the nodules

    PubMed Central

    Cabeza, Ricardo A.; Liese, Rebecca; Lingner, Annika; von Stieglitz, Ilsabe; Neumann, Janice; Salinas-Riester, Gabriela; Pommerenke, Claudia; Dittert, Klaus; Schulze, Joachim

    2014-01-01

    Legume nodules are plant tissues with an exceptionally high concentration of phosphorus (P), which, when there is scarcity of P, is preferentially maintained there rather than being allocated to other plant organs. The hypothesis of this study was that nodules are affected before the P concentration in the organ declines during whole-plant P depletion. Nitrogen (N2) fixation and P concentration in various organs were monitored during a whole-plant P-depletion process in Medicago truncatula. Nodule gene expression was profiled through RNA-seq at day 5 of P depletion. Until that point in time P concentration in leaves reached a lower threshold but was maintained in nodules. N2-fixation activity per plant diverged from that of fully nourished plants beginning at day 5 of the P-depletion process, primarily because fewer nodules were being formed, while the activity of the existing nodules was maintained for as long as two weeks into P depletion. RNA-seq revealed nodule acclimation on a molecular level with a total of 1140 differentially expressed genes. Numerous genes for P remobilization from organic structures were increasingly expressed. Various genes involved in nodule malate formation were upregulated, while genes involved in fermentation were downregulated. The fact that nodule formation was strongly repressed with the onset of P deficiency is reflected in the differential expression of various genes involved in nodulation. It is concluded that plants follow a strategy to maintain N2 fixation and viable leaf tissue as long as possible during whole-plant P depletion to maintain their ability to react to emerging new P sources (e.g. through active P acquisition by roots). PMID:25151618

  10. Predictable and efficient carbon sequestration in the North Pacific Ocean supported by symbiotic nitrogen fixation.

    PubMed

    Karl, David M; Church, Matthew J; Dore, John E; Letelier, Ricardo M; Mahaffey, Claire

    2012-02-07

    The atmospheric and deep sea reservoirs of carbon dioxide are linked via physical, chemical, and biological processes. The last of these include photosynthesis, particle settling, and organic matter remineralization, and are collectively termed the "biological carbon pump." Herein, we present results from a 13-y (1992-2004) sediment trap experiment conducted in the permanently oligotrophic North Pacific Subtropical Gyre that document a large, rapid, and predictable summertime (July 15-August 15) pulse in particulate matter export to the deep sea (4,000 m). Peak daily fluxes of particulate matter during the summer export pulse (SEP) average 408, 283, 24.1, 1.1, and 67.5 μmol·m(-2)·d(-1) for total carbon, organic carbon, nitrogen, phosphorus (PP), and biogenic silica, respectively. The SEP is approximately threefold greater than mean wintertime particle fluxes and fuels more efficient carbon sequestration because of low remineralization during downward transit that leads to elevated total carbon/PP and organic carbon/PP particle stoichiometry (371:1 and 250:1, respectively). Our long-term observations suggest that seasonal changes in the microbial assemblage, namely, summertime increases in the biomass and productivity of symbiotic nitrogen-fixing cyanobacteria in association with diatoms, are the main cause of the prominent SEP. The recurrent SEP is enigmatic because it is focused in time despite the absence of any obvious predictable stimulus or habitat condition. We hypothesize that changes in day length (photoperiodism) may be an important environmental cue to initiate aggregation and subsequent export of organic matter to the deep sea.

  11. Predictable and efficient carbon sequestration in the North Pacific Ocean supported by symbiotic nitrogen fixation

    PubMed Central

    Karl, David M.; Church, Matthew J.; Dore, John E.; Letelier, Ricardo M.; Mahaffey, Claire

    2012-01-01

    The atmospheric and deep sea reservoirs of carbon dioxide are linked via physical, chemical, and biological processes. The last of these include photosynthesis, particle settling, and organic matter remineralization, and are collectively termed the “biological carbon pump.” Herein, we present results from a 13-y (1992–2004) sediment trap experiment conducted in the permanently oligotrophic North Pacific Subtropical Gyre that document a large, rapid, and predictable summertime (July 15–August 15) pulse in particulate matter export to the deep sea (4,000 m). Peak daily fluxes of particulate matter during the summer export pulse (SEP) average 408, 283, 24.1, 1.1, and 67.5 μmol·m−2·d−1 for total carbon, organic carbon, nitrogen, phosphorus (PP), and biogenic silica, respectively. The SEP is approximately threefold greater than mean wintertime particle fluxes and fuels more efficient carbon sequestration because of low remineralization during downward transit that leads to elevated total carbon/PP and organic carbon/PP particle stoichiometry (371:1 and 250:1, respectively). Our long-term observations suggest that seasonal changes in the microbial assemblage, namely, summertime increases in the biomass and productivity of symbiotic nitrogen-fixing cyanobacteria in association with diatoms, are the main cause of the prominent SEP. The recurrent SEP is enigmatic because it is focused in time despite the absence of any obvious predictable stimulus or habitat condition. We hypothesize that changes in day length (photoperiodism) may be an important environmental cue to initiate aggregation and subsequent export of organic matter to the deep sea. PMID:22308450

  12. Dynamics of N2 fixation and fate of diazotroph-derived nitrogen in a low nutrient low chlorophyll ecosystem: results from the VAHINE mesocosm experiment (New Caledonia)

    NASA Astrophysics Data System (ADS)

    Bonnet, S.; Berthelot, H.; Turk-Kubo, K.; Fawcett, S.; Rahav, E.; l'Helguen, S.; Berman-Frank, I.

    2015-12-01

    N2 fixation rates were measured daily in large (~ 50 m3) mesocosms deployed in the tropical South West Pacific coastal ocean (New Caledonia) to investigate the spatial and temporal dynamics of diazotrophy and the fate of diazotroph-derived nitrogen (DDN) in a low nutrient, low chlorophyll ecosystem. The mesocosms were intentionally fertilized with ~ 0.8 μM dissolved inorganic phosphorus (DIP) to stimulate diazotrophy. Bulk N2 fixation rates were replicable between the three mesocosms, averaged 18.5 ± 1.1 nmol N L-1 d-1 over the 23 days, and increased by a factor of two during the second half of the experiment (days 15 to 23) to reach 27.3 ± 1.0 nmol N L-1 d-1. These rates are higher than the upper range reported for the global ocean, indicating that the waters surrounding New Caledonia are particularly favourable for N2 fixation. During the 23 days of the experiment, N2 fixation rates were positively correlated with seawater temperature, primary production, bacterial production, standing stocks of particulate organic carbon, nitrogen and phosphorus, and alkaline phosphatase activity, and negatively correlated with DIP concentrations, DIP turnover time, nitrate, and dissolved organic nitrogen and phosphorus concentrations. The fate of DDN was investigated during the bloom of the unicellular diazotroph, UCYN-C, that occurred during the second half of the experiment. Quantification of diazotrophs in the sediment traps indicates that ~ 10 % of UCYN-C from the water column were exported daily to the traps, representing as much as 22.4 ± 5.5 % of the total POC exported at the height of the UCYN-C bloom. This export was mainly due to the aggregation of small (5.7 ± 0.8 μm) UCYN-C cells into large (100-500 μm) aggregates. During the same time period, a DDN transfer experiment based on high-resolution nanometer scale secondary ion mass spectrometry (nanoSIMS) coupled with 15N2 isotopic labelling revealed that 16 ± 6 % of the DDN was released to the dissolved pool

  13. Selecting matched root architecture in tree pairs to be used for assessing N 2 fixation based on soil- 15N-labelling

    NASA Astrophysics Data System (ADS)

    Nasr, Hafedh; Ghorbel, Mohamed Habib; Wallander, Håkan; Dommergues, Yvon René

    2005-03-01

    It is commonly assumed that soil- 15N-labelling provides reliable estimates of N 2 fixation in trees by matching N 2-fixing and non-N 2-fixing tree pairs. As root system is a key parameter in determining suitability of the tree pairs, we compared root architecture of Acacia cyanophylla Lindl. and Casuarina glauca Sieber ex. Spreng. (two N 2-fixing trees) with Eucalyptus camaldulensis Dehn. and Ceratonia siliqua L. (two non-N 2-fixing trees) at 4-year-old in Mediterranean-semiarid zone. The rhizobium strain used appeared more motile than Frankia strain. A. cyanophylla and E. camaldulensis had extensive rooting area and volume of fine roots, and both species tended to develop marked horizontal rooting, compared to C. glauca and C. siliqua. Characteristics of fine- and horizontal-root components can be used in selecting matched root systems of N 2-fixing and reference-paired trees. Root architecture of C. glauca was more similar to C. siliqua, than to E. camaldulensis, and that of A. cyanophylla was more similar to E. camaldulensis than to C. siliqua. Accordingly, E. camaldulensis is an appropriate reference to estimate actual N 2 fixation by A. cyanophylla, and C. siliqua is an appropriate reference for C. glauca, when using soil- 15N-labelling method in the prevailing site environment.

  14. Regulation of nif gene expression and the energetics of N2 fixation over the diel cycle in a hot spring microbial mat.

    PubMed

    Steunou, Anne-Soisig; Jensen, Sheila I; Brecht, Eric; Becraft, Eric D; Bateson, Mary M; Kilian, Oliver; Bhaya, Devaki; Ward, David M; Peters, John W; Grossman, Arthur R; Kühl, Michael

    2008-04-01

    Nitrogen fixation, a prokaryotic, O2-inhibited process that reduces N2 gas to biomass, is of paramount importance in biogeochemical cycling of nitrogen. We analyzed the levels of nif transcripts of Synechococcus ecotypes, NifH subunit and nitrogenase activity over the diel cycle in the microbial mat of an alkaline hot spring in Yellowstone National Park. The results showed a rise in nif transcripts in the evening, with a subsequent decline over the course of the night. In contrast, immunological data demonstrated that the level of the NifH polypeptide remained stable during the night, and only declined when the mat became oxic in the morning. Nitrogenase activity was low throughout the night; however, it exhibited two peaks, a small one in the evening and a large one in the early morning, when light began to stimulate cyanobacterial photosynthetic activity, but O2 consumption by respiration still exceeded the rate of O2 evolution. Once the irradiance increased to the point at which the mat became oxic, the nitrogenase activity was strongly inhibited. Transcripts for proteins associated with energy-producing metabolisms in the cell also followed diel patterns, with fermentation-related transcripts accumulating at night, photosynthesis- and respiration-related transcripts accumulating during the day and late afternoon, respectively. These results are discussed with respect to the energetics and regulation of N2 fixation in hot spring mats and factors that can markedly influence the extent of N2 fixation over the diel cycle.

  15. Symbiotic nitrogen fixation in the fungus gardens of leaf-cutter ants.

    PubMed

    Pinto-Tomás, Adrián A; Anderson, Mark A; Suen, Garret; Stevenson, David M; Chu, Fiona S T; Cleland, W Wallace; Weimer, Paul J; Currie, Cameron R

    2009-11-20

    Bacteria-mediated acquisition of atmospheric N2 serves as a critical source of nitrogen in terrestrial ecosystems. Here we reveal that symbiotic nitrogen fixation facilitates the cultivation of specialized fungal crops by leaf-cutter ants. By using acetylene reduction and stable isotope experiments, we demonstrated that N2 fixation occurred in the fungus gardens of eight leaf-cutter ant species and, further, that this fixed nitrogen was incorporated into ant biomass. Symbiotic N2-fixing bacteria were consistently isolated from the fungus gardens of 80 leaf-cutter ant colonies collected in Argentina, Costa Rica, and Panama. The discovery of N2 fixation within the leaf-cutter ant-microbe symbiosis reveals a previously unrecognized nitrogen source in neotropical ecosystems.

  16. DIAZOTROPHIC GROWTH OF THE MARINE CYANOBACTERIUM TRICHODESMIUM IMS101 IN CONTINUOUS CULTURE: EFFECTS OF GROWTH RATE ON N2 -FIXATION RATE, BIOMASS, AND C:N:P STOICHIOMETRY(1).

    PubMed

    Holl, Carolyn M; Montoya, Joseph P

    2008-08-01

    Trichodesmium N2 fixation has been studied for decades in situ and, recently, in controlled laboratory conditions; yet N2 -fixation rate estimates still vary widely. This variance has made it difficult to accurately estimate the input of new nitrogen (N) by Trichodesmium to the oligotrophic gyres of the world ocean. Field and culture studies demonstrate that trace metal limitation, phosphate availability, the preferential uptake of combined N, light intensity, and temperature may all affect N2 fixation, but the interactions between growth rate and N2 fixation have not been well characterized in this marine diazotroph. To determine the effects of growth rate on N2 fixation, we established phosphorus (P)-limited continuous cultures of Trichodesmium, which we maintained at nine steady-state growth rates ranging from 0.27 to 0.67 d(-1) . As growth rate increased, biomass (measured as particulate N) decreased, and N2 -fixation rate increased linearly. The carbon to nitrogen ratio (C:N) varied from 5.5 to 6.2, with a mean of 5.8 ± 0.2 (mean ± SD, N = 9), and decreased significantly with growth rate. The N:P ratio varied from 23.4 to 45.9, with a mean of 30.5 ± 6.6 (mean ± SD, N = 9), and remained relatively constant over the range of growth rates studied. Relative constancy of C:N:P ratios suggests a tight coupling between the uptake of these three macronutrients and steady-state growth across the range of growth rates. Our work demonstrates that growth rate must be considered when planning studies of the effects of environmental factors on N2 fixation and when modeling the impact of Trichodesmium as a source of new N to oligotrophic regions of the ocean.

  17. A conserved α-proteobacterial small RNA contributes to osmoadaptation and symbiotic efficiency of rhizobia on legume roots.

    PubMed

    Robledo, Marta; Peregrina, Alexandra; Millán, Vicenta; García-Tomsig, Natalia I; Torres-Quesada, Omar; Mateos, Pedro F; Becker, Anke; Jiménez-Zurdo, José I

    2017-07-01

    Small non-coding RNAs (sRNAs) are expected to have pivotal roles in the adaptive responses underlying symbiosis of nitrogen-fixing rhizobia with legumes. Here, we provide primary insights into the function and activity mechanism of the Sinorhizobium meliloti trans-sRNA NfeR1 (Nodule Formation Efficiency RNA). Northern blot probing and transcription tracking with fluorescent promoter-reporter fusions unveiled high nfeR1 expression in response to salt stress and throughout the symbiotic interaction. The strength and differential regulation of nfeR1 transcription are conferred by a motif, which is conserved in nfeR1 promoter regions in α-proteobacteria. NfeR1 loss-of-function compromised osmoadaptation of free-living bacteria, whilst causing misregulation of salt-responsive genes related to stress adaptation, osmolytes catabolism and membrane trafficking. Nodulation tests revealed that lack of NfeR1 affected competitiveness, infectivity, nodule development and symbiotic efficiency of S. meliloti on alfalfa roots. Comparative computer predictions and a genetic reporter assay evidenced a redundant role of three identical NfeR1 unpaired anti Shine-Dalgarno motifs for targeting and downregulation of translation of multiple mRNAs from transporter genes. Our data provide genetic evidence of the hyperosmotic conditions of the endosymbiotic compartments. NfeR1-mediated gene regulation in response to this cue could contribute to coordinate nutrient uptake with the metabolic reprogramming concomitant to symbiotic transitions. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  18. Symbiotic functioning and bradyrhizobial biodiversity of cowpea (Vigna unguiculata L. Walp.) in Africa

    PubMed Central

    2010-01-01

    Background Cowpea is the most important food grain legume in Sub-Saharan Africa. However, no study has so far assessed rhizobial biodiversity and/or nodule functioning in relation to strain IGS types at the continent level. In this study, 9 cowpea genotypes were planted in field experiments in Botswana, South Africa and Ghana with the aim of i) trapping indigenous cowpea root-nodule bacteria (cowpea "rhizobia") in the 3 countries for isolation, molecular characterisation using PCR-RFLP analysis, and sequencing of the 16S - 23S rDNA IGS gene, ii) quantifying N-fixed in the cowpea genotypes using the 15N natural abundance technique, and iii) relating the levels of nodule functioning (i.e. N-fixed) to the IGS types found inside nodules. Results Field measurements of N2 fixation revealed significant differences in plant growth, δ15N values, %Ndfa and amounts of N-fixed between and among the 9 cowpea genotypes in Ghana and South Africa. Following DNA analysis of 270 nodules from the 9 genotypes, 18 strain IGS types were found. Relating nodule function to the 18 IGS types revealed significant differences in IGS type N2-fixing efficiencies. Sequencing the 16S - 23S rDNA gene also revealed 4 clusters, with cluster 2 forming a distinct group that may be a new Bradyrhizobium species. Taken together, our data indicated greater biodiversity of cowpea bradyrhizobia in South Africa relative to Botswana and Ghana. Conclusions We have shown that cowpea is strongly dependant on N2 fixation for its N nutrition in both South Africa and Ghana. Strain IGS type symbiotic efficiency was assessed for the first time in this study, and a positive correlation was discernible where there was sole nodule occupancy. The differences in IGS type diversity and symbiotic efficiency probably accounts for the genotype × environment interaction that makes it difficult to select superior genotypes for use across Africa. The root-nodule bacteria nodulating cowpea in this study all belonged to the

  19. Symbiotic functioning and bradyrhizobial biodiversity of cowpea (Vigna unguiculata L. Walp.) in Africa.

    PubMed

    Pule-Meulenberg, Flora; Belane, Alphonsus K; Krasova-Wade, Tatiana; Dakora, Felix D

    2010-03-23

    Cowpea is the most important food grain legume in Sub-Saharan Africa. However, no study has so far assessed rhizobial biodiversity and/or nodule functioning in relation to strain IGS types at the continent level. In this study, 9 cowpea genotypes were planted in field experiments in Botswana, South Africa and Ghana with the aim of i) trapping indigenous cowpea root-nodule bacteria (cowpea "rhizobia") in the 3 countries for isolation, molecular characterisation using PCR-RFLP analysis, and sequencing of the 16S - 23S rDNA IGS gene, ii) quantifying N-fixed in the cowpea genotypes using the 15N natural abundance technique, and iii) relating the levels of nodule functioning (i.e. N-fixed) to the IGS types found inside nodules. Field measurements of N2 fixation revealed significant differences in plant growth, delta15N values, %Ndfa and amounts of N-fixed between and among the 9 cowpea genotypes in Ghana and South Africa. Following DNA analysis of 270 nodules from the 9 genotypes, 18 strain IGS types were found. Relating nodule function to the 18 IGS types revealed significant differences in IGS type N2-fixing efficiencies. Sequencing the 16S - 23S rDNA gene also revealed 4 clusters, with cluster 2 forming a distinct group that may be a new Bradyrhizobium species. Taken together, our data indicated greater biodiversity of cowpea bradyrhizobia in South Africa relative to Botswana and Ghana. We have shown that cowpea is strongly dependant on N2 fixation for its N nutrition in both South Africa and Ghana. Strain IGS type symbiotic efficiency was assessed for the first time in this study, and a positive correlation was discernible where there was sole nodule occupancy. The differences in IGS type diversity and symbiotic efficiency probably accounts for the genotype x environment interaction that makes it difficult to select superior genotypes for use across Africa. The root-nodule bacteria nodulating cowpea in this study all belonged to the genus Bradyrhizobium. Some

  20. Symbiotic efficiency and phylogeny of the rhizobia isolated from Leucaena leucocephala in arid-hot river valley area in Panxi, Sichuan, China.

    PubMed

    Xu, Kai Wei; Penttinen, Petri; Chen, Yuan Xue; Chen, Qiang; Zhang, Xiaoping

    2013-01-01

    In search of effective nitrogen-fixing strains for inoculating Leucaena leucocephala, we assessed the symbiotic efficiency of 41 rhizobial isolates from root nodules of L. leucocephala growing in the arid-hot river valley area in Panxi, China. The genetic diversity of the isolates was studied by analyzing the housekeeping genes 16S rRNA and recA, and the symbiotic genes nifH and nodC. In the nodulation and symbiotic efficiency assay, only 11 of the 41 isolates promoted the growth of L. leucocephala while the majority of the isolates were ineffective in symbiotic nitrogen fixation. Furthermore, one fourth of the isolates had a growth slowing effect on the host. According to the 16S rRNA and recA gene analyses, most of the isolates were Ensifer spp. The remaining isolates were assigned to Rhizobium, Mesorhizobium and Bradyrhizobium. The sequence analyses indicated that the L. leucocephala rhizobia had undergone gene recombination. In contrast to the promiscuity observed as a wide species distribution of the isolates, the results implied that L. leucocephala is preferentially nodulated by strains that share common symbiosis genes. The symbiotic efficiency was not connected to chromosomal background of the symbionts and isolates carrying a similar nifH or nodC showed totally different nitrogen fixation efficiency.

  1. Metabolic Adaptation, a Specialized Leaf Organ Structure and Vascular Responses to Diurnal N2 Fixation by Nostoc azollae Sustain the Astonishing Productivity of Azolla Ferns without Nitrogen Fertilizer

    PubMed Central

    Brouwer, Paul; Bräutigam, Andrea; Buijs, Valerie A.; Tazelaar, Anne O. E.; van der Werf, Adrie; Schlüter, Urte; Reichart, Gert-Jan; Bolger, Anthony; Usadel, Björn; Weber, Andreas P. M.; Schluepmann, Henriette

    2017-01-01

    Sustainable agriculture demands reduced input of man-made nitrogen (N) fertilizer, yet N2 fixation limits the productivity of crops with heterotrophic diazotrophic bacterial symbionts. We investigated floating ferns from the genus Azolla that host phototrophic diazotrophic Nostoc azollae in leaf pockets and belong to the fastest growing plants. Experimental production reported here demonstrated N-fertilizer independent production of nitrogen-rich biomass with an annual yield potential per ha of 1200 kg−1 N fixed and 35 t dry biomass. 15N2 fixation peaked at noon, reaching 0.4 mg N g−1 dry weight h−1. Azolla ferns therefore merit consideration as protein crops in spite of the fact that little is known about the fern’s physiology to enable domestication. To gain an understanding of their nitrogen physiology, analyses of fern diel transcript profiles under differing nitrogen fertilizer regimes were combined with microscopic observations. Results established that the ferns adapted to the phototrophic N2-fixing symbionts N. azollae by (1) adjusting metabolically to nightly absence of N supply using responses ancestral to ferns and seed plants; (2) developing a specialized xylem-rich vasculature surrounding the leaf-pocket organ; (3) responding to N-supply by controlling transcripts of genes mediating nutrient transport, allocation and vasculature development. Unlike other non-seed plants, the Azolla fern clock is shown to contain both the morning and evening loops; the evening loop is known to control rhythmic gene expression in the vasculature of seed plants and therefore may have evolved along with the vasculature in the ancestor of ferns and seed plants. PMID:28408911

  2. Metabolic Adaptation, a Specialized Leaf Organ Structure and Vascular Responses to Diurnal N2 Fixation by Nostoc azollae Sustain the Astonishing Productivity of Azolla Ferns without Nitrogen Fertilizer.

    PubMed

    Brouwer, Paul; Bräutigam, Andrea; Buijs, Valerie A; Tazelaar, Anne O E; van der Werf, Adrie; Schlüter, Urte; Reichart, Gert-Jan; Bolger, Anthony; Usadel, Björn; Weber, Andreas P M; Schluepmann, Henriette

    2017-01-01

    Sustainable agriculture demands reduced input of man-made nitrogen (N) fertilizer, yet N2 fixation limits the productivity of crops with heterotrophic diazotrophic bacterial symbionts. We investigated floating ferns from the genus Azolla that host phototrophic diazotrophic Nostoc azollae in leaf pockets and belong to the fastest growing plants. Experimental production reported here demonstrated N-fertilizer independent production of nitrogen-rich biomass with an annual yield potential per ha of 1200 kg(-1) N fixed and 35 t dry biomass. (15)N2 fixation peaked at noon, reaching 0.4 mg N g(-1) dry weight h(-1). Azolla ferns therefore merit consideration as protein crops in spite of the fact that little is known about the fern's physiology to enable domestication. To gain an understanding of their nitrogen physiology, analyses of fern diel transcript profiles under differing nitrogen fertilizer regimes were combined with microscopic observations. Results established that the ferns adapted to the phototrophic N2-fixing symbionts N. azollae by (1) adjusting metabolically to nightly absence of N supply using responses ancestral to ferns and seed plants; (2) developing a specialized xylem-rich vasculature surrounding the leaf-pocket organ; (3) responding to N-supply by controlling transcripts of genes mediating nutrient transport, allocation and vasculature development. Unlike other non-seed plants, the Azolla fern clock is shown to contain both the morning and evening loops; the evening loop is known to control rhythmic gene expression in the vasculature of seed plants and therefore may have evolved along with the vasculature in the ancestor of ferns and seed plants.

  3. Mycorrhizal Symbiotic Efficiency on C3 and C4 Plants under Salinity Stress – A Meta-Analysis

    PubMed Central

    Chandrasekaran, Murugesan; Kim, Kiyoon; Krishnamoorthy, Ramasamy; Walitang, Denver; Sundaram, Subbiah; Joe, Manoharan M.; Selvakumar, Gopal; Hu, Shuijin; Oh, Sang-Hyon; Sa, Tongmin

    2016-01-01

    A wide range of C3 and C4 plant species could acclimatize and grow under the impact of salinity stress. Symbiotic relationship between plant roots and arbuscular mycorrhizal fungi (AMF) are widespread and are well known to ameliorate the influence of salinity stress on agro-ecosystem. In the present study, we sought to understand the phenomenon of variability on AMF symbiotic relationship on saline stress amelioration in C3 and C4 plants. Thus, the objective was to compare varied mycorrhizal symbiotic relationship between C3 and C4 plants in saline conditions. To accomplish the above mentioned objective, we conducted a random effects models meta-analysis across 60 published studies. An effect size was calculated as the difference in mycorrhizal responses between the AMF inoculated plants and its corresponding control under saline conditions. Responses were compared between (i) identity of AMF species and AMF inoculation, (ii) identity of host plants (C3 vs. C4) and plant functional groups, (iii) soil texture and level of salinity and (iv) experimental condition (greenhouse vs. field). Results indicate that both C3 and C4 plants under saline condition responded positively to AMF inoculation, thereby overcoming the predicted effects of symbiotic efficiency. Although C3 and C4 plants showed positive effects under low (EC < 4 ds/m) and high (>8 ds/m) saline conditions, C3 plants showed significant effects for mycorrhizal inoculation over C4 plants. Among the plant types, C4 annual and perennial plants, C4 herbs and C4 dicot had a significant effect over other counterparts. Between single and mixed AMF inoculants, single inoculants Rhizophagus irregularis had a positive effect on C3 plants whereas Funneliformis mosseae had a positive effect on C4 plants than other species. In all of the observed studies, mycorrhizal inoculation showed positive effects on shoot, root and total biomass, and in nitrogen, phosphorous and potassium (K) uptake. However, it showed negative

  4. Mycorrhizal Symbiotic Efficiency on C3 and C4 Plants under Salinity Stress - A Meta-Analysis.

    PubMed

    Chandrasekaran, Murugesan; Kim, Kiyoon; Krishnamoorthy, Ramasamy; Walitang, Denver; Sundaram, Subbiah; Joe, Manoharan M; Selvakumar, Gopal; Hu, Shuijin; Oh, Sang-Hyon; Sa, Tongmin

    2016-01-01

    A wide range of C3 and C4 plant species could acclimatize and grow under the impact of salinity stress. Symbiotic relationship between plant roots and arbuscular mycorrhizal fungi (AMF) are widespread and are well known to ameliorate the influence of salinity stress on agro-ecosystem. In the present study, we sought to understand the phenomenon of variability on AMF symbiotic relationship on saline stress amelioration in C3 and C4 plants. Thus, the objective was to compare varied mycorrhizal symbiotic relationship between C3 and C4 plants in saline conditions. To accomplish the above mentioned objective, we conducted a random effects models meta-analysis across 60 published studies. An effect size was calculated as the difference in mycorrhizal responses between the AMF inoculated plants and its corresponding control under saline conditions. Responses were compared between (i) identity of AMF species and AMF inoculation, (ii) identity of host plants (C3 vs. C4) and plant functional groups, (iii) soil texture and level of salinity and (iv) experimental condition (greenhouse vs. field). Results indicate that both C3 and C4 plants under saline condition responded positively to AMF inoculation, thereby overcoming the predicted effects of symbiotic efficiency. Although C3 and C4 plants showed positive effects under low (EC < 4 ds/m) and high (>8 ds/m) saline conditions, C3 plants showed significant effects for mycorrhizal inoculation over C4 plants. Among the plant types, C4 annual and perennial plants, C4 herbs and C4 dicot had a significant effect over other counterparts. Between single and mixed AMF inoculants, single inoculants Rhizophagus irregularis had a positive effect on C3 plants whereas Funneliformis mosseae had a positive effect on C4 plants than other species. In all of the observed studies, mycorrhizal inoculation showed positive effects on shoot, root and total biomass, and in nitrogen, phosphorous and potassium (K) uptake. However, it showed negative

  5. Cyanobacterial Lactate Oxidases Serve as Essential Partners in N2 Fixation and Evolved into Photorespiratory Glycolate Oxidases in Plants[w

    PubMed Central

    Hackenberg, Claudia; Kern, Ramona; Hüge, Jan; Stal, Lucas J.; Tsuji, Yoshinori; Kopka, Joachim; Shiraiwa, Yoshihiro; Bauwe, Hermann; Hagemann, Martin

    2011-01-01

    Glycolate oxidase (GOX) is an essential enzyme involved in photorespiratory metabolism in plants. In cyanobacteria and green algae, the corresponding reaction is catalyzed by glycolate dehydrogenases (GlcD). The genomes of N2-fixing cyanobacteria, such as Nostoc PCC 7120 and green algae, appear to harbor genes for both GlcD and GOX proteins. The GOX-like proteins from Nostoc (No-LOX) and from Chlamydomonas reinhardtii showed high l-lactate oxidase (LOX) and low GOX activities, whereas glycolate was the preferred substrate of the phylogenetically related At-GOX2 from Arabidopsis thaliana. Changing the active site of No-LOX to that of At-GOX2 by site-specific mutagenesis reversed the LOX/GOX activity ratio of No-LOX. Despite its low GOX activity, No-LOX overexpression decreased the accumulation of toxic glycolate in a cyanobacterial photorespiratory mutant and restored its ability to grow in air. A LOX-deficient Nostoc mutant grew normally in nitrate-containing medium but died under N2-fixing conditions. Cultivation under low oxygen rescued this lethal phenotype, indicating that N2 fixation was more sensitive to O2 in the Δlox Nostoc mutant than in the wild type. We propose that LOX primarily serves as an O2-scavenging enzyme to protect nitrogenase in extant N2-fixing cyanobacteria, whereas in plants it has evolved into GOX, responsible for glycolate oxidation during photorespiration. PMID:21828292

  6. Comparative transcriptome analysis of nodules of two Mesorhizobium-chickpea associations with differential symbiotic efficiency under phosphate deficiency.

    PubMed

    Nasr Esfahani, Maryam; Inoue, Komaki; Chu, Ha Duc; Nguyen, Kien Huu; Van Ha, Chien; Watanabe, Yasuko; Burritt, David J; Herrera-Estrella, Luis; Mochida, Keiichi; Tran, Lam-Son Phan

    2017-09-01

    Phosphate (Pi) deficiency is known to be a major limitation for symbiotic nitrogen fixation (SNF), and hence legume crop productivity globally. However, very little information is available on the adaptive mechanisms, particularly in the important legume crop chickpea (Cicer arietinum L.), which enable nodules to respond to low-Pi availability. Thus, to elucidate these mechanisms in chickpea nodules at molecular level, we used an RNA sequencing approach to investigate transcriptomes of the nodules in Mesorhizobium mediterraneum SWRI9-(MmSWRI9)-chickpea and M. ciceri CP-31-(McCP-31)-chickpea associations under Pi-sufficient and Pi-deficient conditions, of which the McCP-31-chickpea association has a better SNF capacity than the MmSWRI9-chickpea association during Pi starvation. Our investigation revealed that more genes showed altered expression patterns in MmSWRI9-induced nodules than in McCP-31-induced nodules (540 vs. 225) under Pi deficiency, suggesting that the Pi-starvation-more-sensitive MmSWRI9-induced nodules required expression change in a larger number of genes to cope with low-Pi stress than the Pi-starvation-less-sensitive McCP-31-induced nodules. The functional classification of differentially expressed genes (DEGs) was examined to gain an understanding of how chickpea nodules respond to Pi starvation, caused by soil Pi deficiency. As a result, more DEGs involved in nodulation, detoxification, nutrient/ion transport, transcriptional factors, key metabolic pathways, Pi remobilization and signalling were found in Pi-starved MmSWRI9-induced nodules than in Pi-starved McCP-31-induced nodules. Our findings have enabled the identification of molecular processes that play important roles in the acclimation of nodules to Pi deficiency, ultimately leading to the development of Pi-efficient chickpea symbiotic associations suitable for Pi-deficient soils. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  7. Rhizobia with different symbiotic efficiencies nodulate Acaciella angustissima in Mexico, including Sinorhizobium chiapanecum sp. nov. which has common symbiotic genes with Sinorhizobium mexicanum

    PubMed Central

    Rincón-Rosales, Reiner; Lloret, Lourdes; Ponce, Edith; Martínez-Romero, Esperanza

    2009-01-01

    Bacteria from nodules of the legume Acaciella angustissima native to the south of Mexico were characterized genetically and their nodulation and competitiveness were evaluated. Phylogenetic studies derived from rpoB gene sequences indicated that A. angustissima is nodulated by Sinorhizobium mexicanum, Rhizobium tropici, Mesorhizobium plurifarium and Agrobacterium tumefaciens and by bacteria related to Sinorhizobium americanum, Sinorhizobium terangae, Rhizobium etli and Rhizobium gallicum. A new lineage related to S. terangae is recognized based on the sequences of gyrA, nolR, recA, rpoB and rrs genes, DNA–DNA hybridization and phenotypic characteristics. The name for this new species is Sinorhizobium chiapanecum and its type strain is ITTG S70T. The symbiotic genes nodA and nifH were similar to those from S. mexicanum strains, which are Acaciella symbionts as well, with nodA gene sequences grouped within a cluster of nod genes from strains that nodulate plants from the Mimosoideae subfamily of the Leguminosae. Sinorhizobium isolates were the most frequently obtained from A. angustissima nodules and were among the best strains to promote plant growth in A. angustissima and to compete in interstrain nodule competition assays. Lateral transfer of symbiotic genes is not evident among the genera that nodulate A. angustissima (Rhizobium, Sinorhizobium and Mesorhizobium) but may occur among the sympatric and closely related sinorhizobia that nodulate Acaciella. PMID:19120461

  8. Mechanisms of physiological adjustment of N2 fixation in Cicer arietinum L. (chickpea) during early stages of water deficit: single or multi-factor controls.

    PubMed

    Nasr Esfahani, Maryam; Sulieman, Saad; Schulze, Joachim; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo; Tran, Lam-Son Phan

    2014-09-01

    Drought negatively impacts symbiotic nitrogen fixation (SNF) in Cicer arietinum L. (chickpea), thereby limiting yield potential. Understanding how drought affects chickpea nodulation will enable the development of strategies to biotechnologically engineer chickpea varieties with enhanced SNF under drought conditions. By analyzing carbon and nitrogen metabolism, we studied the mechanisms of physiological adjustment of nitrogen fixation in chickpea plants nodulated with Mesorhizobium ciceri during both drought stress and subsequent recovery. The nitrogenase activity, levels of several key carbon (in nodules) and nitrogen (in both nodules and leaves) metabolites and antioxidant compounds, as well as the activity of related nodule enzymes were examined in M. ciceri-inoculated chickpea plants under early drought stress and subsequent recovery. Results indicated that drought reduced nitrogenase activity, and that this was associated with a reduced expression of the nifK gene. Furthermore, drought stress promoted an accumulation of amino acids, mainly asparagine in nodules (but not in leaves), and caused a cell redox imbalance in nodules. An accumulation of organic acids, especially malate, in nodules, which coincided with the decline of nodulated root respiration, was also observed under drought stress. Taken together, our findings indicate that reduced nitrogenase activity occurring at early stages of drought stress involves, at least, the inhibition of respiration, nitrogen accumulation and an imbalance in cell redox status in nodules. The results of this study demonstrate the potential that the genetic engineering-based improvement of SNF efficiency could be applied to reduce the impact of drought on the productivity of chickpea, and perhaps other legume crops. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

  9. The Effect of Land-use Change and Management on Free-living N2 fixation in the Brazilian Atlantic Forest

    NASA Astrophysics Data System (ADS)

    De Oliveira Bomfim, B.; Silva, L. C. R.; Horwath, W. R.; Hello, J.; Doane, T. A.

    2016-12-01

    Globally, primary tropical forests are increasingly disturbed by deforestation, urbanization, agriculture, and cattle ranching. It has been recognized that the resulting (secondary) forests now play a key role in global biogeochemical cycles; however, little is known about alterations in forest function caused by the combination of disturbance and land use change. Fire, deforestation, and forest-to-monocrop conversion are all likely to affect biotic N inputs, yet our understanding of how free-living N2 fixation influences ecosystem response after disturbance remains poorly understood. Our research is assessing the role of asymbiotic (free-living) biological nitrogen fixation (BNF), a microbially-mediated process responsible for providing N inputs across terrestrial ecosystems and modulating the effect of fire and land cover in secondary forest succession. Free-living BNF is being quantified through incubations using stable isotope (15N2 labeling experiment) in different substrates (soil and leaf litter) under contrasting land use and management in the Brazilian Atlantic Forest, the most deforested Biome in Brazil with only 7% of its original cover. Soil and litter samples were collected in primary forests, 12-year secondary forests, Eucalyptus spp. plantations and 10-year Brachiaria brizantha pastures. Preliminary results indicate that free-living BNF rates did not vary significantly between either secondary land use (0.02 to 0.46 µg N2 fixed gDW-1 h-1), but rates were significantly higher in the litter layer (0.32 to 3.8 µg N2 fixed gDW-1 h-1) than in the surface soil (0 - 10 cm and 10 - 30 cm). Free-living BNF in this stretch of the Brazilian Atlantic Forest seems not to be significantly affected by contrasting land use and management.

  10. Measuring carbon and N2 fixation in field populations of colonial and free-living unicellular cyanobacteria using nanometer-scale secondary ion mass spectrometry(1).

    PubMed

    Foster, Rachel A; Sztejrenszus, Saar; Kuypers, Marcel M M

    2013-06-01

    Unicellular cyanobacteria are now recognized as important to the marine N and C cycles in open ocean gyres, yet there are few direct in situ measurements of their activities. Using a high-resolution nanometer scale secondary ion mass spectrometer (nanoSIMS), single cell N2 and C fixation rates were estimated for unicellular cyanobacteria resembling N2 fixer Crocosphaera watsonii. Crocosphaera watsonii-like cells were observed in the subtropical North Pacific gyre (22°45' N, 158°0' W) as 2 different phenotypes: colonial and free-living. Colonies containing 3-242 cells per colony were observed and cell density in colonies increased with incubation time. Estimated C fixation rates were similarly high in both phenotypes and unexpectedly for unicellular cyanobacteria 85% of the colonial cells incubated during midday were also enriched in (15) N above natural abundance. Highest (15) N enrichment and N2 fixation rates were found in cells incubated overnight where up to 64% of the total daily fixed N in the upper surface waters was attributed to both phenotypes. The colonial cells retained newly fixed C in a sulfur-rich matrix surrounding the cells and often cells of both phenotypes possessed areas (<1 nm) of enriched (15) N and (13) C resembling storage granules. The nanoSIMS imaging of the colonial cells also showed evidence for a division of N2 and C fixation activity across the colony where few individual cells (<34%) in a given colony were enriched in both (15) N and (13) C above the colony average. Our results provide new insights into the ecophysiology of unicellular cyanobacteria.

  11. Assessing genotypic diversity and symbiotic efficiency of five rhizobial legume interactions under cadmium stress for soil phytoremediation.

    PubMed

    Guefrachi, I; Rejili, M; Mahdhi, M; Mars, M

    2013-01-01

    In the framework of soil phytoremediation using local legume plants coupled with their native root-nodulating bacteria to increase forage yields and preserve contaminated soils in arid regions of Tunisia, we investigated the diversity of bacteria from root nodules of Lathyrus sativus, Lens culinaris, Medicago marina, M. truncatula, and M. minima and the symbiotic efficiency of these five legume symbiosis under Cadmium stress. Fifty bacterial strains were characterized using physiological and biochemical features such heavy metals resistant, and PCR-RFLP of 16S rDNA. Taxonomically, the isolates nodulating L. sativus, and L. culinaris are species within the genera Rhizobium and the ones associated to Medicago sp, within the genera Sinorhizobium. The results revealed also that the cadmium tolerance of the different legumes-rhizobia interaction was as follows: M. minima < M. truncatula < M. marina < L. sativus < L. culinaris indicating that the effect of Cadmium on root nodulation and biomass production is more deleterious on M. minima-S. meliloti and M. truncatula-S. meliloti than in other symbiosis. Knowledge on genetic and functional diversity of M. marina, L. sativus and L. culinaris microsymbiotes is very useful for inoculant strain selection and can be selected to develop inoculants for soil phytoremediation.

  12. Symbiotic Expressions

    NASA Astrophysics Data System (ADS)

    Bernecky, Robert; Herhut, Stephan; Scholz, Sven-Bodo

    We introduce symbiotic expressions, a method for algebraic simplification within a compiler, in lieu of an SMT solver, such as Yices or the Omega Calculator. Symbiotic expressions are compiler-generated expressions, temporarily injected into a program's abstract syntax tree (AST). The compiler's normal optimizations interpret and simplify those expressions, making their results available for the compiler to use as a basis for decisions about further optimization of the source program. The expressions are symbiotic, in the sense that both parties benefit: an optimization benefits, by using the compiler itself to simplify expressions that have been attached, lamprey-like, to the AST by the optimization; the program being compiled benefits, from improved run-time in both serial and parallel environments.

  13. Comparison of N(2) Fixation and Yields in Cajanus cajan between Hydrogenase-Positive and Hydrogenase-Negative Rhizobia by In Situ Acetylene Reduction Assays and Direct N Partitioning.

    PubMed

    La Favre, J S; Focht, D D

    1983-08-01

    Pigeon peas [Cajanus cajan (L.) Millsp.] were grown in soil columns containing (15)N-enriched organic matter. Seasonal N(2) fixation activity was determined by periodically assaying plants for reduction of C(2)H(2). N(2) fixation rose sharply from the first assay period at 51 days after planting to a peak of activity between floral initiation and fruit set. N(2) fixation (acetylene reduction) activity dropped concomitantly with pod maturation but recovered after pod harvests. Analysis of (15)N content of plant shoots revealed that approximately 91 to 94% of plant N was derived from N(2) fixation. The effect of inoculation with hydrogenase-positive and hydrogenase-negative rhizobia was examined. Pigeon peas inoculated with strain P132 (hydrogenase-positive) yielded significantly more total shoot N than other inoculated or uninoculated treatments. However, two other hydrogenase-positive strains did not yield significantly more total shoot N than a hydrogenase-negative strain. The extent of nodulation by inoculum strains compared to indigenous rhizobia was determined by typing nodules according to intrinsic antibiotic resistance of the inoculum strains. The inoculum strains were detected in almost all typed nodules of inoculated plants.Gas samples were taken from soil columns several times during the growth cycle of the plants. H(2) was never detected, even in columns containing pigeon peas inoculated with hydrogenase-negative rhizobia. This was attributed to H(2) consumption by soil bacteria. Estimation of N(2) fixation by acetylene reduction activity was closest to the direct (15)N method when ethylene concentrations in the gas headspace (between the column lid and soil surface) were extrapolated to include the soil pore space as opposed solely to measurement in the headspace. There was an 8-fold difference between the two acetylene reduction assay methods of estimation. Based on a planting density of 15,000 plants per hectare, the direct (15)N fixation rates ranged

  14. Symbiotic stars

    NASA Technical Reports Server (NTRS)

    Kafatos, M.; Michalitsianos, A. G.

    1984-01-01

    The physical characteristics of symbiotic star systems are discussed, based on a review of recent observational data. A model of a symbiotic star system is presented which illustrates how a cool red-giant star is embedded in a nebula whose atoms are ionized by the energetic radiation from its hot compact companion. UV outbursts from symbiotic systems are explained by two principal models: an accretion-disk-outburst model which describes how material expelled from the tenuous envelope of the red giant forms an inwardly-spiralling disk around the hot companion, and a thermonuclear-outburst model in which the companion is specifically a white dwarf which superheats the material expelled from the red giant to the point where thermonuclear reactions occur and radiation is emitted. It is suspected that the evolutionary course of binary systems is predetermined by the initial mass and angular momentum of the gas cloud within which binary stars are born. Since red giants and Mira variables are thought to be stars with a mass of one or two solar mass, it is believed that the original cloud from which a symbiotic system is formed can consist of no more than a few solar masses of gas.

  15. Surviving and thriving in terms of symbiotic performance of antibiotic and phage-resistant mutants of Bradyrhizobium of soybean [Glycine max (L.) Merrill].

    PubMed

    Anand, Akhil; Jaiswal, Sanjay Kumar; Dhar, Banshi; Vaishampayan, Akhouri

    2012-10-01

    Rhizobial inoculation plays an important role in yielding enhancement of soybean, but it is frequently disturbed by competition with bacterial population present in the soil. Identification of potential indigenous rhizobia as competitive inoculants for efficient nodulation and N(2)-fixation of soybean was assessed under laboratory and field conditions. Two indigenous bradyrhizobial isolates (MPSR033 and MPSR220) and its derived different antibiotic (streptomycin and gentamicin) and phage (RT5 and RT6)-resistant mutant strains were used for competition study. Nodulation occupancy between parent and mutant strains was compared on soybean cultivar JS335 under exotic condition. Strain MPSR033 Sm(r) V(r) was found highly competitive for nodule occupancy in all treatment combinations. On the basis of laboratory experiments four indigenous strains (MPSR033, MPSR033 Sm(r), MPSR033 Sm(r) V(r), MPSR220) were selected for their symbiotic performance along with two exotic strains (USDA123 and USDA94) on two soybean cultivars under field conditions. A significant symbiotic interaction between Bradyrhizobium strains and soybean cultivar was observed. Strain MPSR033 Sm(r) V(r) was found superior among the rhizobial treatments in seed yield production with both cultivars. The 16S rRNA region sequence analysis of the indigenous strains showed close relationship with Bradyrhizobium yuanmingense strain. These findings widen out the usefulness of antibiotic-resistance marked phage-resistant bradyrhizobial strains in interactive mode for studying their symbiotic effectiveness with host plant, and open the way to study the mechanism of contact-dependent growth inhibition in rhizobia.

  16. Dynamics of N2 fixation and fate of diazotroph-derived nitrogen in a low-nutrient, low-chlorophyll ecosystem: results from the VAHINE mesocosm experiment (New Caledonia)

    NASA Astrophysics Data System (ADS)

    Bonnet, Sophie; Berthelot, Hugo; Turk-Kubo, Kendra; Fawcett, Sarah; Rahav, Eyal; L'Helguen, Stéphane; Berman-Frank, Ilana

    2016-05-01

    N2 fixation rates were measured daily in large (˜ 50 m3) mesocosms deployed in the tropical southwest Pacific coastal ocean (New Caledonia) to investigate the temporal variability in N2 fixation rates in relation with environmental parameters and study the fate of diazotroph-derived nitrogen (DDN) in a low-nutrient, low-chlorophyll ecosystem. The mesocosms were fertilized with ˜ 0.8 µM dissolved inorganic phosphorus (DIP) to stimulate diazotrophy. Bulk N2 fixation rates were replicable between the three mesocosms, averaged 18.5 ± 1.1 nmol N L-1 d-1 over the 23 days, and increased by a factor of 2 during the second half of the experiment (days 15 to 23) to reach 27.3 ± 1.0 nmol N L-1 d-1. These later rates measured after the DIP fertilization are higher than the upper range reported for the global ocean. During the 23 days of the experiment, N2 fixation rates were positively correlated with seawater temperature, primary production, bacterial production, standing stocks of particulate organic carbon (POC), nitrogen (PON) and phosphorus (POP), and alkaline phosphatase activity, and negatively correlated with DIP concentrations, DIP turnover time, nitrate, and dissolved organic nitrogen and phosphorus concentrations. The fate of DDN was investigated during a bloom of the unicellular diazotroph UCYN-C that occurred during the second half of the experiment. Quantification of diazotrophs in the sediment traps indicates that ˜ 10 % of UCYN-C from the water column was exported daily to the traps, representing as much as 22.4 ± 5.5 % of the total POC exported at the height of the UCYN-C bloom. This export was mainly due to the aggregation of small (5.7 ± 0.8 µm) UCYN-C cells into large (100-500 µm) aggregates. During the same time period, a DDN transfer experiment based on high-resolution nanometer-scale secondary ion mass spectrometry (nanoSIMS) coupled with 15N2 isotopic labeling revealed that 16 ± 6 % of the DDN was released to the dissolved pool and 21 ± 4

  17. Unicellular cyanobacterium symbiotic with a single-celled eukaryotic alga.

    PubMed

    Thompson, Anne W; Foster, Rachel A; Krupke, Andreas; Carter, Brandon J; Musat, Niculina; Vaulot, Daniel; Kuypers, Marcel M M; Zehr, Jonathan P

    2012-09-21

    Symbioses between nitrogen (N)(2)-fixing prokaryotes and photosynthetic eukaryotes are important for nitrogen acquisition in N-limited environments. Recently, a widely distributed planktonic uncultured nitrogen-fixing cyanobacterium (UCYN-A) was found to have unprecedented genome reduction, including the lack of oxygen-evolving photosystem II and the tricarboxylic acid cycle, which suggested partnership in a symbiosis. We showed that UCYN-A has a symbiotic association with a unicellular prymnesiophyte, closely related to calcifying taxa present in the fossil record. The partnership is mutualistic, because the prymnesiophyte receives fixed N in exchange for transferring fixed carbon to UCYN-A. This unusual partnership between a cyanobacterium and a unicellular alga is a model for symbiosis and is analogous to plastid and organismal evolution, and if calcifying, may have important implications for past and present oceanic N(2) fixation.

  18. A vapBC-type toxin-antitoxin module of Sinorhizobium meliloti influences symbiotic efficiency and nodule senescence of Medicago sativa.

    PubMed

    Lipuma, Justine; Cinege, Gyöngyi; Bodogai, Monica; Oláh, Boglárka; Kiers, Aurélie; Endre, Gabriella; Dupont, Laurence; Dusha, Ilona

    2014-12-01

    The symbiotic nitrogen-fixing soil bacterium Sinorhizobium meliloti carries a large number of toxin-antitoxin (TA) modules both on the chromosome and megaplasmids. One of them, the vapBC-5 module that belongs to the type II systems was characterized here. It encodes an active toxin vapC-5, and was shown to be controlled negatively by the complex of its own proteins. Different mutants of the vapBC-5 genes exhibited diverse effects on symbiotic efficiency during interaction with the host plant Medicago sativa. The absence of the entire vapBC-5 region had no influence on nodule formation and nitrogen fixation properties. The strain carrying an insertion in the antitoxin gene showed a reduced nitrogen fixation capacity resulting in a lower plant yield. In contrast, when the toxin gene was mutated, the strain developed more efficient symbiosis with the host plant. The nitrogen fixing root nodules had a delayed senescent phenotype and contained elevated level of plant-derived molecules characteristic of later steps of nodule development. The longer bacteroid viability and abundance of active nitrogen fixing zone resulted in increased production of plant material. These data indicate that modification of the toxin/antitoxin production may influence bacteroid metabolism and may have an impact on the adaptation to changing environmental conditions.

  19. Mutation in the ntrR gene, a member of the vap gene family, increases the symbiotic efficiency of Sinorhizobium meliloti.

    PubMed

    Oláh, B; Kiss, E; Györgypál, Z; Borzi, J; Cinege, G; Csanádi, G; Batut, J; Kondorosi, A; Dusha, I

    2001-07-01

    In specific plant organs, namely the root nodules of alfalfa, fixed nitrogen (ammonia) produced by the symbiotic partner Sinorhizobium meliloti supports the growth of the host plant in nitrogen-depleted environment. Here, we report that a derivative of S. meliloti carrying a mutation in the chromosomal ntrR gene induced nodules with enhanced nitrogen fixation capacity, resulting in an increased dry weight and nitrogen content of alfalfa. The efficient nitrogen fixation is a result of the higher expression level of the nifH gene, encoding one of the subunits of the nitrogenase enzyme, and nifA, the transcriptional regulator of the nif operon. The ntrR gene, controlled negatively by its own product and positively by the symbiotic regulator syrM, is expressed in the same zone of nodules as the nif genes. As a result of the nitrogen-tolerant phenotype of the strain, the beneficial effect of the mutation on efficiency is not abolished in the presence of the exogenous nitrogen source. The ntrR mutant is highly competitive in nodule occupancy compared with the wild-type strain. Sequence analysis of the mutant region revealed a new cluster of genes, termed the "ntrPR operon," which is highly homologous to a group of vap-related genes of various pathogenic bacteria that are presumably implicated in bacterium-host interactions. On the basis of its favorable properties, the strain is a good candidate for future agricultural utilization.

  20. Impairment of NtAQP1 gene expression in tobacco plants does not affect root colonisation pattern by arbuscular mycorrhizal fungi but decreases their symbiotic efficiency under drought.

    PubMed

    Porcel, Rosa; Gómez, Manuel; Kaldenhoff, Ralf; Ruiz-Lozano, Juan Manuel

    2005-09-01

    We investigated in two tobacco (Nicotiana tabacum) plant lines (wildtype or antisense mutant) whether impairment in expression of the plasma membrane aquaporin gene (NtAQP1) affects the arbuscular mycorrhizal (AM) fungal colonisation pattern or the symbiotic efficiency of AM fungi. These two objectives were investigated under well-watered and drought stress conditions. Both plant lines had a similar pattern of root colonisation under well-watered and drought stress conditions. In contrast, under drought stress, AM wildtype plants grew faster than mycorrhizal antisense plants. Plant gas exchange also appeared to depend on the expression of NtAQP1 and parallelled the determined growth increments. The implications of enhanced symplastic water transport via NtAQP1 for the efficiency of the AM symbiosis under drought stress conditions are further discussed.

  1. Uptake Hydrogenase Activity Determined by Plasmid pRL6JI in Rhizobium leguminosarum Does Not Increase Symbiotic Nitrogen Fixation

    PubMed Central

    Cunningham, Scott D.; Kapulnik, Yoram; Brewin, Nicholas J.; Phillips, Donald A.

    1985-01-01

    Six mutants of Rhizobium leguminosarum 3855 lacking uptake hydrogenase activity (Hup− phenotype) as a result of Tn5-mob mutagenesis of the hup-containing plasmid pRL6JI were tested for symbiotic performance on Pisum sativum L. and Vicia benghalensis L. Three pea cultivars and one vetch line, which induce four different levels of Hup activity in strain 3855, were grown to flowering under microbiologically controlled conditions in the absence of combined N. Direct Kjeldahl N measurements showed that in every case at least one Hup− mutant fixed as much N2 as the isogenic Hup+ strain. Measures of C2H2 reduction, H2 evolution, 3H2 incorporation, and plant dry weight were consistent with the interpretation that the oxidation of H2 produced by the nitrogenase enzyme complex was not necessarily associated with increased N2 fixation in these symbiotic associations. Tests with a smaller subset of the Hup− strains under four different root environments ranging from pH 5.0 to 8.2 likewise showed no significant advantage for the isogenic Hup+ strain. It was concluded that the improvements in symbiotic N2 fixation produced by pRL6JI are associated with some trait other than the Hup+ phenotype. PMID:16346912

  2. [Construction of high-effective symbiotic bacteria: evolutionary models and genetic approaches].

    PubMed

    Provorov, N A; Onishchuk, O P; Iurgel', S N; Kurchak, O N; Chizhevskaia, E P; Vorob'ev, N I; Zatovskaia, T V; Simarov, B V

    2014-11-01

    Using the example of N2-fixing legume-rhizobial symbiosis, we demonstrated that the origin and evolution of bacteria symbiotic for plants involve the following: 1) the formation of novel sym gene systems based on reorganizations of the bacterial genomes and on the gene transfer from the distant organisms; 2) the loss of genes encoding for functions that are required for autonomous performance but interfere with symbiotic functions (negative regulators of symbiosis). Therefore, the construction of effective rhizobia strains should involve improvement of sym genes activities (for instance, nif, fix, and dct genes, encoding for nitrogenase synthesis or for the energy supply of N2 fixation), as well as the inactivation of negative regulators of symbiosis identified in our lab (eff genes encoding for the transport of sugars, and the production of polysaccharides, and storage compounds, as well as for oxidative-reductive processes).

  3. Employing of the amplified fragment length polymorphism (AFLP) methodology as an efficient population genetic tool for symbiotic cnidarians.

    PubMed

    Amar, Keren-Or; Douek, Jacob; Rabinowitz, Claudette; Rinkevich, Baruch

    2008-01-01

    Although the use of molecular markers in population genetics of marine organisms is increasingly employed, methodologic limitations still hampered the research for some taxa, such as symbiotic cnidarians, including scleractinian corals. The development of molecular tools in scleractinian corals' studies is faced with a list of obstacles, such as high cost, labor, time consuming, contamination with foreign DNA, and markers with low resolution. The AFLP (amplified fragment length polymorphism) method, overcomes most of the obstacles listed above except of the difficulty of contamination by algal symbiont DNA. We compared the implication of two pre-DNA extraction treatments to obtain coral DNA free of algal contaminations, termed as CPEM, cell population enriched method, and TTEM, total tissue extraction method. The CPEM process result in pure coral DNA for all samples, but is time consuming, whereas in the TTEM process, approximately 25% to 18% of the samples are still contaminated by algal DNA. However, algal DNA contaminations in the PCR at 2.5 x 10(-1) ng level (approximately 100 algal cells) and below, did not amplify any new AFLP band or peak for neither radioactive nor florescence analyses. Therefore, even the TTEM process may be used because it is faster, easier to handle, and easily employed on a large amount of samples, with minimal contamination artifacts. When correctly employed, both methods are applicable to wide experimental manipulations.

  4. Development of an efficient method for screening microorganisms by using symbiotic association between Nasutitermes takasagoensis and intestinal microorganisms.

    PubMed

    Hayashi, Arata; Aoyagi, Hideki; Kinjyo, Kazuhiko; Yoshimura, Tsuyoshi; Tanaka, Hideo

    2007-07-01

    Screening method of microorganisms that utilized the symbiotic association between insect (Nasutitermes takasagoensis: Nt) and intestinal microorganisms was developed. The existence of desired microorganisms that grew by degrading difficult-to-degrade materials in the gut was detected using survivability of Nt as an indicator. The desired microorganisms were isolated from the survived Nt. It was thought that guts of Nt behave as continuous culture systems whereby microorganisms that cannot degrade diet components are washed out, whereas those that can degrade it are retained and concentrated in the gut. About 60% of Nt fed with phenol artificial diet (PAD) died within 7 days, while 4% of termites survived for 9 days. The structure of intestinal microorganisms of the survived Nt fed with PAD differed from the bacterial communities obtained from enrichment culture (which contained phenol) of wood-feeding Nt. Relatively high colonies (650-times) were detected in the gut of Nt fed on phenol artificial diet compared with those obtained when Nt was fed on wood. Seven denaturing gradient gel electrophoresis (DGGE) bands were detected from gut of wood-feeding Nt, whereas 11 DGGE-bands were detected from that of phenol-feeding Nt. Out of 11 DGGE-bands, 5 of them were sequenced, and bacterial species including phenol-degrading bacteria were identified.

  5. Electrochemical Reduction of N2 under Ambient Conditions for Artificial N2 Fixation and Renewable Energy Storage Using N2 /NH3 Cycle.

    PubMed

    Bao, Di; Zhang, Qi; Meng, Fan-Lu; Zhong, Hai-Xia; Shi, Miao-Miao; Zhang, Yu; Yan, Jun-Min; Jiang, Qing; Zhang, Xin-Bo

    2017-01-01

    Using tetrahexahedral gold nanorods as a heterogeneous electrocatalyst, an electrocatalytic N2 reduction reaction is shown to be possible at room temperature and atmospheric pressure, with a high Faradic efficiency up to 4.02% at -0.2 V vs reversible hydrogen electrode (1.648 µg h(-1) cm(-2) and 0.102 µg h(-1) cm(-2) for NH3 and N2 H4 ·H2 O, respectively). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. De-inking sludge and phosphorus effects on growth and symbiotic dinitrogen fixation in forage legumes.

    PubMed

    Allahdadi, Iraj; Beauchamp, Chantal J; Califour, François P; Khalaj, Hamideh; Labafi, M R

    2007-07-15

    The de-inking process produces a waste by-product, called de-inking paper sludge (DS), that contains paper fibers, clay particles and inks and high carbon (C) concentrations combined with low nitrogen (N) and phosphorus (P) concentrations. The use of high rates of DS to increase the soil organic matter thus requires provision of high rates of N and P for adequate plant growth. Using dinitrogen (N2)-fixing forage legumes is an alternative to N fertilization under such circumstances. In a greenhouse study, DS rates of 0, 50 or 100 Mg ha(-1) and five rates of P (40, 80, 120, 160, or 200 kg P2O5 ha(-1)) were applied on two soil types, a clay loam (Pintendre) and a silty clay loam (St-Augustin). Nitrogen uptake and symbiotic N2 fixation (SNF) were estimated in alfalfa (Medicago sativa L.), sweetclover (Melilotus officinalis L.) and red clover (Trifolium pratense L.); Bromegrass (Bromus inermis L.) and alfalfa ineffective for N2 fixation were used as the reference (non-N2 fixing) crops. Atmospheric N2 fixation was estimated by natural abundance of 15N (815N). Under controlled conditions, high rates of DS substantially reduced delta15N values, particularly with high rates of P. In addition, N uptake of legumes generally increased with increased P concentrations and it peaked with 120 or 160 kg P2O5 ha(-1). Correlated with the trends observed with delta15N values and it peaked with 120 or 160 kg P2O5 ha(-1). Present results showed that under high rates of application of DS and adequate P supply, forage legumes fixed more atmospheric N2. delta15N can be a good indicator of SNF under the above-mentioned conditions.

  7. Asparagine: an amide of particular distinction in the regulation of symbiotic nitrogen fixation of legumes.

    PubMed

    Sulieman, Saad; Tran, Lam-Son Phan

    2013-09-01

    Symbiotic nitrogen fixation is tightly regulated by a range of fine processes at the nodule level, over which the host plant has overall control through the whole life of the plant. The operation of this control at the nodule level is not yet fully understood, but greater knowledge will ultimately lead to a better improvement of N2 fixation through the use of crop legumes and genetic engineering of crop plants for higher performance. It has been suggested that, nodule responses to the nutritional complexity of the rhizosphere environment involve a great deal of coordination of sensing and signal transduction. This regulation can be achieved through several mechanisms, including changes in carbon metabolism, oxygen supply and/or overproduction of reactive oxygen and nitrogen species. Recently, the cycling of amino acids observed between the plant and bacteroid fractions suggests a new and important regulatory mechanism involved in nodule responses. Most of the recent transcriptional findings are consistent with the earlier biochemical and physiological reports. Current research revealed unique advances for nodule metabolism, especially on the regulation of asparagine synthetase gene expression and the control of asparagine (ASN) to N2 fixing activity. A large amount of ASN is found accumulating in the root nodules of the symbiotic plants under restricted environments, such as drought, salinity and nutrient deficiency. Exceptionally, ASN phloem feeding has resulted in an increased concentration of the ASN amide in nodules followed by a remarkable decrease in nodule activity. In this review, recent progress concerning the possible role of ASN in whole-plant-based down-regulation of symbiotic N2 fixation will be reviewed.

  8. Identifying abnormalities in symbiotic development between Trifolium spp. and Rhizobium leguminosarum bv. trifolii leading to sub-optimal and ineffective nodule phenotypes

    PubMed Central

    Melino, V. J.; Drew, E. A.; Ballard, R. A.; Reeve, W. G.; Thomson, G.; White, R. G.; O'Hara, G. W.

    2012-01-01

    Background and Aims Legumes overcome nitrogen limitations by entering into a mutualistic symbiosis with N2-fixing bacteria (rhizobia). Fully compatible associations (effective) between Trifolium spp. and Rhizobium leguminosarum bv. trifolii result from successful recognition of symbiotic partners in the rhizosphere, root hair infection and the formation of nodules where N2-fixing bacteroids reside. Poorly compatible associations can result in root nodule formation with minimal (sub-optimal) or no (ineffective) N2-fixation. Despite the abundance and persistence of strains in agricultural soils which are poorly compatible with the commercially grown clover species, little is known of how and why they fail symbiotically. The aims of this research were to determine the morphological aberrations occurring in sub-optimal and ineffective clover nodules and to determine whether reduced bacteroid numbers or reduced N2-fixing activity is the main cause for the Sub-optimal phenotype. Methods Symbiotic effectiveness of four Trifolium hosts with each of four R. leguminosarum bv. trifolii strains was assessed by analysis of plant yields and nitrogen content; nodule yields, abundance, morphology and internal structure; and bacteroid cytology, quantity and activity. Key Results Effective nodules (Nodule Function 83–100 %) contained four developmental zones and N2-fixing bacteroids. In contrast, Sub-optimal nodules of the same age (Nodule Function 24–57 %) carried prematurely senescing bacteroids and a small bacteroid pool resulting in reduced shoot N. Ineffective-differentiated nodules carried bacteroids aborted at stage 2 or 3 in differentiation. In contrast, bacteroids were not observed in Ineffective-vegetative nodules despite the presence of bacteria within infection threads. Conclusions Three major responses to N2-fixation incompatibility between Trifolium spp. and R. l. trifolii strains were found: failed bacterial endocytosis from infection threads into plant cortical

  9. Are Symbiotic Methanotrophs Key Microbes for N Acquisition in Paddy Rice Root?

    PubMed Central

    Minamisawa, Kiwamu; Imaizumi-Anraku, Haruko; Bao, Zhihua; Shinoda, Ryo; Okubo, Takashi; Ikeda, Seishi

    2016-01-01

    The relationships between biogeochemical processes and microbial functions in rice (Oryza sativa) paddies have been the focus of a large number of studies. A mechanistic understanding of methane–nitrogen (CH4–N) cycle interactions is a key unresolved issue in research on rice paddies. This minireview is an opinion paper for highlighting the mechanisms underlying the interactions between biogeochemical processes and plant-associated microbes based on recent metagenomic, metaproteomic, and isotope analyses. A rice symbiotic gene, relevant to rhizobial nodulation and mycorrhization in plants, likely accommodates diazotrophic methanotrophs or the associated bacterial community in root tissues under low-N fertilizer management, which may permit rice plants to acquire N via N2 fixation. The amount of N fixed in rice roots was previously estimated to be approximately 12% of plant N based on measurements of 15N natural abundance in a paddy field experiment. Community analyses also indicate that methanotroph populations in rice roots are susceptible to environmental conditions such as the microclimate of rice paddies. Therefore, CH4 oxidation by methanotrophs is a driving force in shaping bacterial communities in rice roots grown in CH4-rich environments. Based on these findings, we propose a hypothesis with unanswered questions to describe the interplay between rice plants, root microbiomes, and their biogeochemical functions (CH4 oxidation and N2 fixation). PMID:26960961

  10. Key role of symbiotic dinitrogen fixation in tropical forest secondary succession

    NASA Astrophysics Data System (ADS)

    Batterman, Sarah A.; Hedin, Lars O.; van Breugel, Michiel; Ransijn, Johannes; Craven, Dylan J.; Hall, Jefferson S.

    2013-10-01

    Forests contribute a significant portion of the land carbon sink, but their ability to sequester CO2 may be constrained by nitrogen, a major plant-limiting nutrient. Many tropical forests possess tree species capable of fixing atmospheric dinitrogen (N2), but it is unclear whether this functional group can supply the nitrogen needed as forests recover from disturbance or previous land use, or expand in response to rising CO2 (refs 6, 8). Here we identify a powerful feedback mechanism in which N2 fixation can overcome ecosystem-scale deficiencies in nitrogen that emerge during periods of rapid biomass accumulation in tropical forests. Over a 300-year chronosequence in Panama, N2-fixing tree species accumulated carbon up to nine times faster per individual than their non-fixing neighbours (greatest difference in youngest forests), and showed species-specific differences in the amount and timing of fixation. As a result of fast growth and high fixation, fixers provided a large fraction of the nitrogen needed to support net forest growth (50,000kg carbon per hectare) in the first 12years. A key element of ecosystem functional diversity was ensured by the presence of different N2-fixing tree species across the entire forest age sequence. These findings show that symbiotic N2 fixation can have a central role in nitrogen cycling during tropical forest stand development, with potentially important implications for the ability of tropical forests to sequester CO2.

  11. Key role of symbiotic dinitrogen fixation in tropical forest secondary succession.

    PubMed

    Batterman, Sarah A; Hedin, Lars O; van Breugel, Michiel; Ransijn, Johannes; Craven, Dylan J; Hall, Jefferson S

    2013-10-10

    Forests contribute a significant portion of the land carbon sink, but their ability to sequester CO2 may be constrained by nitrogen, a major plant-limiting nutrient. Many tropical forests possess tree species capable of fixing atmospheric dinitrogen (N2), but it is unclear whether this functional group can supply the nitrogen needed as forests recover from disturbance or previous land use, or expand in response to rising CO2 (refs 6, 8). Here we identify a powerful feedback mechanism in which N2 fixation can overcome ecosystem-scale deficiencies in nitrogen that emerge during periods of rapid biomass accumulation in tropical forests. Over a 300-year chronosequence in Panama, N2-fixing tree species accumulated carbon up to nine times faster per individual than their non-fixing neighbours (greatest difference in youngest forests), and showed species-specific differences in the amount and timing of fixation. As a result of fast growth and high fixation, fixers provided a large fraction of the nitrogen needed to support net forest growth (50,000 kg carbon per hectare) in the first 12 years. A key element of ecosystem functional diversity was ensured by the presence of different N2-fixing tree species across the entire forest age sequence. These findings show that symbiotic N2 fixation can have a central role in nitrogen cycling during tropical forest stand development, with potentially important implications for the ability of tropical forests to sequester CO2.

  12. Do symbiotic bacteria subvert host immunity?

    PubMed

    Hooper, Lora V

    2009-05-01

    The mammalian intestine is home to dense and complex indigenous bacterial communities. Most of these bacteria establish beneficial symbiotic relationships with their hosts, making important contributions to host metabolism and digestive efficiency. The vast numbers of intestinal bacteria and their proximity to host tissues raise the question of how symbiotic host-bacterial relationships are established without eliciting potentially harmful immune responses. In light of the varied ways in which pathogenic bacteria manipulate host immunity, this Opinion article explores the role of immune suppression, subversion and evasion in the establishment of symbiotic host-bacterial associations.

  13. Outbursts in Symbiotic Binaries

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Keyes, Charles

    2005-01-01

    A major question for symbiotic stars concerns the nature and cause of their outbursts. A small subset of symbiotics, the slow novae are fairly well established as thermonuclear events that last on the order of decades. The several symbiotic recurrent novae, which are much shorter and last on the order of months, are also thought to be thermonuclear runaways. Yet the majority of symbiotics are neither slow novae nor recurrent novae. These are the so-called classical symbiotics, many of which show outbursts whose cause is not well understood. In some cases, jets are produced in association with an outburst, therefore an investigation into the causes of outbursts will yield important insights into the production of collimated outflows. To investigate the cause and nature of classical symbiotic outbursts, we initiated a program of multiwavelength observations of these events. In FUSE Cycle 2, we obtained six observational epochs of the 2000-2002 classic symbiotic outburst in the first target of our campaign - class prototype, Z Andromedae. That program was part of a coordinated multi-wavelength Target-of-Opportunity (TOO) campaign with FUSE, XMM, Chandra, MERLIN, the VLA, and ground-based spectroscopic and high time-resolution photometric observations. Our campaign proved the concept, utility, and need for coordinated multi-wavelength observations in order to make progress in understanding the nature of the outburst mechanisms in symbiotic stars. Indeed, the FUSE data were the cornerstone of this project

  14. Models of symbiotic stars

    NASA Technical Reports Server (NTRS)

    Friedjung, Michael

    1993-01-01

    One of the most important features of symbiotic stars is the coexistence of a cool spectral component that is apparently very similar to the spectrum of a cool giant, with at least one hot continuum, and emission lines from very different stages of ionization. The cool component dominates the infrared spectrum of S-type symbiotics; it tends to be veiled in this wavelength range by what appears to be excess emission in D-type symbiotics, this excess usually being attributed to circumstellar dust. The hot continuum (or continua) dominates the ultraviolet. X-rays have sometimes also been observed. Another important feature of symbiotic stars that needs to be explained is the variability. Different forms occur, some variability being periodic. This type of variability can, in a few cases, strongly suggest the presence of eclipses of a binary system. One of the most characteristic forms of variability is that characterizing the active phases. This basic form of variation is traditionally associated in the optical with the veiling of the cool spectrum and the disappearance of high-ionization emission lines, the latter progressively appearing (in classical cases, reappearing) later. Such spectral changes recall those of novae, but spectroscopic signatures of the high-ejection velocities observed for novae are not usually detected in symbiotic stars. However, the light curves of the 'symbiotic nova' subclass recall those of novae. We may also mention in this connection that radio observations (or, in a few cases, optical observations) of nebulae indicate ejection from symbiotic stars, with deviations from spherical symmetry. We shall give a historical overview of the proposed models for symbiotic stars and make a critical analysis in the light of the observations of symbiotic stars. We describe the empirical approach to models and use the observational data to diagnose the physical conditions in the symbiotics stars. Finally, we compare the results of this empirical

  15. Spectrophotometry of Symbiotic Stars

    NASA Astrophysics Data System (ADS)

    Boyd, David

    2017-06-01

    Symbiotic stars are fascinating objects - complex binary systems comprising a cool red giant star and a small hot object, often a white dwarf, both embedded in a nebula formed by a wind from the giant star. UV radiation from the hot star ionises the nebula producing a range of emission lines. These objects have composite spectra with contributions from both stars plus the nebula and these spectra can change on many timescales. Being moderately bright, they lend themselves well to amateur spectroscopy. This paper describes the symbiotic star phenomenon, shows how spectrophotometry can be used to extract astrophysically useful information about the nature of these systems, and gives results for three symbiotic stars based on the author's observations.

  16. Population genomics of the symbiotic plasmids of sympatric nitrogen-fixing Rhizobium species associated with Phaseolus vulgaris.

    PubMed

    Pérez Carrascal, Olga M; VanInsberghe, David; Juárez, Soledad; Polz, Martin F; Vinuesa, Pablo; González, Víctor

    2016-09-01

    Cultivated common beans are the primary protein source for millions of people around the world who subsist on low-input agriculture, enabled by the symbiotic N2 -fixation these legumes perform in association with rhizobia. Within a single agricultural plot, multiple Rhizobium species can nodulate bean roots, but it is unclear how genetically isolated these species remain in sympatry. To better understand this issue, we sequenced and compared the genomes of 33 strains isolated from the rhizosphere and root nodules of a particular bean variety grown in the same agricultural plot. We found that the Rhizobium species we observed coexist with low genetic recombination across their core genomes. Accessory plasmids thought to be necessary for the saprophytic lifestyle in soil show similar levels of genetic isolation, but with higher rates of recombination than the chromosomes. However, the symbiotic plasmids are extremely similar, with high rates of recombination and do not appear to have co-evolved with the chromosome or accessory plasmids. Therefore, while Rhizobium species are genetically isolated units within the microbial community, a common symbiotic plasmid allows all Rhizobium species to engage in symbiosis with the same host in a single agricultural plot. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  17. Speciation and symbiotic dinoflagellates.

    PubMed

    Blank, R J; Trench, R K

    1985-08-16

    Morphometric analyses based on three-dimensional reconstruction of the nuclei of four different strains of the symbiotic dinoflagellate Symbiodinium microadriaticum, the algae that inhabit corals, giant clams, and other marine invertebrates, revealed marked differences in chromosome numbers and chromosome volumes. The differences are not consistent with different ploidy states within the same species, but can most easily be interpreted as indicating different species.

  18. Association of nitrogen fixation to water use efficiency and yield traits of peanut

    USDA-ARS?s Scientific Manuscript database

    Improvement of N2 fixation might be an effective strategy in peanut breeding for high yield under drought stress conditions. However, under water limited conditions peanut varieties having high water-use efficiency (WUE) are favorable. A pot experiment was conducted under greenhouse conditions at ...

  19. Symbiotic Origin of Aging.

    PubMed

    Greenberg, Edward F; Vatolin, Sergei

    2017-09-25

    Normally aging cells are characterized by an unbalanced mitochondrial dynamic skewed toward punctate mitochondria. Genetic and pharmacological manipulation of mitochondrial fission/fusion cycles can contribute to both accelerated and decelerated cellular or organismal aging. In this work, we connect these experimental data with the symbiotic theory of mitochondrial origin to generate new insight into the evolutionary origin of aging. Mitochondria originated from autotrophic α-proteobacteria during an ancient endosymbiotic event early in eukaryote evolution. To expand beyond individual host cells, dividing α-proteobacteria initiated host cell lysis; apoptosis is a product of this original symbiont cell lytic exit program. Over the course of evolution, the host eukaryotic cell attenuated the harmful effect of symbiotic proto-mitochondria, and modern mitochondria are now functionally interdependent with eukaryotic cells; they retain their own circular genomes and independent replication timing. In nondividing differentiated or multipotent eukaryotic cells, intracellular mitochondria undergo repeated fission/fusion cycles, favoring fission as organisms age. The discordance between cellular quiescence and mitochondrial proliferation generates intracellular stress, eventually leading to a gradual decline in host cell performance and age-related pathology. Hence, aging evolved from a conflict between maintenance of a quiescent, nonproliferative state and the evolutionarily conserved propagation program driving the life cycle of former symbiotic organisms: mitochondria.

  20. Symbiotic potential and survival of native rhizobia kept on different carriers

    PubMed Central

    Ruíz-Valdiviezo, Víctor Manuel; Canseco, Lucía María Cristina Ventura; Suárez, Luis Antonio Castillo; Gutiérrez-Miceli, Federico Antonio; Dendooven, Luc; Rincón-Rosales, Reiner

    2015-01-01

    Native rhizobia are ideal for use as commercial legume inoculants. The characteristics of the carrier used to store the inoculants are important for the survival and symbiotic potential of the rhizobia. The objective of this study was to investigate the effects of peat (PEAT), perlite sugarcane bagasse (PSB), carboxymethyl cellulose plus starch (CMCS), and yeast extract mannitol supplemented with mannitol (YEMM) on the survival, nodulation potential and N2 fixation capacity of the native strains Sinorhizobium mexicanum ITTG R7T and Rhizobium calliandrae LBP2-1T and of the reference strain Rhizobium etli CFN42T. A factorial design (4 × 3) with four repetitions was used to determine the symbiotic potential of the rhizobial strains. The survival of the strains was higher for PEAT (46% for strain LBP2-1T, 167% for strain CFN42T and 219% for strain ITTG R7T) than for the other carriers after 240 days, except for CFN42T kept on CMCS (225%). All the strains kept on the different carriers effectively nodulated common bean, with the lowest number of nodules found (5 nodules) when CFN42T was kept on CMCS and with the highest number of nodules found (28 nodules) when ITTG R7T was kept on PSB. The nitrogenase activity was the highest for ITTG R7T kept on PEAT (4911 μmol C2H4 per fresh weight nodule h−1); however, no activity was found when the strains were kept on YEMM. Thus, the survival and symbiotic potential of the rhizobia depended on the carrier used to store them. PMID:26413054

  1. Symbiotic potential and survival of native rhizobia kept on different carriers.

    PubMed

    Ruíz-Valdiviezo, Víctor Manuel; Canseco, Lucía María Cristina Ventura; Suárez, Luis Antonio Castillo; Gutiérrez-Miceli, Federico Antonio; Dendooven, Luc; Rincón-Rosales, Reiner

    2015-01-01

    Native rhizobia are ideal for use as commercial legume inoculants. The characteristics of the carrier used to store the inoculants are important for the survival and symbiotic potential of the rhizobia. The objective of this study was to investigate the effects of peat (PEAT), perlite sugarcane bagasse (PSB), carboxymethyl cellulose plus starch (CMCS), and yeast extract mannitol supplemented with mannitol (YEMM) on the survival, nodulation potential and N2 fixation capacity of the native strains Sinorhizobium mexicanum ITTG R7(T) and Rhizobium calliandrae LBP2-1(T) and of the reference strain Rhizobium etli CFN42(T). A factorial design (4 × 3) with four repetitions was used to determine the symbiotic potential of the rhizobial strains. The survival of the strains was higher for PEAT (46% for strain LBP2-1(T), 167% for strain CFN42(T) and 219% for strain ITTG R7(T)) than for the other carriers after 240 days, except for CFN42(T) kept on CMCS (225%). All the strains kept on the different carriers effectively nodulated common bean, with the lowest number of nodules found (5 nodules) when CFN42(T) was kept on CMCS and with the highest number of nodules found (28 nodules) when ITTG R7(T) was kept on PSB. The nitrogenase activity was the highest for ITTG R7(T) kept on PEAT (4911 μmol C2H4 per fresh weight nodule h(-1)); however, no activity was found when the strains were kept on YEMM. Thus, the survival and symbiotic potential of the rhizobia depended on the carrier used to store them.

  2. Population control in symbiotic corals

    SciTech Connect

    Falkowski, P.G. ); Dubinsky, Z. ); Muscatine, L. ); McCloskey, L. )

    1993-10-01

    Stability in symbiotic association requires control of population growth between symbionts. The population density of zooxanthellae per unit surface area of most symbiotic corals is remarkably consistant. How is the population density of zooxanthellae maintained and what happens to the symbiotic association if the balance between algae and host is perturbed. The answers to these question, examined in this paper, provide a framework for understanding how the size of the component populations is controlled in symbiotic associations. The topic areas covered include the following: carbon economy in a symbiotic coral; effects of nutrient enrichment; the chemostat model of population control; the effects of exposure to ammonium levels. Ammonium ions and organic materials are the factors which maintain the density of zooxanthellae. 32 refs., 5 figs.

  3. Which role for nitric oxide in symbiotic N2-fixing nodules: toxic by-product or useful signaling/metabolic intermediate?

    PubMed Central

    Boscari, Alexandre; Meilhoc, Eliane; Castella, Claude; Bruand, Claude; Puppo, Alain; Brouquisse, Renaud

    2013-01-01

    The interaction between legumes and rhizobia leads to the establishment of a symbiotic relationship characterized by the formation of new organs called nodules, in which bacteria have the ability to fix atmospheric nitrogen (N2) via the nitrogenase activity. Significant nitric oxide (NO) production was evidenced in the N2-fixing nodules suggesting that it may impact the symbiotic process. Indeed, NO was shown to be a potent inhibitor of nitrogenase activity and symbiotic N2 fixation. It has also been shown that NO production is increased in hypoxic nodules and this production was supposed to be linked – via a nitrate/NO respiration process – with improved capacity of the nodules to maintain their energy status under hypoxic conditions. Other data suggest that NO might be a developmental signal involved in the induction of nodule senescence. Hence, the questions were raised of the toxic effects versus signaling/metabolic functions of NO, and of the regulation of NO levels compatible with nitrogenase activity. The present review analyses the different roles of NO in functioning nodules, and discusses the role of plant and bacterial (flavo)hemoglobins in the control of NO level in nodules. PMID:24130563

  4. THE THERAPEUTIC USE OF SYMBIOTICS

    PubMed Central

    FLESCH, Aline Gamarra Taborda; POZIOMYCK, Aline Kirjner; DAMIN, Daniel De Carvalho

    2014-01-01

    Introduction Functional foods are health promoters and their use is associated with reduced risk of chronic degenerative and non-transmissible diseases. Examples are symbiotic. The association of one (or more) probiotic with a one (or more) prebiotic is called symbiotic, being the prebiotics complementary and probiotics synergistic, thus presenting a multiplicative factor on their individual actions. Objective To assess the evidences on the benefits of the use of symbiotics in the treatment of clinical and surgical situations. Methods The headings symbiotic, probiotic and prebiotic were searched in Pubmed/Medline in the last 15 years, and were selected 25 articles, used for database. Results The use of symbiotic may promote an increase in the number of bifidobacteria, glycemic control, reduction of blood cholesterol, balancing the intestinal flora which aids in reducing constipation and/or diarrhea, improves intestinal permeability and stimulation of the immune system. Clinical indications for these products has been expanded, in order to maximize the individual's physiological functions to provide greater. So, with the high interest in the clinical and nutritional control of disease, many studies have been conducted demonstrating the effectiveness of using symbiotic in improving and/or preventing various and/or symptoms of gastrointestinal diseases. Conclusion Symbiotic behave differently and positively in various pathological situations. PMID:25184774

  5. Biogeography of symbiotic and other endophytic bacteria isolated from medicinal Glycyrrhiza species in China.

    PubMed

    Li, Li; Sinkko, Hanna; Montonen, Leone; Wei, Gehong; Lindström, Kristina; Räsänen, Leena A

    2012-01-01

    A total of 159 endophytic bacteria were isolated from surface-sterilized root nodules of wild perennial Glycyrrhiza legumes growing on 40 sites in central and northwestern China. Amplified fragment length polymorphism (AFLP) genomic fingerprinting and sequencing of partial 16S rRNA genes revealed that the collection mainly consisted of Mesorhizobium, Rhizobium, Sinorhizobium, Agrobacterium and Paenibacillus species. Based on symbiotic properties with the legume hosts Glycyrrhiza uralensis and Glycyrrhiza glabra, we divided the nodulating species into true and sporadic symbionts. Five distinct Mesorhizobium groups represented true symbionts of the host plants, the majority of strains inducing N2-fixing nodules. Sporadic symbionts consisted of either species with infrequent occurrence (Rhizobium galegae, Rhizobium leguminosarum) or species with weak (Sinorhizobium meliloti, Rhizobium gallicum) or no N2 fixation ability (Rhizobium giardinii, Rhizobium cellulosilyticum, Phyllobacterium sp.). Multivariate analyses revealed that the host plant species and geographic location explained only a small part (14.4%) of the total variation in bacterial AFLP patterns, with the host plant explaining slightly more (9.9%) than geography (6.9%). However, strains isolated from G. glabra were clearly separated from those from G. uralensis, and strains obtained from central China were well separated from those originating from Xinjiang in the northwest, indicating both host preference and regional endemism.

  6. Nodule morphology, symbiotic specificity and association with unusual rhizobia are distinguishing features of the genus Listia within the Southern African crotalarioid clade Lotononis s.l.

    PubMed

    Ardley, Julie K; Reeve, Wayne G; O'Hara, Graham W; Yates, Ron J; Dilworth, Michael J; Howieson, John G

    2013-07-01

    The legume clade Lotononis sensu lato (s.l.; tribe Crotalarieae) comprises three genera: Listia, Leobordea and Lotononis sensu stricto (s.s.). Listia species are symbiotically specific and form lupinoid nodules with rhizobial species of Methylobacterium and Microvirga. This work investigated whether these symbiotic traits were confined to Listia by determining the ability of rhizobial strains isolated from species of Lotononis s.l. to nodulate Listia, Leobordea and Lotononis s.s. hosts and by examining the morphology and structure of the resulting nodules. Rhizobia were characterized by sequencing their 16S rRNA and nodA genes. Nodulation and N2 fixation on eight taxonomically diverse Lotononis s.l. species were determined in glasshouse trials. Nodules of all hosts, and the process of infection and nodule initiation in Listia angolensis and Listia bainesii, were examined by light microscopy. Rhizobia associated with Lotononis s.l. were phylogenetically diverse. Leobordea and Lotononis s.s. isolates were most closely related to Bradyrhizobium spp., Ensifer meliloti, Mesorhizobium tianshanense and Methylobacterium nodulans. Listia angolensis formed effective nodules only with species of Microvirga. Listia bainesii nodulated only with pigmented Methylobacterium. Five lineages of nodA were found. Listia angolensis and L. bainesii formed lupinoid nodules, whereas nodules of Leobordea and Lotononis s.s. species were indeterminate. All effective nodules contained uniformly infected central tissue. Listia angolensis and L. bainesii nodule initials occurred on the border of the hypocotyl and along the tap root, and nodule primordia developed in the outer cortical layer. Neither root hair curling nor infection threads were seen. Two specificity groups occur within Lotononis s.l.: Listia species are symbiotically specific, while species of Leobordea and Lotononis s.s. are generally promiscuous and interact with rhizobia of diverse chromosomal and symbiotic lineages. The

  7. Nodule morphology, symbiotic specificity and association with unusual rhizobia are distinguishing features of the genus Listia within the southern African crotalarioid clade Lotononis s.l.

    PubMed Central

    Ardley, Julie K.; Reeve, Wayne G.; O'Hara, Graham W.; Yates, Ron J.; Dilworth, Michael J.; Howieson, John G.

    2013-01-01

    Background and Aims The legume clade Lotononis sensu lato (s.l.; tribe Crotalarieae) comprises three genera: Listia, Leobordea and Lotononis sensu stricto (s.s.). Listia species are symbiotically specific and form lupinoid nodules with rhizobial species of Methylobacterium and Microvirga. This work investigated whether these symbiotic traits were confined to Listia by determining the ability of rhizobial strains isolated from species of Lotononis s.l. to nodulate Listia, Leobordea and Lotononis s.s. hosts and by examining the morphology and structure of the resulting nodules. Methods Rhizobia were characterized by sequencing their 16S rRNA and nodA genes. Nodulation and N2 fixation on eight taxonomically diverse Lotononis s.l. species were determined in glasshouse trials. Nodules of all hosts, and the process of infection and nodule initiation in Listia angolensis and Listia bainesii, were examined by light microscopy. Key Results Rhizobia associated with Lotononis s.l. were phylogenetically diverse. Leobordea and Lotononis s.s. isolates were most closely related to Bradyrhizobium spp., Ensifer meliloti, Mesorhizobium tianshanense and Methylobacterium nodulans. Listia angolensis formed effective nodules only with species of Microvirga. Listia bainesii nodulated only with pigmented Methylobacterium. Five lineages of nodA were found. Listia angolensis and L. bainesii formed lupinoid nodules, whereas nodules of Leobordea and Lotononis s.s. species were indeterminate. All effective nodules contained uniformly infected central tissue. Listia angolensis and L. bainesii nodule initials occurred on the border of the hypocotyl and along the tap root, and nodule primordia developed in the outer cortical layer. Neither root hair curling nor infection threads were seen. Conclusions Two specificity groups occur within Lotononis s.l.: Listia species are symbiotically specific, while species of Leobordea and Lotononis s.s. are generally promiscuous and interact with rhizobia of

  8. Multifrequency observations of symbiotic stars

    NASA Technical Reports Server (NTRS)

    Kenyon, Scott J.

    1988-01-01

    The discovery of symbiotic stars is described, and the results of multifrequency observations made during the past two decades are presented. Observational data identify symbiotic stars as long-period binary systems that can be divided into two basic physical classes: detached symbiotics containing a red giant (or a Mira variable), and semidetached symbiotics containing a lobe-filling red giant and a solar-type main sequence star. Three components are typically observed: (1) the cool giant component with an effective temperature of 2500-4000 K, which can be divided by the IR spectral classification into normal M giants (S-types) and heavily reddened Mira variables (D-types); (2) the hot companion displaying a bright blue continuum at UV wavelengths, which is sometimes also an X-ray source; and (3) a gaseous nebula enveloping the binary.

  9. Symbiotic systems: observations and theory

    NASA Astrophysics Data System (ADS)

    Luna, Gerardo

    2016-07-01

    Although there is wide concensus about the binary nature of symbiotic stars, the nature of their central engine, the structure of the accretion flow and the accretion rate are poorly known. Modern observatories are now providing, for the first time, direct information about the central source of power and how it is fueled. The detection of hard (E > 20 keV) X-ray emission from a handful of symbiotics indicates that some symbiotics accrete at a low enough rate for a ˜10^{8} K accretion-disk boundary layer to remain optically thin and generate hard X-rays. Such high temperature is possible if the white dwarf is massive; symbiotics could thus be SNIa progenitors, the pilars of the current cosmological paradigm.

  10. FRET-Mediated Long-Range Wavelength Transformation by Photoconvertible Fluorescent Proteins as an Efficient Mechanism to Generate Orange-Red Light in Symbiotic Deep Water Corals

    PubMed Central

    Bollati, Elena; Plimmer, Daniel; D’Angelo, Cecilia; Wiedenmann, Jörg

    2017-01-01

    Photoconvertible fluorescent proteins (pcRFPs) are a group of fluorophores that undergo an irreversible green-to-red shift in emission colour upon irradiation with near-ultraviolet (near-UV) light. Despite their wide application in biotechnology, the high-level expression of pcRFPs in mesophotic and depth-generalist coral species currently lacks a biological explanation. Additionally, reduced penetration of near-UV wavelengths in water poses the question whether light-driven photoconversion is relevant in the mesophotic zone, or whether a different mechanism is involved in the post-translational pigment modification in vivo. Here, we show in a long-term mesocosm experiment that photoconversion in vivo is entirely dependent on near-UV wavelengths. However, a near-UV intensity equivalent to the mesophotic underwater light field at 80 m depth is sufficient to drive the process in vitro, suggesting that photoconversion can occur near the lower distribution limits of these corals. Furthermore, live coral colonies showed evidence of efficient Förster Resonance Energy Transfer (FRET). Our simulated mesophotic light field maintained the pcRFP pool in a partially photoconverted state in vivo, maximising intra-tetrameric FRET and creating a long-range wavelength conversion system with higher quantum yield than other native RFPs. We hypothesise that efficient conversion of blue wavelengths, abundant at depth, into orange-red light could constitute an adaptation of corals to life in light-limited environments. PMID:28677653

  11. The transmission efficiency of tomato yellow leaf curl virus by the whitefly Bemisia tabaci is correlated with the presence of a specific symbiotic bacterium species.

    PubMed

    Gottlieb, Yuval; Zchori-Fein, Einat; Mozes-Daube, Netta; Kontsedalov, Svetlana; Skaljac, Marisa; Brumin, Marina; Sobol, Iris; Czosnek, Henryk; Vavre, Fabrice; Fleury, Frédéric; Ghanim, Murad

    2010-09-01

    Tomato yellow leaf curl virus (TYLCV) (Geminiviridae: Begomovirus) is exclusively vectored by the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). TYLCV transmission depends upon a 63-kDa GroEL protein produced by the vector's endosymbiotic bacteria. B. tabaci is a species complex comprising several genetically distinct biotypes that show different secondary-symbiont fauna. In Israel, the B biotype harbors Hamiltonella, and the Q biotype harbors Wolbachia and Arsenophonus. Both biotypes harbor Rickettsia and Portiera (the obligatory primary symbionts). The aim of this study was to determine which B. tabaci symbionts are involved in TYLCV transmission using B. tabaci populations collected in Israel. Virus transmission assays by B. tabaci showed that the B biotype efficiently transmits the virus, while the Q biotype scarcely transmits it. Yeast two-hybrid and protein pulldown assays showed that while the GroEL protein produced by Hamiltonella interacts with TYLCV coat protein, GroEL produced by Rickettsia and Portiera does not. To assess the role of Wolbachia and Arsenophonus GroEL proteins (GroELs), we used an immune capture PCR (IC-PCR) assay, employing in vivo- and in vitro-synthesized GroEL proteins from all symbionts and whitefly artificial feeding through membranes. Interaction between GroEL and TYLCV was found to occur in the B biotype, but not in the Q biotype. This assay further showed that release of virions protected by GroEL occurs adjacent to the primary salivary glands. Taken together, the GroEL protein produced by Hamiltonella (present in the B biotype, but absent in the Q biotype) facilitates TYLCV transmission. The other symbionts from both biotypes do not seem to be involved in transmission of this virus.

  12. Dihydrogen catalysis: a degradation mechanism for N2-fixation intermediates.

    PubMed

    Asatryan, Rubik; Bozzelli, Joseph W; Ruckenstein, Eli

    2012-11-29

    Molecular hydrogen plays multiple roles in activation of nitrogen. Among others, it inhibits the overall process of N(2)-reduction catalyzed by nitrogenase enzyme. The H(2)-assisted dehydrogenation and the H-atom transfer reactions (called dihydrogen catalysis, DHC) are suggested as possible mechanisms for the degradation and removal of potential intermediates formed during the reduction of nitrogen. Several iron-organic model reactions associated with the core stereospecific reaction (cis-N(2)H(2) + H(2) → N(2) + H(2) + H(2)) are examined using a comprehensive density functional theory and ab initio analysis of the corresponding potential energy surfaces. A variety of energetically feasible decomposition pathways are identified for the DHC-oxidation of iron-bound [N(x)H(y)]-species. A liberated diazene intermediate (HN═NH) is suggested to interact in situ with two proximal hydridic H-atoms of an activated (hydrided) Fe-catalyst to produce N(2) and H(2) with a low or even no activation barrier. The majority of identified pathways are shown to be highly sensitive to the electronic environment and spin configuration of metallocomplexes. The H(2)-assisted transport of a single H-atom from a bound [N(x)H(y)] moiety to either the proximal or distal (Fe, S or N) active centers of a catalyst provides an alternative degradation (interconversion) mechanism for the relevant intermediates. The two types of molecular hydrogen-assisted reactions highlighted above, namely, the H(2)-assisted dehydrogenation and the transport of H-atoms, suggest theoretical interpretations for the observed H(2)-inhibition of N(2) activation and HD formation (in the presence of D(2)). The DHC reactions of various [N(x)H(y)] moieties are expected to play significant roles in the industrial high-pressure hydrodenitrification and other catalytic processes involving the metabolism of molecular hydrogen.

  13. Carbon budgets in symbiotic associations

    SciTech Connect

    Muscatine, L.; Falkowski, P.G.; Dubinsky, Z.

    1983-01-01

    Methods are described which permit the estimation of daily budgets for photosynthetically fixed carbon in any alga-invertebrate symbiosis. Included is a method for estimating total daily translocation which does not involve the use of C-14. A daily carbon budget for a shallow water symbiotic reef coral is presented.

  14. Discussion on selected symbiotic stars

    NASA Technical Reports Server (NTRS)

    Viotti, Roberto; Hack, Margherita

    1993-01-01

    Because of its large variety of aspects, the symbiotic phenomenon is not very suitable for a statistical treatment. It is also not clear whether symbiotic stars really represent a homogeneous group of astrophysical objects or a collection of objects of different natures but showing similar phenomena. However we are especially interested in the symbiotic phenomenon, i.e., in those physical processes occurring in the atmosphere of each individual object and in their time dependence. Such a research can be performed through the detailed analysis of individual objects. This study should be done for a time long enough to cover all the different phases of their activity, in all the spectral ranges. Since the typical time scale of the symbiotic phenomena is up to several years and decades, this represents a problem since, for instance, making astronomy outside the visual region is a quite new field of research. It was a fortunate case that a few symbiotic stars (Z And, AG Dra, CH Cyg, AX Per, and PU Vul) had undergone remarkable light variations (or 'outbursts') in recent years, which could have been followed in the space ultraviolet with IUE, and simultaneously in the optical and IR with ground-based telescopes. But, in general, the time coverage of most of the symbiotic objects is too short to have a complete picture of their behavior. In this regard, one should recall Mayall's remark about the light curve of Z And: 'Z Andromedae is another variable that shows it will require several hundred years of observations before a good analysis can be made of its variations'. This pessimistic remark should be considered as a note of caution for those involved in the interpretation of the observations. We shall discuss a number of individual symbiotic stars for which the amount of observational data is large enough to draw a rather complete picture of their general behavior and to make consistent models. We shall especially illustrate the necessary steps toward an empirical model

  15. Unique symbiotic viruses in plants: Endornaviruses.

    PubMed

    Fukuhara, Toshiyuki

    2015-01-01

    Linear double-stranded RNAs (dsRNAs) of about 15 kbp in length are often found from healthy plants, such as bell pepper and rice plants. Nucleotide sequencing and phylogenetic analyses reveal that these dsRNAs are not transcribed from host genomic DNAs, encode a single long open reading frame (ORF) with a viral RNA-dependent RNA polymerase domain, and contain a site-specific nick in the 5' region of their coding strands. Consequently the International Committee on Taxonomy of Viruses has approved that these dsRNAs are viruses forming a distinct taxon, the family Endornaviridae the genus Endornavirus. Endornaviruses have common properties that differ from those of conventional viruses: they have no obvious effect on the phenotype of their host plants, and they are efficiently transmitted to the next generation via both pollen and ova, but their horizontal transfer to other plants has never been proven. Conventional single-stranded RNA viruses, such as cucumber mosaic virus, propagate hugely and systemically in host plants to sometime kill their hosts eventually and transmit horizontally (infect to other plants). In contrast, copy numbers of endornaviruses are low and constant (about 100 copies/cell), and they symbiotically propagate with host plants and transmit vertically. Therefore, endornaviruses are unique plant viruses with symbiotic properties.

  16. On Predation of Symbiotic Systems

    NASA Astrophysics Data System (ADS)

    Chatterjee, Samrat; Venturino, Ezio

    2011-09-01

    In this study we investigate an ecosystem in which a predator population hunts two different prey who live in symbiosis. Under the assumptions we take, the effect of the predators on the symbiotic system does not reveal any substantial change in the system dynamics, except that in sufficient numbers they can drive the ecosystem to extinction, although the prey in their absence might grow unboundedly.

  17. Effect of Light Intensity on Efficiency of Carbon Dioxide and Nitrogen Reduction in Pisum sativum L. 1

    PubMed Central

    Bethlenfalvay, Gabor J.; Phillips, Donald A.

    1977-01-01

    Photosynthetic efficiency, primary productivity, and N2 reduction were determined in peas (Pisum sativum L. var. Alaska) grown at light intensities ranging from severely limiting to saturating. Plants grown under higher light intensities showed greater carboxylation and light capture potential and higher rates of net C exchange. Uptake of N2, computed from measured C2H2 reduction and H2 evolution rates, also increased with growth light intensity, while the previously proposed relative efficiency of N2 fixation, based on these same parameters, declined. The plot of N/C ratios (total nitrogen content/plant dry weight) increased hyperbolically with light intensity, and the plot of N2/CO2 uptake ratios (N2 uptake rate/net CO2 uptake rate) increased linearly. Both plots extrapolated to the light compensation point. The data indicate that the relative efficiency of N2 fixation is not necessarily correlated with maximum plant productivity and that evaluation of a plant's capacity to reduce N2 is related directly to concurrent CO2 reduction. A measure of whole plant N2 fixation efficiency based on the N2/CO2 uptake ratio is proposed. PMID:16660203

  18. AG Draconis - a symbiotic mystery

    NASA Astrophysics Data System (ADS)

    Galis, R.; Hric, L.; Smelcer, L.

    2015-02-01

    Symbiotic system AG Draconis regularly undergoes quiescent and active stages which consist of the series of individual outbursts. The period analysis of new and historical photometric data, as well as radial velocities, confirmed the presence of the two periods. The longer one (~550 d) is related to the orbital motion and the shorter one (~355 d) could be due to pulsation of the cool component of AG Dra. In addition, the active stages change distinctively, but the outbursts are repeated with periods from 359 - 375 d.

  19. Molecular Basis of Symbiotic Promiscuity

    PubMed Central

    Perret, Xavier; Staehelin, Christian; Broughton, William J.

    2000-01-01

    Eukaryotes often form symbioses with microorganisms. Among these, associations between plants and nitrogen-fixing bacteria are responsible for the nitrogen input into various ecological niches. Plants of many different families have evolved the capacity to develop root or stem nodules with diverse genera of soil bacteria. Of these, symbioses between legumes and rhizobia (Azorhizobium, Bradyrhizobium, Mesorhizobium, and Rhizobium) are the most important from an agricultural perspective. Nitrogen-fixing nodules arise when symbiotic rhizobia penetrate their hosts in a strictly controlled and coordinated manner. Molecular codes are exchanged between the symbionts in the rhizosphere to select compatible rhizobia from pathogens. Entry into the plant is restricted to bacteria that have the “keys” to a succession of legume “doors”. Some symbionts intimately associate with many different partners (and are thus promiscuous), while others are more selective and have a narrow host range. For historical reasons, narrow host range has been more intensively investigated than promiscuity. In our view, this has given a false impression of specificity in legume-Rhizobium associations. Rather, we suggest that restricted host ranges are limited to specific niches and represent specialization of widespread and more ancestral promiscuous symbioses. Here we analyze the molecular mechanisms governing symbiotic promiscuity in rhizobia and show that it is controlled by a number of molecular keys. PMID:10704479

  20. Multi Agent Systems with Symbiotic Learning and Evolution using GNP

    NASA Astrophysics Data System (ADS)

    Eguchi, Toru; Hirasawa, Kotaro; Hu, Jinglu; Murata, Junichi

    Recently, various attempts relevant to Multi Agent Systems (MAS) which is one of the most promising systems based on Distributed Artificial Intelligence have been studied to control large and complicated systems efficiently. In these trends of MAS, Multi Agent Systems with Symbiotic Learning and Evolution named Masbiole has been proposed. In Masbiole, symbiotic phenomena among creatures are considered in the process of learning and evolution of MAS. So we can expect more flexible and sophisticated solutions than conventional MAS. In this paper, we apply Masbiole to Iterative Prisoner’s Dilemma Games (IPD Games) using Genetic Network Programming (GNP) which is a newly developed evolutionary computation method for constituting agents. Some characteristics of Masbiole using GNP in IPD Games are clarified.

  1. Training Feedforward Neural Networks Using Symbiotic Organisms Search Algorithm

    PubMed Central

    Wu, Haizhou; Luo, Qifang

    2016-01-01

    Symbiotic organisms search (SOS) is a new robust and powerful metaheuristic algorithm, which stimulates the symbiotic interaction strategies adopted by organisms to survive and propagate in the ecosystem. In the supervised learning area, it is a challenging task to present a satisfactory and efficient training algorithm for feedforward neural networks (FNNs). In this paper, SOS is employed as a new method for training FNNs. To investigate the performance of the aforementioned method, eight different datasets selected from the UCI machine learning repository are employed for experiment and the results are compared among seven metaheuristic algorithms. The results show that SOS performs better than other algorithms for training FNNs in terms of converging speed. It is also proven that an FNN trained by the method of SOS has better accuracy than most algorithms compared. PMID:28105044

  2. Symbiotic structures to significantly enhance space missions

    NASA Astrophysics Data System (ADS)

    Williams, Andrew D.; Diaz-Aguado, Millan; Arritt, Brandon J.

    2007-04-01

    The Department of Defense is actively pursuing a Responsive Space capability that will dramatically reduce the cost and time associated with getting a payload into space. In order to enable that capability, our space systems must be modular and flexible to cover a wide range of missions, configurations, duty cycles, and orbits. This places requirements on the entire satellite infrastructure: payloads, avionics, electrical harnessing, structure, thermal management system, etc. The Integrated Structural Systems Team at the Air Force Research Laboratory, Space Vehicles Directorate, has been tasked with developing structural and thermal solutions that will enable a Responsive Space capability. This paper details a "symbiotic" solution where thermal management functionality is embedded within the structure of the satellite. This approach is based on the flight proven and structurally efficient isogrid architecture. In our rendition, the ribs serve as fluidic passages for thermal management, and passively activated valves are used to control flow to the individual components. As the paper will explain, our analysis has shown this design to be structurally efficient and thermally responsive to a wide range of potential satellite missions, payloads, configurations, and orbits.

  3. Influence of the size of indigenous rhizobial populations on establishment and symbiotic performance of introduced rhizobia on field-grown legumes.

    PubMed

    Thies, J E; Singleton, P W; Bohlool, B B

    1991-01-01

    significantly increased 85% of the time. Yield was significantly increased in only 6% of the observations when numbers of indigenous rhizobia were greater than 10 cells g of soil. A significant response to N application, significant increases in nodule parameters, and greater than 50% nodule occupancy by inoculant rhizobia did not necessarily coincide with significant inoculation responses. No less than a doubling of nodule mass and 66% nodule occupancy by inoculant rhizobia were required to significantly increase the yield of inoculated crops over that of uninoculated crops. However, lack of an inoculation response was common even when inoculum strains occupied the majority of nodules. In these trials, the symbiotic yield of crops was, on average, only 88% of the maximum yield potential, as defined by the fertilizer N treatment. The difference between the yield of N-fertilized crops and that of N(2)-fixing crops indicates a potential for improving inoculation technology, the N(2) fixation capacity of rhizobial strains, and the efficiency of symbiosis. In this study, we show that the probability of enhancing yield with existing inoculation technology decreases dramatically with increasing numbers of indigenous rhizobia.

  4. Influence of the Size of Indigenous Rhizobial Populations on Establishment and Symbiotic Performance of Introduced Rhizobia on Field-Grown Legumes †

    PubMed Central

    Thies, Janice E.; Singleton, Paul W.; Bohlool, B. Ben

    1991-01-01

    significantly increased 85% of the time. Yield was significantly increased in only 6% of the observations when numbers of indigenous rhizobia were greater than 10 cells g of soil-1. A significant response to N application, significant increases in nodule parameters, and greater than 50% nodule occupancy by inoculant rhizobia did not necessarily coincide with significant inoculation responses. No less than a doubling of nodule mass and 66% nodule occupancy by inoculant rhizobia were required to significantly increase the yield of inoculated crops over that of uninoculated crops. However, lack of an inoculation response was common even when inoculum strains occupied the majority of nodules. In these trials, the symbiotic yield of crops was, on average, only 88% of the maximum yield potential, as defined by the fertilizer N treatment. The difference between the yield of N-fertilized crops and that of N2-fixing crops indicates a potential for improving inoculation technology, the N2 fixation capacity of rhizobial strains, and the efficiency of symbiosis. In this study, we show that the probability of enhancing yield with existing inoculation technology decreases dramatically with increasing numbers of indigenous rhizobia. PMID:16348393

  5. Circumstellar Dust in Symbiotic Novae

    NASA Astrophysics Data System (ADS)

    Jurkic, T.; Kotnik-Karuza, D.

    2015-12-01

    We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the near-IR photometry, ISO spectra and mid-IR interferometry. The dust properties were determined using the DUSTY code. A compact circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel shows the presence of an equatorially enhanced dust density during minimum obscuration. Obscuration events are explained by an increase in optical depth caused by the newly condensed dust. The mass loss rates are significantly higher than in intermediate-period single Miras but in agreement with longer-period O-rich AGB stars.

  6. IUE observations of symbiotic stars

    NASA Technical Reports Server (NTRS)

    Hack, M.

    1982-01-01

    The main photometric and spectroscopic characteristics in the ultraviolet and visual range of the most extensively studied symbiotic stars are reviewed. The main data obtained with IUE concern: (1) the determination of the shape of the UV continuum, which, in some cases, proves without doubt the presence of a hot companion; and the determination of the interstellar extinction by means of the lambda 2200 feature; (2) the measurement of emission lines, which enables us to derive the electron temperature and density of the circumstellar envelope, and, taken together with those lines observed in the visual, give more complete information on which spectroscopic mechanisms operate in the envelope; (3) the observation of absorption lines in the UV, which are present in just a few cases.

  7. Comparative phylogenomics of symbiotic associations.

    PubMed

    Delaux, Pierre-Marc

    2017-01-01

    89 I. 89 II. 90 III. 90 IV. 91 V. 92 VI. 93 References 93 SUMMARY: Understanding the genetic bases of complex traits has been a main challenge in biology for decades. Comparative phylogenomics offers an opportunity to identify candidate genes associated with these complex traits. This approach initially developed in prokaryotes consists in looking at shared coevolution between genes and traits. It thus requires a precise reconstruction of the trait evolution, a large genomic sampling in the clades of interest and an accurate definition of orthogroups. Recently, with the growing body of sequenced plant genomes, comparative genomics has been successfully applied to plants to study the widespread arbuscular mycorrhizal symbiosis. Here I will use these findings to illustrate the main principles of comparative phylogenomic approaches and propose directions to improve our understanding of symbiotic associations.

  8. ZZ Canis Minoris as a symbiotic star

    NASA Technical Reports Server (NTRS)

    Bopp, B. W.

    1984-01-01

    The H-aplha and Na I D-line regions of the M6 giant star ZZ Canis Minoris (ZZ CMi) were observed with the Kitt Peak coude feed telescope and a CCD detector. It is shown that ZZ CMi has similar spectroscopic and photoproperties to the symbiotic star EG And. The data are used to argue for the classification of ZZ CMi as a symbiotic star despite its current listing in the General Catalog of Variable Stars (GCVS) as a semi-regular variable. The infrared magnitudes of ZZ CMi and the known symbiotic stars are compared in a table.

  9. Evidence of Horizontal Transfer of Symbiotic Genes from a Bradyrhizobium japonicum Inoculant Strain to Indigenous Diazotrophs Sinorhizobium (Ensifer) fredii and Bradyrhizobium elkanii in a Brazilian Savannah Soil▿

    PubMed Central

    Barcellos, Fernando Gomes; Menna, Pâmela; da Silva Batista, Jesiane Stefânia; Hungria, Mariangela

    2007-01-01

    The importance of horizontal gene transfer (HGT) in the evolution and speciation of bacteria has been emphasized; however, most studies have focused on genes clustered in pathogenesis and very few on symbiosis islands. Both soybean (Glycine max [L.] Merrill) and compatible Bradyrhizobium japonicum and Bradyrhizobium elkanii strains are exotic to Brazil and have been massively introduced in the country since the early 1960s, occupying today about 45% of the cropped land. For the past 10 years, our group has obtained several isolates showing high diversity in morphological, physiological, genetic, and symbiotic properties in relation to the putative parental inoculant strains. In this study, parental strains and putative natural variants isolated from field-grown soybean nodules were genetically characterized in relation to conserved genes (by repetitive extragenic palindromic PCR using REP and BOX A1R primers, PCR-restriction fragment length polymorphism, and sequencing of the 16SrRNA genes), nodulation, and N2-fixation genes (PCR-RFLP and sequencing of nodY-nodA, nodC, and nifH genes). Both genetic variability due to adaptation to the stressful environmental conditions of the Brazilian Cerrados and HGT events were confirmed. One strain (S 127) was identified as an indigenous B. elkanii strain that acquired a nodC gene from the inoculant B. japonicum. Another one (CPAC 402) was identified as an indigenous Sinorhizobium (Ensifer) fredii strain that received the whole symbiotic island from the B. japonicum inoculant strain and maintained an extra copy of the original nifH gene. The results highlight the strategies that bacteria may commonly use to obtain ecological advantages, such as the acquisition of genes to establish effective symbioses with an exotic host legume. PMID:17308185

  10. A polarimetric survey of symbiotic stars

    NASA Technical Reports Server (NTRS)

    Schulte-Ladbeck, R. E.; Aspin, C.; Magalhaes, A. M.; Schwarz, H. E.

    1990-01-01

    Optical and near-infrared polarization observations of 24 symbiotic stars, 14 observed with polarimetry for the first time are presented. In combination with published data, it is found that about 50 percent of the symbiotics observed polarimetrically show evidence for intrinsic polarization. The results are discussed in the light of previous observations, and comments are made on the temporal variability and wavelength dependence of the polarization. Dust scattering is identified as the dominant mechanism producing polarization in symbiotic stars. While it cannot be excluded that some symbiotic systems are completely engulfed in their dust shells, the data indicate that the H-alpha emission line may originate from outside of the dust-scattering envelopes in some systems.

  11. Circumstellar dust in symbiotic novae

    NASA Astrophysics Data System (ADS)

    Jurkic, Tomislav; Kotnik-Karuza, Dubravka

    2015-08-01

    Physical properties of the circumstellar dust and associated physical mechanisms play an important role in understanding evolution of symbiotic binaries. We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the long-term near-IR photometry, infrared ISO spectra and mid-IR interferometry. Pulsation properties and long-term variabilities were found from the near-IR light curves. The dust properties were determined using the DUSTY code which solves the radiative transfer. No changes in pulsational parameters were found, but a long-term variations with periods of 20-25 years have been detected which cannot be attributed to orbital motion.Circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel showed the presence of an optically thin CS dust envelope and an optically thick dust region outside the line of sight, which was further supported by the detailed modelling using the 2D LELUYA code. Obscuration events in RR Tel were explained by an increase in optical depth caused by the newly condensed dust leading to the formation of a compact dust shell. HM Sge showed permanent obscuration and a presence of a compact dust shell with a variable optical depth. Scattering of the near-IR colours can be understood by a change in sublimation temperature caused by the Mira variability. Presence of large dust grains (up to 4 µm) suggests an increased grain growth in conditions of increased mass loss. The mass loss rates of up to 17·10-6 MSun/yr were significantly higher than in intermediate-period single Miras and in agreement with longer-period O-rich AGB stars.Despite the nova outburst, HM Sge remained enshrouded in dust with no significant dust destruction. The existence of unperturbed dust shell suggests a small influence of the hot component and strong dust shielding from the UV flux. By the use

  12. Light and the bioenergetics of a symbiotic coral

    SciTech Connect

    Falkowski, P.G.; Dubinsky, Z.; Muscatine, L.; Porter, J.W.

    1984-12-01

    Colonies of coral Stylophora pistillata growing at high light can obtain all the reduced carbon needed for animal respiration from photosynthesis by symbiotic zooxanthellae. In contrast, colonies in shaded reef areas must acquired 60% of their reduced carbon heterotrophically. More than 90% of the carbon fixed by zooxanthellae is translocated to the animal host in both light regimes, but very little is assimilated, apparently because the translocated products are deficient in nitrogen. Thus, the coral's overall growth efficiency is similar to that of aquatic herbivores that forage actively. 29 references, 2 figures, 1 table.

  13. Symbiotic Stars in X-rays

    NASA Technical Reports Server (NTRS)

    Luna, G. J. M.; Sokoloski, J. L.; Mukai, K.; Nelson, T.

    2014-01-01

    Until recently, symbiotic binary systems in which a white dwarf accretes from a red giant were thought to be mainly a soft X-ray population. Here we describe the detection with the X-ray Telescope (XRT) on the Swift satellite of 9 white dwarf symbiotics that were not previously known to be X-ray sources and one that was previously detected as a supersoft X-ray source. The 9 new X-ray detections were the result of a survey of 41 symbiotic stars, and they increase the number of symbiotic stars known to be X-ray sources by approximately 30%. Swift/XRT detected all of the new X-ray sources at energies greater than 2 keV. Their X-ray spectra are consistent with thermal emission and fall naturally into three distinct groups. The first group contains those sources with a single, highly absorbed hard component, which we identify as probably coming from an accretion-disk boundary layer. The second group is composed of those sources with a single, soft X-ray spectral component, which likely arises in a region where low-velocity shocks produce X-ray emission, i.e. a colliding-wind region. The third group consists of those sources with both hard and soft X-ray spectral components. We also find that unlike in the optical, where rapid, stochastic brightness variations from the accretion disk typically are not seen, detectable UV flickering is a common property of symbiotic stars. Supporting our physical interpretation of the two X-ray spectral components, simultaneous Swift UV photometry shows that symbiotic stars with harder X-ray emission tend to have stronger UV flickering, which is usually associated with accretion through a disk. To place these new observations in the context of previous work on X-ray emission from symbiotic stars, we modified and extended the alpha/beta/gamma classification scheme for symbiotic-star X-ray spectra that was introduced by Muerset et al. based upon observations with the ROSAT satellite, to include a new sigma classification for sources with

  14. QTL analysis of symbiotic nitrogen fixation in a black bean RIL population

    USDA-ARS?s Scientific Manuscript database

    Dry bean (Phaseolus vulgaris L) acquires nitrogen (N) from the atmosphere through symbiotic nitrogen fixation (SNF) but it has a low efficiency to fix nitrogen. The objective of this study is to map the genes controlling nitrogen fixation in common bean. A mapping population consisting of 122 recomb...

  15. Overview of the observations of symbiotic stars

    NASA Technical Reports Server (NTRS)

    Viotti, Roberto

    1993-01-01

    The term Symbiotic stars commonly denotes variable stars whose optical spectra simultaneously present a cool absorption spectrum (typically TiO absorption bands) and emission lines of high ionization energy. This term is now used for the category of variable stars with composite spectrum. The main spectral features of these objects are: (1) the presence of the red continuum typical of a cool star, (2) the rich emission line spectrum, and (3) the UV excess, frequently with the Balmer continuum in emission. In addition to the peculiar spectrum, the very irregular photometric and spectroscopic variability is the major feature of the symbiotic stars. Moreover, the light curve is basic to identify the different phases of activity in a symbiotic star. The physical mechanisms that cause the symbiotic phenomenon and its variety are the focus of this paper. An astronomical phenomenon characterized by a composite stellar spectrum with two apparently conflicting features, and large variability has been observed. Our research set out to find the origin of this behavior and, in particular, to identify and measure the physical mechanism(s) responsible for the observed phenomena.

  16. Effect of diseases on symbiotic systems.

    PubMed

    Tiwari, Pankaj Kumar; Sasmal, Sourav Kumar; Sha, Amar; Venturino, Ezio; Chattopadhyay, Joydev

    2017-09-01

    There are many species living in symbiotic communities. In this study, we analyzed models in which populations are in the mutualism symbiotic relations subject to a disease spreading among one of the species. The main goal is the characterization of symbiotic relations of coexisting species through their mutual influences on their respective carrying capacities, taking into account that this influence can be quite strong. The functional dependence of the carrying capacities reflects the fact that the correlations between populations cannot be realized merely through direct interactions, as in the usual predator-prey Lotka-Volterra model, but also through the influence of each species on the carrying capacities of the other one. Equilibria are analyzed for feasibility and stability, substantiated via numerical simulations, and global sensitivity analysis identifies the important parameters having a significant impact on the model dynamics. The infective growth rate and the disease-related mortality rate may alter the stability behavior of the system. Our results show that introducing a symbiotic species is a plausible way to control the disease in the population. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Lignocellulose-degrading enzymes from termites and their symbiotic microbiota.

    PubMed

    Ni, Jinfeng; Tokuda, Gaku

    2013-11-01

    Lignocellulose-the dry matter of plants, or "plant biomass"-digestion is of increasing interest in organismal metabolism research, specifically the conversion of biomass into biofuels. Termites efficiently decompose lignocelluloses, and studies on lignocellulolytic systems may elucidate mechanisms of efficient lignocellulose degradation in termites as well as offer novel enzyme sources, findings which have significant potential industrial applications. Recent progress in metagenomic and metatranscriptomic research has illuminated the diversity of lignocellulolytic enzymes within the termite gut. Here, we review state-of-the-art research on lignocellulose-degrading systems in termites, specifically cellulases, xylanases, and lignin modification enzymes produced by termites and their symbiotic microbiota. We also discuss recent investigations into heterologous overexpression of lignocellulolytic enzymes from termites and their symbionts.

  18. Host legume-exuded antimetabolites optimize the symbiotic rhizosphere.

    PubMed

    Cai, Tao; Cai, Wentong; Zhang, Jiang; Zheng, Huiming; Tsou, Amy M; Xiao, Lin; Zhong, Zengtao; Zhu, Jun

    2009-08-01

    Rhizobia form symbiotic nodules on host legumes and fix nitrogen for their hosts in exchange for nutrients. In order to establish this mutually beneficial relationship, rhizobia must compete with other soil bacteria in the host legume rhizosphere to colonize plant roots efficiently. A promoter-trap transposon screen in Mesorhizobium tianshanense, a Rhizobium that forms nodules on licorice (Glycyrrhiza uralensis) plants revealed that the expression of msiA, which encodes a putative exporter protein belonging to the LysE family of translocators, is activated by both legume exudates and MsiR, a LysR family transcriptional regulator. Chemical analysis suggests that the msiA-inducing signal in exudates is canavanine, an anti-metabolite present in the seeds and exudates of a variety of legume plants. We show that MsiA serves as a canavanine exporter that is indispensable for canavanine resistance in M. tianshanense. We also show that the expression of MsiA homologues in other rhizobial species is induced by canavanine and is critical for canavanine resistance. Furthermore, rhizobial canavanine resistance is important for root hair adherence as well as for survival in a canavanine-producing legume rhizosphere. Together, these data suggest that host legumes may exude specific antimetabolites into their surroundings to optimize the bacterial population in order to have successful symbiotic events with rhizobia.

  19. UV-protectant metabolites from lichens and their symbiotic partners.

    PubMed

    Nguyen, Khanh-Hung; Chollet-Krugler, Marylène; Gouault, Nicolas; Tomasi, Sophie

    2013-12-01

    Lichens are structurally complex symbiotic organisms that are exposed to a wide variety of external conditions (extreme temperatures, desiccation, UV radiation, etc.). These poikilohydric organisms have developed various mechanisms of photoprotection, such as light scattering, radiation screening, thermal dissipation, activation of antioxidant defense and macromolecules and membrane repair. These unique organisms produce a vast array of compounds, with more than 1000 secondary metabolites known. An important protective mechanism of lichens is the production of UV screening compounds, such as phenolic compounds (depsidones, depsides, diphenyl ethers), anthraquinones, xanthones or shikimic acid derivatives (calycin, mycosporines, scytonemin). Due to the harmful effects of the UVA wavelengths of sunlight, the search for new sunscreens remains important. We herein propose a review that focuses on the UV protectants from lichens and their symbiotic partners (lichenized fungi, green alga, cyanobacteria). In fact, lichens produce unique and/or efficient UV filters such as depsidones (lobaric acid, pannarin, etc.), depsides (atranorin, gyrophoric acid, etc.), diphenyl ethers (epiphorellic acids, buellin), bisxanthones (secalonic acids, etc.), mycosporines and MAAs, scytonemin along with classical pigments (melanin, carotenoids). We propose to classify these compounds with regard to their chemical structures and review the physicochemical properties that act as UV filters. While the most abundant lichen polyfunctionalized aromatic compounds, belonging to orsellinic derivatives, are UVB screens, these organisms produce strong UVA filters, e.g., calycin (pulvinic acid derivatives), bisxanthones (secalonic acids), scytonemin or mycosporines and MAAs with the latter ones exhibiting attractive properties as photoprotectants.

  20. Symbiotic options for the conquest of land.

    PubMed

    Field, Katie J; Pressel, Silvia; Duckett, Jeffrey G; Rimington, William R; Bidartondo, Martin I

    2015-08-01

    The domination of the landmasses of Earth by plants starting during the Ordovician Period drastically altered the development of the biosphere and the composition of the atmosphere, with far-reaching consequences for all life ever since. It is widely thought that symbiotic soil fungi facilitated the colonization of the terrestrial environment by plants. However, recent discoveries in molecular ecology, physiology, cytology, and paleontology have brought into question the hitherto-assumed identity and biology of the fungi engaged in symbiosis with the earliest-diverging lineages of extant land plants. Here, we reconsider the existing paradigm and show that the symbiotic options available to the first plants emerging onto the land were more varied than previously thought.

  1. Molecular Determinants of a Symbiotic Chronic Infection

    PubMed Central

    Gibson, Katherine E.; Kobayashi, Hajime

    2009-01-01

    Rhizobial bacteria colonize legume roots for the purpose of biological nitrogen fixation. A complex series of events, coordinated by host and bacterial signal molecules, underlie the development of this symbiotic interaction. Rhizobia elicit de novo formation of a novel root organ within which they establish a chronic intracellular infection. Legumes permit rhizobia to invade these root tissues while exerting control over the infection process. Once rhizobia gain intracellular access to their host, legumes also strongly influence the process of bacterial differentiation that is required for nitrogen fixation. Even so, symbiotic rhizobia play an active role in promoting their goal of host invasion and chronic persistence by producing a variety of signal molecules that elicit changes in host gene expression. In particular, rhizobia appear to advocate for their access to the host by producing a variety of signal molecules capable of suppressing a general pathogen defense response. PMID:18983260

  2. Heritability of N2 fixation traits, and phenotypic and genotypic correlations between N2 fixation traits with drought resistance traits and yield in peanut under different water regimes

    USDA-ARS?s Scientific Manuscript database

    Drought stress reduces growth and yield in peanut and also reduces nitrogen fixation (NF). Peanut production in drought prone areas should be enhanced by the development of cultivars that can fix more N under drought conditions. The aims of this study were to estimate heritability for NF and to est...

  3. Isolation of symbiotic dinoflagellates by centrifugal elutriation

    SciTech Connect

    Bird, A.E.; Quinn, R.J.

    1986-01-01

    Centrifugal elutriation, a method combining centripetal liquid flow with centrifugal force, has been used to isolate symbiotic dinoflagellates from a cnidarian host. The elutriated cells were shown to be viable by photosynthetic incorporation of /sup 14/CO/sub 2/ and low release of photosynthetic products into the incubation medium. The level of contamination by clinging debris was low and by host solids was negligible.

  4. A Legume Genetic Framework Controls Infection of Nodules by Symbiotic and Endophytic Bacteria

    PubMed Central

    Zgadzaj, Rafal; James, Euan K.; Kelly, Simon; Kawaharada, Yasuyuki; de Jonge, Nadieh; Jensen, Dorthe B.; Madsen, Lene H.; Radutoiu, Simona

    2015-01-01

    Legumes have an intrinsic capacity to accommodate both symbiotic and endophytic bacteria within root nodules. For the symbionts, a complex genetic mechanism that allows mutual recognition and plant infection has emerged from genetic studies under axenic conditions. In contrast, little is known about the mechanisms controlling the endophytic infection. Here we investigate the contribution of both the host and the symbiotic microbe to endophyte infection and development of mixed colonised nodules in Lotus japonicus. We found that infection threads initiated by Mesorhizobium loti, the natural symbiont of Lotus, can selectively guide endophytic bacteria towards nodule primordia, where competent strains multiply and colonise the nodule together with the nitrogen-fixing symbiotic partner. Further co-inoculation studies with the competent coloniser, Rhizobium mesosinicum strain KAW12, show that endophytic nodule infection depends on functional and efficient M. loti-driven Nod factor signalling. KAW12 exopolysaccharide (EPS) enabled endophyte nodule infection whilst compatible M. loti EPS restricted it. Analysis of plant mutants that control different stages of the symbiotic infection showed that both symbiont and endophyte accommodation within nodules is under host genetic control. This demonstrates that when legume plants are exposed to complex communities they selectively regulate access and accommodation of bacteria occupying this specialized environmental niche, the root nodule. PMID:26042417

  5. A legume genetic framework controls infection of nodules by symbiotic and endophytic bacteria.

    PubMed

    Zgadzaj, Rafal; James, Euan K; Kelly, Simon; Kawaharada, Yasuyuki; de Jonge, Nadieh; Jensen, Dorthe B; Madsen, Lene H; Radutoiu, Simona

    2015-06-01

    Legumes have an intrinsic capacity to accommodate both symbiotic and endophytic bacteria within root nodules. For the symbionts, a complex genetic mechanism that allows mutual recognition and plant infection has emerged from genetic studies under axenic conditions. In contrast, little is known about the mechanisms controlling the endophytic infection. Here we investigate the contribution of both the host and the symbiotic microbe to endophyte infection and development of mixed colonised nodules in Lotus japonicus. We found that infection threads initiated by Mesorhizobium loti, the natural symbiont of Lotus, can selectively guide endophytic bacteria towards nodule primordia, where competent strains multiply and colonise the nodule together with the nitrogen-fixing symbiotic partner. Further co-inoculation studies with the competent coloniser, Rhizobium mesosinicum strain KAW12, show that endophytic nodule infection depends on functional and efficient M. loti-driven Nod factor signalling. KAW12 exopolysaccharide (EPS) enabled endophyte nodule infection whilst compatible M. loti EPS restricted it. Analysis of plant mutants that control different stages of the symbiotic infection showed that both symbiont and endophyte accommodation within nodules is under host genetic control. This demonstrates that when legume plants are exposed to complex communities they selectively regulate access and accommodation of bacteria occupying this specialized environmental niche, the root nodule.

  6. Microbiome change by symbiotic invasion in lichens.

    PubMed

    Wedin, Mats; Maier, Stefanie; Fernandez-Brime, Samantha; Cronholm, Bodil; Westberg, Martin; Grube, Martin

    2016-05-01

    Lichens are obligate symbioses between fungi and green algae or cyanobacteria. Most lichens resynthesize their symbiotic thalli from propagules, but some develop within the structures of already existing lichen symbioses. Diploschistes muscorum starts as a parasite infecting the lichen Cladonia symphycarpa and gradually develops an independent Diploschistes lichen thallus. Here we studied how this process influences lichen-associated microbiomes and photobionts by sampling four transitional stages, at sites in Sweden and Germany, and characterizing their microbial communities using high-throughput 16S rRNA gene and photobiont-specific ITS rDNA sequencing, and fluorescence in situ hybridization. A gradual microbiome shift occurred during the transition, but fractions of Cladonia-associated bacteria were retained during the process of symbiotic reorganization. Consistent changes observed across sites included a notable decrease in the relative abundance of Alphaproteobacteria with a concomitant increase in Betaproteobacteria. Armatimonadia, Spartobacteria and Acidobacteria also decreased during the infection of Cladonia by Diploschistes. The lichens differed in photobiont specificity. Cladonia symphycarpa was associated with the same algal species at all sites, but Diploschistes muscorum had a flexible strategy with different photobiont combinations at each site. This symbiotic invasion system suggests that partners can be reorganized and selected for maintaining potential roles rather than depending on particular species. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  7. [Mechanisms of the Effects of Probiotics on Symbiotic Digestion].

    PubMed

    Usakova, N A; Nekrasov, R V; Pravdin, I V; Sverchkova, N V; Kolomiyets, E I; Pavlov, D S

    2015-01-01

    The published data and our own data on the mechanisms of the influence of microbial probiotics, prebiotics, and their combinations on the processes of symbiotic digestion have been considered and generalized. It is shown that the effects on an organism are associated with the enhanced metabolic activity of intestinal bacteria: stimulation of bacterial fermentation of carbohydrates and formation of short-chained fatty acids, an increase in the blotting capacity of the intestines due to elongation of villi and deepening of crypts, and a decrease in secretion of toxic proteolytic products (ammonia, phenols, thiols, indoles, etc.). It has been shown that a combination of probiotics and prebiotic enhances the biological efficiency of a complex preparation, which contributes to activation of carbohydrate, protein, and mineral metabolism.

  8. Effects of symbiotic bacteria on chemical sensitivity of Daphnia magna.

    PubMed

    Manakul, Patcharaporn; Peerakietkhajorn, Saranya; Matsuura, Tomoaki; Kato, Yasuhiko; Watanabe, Hajime

    2017-07-01

    The crustacean zooplankton Daphnia magna has been widely used for chemical toxicity tests. Although abiotic factors have been well documented in ecotoxicological test protocols, biotic factors that may affect the sensitivity to chemical compounds remain limited. Recently, we identified symbiotic bacteria that are critical for the growth and reproduction of D. magna. The presence of symbiotic bacteria on Daphnia raised the question as to whether these bacteria have a positive or negative effect on toxicity tests. In order to evaluate the effects of symbiotic bacteria on toxicity tests, bacteria-free Daphnia were prepared, and their chemical sensitivities were compared with that of Daphnia with symbiotic bacteria based on an acute immobilization test. The Daphnia with symbiotic bacteria showed higher chemical resistance to nonylphenol, fenoxycarb, and pentachlorophenol than bacteria-free Daphnia. These results suggested potential roles of symbiotic bacteria in the chemical resistance of its host Daphnia. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Physical Structure of Four Symbiotic Binaries

    NASA Technical Reports Server (NTRS)

    Kenyon, Scott J. (Principal Investigator)

    1997-01-01

    Disk accretion powers many astronomical objects, including pre-main sequence stars, interacting binary systems, and active galactic nuclei. Unfortunately, models developed to explain the behavior of disks and their surroundings - boundary layers, jets, and winds - lack much predictive power, because the physical mechanism driving disk evolution - the viscosity - is not understood. Observations of many types of accreting systems are needed to constrain the basic physics of disks and provide input for improved models. Symbiotic stars are an attractive laboratory for studying physical phenomena associated with disk accretion. These long period binaries (P(sub orb) approx. 2-3 yr) contain an evolved red giant star, a hot companion, and an ionized nebula. The secondary star usually is a white dwarf accreting material from the wind of its red giant companion. A good example of this type of symbiotic is BF Cygni: our analysis shows that disk accretion powers the nuclear burning shell of the hot white dwarf and also manages to eject material perpendicular to the orbital plane (Mikolajewska, Kenyon, and Mikolajewski 1989). The hot components in other symbiotic binaries appear powered by tidal overflow from a very evolved red giant companion. We recently completed a study of CI Cygni and demonstrated that the accreting secondary is a solar-type main sequence star, rather than a white dwarf (Kenyon et aL 1991). This project continued our study of symbiotic binary systems. Our general plan was to combine archival ultraviolet and optical spectrophotometry with high quality optical radial velocity observations to determine the variation of line and continuum sources as functions of orbital phase. We were very successful in generating orbital solutions and phasing UV+optical spectra for five systems: AG Dra, V443 Her, RW Hya, AG Peg, and AX Per. Summaries of our main results for these systems appear below. A second goal of our project was to consider general models for the

  10. Development and Partial Characterization of Nearly Isogenic Pea Lines (Pisum sativum L.) that Alter Uptake Hydrogenase Activity in Symbiotic Rhizobium.

    PubMed

    Phillips, D A; Kapulnik, Y; Bedmar, E J; Joseph, C M

    1990-04-01

    Some Rhizobium bacteria have H(2)-uptake (Hup) systems that oxidize H(2) evolved from nitrogenase in leguminous root nodules. Pea (Pisum sativum L.) cultivars ;JI1205' and ;Alaska' produce high Hup (Hup(++)) and moderate Hup (Hup(+)) phenotypes, respectively, in Rhizobium leguminosarum 128C53. The physiological significance and biochemical basis of this host plant genetic effect are unknown. The purpose of this investigation was to advance basic Hup studies by developing nearly isogenic lines of peas that alter Hup phenotypes in R. leguminosarum strains containing hup genes. Eight pairs of nearly isogenic pea lines that produce Hup(++) and Hup(+) phenotypes in R. leguminosarum 128C53 were identified in 173 F(2)-derived F(6) families produced from crosses between JI1205 and Alaska. Tests with the pea isolines and three strains of hup-containing R. leguminosarum showed that the isolines altered Hup activity significantly (P symbiotic combinations. Analyses of Hup phenotypes in F(6) families, the F(1) population, and two backcrosses suggested involvement of a single genetic locus. Three of the eight pairs of isolines were identified as being suitable for physiological studies, because the two lines in each pair showed similar growth, N assimilation, and flowering traits under nonsymbiotic conditions. Tests of those lines under N(2)-dependent conditions with isogenic Hup(+) and negligible Hup (Hup(-)) mutants of R. leguminosarum 128C53 showed that, in symbioses with Hup(+) rhizobia, two out of three Hup(++) pea lines decreased N(2) fixation relative to Hup(+) peas. In one of those cases, however, the Hup(++) plant line also decreased fixation by Hup(-) rhizobia. When results were averaged across all rhizobia tested, Hup(+) pea isolines had 8.2% higher dry weight (P

  11. Exploring the symbiotic pangenome of the nitrogen-fixing bacterium Sinorhizobium meliloti

    SciTech Connect

    Galardini, Marco; Mengoni, Alessio; Brilli, Matteo; Pini, Francesco; Fioravanti, Antonella; Lucas, Susan; Lapidus, Alla L.; Cheng, Jan-Fang; Goodwin, Lynne A.; Pitluck, Sam; Land, Miriam L; Hauser, Loren John; Woyke, Tanja; Mikhailova, Natalia; Ivanova, N; Daligault, Hajnalka E.; Bruce, David; Detter, J. Chris; Tapia, Roxanne; Han, Cliff; Teshima, Hazuki; Mocali, Stefano; Bazzicalupo, Marco; Biondi, Emanuele

    2011-01-01

    Background: Sinorhizobium meliloti is a model system for the studies of symbiotic nitrogen fixation. An extensive polymorphism at the genetic and phenotypic level is present in natural populations of this species, especially in relation with symbiotic promotion of plant growth. AK83 and BL225C are two nodule-isolated strains with diverse symbiotic phenotypes; BL225C is more efficient in promoting growth of the Medicago sativa plants than strain AK83. In order to investigate the genetic determinants of the phenotypic diversification of S. meliloti strains AK83 and BL225C, we sequenced the complete genomes for these two strains. Results: With sizes of 7.14 Mbp and 6.97 Mbp, respectively, the genomes of AK83 and BL225C are larger than the laboratory strain Rm1021. The core genome of Rm1021, AK83, BL225C strains included 5124 orthologous groups, while the accessory genome was composed by 2700 orthologous groups. While Rm1021 and BL225C have only three replicons (Chromosome, pSymA and pSymB), AK83 has also two plasmids, 260 and 70 Kbp long. We found 65 interesting orthologous groups of genes that were present only in the accessory genome, consequently responsible for phenotypic diversity and putatively involved in plant-bacterium interaction. Notably, the symbiosis inefficient AK83 lacked several genes required for microaerophilic growth inside nodules, while several genes for accessory functions related to competition, plant invasion and bacteroid tropism were identified only in AK83 and BL225C strains. Presence and extent of polymorphism in regulons of transcription factors involved in symbiotic interaction were also analyzed. Our results indicate that regulons are flexible, with a large number of accessory genes, suggesting that regulons polymorphism could also be a key determinant in the variability of symbiotic performances among the analyzed strains.

  12. Phenotypic, Molecular and Symbiotic Characterization of the Rhizobial Symbionts of Desmanthus paspalaceus (Lindm.) Burkart That Grow in the Province of Santa Fe, Argentina

    PubMed Central

    Fornasero, Laura Viviana; Del Papa, María Florencia; López, José Luis; Albicoro, Francisco Javier; Zabala, Juan Marcelo; Toniutti, María Antonieta; Pensiero, José Francisco; Lagares, Antonio

    2014-01-01

    ; while exhibiting prominent N2 fixation; thus indicating suitability as candidates for inoculation of D. paspalaceus. PMID:25153989

  13. Phenotypic, molecular and symbiotic characterization of the rhizobial symbionts of Desmanthus paspalaceus (Lindm.) Burkart that grow in the province of Santa Fe, Argentina.

    PubMed

    Fornasero, Laura Viviana; Del Papa, María Florencia; López, José Luis; Albicoro, Francisco Javier; Zabala, Juan Marcelo; Toniutti, María Antonieta; Pensiero, José Francisco; Lagares, Antonio

    2014-01-01

    exhibiting prominent N2 fixation; thus indicating suitability as candidates for inoculation of D. paspalaceus.

  14. The mosaic structure of the symbiotic plasmid of Rhizobium etli CFN42 and its relation to other symbiotic genome compartments

    PubMed Central

    González, Víctor; Bustos, Patricia; Ramírez-Romero, Miguel A; Medrano-Soto, Arturo; Salgado, Heladia; Hernández-González, Ismael; Hernández-Celis, Juan Carlos; Quintero, Verónica; Moreno-Hagelsieb, Gabriel; Girard, Lourdes; Rodríguez, Oscar; Flores, Margarita; Cevallos, Miguel A; Collado-Vides, Julio; Romero, David; Dávila, Guillermo

    2003-01-01

    Background Symbiotic bacteria known as rhizobia interact with the roots of legumes and induce the formation of nitrogen-fixing nodules. In rhizobia, essential genes for symbiosis are compartmentalized either in symbiotic plasmids or in chromosomal symbiotic islands. To understand the structure and evolution of the symbiotic genome compartments (SGCs), it is necessary to analyze their common genetic content and organization as well as to study their differences. To date, five SGCs belonging to distinct species of rhizobia have been entirely sequenced. We report the complete sequence of the symbiotic plasmid of Rhizobium etli CFN42, a microsymbiont of beans, and a comparison with other SGC sequences available. Results The symbiotic plasmid is a circular molecule of 371,255 base-pairs containing 359 coding sequences. Nodulation and nitrogen-fixation genes common to other rhizobia are clustered in a region of 125 kilobases. Numerous sequences related to mobile elements are scattered throughout. In some cases the mobile elements flank blocks of functionally related sequences, thereby suggesting a role in transposition. The plasmid contains 12 reiterated DNA families that are likely to participate in genomic rearrangements. Comparisons between this plasmid and complete rhizobial genomes and symbiotic compartments already sequenced show a general lack of synteny and colinearity, with the exception of some transcriptional units. There are only 20 symbiotic genes that are shared by all SGCs. Conclusions Our data support the notion that the symbiotic compartments of rhizobia genomes are mosaic structures that have been frequently tailored by recombination, horizontal transfer and transposition. PMID:12801410

  15. The mosaic structure of the symbiotic plasmid of Rhizobium etli CFN42 and its relation to other symbiotic genome compartments.

    PubMed

    González, Víctor; Bustos, Patricia; Ramírez-Romero, Miguel A; Medrano-Soto, Arturo; Salgado, Heladia; Hernández-González, Ismael; Hernández-Celis, Juan Carlos; Quintero, Verónica; Moreno-Hagelsieb, Gabriel; Girard, Lourdes; Rodríguez, Oscar; Flores, Margarita; Cevallos, Miguel A; Collado-Vides, Julio; Romero, David; Dávila, Guillermo

    2003-01-01

    Symbiotic bacteria known as rhizobia interact with the roots of legumes and induce the formation of nitrogen-fixing nodules. In rhizobia, essential genes for symbiosis are compartmentalized either in symbiotic plasmids or in chromosomal symbiotic islands. To understand the structure and evolution of the symbiotic genome compartments (SGCs), it is necessary to analyze their common genetic content and organization as well as to study their differences. To date, five SGCs belonging to distinct species of rhizobia have been entirely sequenced. We report the complete sequence of the symbiotic plasmid of Rhizobium etli CFN42, a microsymbiont of beans, and a comparison with other SGC sequences available. The symbiotic plasmid is a circular molecule of 371,255 base-pairs containing 359 coding sequences. Nodulation and nitrogen-fixation genes common to other rhizobia are clustered in a region of 125 kilobases. Numerous sequences related to mobile elements are scattered throughout. In some cases the mobile elements flank blocks of functionally related sequences, thereby suggesting a role in transposition. The plasmid contains 12 reiterated DNA families that are likely to participate in genomic rearrangements. Comparisons between this plasmid and complete rhizobial genomes and symbiotic compartments already sequenced show a general lack of synteny and colinearity, with the exception of some transcriptional units. There are only 20 symbiotic genes that are shared by all SGCs. Our data support the notion that the symbiotic compartments of rhizobia genomes are mosaic structures that have been frequently tailored by recombination, horizontal transfer and transposition.

  16. SS 383: A NEW S-TYPE YELLOW SYMBIOTIC STAR?

    SciTech Connect

    Baella, N. O.; Pereira, C. B.; Miranda, L. F.

    2013-11-01

    Symbiotic stars are key objects in understanding the formation and evolution of interacting binary systems, and are probably the progenitors of Type Ia supernovae. However, the number of known symbiotic stars is much lower than predicted. We aim to search for new symbiotic stars, with particular emphasis on the S-type yellow symbiotic stars, in order to determine their total population, evolutionary timescales, and physical properties. The Two Micron All Sky Survey (2MASS) (J – H) versus (H – K {sub s}) color-color diagram has been previously used to identify new symbiotic star candidates and show that yellow symbiotics are located in a particular region of that diagram. Candidate symbiotic stars are selected on the basis of their locus in the 2MASS (J – H) versus (H – K {sub s}) diagram and the presence of Hα line emission in the Stephenson and Sanduleak Hα survey. This diagram separates S-type yellow symbiotic stars from the rest of the S-type symbiotic stars, allowing us to select candidate yellow symbiotics. To establish the true nature of the candidates, intermediate-resolution spectroscopy is obtained. We have identified the Hα emission line source SS 383 as an S-type yellow symbiotic candidate by its position in the 2MASS color-color diagram. The optical spectrum of SS 383 shows Balmer, He I, He II, and [O III] emission lines, in combination with TiO absorption bands that confirm its symbiotic nature. The derived electron density (≅10{sup 8-9} cm{sup –3}), He I emission line intensity ratios, and position in the [O III] λ5007/Hβ versus [O III] λ4363/Hγ diagram indicate that SS 383 is an S-type symbiotic star, with a probable spectral type of K7-M0 deduced for its cool component based on TiO indices. The spectral type and the position of SS 383 (corrected for reddening) in the 2MASS color-color diagram strongly suggest that SS 383 is an S-type yellow symbiotic. Our result points out that the 2MASS color-color diagram is a powerful tool in

  17. Epidemic Spread of Symbiotic and Non-Symbiotic Bradyrhizobium Genotypes Across California.

    PubMed

    Hollowell, A C; Regus, J U; Gano, K A; Bantay, R; Centeno, D; Pham, J; Lyu, J Y; Moore, D; Bernardo, A; Lopez, G; Patil, A; Patel, S; Lii, Y; Sachs, J L

    2016-04-01

    The patterns and drivers of bacterial strain dominance remain poorly understood in natural populations. Here, we cultured 1292 Bradyrhizobium isolates from symbiotic root nodules and the soil root interface of the host plant Acmispon strigosus across a >840-km transect in California. To investigate epidemiology and the potential role of accessory loci as epidemic drivers, isolates were genotyped at two chromosomal loci and were assayed for presence or absence of accessory "symbiosis island" loci that encode capacity to form nodules on hosts. We found that Bradyrhizobium populations were very diverse but dominated by few haplotypes-with a single "epidemic" haplotype constituting nearly 30 % of collected isolates and spreading nearly statewide. In many Bradyrhizobium lineages, we inferred presence and absence of the symbiosis island suggesting recurrent evolutionary gain and or loss of symbiotic capacity. We did not find statistical phylogenetic evidence that the symbiosis island acquisition promotes strain dominance and both symbiotic and non-symbiotic strains exhibited population dominance and spatial spread. Our dataset reveals that a strikingly few Bradyrhizobium genotypes can rapidly spread to dominate a landscape and suggests that these epidemics are not driven by the acquisition of accessory loci as occurs in key human pathogens.

  18. BI Crucis - A new symbiotic star

    NASA Technical Reports Server (NTRS)

    Henize, K. G.; Carlson, E. D.

    1980-01-01

    A Mount Stromlo spectrogram of BI Cru taken in 1962 shows emission lines of H I, He I, He II, Fe II, N III, and the forbidden O III, forbidden Ne III, and forbidden S II transitions superposed on a weak bluish continuum. A spectrogram by Allen in 1974 shows emission lines of H I and Fe II and possibly weak He I, forbidden Fe II, and forbidden O I lines superposed on an M-star absorption spectrum. The object is evidently a symbiotic star showing large variations in its spectral character. Significant differences exist in the mean ion velocities and appear to be correlated with ionization potential.

  19. Analysis of the symbiotic star AG Pegasi

    NASA Technical Reports Server (NTRS)

    Keyes, C. D.; Plavec, M. J.

    1981-01-01

    High and low dispersion IUE data are analyzed in conjunction with coincident ground based spectrophotometric scans and supplementary infrared photometry of the symbiotic object AG Pegasi. The IUE observations yield an improved value of E(B-V) = 0.12. The two stellar components are easily recognized in the spectra. The cool component may be an M1.7 III star and the hot component appears to have T (sub eff) of approximately 30000 K. The emission lines observed in the ultraviolet indicate two or three distince emitting regions. Nebular component ultraviolet intercombination lines suggest an electron density of several times 10 billion/cu cm.

  20. BI Crucis - A new symbiotic star

    NASA Technical Reports Server (NTRS)

    Henize, K. G.; Carlson, E. D.

    1980-01-01

    A Mount Stromlo spectrogram of BI Cru taken in 1962 shows emission lines of H I, He I, He II, Fe II, N III, and the forbidden O III, forbidden Ne III, and forbidden S II transitions superposed on a weak bluish continuum. A spectrogram by Allen in 1974 shows emission lines of H I and Fe II and possibly weak He I, forbidden Fe II, and forbidden O I lines superposed on an M-star absorption spectrum. The object is evidently a symbiotic star showing large variations in its spectral character. Significant differences exist in the mean ion velocities and appear to be correlated with ionization potential.

  1. Symbiotic regulation of plant growth, development and reproduction

    Treesearch

    Russell J. Rodriguez; D. Carl Freeman; E. Durant McArthur; Yong Ok Kim; Regina S. Redman

    2009-01-01

    The growth and development of rice (Oryzae sativa) seedlings was shown to be regulated epigenetically by a fungal endophyte. In contrast to un-inoculated (nonsymbiotic) plants, endophyte colonized (symbiotic) plants preferentially allocated resources into root growth until root hairs were well established. During that time symbiotic roots expanded at...

  2. Comparative proteomics of symbiotic and aposymbiotic juvenile soft corals.

    PubMed

    Barneah, O; Benayahu, Y; Weis, V M

    2006-01-01

    The symbiotic association between corals and photosynthetic unicellular algae is of great importance in coral reef ecosystems. The study of symbiotic relationships is multidisciplinary and involves research in phylogeny, physiology, biochemistry, and ecology. An intriguing phase in each symbiotic relationship is its initiation, in which the partners interact for the first time. The examination of this phase in coral-algae symbiosis from a molecular point of view is still at an early stage. In the present study we used 2-dimensional polyacrylamide gel electrophoresis to compare patterns of proteins synthesized in symbiotic and aposymbiotic primary polyps of the Red Sea soft coral Heteroxenia fuscescens. This is the first work to search for symbiosis-specific proteins during the natural onset of symbiosis in early host ontogeny. The protein profiles reveal changes in the host soft coral proteome through development, but surprisingly virtually no changes in the host proteome as a function of symbiotic state.

  3. Monogamy in a Hyper-Symbiotic Shrimp.

    PubMed

    Baeza, J Antonio; Simpson, Lunden; Ambrosio, Louis J; Guéron, Rodrigo; Mora, Nathalia

    2016-01-01

    Theory predicts that monogamy is adaptive in resource-specialist symbiotic crustaceans inhabiting relatively small and morphologically simple hosts in tropical environments where predation risk away from hosts is high. We tested this prediction in Pontonia manningi, a hyper-symbiotic shrimp that dwells in the mantle cavity of the Atlantic winged oyster Pteria colymbus that, in turn, infects gorgonians from the genus Pseudopterogorgia in the Caribbean Sea. In agreement with theory, P. manningi were found dwelling as heterosexual pairs in oysters more frequently than expected by chance alone. Males and females also inhabited the same host individual independent of the female gravid condition or of the developmental stage of brooded embryos. While the observations above argue in favor of monogamy in P. manningi, there is evidence to suggest that males of the studied species are moderately promiscuous. That females found living solitary in oysters most often brooded embryos, and that males allocated more to weaponry (major claw size) than females at any given size suggest that males might be roaming among host individuals in search of and, fighting for, receptive females. All available information depicts a rather complex mating system in P. manningi: primarily monogamous but with moderately promiscuous males.

  4. Symbiotic two-component gap solitons.

    PubMed

    Roeksabutr, Athikom; Mayteevarunyoo, Thawatchai; Malomed, Boris A

    2012-10-22

    We consider a two-component one-dimensional model of gap solitons (GSs), which is based on two nonlinear Schrödinger equations, coupled by repulsive XPM (cross-phase-modulation) terms, in the absence of the SPM (self-phase-modulation) nonlinearity. The equations include a periodic potential acting on both components, thus giving rise to GSs of the "symbiotic" type, which exist solely due to the repulsive interaction between the two components. The model may be implemented for "holographic solitons" in optics, and in binary bosonic or fermionic gases trapped in the optical lattice. Fundamental symbiotic GSs are constructed, and their stability is investigated, in the first two finite bandgaps of the underlying spectrum. Symmetric solitons are destabilized, including their entire family in the second bandgap, by symmetry-breaking perturbations above a critical value of the total power. Asymmetric solitons of intra-gap and inter-gap types are studied too, with the propagation constants of the two components falling into the same or different bandgaps, respectively. The increase of the asymmetry between the components leads to shrinkage of the stability areas of the GSs. Inter-gap GSs are stable only in a strongly asymmetric form, in which the first-bandgap component is a dominating one. Intra-gap solitons are unstable in the second bandgap. Unstable two-component GSs are transformed into persistent breathers. In addition to systematic numerical considerations, analytical results are obtained by means of an extended ("tailed") Thomas-Fermi approximation (TFA).

  5. Monogamy in a Hyper-Symbiotic Shrimp

    PubMed Central

    Baeza, J. Antonio; Simpson, Lunden; Ambrosio, Louis J.; Guéron, Rodrigo; Mora, Nathalia

    2016-01-01

    Theory predicts that monogamy is adaptive in resource-specialist symbiotic crustaceans inhabiting relatively small and morphologically simple hosts in tropical environments where predation risk away from hosts is high. We tested this prediction in Pontonia manningi, a hyper-symbiotic shrimp that dwells in the mantle cavity of the Atlantic winged oyster Pteria colymbus that, in turn, infects gorgonians from the genus Pseudopterogorgia in the Caribbean Sea. In agreement with theory, P. manningi were found dwelling as heterosexual pairs in oysters more frequently than expected by chance alone. Males and females also inhabited the same host individual independent of the female gravid condition or of the developmental stage of brooded embryos. While the observations above argue in favor of monogamy in P. manningi, there is evidence to suggest that males of the studied species are moderately promiscuous. That females found living solitary in oysters most often brooded embryos, and that males allocated more to weaponry (major claw size) than females at any given size suggest that males might be roaming among host individuals in search of and, fighting for, receptive females. All available information depicts a rather complex mating system in P. manningi: primarily monogamous but with moderately promiscuous males. PMID:26934109

  6. Discrimination against 15N among recombinant inbred lines of Phaseolus vulgaris L. contrasting in phosphorus use efficiency for nitrogen fixation.

    PubMed

    Lazali, Mohamed; Bargaz, Adnane; Carlsson, Georg; Ounane, Sidi Mohamed; Drevon, Jean Jacques

    2014-02-15

    Although isotopic discrimination processes during nitrogen (N) transformations influence the outcome of (15)N based quantification of N2 fixation in legumes, little attention has been given to the effects of genotypic variability and environmental constraints such as phosphorus (P) deficiency, on discrimination against (15)N during N2 fixation. In this study, six Phaseolus vulgaris recombinant inbred lines (RILs), i.e. RILs 115, 104, 34 (P deficiency tolerant) and 147, 83, 70 (P deficiency sensitive), were inoculated with Rhizobium tropici CIAT899, and hydroaeroponically grown with P-sufficient (250 μmol P plant(-1) week(-1)) versus P-deficient (75 μmol P plant(-1) week(-1)) supply. Two harvests were done at 15 (before nodule functioning) and 42 (flowering stage) days after transplanting. Nodulation, plant biomass, P and N contents, and the ratios of (15)N over total N content ((15)N/Nt) for shoots, roots and nodules were determined. The results showed lower (15)N/Nt in shoots than in roots, both being much lower than in nodules. P deficiency caused a larger decrease in (15)N/Nt in shoots (-0.18%) than in nodules (-0.11%) for all of the genotypes, and the decrease in shoots was greatest for RILs 34 (-0.33%) and 104 (-0.25%). Nodule (15)N/Nt was significantly related to both the quantity of N2 fixed (R(2)=0.96***) and the P content of nodules (R(2)=0.66*). We conclude that the discrimination against (15)N in the legume N2-fixing symbiosis of common bean with R. tropici CIAT899 is affected by P nutrition and plant genotype, and that the (15)N/Nt in nodules may be used to screen for genotypic variation in P use efficiency for N2 fixation.

  7. Phylogeny of Symbiotic Genes and the Symbiotic Properties of Rhizobia Specific to Astragalus glycyphyllos L.

    PubMed

    Gnat, Sebastian; Małek, Wanda; Oleńska, Ewa; Wdowiak-Wróbel, Sylwia; Kalita, Michał; Łotocka, Barbara; Wójcik, Magdalena

    2015-01-01

    The phylogeny of symbiotic genes of Astragalus glycyphyllos L. (liquorice milkvetch) nodule isolates was studied by comparative sequence analysis of nodA, nodC, nodH and nifH loci. In all these genes phylograms, liquorice milkvetch rhizobia (closely related to bacteria of three species, i.e. Mesorhizobium amorphae, Mesorhizobium septentrionale and Mesorhizobium ciceri) formed one clearly separate cluster suggesting the horizontal transfer of symbiotic genes from a single ancestor to the bacteria being studied. The high sequence similarity of the symbiotic genes of A. glycyphyllos rhizobia (99-100% in the case of nodAC and nifH genes, and 98-99% in the case of nodH one) points to the relatively recent (in evolutionary scale) lateral transfer of these genes. In the nodACH and nifH phylograms, A. glycyphyllos nodule isolates were grouped together with the genus Mesorhizobium species in one monophyletic clade, close to M. ciceri, Mesorhizobium opportunistum and Mesorhizobium australicum symbiovar biserrulae bacteria, which correlates with the close relationship of these rhizobia host plants. Plant tests revealed the narrow host range of A. glycyphyllos rhizobia. They formed effective symbiotic interactions with their native host (A. glycyphyllos) and Amorpha fruticosa but not with 11 other fabacean species. The nodules induced on A. glycyphyllos roots were indeterminate with apical, persistent meristem, an age gradient of nodule tissues and cortical vascular bundles. To reflect the symbiosis-adaptive phenotype of rhizobia, specific for A. glycyphyllos, we propose for these bacteria the new symbiovar "glycyphyllae", based on nodA and nodC genes sequences.

  8. Phylogeny of Symbiotic Genes and the Symbiotic Properties of Rhizobia Specific to Astragalus glycyphyllos L.

    PubMed Central

    Gnat, Sebastian; Małek, Wanda; Oleńska, Ewa; Wdowiak-Wróbel, Sylwia; Kalita, Michał; Łotocka, Barbara; Wójcik, Magdalena

    2015-01-01

    The phylogeny of symbiotic genes of Astragalus glycyphyllos L. (liquorice milkvetch) nodule isolates was studied by comparative sequence analysis of nodA, nodC, nodH and nifH loci. In all these genes phylograms, liquorice milkvetch rhizobia (closely related to bacteria of three species, i.e. Mesorhizobium amorphae, Mesorhizobium septentrionale and Mesorhizobium ciceri) formed one clearly separate cluster suggesting the horizontal transfer of symbiotic genes from a single ancestor to the bacteria being studied. The high sequence similarity of the symbiotic genes of A. glycyphyllos rhizobia (99–100% in the case of nodAC and nifH genes, and 98–99% in the case of nodH one) points to the relatively recent (in evolutionary scale) lateral transfer of these genes. In the nodACH and nifH phylograms, A. glycyphyllos nodule isolates were grouped together with the genus Mesorhizobium species in one monophyletic clade, close to M. ciceri, Mesorhizobium opportunistum and Mesorhizobium australicum symbiovar biserrulae bacteria, which correlates with the close relationship of these rhizobia host plants. Plant tests revealed the narrow host range of A. glycyphyllos rhizobia. They formed effective symbiotic interactions with their native host (A. glycyphyllos) and Amorpha fruticosa but not with 11 other fabacean species. The nodules induced on A. glycyphyllos roots were indeterminate with apical, persistent meristem, an age gradient of nodule tissues and cortical vascular bundles. To reflect the symbiosis-adaptive phenotype of rhizobia, specific for A. glycyphyllos, we propose for these bacteria the new symbiovar “glycyphyllae”, based on nodA and nodC genes sequences. PMID:26496493

  9. Outbursts in Symbiotic Binaries: Z and Continued Observation

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Keyes, Charles

    2005-01-01

    A major question for symbiotic stars concerns the nature and cause of their outbursts. A small subset of symbiotics, the "slow novae" are fairly well established as thermonuclear events that last on the order of decades. The several symbiotic "recurrent novae", which are much shorter and last on the order of months, are also thought to be thermonuclear runaways. Yet the majority of symbiotics are neither slow novae nor recurrent novae. These are the so-called "classical symbiotics," many of which show outbursts whose cause is not well understood. In some cases, jets are produced in association with an outburst, therefore an investigation into the causes of outbursts will yield important insights into the production of collimated outflows. To investigate the cause and nature of classical symbiotic outbursts, we initiated a program of multi- wavelength observations of these events. First of all in FUSE Cycle 2, we obtained six observational epochs of the 2000-2002 classic symbiotic outburst in the first target of our campaign - class prototype, Z Andromedae. That program was part of a coordinated multi-wavelength Target-of-Opportunity (TOO) campaign with FUSE, XMM, Chandra, MERLIN, the VLA, and ground-based spectroscopic and high time-resolution photometric observations. Our campaign proved the concept, utility, and need for coordinated multi-wavelength observations in order to make progress in understanding the nature of the outburst mechanisms in symbiotic stars. Indeed, the FUSE data were the cornerstone of this project. The present program is a continuation of that cycle 2 effort. Indeed, the observations acquired in this program are vital to the proper interpretation of the material acquired in cycle 2 as the new data cover the critical time period when the star continues to decline from outburst and actually returns to quiescence. The utilization of these data have allowed us to refine and complete description of our new model for classical symbiotic system

  10. Symbiote transmission and maintenance of extra-genomic associations.

    PubMed

    Fitzpatrick, Benjamin M

    2014-01-01

    Symbiotes can be transmitted from parents to offspring or horizontally from unrelated hosts or the environment. A key question is whether symbiote transmission is similar enough to Mendelian gene transmission to generate and maintain coevolutionary associations between host and symbiote genes. Recent papers come to opposite conclusions, with some suggesting that any horizontal transmission eliminates genetic association. These studies are hard to compare owing to arbitrary differences in modeling approach, parameter values, and assumptions about selection. I show that associations between host and symbiote genes (extra-genomic associations) can be described by the same dynamic model as conventional linkage disequilibria between genes in the same genome. Thus, covariance between host and symbiote genomes depends on population history, geographic structure, selection, and co-transmission rate, just as covariance between genes within a genome. The conclusion that horizontal transmission rapidly erodes extra-genomic associations is equivalent to the conclusion that recombination rapidly erodes associations between genes within a genome. The conclusion is correct in the absence of population structure or selection. However, population structure can maintain spatial associations between host and symbiote traits, and non-additive selection (interspecific epistasis) can generate covariances between host and symbiote genotypes. These results can also be applied to cultural or other non-genetic traits. This work contributes to a growing consensus that genomic, symbiotic, and gene-culture evolution can be analyzed under a common theoretical framework. In terms of coevolutionary potential, symbiotes can be viewed as lying on a continuum between the intimacy of genes and the indifference of casually co-occurring species.

  11. Uric acid deposits in symbiotic marine algae.

    PubMed

    Clode, Peta L; Saunders, Martin; Maker, Garth; Ludwig, Martha; Atkins, Craig A

    2009-02-01

    The symbiosis between cnidarians and dinoflagellate algae is not understood at the cell or molecular level, yet this relationship is responsible for the formation of thousands of square kilometres of coral reefs. We have investigated the nature of crystalline material prominent within marine algal symbionts of Aiptasia sp. anemones. This material, which has historically been considered to be calcium oxalate, is shown to be uric acid. We demonstrate that these abundant uric acid stores can be mobilized rapidly, thereby allowing the algal symbionts to flourish in an otherwise N-poor environment. This is the first report of uric acid accumulation by symbiotic marine algae. These data provide new insight and considerations for understanding the physiological basis of algal symbioses, and represent a new and previously unconsidered aspect of N metabolism in cnidarian, and a variety of other, marine symbioses.

  12. Symbiotic empirical ethics: a practical methodology.

    PubMed

    Frith, Lucy

    2012-05-01

    Like any discipline, bioethics is a developing field of academic inquiry; and recent trends in scholarship have been towards more engagement with empirical research. This 'empirical turn' has provoked extensive debate over how such 'descriptive' research carried out in the social sciences contributes to the distinctively normative aspect of bioethics. This paper will address this issue by developing a practical research methodology for the inclusion of data from social science studies into ethical deliberation. This methodology will be based on a naturalistic conception of ethical theory that sees practice as informing theory just as theory informs practice - the two are symbiotically related. From this engagement with practice, the ways that such theories need to be extended and developed can be determined. This is a practical methodology for integrating theory and practice that can be used in empirical studies, one that uses ethical theory both to explore the data and to draw normative conclusions. © 2010 Blackwell Publishing Ltd.

  13. Kinematics of the symbiotic system R Aqr

    NASA Astrophysics Data System (ADS)

    Navarro, S.; Corral, L. J.; Steffen, W.

    2014-04-01

    We present the results of the kinematical analysis of the symbiotic system R Aqr. We obtained high dispersion spectra with the MES spectrograph at the 2.1 m telescope of San Pedro Mártir (MEZCAL). The used filter were Ha + [NII], (λc = 6575Å, Δλ = 90Å). We analyse the [NII] λλ6583 line. When the observations are compared with previous ones by Solf (1992) we detected an important change in the projected velocities of the observed knots, supporting the idea of a precessing jet. We are working also in a 3-D kinematic model for the object using the measured velocities and the state of the model is presented.

  14. Symbiotic Stars on Asiago Archive Plates

    NASA Astrophysics Data System (ADS)

    Jurdana-Šepić, Rajka; Munari, Ulisse

    2010-01-01

    The Asiago photographic archive has been searched for plates containing the symbiotic stars AS 210, AS 327, AX Per, BF Cyg, CI Cyg, DT Ser, EG And, GH Gem, Hen 2-442, Hen 3-1591, HM Sge, MaC 1-17, NSV 11776, Pe 2-16, Pt 1, PU Vul, RS Oph, T CrB, UV Aur, V1016 Cyg, V1329 Cyg, V352 Aql, V4018 Sgr, Wray 15-1470, and Z And. A total of 1617 good-quality plates imaging the program stars have been found and their brightness has been estimated using the Henden & Munari UBVRC IC local photometric sequences. The results for the objects with most abundant measurements are discussed.

  15. AG Pegasi - now a classical symbiotic star in outburst?

    NASA Astrophysics Data System (ADS)

    Tomov, T. V.; Stoyanov, K. A.; Zamanov, R. K.

    2016-11-01

    Optical spectroscopy study of the recent AG Pegasi (AG Peg) outburst observed during the second half of 2015 is presented. Considerable variations of the intensity and the shape of the spectral features as well as the changes of the hot component parameters, caused by the outburst, are discussed and certain similarities between the outburst of AG Peg and the outburst of a classical symbiotic stars are shown. It seems that after the end of the symbiotic nova phase, AG Peg became a member of the classical symbiotic stars group.

  16. Computer symbiosis: Emergence of symbiotic behavior through evolution

    SciTech Connect

    Ikegami, Takashi; Kaneko, Kunihiko

    1989-01-01

    Symbiosis is altruistic cooperation between distinct species. It is one of the most effective evolutionary processes, but its dynamics are not well understood as yet. A simple model of symbiosis is introduced, where we consider interactions between hosts and parasites and also mutations of hosts and parasites. It is found that a symbiotic state emerges for a suitable range of mutation rates. The symbiotic state is not static, but dynamically oscillates. Harmful parasites violating symbiosis appear periodically, but are rapidly extinguished by hosts and other parasites, and the symbiotic state is recovered. The emergence of ''Tit for Tat'' strategy to maintain symbiosis is discussed. 4 figs.

  17. Symbiotic Nitrogen Fixation and the Challenges to Its Extension to Nonlegumes

    PubMed Central

    Mus, Florence; Crook, Matthew B.; Garcia, Kevin; Garcia Costas, Amaya; Geddes, Barney A.; Kouri, Evangelia D.; Paramasivan, Ponraj; Ryu, Min-Hyung; Oldroyd, Giles E. D.; Poole, Philip S.; Udvardi, Michael K.; Voigt, Christopher A.

    2016-01-01

    Access to fixed or available forms of nitrogen limits the productivity of crop plants and thus food production. Nitrogenous fertilizer production currently represents a significant expense for the efficient growth of various crops in the developed world. There are significant potential gains to be had from reducing dependence on nitrogenous fertilizers in agriculture in the developed world and in developing countries, and there is significant interest in research on biological nitrogen fixation and prospects for increasing its importance in an agricultural setting. Biological nitrogen fixation is the conversion of atmospheric N2 to NH3, a form that can be used by plants. However, the process is restricted to bacteria and archaea and does not occur in eukaryotes. Symbiotic nitrogen fixation is part of a mutualistic relationship in which plants provide a niche and fixed carbon to bacteria in exchange for fixed nitrogen. This process is restricted mainly to legumes in agricultural systems, and there is considerable interest in exploring whether similar symbioses can be developed in nonlegumes, which produce the bulk of human food. We are at a juncture at which the fundamental understanding of biological nitrogen fixation has matured to a level that we can think about engineering symbiotic relationships using synthetic biology approaches. This minireview highlights the fundamental advances in our understanding of biological nitrogen fixation in the context of a blueprint for expanding symbiotic nitrogen fixation to a greater diversity of crop plants through synthetic biology. PMID:27084023

  18. Symbiotic Nitrogen Fixation and the Challenges to Its Extension to Nonlegumes.

    PubMed

    Mus, Florence; Crook, Matthew B; Garcia, Kevin; Garcia Costas, Amaya; Geddes, Barney A; Kouri, Evangelia D; Paramasivan, Ponraj; Ryu, Min-Hyung; Oldroyd, Giles E D; Poole, Philip S; Udvardi, Michael K; Voigt, Christopher A; Ané, Jean-Michel; Peters, John W

    2016-07-01

    Access to fixed or available forms of nitrogen limits the productivity of crop plants and thus food production. Nitrogenous fertilizer production currently represents a significant expense for the efficient growth of various crops in the developed world. There are significant potential gains to be had from reducing dependence on nitrogenous fertilizers in agriculture in the developed world and in developing countries, and there is significant interest in research on biological nitrogen fixation and prospects for increasing its importance in an agricultural setting. Biological nitrogen fixation is the conversion of atmospheric N2 to NH3, a form that can be used by plants. However, the process is restricted to bacteria and archaea and does not occur in eukaryotes. Symbiotic nitrogen fixation is part of a mutualistic relationship in which plants provide a niche and fixed carbon to bacteria in exchange for fixed nitrogen. This process is restricted mainly to legumes in agricultural systems, and there is considerable interest in exploring whether similar symbioses can be developed in nonlegumes, which produce the bulk of human food. We are at a juncture at which the fundamental understanding of biological nitrogen fixation has matured to a level that we can think about engineering symbiotic relationships using synthetic biology approaches. This minireview highlights the fundamental advances in our understanding of biological nitrogen fixation in the context of a blueprint for expanding symbiotic nitrogen fixation to a greater diversity of crop plants through synthetic biology.

  19. Fossilized glycolipids reveal past oceanic N2 fixation by heterocystous cyanobacteria

    PubMed Central

    Bauersachs, Thorsten; Speelman, Eveline N.; Hopmans, Ellen C.; Reichart, Gert-Jan; Schouten, Stefan; Damsté, Jaap S. Sinninghe

    2010-01-01

    N2-fixing cyanobacteria play an essential role in sustaining primary productivity in contemporary oceans and freshwater systems. However, the significance of N2-fixing cyanobacteria in past nitrogen cycling is difficult to establish as their preservation potential is relatively poor and specific biological markers are presently lacking. Heterocystous N2-fixing cyanobacteria synthesize unique long-chain glycolipids in the cell envelope covering the heterocyst cell to protect the oxygen-sensitive nitrogenase enzyme. We found that these heterocyst glycolipids are remarkably well preserved in (ancient) lacustrine and marine sediments, unambiguously indicating the (past) presence of N2-fixing heterocystous cyanobacteria. Analysis of Pleistocene sediments of the eastern Mediterranean Sea showed that heterocystous cyanobacteria, likely as epiphytes in symbiosis with planktonic diatoms, were particularly abundant during deposition of sapropels. Eocene Arctic Ocean sediments deposited at a time of large Azolla blooms contained glycolipids typical for heterocystous cyanobacteria presently living in symbiosis with the freshwater fern Azolla, indicating that this symbiosis already existed in that time. Our study thus suggests that heterocystous cyanobacteria played a major role in adding “new” fixed nitrogen to surface waters in past stratified oceans. PMID:20966349

  20. Taxonomic identity determines N2 fixation by canopy trees across lowland tropical forests.

    PubMed

    Wurzburger, Nina; Hedin, Lars O

    2016-01-01

    Legumes capable of fixing atmospheric N2 are abundant and diverse in many tropical forests, but the factors determining ecological patterns in fixation are unresolved. A long-standing idea is that fixation depends on soil nutrients (N, P or Mo), but recent evidence shows that fixation may also differ among N2-fixing species. We sampled canopy-height trees across five species and one species group of N2-fixers along a landscape P gradient, and manipulated P and Mo to seedlings in a shadehouse. Our results identify taxonomy as the major determinant of fixation, with P (and possibly Mo) only influencing fixation following tree-fall disturbances. While 44% of trees did not fix N2, other trees fixed at high rates, with two species functioning as superfixers across the landscape. Our results raise the possibility that fixation is determined by biodiversity, evolutionary history and species-specific traits (tree growth rate, canopy stature and response to disturbance) in the tropical biome.

  1. Composition of nifH in a wastewater treatment system reliant on N(2) fixation.

    PubMed

    Bowers, T H; Reid, N M; Lloyd-Jones, G

    2008-07-01

    High levels of nitrogen fixation have been observed in the wastewaters of pulp and paper mills. In this study, we show that nitrogen fixation in a model pulp and paper wastewater treatment system is supported by a high density of nifH sequences that are of low diversity. Quantitative PCR revealed a ratio of nifH to 16S rDNA of 1.14 +/- 0.76 which shows that very high levels of the nifH gene were enriched to support the high rates of nitrogen fixation that occur in this wastewater. Changes in wastewater composition and dissolved oxygen levels did not affect the nifH levels and allowed stable wastewater treatment. The nifH sequences identified display a similar profile to those seen in forest soil environments where nifH sequences derived from alpha-proteobacteria and beta-proteobacteria are also prevalent.

  2. N2 fixation of common and hairy vetches when intercropped into switchgrass

    USDA-ARS?s Scientific Manuscript database

    Interest in alternatives to synthetic nitrogen (N) fertilizer for switchgrass (Panicum virgatum L.) forage and bioenergy production continues to increase, and interseeding legumes into swards may be one such prospect. Common vetch (Vicia sativa L.) occurs naturally throughout the U.S. and has fewer ...

  3. Stress as a Normal Cue in the Symbiotic Environment.

    PubMed

    Schwartzman, Julia A; Ruby, Edward G

    2016-05-01

    All multicellular hosts form associations with groups of microorganisms. These microbial communities can be taxonomically diverse and dynamic, and their persistence is due to robust, and sometimes coevolved, host-microbe and microbe-microbe interactions. Chemical and physical sources of stress are prominently situated in this molecular exchange, as cues for cellular responses in symbiotic microbes. Stress in the symbiotic environment may arise from three sources: host tissues, microbe-induced immune responses, or other microbes in the host environment. The responses of microbes to these stresses can be general or highly specialized, and collectively may contribute to the stability of the symbiotic system. In this review, we highlight recent work that emphasizes the role of stress as a cue in the symbiotic environment of plants and animals. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Stress as a Normal Cue in the Symbiotic Environment

    PubMed Central

    Schwartzman, Julia A.; Ruby, Edward G.

    2016-01-01

    All multicellular hosts form associations with groups of microorganisms. These microbial communities can be taxonomically diverse and dynamic, and their persistence is due to robust, and sometimes co-evolved, host microbe and microbe microbe interactions. Chemical and physical sources of stress are prominently situated in this molecular exchange, as cues for cellular responses in symbiotic microbes. Stress in the symbiotic environment may arise from three sources: host tissues, microbe-induced immune responses, or other microbes in the host environment. The responses of microbes to these stresses can be general or highly specialized, and collectively may contribute to the stability of the symbiotic system. In this review, we highlight recent work that emphasizes the role of stress as a cue in the symbiotic environment of plants and animals. PMID:27004825

  5. Microbiome change by symbiotic invasion in lichens

    NASA Astrophysics Data System (ADS)

    Maier, Stefanie; Wedin, Mats; Fernandez-Brime, Samantha; Cronholm, Bodil; Westberg, Martin; Weber, Bettina; Grube, Martin

    2016-04-01

    Biological soil crusts (BSC) seal the soil surface from erosive forces in many habitats where plants cannot compete. Lichens symbioses of fungi and algae often form significant fraction of these microbial assemblages. In addition to the fungal symbiont, many species of other fungi can inhabit the lichenic structures and interact with their hosts in different ways, ranging from commensalism to parasitism. More than 1800 species of lichenicolous (lichen-inhabiting) fungi are known to science. One example is Diploschistes muscorum, a common species in lichen-dominated BSC that infects lichens of the genus Cladonia. D. muscorum starts as a lichenicolous fungus, invading the lichen Cladonia symphycarpa and gradually develops an independent Diploschistes lichen thallus. Furthermore, bacterial groups, such as Alphaproteobacteria and Acidobacteria, have been consistently recovered from lichen thalli and evidence is rapidly accumulating that these microbes may generally play integral roles in the lichen symbiosis. Here we describe lichen microbiome dynamics as the parasitic lichen D. muscorum takes over C. symphycarpa. We used high-throughput 16S rRNA gene and photobiont-specific ITS rDNA sequencing to track bacterial and algal transitions during the infection process, and employed fluorescence in situ hybridization to localize bacteria in the Cladonia and Diploschistes lichen thalli. We sampled four transitional stages, at sites in Sweden and Germany: A) Cladonia with no visible infection, B) early infection stage defined by the first visible Diploschistes thallus, C) late-stage infection with parts of the Cladonia thallus still identifiable, and D) final stage with a fully developed Diploschistes thallus, A gradual microbiome shift occurred during the transition, but fractions of Cladonia-associated bacteria were retained during the process of symbiotic reorganization. Consistent changes observed across sites included a notable decrease in the relative abundance of

  6. Genetic and Symbiotic Diversity of Nitrogen-Fixing Bacteria Isolated from Agricultural Soils in the Western Amazon by Using Cowpea as the Trap Plant

    PubMed Central

    Azarias Guimarães, Amanda; Duque Jaramillo, Paula Marcela; Simão Abrahão Nóbrega, Rafaela; Florentino, Ligiane Aparecida; Barroso Silva, Karina

    2012-01-01

    Cowpea is a legume of great agronomic importance that establishes symbiotic relationships with nitrogen-fixing bacteria. However, little is known about the genetic and symbiotic diversity of these bacteria in distinct ecosystems. Our study evaluated the genetic diversity and symbiotic efficiencies of 119 bacterial strains isolated from agriculture soils in the western Amazon using cowpea as a trap plant. These strains were clustered into 11 cultural groups according to growth rate and pH. The 57 nonnodulating strains were predominantly fast growing and acidifying, indicating a high incidence of endophytic strains in the nodules. The other 62 strains, authenticated as nodulating bacteria, exhibited various symbiotic efficiencies, with 68% of strains promoting a significant increase in shoot dry matter of cowpea compared with the control with no inoculation and low levels of mineral nitrogen. Fifty genotypes with 70% similarity and 21 genotypes with 30% similarity were obtained through repetitive DNA sequence (BOX element)-based PCR (BOX-PCR) clustering. The 16S rRNA gene sequencing of strains representative of BOX-PCR clusters showed a predominance of bacteria from the genus Bradyrhizobium but with high species diversity. Rhizobium, Burkholderia, and Achromobacter species were also identified. These results support observations of cowpea promiscuity and demonstrate the high symbiotic and genetic diversity of rhizobia species in areas under cultivation in the western Amazon. PMID:22798370

  7. Genetic and symbiotic diversity of nitrogen-fixing bacteria isolated from agricultural soils in the western Amazon by using cowpea as the trap plant.

    PubMed

    Azarias Guimarães, Amanda; Duque Jaramillo, Paula Marcela; Simão Abrahão Nóbrega, Rafaela; Florentino, Ligiane Aparecida; Barroso Silva, Karina; de Souza Moreira, Fatima Maria

    2012-09-01

    Cowpea is a legume of great agronomic importance that establishes symbiotic relationships with nitrogen-fixing bacteria. However, little is known about the genetic and symbiotic diversity of these bacteria in distinct ecosystems. Our study evaluated the genetic diversity and symbiotic efficiencies of 119 bacterial strains isolated from agriculture soils in the western Amazon using cowpea as a trap plant. These strains were clustered into 11 cultural groups according to growth rate and pH. The 57 nonnodulating strains were predominantly fast growing and acidifying, indicating a high incidence of endophytic strains in the nodules. The other 62 strains, authenticated as nodulating bacteria, exhibited various symbiotic efficiencies, with 68% of strains promoting a significant increase in shoot dry matter of cowpea compared with the control with no inoculation and low levels of mineral nitrogen. Fifty genotypes with 70% similarity and 21 genotypes with 30% similarity were obtained through repetitive DNA sequence (BOX element)-based PCR (BOX-PCR) clustering. The 16S rRNA gene sequencing of strains representative of BOX-PCR clusters showed a predominance of bacteria from the genus Bradyrhizobium but with high species diversity. Rhizobium, Burkholderia, and Achromobacter species were also identified. These results support observations of cowpea promiscuity and demonstrate the high symbiotic and genetic diversity of rhizobia species in areas under cultivation in the western Amazon.

  8. Phylogeny of nodulation genes and symbiotic diversity of Acacia senegal (L.) Willd. and A. seyal (Del.) Mesorhizobium strains from different regions of Senegal.

    PubMed

    Bakhoum, Niokhor; Galiana, Antoine; Le Roux, Christine; Kane, Aboubacry; Duponnois, Robin; Ndoye, Fatou; Fall, Dioumacor; Noba, Kandioura; Sylla, Samba Ndao; Diouf, Diégane

    2015-04-01

    Acacia senegal and Acacia seyal are small, deciduous legume trees, most highly valued for nitrogen fixation and for the production of gum arabic, a commodity of international trade since ancient times. Symbiotic nitrogen fixation by legumes represents the main natural input of atmospheric N2 into ecosystems which may ultimately benefit all organisms. We analyzed the nod and nif symbiotic genes and symbiotic properties of root-nodulating bacteria isolated from A. senegal and A. seyal in Senegal. The symbiotic genes of rhizobial strains from the two Acacia species were closed to those of Mesorhizobium plurifarium and grouped separately in the phylogenetic trees. Phylogeny of rhizobial nitrogen fixation gene nifH was similar to those of nodulation genes (nodA and nodC). All A. senegal rhizobial strains showed identical nodA, nodC, and nifH gene sequences. By contrast, A. seyal rhizobial strains exhibited different symbiotic gene sequences. Efficiency tests demonstrated that inoculation of both Acacia species significantly affected nodulation, total dry weight, acetylene reduction activity (ARA), and specific acetylene reduction activity (SARA) of plants. However, these cross-inoculation tests did not show any specificity of Mesorhizobium strains toward a given Acacia host species in terms of infectivity and efficiency as stated by principal component analysis (PCA). This study demonstrates that large-scale inoculation of A. senegal and A. seyal in the framework of reafforestation programs requires a preliminary step of rhizobial strain selection for both Acacia species.

  9. Symbiotic two-species contact process

    NASA Astrophysics Data System (ADS)

    de Oliveira, Marcelo Martins; Dos Santos, Renato Vieira; Dickman, Ronald

    2012-07-01

    We study a contact process (CP) with two species that interact in a symbiotic manner. In our model, each site of a lattice may be vacant or host individuals of species A and/or B; multiple occupancy by the same species is prohibited. Symbiosis is represented by a reduced death rate μ<1 for individuals at sites with both species present. Otherwise, the dynamics is that of the basic CP, with creation (at vacant neighbor sites) at rate λ and death of (isolated) individuals at a rate of unity. Mean-field theory and Monte Carlo simulation show that the critical creation rate λc(μ) is a decreasing function of μ, even though a single-species population must go extinct for λ<λc(1), the critical point of the basic CP. Extensive simulations yield results for critical behavior that are compatible with the directed percolation (DP) universality class, but with unusually strong corrections to scaling. A field-theoretic argument supports the conclusion of DP critical behavior. We obtain similar results for a CP with creation at second-neighbor sites and enhanced survival at first neighbors in the form of an annihilation rate that decreases with the number of occupied first neighbors.

  10. Development and Partial Characterization of Nearly Isogenic Pea Lines (Pisum sativum L.) that Alter Uptake Hydrogenase Activity in Symbiotic Rhizobium1

    PubMed Central

    Phillips, Donald A.; Kapulnik, Yoram; Bedmar, Eulogio J.; Joseph, Cecillia M.

    1990-01-01

    Some Rhizobium bacteria have H2-uptake (Hup) systems that oxidize H2 evolved from nitrogenase in leguminous root nodules. Pea (Pisum sativum L.) cultivars `JI1205' and `Alaska' produce high Hup (Hup++) and moderate Hup (Hup+) phenotypes, respectively, in Rhizobium leguminosarum 128C53. The physiological significance and biochemical basis of this host plant genetic effect are unknown. The purpose of this investigation was to advance basic Hup studies by developing nearly isogenic lines of peas that alter Hup phenotypes in R. leguminosarum strains containing hup genes. Eight pairs of nearly isogenic pea lines that produce Hup++ and Hup+ phenotypes in R. leguminosarum 128C53 were identified in 173 F2-derived F6 families produced from crosses between JI1205 and Alaska. Tests with the pea isolines and three strains of hup-containing R. leguminosarum showed that the isolines altered Hup activity significantly (P ≤ 0.05) in 19 of 24 symbiotic combinations. Analyses of Hup phenotypes in F6 families, the F1 population, and two backcrosses suggested involvement of a single genetic locus. Three of the eight pairs of isolines were identified as being suitable for physiological studies, because the two lines in each pair showed similar growth, N assimilation, and flowering traits under nonsymbiotic conditions. Tests of those lines under N2-dependent conditions with isogenic Hup+ and negligible Hup (Hup−) mutants of R. leguminosarum 128C53 showed that, in symbioses with Hup+ rhizobia, two out of three Hup++ pea lines decreased N2 fixation relative to Hup+ peas. In one of those cases, however, the Hup++ plant line also decreased fixation by Hup− rhizobia. When results were averaged across all rhizobia tested, Hup+ pea isolines had 8.2% higher dry weight (P ≤ 0.05) and fixed 12.6% more N2 (P ≤ 0.05) than Hup++ isolines. Pea lines described here may help identify host plant factors that influence rhizobial Hup activity and should assist in clarifying how Hup systems

  11. Adaptation of the symbiotic Mesorhizobium–chickpea relationship to phosphate deficiency relies on reprogramming of whole-plant metabolism

    PubMed Central

    Nasr Esfahani, Maryam; Kusano, Miyako; Nguyen, Kien Huu; Watanabe, Yasuko; Ha, Chien Van; Saito, Kazuki; Sulieman, Saad; Herrera-Estrella, Luis; Tran, Lam-Son Phan

    2016-01-01

    Low inorganic phosphate (Pi) availability is a major constraint for efficient nitrogen fixation in legumes, including chickpea. To elucidate the mechanisms involved in nodule acclimation to low Pi availability, two Mesorhizobium–chickpea associations exhibiting differential symbiotic performances, Mesorhizobium ciceri CP-31 (McCP-31)–chickpea and Mesorhizobium mediterranum SWRI9 (MmSWRI9)–chickpea, were comprehensively studied under both control and low Pi conditions. MmSWRI9–chickpea showed a lower symbiotic efficiency under low Pi availability than McCP-31–chickpea as evidenced by reduced growth parameters and down-regulation of nifD and nifK. These differences can be attributed to decline in Pi level in MmSWRI9-induced nodules under low Pi stress, which coincided with up-regulation of several key Pi starvation-responsive genes, and accumulation of asparagine in nodules and the levels of identified amino acids in Pi-deficient leaves of MmSWRI9-inoculated plants exceeding the shoot nitrogen requirement during Pi starvation, indicative of nitrogen feedback inhibition. Conversely, Pi levels increased in nodules of Pi-stressed McCP-31–inoculated plants, because these plants evolved various metabolic and biochemical strategies to maintain nodular Pi homeostasis under Pi deficiency. These adaptations involve the activation of alternative pathways of carbon metabolism, enhanced production and exudation of organic acids from roots into the rhizosphere, and the ability to protect nodule metabolism against Pi deficiency-induced oxidative stress. Collectively, the adaptation of symbiotic efficiency under Pi deficiency resulted from highly coordinated processes with an extensive reprogramming of whole-plant metabolism. The findings of this study will enable us to design effective breeding and genetic engineering strategies to enhance symbiotic efficiency in legume crops. PMID:27450089

  12. Outbursts In Symbiotic Binaries (FUSE 2000)

    NASA Technical Reports Server (NTRS)

    Kenyon, Scott J.; Sonneborn, George (Technical Monitor)

    2002-01-01

    During the past year, we made good progress on analysis of FUSE observations of the symbiotic binary Z And. For background, Z And is a binary system composed of a red giant and a hot component of unknown status. The orbital period is roughly 750 days. The hot component undergoes large-scale eruptions every 10-20 yr. An outburst began several years ago, triggering this FUSE opportunity. First, we obtained an excellent set of ground-based optical data in support, of the FUSE observations. We used FAST, a high throughput low resolution spectrograph on the 1.5-m telescope at Mt. Hopkins, Arizona. A 300 g/ mm grating blazed at 4750 A, a 3 in. slit, and a thinned Loral 512 x 2688 CCD gave us spectra covering 3800-7500 A at a resolution of 6 A. The wavelength solution for each spectrum has a probable error of +/- 0.5 A or better. Most of the resulting spectra have moderate signal-to-noise, S/.N approx. greater than 30 per pixel. The time coverage for these spectra is excellent. Typically, we acquired spectra every 1-2 nights during dark runs at Mt. Hopkins. These data cover most of the rise and all of the decline of the recent outburst. The spectra show a wealth of emission lines, including H I, He I, He II, [Fe V11], and the Raman scattering bands at 6830 A and 7088 A. The Raman bands and other high ionization features vary considerably throughout the outburst. These features will enable us to correlate variations in the FUSE spectra with variations in the optical spectra. Second, we began an analysis of FUSE spectra of Z And. We have carefully examined the spectra, identifying real features and defects. We have identified and measured fluxes for all strong emission lines, including the O VI doublet at 1032 A and 1038 A. These and several other strong emission lines display pronounced P Cygni absorption components indicative of outgrowing gas. We will attempt to correlate these velocities with similar profiles observed on optical spectra. The line velocities - together

  13. Symbiotic variable V4018 Sgr in outburst

    NASA Astrophysics Data System (ADS)

    Elizabeth O. Waagen

    2012-09-01

    The symbiotic variable V4018 Sgr is undergoing an outburst, according to observations reported to the AAVSO and confirmed by spectroscopy by Ulisse Munari et al. Prompted by an observation and comment from John Bortle (Stormville, NY) (16 June 2012, visual magnitude 12.2) about a possible outburst, Steven O'Connor (St. George's, Bermuda) obtained an observation (10 August 2012, 11.44V) that confirmed V4018 Sgr was bright. His subsequent BVRI observations in September and visual observations by Bortle and Andrew Pearce (Nedlands, Western Australia) show the system brightening and at V magnitude 11.07 as of 2012 Sep. 17.091 UT. Ulisse Munari (INAF Astr. Obs. Padua, Italy) and colleagues Paolo Valisa and Sergio Dallaporta (ANS Collaboration), after being informed by the AAVSO of the bright state of V4018 Sgr, carried out spectroscopy. Munari writes: "A low resolution, absolutely fluxed 4000-8650 Ang spectrum of V4018 Sgr was obtained on Sept 13.90 UT with the 0.6m telescope ! of the Schiaparelli Observatory in Varese (Italy). It shows the spectrum of the M giant overwhelmed by a blue continuum up to 6000 Ang, and all high ionization emission lines typical of quiescence are gone, leaving only hydrogen Balmer and weak HeI lines in emission. The spectrum looks like a template one for a symbiotic star in outburst. CCD photometry was obtained on Sept 13.79 UT and provides V=11.027 ± 0.002, B-V=+0.621 ± 0.003. The B-V color is appreciably bluer and the V magnitude much brighter than typical in quiescence (on average V=13.3, B-V=+1.09; Henden and Munari 2008, Baltic Astronomy 17, 293), and support the idea V4018 Sgr is undergoing an outburst." According to Munari, the last bright outburst of V4018 Sgr was underway in June 1990. Observations in the AAVSO International Database from Albert Jones (Nelson, New Zealand) beginning in May 1992 show the variable at visual magnitude 11.0, with fluctuations between 10.5 and 11.9 through October 1995. Numerous ! other observers

  14. Comprehensive EST analysis of the symbiotic sea anemone, Anemonia viridis.

    PubMed

    Sabourault, Cécile; Ganot, Philippe; Deleury, Emeline; Allemand, Denis; Furla, Paola

    2009-07-23

    Coral reef ecosystems are renowned for their diversity and beauty. Their immense ecological success is due to a symbiotic association between cnidarian hosts and unicellular dinoflagellate algae, known as zooxanthellae. These algae are photosynthetic and the cnidarian-zooxanthellae association is based on nutritional exchanges. Maintenance of such an intimate cellular partnership involves many crosstalks between the partners. To better characterize symbiotic relationships between a cnidarian host and its dinoflagellate symbionts, we conducted a large-scale EST study on a symbiotic sea anemone, Anemonia viridis, in which the two tissue layers (epiderm and gastroderm) can be easily separated. A single cDNA library was constructed from symbiotic tissue of sea anemones A. viridis in various environmental conditions (both normal and stressed). We generated 39,939 high quality ESTs, which were assembled into 14,504 unique sequences (UniSeqs). Sequences were analysed and sorted according to their putative origin (animal, algal or bacterial). We identified many new repeated elements in the 3'UTR of most animal genes, suggesting that these elements potentially have a biological role, especially with respect to gene expression regulation. We identified genes of animal origin that have no homolog in the non-symbiotic starlet sea anemone Nematostella vectensis genome, but in other symbiotic cnidarians, and may therefore be involved in the symbiosis relationship in A. viridis. Comparison of protein domain occurrence in A. viridis with that in N. vectensis demonstrated an increase in abundance of some molecular functions, such as protein binding or antioxidant activity, suggesting that these functions are essential for the symbiotic state and may be specific adaptations. This large dataset of sequences provides a valuable resource for future studies on symbiotic interactions in Cnidaria. The comparison with the closest available genome, the sea anemone N. vectensis, as well as

  15. Comprehensive EST analysis of the symbiotic sea anemone, Anemonia viridis

    PubMed Central

    Sabourault, Cécile; Ganot, Philippe; Deleury, Emeline; Allemand, Denis; Furla, Paola

    2009-01-01

    Background Coral reef ecosystems are renowned for their diversity and beauty. Their immense ecological success is due to a symbiotic association between cnidarian hosts and unicellular dinoflagellate algae, known as zooxanthellae. These algae are photosynthetic and the cnidarian-zooxanthellae association is based on nutritional exchanges. Maintenance of such an intimate cellular partnership involves many crosstalks between the partners. To better characterize symbiotic relationships between a cnidarian host and its dinoflagellate symbionts, we conducted a large-scale EST study on a symbiotic sea anemone, Anemonia viridis, in which the two tissue layers (epiderm and gastroderm) can be easily separated. Results A single cDNA library was constructed from symbiotic tissue of sea anemones A. viridis in various environmental conditions (both normal and stressed). We generated 39,939 high quality ESTs, which were assembled into 14,504 unique sequences (UniSeqs). Sequences were analysed and sorted according to their putative origin (animal, algal or bacterial). We identified many new repeated elements in the 3'UTR of most animal genes, suggesting that these elements potentially have a biological role, especially with respect to gene expression regulation. We identified genes of animal origin that have no homolog in the non-symbiotic starlet sea anemone Nematostella vectensis genome, but in other symbiotic cnidarians, and may therefore be involved in the symbiosis relationship in A. viridis. Comparison of protein domain occurrence in A. viridis with that in N. vectensis demonstrated an increase in abundance of some molecular functions, such as protein binding or antioxidant activity, suggesting that these functions are essential for the symbiotic state and may be specific adaptations. Conclusion This large dataset of sequences provides a valuable resource for future studies on symbiotic interactions in Cnidaria. The comparison with the closest available genome, the sea

  16. Evolutionary Instability of Symbiotic Function in Bradyrhizobium japonicum

    PubMed Central

    Sachs, Joel L.; Russell, James E.; Hollowell, Amanda C.

    2011-01-01

    Bacterial mutualists are often acquired from the environment by eukaryotic hosts. However, both theory and empirical work suggest that this bacterial lifestyle is evolutionarily unstable. Bacterial evolution outside of the host is predicted to favor traits that promote an independent lifestyle in the environment at a cost to symbiotic function. Consistent with these predictions, environmentally-acquired bacterial mutualists often lose symbiotic function over evolutionary time. Here, we investigate the evolutionary erosion of symbiotic traits in Bradyrhizobium japonicum, a nodulating root symbiont of legumes. Building on a previous published phylogeny we infer loss events of nodulation capability in a natural population of Bradyrhizobium, potentially driven by mutation or deletion of symbiosis loci. Subsequently, we experimentally evolved representative strains from the symbiont population under host-free in vitro conditions to examine potential drivers of these loss events. Among Bradyrhizobium genotypes that evolved significant increases in fitness in vitro, two exhibited reduced symbiotic quality, but no experimentally evolved strain lost nodulation capability or evolved any fixed changes at six sequenced loci. Our results are consistent with trade-offs between symbiotic quality and fitness in a host free environment. However, the drivers of loss-of-nodulation events in natural Bradyrhizobium populations remain unknown. PMID:22073160

  17. Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.

    PubMed

    Sachs, Joel L; Russell, James E; Hollowell, Amanda C

    2011-01-01

    Bacterial mutualists are often acquired from the environment by eukaryotic hosts. However, both theory and empirical work suggest that this bacterial lifestyle is evolutionarily unstable. Bacterial evolution outside of the host is predicted to favor traits that promote an independent lifestyle in the environment at a cost to symbiotic function. Consistent with these predictions, environmentally-acquired bacterial mutualists often lose symbiotic function over evolutionary time. Here, we investigate the evolutionary erosion of symbiotic traits in Bradyrhizobium japonicum, a nodulating root symbiont of legumes. Building on a previous published phylogeny we infer loss events of nodulation capability in a natural population of Bradyrhizobium, potentially driven by mutation or deletion of symbiosis loci. Subsequently, we experimentally evolved representative strains from the symbiont population under host-free in vitro conditions to examine potential drivers of these loss events. Among Bradyrhizobium genotypes that evolved significant increases in fitness in vitro, two exhibited reduced symbiotic quality, but no experimentally evolved strain lost nodulation capability or evolved any fixed changes at six sequenced loci. Our results are consistent with trade-offs between symbiotic quality and fitness in a host free environment. However, the drivers of loss-of-nodulation events in natural Bradyrhizobium populations remain unknown.

  18. Fighting malaria with engineered symbiotic bacteria from vector mosquitoes.

    PubMed

    Wang, Sibao; Ghosh, Anil K; Bongio, Nicholas; Stebbings, Kevin A; Lampe, David J; Jacobs-Lorena, Marcelo

    2012-07-31

    The most vulnerable stages of Plasmodium development occur in the lumen of the mosquito midgut, a compartment shared with symbiotic bacteria. Here, we describe a strategy that uses symbiotic bacteria to deliver antimalaria effector molecules to the midgut lumen, thus rendering host mosquitoes refractory to malaria infection. The Escherichia coli hemolysin A secretion system was used to promote the secretion of a variety of anti-Plasmodium effector proteins by Pantoea agglomerans, a common mosquito symbiotic bacterium. These engineered P. agglomerans strains inhibited development of the human malaria parasite Plasmodium falciparum and rodent malaria parasite Plasmodium berghei by up to 98%. Significantly, the proportion of mosquitoes carrying parasites (prevalence) decreased by up to 84% for two of the effector molecules, scorpine, a potent antiplasmodial peptide and (EPIP)(4), four copies of Plasmodium enolase-plasminogen interaction peptide that prevents plasminogen binding to the ookinete surface. We demonstrate the use of an engineered symbiotic bacterium to interfere with the development of P. falciparum in the mosquito. These findings provide the foundation for the use of genetically modified symbiotic bacteria as a powerful tool to combat malaria.

  19. Fighting malaria with engineered symbiotic bacteria from vector mosquitoes

    PubMed Central

    Wang, Sibao; Ghosh, Anil K.; Bongio, Nicholas; Stebbings, Kevin A.; Lampe, David J.; Jacobs-Lorena, Marcelo

    2012-01-01

    The most vulnerable stages of Plasmodium development occur in the lumen of the mosquito midgut, a compartment shared with symbiotic bacteria. Here, we describe a strategy that uses symbiotic bacteria to deliver antimalaria effector molecules to the midgut lumen, thus rendering host mosquitoes refractory to malaria infection. The Escherichia coli hemolysin A secretion system was used to promote the secretion of a variety of anti-Plasmodium effector proteins by Pantoea agglomerans, a common mosquito symbiotic bacterium. These engineered P. agglomerans strains inhibited development of the human malaria parasite Plasmodium falciparum and rodent malaria parasite Plasmodium berghei by up to 98%. Significantly, the proportion of mosquitoes carrying parasites (prevalence) decreased by up to 84% for two of the effector molecules, scorpine, a potent antiplasmodial peptide and (EPIP)4, four copies of Plasmodium enolase–plasminogen interaction peptide that prevents plasminogen binding to the ookinete surface. We demonstrate the use of an engineered symbiotic bacterium to interfere with the development of P. falciparum in the mosquito. These findings provide the foundation for the use of genetically modified symbiotic bacteria as a powerful tool to combat malaria. PMID:22802646

  20. Expulsion of zooxanthellae by symbiotic cnidarians from the Red Sea

    NASA Astrophysics Data System (ADS)

    Hoegh-Guldberg, O.; McCloskey, L. R.; Muscatine, L.

    1987-04-01

    The expulsion of zooxanthellae by octocorals ( Xenia macrospiculata and Heteroxenia fuscescens), the scleractinian coral Stylophora pistillata, and the hydrocoral Millepora dichotoma, was measured in the field. The numbers expelled did not exceed 0.1% of the total standing stock of symbiotic algae per day, the rate of expulsion was less than 4% of the rate at which cells are added to symbiotic populations, and the carbon lost represented 0.01% of the total carbon fixed on a daily basis. Expulsion of zooxanthellae is therefore not a significant sink for fixed carbon in these symbiotic associations. In contrast to field populations, expulsion by X. macrospiculata increased 5-fold or more in the laboratory, suggesting that laboratory conditions may introduce stress.

  1. Morphological and genetic diversity of symbiotic cyanobacteria from cycads.

    PubMed

    Thajuddin, Nooruddin; Muralitharan, Gangatharan; Sundaramoorthy, Mariappan; Ramamoorthy, Rengasamy; Ramachandran, Srinivasan; Akbarsha, Mohamed Abdulkadar; Gunasekaran, Muthukumaran

    2010-06-01

    The morphological and genetic diversity of cyanobacteria associated with cycads was examined using PCR amplification techniques and 16S rRNA gene sequence analysis. Eighteen symbiotic cyanobacteria were isolated from different cycad species. One of the symbiotic isolates was a species of Calothrix, a genus not previously reported to form symbioses with Cycadaceae family, and the remainder were Nostoc spp. Axenic cyanobacterial strains were compared by DNA amplification using PCR with either short arbitrary primers or primers specific for the repetitive sequences. Based on fingerprint patterns and phenograms, it was revealed that cyanobacterial symbionts exhibit important genetic diversity among host plants, both within and between cycad populations. A phylogenetic analysis based on 16S rRNA gene sequence analysis revealed that most of the symbiotic cyanobacterial isolates fell into well-separated clades.

  2. Formation of broad Balmer wings in symbiotic stars

    NASA Astrophysics Data System (ADS)

    Chang, Seok-Jun; Heo, Jeong-Eun; Hong, Chae-Lin; Lee, Hee-Won

    2016-07-01

    Symbiotic stars are binary systems composed of a hot white dwarf and a mass losing giant. In addition to many prominent emission lines symbiotic stars exhibit Raman scattered O VI features at 6825 and 7088 Å. Another notable feature present in the spectra of many symbiotics is the broad wings around Balmer lines. Astrophysical mechanisms that can produce broad wings include Thomson scattering by free electrons and Raman scattering of Ly,β and higher series by neutral hydrogen. In this poster presentation we produce broad wings around Hα and H,β adopting a Monte Carlo techinique in order to make a quantitative comparison of these two mechanisms. Thomson wings are characterized by the exponential cutoff given by the termal width whereas the Raman wings are dependent on the column density and continuum shape in the far UV region. A brief discussion is provided.

  3. Dynamic task allocation for a man-machine symbiotic system

    NASA Technical Reports Server (NTRS)

    Parker, L. E.; Pin, F. G.

    1987-01-01

    This report presents a methodological approach to the dynamic allocation of tasks in a man-machine symbiotic system in the context of dexterous manipulation and teleoperation. This report addresses a symbiotic system containing two symbiotic partners which work toward controlling a single manipulator arm for the execution of a series of sequential manipulation tasks. It is proposed that an automated task allocator use knowledge about the constraints/criteria of the problem, the available resources, the tasks to be performed, and the environment to dynamically allocate task recommendations for the man and the machine. The presentation of the methodology includes discussions concerning the interaction of the knowledge areas, the flow of control, the necessary communication links, and the replanning of the task allocation. Examples of task allocation are presented to illustrate the results of this methodolgy.

  4. Arthropod symbiotes of Laonastes aenigmamus (Rodentia:Diatomyidae).

    PubMed

    Bochkov, A V; Abramov, A V; Durden, L A; Apanaskevich, D A; Stekolnikov, A A; Stanyukovich, M K; Gnophanxay, S; Tikhonov, A N

    2011-04-01

    Arthropod symbiotes of the Laotian rock-rat, Laonastes aenigmamus (Rodentia:Diatomyidae), from Laos are examined. This host is a member of Diatomyidae previously thought to have gone extinct >10 million yr ago. Permanent symbiotes are represented by 2 species, a new species of sucking louse, Polyplax sp., near rhizomydis (Phthiraptera:Polyplacidae), and a new species of fur mite, Afrolistrophorus sp., near maculatus (Acariformes:Listrophoridae). The temporary parasites are represented by 18 species, i.e., 1 mesostigmatan species, i.e., a new species of Androlaelaps near casalis (Parasitiformes:Laelapidae); immature stages of 2 tick species, Ixodes granulatus and Haemaphysalis sp. (Parasitiformes:Ixodidae); and a rich fauna of chiggers (Acariformes:Trombiculidae) comprising 8 genera and 15 species. It is hypothesized that this host completely lost its initial fauna of ectosymbiotes and that ancestors of the recorded symbiotes switched to this host from rodents of the superfamily Muroidea.

  5. Symbiotic relationship of Thiothrix spp. with an echinoderm

    SciTech Connect

    Brigmon, R.L.; De Ridder, C.

    1998-09-01

    Thiothrix-like bacteria have been reported as symbionts in invertebrates from sulfide-rich habitats. Isolation of these symbiotic Thiothrix-like bacteria has failed, and the organisms have not been previously identified with certainty. The genus Thiothrix was created for ensheathed filamentous bacteria that oxidize sulfide and deposit sulfur granules internally, attach to substrates, produce gliding gonidia, and form rosettes. Immunoassay procedures were used to investigate the symbiotic relationship of Thiothrix spp. in the intestinal cecum of the spatangoid species Echinocardium cordatum. Thiothrix spp. were identified in nodule samples from E. cordatum digestive tubes based on microscopic examination, enzyme-linked immunosorbent assay, and indirect immunofluorescence. Thiothrix spp. protein made up as much as 84% of the total protein content of the nodules. This is the first identification of Thiothrix spp. internally symbiotic with marine invertebrates.

  6. Computer symbiosis-emergence of symbiotic behavior through evolution

    NASA Astrophysics Data System (ADS)

    Ikegami, Takashi; Kaneko, Kunihiko

    1990-06-01

    Symbiosis is cooperation between distinct species. It is one of the most effective evolutionary processes, but its dynamics are not well understood as yet. A simple model of symbiosis is introduced, in which we consider interactions between hosts and parasites and also mutations of hosts and parasites. The interactions and mutations form a dynamical system on the populations of hosts and parasites. It is found that a symbiotic state emerges for a suitable range of mutation rates. The symbiotic state is not static, but dynamically oscillates. Harmful parasites violating symbiosis appear periodically, but are rapidly extinguished by hosts and other parasites, and the symbiotic state is recovered. The relation between these phenomena and “TIT for TAT” strategy to maintain symbiosis is discussed.

  7. Nodulation outer proteins: double-edged swords of symbiotic rhizobia.

    PubMed

    Staehelin, Christian; Krishnan, Hari B

    2015-09-15

    Rhizobia are nitrogen-fixing bacteria that establish a nodule symbiosis with legumes. Nodule formation depends on signals and surface determinants produced by both symbiotic partners. Among them, rhizobial Nops (nodulation outer proteins) play a crucial symbiotic role in many strain-host combinations. Nops are defined as proteins secreted via a rhizobial T3SS (type III secretion system). Functional T3SSs have been characterized in many rhizobial strains. Nops have been identified using various genetic, biochemical, proteomic, genomic and experimental approaches. Certain Nops represent extracellular components of the T3SS, which are visible in electron micrographs as bacterial surface appendages called T3 (type III) pili. Other Nops are T3 effector proteins that can be translocated into plant cells. Rhizobial T3 effectors manipulate cellular processes in host cells to suppress plant defence responses against rhizobia and to promote symbiosis-related processes. Accordingly, mutant strains deficient in synthesis or secretion of T3 effectors show reduced symbiotic properties on certain host plants. On the other hand, direct or indirect recognition of T3 effectors by plant cells expressing specific R (resistance) proteins can result in effector triggered defence responses that negatively affect rhizobial infection. Hence Nops are double-edged swords that may promote establishment of symbiosis with one legume (symbiotic factors) and impair symbiotic processes when bacteria are inoculated on another legume species (asymbiotic factors). In the present review, we provide an overview of our current understanding of Nops. We summarize their symbiotic effects, their biochemical properties and their possible modes of action. Finally, we discuss future perspectives in the field of T3 effector research. © 2015 Authors; published by Portland Press Limited.

  8. Failure to fix nitrogen by non-reproductive symbiotic rhizobia triggers host sanctions that reduce fitness of their reproductive clonemates.

    PubMed

    Oono, Ryoko; Anderson, Carolyn G; Denison, R Ford

    2011-09-07

    The legume-rhizobia symbiosis is a classical mutualism where fixed carbon and nitrogen are exchanged between the species. Nonetheless, the plant carbon that fuels nitrogen (N(2)) fixation could be diverted to rhizobial reproduction by 'cheaters'--rhizobial strains that fix less N(2) but potentially gain the benefit of fixation by other rhizobia. Host sanctions can decrease the relative fitness of less-beneficial reproductive bacteroids and prevent cheaters from breaking down the mutualism. However, in certain legume species, only undifferentiated rhizobia reproduce, while only terminally differentiated rhizobial bacteroids fix nitrogen. Sanctions were, therefore, tested in two legume species that host non-reproductive bacteroids. We demonstrate that even legume species that host non-reproductive bacteroids, specifically pea and alfalfa, can severely sanction undifferentiated rhizobia when bacteroids within the same nodule fail to fix N(2). Hence, host sanctions by a diverse set of legumes play a role in maintaining N(2) fixation.

  9. The B[e] Phenomenon in Symbiotic Binaries

    NASA Astrophysics Data System (ADS)

    Skopal, A.

    2017-02-01

    The spectrum of symbiotic stars (SSs) consists of three basic components of radiation. Two are stellar in nature are produced by the binary components, the evolved cool giant and the hot compact component, whereas the third one is the nebular in nature being rich for emission lines. An additional component from a dust is observed in the near-IR spectrum of the so-called D-type (dusty) SSs. In this contribution I introduce the basic physical processes responsible for the symbiotic phenomenon, model the composite spectrum, and point to a striking similarity of the configuration of B[e] supergiants with that of the hot components during outbursts of SSs.

  10. Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms

    PubMed Central

    Sulieman, Saad; Tran, Lam-Son Phan

    2014-01-01

    The special issue “Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms” aims to investigate the physiological and biochemical advances in the symbiotic process with an emphasis on nodule establishment, development and functioning. The original research articles included in this issue provide important information regarding novel aspects of nodule metabolism and various regulatory pathways, which could have important future implications. This issue also included one review article that highlights the importance of using legume trees in the production of renewable biofuels. PMID:25347276

  11. He 2-104 - A symbiotic proto-planetary nebula?

    NASA Technical Reports Server (NTRS)

    Schwarz, Hugo E.; Aspin, Colin; Lutz, Julie H.

    1989-01-01

    CCD observations are presented for He 2-104, an object previously classified as both PN and symbiotic star, which show that this is in fact a protoplanetary nebula (PPN) with a dynamical age of about 800 yr. The presence of highly collimated jets, extending over 75 arcsec on the sky, combined with an energy distribution showing a hot as well as a cool component, indicates that He 2-104 is a binary PPN. Since the primary is probably a Mira with a 400-d period (as reported by Whitelock, 1988), it is proposed that the system is a symbiotic PPN.

  12. He 2-104 - A symbiotic proto-planetary nebula?

    NASA Technical Reports Server (NTRS)

    Schwarz, Hugo E.; Aspin, Colin; Lutz, Julie H.

    1989-01-01

    CCD observations are presented for He 2-104, an object previously classified as both PN and symbiotic star, which show that this is in fact a protoplanetary nebula (PPN) with a dynamical age of about 800 yr. The presence of highly collimated jets, extending over 75 arcsec on the sky, combined with an energy distribution showing a hot as well as a cool component, indicates that He 2-104 is a binary PPN. Since the primary is probably a Mira with a 400-d period (as reported by Whitelock, 1988), it is proposed that the system is a symbiotic PPN.

  13. Symbiotic fungal associations in 'lower' land plants.

    PubMed Central

    Read, D J; Ducket, J G; Francis, R; Ligron, R; Russell, A

    2000-01-01

    An analysis of the current state of knowledge of symbiotic fungal associations in 'lower' plants is provided. Three fungal phyla, the Zygomycota, Ascomycota and Basidiomycota, are involved in forming these associations, each producing a distinctive suite of structural features in well-defined groups of 'lower' plants. Among the 'lower' plants only mosses and Equisetum appear to lack one or other of these types of association. The salient features of the symbioses produced by each fungal group are described and the relationships between these associations and those formed by the same or related fungi in 'higher' plants are discussed. Particular consideration is given to the question of the extent to which root fungus associations in 'lower' plants are analogous to 'mycorrhizas' of 'higher' plants and the need for analysis of the functional attributes of these symbioses is stressed. Zygomycetous fungi colonize a wide range of extant lower land plants (hornworts, many hepatics, lycopods, Ophioglossales, Psilotales and Gleicheniaceae), where they often produce structures analogous to those seen in the vesicular-arbuscular (VA) mycorrhizas of higher plants, which are formed by members of the order Glomales. A preponderance of associations of this kind is in accordance with palaeohbotanical and molecular evidence indicating that glomalean fungi produced the archetypal symbioses with the first plants to emerge on to land. It is shown, probably for the first time, that glomalean fungi forming typical VA mycorrhiza with a higher plant (Plantago lanceolata) can colonize a thalloid liverwort (Pellia epiphylla), producing arbuscules and vesicles in the hepatic. The extent to which these associations, which are structurally analogous to mycorrhizas, have similar functions remains to be evaluated. Ascomycetous associations are found in a relatively small number of families of leafy liverworts. The structural features of the fungal colonization of rhizoids and underground axes of

  14. PU Vulpeculae: an eclipsing symbiotic nova.

    NASA Astrophysics Data System (ADS)

    Nussbaumer, H.; Vogel, M.

    1996-03-01

    A series of IUE observation from 1992 to 1995 has definitely established PU Vul as an eclipsing binary. The outburst of this symbiotic nova began in 1977. An extended fading in 1980 gave rise to various interpretations, the eclipse scenario being one of them, dust formation being another. From AFOEV and AAVSO observations we find a period of 4900+/-100days, or 13.42+/-0.27years. An eclipsing object of such a long period signifies that we see the binary system at an orbital inclination close to 90deg. ESO observations in the near infrared give an orbital velocity of 4.7km/s and a mass function of m_f_=~0.05. Assuming a white dwarf mass between 0.4Msun_ and 0.5Msun_ gives for the red giant 0.7<=M/Msun_<=1.1. From the length of the eclipse the radius of the red giant is determined as R_giant_>=82Rsun_. We discuss IUE, HST and ground based observations of PU Vulpeculae before and during its second observed eclipse of the hot component by the cool giant which lasted from 1993 to 1995, mid-eclipse was in April 1994. Line profiles, particularly those taken by HST, allow a neat distinction between narrow nebular lines and broader wind lines which prove the existence of a fast wind from the hot star in the binary system of v=~1000km/s. That wind has relatively high densities (N_e_>10^12^cm^-3^) and is optically thick to radiation at λ<228A. Nebular lines have half widths corresponding to v=~70km/s. During the 1994 eclipse the more highly ionized lines were strongly eclipsed, whereas the lowly ionized nebular lines were hardly affected. This proves that the lowly ionized nebular lines are emitted in a very extended region, and not only close to the cool giant. From 1990 to 1994 relative C/N/O abundances of the nebular and wind emission regions have not changed beyond observational uncertainties.

  15. Effect of Subliminal Stimulation of Symbiotic Fantasies on Behavior Modification Treatment of Obesity.

    ERIC Educational Resources Information Center

    And Others; Silverman, Lloyd H.

    1978-01-01

    Obese women were treated in behavior modification programs for overeating. Behavior programs were accompanied by subliminal stimulation and by symbiotic and control messages. The symbiotic condition gave evidence of enhancing weight loss. This finding supports the proposition that subliminal stimulation of symbiotic fantasies can enhance the…

  16. Medicago truncatula symbiotic peptide NCR247 contributes to bacteroid differentiation through multiple mechanisms.

    PubMed

    Farkas, Attila; Maróti, Gergely; Durgő, Hajnalka; Györgypál, Zoltán; Lima, Rui M; Medzihradszky, Katalin F; Kereszt, Attila; Mergaert, Peter; Kondorosi, Éva

    2014-04-08

    Symbiosis between rhizobia soil bacteria and legume plants results in the formation of root nodules where plant cells are fully packed with nitrogen fixing bacteria. In the host cells, the bacteria adapt to the intracellular environment and gain the ability for nitrogen fixation. Depending on the host plants, the symbiotic fate of bacteria can be either reversible or irreversible. In Medicago and related legume species, the bacteria undergo a host-directed multistep differentiation process culminating in the formation of elongated and branched polyploid bacteria with definitive loss of cell division ability. The plant factors are nodule-specific symbiotic peptides. Approximately 600 of them are nodule-specific cysteine-rich (NCR) peptides produced in the rhizobium-infected plant cells. NCRs are targeted to the endosymbionts, and concerted action of different sets of peptides governs different stages of endosymbiont maturation, whereas the symbiotic function of individual NCRs is unknown. This study focused on NCR247, a cationic peptide exhibiting in vitro antimicrobial activities. We show that NCR247 acts in those nodule cells where bacterial cell division is arrested and cell elongation begins. NCR247 penetrates the bacteria and forms complexes with many bacterial proteins. Interaction with FtsZ required for septum formation is one of the host interventions for inhibiting bacterial cell division. Complex formation with the ribosomal proteins affects translation and contributes to altered proteome and physiology of the endosymbiont. Binding to the chaperone GroEL amplifies the NCR247-modulated biological processes. We show that GroEL1 of Sinorhizobium meliloti is required for efficient infection, terminal differentiation, and nitrogen fixation.

  17. Oxidative burst in alfalfa-Sinorhizobium meliloti symbiotic interaction.

    PubMed

    Santos, R; Hérouart, D; Sigaud, S; Touati, D; Puppo, A

    2001-01-01

    Reactive oxygen species are produced as an early event in plant defense response against avirulent pathogens. We show here that alfalfa responds to infection with Sinorhizobium meliloti by production of superoxide and hydrogen peroxide. This similarity in the early response to infection by pathogenic and symbiotic bacteria addresses the question of which mechanism rhizobia use to counteract the plant defense response.

  18. Nodulation outer proteins: double-edged swords of symbiotic rhizobia

    USDA-ARS?s Scientific Manuscript database

    Rhizobia are nitrogen-fixing bacteria that establish a nodule symbiosis with legumes. Nodule formation is the result of a complex bacterial infection process, which depends on signals and surface determinants produced by both symbiotic partners. Among them, rhizobial nodulation outer proteins (Nops)...

  19. Towards the minimal nitrogen-fixing symbiotic genome.

    PubMed

    Sanjuán, Juan

    2016-09-01

    diCenzo and coworkers have reverse engineered a rhizobium into a non-nitrogen fixer, creating a genomic platform for gain-of-function genetics studies, which should aid to identify the minimal nitrogen fixing symbiotic genome. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  20. Request for regular monitoring of the symbiotic variable RT Cru

    NASA Astrophysics Data System (ADS)

    Waagen, Elizabeth O.

    2014-08-01

    Dr. Margarita Karovska (Harvard-Smithsonian Center for Astrophysics) and colleagues have requested AAVSO observer assistance in their campaign on the symbiotic variable RT Cru (member of a new class of hard X-ray emitting symbiotic binaries). Weekly or more frequent monitoring (B, V, and visual) beginning now is requested in support of upcoming Chandra observations still to be scheduled. "We plan Chandra observations of RT Cru in the near future that will help us understand the characteristics of the accretion onto the white dwarf in this sub-class of symbiotics. This is an important step for determining the precursor conditions for formation of a fraction of asymmetric Planetary Nebulae, and the potential of symbiotic systems as progenitors of at least a fraction of Type Ia supernovae." Finder charts with sequence may be created using the AAVSO Variable Star Plotter (http://www.aavso.org/vsp). Observations should be submitted to the AAVSO International Database. See full Alert Notice for more details and observations.

  1. A New Active Stage of the Symbiotic Star CH Cygni

    NASA Astrophysics Data System (ADS)

    Iijima, Takashi

    2017-03-01

    The spectral variation of the symbiotic star CH Cygni has been monitored at Asiago Astrophysical Observatory using the 1.22m Galileo telescope. Recently, P Cygni type high velocity absorption components appeared on the H I Balmer lines, which were not seen in early December 2016.

  2. Optical Variability of X-Ray Bright Southern Symbiotic Stars

    NASA Astrophysics Data System (ADS)

    Hedrick, C.; Sokoloski, J.

    2004-12-01

    We performed weekly B- and V-band observations of four X-ray bright southern symbiotic binary stars -- CD-43 14304, Hen 3-1591, LMC S63, and SMC LN 358 -- using the 1.3-m telescope at Cerro Tololo Inter-American Observatory (CTIO). We began optical monitoring in August 2003 for two of the objects (LMC S63 and SMC LN 358) and in January 2004 for the other two objects (CD-43 14304 and Hen 3-1591). None of the four survey objects experienced a major outburst during the monitoring period. We did, however, detect small-amplitude ( 0.1 mag) optical variability on a time scale of tens of days, for the first time, in each of the four systems. Both the structure and amplitude of the variations are roughly the same in the B band and V band in all of the symbiotics in our sample except one (LMC S63), and is most consistent with the idea that the week-time-scale variability originates with the hot component (most likely an accreting white dwarf) rather than the red giant. We compare the variability properties of our small sample of X-ray-bright symbiotic stars to those of samples of both X-ray-bright and X-ray-dim symbiotic stars from the database of the American Association of Variable Star Observers (AAVSO).

  3. Insect symbiotic bacteria harbour viral pathogens for transovarial transmission.

    PubMed

    Jia, Dongsheng; Mao, Qianzhuo; Chen, Yong; Liu, Yuyan; Chen, Qian; Wu, Wei; Zhang, Xiaofeng; Chen, Hongyan; Li, Yi; Wei, Taiyun

    2017-03-06

    Many insects, including mosquitoes, planthoppers, aphids and leafhoppers, are the hosts of bacterial symbionts and the vectors for transmitting viral pathogens(1-3). In general, symbiotic bacteria can indirectly affect viral transmission by enhancing immunity and resistance to viruses in insects(3-5). Whether symbiotic bacteria can directly interact with the virus and mediate its transmission has been unknown. Here, we show that an insect symbiotic bacterium directly harbours a viral pathogen and mediates its transovarial transmission to offspring. We observe rice dwarf virus (a plant reovirus) binding to the envelopes of the bacterium Sulcia, a common obligate symbiont of leafhoppers(6-8), allowing the virus to exploit the ancient oocyte entry path of Sulcia in rice leafhopper vectors. Such virus-bacterium binding is mediated by the specific interaction of the viral capsid protein and the Sulcia outer membrane protein. Treatment with antibiotics or antibodies against Sulcia outer membrane protein interferes with this interaction and strongly prevents viral transmission to insect offspring. This newly discovered virus-bacterium interaction represents the first evidence that a viral pathogen can directly exploit a symbiotic bacterium for its transmission. We believe that such a model of virus-bacterium communication is a common phenomenon in nature.

  4. Competitive interactions among symbiotic fungi of the southern pine beetle

    Treesearch

    Kier D. Klepzig; Richard T. Wilkens

    1997-01-01

    The southern pine beetle, a damaging pest of conifers, is intimately linked to three symbiotic fungi.Two fungi, Ceratocystiopsis ranaculosus and Entomocorticium sp. A, are transported within specialized structures (mycangia) in the beetle exoskeleton and are mutualists of the beetle.A third fungus, Ophiostoma minus, is transported externally on the beetle exoskeleton (...

  5. SYMBIOTIC STAR BLOWS BUBBLES INTO SPACE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A tempestuous relationship between an unlikely pair of stars may have created an oddly shaped, gaseous nebula that resembles an hourglass nestled within an hourglass. Images taken with Earth-based telescopes have shown the larger, hourglass-shaped nebula. But this picture, taken with NASA's Hubble Space Telescope, reveals a small, bright nebula embedded in the center of the larger one (close-up of nebula in inset). Astronomers have dubbed the entire nebula the 'Southern Crab Nebula' (He2-104), because, from ground-based telescopes, it looks like the body and legs of a crab. The nebula is several light-years long. The possible creators of these shapes cannot be seen at all in this Wide Field and Planetary Camera 2 image. It's a pair of aging stars buried in the glow of the tiny, central nebula. One of them is a red giant, a bloated star that is exhausting its nuclear fuel and is shedding its outer layers in a powerful stellar wind. Its companion is a hot, white dwarf, a stellar zombie of a burned-out star. This odd duo of a red giant and a white dwarf is called a symbiotic system. The red giant is also a Mira Variable, a pulsating red giant, that is far away from its partner. It could take as much as 100 years for the two to orbit around each other. Astronomers speculate that the interaction between these two stars may have sparked episodic outbursts of material, creating the gaseous bubbles that form the nebula. They interact by playing a celestial game of 'catch': as the red giant throws off its bulk in a powerful stellar wind, the white dwarf catches some of it. As a result, an accretion disk of material forms around the white dwarf and spirals onto its hot surface. Gas continues to build up on the surface until it sparks an eruption, blowing material into space. This explosive event may have happened twice in the 'Southern Crab.' Astronomers speculate that the hourglass-shaped nebulae represent two separate outbursts that occurred several thousand years apart

  6. SYMBIOTIC STAR BLOWS BUBBLES INTO SPACE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A tempestuous relationship between an unlikely pair of stars may have created an oddly shaped, gaseous nebula that resembles an hourglass nestled within an hourglass. Images taken with Earth-based telescopes have shown the larger, hourglass-shaped nebula. But this picture, taken with NASA's Hubble Space Telescope, reveals a small, bright nebula embedded in the center of the larger one (close-up of nebula in inset). Astronomers have dubbed the entire nebula the 'Southern Crab Nebula' (He2-104), because, from ground-based telescopes, it looks like the body and legs of a crab. The nebula is several light-years long. The possible creators of these shapes cannot be seen at all in this Wide Field and Planetary Camera 2 image. It's a pair of aging stars buried in the glow of the tiny, central nebula. One of them is a red giant, a bloated star that is exhausting its nuclear fuel and is shedding its outer layers in a powerful stellar wind. Its companion is a hot, white dwarf, a stellar zombie of a burned-out star. This odd duo of a red giant and a white dwarf is called a symbiotic system. The red giant is also a Mira Variable, a pulsating red giant, that is far away from its partner. It could take as much as 100 years for the two to orbit around each other. Astronomers speculate that the interaction between these two stars may have sparked episodic outbursts of material, creating the gaseous bubbles that form the nebula. They interact by playing a celestial game of 'catch': as the red giant throws off its bulk in a powerful stellar wind, the white dwarf catches some of it. As a result, an accretion disk of material forms around the white dwarf and spirals onto its hot surface. Gas continues to build up on the surface until it sparks an eruption, blowing material into space. This explosive event may have happened twice in the 'Southern Crab.' Astronomers speculate that the hourglass-shaped nebulae represent two separate outbursts that occurred several thousand years apart

  7. Characteristics of the hot components of symbiotic stars

    NASA Astrophysics Data System (ADS)

    Burmeister, Mari

    2010-08-01

    Symbiotic stars are interacting binaries whose components are a red giant and a small hot star, usually a white dwarf. The intensive stellar wind from the giant is captured by the companion, giving rise to strong emission lines in the spectra and a range of phenomena, which may include the formation of an accretion disk and the ejection of collimated jets. In this thesis, four symbiotic stars, as different as possible, were chosen for a spectral investigation of the symbiotic phenomenon. Of those, Z Andromedae is a so-called classical symbiotic star with a hot companion that shows a characteristic pattern of brightenings (outbursts). AG Draconis is a bright system like Z Andromedae and shows similar activity, but has an unusually hot yellow donor star. CH Cygni and EG Andromedae have, on the contrary, relatively dim white dwarfs. The former shows irregular outbursts, the origin of which is not easy to explain, the latter is one of the quiet symbiotic stars with no outburst yet recorded. Each of those four stars was observed for at least ten years with the 1.5-m telescope at Tartu Observatory. Several outbursts of Z Andromedae and AG Draconis were witnessed, as well as substantial changes in the CH Cygni spectra. The perhaps most surprising result was the discovery of collimated jets in Z Andromedae spectra on two instances, an event never observed in this star before. In CH Cygni, evidence for the existence of an accretion disk in 1998 was discovered. EG Andromedae stayed quiet and the only changes in its spectra could be ascribed to orbital motion. We found that not all the outbursts of Z Andromedae and AG Draconis are accompanied by similar changes in the spectra: during some brightenings the stars become hotter, during some, cooler. The existence of the disk in CH Cygni in 1998 affirms that the formation of such a structure is possible in symbiotic stars. Moreover, as the ejection of jets is associated to an accretion disk, the jets in Z Andromedae can also be

  8. Molecular and biochemical analysis of symbiotic plant receptor kinase complexes

    SciTech Connect

    Cook, Douglas R; Riely, Brendan K

    2010-09-01

    DE-FG02-01ER15200 was a 36-month project, initiated on Sept 1, 2005 and extended with a one-year no cost extension to August 31, 2009. During the project period we published seven manuscripts (2 in review). Including the prior project period (2002-2005) we published 12 manuscripts in journals that include Science, PNAS, The Plant Cell, Plant Journal, Plant Physiology, and MPMI. The primary focus of this work was to further elucidate the function of the Nod factor signaling pathway that is involved in initiation of the legume-rhizobium symbiosis and in particular to explore the relationship between receptor kinase-like proteins and downstream effectors of symbiotic development. During the project period we have map-base cloned two additional players in symbiotic development, including an ERF transcription factor and an ethylene pathway gene (EIN2) that negatively regulates symbiotic signaling; we have also further characterized the subcellular distribution and function of a nuclear-localized symbiosis-specific ion channel, DMI1. The major outcome of the work has been the development of systems for exploring and validating protein-protein interactions that connect symbiotic receptor-like proteins to downstream responses. In this regard, we have developed both homologous (i.e., in planta) and heterologous (i.e., in yeast) systems to test protein interactions. Using yeast 2-hybrid screens we isolated the only known interactor of the nuclear-localized calcium-responsive kinase DMI3. We have also used yeast 2-hybrid methodology to identify interactions between symbiotic signaling proteins and certain RopGTPase/RopGEF proteins that regulate root hair polar growth. More important to the long-term goals of our work, we have established a TAP tagging system that identifies in planta interactions based on co-immuno precipitation and mass spectrometry. The validity of this approach has been shown using known interactors that either co-iummnoprecipate (i.e., remorin) or co

  9. SIMULATIONS OF THE SYMBIOTIC RECURRENT NOVA V407 CYG. I. ACCRETION AND SHOCK EVOLUTIONS

    SciTech Connect

    Pan, Kuo-Chuan; Ricker, Paul M.; Taam, Ronald E. E-mail: pmricker@illinois.edu E-mail: taam@asiaa.sinica.edu.tw

    2015-06-10

    The shock interaction and evolution of nova ejecta with wind from a red giant (RG) star in a symbiotic binary system are investigated via three-dimensional hydrodynamics simulations. We specifically model the 2010 March outburst of the symbiotic recurrent nova V407 Cygni from its quiescent phase to its eruption phase. The circumstellar density enhancement due to wind–white-dwarf interaction is studied in detail. It is found that the density-enhancement efficiency depends on the ratio of the orbital speed to the RG wind speed. Unlike another recurrent nova, RS Ophiuchi, we do not observe a strong disk-like density enhancement, but instead observe an aspherical density distribution with ∼20% higher density in the equatorial plane than at the poles. To model the 2010 outburst, we consider several physical parameters, including the RG mass-loss rate, nova eruption energy, and ejecta mass. A detailed study of the shock interaction and evolution reveals that the interaction of shocks with the RG wind generates strong Rayleigh–Taylor instabilities. In addition, the presence of the companion and circumstellar density enhancement greatly alter the shock evolution during the nova phase. Depending on the model, the ejecta speed after sweeping out most of the circumstellar medium decreases to ∼100–300 km s{sup −1}, which is consistent with the observed extended redward emission in [N ii] lines in 2011 April.

  10. Rhizobium cellulase CelC2 is essential for primary symbiotic infection of legume host roots

    PubMed Central

    Robledo, M.; Jiménez-Zurdo, J. I.; Velázquez, E.; Trujillo, M. E.; Zurdo-Piñeiro, J. L.; Ramírez-Bahena, M. H.; Ramos, B.; Díaz-Mínguez, J. M.; Dazzo, F.; Martínez-Molina, E.; Mateos, P. F.

    2008-01-01

    The rhizobia–legume, root-nodule symbiosis provides the most efficient source of biologically fixed ammonia fertilizer for agricultural crops. Its development involves pathways of specificity, infectivity, and effectivity resulting from expressed traits of the bacterium and host plant. A key event of the infection process required for development of this root-nodule symbiosis is a highly localized, complete erosion of the plant cell wall through which the bacterial symbiont penetrates to establish a nitrogen-fixing, intracellular endosymbiotic state within the host. This process of wall degradation must be delicately balanced to avoid lysis and destruction of the host cell. Here, we describe the purification, biochemical characterization, molecular genetic analysis, biological activity, and symbiotic function of a cell-bound bacterial cellulase (CelC2) enzyme from Rhizobium leguminosarum bv. trifolii, the clover-nodulating endosymbiont. The purified enzyme can erode the noncrystalline tip of the white clover host root hair wall, making a localized hole of sufficient size to allow wild-type microsymbiont penetration. This CelC2 enzyme is not active on root hairs of the nonhost legume alfalfa. Microscopy analysis of the symbiotic phenotypes of the ANU843 wild type and CelC2 knockout mutant derivative revealed that this enzyme fulfils an essential role in the primary infection process required for development of the canonical nitrogen-fixing R. leguminosarum bv. trifolii-white clover symbiosis. PMID:18458328

  11. An Analysis on a Negotiation Model Based on Multiagent Systems with Symbiotic Learning and Evolution

    NASA Astrophysics Data System (ADS)

    Hossain, Md. Tofazzal

    This study explores an evolutionary analysis on a negotiation model based on Masbiole (Multiagent Systems with Symbiotic Learning and Evolution) which has been proposed as a new methodology of Multiagent Systems (MAS) based on symbiosis in the ecosystem. In Masbiole, agents evolve in consideration of not only their own benefits and losses, but also the benefits and losses of opponent agents. To aid effective application of Masbiole, we develop a competitive negotiation model where rigorous and advanced intelligent decision-making mechanisms are required for agents to achieve solutions. A Negotiation Protocol is devised aiming at developing a set of rules for agents' behavior during evolution. Simulations use a newly developed evolutionary computing technique, called Genetic Network Programming (GNP) which has the directed graph-type gene structure that can develop and design the required intelligent mechanisms for agents. In a typical scenario, competitive negotiation solutions are reached by concessions that are usually predetermined in the conventional MAS. In this model, however, not only concession is determined automatically by symbiotic evolution (making the system intelligent, automated, and efficient) but the solution also achieves Pareto optimal automatically.

  12. Phylogenetic diversity and symbiotic functioning in mungbean (Vigna radiata L. Wilczek) bradyrhizobia from contrast agro-ecological regions of Nepal.

    PubMed

    Risal, Chandra Prasad; Djedidi, Salem; Dhakal, Dhruba; Ohkama-Ohtsu, Naoko; Sekimoto, Hitoshi; Yokoyama, Tadashi

    2012-02-01

    Nepal consists wide range of climatic and topographical variations. Here, we explored the phylogeny of native mungbean bradyrhizobia isolated from different agro-ecological regions of Nepal and accessed their nodulation and nitrogen fixation characteristics. Soil samples were collected from three agro-ecological regions with contrasting climate and topography. A local mungbean cultivar, Kalyan, was used as a trap plant. We characterized isolates based on the full nucleotide sequence of the 16S rRNA, ITS region, and nodA genes; and partial sequences of nodD1 and nifD genes. We found 50% of isolates phylogenetically related to B. yuanmingense, 13% to B. japonicum, 8% to B. elkanii, and 29% to novel phylogenetic origin. Results of the inoculation test suggested that expression of different symbiotic genes in isolates resulted in different degrees of symbiotic functioning. Our results indicate B. yuanmingense and novel strains are more efficient symbiotic partners than B. elkanii for the local mungbean cv. Kalyan. We also found most mungbean rhizobial genotypes were conserved across agro-ecological regions. All the strains from tropical Terai region belonged to B. yuanmingense or a novel lineage of B. yuanmingense, and dominance of B. japonicum related strains was observed in the Hill region. Higher genetic diversity of Bradyrhizobium strains was observed in temperate and sub-tropical region than in the tropical region. Copyright © 2011 Elsevier GmbH. All rights reserved.

  13. Identification and assessment of symbiotic effectiveness of phage-typed Rhizobium leguminosarum strains on lentil (Lens culinaris Medik) cultivars.

    PubMed

    Jaiswal, Sanjay Kumar; Dhar, Banshi

    2011-05-01

    Symbiotic effectiveness of 19 indigenous and two exotic (USDA 2426 and USDA 2431) strains of lentil Rhizobium belonging to different phage-sensitive and phage-resistant groups was compared under axenic condition. Four strains (USDA 2431, BHULR 104, BHULR 113, and BHULR 115) sensitive to different phages were found significantly superior over others in terms of nodule number, acetylene reduction activity, and total dry weight per plant. Inoculation response of these strains was then evaluated on six lentil cultivars under field condition. A significant symbiotic interaction between rhizobial strains and lentil cultivars was observed. Grain yield enhancement was noticed by the compatible interaction of lentil cultivars HUL-57, L-4147, K-75, and PL-4/DPL-15/DPL-62 with rhizobial strains USDA 2431, BHULR 104, BHULR 113, and BHULR 115, respectively. The authentication of rhizobial strains was accomplished through 16S rDNA sequence analysis. All rhizobial strains had close matching with R. leguminosarum bv. viciae strains. The results have shown that phages can trustfully help selecting out the symbiotically efficient most rhizobial strains for advantageous use with lentil cultivars, in order to strengthen the BNF-based future lentil breeding programs.

  14. Obligatory symbiotic Wolbachia endobacteria are absent from Loa loa

    PubMed Central

    Büttner, Dietrich W; Wanji, Samuel; Bazzocchi, Chiara; Bain, Odile; Fischer, Peter

    2003-01-01

    Background Many filarial nematodes harbour Wolbachia endobacteria. These endobacteria are transmitted vertically from one generation to the next. In several filarial species that have been studied to date they are obligatory symbionts of their hosts. Elimination of the endobacteria by antibiotics interrupts the embryogenesis and hence the production of microfilariae. The medical implication of this being that the use of doxycycline for the treatment of human onchocerciasis and bancroftian filariasis leads to elimination of the Wolbachia and hence sterilisation of the female worms. Wolbachia play a role in the immunopathology of patients and may contribute to side effects seen after antifilarial chemotherapy. In several studies Wolbachia were not observed in Loa loa. Since these results have been doubted, and because of the medical significance, several independent methods were applied to search for Wolbachia in L. loa. Methods Loa loa and Onchocerca volvulus were studied by electron microscopy, histology with silver staining, and immunohistology using antibodies against WSP, Wolbachia aspartate aminotransferase, and heat shock protein 60. The results achieved with L. loa and O. volvulus were compared. Searching for Wolbachia, genes were amplified by PCR coding for the bacterial 16S rDNA, the FTSZ cell division protein, and WSP. Results No Wolbachia endobacteria were discovered by immunohistology in 13 male and 14 female L. loa worms and in numerous L. loa microfilariae. In contrast, endobacteria were found in large numbers in O. volvulus and 14 other filaria species. No intracellular bacteria were seen in electron micrographs of oocytes and young morulae of L. loa in contrast to O. volvulus. In agreement with these results, Wolbachia DNA was not detected by PCR in three male and six female L. loa worms and in two microfilariae samples of L. loa. Conclusions Loa loa do not harbour obligatory symbiotic Wolbachia endobacteria in essential numbers to enable their

  15. Genome-wide association analysis of diverse soybean genotypes reveals novel markers for nitrogen traits

    USDA-ARS?s Scientific Manuscript database

    Nitrogen is a primary plant nutrient that plays a major role in achieving maximum economic yield. Insufficient availability most often limits soybean crop growth. Symbiotic N2 fixation in soybean is highly sensitive to limited water availability, and breeding for reduced N2 fixation sensitivity to ...

  16. Ultraviolet observations of the symbiotic star AS 296

    NASA Technical Reports Server (NTRS)

    Gutierrez-Moreno, A.; Moreno, H.; Feibelman, W. A.

    1992-01-01

    AS 296 is a well-known S-type symbiotic star which underwent an optical outburst during 1988. In this paper, UV data based on IUE observations obtained both during the quiescent and outburst stages are presented and discussed, correlating them to observations made in the optical region. It is concluded that the object is a symbiotic nova, in which the outburst is due to a thermonuclear runaway produced in the hydrogen-burning shell of a white dwarf with M of about 0.5 solar masses, accreting from the late-type giant at a rate M(acc) of about 9.7 x 10 exp -9 solar mass/year. It is not possible to determine from the observations if the hydrogen flash is degenerate or nondegenerate.

  17. Discovery of optical flickering from the symbiotic star EF Aquilae

    NASA Astrophysics Data System (ADS)

    Zamanov, R. K.; Boeva, S.; Nikolov, Y. M.; Petrov, B.; Bachev, R.; Latev, G. Y.; Popov, V. A.; Stoyanov, K. A.; Bode, M. F.; Martí, J.; Tomov, T.; Antonova, A.

    2017-07-01

    We report optical CCD photometry of the recently identified symbiotic star EF Aql. Our observations in Johnson V and B bands clearly show the presence of stochastic light variations with an amplitude of about 0.2 mag on a time scale of minutes. The observations point toward a white dwarf (WD) as the hot component in the system. It is the 11-th object among more than 200 symbiotic stars known with detected optical flickering. Estimates of the mass accretion rate onto the WD and the mass loss rate in the wind of the Mira secondary star lead to the conclusion that less than 1 per cent of the wind is captured by the WD. Eight further candidates for the detection of flickering in similar systems are suggested.

  18. Spectrophotometric observations of symbiotic stars and related objects

    NASA Technical Reports Server (NTRS)

    Blair, W. P.; Feibelman, W. A.; Michalitsianos, A. G.; Stencel, R. E.

    1983-01-01

    Calibrated optical spectrophotometric observations of 16 symbiotic and symbiotic-like objects are presented. The objects observed include Z And, T CrB, CH Cyg, CI Cyg, V1016 Cyg, V1329 Cyg, AG Dra, YY Her, RS Oph, XX Oph, AG Peg, AX Per, CL Sco, HM Sge, AS 289, and M1-2. Integrated emission-line intensities are tabulated for comparison with ultraviolet and infrared data, as well as with previous optical studies. The reddening to each of the objects is derived by assuming that Balmer lines are emitted in their case B recombination ratios. However, the values so derived are often systematically higher than reddening estimates from the ultraviolet 2200 A feature. Comparisons with the available data from other wavelength ranges are noted.

  19. The development and consequences of an aggressive symbiotic fantasy.

    PubMed

    Awad, G A

    2000-01-01

    Chronic anxiety in a female patient was understood to have multiple meanings in relating to the mother through the fantasy of a symbiotic union. The origins of the fantasy are traced to the patient's poor relationship with a preoccupied and unavailable mother. The fantasy underwent several transformations under the influence of subsequent developmental phases and the special role of aggression in its elaboration. This paper illustrates the reciprocal interactions between separation-individuation and psychosexual development and their influence on the development of the self and gender identity, defenses against aggression, development of a sadomasochistic style, and transference-countertransference interactions. The symbiotic fantasy is seen as carrying the imprints of all developmental phases and as having multiple functions.

  20. Leguminous plants: inventors of root nodules to accommodate symbiotic bacteria.

    PubMed

    Suzaki, Takuya; Yoro, Emiko; Kawaguchi, Masayoshi

    2015-01-01

    Legumes and a few other plant species can establish a symbiotic relationship with nitrogen-fixing rhizobia, which enables them to survive in a nitrogen-deficient environment. During the course of nodulation, infection with rhizobia induces the dedifferentiation of host cells to form primordia of a symbiotic organ, the nodule, which prepares plants to accommodate rhizobia in host cells. While these nodulation processes are known to be genetically controlled by both plants and rhizobia, recent advances in studies on two model legumes, Lotus japonicus and Medicago truncatula, have provided great insight into the underlying plant-side molecular mechanism. In this chapter, we review such knowledge, with particular emphasis on two key processes of nodulation, nodule development and rhizobial invasion. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Physiological limitations and the genetic improvement of symbiotic nitrogen fixation

    SciTech Connect

    Gara, F.O.; Manian, S. ); Drevon, J.J. )

    1988-01-01

    The rhizobium legume symbiosis continues to be of strategic importance particularly in the context of food production. As the world population grows, it is necessary that new developments take place in crop improvement. The development and application of new technologies in biological sciences over past years has made the entire area of plant-microbial interaction an exciting and challenging research area to be involved in. In view of the importance of symbiotic nitrogen fixation, it is not surprising that it still represents one of the priority areas for commercial development in agricultural biotechnology. Since this symbiosis involves an association between procaryotic and eucaryhotic partners, it requires of necessity a coordinated and interdisciplinary approach. This book focuses on physiological limitations affecting symbiotic nitrogen fixation and the potential for overcoming such limitations by using genetic technologies.

  2. A survey of the Local Group of galaxies for symbiotic binary stars - I. First detection of symbiotic stars in M33

    NASA Astrophysics Data System (ADS)

    Mikołajewska, Joanna; Shara, Michael M.; Caldwell, Nelson; Iłkiewicz, Krystian; Zurek, David

    2017-02-01

    We present and discuss initial selection criteria and first results in M33 from a systematic search for extragalactic symbiotic stars. We show that the presence of diffuse ionized gas (DIG) emission can significantly contaminate the spectra of symbiotic star candidates. This important effect forces upon us a more stringent working definition of an extragalactic symbiotic star. We report the first detections and spectroscopic characterization of 12 symbiotic binaries in M33. We found that four of our systems contain carbon-rich giants. In another two of them, the giant seems to be a Zr-enhanced MS star, while the remaining six objects host M-type giants. The high number ratio of C to M giants in these binaries is consistent with the low metallicity of M33. The spatial and radial velocity distributions of these new symbiotic binaries are consistent with a wide range of progenitor star ages.

  3. Outburst Activity of the Symbiotic System AG Dra

    NASA Astrophysics Data System (ADS)

    Gális, R.; Hric, L.; Leedjärv, L.; Kundra, E.

    2015-07-01

    AG Dra is one of the best studied symbiotic systems. A period analysis of new and historical photometric data, as well as radial velocities, confirmed the presence of the two periods — about 550 days, caused by orbital motion, and around 350 days, related to pulsations of the cool component of AG Dra. In addition, the active stages change distinctively, but the outbursts recur with periods from 359 to 375 days.

  4. Sequence evidence for the symbiotic origins of chloroplasts and mitochondria

    NASA Technical Reports Server (NTRS)

    George, D. G.; Hunt, L. T.; Dayhoff, M. O.

    1983-01-01

    The origin of mitochondria and chloroplasts is investigated on the basis of prokaryotic and early-eukaryotic evolutionary trees derived from protein and nucleic-acid sequences by the method of Dayhoff (1979). Trees for bacterial ferrodoxins, 5S ribosomal RNA, c-type cytochromes, the lipid-binding subunit of ATPase, and dihydrofolate reductase are presented and discussed. Good agreement among the trees is found, and it is argued that the mitochondria and chloroplasts evolved by multiple symbiotic events.

  5. Sequence evidence for the symbiotic origins of chloroplasts and mitochondria

    NASA Technical Reports Server (NTRS)

    George, D. G.; Hunt, L. T.; Dayhoff, M. O.

    1983-01-01

    The origin of mitochondria and chloroplasts is investigated on the basis of prokaryotic and early-eukaryotic evolutionary trees derived from protein and nucleic-acid sequences by the method of Dayhoff (1979). Trees for bacterial ferrodoxins, 5S ribosomal RNA, c-type cytochromes, the lipid-binding subunit of ATPase, and dihydrofolate reductase are presented and discussed. Good agreement among the trees is found, and it is argued that the mitochondria and chloroplasts evolved by multiple symbiotic events.

  6. 1988 workshop on human-machine symbiotic systems

    SciTech Connect

    Parker, L.E.; Weisbin, C.R.

    1988-01-01

    This report presents the proceedings of the 1988 Workshop on Human-Machine Symbiotic Systems. Held December 5-6, 1988 in Oak Ridge, Tennessee, the workshop served as a forum for the discussion of several critical issues in human-machine symbiosis: human-machine communication, autonomous task planning and execution monitoring for heterogeneous agents, dynamic task allocation, human-machine system architecture, and machine learning via experience and human observation.

  7. Heterologous expression and characterization of a glycoside hydrolase family 45 endo-β-1,4-glucanase from a symbiotic protist of the lower termite, Reticulitermes speratus.

    PubMed

    Otagiri, Masato; Lopez, Crisanto M; Kitamoto, Katsuhiko; Arioka, Manabu; Kudo, Toshiaki; Moriya, Shigeharu

    2013-03-01

    The termite symbiotic system is one of the efficient lignocellulose degradation systems. We tried to express and characterize a novel cellulolytic enzyme from this system. Here, we report the isolation of an endo-β-1,4-glucanase gene homolog of glycoside hydrolase family 45 from a symbiotic protistan community of Reticulitermes speratus. Heterologous expression of this gene was performed using the expression system of Aspergillus oryzae. Analysis of enzymatic properties revealed 786 μmol/min/mg protein in specific activity, a V max of 833.0 units/mg protein, and a K m value of 2.58 mg/ml with carboxymethyl cellulose as the substrate. Thin-layer chromatography analysis showed that RsSymEG2 produces cellobiose from cellodextrins larger than cellohexaose. This enzyme showed high specific activity like other endo-β-1,4-glucanases from the symbiotic system of termites. It means that the termite symbiotic system is a good resource for highly active endo-β-1,4-glucanases.

  8. The Symbiotic System SS73 17 seen with Suzaku

    NASA Technical Reports Server (NTRS)

    Smith, Randall K.; Mushotzky, Richard; Kallman, Tim; Tueller, Jack; Mukai, Koji; Markwardt, Craig

    2007-01-01

    We observed with Suzaku the symbiotic star SS73 17, motivated by the discovery by the INTEGRAL satellite and the Swift BAT survey that it emits hard X-rays. Our observations showed a highly-absorbed X-ray spectrum with NH > loz3 emp2, equivalent to Av > 26, although the source has B magnitude 11.3 and is also bright in UV. The source also shows strong, narrow iron lines including fluorescent Fe K as well as Fe xxv and Fe XXVI. The X-ray spectrum can be fit with a thermal model including an absorption component that partially covers the source. Most of the equivalent width of the iron fluorescent line in this model can be explained as a combination of reprocessing in a dense absorber plus reflection off a white dwarf surface, but it is likely that the continuum is partially seen in reflection as well. Unlike other symbiotic systems that show hard X-ray emission (CH Cyg, RT Cru, T CrB, GX1+4), SS73 17 is not known to have shown nova-like optical variability, X-ray flashes, or pulsations, and has always shown faint soft X-ray emission. As a result, although it is likely a white dwarf, the nature of the compact object in SS73 17 is still uncertain. SS73 17 is probably an extreme example of the recently discovered and relatively small class of hard X-ray emitting symbiotic systems.

  9. Symbiotic regulation of plant growth, development and reproduction

    USGS Publications Warehouse

    Rodriguez, R.J.; Freeman, D. Carl; McArthur, E.D.; Kim, Y.-O.; Redman, R.S.

    2009-01-01

    The growth and development of rice (Oryzae sativa) seedlings was shown to be regulated epigenetically by a fungal endophyte. In contrast to un-inoculated (nonsymbiotic) plants, endophyte colonized (symbiotic) plants preferentially allocated resources into root growth until root hairs were well established. During that time symbiotic roots expanded at five times the rate observed in nonsymbiotic plants. Endophytes also influenced sexual reproduction of mature big sagebrush (Artemisia tridentata) plants. Two spatially distinct big sagebrush subspecies and their hybrids were symbiotic with unique fungal endophytes, despite being separated by only 380 m distance and 60 m elevation. A double reciprocal transplant experiment of parental and hybrid plants, and soils across the hybrid zone showed that fungal endophytes interact with the soils and different plant genotypes to confer enhanced plant reproduction in soil native to the endophyte and reduced reproduction in soil alien to the endophyte. Moreover, the most prevalent endophyte of the hybrid zone reduced the fitness of both parental subspecies. Because these endophytes are passed to the next generation of plants on seed coats, this interaction provides a selective advantage, habitat specificity, and the means of restricting gene flow, thereby making the hybrid zone stable, narrow and potentially leading to speciation. ?? 2009 Landes Bioscience.

  10. [A psychotic symbiotic child. Clinical and psychopathological study].

    PubMed

    Ledoux, M H

    1993-01-01

    Through the case study of a psychotic girl, we have tried to outline the psychotic mechanisms involved in this mental functioning. Anxieties of an autistic type have been found, as well as anxieties of a more psychotic type (i.e. symbiotic and schizophrenic). Characteristics of this psychotic functioning were: omnipotence, primitive identification mechanisms, fragmenting separation anxiety, search for sameness and for a low of identical repetition, difficulties in accessing to symbolism. Difficulties in defusion from the symbiotic object and the potential role played by this object in the difficulties are noteworthy. But it is not possible to conceptualize them in terms of direct causal relationship, because the object has also a counterphobic function and compensates for the void of subject as well as for the dissolution of the self. Also present is a schizoparanoïd aspect, with a temptation to cuddle inside the object. The sudden breaking through of informations or requirements from reality provokes surprise, panic reactions and retirement from the objectal world. Otherness triggers psychic pain and vacillation of symbiotic bounds. Thus the avoidance of, and retirement from, reality and the recourse to delusional thinking, especially when attempts to controlling with a rigid system are failing and deceiving. Threats of intrusion and loss of control are experienced as a threat of fragmentation and dissolution of the psyche. Far less threatening to the subject's internal balance is the policy of rigidly maintaining sameness and cuddling inside the object.

  11. Discovery of collimated ejection from the symbiotic binary BF Cygni

    NASA Astrophysics Data System (ADS)

    Skopal, A.; Tomov, N. A.; Tomova, M. T.

    2013-03-01

    Context. Detection of collimated ejection from white dwarfs (WD) in symbiotic binaries is very rare and has employed a variety of methods in X-ray, radio, optical imagery, and spectroscopy. To date, its signature in the optical spectra has only been recorded for four objects (MWC 560, Hen 3-1341, StHα 190, and Z And). Aims: We present the first observational evidence of highly-collimated bipolar ejection from the symbiotic binary BF Cyg, which developed during its current (2006-12) active phase, and determine their physical parameters. Methods: We monitored the outburst with the optical high-resolution spectroscopy and multicolour UBVRCIC photometry. Results: During 2009, three years after the 2006-eruption of BF Cyg, satellite components to Hα and Hβ lines emerged in the spectrum. During 2012, they became stable and were located symmetrically with respect to the main emission core of the line. Spectral properties of these components suggest bipolar ejection collimated within an opening angle of ≲15°, whose radiation is produced by an optically thin medium with the emission measure of 1-2 × 1059 (d/3.8 kpc)2 cm-3. Conclusions: Formation of the collimated ejection a few years after the eruption and its evolution on a time scale of years at a constant optical brightness can aid us in better understanding the accretion process during the active phases of symbiotic stars. Based on data collected with 2-m telescope at the Rozhen National Astronomical Observatory and the David Dunlap Observatory.

  12. Symbiotic commensal bacteria direct maturation of the host immune system.

    PubMed

    Edelman, Sanna M; Kasper, Dennis L

    2008-11-01

    Although commensal bacteria are known to play an important role in the proper maturation of the immune system of their mammalian hosts, the molecular mechanisms underlying this immunomodulation are poorly characterized. The present review summarizes recent findings in the field and describes new knowledge on the interplay of the innate and adaptive arms of the immune response induced by symbiotic bacterial carbohydrate antigens. Commensal bacteria in the intestine not only interact directly with dendritic cells but also engage in cross-talk with epithelial cells. These interactions lead to the induction of tolerogenic antigen-presenting cells in the lamina propria and ultimately to the regulation of functional maturation of effector T cells. Upon recognition of capsular polysaccharide antigens of commensal bacteria by dendritic cells (through toll-like receptor 2), innate immune responses facilitate and act in conjunction with adaptive responses to promote optimal Th1 polarization. In contrast, adaptive immunoglobulin A responses to symbiotic bacteria regulate the magnitude of oxidative innate immune responses in the mucosa as well as bacterial epitope expression in the lumen. Accumulating evidence is elucidating surface carbohydrate structures of symbiotic bacteria that drive the modulation of the intestinal immune system, resulting in mature, balanced immune responses and oral tolerance.

  13. A rhizobium leguminosarum mutant defective in symbiotic iron acquisition

    SciTech Connect

    Nadler, K.D.; Chen, Jing-Wen; John, T.R. ); Johnston, A.W.B. )

    1990-02-01

    Iron acquisition by symbiotic Rhizobium spp. is essential for nitrogen fixation in the legume root nodule symbiosis. Rhizobium leguminosarum 116, an ineffective mutant strain with a defect in iron acquisition, was isolated after nitrosoguanidine mutagenesis of the effective strain 1062. The pop-1 mutation in strain 116 imparted to it a complex phenotype, characteristic of iron deficiency. Several iron(III)-solubilizing agents, such as citrate, hydroxyquinoline, and dihydroxybenzoate, stimulated growth of 116 on low-iron solid medium; anthranilic acid, the R. leguminosarum siderophore, inhibited low-iron growth of 116. The initial rate of {sup 55}Fe uptake by suspensions of iron-starved 116 cells was 10-fold less than that of iron-starved wild-type cells. Electron microscopic observations revealed no morphological abnormalities in the small, white nodules induced by 116. Nodule cortical cells were filled with vesicles containing apparently normal bacteroids. No premature degeneration of bacteroids or of plant cell organelles was evident. The authors mapped pop-1 by R plasmid-mediated conjugation and recombination to the ade-27-rib-2 region of the R. leguminosarum chromosome. No segregation of pop-1 and the symbiotic defect was observed among the recombinants from these crosses. Cosmid pKN1, a pLAFR1 derivative containing a 24-kilobase-pair fragment of R. leguminosarum DNA, conferred on 116 the ability to grow on dipyridyl medium and to fix nitrogen symbiotically.

  14. Cellulolytic activity and structure of symbiotic bacteria in locust guts.

    PubMed

    Su, L-J; Liu, H; Li, Y; Zhang, H-F; Chen, M; Gao, X-H; Wang, F-Q; Song, A-D

    2014-09-29

    Locusts are able to digest the cellulose of Gramineae plants, resulting in their being considered as major crop pests. To illustrate the mechanism involved in cellulose digestion, the cellulolytic activity and zymography in the gut contents of 16 locust species were determined using carboxymethyl cellulose (CMC) as substrate. The diversity of gut symbiotic bacteria was studied using denaturing gradient gel electrophoresis (DGGE). The results showed that high CMC activity was present in Acrididae gut fluid (mean 356.4 U/g proteins). Of the 5 locust species, Oxya chinensis had the highest diversity of intestinal symbiotic bacteria, characterized by the DGGE profile containing more than 20 bands of 16S rRNA. Klebsiella pneumoniae, in the gut of Locusta migratoria manilensis, was identified as the most abundant symbiotic bacterium by DNA sequencing, with a relative abundance of 19.74%. In comparison, Methylobacterium sp was the most dominant species in the Atractomorpha sinensis gut, with a relative abundance of 29.04%. The results indicated that the cellulolytic enzymes and gut microbial communities probably reflected their phylogenetic relationship with different locust species and associated feeding strategies.

  15. Chemical Abundance Analysis of the Symbiotic Red Giants

    NASA Astrophysics Data System (ADS)

    Galan, Cezary; Mikolajewska, Joanna; Hinkle, Kenneth H.

    2015-01-01

    The study of symbiotic stars - the long period, interacting binary systems - composed of red giant donor and a hot, compact companion is important for our understanding of binary stellar evolution in systems where mass loss or transfer take place involving RGB/AGB stars. The elemental abundances of symbiotic giants can track the mass exchange history and can determine their parent stellar population. However, the number of these objects with fairly well determined photospheric composition is insufficient for statistical considerations. Here we present the detailed chemical abundance analysis obtained for the first time for 14 M-type symbiotic giants. The analysis is based on the high resolution (R ˜ 50000), high S/N ˜ 100, near-IR spectra (at H- and K-band regions) obtained with Phoenix/Gemini South spectrometer. Spectrum synthesis employing standard LTE analysis and atmosphere models was used to obtain photospheric abundances of CNO and elements around the iron peak (Sc, Ti, Fe, and Ni). Our analysis reveals mostly slightly sub-solar or near-solar metallicities. We obtained significantly subsolar metallicities for RW Hya, RT Ser, and Hen 3-1213 and slightly super-solar metallicity in V455 Sco. The very low ^{12}C/^{13}C isotopic ratios, ˜6-11, and significant enrichment in nitrogen ^{14}N isotope in almost all giants in our sample indicate that they have experienced the first dredge-up.

  16. Do symbiotic microbes have a role in plant evolution, performance and response to stress?

    PubMed Central

    Lucero, Mary E; Reyes-Vera, Isaac; Havstad, Kris M

    2008-01-01

    Vascular plants have been considered as autonomous organisms especially when their performance has been interpreted at the genome and cellular level. In reality, vascular plants provide a unique ecological niche for diverse communities of cryptic symbiotic microbes which often contribute multiple benefits, such as enhanced photosynthetic efficiency, nutrient and water use and tolerance to abiotic and biotic stress. These benefits are similar to improvements sought by plant scientists working to develop ecologically sustainable crops for food, fiber and biofuels. Native desert plants include a community of indigenous endosymbiotic fungi that are structural components with cells, tissues, cell cultures and regenerated plants. These fungi regulate plant growth and development and contribute genes and natural products that enable plants to adapt to changing environments. A method developed for transferring these endophytes from cell cultures to non-host plants promises to be a revolutionary approach for the development of novel plant germplasm and has application in the field of plant biotechnology. PMID:19513202

  17. Regulation of fixLJ by Hfq Controls Symbiotically Important Genes in Sinorhizobium meliloti.

    PubMed

    Gao, Mengsheng; Nguyen, Hahn; Salas González, Isai; Teplitski, Max

    2016-11-01

    The RNA-binding chaperone Hfq plays critical roles in the establishment and functionality of the symbiosis between Sinorhizobium meliloti and its legume hosts. A mutation in hfq reduces symbiotic efficiency resulting in a Fix(-) phenotype, characterized by the inability of the bacterium to fix nitrogen. At least in part, this is due to the ability of Hfq to regulate the fixLJ operon, which encodes a sensor kinase-response regulator pair that controls expression of the nitrogenase genes. The ability of Hfq to bind fixLJ in vitro and in planta was demonstrated with gel shift and coimmunoprecipitation experiments. Two (ARN)2 motifs in the fixLJ message were the likely sites through which Hfq exerted its posttranscriptional control. Consistent with the regulatory effects of Hfq, downstream genes controlled by FixLJ (such as nifK, noeB) were also subject to Hfq regulation in planta.

  18. Symbiotic hollow fiber membrane photobioreactor for microalgal growth and bacterial wastewater treatment.

    PubMed

    Vu, Linh T K; Loh, Kai-Chee

    2016-11-01

    A hollow fiber membrane photobioreactor (HFMP) for microalgal growth and bacterial wastewater treatment was developed. C. vulgaris culture was circulated through one side of the HFMP and P. putida culture was circulated through the other. A symbiotic relationship was demonstrated as reflected by the photo-autotrophic growth of C. vulgaris using CO2 provided by P. putida and biodegradation of 500mg/L glucose by P. putida utilizing photosynthetic O2 produced by C. vulgaris. Performance of the HFMP was significantly enhanced when the microalgal culture was circulated through the lumen side of the HFMP: the average percentage of glucose degraded per 8-h cycle was as high as 98% and microalgal biomass productivity was increased by 69% compared to the reversed orientation. Enhanced glucose biodegradation was achieved in an HFMP packed with more fibers indicating the easy scalability of the HFMP for increased wastewater treatment efficiency.

  19. Exogenous suppression of the symbiotic deficiencies of Rhizobium meliloti exo mutants.

    PubMed Central

    Urzainqui, A; Walker, G C

    1992-01-01

    The acidic exopolysaccharide (EPS I) produced by Rhizobium meliloti during symbiosis with Medicago sativa has been shown to be required for the proper development of nitrogen-fixing nodules. Cloned DNA from the exo region of R. meliloti is shown to stimulate production of the low-molecular-weight form of this exopolysaccharide, and in this report we show that the symbiotic deficiencies of two exo mutants of R. meliloti, the exoA and exoH mutants, can be rescued by the addition of this low-molecular-weight material at the time of inoculation. For exoA and exoH mutants, rescue with a preparation containing low-molecular-weight exopolysaccharide induces the formation of nitrogen-fixing nodules which appear somewhat later and at a reduced efficiency compared with wild-type-induced nodules; however, microscopic analysis of these nodules reveals similar nodule morphology and the presence of large numbers of bacteroids in each. Images PMID:1577707

  20. Job planning and execution monitoring for a human-robot symbiotic system

    SciTech Connect

    Parker, L.E.

    1989-11-01

    The human-robot symbiosis concept has the fundamental objective of bridging the gap between fully human-controlled and fully autonomous systems to achieve true human-robot cooperative control and intelligence. Such a system would allow improved speed, accuracy, and efficiency of task execution, while retaining the human in the loop for innovative reasoning and decision-making. Earlier research has resulted in the development of a robotic system architecture facilitating the symbiotic integration of teleoperative and automated modes of task execution. This architecture reflects a unique blend of many disciplines of artificial intelligence into a working system, including job or mission planning, dynamic task allocation, human-robot communication, automated monitoring, and machine learning. This report focuses on two elements of this architecture: the Job Planner and the Automated Monitor. 17 refs., 7 figs.

  1. Simulating interactive effects of symbiotic nitrogen fixation, carbon dioxide elevation, and climatic change on legume growth.

    PubMed

    Yu, Mei; Gao, Q; Shaffer, M J

    2002-01-01

    The underlying mechanisms of interaction between the symbiotic nitrogen-fixation process and main physiological processes, such as assimilation, nutrient allocation, and structural growth, as well as effects of nitrogen fixation on plant responses to global change, are important and still open to more investigation. Appropriate models have not been adequately developed. A dynamic ecophysiological model was developed in this study for a legume plant [Glycine max (L.) Merr.] growing in northern China. The model synthesized symbiotic nitrogen fixation and the main physiological processes under variable atmospheric CO2 concentration and climatic conditions, and emphasized the interactive effects of these processes on seasonal biomass dynamics of the plant. Experimental measurements of ecophysiological quantities obtained in a CO2 enrichment experiment on soybean plants, were used to parameterize and validate the model. The results indicated that the model simulated the experiments with reasonable accuracy. The R2 values between simulations and observations are 0.94, 0.95, and 0.86 for total biomass, green biomass, and nodule biomass, respectively. The simulations for various combinations of atmospheric CO2 concentration, precipitation, and temperature, with or without nitrogen fixation, showed that increasing atmospheric CO2 concentration, precipitation, and efficiency of nitrogen fixation all have positive effects on biomass accumulation. On the other hand, an increased temperature induced lower rates of biomass accumulation under semi-arid conditions. In general, factors with positive effects on plant growth tended to promote each other in the simulation range, except the relationship between CO2 concentration and climatic factors. Because of the enhanced water use efficiency with a higher CO2 concentration, more significant effects of CO2 concentration were associated with a worse (dryer and warmer in this study) climate.

  2. Obtaining hemocytes from the Hawaiian bobtail squid Euprymna scolopes and observing their adherence to symbiotic and non-symbiotic bacteria.

    PubMed

    Collins, Andrew J; Nyholm, Spencer V

    2010-02-11

    Studies concerning the role of the immune system in mediating molecular signaling between beneficial bacteria and their hosts have, in recent years, made significant contributions to our understanding of the co-evolution of eukaryotes with their microbiota. The symbiotic association between the Hawaiian bobtail squid, Euprymna scolopes and the bioluminescent bacterium Vibrio fischeri has been utilized as a model system for understanding the effects of beneficial bacteria on animal development. Recent studies have shown that macrophage-like hemocytes, the sole cellular component of the squid host's innate immune system, likely play an important role in mediating the establishment and maintenance of this association. This protocol will demonstrate how to obtain hemocytes from E. scolopes and then use these cells in bacterial binding assays. Adult squid are first anesthetized before hemolymph is collected by syringe from the main cephalic blood vessel. The host hemocytes, contained in the extracted hemolymph, are adhered to chambered glass coverslips and then exposed to green fluorescent protein-labeled symbiotic Vibrio fischeri and non-symbiotic Vibrio harveyi. The hemocytes are counterstained with a fluorescent dye (Cell Tracker Orange, Invitrogen) and then visualized using fluorescent microscopy.

  3. Symbiotic adaptation of bacteria in the gut of Reticulitermes speratus: low endo-beta-1,4-glucanase activity.

    PubMed

    Cho, Moon-Jung; Kim, Yoon-Hee; Shin, Keum; Kim, Young-Kyoon; Kim, Yeong-Suk; Kim, Tae-Jong

    2010-05-07

    The termite is a good model of symbiosis between microbes and hosts and possesses an effective cellulose digestive system. Oxygen-tolerant bacteria, such as Dyella sp., Chryseobacterium sp., and Bacillus sp., were isolated from Reticulitermes speratus gut. Notably, the endo-beta-1,4-glucanase (EG) activity of all 16 strains of isolated bacteria was low. Due to the combined activity of EG from the termites and their symbiotic protozoa, the bacteria might not be compelled to express EG. This observation demonstrates how well intestinal bacteria have assimilated themselves into the efficient cellulose digestive systems of termites. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  4. Mechanism by Which Cold Shock Evokes Exocytosis of Symbiotic Algae in Marine Cnidarians

    DTIC Science & Technology

    1993-05-30

    cold shock evokes exocytosis of symbiotic algae in marine cnidarians . RPORTING PERIOD: 30 September 1989 - 30 May 1993 D TIC ELECTE AWARD PERIOD: 30... cnidarians (sea anemones and corals). 2. To identify host factor in symbiotic cnidarians . OBJECTIVE 1: Marine cnidarians were subjected ta cold shock, heat...and L. Muscatine (1992) Temperature stress causes host cell detachment in symbiotic cnidarians : Implications for coral bleaching. Biol. Bull. 182: 324

  5. Primers to block the amplification of symbiotic apostome ciliate 18S rRNA gene in a PCR-based copepod diet study

    NASA Astrophysics Data System (ADS)

    Yi, Xiaoyan; Zhang, Huan; Liu, Guangxing

    2014-05-01

    Pelagic copepods play an important role in the marine food web. However, a full understanding of the ecological status of this zooplankton group depends on the careful study of their natural diets. In previous PCR-based copepod diet studies, we found many apostome ciliates that live symbiotically under the exoskeleton of the copepods, and their sequences were often over-represented in the 18S rRNA gene (18S rDNA) libraries. As a first step to address this issue, we designed three apostome ciliate 18S rDNA blocking primers, and tested their blocking efficiency against apostome ciliate 18s rDNA under various PCR conditions. Using a semi-quantitative PCR method, we optimized the conditions to efficiently amplify the 18S rDNA of the prey while simultaneously excluding the symbiotic apostome ciliates. This technique will facilitate PCR-based diet studies of copepods and other zooplankton in their natural environments.

  6. Symbiotic Control in Mechanical Bond Formation.

    PubMed

    Wang, Yuping; Sun, Junling; Liu, Zhichang; Nassar, Majed S; Botros, Youssry Y; Stoddart, J Fraser

    2016-09-26

    Since the advent of mechanically interlocked molecules (MIMs), many approaches to templating their formation using various different noncovalent bonding interactions have been introduced and explored. In particular, employing radical-pairing interactions between BIPY(.+) units, the radical cationic state of 4,4'-bipyridinium (BIPY(2+) ) units, in syntheses is not only a convenient but also an attractive source of templation because of the unique properties residing in the resulting catenanes and rotaxanes. Herein, we report a copper-mediated procedure that enables the generation, in the MIM-precursors, of BIPY(.+) radical cations, while the metal itself, which is oxidized to Cu(I) , catalyzes the azide-alkyne cycloaddition reactions that result in the efficient syntheses of two catenanes and one rotaxane, assisted by radical-pairing interactions between the BIPY(.+) radical cations. This procedure not only provides a fillip for making and investigating the properties of Coulombically challenged catenanes and rotaxanes, but it also opens up the possibility of synthesizing artificial molecular machines which operate away from equilibrium.

  7. Symbiotic Performance of Diverse Frankia Strains on Salt-Stressed Casuarina glauca and Casuarina equisetifolia Plants

    PubMed Central

    Ngom, Mariama; Gray, Krystelle; Diagne, Nathalie; Oshone, Rediet; Fardoux, Joel; Gherbi, Hassen; Hocher, Valérie; Svistoonoff, Sergio; Laplaze, Laurent; Tisa, Louis S.; Sy, Mame O.; Champion, Antony

    2016-01-01

    Symbiotic nitrogen-fixing associations between Casuarina trees and the actinobacteria Frankia are widely used in agroforestry in particular for salinized land reclamation. The aim of this study was to analyze the effects of salinity on the establishment of the actinorhizal symbiosis between C. glauca and two contrasting Frankia strains (salt sensitive; CcI3 vs. salt tolerant; CeD) and the role of these isolates in the salt tolerance of C. glauca and C. equisetifolia plants. We show that the number of root nodules decreased with increasing salinity levels in both plants inoculated with CcI3 and CeD. Nodule formation did not occur in seedlings inoculated with CcI3 and CeD, at NaCl concentrations above 100 and 200 mM, respectively. Salinity also affected the early deformation of plant root hairs and reduced their number and size. In addition, expression of symbiotic marker Cg12 gene, which codes for a subtilase, was reduced at 50 mM NaCl. These data suggest that the reduction of nodulation in C. glauca under salt stress is in part due to inhibition of early mechanisms of infection. We also show that prior inoculation of C. glauca and C. equisetifolia with Frankia strains CcI3 and CeD significantly improved plant height, dry biomass, chlorophyll and proline contents at all levels of salinity tested, depending on the Casuarina-Frankia association. There was no correlation between in vitro salt tolerance of Frankia strains and efficiency in planta under salt-stressed conditions. Our results strongly indicate that increased N nutrition, photosynthesis potential and proline accumulation are important factors responsible for salt tolerance of nodulated C. glauca and C. equisetifolia. PMID:27630656

  8. A LuxR Homolog Controls Production of Symbiotically Active Extracellular Polysaccharide II by Sinorhizobium meliloti

    PubMed Central

    Pellock, Brett J.; Teplitski, Max; Boinay, Ryan P.; Bauer, W. Dietz; Walker, Graham C.

    2002-01-01

    Production of complex extracellular polysaccharides (EPSs) by the nitrogen-fixing soil bacterium Sinorhizobium meliloti is required for efficient invasion of root nodules on the host plant alfalfa. Any one of three S. meliloti polysaccharides, succinoglycan, EPS II, or K antigen, can mediate infection thread initiation and extension (root nodule invasion) on alfalfa. Of these three polysaccharides, the only symbiotically active polysaccharide produced by S. meliloti wild-type strain Rm1021 is succinoglycan. The expR101 mutation is required to turn on production of symbiotically active forms of EPS II in strain Rm1021. In this study, we have determined the nature of the expR101 mutation in S. meliloti. The expR101 mutation, a spontaneous dominant mutation, results from precise, reading frame-restoring excision of an insertion sequence from the coding region of expR, a gene whose predicted protein product is highly homologous to the Rhizobium leguminosarum bv. viciae RhiR protein and a number of other homologs of Vibrio fischeri LuxR that function as receptors for N-acylhomoserine lactones (AHLs) in quorum-sensing regulation of gene expression. S. meliloti ExpR activates transcription of genes involved in EPS II production in a density-dependent fashion, and it does so at much lower cell densities than many quorum-sensing systems. High-pressure liquid chromatographic fractionation of S. meliloti culture filtrate extracts revealed at least three peaks with AHL activity, one of which activated ExpR-dependent expression of the expE operon. PMID:12193623

  9. Symbiotic diversity of Ensifer meliloti strains recovered from various legume species in Tunisia.

    PubMed

    Mnasri, Bacem; Badri, Yazid; Saïdi, Sabrine; de Lajudie, Philippe; Mhamdi, Ridha

    2009-12-01

    Ensifer meliloti (formerly Sinorhizobium meliloti) was first considered as a specific microsymbiont of Medicago, Melilotus and Trigonella. However, strains of E. meliloti were recovered from root nodules of various legume species and their symbiotic status still remains unclear. Here, we further investigate the specificity of these strains. A collection of 47 E. meliloti strains isolated in Tunisia from root nodules of Medicago truncatula, Medicago sativa, Medicago ciliaris, Medicago laciniata, Medicago marina, Medicago scutellata, Phaseolus vulgaris, Cicer arietinum, Argyrolobium uniflorum, Lotus creticus, Lotus roudairei, Ononis natrix, Retama raetam, Genista saharae, Acacia tortilis, Hedysarum carnosum and Hippocrepis bicontorta were examined by REP-PCR fingerprinting, PCR-RFLPs of the 16S-23S rDNA IGS, the nifH gene and nifD-K intergenic spacer, and sequencing of 16S rRNA and nodA genes. Their nodulation range was also assessed by cross-inoculation experiments. No clear correlation was found between chromosomal backgrounds and host plants of origin. The nodulation polyvalence of the species E. meliloti was associated with a high symbiotic heterogeneity. On the basis of PCR-RFLP data from the nifH gene and nifD-K intergenic spacer, E. meliloti strains isolated from non-Medicago legumes harboured distinct genes and possessed wider host ranges. Some strains did not nodulate Medicago species. On the basis of nodA phylogeny, the majority of the Tunisian strains, including strains from Medicago, harboured distinct nodA alleles more related to those found in E. medicae than those found in E. meliloti. However, more work is still needed to characterize this group further. The diversity observed among M. laciniata isolates, which was supported by nodA phylogeny, nifH typing and the efficiency profile on M. ciliaris, indicated that what was thought to be bv. medicaginis is certainly heterogeneous.

  10. Comparative metagenomic analysis of microcosm structures and lignocellulolytic enzyme systems of symbiotic biomass-degrading consortia.

    PubMed

    Wongwilaiwalin, Sarunyou; Laothanachareon, Thanaporn; Mhuantong, Wuttichai; Tangphatsornruang, Sithichoke; Eurwilaichitr, Lily; Igarashi, Yasuo; Champreda, Verawat

    2013-10-01

    Decomposition of lignocelluloses by cooperative microbial actions is an essential process of carbon cycling in nature and provides a basis for biomass conversion to fuels and chemicals in biorefineries. In this study, structurally stable symbiotic aero-tolerant lignocellulose-degrading microbial consortia were obtained from biodiversified microflora present in industrial sugarcane bagasse pile (BGC-1), cow rumen fluid (CRC-1), and pulp mill activated sludge (ASC-1) by successive subcultivation on rice straw under facultative anoxic conditions. Tagged 16S rRNA gene pyrosequencing revealed that all isolated consortia originated from highly diverse environmental microflora shared similar composite phylum profiles comprising mainly Firmicutes, reflecting convergent adaptation of microcosm structures, however, with substantial differences at refined genus level. BGC-1 comprising cellulolytic Clostridium and Acetanaerobacterium in stable coexistence with ligninolytic Ureibacillus showed the highest capability on degradation of agricultural residues and industrial pulp waste with CMCase, xylanase, and β-glucanase activities in the supernatant. Shotgun pyrosequencing of the BGC-1 metagenome indicated a markedly high relative abundance of genes encoding for glycosyl hydrolases, particularly for lignocellulytic enzymes in 26 families. The enzyme system comprised a unique composition of main-chain degrading and side-chain processing hydrolases, dominated by GH2, 3, 5, 9, 10, and 43, reflecting adaptation of enzyme profiles to the specific substrate. Gene mapping showed metabolic potential of BGC-1 for conversion of biomass sugars to various fermentation products of industrial importance. The symbiotic consortium is a promising simplified model for study of multispecies mechanisms on consolidated bioprocessing and a platform for discovering efficient synergistic enzyme systems for biotechnological application.

  11. Transcriptome analyses to investigate symbiotic relationships between marine protists

    PubMed Central

    Balzano, Sergio; Corre, Erwan; Decelle, Johan; Sierra, Roberto; Wincker, Patrick; Da Silva, Corinne; Poulain, Julie; Pawlowski, Jan; Not, Fabrice

    2015-01-01

    Rhizaria are an important component of oceanic plankton communities worldwide. A number of species harbor eukaryotic microalgal symbionts, which are horizontally acquired in the environment at each generation. Although these photosymbioses are determinant for Rhizaria ability to thrive in oceanic ecosystems, the mechanisms for symbiotic interactions are unclear. Using high-throughput sequencing technology (i.e., 454), we generated large Expressed Sequence Tag (EST) datasets from four uncultured Rhizaria, an acantharian (Amphilonche elongata), two polycystines (Collozoum sp. and Spongosphaera streptacantha), and one phaeodarian (Aulacantha scolymantha). We assessed the main genetic features of the host/symbionts consortium (i.e., the holobiont) transcriptomes and found rRNA sequences affiliated to a wide range of bacteria and protists in all samples, suggesting that diverse microbial communities are associated with the holobionts. A particular focus was then carried out to search for genes potentially involved in symbiotic processes such as the presence of c-type lectins-coding genes, which are proteins that play a role in cell recognition among eukaryotes. Unigenes coding putative c-type lectin domains (CTLD) were found in the species bearing photosynthetic symbionts (A. elongata, Collozoum sp., and S. streptacantha) but not in the non-symbiotic one (A. scolymantha). More particularly, phylogenetic analyses group CTLDs from A. elongata and Collozoum sp. on a distinct branch from S. streptacantha CTLDs, which contained carbohydrate-binding motifs typically observed in other marine photosymbiosis. Our data suggest that similarly to other well-known marine photosymbiosis involving metazoans, the interactions of glycans with c-type lectins is likely involved in modulation of the host/symbiont specific recognition in Radiolaria. PMID:25852650

  12. BD-21 3873: another yellow-symbiotic barium star.

    NASA Astrophysics Data System (ADS)

    Smith, V. V.; Cunha, K.; Jorissen, A.; Boffin, H. M. J.

    1997-08-01

    An abundance analysis of the yellow symbiotic system BD-21 3873 reveals it to be a metal-poor K-giant ([Fe/H]=-1.3) which is enriched in the heavy s-process elements. In that respect, this star appears to be a twin of AG Dra, another yellow symbiotic system analyzed in a previous paper (Smith et al., 1996A&A...315..179S). The heavy-element abundance distributions of AG Dra and BD-21 3873 are almost identical, and are best reproduced by a s-process with a neutron exposure parameter of 1.2-1.3mb^-1^ and a neutron density logN_n_=8.3 (as derived from the Rb/Zr ratio). These two systems thus link the symbiotic stars to the binary barium and CH stars which are also s-process enriched. These binary systems, which exhibit overabundances of the heavy elements, owe their abundance peculiarities to mass transfer from thermally-pulsing asymptotic giant branch stars, which have since evolved to become white-dwarf companions of the cool stars we now view as the chemically-peculiar primaries. The spectroscopic orbits of BD-21 3873 (derived from CORAVEL measurements) and AG Dra are similar to those of barium and CH stars. With an orbital period of 281.6d, BD-21 3873 is one of the closest systems in these families, and its light curve indeed suggests that variations due to reflection and ellipticity effects are present. The amplitude of the ellipsoidal variations indicates that the giant must be close to filling its Roche lobe. However, no acceptable solution simultaneously satisfies the constraints from the light curve, the orbital elements and the evolutionary tracks in the framework of the standard Roche lobe geometry. We suggest that this discrepancy may be resolved by taking into account the deformation of the Roche lobe caused by the force driving the large mass loss of the giant.

  13. Low resolution ultraviolet and optical spectrophotometry of symbiotic stars

    NASA Technical Reports Server (NTRS)

    Slovak, M. H.

    1982-01-01

    Low resolution International Ultraviolet Explorer spectra combined with optical spectrophotometry provide absolute flux distributions for seven symbiotic variables from 1200 to 6450 A. For five stars (EG And, BF Cyg, CI Cyg, AG Peg, and Z And) the data are representative of the quiescent/out-of-eclipse energy distributions; for CH Cyg and AX Per, the observations were obtained following their atest outburst in 1977 and 1978, respectively. The de-reddened distributions reveal a remarkable diversity of both line spectra and continua. While the optical and near infrared regions lambda = 5500 A) are well represented by single component stellar models, multicomponent flux distributions are required to reproduce the ultraviolet continua.

  14. Trading molecules and tracking targets in symbiotic interactions

    PubMed Central

    Schmidt, Eric W.

    2009-01-01

    It is probable that nearly every natural product structure results from interactions between organisms. Symbiosis, a subset of inter-organism interactions involving closely associated partners, has recently provided new and interesting experimental systems for the study of these interactions. This review discusses new observations about natural product function and structural evolution that emerge from the study of symbiotic systems. In particular, these advances directly address long-standing “how” and “why” questions about natural products, providing fundamental insights about the evolution, origin, and purpose of natural products that are inaccessible by other methods. PMID:18641627

  15. IRAS low resolution spectra of 26 symbiotic stars

    NASA Technical Reports Server (NTRS)

    Stencel, Robert E.; Brugel, Edward W.; Goodwill, Michael E.

    1990-01-01

    Data related to the spectral scans for 26 symbiotic stars are described which were extracted from the IRAS low resolution database. Data from the 8-15- and 15-23-micron bands are merged in a program that scales the longer wavelength and produces a weighted average of the spectral scans for each source. The survey shows that active dust producers can probably be isolated and some theories related to the presence of dust emission features are discussed in terms of source variability for measurements made with low resolution spectra.

  16. A Rhizobium leguminosarum mutant defective in symbiotic iron acquisition.

    PubMed Central

    Nadler, K D; Johnston, A W; Chen, J W; John, T R

    1990-01-01

    Iron acquisition by symbiotic Rhizobium spp. is essential for nitrogen fixation in the legume root nodule symbiosis. Rhizobium leguminosarum 116, an ineffective mutant strain with a defect in iron acquisition, was isolated after nitrosoguanidine mutagenesis of the effective strain 1062. The pop-1 mutation in strain 116 imparted to it a complex phenotype, characteristic of iron deficiency: the accumulation of porphyrins (precursors of hemes) so that colonies emitted a characteristic pinkish-red fluorescence when excited by UV light, reduced levels of cytochromes b and c, and wild-type growth on high-iron media but low or no growth in low-iron broth and on solid media supplemented with the iron scavenger dipyridyl. Several iron(III)-solubilizing agents, such as citrate, hydroxyquinoline, and dihydroxybenzoate, stimulated growth of 116 on low-iron solid medium; anthranilic acid, the R. leguminosarum siderophore, inhibited low-iron growth of 116. The initial rate of 55Fe uptake by suspensions of iron-starved 116 cells was 10-fold less than that of iron-starved wild-type cells. Electron microscopic observations revealed no morphological abnormalities in the small, white nodules induced by 116. Nodule cortical cells were filled with vesicles containing apparently normal bacteroids. No premature degeneration of bacteroids or of plant cell organelles was evident. We mapped pop-1 by R plasmid-mediated conjugation and recombination to the ade-27-rib-2 region of the R. leguminosarum chromosome. No segregation of pop-1 and the symbiotic defect was observed among the recombinants from these crosses. Cosmid pKN1, a pLAFR1 derivative containing a 24-kilobase-pair fragment of R. leguminosarum DNA, conferred on 116 the ability to grow on dipyridyl medium and to fix nitrogen symbiotically. These results indicate that the insert cloned in pKN1 encodes an element of the iron acquisition system of R. leguminosarum that is essential for symbiotic nitrogen fixation. Images FIG. 3A-3B FIG

  17. COMPARING SYMBIOTIC NEBULAE AND PLANETARY NEBULAE LUMINOSITY FUNCTIONS

    SciTech Connect

    Frankowski, Adam; Soker, Noam E-mail: soker@physics.technion.ac.i

    2009-10-01

    We compare the observed symbiotic nebulae (SyN) luminosity function (SyNLF) in the [O III] lambda5007 A line to the planetary nebulae (PN) luminosity function (PNLF) and find that the intrinsic SyNLF (ISyNLF) of galactic SyNs has-within its uncertainty of 0.5-0.8 mag-very similar cutoff luminosity and general shape to those of the PNLF. The [O III]/(Halpha+[N II]) line ratios of SyNs and PNs are shown to be also related. Possible implications of these results for the universality of the PNLF are briefly outlined.

  18. Gene Expression in Gut Symbiotic Organ of Stinkbug Affected by Extracellular Bacterial Symbiont

    PubMed Central

    Futahashi, Ryo; Tanaka, Kohjiro; Tanahashi, Masahiko; Nikoh, Naruo; Kikuchi, Yoshitomo; Lee, Bok Luel; Fukatsu, Takema

    2013-01-01

    The bean bug Riptortus pedestris possesses a specialized symbiotic organ in a posterior region of the midgut, where numerous crypts harbor extracellular betaproteobacterial symbionts of the genus Burkholderia. Second instar nymphs orally acquire the symbiont from the environment, and the symbiont infection benefits the host by facilitating growth and by occasionally conferring insecticide resistance. Here we performed comparative transcriptomic analyses of insect genes expressed in symbiotic and non-symbiotic regions of the midgut dissected from Burkholderia-infected and uninfected R. pedestris. Expression sequence tag analysis of cDNA libraries and quantitative reverse transcription PCR identified a number of insect genes expressed in symbiosis- or aposymbiosis-associated patterns. For example, genes up-regulated in symbiotic relative to aposymbiotic individuals, including many cysteine-rich secreted protein genes and many cathepsin protease genes, are likely to play a role in regulating the symbiosis. Conversely, genes up-regulated in aposymbiotic relative to symbiotic individuals, including a chicken-type lysozyme gene and a defensin-like protein gene, are possibly involved in regulation of non-symbiotic bacterial infections. Our study presents the first transcriptomic data on gut symbiotic organ of a stinkbug, which provides initial clues to understanding of molecular mechanisms underlying the insect-bacterium gut symbiosis and sheds light on several intriguing commonalities between endocellular and extracellular symbiotic associations. PMID:23691247

  19. New burst of the active symbiotic star BF Cyg at the beginning of 2017.

    NASA Astrophysics Data System (ADS)

    Skopal, A.; Sekeras, M.; Shugarov, S.; Shagatova, N.

    2017-02-01

    BF Cyg is an eclipsing symbiotic binary with the orbital period of 757 d. Historical light curve of BF Cyg shows a slow symbiotic-nova-like outburst (1895-1960) with superposed eruptions of the Z And type and bursts on the time scale of, or less than, one year (e.g.

  20. Effects of removing symbiotic green algae on the response of Hydra viridissima (Pallas 1776) to metals.

    PubMed

    Karntanut, W; Pascoe, D

    2005-03-01

    Hydra viridissima is distinctively green due to symbiotic algae within the endodermal cells. The current investigation was designed to see if these algae influenced the response of Hydra to pollutants, by comparing the toxicity of copper, cadmium, and zinc to both symbiotic and aposymbiotic (free of their endosymbiotic algae) H. viridissima. The results demonstrated that the toxicity of the metals was generally similar for both groups of Hydra. However, at the lowest copper concentrations there was a difference between the two group of polyps, with aposymbiotic animals dying at concentrations where symbiotic Hydra survived. The lowest observed effect concentrations were 0.0068 and 0.016 mg/L for aposymbiotic and symbiotic Hydra, respectively. It is suggested that the symbiotic Hydra derive benefits from the association that enable them to better tolerate the toxicant. This work demonstrated that experimental manipulation of symbionts can help to explain their complex interactions and the ways in which they respond to pollutants.

  1. Multi Groups Cooperation based Symbiotic Evolution for TSK-type Neuro-Fuzzy Systems Design

    PubMed Central

    Cheng, Yi-Chang; Hsu, Yung-Chi

    2010-01-01

    In this paper, a TSK-type neuro-fuzzy system with multi groups cooperation based symbiotic evolution method (TNFS-MGCSE) is proposed. The TNFS-MGCSE is developed from symbiotic evolution. The symbiotic evolution is different from traditional GAs (genetic algorithms) that each chromosome in symbiotic evolution represents a rule of fuzzy model. The MGCSE is different from the traditional symbiotic evolution; with a population in MGCSE is divided to several groups. Each group formed by a set of chromosomes represents a fuzzy rule and cooperate with other groups to generate the better chromosomes by using the proposed cooperation based crossover strategy (CCS). In this paper, the proposed TNFS-MGCSE is used to evaluate by numerical examples (Mackey-Glass chaotic time series and sunspot number forecasting). The performance of the TNFS-MGCSE achieves excellently with other existing models in the simulations. PMID:21709856

  2. Multi Groups Cooperation based Symbiotic Evolution for TSK-type Neuro-Fuzzy Systems Design.

    PubMed

    Cheng, Yi-Chang; Hsu, Yung-Chi; Lin, Sheng-Fuu

    2010-07-01

    In this paper, a TSK-type neuro-fuzzy system with multi groups cooperation based symbiotic evolution method (TNFS-MGCSE) is proposed. The TNFS-MGCSE is developed from symbiotic evolution. The symbiotic evolution is different from traditional GAs (genetic algorithms) that each chromosome in symbiotic evolution represents a rule of fuzzy model. The MGCSE is different from the traditional symbiotic evolution; with a population in MGCSE is divided to several groups. Each group formed by a set of chromosomes represents a fuzzy rule and cooperate with other groups to generate the better chromosomes by using the proposed cooperation based crossover strategy (CCS). In this paper, the proposed TNFS-MGCSE is used to evaluate by numerical examples (Mackey-Glass chaotic time series and sunspot number forecasting). The performance of the TNFS-MGCSE achieves excellently with other existing models in the simulations.

  3. Symbiotic crabs maintain coral health by clearing sediments

    NASA Astrophysics Data System (ADS)

    Stewart, Hannah L.; Holbrook, Sally J.; Schmitt, Russell J.; Brooks, Andrew J.

    2006-11-01

    Stony corals are the foundation of coral reef ecosystems and form associations with other reef species. Many of these associations may be ecologically important and play a role in maintaining the health and diversity of reef systems, rendering it critical to understand the influence of symbiotic organisms in mediating responses to perturbation. This study demonstrates the importance of an association with trapeziid crabs in reducing adverse effects of sediments deposited on corals. In a field experiment, mortality rates of two species of branching corals were significantly lowered by the presence of crabs. All outplanted corals with crabs survived whereas 45-80% of corals without crabs died within a month. For surviving corals that lacked crabs, growth was slower and tissue bleaching and sediment load were higher. Laboratory experiments revealed that corals with crabs shed substantially more of the sediments deposited on coral surfaces, but also that crabs were most effective at removing grain sizes that were most damaging to coral tissues. The mechanism underlying this symbiotic relationship has not been recognized previously, and its role in maintaining coral health is likely to become even more critical as reefs worldwide experience increasing sedimentation.

  4. Unraveling the nitrogen isotopic signature of symbiotic corals

    NASA Astrophysics Data System (ADS)

    Devlin, Q.; Swart, P. K.; Altabet, M. A.

    2013-12-01

    Coral reefs thrive in shallow, tropical, low nutrient waters. Nutrient inputs to a reef environment are often interpreted by measuring the nitrogen isotopic composition of reef organisms. The δ15N signature of scleractinian corals has been historically measured to assess the presence of anthropogenic influences such as sewage and fertilizer runoff. The majority of reef building corals form a symbiotic partnership with the dinoflagellate algae, Symbiodinium microadriaticum. The δ15N signature of symbiotic corals is complex as it is not only dependent on nitrogen acquisition by the coral, but also by the algal symbionts that reside within the gastrodermal tissue layer. The relationship between the δ15N of dissolved inorganic nitrogen (DIN) and the δ15N of coral tissue has not been established. The aim of this study is to identify considerations necessary when interpreting nitrogen sources based on δ15N of coral tissue. Incubations were carried out in order to measure isotopic fractionation associated with nitrate and ammonium incorporation by the Pacific branching coral, Pocillopora damicornis. We investigated the dependence of nitrogen isotope fractionation on species of DIN (nitrate or ammonium), concentration of DIN (range: 1-50 μM N), genetic diversity of algal symbionts (clade C or clade D) and light levels.

  5. Symbiotic symbolization by hand and mouth in sign language*

    PubMed Central

    Sandler, Wendy

    2010-01-01

    Current conceptions of human language include a gestural component in the communicative event. However, determining how the linguistic and gestural signals are distinguished, how each is structured, and how they interact still poses a challenge for the construction of a comprehensive model of language. This study attempts to advance our understanding of these issues with evidence from sign language. The study adopts McNeill’s criteria for distinguishing gestures from the linguistically organized signal, and provides a brief description of the linguistic organization of sign languages. Focusing on the subcategory of iconic gestures, the paper shows that signers create iconic gestures with the mouth, an articulator that acts symbiotically with the hands to complement the linguistic description of objects and events. A new distinction between the mimetic replica and the iconic symbol accounts for the nature and distribution of iconic mouth gestures and distinguishes them from mimetic uses of the mouth. Symbiotic symbolization by hand and mouth is a salient feature of human language, regardless of whether the primary linguistic modality is oral or manual. Speakers gesture with their hands, and signers gesture with their mouths. PMID:20445832

  6. Symbiotic bacteria enable insect to use a nutritionally inadequate diet.

    PubMed

    Akman Gündüz, E; Douglas, A E

    2009-03-07

    Animals generally require a dietary supply of various nutrients (vitamins, essential amino acids, etc.) because their biosynthetic capabilities are limited. The capacity of aphids to use plant phloem sap, with low essential amino acid content, has been attributed to their symbiotic bacteria, Buchnera aphidicola, which can synthesize these nutrients; but this has not been demonstrated empirically. We demonstrate here that phloem sap obtained from the severed stylets of pea aphids Acyrthosiphon pisum feeding on Vicia faba plants generally provided inadequate amounts of at least one essential amino acid to support aphid growth. Complementary analyses using aphids reared on chemically defined diets with each amino acid individually omitted revealed that the capacity of the symbiotic bacterium B. aphidicola to synthesize essential amino acids exceeded the dietary deficit of all phloem amino acids except methionine. It is proposed that this shortfall of methionine was met by aphid usage of the non-protein amino acid 5-methylmethionine in the phloem sap. This study provides the first quantitative demonstration that bacterial symbiosis can meet the nutritional demand of plant-reared aphids. It shows how symbiosis with micro-organisms has enabled this group of animals to escape from the constraint of requiring a balanced dietary supply of amino acids.

  7. Symbiotic bacteria enable insect to use a nutritionally inadequate diet

    PubMed Central

    Akman Gündüz, E.; Douglas, A.E.

    2008-01-01

    Animals generally require a dietary supply of various nutrients (vitamins, essential amino acids, etc.) because their biosynthetic capabilities are limited. The capacity of aphids to use plant phloem sap, with low essential amino acid content, has been attributed to their symbiotic bacteria, Buchnera aphidicola, which can synthesize these nutrients; but this has not been demonstrated empirically. We demonstrate here that phloem sap obtained from the severed stylets of pea aphids Acyrthosiphon pisum feeding on Vicia faba plants generally provided inadequate amounts of at least one essential amino acid to support aphid growth. Complementary analyses using aphids reared on chemically defined diets with each amino acid individually omitted revealed that the capacity of the symbiotic bacterium B. aphidicola to synthesize essential amino acids exceeded the dietary deficit of all phloem amino acids except methionine. It is proposed that this shortfall of methionine was met by aphid usage of the non-protein amino acid 5-methylmethionine in the phloem sap. This study provides the first quantitative demonstration that bacterial symbiosis can meet the nutritional demand of plant-reared aphids. It shows how symbiosis with micro-organisms has enabled this group of animals to escape from the constraint of requiring a balanced dietary supply of amino acids. PMID:19129128

  8. Extensive Differences in Gene Expression Between Symbiotic and Aposymbiotic Cnidarians

    PubMed Central

    Lehnert, Erik M.; Mouchka, Morgan E.; Burriesci, Matthew S.; Gallo, Natalya D.; Schwarz, Jodi A.; Pringle, John R.

    2013-01-01

    Coral reefs provide habitats for a disproportionate number of marine species relative to the small area of the oceans that they occupy. The mutualism between the cnidarian animal hosts and their intracellular dinoflagellate symbionts provides the nutritional foundation for coral growth and formation of reef structures, because algal photosynthesis can provide >90% of the total energy of the host. Disruption of this symbiosis (“coral bleaching”) is occurring on a large scale due primarily to anthropogenic factors and poses a major threat to the future of coral reefs. Despite the importance of this symbiosis, the cellular mechanisms involved in its establishment, maintenance, and breakdown remain largely unknown. We report our continued development of genomic tools to study these mechanisms in Aiptasia, a small sea anemone with great promise as a model system for studies of cnidarian–dinoflagellate symbiosis. Specifically, we have generated de novo assemblies of the transcriptomes of both a clonal line of symbiotic anemones and their endogenous dinoflagellate symbionts. We then compared transcript abundances in animals with and without dinoflagellates. This analysis identified >900 differentially expressed genes and allowed us to generate testable hypotheses about the cellular functions affected by symbiosis establishment. The differentially regulated transcripts include >60 encoding proteins that may play roles in transporting various nutrients between the symbiotic partners; many more encoding proteins functioning in several metabolic pathways, providing clues regarding how the transported nutrients may be used by the partners; and several encoding proteins that may be involved in host recognition and tolerance of the dinoflagellate. PMID:24368779

  9. Generating the Simple Decision Tree with Symbiotic Evolution

    NASA Astrophysics Data System (ADS)

    Otani, Noriko; Shimura, Masamichi

    In representing classification rules by decision trees, simplicity of tree structure is as important as predictive accuracy especially in consideration of the comprehensibility to a human, the memory capacity and the time required to classify. Trees tend to be complex when they get high accuracy. This paper proposes a novel method for generating accurate and simple decision trees based on symbiotic evolution. It is distinctive of symbiotic evolution that two different populations are evolved in parallel through genetic algorithms. In our method one's individuals are partial trees of height 1, and the other's individuals are whole trees represented by the combinations of the former individuals. Generally, overfitting to training examples prevents getting high predictive accuracy. In order to circumvent this difficulty, individuals are evaluated with not only the accuracy in training examples but also the correct answer biased rate indicating the dispersion of the correct answers in the terminal nodes. Based on our method we developed a system called SESAT for generating decision trees. Our experimental results show that SESAT compares favorably with other systems on several datasets in the UCI repository. SESAT has the ability to generate more simple trees than C5.0 without sacrificing predictive accuracy.

  10. Colored-noise-induced discontinuous transitions in symbiotic ecosystems

    NASA Astrophysics Data System (ADS)

    Mankin, Romi; Sauga, Ako; Ainsaar, Ain; Haljas, Astrid; Paunel, Kristiina

    2004-06-01

    A symbiotic ecosystem is studied by means of the Lotka-Volterra stochastic model, using the generalized Verhulst self-regulation. The effect of fluctuating environment on the carrying capacity of a population is taken into account as dichotomous noise. The study is a follow-up of our investigation of symbiotic ecosystems subjected to three-level (trichotomous) noise [

    R. Mankin, A. Ainsaar, A. Haljas, and E. Reiter, Phys. Rev. E 65, 051108 (2002)
    ]. Relying on the mean-field theory, an exact self-consistency equation for stationary states is derived. In some cases the mean field exhibits hysteresis as a function of noise parameters. It is established that random interactions with the environment can cause discontinuous transitions. The dependence of the critical coupling strengths on the noise parameters is found and illustrated by phase diagrams. Predictions from the mean-field theory are compared with the results of numerical simulations. Our results provide a possible scenario for catastrophic shifts of population sizes observed in nature.

  11. Non-symbiotic Bradyrhizobium ecotypes dominate North American forest soils.

    PubMed

    VanInsberghe, David; Maas, Kendra R; Cardenas, Erick; Strachan, Cameron R; Hallam, Steven J; Mohn, William W

    2015-11-01

    The genus Bradyrhizobium has served as a model system for studying host-microbe symbiotic interactions and nitrogen fixation due to its importance in agricultural productivity and global nitrogen cycling. In this study, we identify a bacterial group affiliated with this genus that dominates the microbial communities of coniferous forest soils from six distinct ecozones across North America. Representative isolates from this group were obtained and characterized. Using quantitative population genomics, we show that forest soil populations of Bradyrhizobium represent ecotypes incapable of nodulating legume root hairs or fixing atmospheric nitrogen. Instead, these populations appear to be free living and have a greater potential for metabolizing aromatic carbon sources than their close symbiotic relatives. In addition, we identify fine-scaled differentiation between populations inhabiting neighboring soil layers that illustrate how diversity within Bradyrhizobium is structured by habitat similarity. These findings reconcile incongruent observations about this widely studied and important group of bacteria and highlight the value of ecological context to interpretations of microbial diversity and taxonomy. These results further suggest that the influence of this genus likely extends well beyond facilitating agriculture, especially as forest ecosystems are large and integral components of the biosphere. In addition, this study demonstrates how focusing research on economically important microorganisms can bias our understanding of the natural world.

  12. Outbursts by low-mass white dwarfs in symbiotic variables

    NASA Technical Reports Server (NTRS)

    Sion, Edward M.; Ready, Christian J.

    1992-01-01

    The high-resolution IUE spectra of the symbiotic variables BF Cygni and EG Andromedae are studied in order to describe the P Cygni-like features of these objects. The 10 high-dispersion IUE spectra are examined for orbital phase-dependent variations in the C IV resonance doublet in terms of velocity and/or structure. One image is found to have a strong He-II absorption feature that coincides in velocity with the C-IV absorption component in P Cygni. The absorbing material for both lines is related to outflow and P Cygni self-absorption near the hot component. The P Cygni profiles do not appear to be related to a red-giant wind nor an expanding circumbinary shell in the in both BF Cyg and EG And. Quasi-static evolutionary model calculations demonstrate an unexpected outburst behavior in response to the assumed accretion. These data are shown to be important for the study of symbiotic systems that contain low-mass white dwarfs.

  13. A statistical anomaly indicates symbiotic origins of eukaryotic membranes

    PubMed Central

    Bansal, Suneyna; Mittal, Aditya

    2015-01-01

    Compositional analyses of nucleic acids and proteins have shed light on possible origins of living cells. In this work, rigorous compositional analyses of ∼5000 plasma membrane lipid constituents of 273 species in the three life domains (archaea, eubacteria, and eukaryotes) revealed a remarkable statistical paradox, indicating symbiotic origins of eukaryotic cells involving eubacteria. For lipids common to plasma membranes of the three domains, the number of carbon atoms in eubacteria was found to be similar to that in eukaryotes. However, mutually exclusive subsets of same data show exactly the opposite—the number of carbon atoms in lipids of eukaryotes was higher than in eubacteria. This statistical paradox, called Simpson's paradox, was absent for lipids in archaea and for lipids not common to plasma membranes of the three domains. This indicates the presence of interaction(s) and/or association(s) in lipids forming plasma membranes of eubacteria and eukaryotes but not for those in archaea. Further inspection of membrane lipid structures affecting physicochemical properties of plasma membranes provides the first evidence (to our knowledge) on the symbiotic origins of eukaryotic cells based on the “third front” (i.e., lipids) in addition to the growing compositional data from nucleic acids and proteins. PMID:25631820

  14. Symbiotic symbolization by hand and mouth in sign language.

    PubMed

    Sandler, Wendy

    2009-04-01

    Current conceptions of human language include a gestural component in the communicative event. However, determining how the linguistic and gestural signals are distinguished, how each is structured, and how they interact still poses a challenge for the construction of a comprehensive model of language. This study attempts to advance our understanding of these issues with evidence from sign language. The study adopts McNeill's criteria for distinguishing gestures from the linguistically organized signal, and provides a brief description of the linguistic organization of sign languages. Focusing on the subcategory of iconic gestures, the paper shows that signers create iconic gestures with the mouth, an articulator that acts symbiotically with the hands to complement the linguistic description of objects and events. A new distinction between the mimetic replica and the iconic symbol accounts for the nature and distribution of iconic mouth gestures and distinguishes them from mimetic uses of the mouth. Symbiotic symbolization by hand and mouth is a salient feature of human language, regardless of whether the primary linguistic modality is oral or manual. Speakers gesture with their hands, and signers gesture with their mouths.

  15. A slowly evolving host moves first in symbiotic interactions

    NASA Astrophysics Data System (ADS)

    Damore, James; Gore, Jeff

    2011-03-01

    Symbiotic relationships, both parasitic and mutualistic, are ubiquitous in nature. Understanding how these symbioses evolve, from bacteria and their phages to humans and our gut microflora, is crucial in understanding how life operates. Often, symbioses consist of a slowly evolving host species with each host only interacting with its own sub-population of symbionts. The Red Queen hypothesis describes coevolutionary relationships as constant arms races with each species rushing to evolve an advantage over the other, suggesting that faster evolution is favored. Here, we use a simple game theoretic model of host- symbiont coevolution that includes population structure to show that if the symbionts evolve much faster than the host, the equilibrium distribution is the same as it would be if it were a sequential game where the host moves first against its symbionts. For the slowly evolving host, this will prove to be advantageous in mutualisms and a handicap in antagonisms. The model allows for symbiont adaptation to its host, a result that is robust to changes in the parameters and generalizes to continuous and multiplayer games. Our findings provide insight into a wide range of symbiotic phenomena and help to unify the field of coevolutionary theory.

  16. Extensive differences in gene expression between symbiotic and aposymbiotic cnidarians.

    PubMed

    Lehnert, Erik M; Mouchka, Morgan E; Burriesci, Matthew S; Gallo, Natalya D; Schwarz, Jodi A; Pringle, John R

    2014-02-19

    Coral reefs provide habitats for a disproportionate number of marine species relative to the small area of the oceans that they occupy. The mutualism between the cnidarian animal hosts and their intracellular dinoflagellate symbionts provides the nutritional foundation for coral growth and formation of reef structures, because algal photosynthesis can provide >90% of the total energy of the host. Disruption of this symbiosis ("coral bleaching") is occurring on a large scale due primarily to anthropogenic factors and poses a major threat to the future of coral reefs. Despite the importance of this symbiosis, the cellular mechanisms involved in its establishment, maintenance, and breakdown remain largely unknown. We report our continued development of genomic tools to study these mechanisms in Aiptasia, a small sea anemone with great promise as a model system for studies of cnidarian-dinoflagellate symbiosis. Specifically, we have generated de novo assemblies of the transcriptomes of both a clonal line of symbiotic anemones and their endogenous dinoflagellate symbionts. We then compared transcript abundances in animals with and without dinoflagellates. This analysis identified >900 differentially expressed genes and allowed us to generate testable hypotheses about the cellular functions affected by symbiosis establishment. The differentially regulated transcripts include >60 encoding proteins that may play roles in transporting various nutrients between the symbiotic partners; many more encoding proteins functioning in several metabolic pathways, providing clues regarding how the transported nutrients may be used by the partners; and several encoding proteins that may be involved in host recognition and tolerance of the dinoflagellate.

  17. 15N discrimination and the sensitivity of nitrogen fixation to changes in dietary nitrogen in Reticulitermes flavipes (Isoptera: Rhinotermitidae).

    PubMed

    Meuti, Megan E; Jones, Susan C; Curtis, Peter S

    2010-12-01

    Xylophagous termites possess symbiotic bacteria that fix atmospheric nitrogen (N(2)). Although symbiotic N(2) fixation is central to termite nutrition and ecologically important, it is energetically costly. Using stable isotopes, we tested the hypothesis that symbiotic N(2) fixation would decrease in workers of the eastern subterranean termite, Reticulitermes flavipes Kollar, which were exposed to high nitrogen diets. To calculate the isotope discrimination factor occurring as a result of digestion, Δ(dig), and which occurs as the result of N(2) fixation, Δ(fix), symbiotic N(2) fixation was inhibited via force feeding termites the antibiotic kanamycin. Antibiotic-treated termites and control (N(2)-fixing) termites were exposed to different concentrations of dietary N (0, 0.21, and 0.94% N), their (15)N signatures were obtained, and the percent nitrogen derived from the atmosphere within termite samples was calculated. As we hypothesized, symbiotic N(2) fixation rates were negatively correlated with dietary N, suggesting that high concentrations of dietary N suppressed symbiotic N(2) fixation in R. flavipes. A comparison of the (15)N isotope signatures of antibiotic-treated termites with their food sources demonstrated that Δ(dig) = 2.284‰, and a comparison of the (15)N isotope signatures of antibiotic-treated termites with control termites indicated that Δ(fix) = -1.238‰. These are the first estimates of Δ(dig) for R. flavipes, and the first estimate of Δ(fix) for any N(2)-fixing termite species.

  18. Two Major Clades of Bradyrhizobia Dominate Symbiotic Interactions with Pigeonpea in Fields of Côte d'Ivoire

    PubMed Central

    Fossou, Romain K.; Ziegler, Dominik; Zézé, Adolphe; Barja, François; Perret, Xavier

    2016-01-01

    In smallholder farms of Côte d'Ivoire, particularly in the northeast of the country, Cajanus cajan (pigeonpea) has become an important crop because of its multiple beneficial facets. Pigeonpea seeds provide food to make ends meet, are sold on local markets, and aerial parts serve as forage for animals. Since it fixes atmospheric nitrogen in symbiosis with soil bacteria collectively known as rhizobia, C. cajan also improves soil fertility and reduces fallow time. Yet, seed yields remain low mostly because farmers cannot afford chemical fertilizers. To identify local rhizobial strains susceptible to be used as bio-inoculants to foster pigeonpea growth, root nodules were collected in six fields of three geographically distant regions of Côte d'Ivoire. Nodule bacteria were isolated and characterized using various molecular techniques including matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) and DNA sequencing. These molecular analyses showed that 63 out of 85 nodule isolates belonged to two major clades of bradyrhizobia, one of which is known as the Bradyrhizobium elkanii super clade. Phylogenies of housekeeping (16S-ITS-23S, rpoB) and symbiotic (nifH) genes were not always congruent suggesting that lateral transfer of nitrogen fixation genes also contributed to define the genome of these bradyrhizobial isolates. Interestingly, no field-, plant-, or cultivar-specific effect was found to shape the profiles of symbiotic strains. In addition, nodule isolates CI-1B, CI-36E, and CI-41A that belong to distinct species, showed similar symbiotic efficiencies suggesting that any of these strains might serve as a proficient inoculant for C. cajan. PMID:27891120

  19. Evolution of high cellulolytic activity in symbiotic Streptomyces through selection of expanded gene content and coordinated gene expression

    DOE PAGES

    Book, Adam J.; Lewin, Gina R.; McDonald, Bradon R.; ...

    2016-06-08

    In this study, the evolution of cellulose degradation was a defining event in the history of life. Without efficient decomposition and recycling, dead plant biomass would quickly accumulate and become inaccessible to terrestrial food webs and the global carbon cycle. On land, the primary drivers of plant biomass deconstruction are fungi and bacteria in the soil or associated with herbivorous eukaryotes. While the ecological importance of plant-decomposing microbes is well established, little is known about the distribution or evolution of cellulolytic activity in any bacterial genus. Here we show that in Streptomyces, a genus of Actinobacteria abundant in soil andmore » symbiotic niches, the ability to rapidly degrade cellulose is largely restricted to two clades of host-associated strains and is not a conserved characteristic of the Streptomyces genus or host-associated strains. Our comparative genomics identify that while plant biomass degrading genes (CAZy) are widespread in Streptomyces, key enzyme families are enriched in highly cellulolytic strains. Transcriptomic analyses demonstrate that cellulolytic strains express a suite of multi-domain CAZy enzymes that are coregulated by the CebR transcriptional regulator. Using targeted gene deletions, we verify the importance of a highly expressed cellulase (GH6 family cellobiohydrolase) and the CebR transcriptional repressor to the cellulolytic phenotype. Evolutionary analyses identify complex genomic modifications that drive plant biomass deconstruction in Streptomyces, including acquisition and selective retention of CAZy genes and transcriptional regulators. Our results suggest that host-associated niches have selected some symbiotic Streptomyces for increased cellulose degrading activity and that symbiotic bacteria are a rich biochemical and enzymatic resource for biotechnology.« less

  20. Evolution of High Cellulolytic Activity in Symbiotic Streptomyces through Selection of Expanded Gene Content and Coordinated Gene Expression.

    PubMed

    Book, Adam J; Lewin, Gina R; McDonald, Bradon R; Takasuka, Taichi E; Wendt-Pienkowski, Evelyn; Doering, Drew T; Suh, Steven; Raffa, Kenneth F; Fox, Brian G; Currie, Cameron R

    2016-06-01

    The evolution of cellulose degradation was a defining event in the history of life. Without efficient decomposition and recycling, dead plant biomass would quickly accumulate and become inaccessible to terrestrial food webs and the global carbon cycle. On land, the primary drivers of plant biomass deconstruction are fungi and bacteria in the soil or associated with herbivorous eukaryotes. While the ecological importance of plant-decomposing microbes is well established, little is known about the distribution or evolution of cellulolytic activity in any bacterial genus. Here we show that in Streptomyces, a genus of Actinobacteria abundant in soil and symbiotic niches, the ability to rapidly degrade cellulose is largely restricted to two clades of host-associated strains and is not a conserved characteristic of the Streptomyces genus or host-associated strains. Our comparative genomics identify that while plant biomass degrading genes (CAZy) are widespread in Streptomyces, key enzyme families are enriched in highly cellulolytic strains. Transcriptomic analyses demonstrate that cellulolytic strains express a suite of multi-domain CAZy enzymes that are coregulated by the CebR transcriptional regulator. Using targeted gene deletions, we verify the importance of a highly expressed cellulase (GH6 family cellobiohydrolase) and the CebR transcriptional repressor to the cellulolytic phenotype. Evolutionary analyses identify complex genomic modifications that drive plant biomass deconstruction in Streptomyces, including acquisition and selective retention of CAZy genes and transcriptional regulators. Our results suggest that host-associated niches have selected some symbiotic Streptomyces for increased cellulose degrading activity and that symbiotic bacteria are a rich biochemical and enzymatic resource for biotechnology.

  1. Two Major Clades of Bradyrhizobia Dominate Symbiotic Interactions with Pigeonpea in Fields of Côte d'Ivoire.

    PubMed

    Fossou, Romain K; Ziegler, Dominik; Zézé, Adolphe; Barja, François; Perret, Xavier

    2016-01-01

    In smallholder farms of Côte d'Ivoire, particularly in the northeast of the country, Cajanus cajan (pigeonpea) has become an important crop because of its multiple beneficial facets. Pigeonpea seeds provide food to make ends meet, are sold on local markets, and aerial parts serve as forage for animals. Since it fixes atmospheric nitrogen in symbiosis with soil bacteria collectively known as rhizobia, C. cajan also improves soil fertility and reduces fallow time. Yet, seed yields remain low mostly because farmers cannot afford chemical fertilizers. To identify local rhizobial strains susceptible to be used as bio-inoculants to foster pigeonpea growth, root nodules were collected in six fields of three geographically distant regions of Côte d'Ivoire. Nodule bacteria were isolated and characterized using various molecular techniques including matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) and DNA sequencing. These molecular analyses showed that 63 out of 85 nodule isolates belonged to two major clades of bradyrhizobia, one of which is known as the Bradyrhizobium elkanii super clade. Phylogenies of housekeeping (16S-ITS-23S, rpoB) and symbiotic (nifH) genes were not always congruent suggesting that lateral transfer of nitrogen fixation genes also contributed to define the genome of these bradyrhizobial isolates. Interestingly, no field-, plant-, or cultivar-specific effect was found to shape the profiles of symbiotic strains. In addition, nodule isolates CI-1B, CI-36E, and CI-41A that belong to distinct species, showed similar symbiotic efficiencies suggesting that any of these strains might serve as a proficient inoculant for C. cajan.

  2. Evolution of High Cellulolytic Activity in Symbiotic Streptomyces through Selection of Expanded Gene Content and Coordinated Gene Expression

    PubMed Central

    McDonald, Bradon R.; Takasuka, Taichi E.; Wendt-Pienkowski, Evelyn; Doering, Drew T.; Raffa, Kenneth F.; Fox, Brian G.; Currie, Cameron R.

    2016-01-01

    The evolution of cellulose degradation was a defining event in the history of life. Without efficient decomposition and recycling, dead plant biomass would quickly accumulate and become inaccessible to terrestrial food webs and the global carbon cycle. On land, the primary drivers of plant biomass deconstruction are fungi and bacteria in the soil or associated with herbivorous eukaryotes. While the ecological importance of plant-decomposing microbes is well established, little is known about the distribution or evolution of cellulolytic activity in any bacterial genus. Here we show that in Streptomyces, a genus of Actinobacteria abundant in soil and symbiotic niches, the ability to rapidly degrade cellulose is largely restricted to two clades of host-associated strains and is not a conserved characteristic of the Streptomyces genus or host-associated strains. Our comparative genomics identify that while plant biomass degrading genes (CAZy) are widespread in Streptomyces, key enzyme families are enriched in highly cellulolytic strains. Transcriptomic analyses demonstrate that cellulolytic strains express a suite of multi-domain CAZy enzymes that are coregulated by the CebR transcriptional regulator. Using targeted gene deletions, we verify the importance of a highly expressed cellulase (GH6 family cellobiohydrolase) and the CebR transcriptional repressor to the cellulolytic phenotype. Evolutionary analyses identify complex genomic modifications that drive plant biomass deconstruction in Streptomyces, including acquisition and selective retention of CAZy genes and transcriptional regulators. Our results suggest that host-associated niches have selected some symbiotic Streptomyces for increased cellulose degrading activity and that symbiotic bacteria are a rich biochemical and enzymatic resource for biotechnology. PMID:27276034

  3. Termites create spatial structure and govern ecosystem function by affecting N2 fixation in an East African savanna.

    PubMed

    Fox-Dobbs, Kena; Doak, Daniel F; Brody, Alison K; Palmer, Todd M

    2010-05-01

    The mechanisms by which even the clearest of keystone or dominant species exert community-wide effects are only partially understood in most ecosystems. This is especially true when a species or guild influences community-wide interactions via changes in the abiotic landscape. Using stable isotope analyses, we show that subterranean termites in an East African savanna strongly influence a key ecosystem process: atmospheric nitrogen fixation by a monodominant tree species and its bacterial symbionts. Specifically, we applied the 15N natural abundance method in combination with other biogeochemical analyses to assess levels of nitrogen fixation by Acacia drepanolobium and its effects on co-occurring grasses and forbs in areas near and far from mounds and where ungulates were or were not excluded. We find that termites exert far stronger effects than do herbivores on nitrogen fixation. The percentage of nitrogen derived from fixation in Acacia drepanolobium trees is higher (55-80%) away from mounds vs. near mounds (40-50%). Mound soils have higher levels of plant available nitrogen, and Acacia drepanolobium may preferentially utilize soil-based nitrogen sources in lieu of fixed nitrogen when these sources are readily available near termite mounds. At the scale of the landscape, our models predict that termite/soil derived nitrogen sources influence >50% of the Acacia drepanolobium trees in our system. Further, the spatial extent of these effects combine with the spacing of termite mounds to create highly regular patterning in nitrogen fixation rates, resulting in marked habitat heterogeneity in an otherwise uniform landscape. In summary, we show that termite-associated effects on nitrogen processes are not only stronger than those of more apparent large herbivores in the same system, but also occur in a highly regular spatial pattern, potentially adding to their importance as drivers of community and ecosystem structure.

  4. (15)N natural abundance in plants of the Amazon River floodplain and potential atmospheric N2 fixation.

    PubMed

    Martinelli, L A; Victoria, R L; Trivelin, P C O; Devol, A H; Richey, J E

    1992-07-01

    The(15)N natural abundance values of various Amazon floodplain (várzea) plants was investigated. Samples of young leaf tissues were collected during three different periods of the river hydrography (low water, mid rising water and high water) and during one period in the Madeira River (high water). A large variation of(15)N abundance was observed, both among the different plant types and between the different flood stages. This variation probably, reflected, in part, the highly variable nature of the floodplain, sometimes dry and oxygenated and at other times inundated and anaerobic and, in part, changes in plant nitrogen metabolism. Comparison of the nitrogen isotopic composition of leguminous plants with that of non-leguminous plants showed that, on average, the(15)N abundance was lower in the legumes than non-legumes, suggesting active N-fixation. Also, the(15)N natural abundance in aquatic grasses of the generaPaspalum, was in general, lower than the(15)N abundance of aquatic grasses of the generaEchinochloa. As both of these grasses grow in the same general habitat, it appears thatPaspalum grasses may also be nitrogen fixers.

  5. Symbiotic Navigation in Multi-Robot Systems with Remote Obstacle Knowledge Sharing

    PubMed Central

    Ravankar, Abhijeet; Ravankar, Ankit A.; Kobayashi, Yukinori; Emaru, Takanori

    2017-01-01

    Large scale operational areas often require multiple service robots for coverage and task parallelism. In such scenarios, each robot keeps its individual map of the environment and serves specific areas of the map at different times. We propose a knowledge sharing mechanism for multiple robots in which one robot can inform other robots about the changes in map, like path blockage, or new static obstacles, encountered at specific areas of the map. This symbiotic information sharing allows the robots to update remote areas of the map without having to explicitly navigate those areas, and plan efficient paths. A node representation of paths is presented for seamless sharing of blocked path information. The transience of obstacles is modeled to track obstacles which might have been removed. A lazy information update scheme is presented in which only relevant information affecting the current task is updated for efficiency. The advantages of the proposed method for path planning are discussed against traditional method with experimental results in both simulation and real environments. PMID:28678193

  6. Journal entries facilitating preprofessional scientific literacy and mutualistic symbiotic relationships

    NASA Astrophysics Data System (ADS)

    Vander Vliet, Valerie J.

    This study explored journal writing as an alternative assessment to promote the development of pre-professional scientific literacy and mutualistic symbiotic relationships between teaching and learning, instruction and assessment, and students and teachers. The larger context of this study is an action reaction project of the attempted transformation of a traditional first year undergraduate pre-professional biology class to sociocultural constructivist principles. The participants were commuter and residential, full and part-time students ranging in age from 18 to 27 and 18/21 were female. The backgrounds of the students varied considerably, ranging from low to upper middle income, including students of Black and Asian heritage. The setting was a medium-sized Midwestern university. The instructor has twenty years of experience teaching Biology at the college level. The data were analyzed using the constant comparative method and the development of grounded theory. The journal entries were analyzed as to their function and form in relationship to the development of multiple aspects of pre-professional scientific literacy. The perceptions of the students as to the significance of the use of journal entries were also determined through the analysis of their use of journal entries in their portfolios and statements in surveys and portfolios. The analysis revealed that journal entries promoted multiple aspects of pre-professional scientific literacy in both students and the instructor and facilitated the development of mutualistic symbiotic relationships between teaching and learning, instruction and assessment, and students and teachers. The function analysis revealed that the journal entries fulfilled the functions intended for the development of multiple aspects of pre-professional scientific literacy. The complexity of journal writing emerged from the form analysis, which revealed the multiple form elements inherent in journal entries. Students perceived journal

  7. Recurrent evolution of gut symbiotic bacteria in pentatomid stinkbugs.

    PubMed

    Hosokawa, Takahiro; Matsuura, Yu; Kikuchi, Yoshitomo; Fukatsu, Takema

    2016-01-01

    Diverse animals are intimately associated with microbial symbionts. How such host-symbiont associations have evolved is a fundamental biological issue. Recent studies have revealed a variety of evolutionary relationships, such as obligatory, facultative, and free-living, of gut bacterial symbiosis within the stinkbug family Pentatomidae, although the whole evolutionary picture remains elusive. Here we investigated a comprehensive assembly of Japanese pentatomid stinkbugs representing 28 genera, 35 species, and 143 populations. Polymerase chain reaction (PCR), cloning, and sequencing of bacterial 16S rRNA gene from their midgut symbiotic organ consistently detected a single bacterial species from each of the insect samples, indicating a general tendency toward monosymbiotic gut association. Bacterial sequences detected from different populations of the same species were completely or nearly identical, indicating that the majority of the gut symbiotic associations are stably maintained at the species level. Furthermore, bacterial sequences detected from different species in the same genus tended to form well-supported clades, suggesting that host-symbiont associations are often stable even at the genus level. Meanwhile, when we compared such sequences with published sequences available in DNA databases, we found a number of counter-examples to such stable host-symbiont relationships; i.e., symbionts from different host species in the same genus may be phylogenetically distant, and symbionts from the same host species may be phylogenetically diverse. Likewise, symbionts of diverse pentatomid species may be closely related to symbionts of other stinkbug families, and symbionts of diverse pentatomid species may even be allied to free-living bacteria. Molecular evolutionary analyses revealed that higher molecular evolutionary rates, higher AT nucleotide compositions, and smaller genome sizes tended to be associated with the pentatomid symbionts constituting the stable

  8. Coordinated rearrangements of assimilatory and storage cell compartments in a nitrogen-starving symbiotic chlorophyte cultivated under high light.

    PubMed

    Gorelova, Olga; Baulina, Olga; Solovchenko, Alexei; Selyakh, Irina; Chivkunova, Olga; Semenova, Larisa; Scherbakov, Pavel; Burakova, Olga; Lobakova, Elena

    2015-03-01

    A quantitative micromorphometric study of the cell compartment rearrangements was performed in a symbiotic chlorophyte Desmodesmus sp. 3Dp86E-1 grown on nitrogen (N) replete or N-free medium under 480 μmol PAR quanta m(-2) s(-1). The changes in the chloroplast, intraplastidial, and cytoplasmic inclusions induced by high light (HL) and N starvation were similar to those characteristic of free-living chlorophytes. The N-sufficient culture responded to HL by a transient swelling of the thylakoid lumen and a decline in photosynthetic efficiency followed by its recovery. In the N-starving cells, a more rapid expansion and thylakoid swelling occurred along with the irreversible decline in the photosynthetic efficiency. Differential induction of starch grains, oil bodies, and cell wall polysaccharides depending on the stress exposure and type was recorded. Tight relationships between the changes in the assimilatory and storage compartments in the stressed Desmodesmus sp. cells were revealed.

  9. A Remarkable Sample of New Symbiotic Stars Towards the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Miszalski, B.; Mikolajewska, J.; Udalski, A.

    2014-12-01

    Symbiotic stars are the longest orbital period interacting binaries, where nova-like outbursts are generated by the accretion of a high mass loss rate red giant wind onto a white dwarf companion. Long-term photometric monitoring surveys such as OGLE and MACHO are ideal platforms to identify nova-like events in symbiotic stars. However, there are only a handful of known systems within the small footprint of these surveys. We introduce a systematic Hα emission line object survey for new symbiotic stars covering 35 deg2 towards the Galactic Bulge that combines deep 2dF/AAOmega spectroscopy with OGLE and MACHO photometry. This powerful combination has uncovered nearly two dozen new symbiotic stars, more than a dozen probable symbiotic stars, and several other unusual Hα emission line stars. While we don't find any nova-like activity, the lightcurves do exhibit semi-regular and Mira pulsations, orbital variations and slower changes due to dust. Here we introduce a few of the new symbiotics, including H1-45, only the fourth known carbon symbiotic Mira. This remarkable discovery may be the first luminous carbon star belonging to the Galactic Bulge, according to its period-luminosity relation distance of 6.2±1.4 kpc, potentially shedding new light on the puzzling lack of luminous carbon stars in the Bulge. We also present two old novae captured in the nebular phase, complementing other surveys to better characterize the old nova population.

  10. SEARCHING FOR NEW YELLOW SYMBIOTIC STARS: POSITIVE IDENTIFICATION OF StHα63

    SciTech Connect

    Baella, N. O.; Pereira, C. B.; Alvarez-Candal, A.

    2016-04-15

    Yellow symbiotic stars are useful targets for probing whether mass transfer has happened in their binary systems. However, the number of known yellow symbiotic stars is very scarce. We report spectroscopic observations of five candidate yellow symbiotic stars that were selected by their positions in the 2MASS (J − H) versus (H − K{sub s}) diagram and which were included in some emission-line catalogs. Among the five candidates, only StHα63 is identified as a new yellow symbiotic star because of its spectrum and its position in the [TiO]{sub 1}–[TiO]{sub 2} diagram, which indicates a K4–K6 spectral type. In addition, the derived electron density (∼10{sup 8.4} cm{sup −3}) and several emission-line intensity ratios provide further support for that classification. The other four candidates are rejected as symbiotic stars because three of them actually do not show emission lines and the fourth one only Balmer emission lines. We also found that the WISE W3–W4 index clearly separates normal K-giants from yellow symbiotic stars and therefore can be used as an additional tool for selecting candidate yellow symbiotic stars.

  11. Evolutionary signals of symbiotic persistence in the legume–rhizobia mutualism

    PubMed Central

    Werner, Gijsbert D. A.; Cornwell, William K.; Cornelissen, Johannes H. C.; Kiers, E. Toby

    2015-01-01

    Understanding the origins and evolutionary trajectories of symbiotic partnerships remains a major challenge. Why are some symbioses lost over evolutionary time whereas others become crucial for survival? Here, we use a quantitative trait reconstruction method to characterize different evolutionary stages in the ancient symbiosis between legumes (Fabaceae) and nitrogen-fixing bacteria, asking how labile is symbiosis across different host clades. We find that more than half of the 1,195 extant nodulating legumes analyzed have a high likelihood (>95%) of being in a state of high symbiotic persistence, meaning that they show a continued capacity to form the symbiosis over evolutionary time, even though the partnership has remained facultative and is not obligate. To explore patterns associated with the likelihood of loss and retention of the N2-fixing symbiosis, we tested for correlations between symbiotic persistence and legume distribution, climate, soil and trait data. We found a strong latitudinal effect and demonstrated that low mean annual temperatures are associated with high symbiotic persistence in legumes. Although no significant correlations between soil variables and symbiotic persistence were found, nitrogen and phosphorus leaf contents were positively correlated with legumes in a state of high symbiotic persistence. This pattern suggests that highly demanding nutrient lifestyles are associated with more stable partnerships, potentially because they “lock” the hosts into symbiotic dependency. Quantitative reconstruction methods are emerging as a powerful comparative tool to study broad patterns of symbiont loss and retention across diverse partnerships. PMID:26041807

  12. Identification of new Galactic symbiotic stars with SALT - I. Initial discoveries and other emission line objects

    NASA Astrophysics Data System (ADS)

    Miszalski, Brent; Mikołajewska, Joanna

    2014-05-01

    We introduce the first results from an ongoing, systematic survey for new symbiotic stars selected from the AAO/UKST SuperCOSMOS Hα Survey. The survey aims to identify and characterize the fainter population of symbiotic stars under-represented in extant catalogues. The accreting white dwarfs (WDs) in symbiotic stars, fuelled by their red giant donors with high mass-loss rate winds, make them promising candidates for Type Ia supernovae. Several candidates were observed spectroscopically with the Southern African Large Telescope. A total of 12 bona fide and 3 possible symbiotic stars were identified. The most remarkable example is a rare carbon-rich symbiotic star that displays coronal [Fe X] λ6375 emission, suggesting it may be a supersoft X-ray source with a massive WD. Several other emission line objects with near-infrared colours similar to symbiotic stars are listed in an appendix, including six B[e] stars, four planetary nebulae (PNe), two possible Be stars, one [WC9] Wolf-Rayet (WR) central star of a PN and one WC9 WR star. These initial discoveries will help shape and refine the candidate selection criteria that we expect will uncover several more symbiotic stars as the survey progresses.

  13. [Response of arbuscular mycorrhizal fungal lipid metabolism to symbiotic signals in mycorrhiza].

    PubMed

    Tian, Lei; Li, Yuanjing; Tian, Chunjie

    2016-01-04

    Arbuscular mycorrhizal (AM) fungi play an important role in energy flow and nutrient cycling, besides their wide distribution in the cosystem. With a long co-evolution, AM fungi and host plant have formed a symbiotic relationship, and fungal lipid metabolism may be the key point to find the symbiotic mechanism in arbusculart mycorrhiza. Here, we reviewed the most recent progress on the interaction between AM fungal lipid metabolism and symbiotic signaling networks, especially the response of AM fungal lipid metabolism to symbiotic signals. Furthermore, we discussed the response of AM fungal lipid storage and release to symbiotic or non-symbiotic status, and the correlation between fungal lipid metabolism and nutrient transfer in mycorrhiza. In addition, we explored the feedback of the lipolysis process to molecular signals during the establishment of symbiosis, and the corresponding material conversion and energy metabolism besides the crosstalk of fungal lipid metabolism and signaling networks. This review will help understand symbiotic mechanism of arbuscular mycorrhiza fungi and further application in ecosystem.

  14. Evolutionary signals of symbiotic persistence in the legume-rhizobia mutualism.

    PubMed

    Werner, Gijsbert D A; Cornwell, William K; Cornelissen, Johannes H C; Kiers, E Toby

    2015-08-18

    Understanding the origins and evolutionary trajectories of symbiotic partnerships remains a major challenge. Why are some symbioses lost over evolutionary time whereas others become crucial for survival? Here, we use a quantitative trait reconstruction method to characterize different evolutionary stages in the ancient symbiosis between legumes (Fabaceae) and nitrogen-fixing bacteria, asking how labile is symbiosis across different host clades. We find that more than half of the 1,195 extant nodulating legumes analyzed have a high likelihood (>95%) of being in a state of high symbiotic persistence, meaning that they show a continued capacity to form the symbiosis over evolutionary time, even though the partnership has remained facultative and is not obligate. To explore patterns associated with the likelihood of loss and retention of the N2-fixing symbiosis, we tested for correlations between symbiotic persistence and legume distribution, climate, soil and trait data. We found a strong latitudinal effect and demonstrated that low mean annual temperatures are associated with high symbiotic persistence in legumes. Although no significant correlations between soil variables and symbiotic persistence were found, nitrogen and phosphorus leaf contents were positively correlated with legumes in a state of high symbiotic persistence. This pattern suggests that highly demanding nutrient lifestyles are associated with more stable partnerships, potentially because they "lock" the hosts into symbiotic dependency. Quantitative reconstruction methods are emerging as a powerful comparative tool to study broad patterns of symbiont loss and retention across diverse partnerships.

  15. Discovery of true, likely and possible symbiotic stars in the dwarf spheroidal NGC 205

    NASA Astrophysics Data System (ADS)

    Gonçalves, Denise R.; Magrini, Laura; de la Rosa, Ignacio G.; Akras, Stavros

    2015-02-01

    In this paper we discuss the photometric and spectroscopic observations of newly discovered (symbiotic) systems in the dwarf spheroidal galaxy NGC 205. The Gemini Multi-Object Spectrograph on-off band [O III] 5007 Å emission imaging highlighted several [O III] line emitters, for which optical spectra were then obtained. The detailed study of the spectra of three objects allows us to identify them as true, likely and possible symbiotic systems (SySts), the first ones discovered in this galaxy. SySt-1 is unambiguously classified as a symbiotic star, because of the presence of unique emission lines which belong only to symbiotic spectra, the well-known O VI Raman-scattered lines. SySt-2 is only possibly a SySt because the Ne VII Raman-scattered line at 4881 Å, recently identified in a well-studied Galactic symbiotic as another very conspicuous property of symbiotic, could as well be identified as N III or [Fe III]. Finally, SySt-3 is likely a symbiotic binary because in the red part of the spectrum it shows the continuum of a late giant, and forbidden lines of moderate to high ionization, like [Fe V] 4180 Å. The main source for scepticism on the symbiotic nature of the latter systems is their location in the planetary nebula region in the [O III]4363/Hγ versus [O III]5007/Hβ diagnostic diagram. It is worth mentioning that at least another two confirmed symbiotics, one of the Local Group dwarf spheroidal IC 10 and the other of the Galaxy, are also misplaced in this diagram.

  16. Flavonoids and Auxin Transport Inhibitors Rescue Symbiotic Nodulation in the Medicago truncatula Cytokinin Perception Mutant cre1.

    PubMed

    Ng, Jason Liang Pin; Hassan, Samira; Truong, Thy T; Hocart, Charles H; Laffont, Carole; Frugier, Florian; Mathesius, Ulrike

    2015-08-01

    Initiation of symbiotic nodules in legumes requires cytokinin signaling, but its mechanism of action is largely unknown. Here, we tested whether the failure to initiate nodules in the Medicago truncatula cytokinin perception mutant cre1 (cytokinin response1) is due to its altered ability to regulate auxin transport, auxin accumulation, and induction of flavonoids. We found that in the cre1 mutant, symbiotic rhizobia cannot locally alter acro- and basipetal auxin transport during nodule initiation and that these mutants show reduced auxin (indole-3-acetic acid) accumulation and auxin responses compared with the wild type. Quantification of flavonoids, which can act as endogenous auxin transport inhibitors, showed a deficiency in the induction of free naringenin, isoliquiritigenin, quercetin, and hesperetin in cre1 roots compared with wild-type roots 24 h after inoculation with rhizobia. Coinoculation of roots with rhizobia and the flavonoids naringenin, isoliquiritigenin, and kaempferol, or with the synthetic auxin transport inhibitor 2,3,5,-triiodobenzoic acid, rescued nodulation efficiency in cre1 mutants and allowed auxin transport control in response to rhizobia. Our results suggest that CRE1-dependent cytokinin signaling leads to nodule initiation through the regulation of flavonoid accumulation required for local alteration of polar auxin transport and subsequent auxin accumulation in cortical cells during the early stages of nodulation.

  17. Metaproteomics of a gutless marine worm and its symbiotic microbial community reveal unusual pathways for carbon and energy use

    SciTech Connect

    Kleiner, Manuel; Wentrop, C.; Lott, C.; Teeling, Hanno; Wetzel, Silke; Young, Jacque C; Chang, Y.; Shah, Manesh B; Verberkmoes, Nathan C; Zarzycki, Jan; Fuchs, Georg; Markert, Stephanie; Hempel, Kristina

    2012-01-01

    Low nutrient and energy availability has led to the evolution of numerous strategies for overcoming these limitations, of which symbiotic associations represent a key mechanism. Particularly striking are the associations between chemosynthetic bacteria and marine animals that thrive in nutrient-poor environments such as the deep-sea because the symbionts allow their hosts to grow on inorganic energy and carbon sources such as sulfide and CO2. Remarkably little is known about the physiological strategies that enable chemosynthetic symbioses to colonize oligotrophic environments. In this study, we used metaproteomics and metabolomics to investigate the intricate network of metabolic interactions in the chemosynthetic association between Olavius algarvensis, a gutless marine worm, and its bacterial symbionts. We propose novel pathways for coping with energy and nutrient limitation, some of which may be widespread in both free-living and symbiotic bacteria. These include (i) a pathway for symbiont assimilation of the host waste products acetate, propionate, succinate and malate, (ii) the potential use of carbon monoxide as an energy source, a substrate previously not known to play a role in marine invertebrate symbioses, (iii) the potential use of hydrogen as an energy source, (iv) the strong expression of high affinity uptake transporters, and (v) novel energy efficient steps in CO2 fixation and sulfate reduction. The high expression of proteins involved in pathways for energy and carbon uptake and conservation in the O. algarvensis symbiosis indicates that the oligotrophic nature of its environment exerted a strong selective pressure in shaping these associations.

  18. (Homo)glutathione depletion modulates host gene expression during the symbiotic interaction between Medicago truncatula and Sinorhizobium meliloti.

    PubMed

    Pucciariello, Chiara; Innocenti, Gilles; Van de Velde, Willem; Lambert, Annie; Hopkins, Julie; Clément, Mathilde; Ponchet, Michel; Pauly, Nicolas; Goormachtig, Sofie; Holsters, Marcelle; Puppo, Alain; Frendo, Pierre

    2009-11-01

    Under nitrogen-limiting conditions, legumes interact with symbiotic rhizobia to produce nitrogen-fixing root nodules. We have previously shown that glutathione and homoglutathione [(h)GSH] deficiencies impaired Medicago truncatula symbiosis efficiency, showing the importance of the low M(r) thiols during the nodulation process in the model legume M. truncatula. In this study, the plant transcriptomic response to Sinorhizobium meliloti infection under (h)GSH depletion was investigated using cDNA-amplified fragment length polymorphism analysis. Among 6,149 expression tags monitored, 181 genes displayed significant differential expression between inoculated control and inoculated (h)GSH depleted roots. Quantitative reverse transcription polymerase chain reaction analysis confirmed the changes in mRNA levels. This transcriptomic analysis shows a down-regulation of genes involved in meristem formation and a modulation of the expression of stress-related genes in (h)GSH-depleted plants. Promoter-beta-glucuronidase histochemical analysis showed that the putative MtPIP2 aquaporin might be up-regulated during nodule meristem formation and that this up-regulation is inhibited under (h)GSH depletion. (h)GSH depletion enhances the expression of salicylic acid (SA)-regulated genes after S. meliloti infection and the expression of SA-regulated genes after exogenous SA treatment. Modification of water transport and SA signaling pathway observed under (h)GSH deficiency contribute to explain how (h)GSH depletion alters the proper development of the symbiotic interaction.

  19. Flavonoids and Auxin Transport Inhibitors Rescue Symbiotic Nodulation in the Medicago truncatula Cytokinin Perception Mutant cre1

    PubMed Central

    Ng, Jason Liang Pin; Hassan, Samira; Truong, Thy T.; Hocart, Charles H.; Laffont, Carole; Frugier, Florian; Mathesius, Ulrike

    2015-01-01

    Initiation of symbiotic nodules in legumes requires cytokinin signaling, but its mechanism of action is largely unknown. Here, we tested whether the failure to initiate nodules in the Medicago truncatula cytokinin perception mutant cre1 (cytokinin response1) is due to its altered ability to regulate auxin transport, auxin accumulation, and induction of flavonoids. We found that in the cre1 mutant, symbiotic rhizobia cannot locally alter acro- and basipetal auxin transport during nodule initiation and that these mutants show reduced auxin (indole-3-acetic acid) accumulation and auxin responses compared with the wild type. Quantification of flavonoids, which can act as endogenous auxin transport inhibitors, showed a deficiency in the induction of free naringenin, isoliquiritigenin, quercetin, and hesperetin in cre1 roots compared with wild-type roots 24 h after inoculation with rhizobia. Coinoculation of roots with rhizobia and the flavonoids naringenin, isoliquiritigenin, and kaempferol, or with the synthetic auxin transport inhibitor 2,3,5,-triiodobenzoic acid, rescued nodulation efficiency in cre1 mutants and allowed auxin transport control in response to rhizobia. Our results suggest that CRE1-dependent cytokinin signaling leads to nodule initiation through the regulation of flavonoid accumulation required for local alteration of polar auxin transport and subsequent auxin accumulation in cortical cells during the early stages of nodulation. PMID:26253705

  20. Spectroscopic observations of the symbiotic binary RW Hydrae

    NASA Technical Reports Server (NTRS)

    Kenyon, Scott J.; Fernandez-Castro, Telmo

    1987-01-01

    Ultraviolet/optical spectrophotometry and infrared photometry show that the symbiotic binary RW Hya is comprised of an M giant (with L of about 1000 solar luminosities) and a compact object (with L of about 200 solar luminosities) which resembles the central star of a planetary nebula. The luminosity of the hot component is produced by a nuclear shell source which is replenished by the wind of the red giant at a rate of about 10 to the -8th solar mass/yr. Results indicate that the binary is surrounded by an H II region (of radius of about 10 AU) which gives rise to the observed emission lines and radio emission. The He(2+) and O(2+) regions are found to be confined to the immediate vicinity of the hot component.

  1. Outburst activity of the symbiotic binary AG Dra

    NASA Astrophysics Data System (ADS)

    Gális, R.; Merc, J.; Leedjärv, L.

    2017-04-01

    AG Dra regularly undergoes quiescent and active stages which consist of a series of individual outbursts repeating at about a one-year interval. After seven years of flat quiescence following the 2006-08 major outbursts, in the late spring of 2015, AG Dra begun rising again in brightness toward what appeared to be a new minor outburst. The recent outburst activity of AG Dra was definitely confirmed by a more prominent outburst in April 2016. The photometric and spectroscopic observations suggest that these outbursts are of the hot type. Such behaviour is quite unusual, because the major outbursts in the beginning of active stages are usually cool. Can we expect the major cool or minor hot outburst during the spring of 2017? AG Dra demonstrates the importance of long-term monitoring of symbiotic stars in order to disentangle the nature and mechanisms of their active stages and outbursts.

  2. On the nature of the symbiotic star BF Cygni

    NASA Technical Reports Server (NTRS)

    Mikolajewska, J.; Mikolajewski, M.; Kenyon, S. J.

    1989-01-01

    Optical and ultraviolet spectroscopy of the symbiotic binary BF Cyg obtained during 1979-1988 is discussed. This system consists of a low-mass M5 giant filling about 50 percent of its tidal volume and a hot, luminous compact object similar to the central star of a planetary nebula. The binary is embedded in an asymmetric nebula which includes a small, high-density region and an extended region of lower density. The larger nebula is formed by a slow wind ejected by the cool component and ionized by the hot star, while the more compact nebula is material expelled by the hot component in the form of a bipolar wind. The analysis indicates that disk accretion is essential to maintain the nuclear burning shell of the hot star.

  3. An update on probiotics, prebiotics and symbiotics in clinical nutrition.

    PubMed

    Olveira, Gabriel; González-Molero, Inmaculada

    2016-11-01

    The concept of prebiotics, probiotics, and symbiotics and their use in different situations of daily clinical practice related to clinical nutrition is reviewed, as well as their role in the treatment/prevention of diarrhea (acute, induced by antibiotics, secondary to radiotherapy), inflammatory bowel disease (ulcerative colitis and pouchitis), in colonic health (constipation, irritable bowel), in liver disease (steatosis and minimum encephalopathy), and in intensive care, surgical, and liver transplantation. While their effectiveness for preventing antibiotic-induced diarrhea and pouchitis in ulcerative colitis appears to be shown, additional studies are needed to establish recommendations in most clinical settings. The risk of infection associated to use of probiotics is relatively low; however, there are selected groups of patients in whom they should be used with caution (as jejunum infusion).

  4. A brightening of the symbiotic variable SY Muscae

    NASA Technical Reports Server (NTRS)

    Michalitsianos, A. G.; Feibelman, W. A.; Kafatos, M.; Wallerstein, G.

    1982-01-01

    The symbiotic variable SY Muscae has been observed with IUE in September 1980 and June 1981 and in the photographic region in May 1981. The entire ultraviolet spectrum brightened between September and June by about a factor of 5. The spectrum shows high excitation including emission from N v and high electron density, about 10-billion per cu cm as determined from various line ratios in the ultraviolet. The optical spectrum is dominated by permitted lines; even forbidden O III is very weak again indicating high density in the ionized region. The increase in ultraviolet continuum and line emission may be due to enhanced mass transfer from the cool star whose period is 623d and whose maximum was predicted to occur very close to the time of the June 1981 observations. Alternatively the hot star and much of the emitting gas could have been in eclipse in September 1980.

  5. Symbiotic Bacteria Direct Expression of an Intestinal Bactericidal Lectin

    PubMed Central

    Cash, Heather L.; Whitham, Cecilia V.; Behrendt, Cassie L.; Hooper, Lora V.

    2009-01-01

    The mammalian intestine harbors complex societies of beneficial bacteria that are maintained in the lumen with minimal penetration of mucosal surfaces. Microbial colonization of germ-free mice triggers epithelial expression of RegIIIγ, a secreted C-type lectin. RegIIIγ binds intestinal bacteria but lacks the complement recruitment domains present in other microbe-binding mammalian C-type lectins. We show that RegIIIγ and its human counterpart, HIP/PAP, are directly antimicrobial proteins that bind their bacterial targets via interactions with peptidoglycan carbohydrate. We propose that these proteins represent an evolutionarily primitive form of lectin-mediated innate immunity, and that they reveal intestinal strategies for maintaining symbiotic host-microbial relationships. PMID:16931762

  6. Symbiotic implications of type III protein secretion machinery in Rhizobium.

    PubMed

    Viprey, V; Del Greco, A; Golinowski, W; Broughton, W J; Perret, X

    1998-06-01

    The symbiotic plasmid of Rhizobium sp. NGR234 carries a cluster of genes that encodes components of a bacterial type III secretion system (TTSS). In both animal and plant pathogens, the TTSS is an essential component of pathogenicity. Here, we show that secretion of at least two proteins (y4xL and NolX) is controlled by the TTSS of NGR234 and occurs after the induction with flavonoids. Polar mutations in two TTSS genes, rhcN and the nod-box controlled regulator of transcription y4xl, block the secretion of both proteins and strongly affect the ability of NGR234 to nodulate a variety of tropical legumes including Pachyrhizus tuberosus and Tephrosia vogelii.

  7. Coral host cells acidify symbiotic algal microenvironment to promote photosynthesis

    PubMed Central

    Barott, Katie L.; Venn, Alexander A.; Perez, Sidney O.; Tambutté, Sylvie; Tresguerres, Martin

    2015-01-01

    Symbiotic dinoflagellate algae residing inside coral tissues supply the host with the majority of their energy requirements through the translocation of photosynthetically fixed carbon. The algae, in turn, rely on the host for the supply of inorganic carbon. Carbon must be concentrated as CO2 in order for photosynthesis to proceed, and here we show that the coral host plays an active role in this process. The host-derived symbiosome membrane surrounding the algae abundantly expresses vacuolar H+-ATPase (VHA), which acidifies the symbiosome space down to pH ∼4. Inhibition of VHA results in a significant decrease in average H+ activity in the symbiosome of up to 75% and a significant reduction in O2 production rate, a measure of photosynthetic activity. These results suggest that host VHA is part of a previously unidentified carbon concentrating mechanism for algal photosynthesis and provide mechanistic evidence that coral host cells can actively modulate the physiology of their symbionts. PMID:25548188

  8. Coral host cells acidify symbiotic algal microenvironment to promote photosynthesis.

    PubMed

    Barott, Katie L; Venn, Alexander A; Perez, Sidney O; Tambutté, Sylvie; Tresguerres, Martin

    2015-01-13

    Symbiotic dinoflagellate algae residing inside coral tissues supply the host with the majority of their energy requirements through the translocation of photosynthetically fixed carbon. The algae, in turn, rely on the host for the supply of inorganic carbon. Carbon must be concentrated as CO2 in order for photosynthesis to proceed, and here we show that the coral host plays an active role in this process. The host-derived symbiosome membrane surrounding the algae abundantly expresses vacuolar H(+)-ATPase (VHA), which acidifies the symbiosome space down to pH ∼ 4. Inhibition of VHA results in a significant decrease in average H(+) activity in the symbiosome of up to 75% and a significant reduction in O2 production rate, a measure of photosynthetic activity. These results suggest that host VHA is part of a previously unidentified carbon concentrating mechanism for algal photosynthesis and provide mechanistic evidence that coral host cells can actively modulate the physiology of their symbionts.

  9. Symbiotic X-ray binaries systems in the galaxy

    NASA Astrophysics Data System (ADS)

    Kuranov, A. G.; Postnov, K. A.

    2015-03-01

    The evolution of symbiotic X-ray binaries in the Galaxy is studied by the population synthesis method. We show that allowance for the nonstationarity of the regime of quasi-spherical subsonic accretion from the stellar wind of a giant onto slowly rotating neutron stars in these sources allows their observed positions on the neutron star spin period-X-ray luminosity diagramto be described in a wide range of stellar wind parameters. The derived distributions of sources in orbital periods, neutron star spin periods, and X-ray luminosities can be used to analyze the observations of Galactic sources in the range of luminosities ˜1032-1036 erg s-1 in the planned SRG/eROSITA all-sky survey.

  10. Trichotomous-noise-induced catastrophic shifts in symbiotic ecosystems

    NASA Astrophysics Data System (ADS)

    Mankin, Romi; Ainsaar, Ain; Haljas, Astrid; Reiter, Eerik

    2002-05-01

    An N-species Lotka-Volterra stochastic model of a symbiotic ecological system with the Verhulst self-regulation mechanism is considered. The effect of fluctuating environment on the carrying capacity of a population is modeled as the colored three-level Markovian (trichotomous) noise. In the framework of the mean-field theory an explicit self-consistency equation for stationary states is presented. Stability and instability conditions and colored-noise-induced discontinuous transitions (catastrophic shifts) in the model are investigated. In some cases the mean field exhibits hysteresis as a function of the noise parameters. It is shown that the occurrence of catastrophic shifts can be controlled by noise parameters, such as correlation time, amplitude, and flatness. The dependence of the critical coupling strengths on the noise parameters is found and illustrated by phase diagrams. Implications of the results on some modifications of the model are discussed.

  11. A brightening of the symbiotic variable SY Muscae

    NASA Technical Reports Server (NTRS)

    Michalitsianos, A. G.; Feibelman, W. A.; Kafatos, M.; Wallerstein, G.

    1982-01-01

    The symbiotic variable SY Muscae has been observed with IUE in September 1980 and June 1981 and in the photographic region in May 1981. The entire ultraviolet spectrum brightened between September and June by about a factor of 5. The spectrum shows high excitation including emission from N v and high electron density, about 10-billion per cu cm as determined from various line ratios in the ultraviolet. The optical spectrum is dominated by permitted lines; even forbidden O III is very weak again indicating high density in the ionized region. The increase in ultraviolet continuum and line emission may be due to enhanced mass transfer from the cool star whose period is 623d and whose maximum was predicted to occur very close to the time of the June 1981 observations. Alternatively the hot star and much of the emitting gas could have been in eclipse in September 1980.

  12. 1988 workshop on human-machine symbiotic systems proceedings

    SciTech Connect

    Parker, L.E.; Weisbin, C.R.

    1989-01-01

    This report presents the proceedings of the 1988 Workshop on Human-Machine Symbiotic Systems. Held December 5--6, 1988, in Oak Ridge, Tennessee, the workshop served as a forum for the discussion of several critical issues in human-machine symbiosis: human-machine communication, autonomous task planning and execution monitoring for heterogeneous agents, dynamic task allocation, human-machine system architecture, and machine learning via experience and human observation. The presentation of overview papers by invited keynote speakers provided a background for the breakout session discussions in these five areas. The full powers furnished by the speakers are included in the proceedings, along with written summaries of the group discussions that report session conclusions and recommendations for future work.

  13. Linear polarization of a group of symbiotic systems

    NASA Astrophysics Data System (ADS)

    Brandi, E.; García, L. G.; Piirola, V.; Scaltriti, F.; Quiroga, C.

    2000-08-01

    We report linear polarization measurements of a set of symbiotic stars, made at several epochs during the period 1994-1998. Evidence of intrinsic polarization is looked for from the wavelength dependence of the polarization degree and position angle in UBVRI bands. The results have also been analysed to search for temporal variability of polarization. Several objects have shown a polarization spectrum different from that produced by interstellar dust grains and/or polarimetric variations on time scales as short as several days or months, indicating the presence of polarization component of circumstellar origin. Based on observations taken at Complejo Astronómico El Leoncito (CASLEO), operated under an agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, the Secretaría de Ciencia y Tecnología de la Nación and the National Universities of La Plata, Córdoba and San Juan.

  14. Driving mosquito refractoriness to Plasmodium falciparum with engineered symbiotic bacteria.

    PubMed

    Wang, Sibao; Dos-Santos, André L A; Huang, Wei; Liu, Kun Connie; Oshaghi, Mohammad Ali; Wei, Ge; Agre, Peter; Jacobs-Lorena, Marcelo

    2017-09-29

    The huge burden of malaria in developing countries urgently demands the development of novel approaches to fight this deadly disease. Although engineered symbiotic bacteria have been shown to render mosquitoes resistant to the parasite, the challenge remains to effectively introduce such bacteria into mosquito populations. We describe a Serratia bacterium strain (AS1) isolated from Anopheles ovaries that stably colonizes the mosquito midgut, female ovaries, and male accessory glands and spreads rapidly throughout mosquito populations. Serratia AS1 was genetically engineered for secretion of anti-Plasmodium effector proteins, and the recombinant strains inhibit development of Plasmodium falciparum in mosquitoes. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  15. Intracellular Symbiotic Bacteria of Camponotus textor, Forel (Hymenoptera, Formicidae).

    PubMed

    Ramalho, Manuela O; Martins, Cintia; Silva, Larissa M R; Martins, Vanderlei G; Bueno, Odair C

    2017-05-01

    This study focuses on the weaver ant, Camponotus textor, Forel which occurs in some areas of the Brazilian Cerrado and Atlantic Forest, and its symbionts: Blochmannia, an obligate symbiont of Camponotus, and Wolbachia, known for causing reproductive alterations in their hosts. The main goal of this study was to investigate the presence, frequency of occurrence, and diversity of Wolbachia and Blochmannia strains in C. textor colonies. We found high infection rates (100%) and the occurrence of at least two distinct strains of Blochmannia (H_1 or H_7) in the same species. The observed haplotype variation within a single species may result from the high mutation rate of the symbiont. Similarly, the Wolbachia was found in all colonies with different rates of infections and a new strain (supergroup A) was deposited in the MLST database. The diversity found in the present study shows that there is still much to explore to understand about these symbiotic interactions.

  16. Coevolution of symbiotic mutualists and parasites in a community context.

    PubMed

    Thrall, Peter H; Hochberg, Michael E; Burdon, Jeremy J; Bever, James D

    2007-03-01

    Recent advances in our knowledge of parasitic and mutualistic associations have confirmed the central role of coevolutionary interactions in population and community ecology. Here, we discuss the potential coevolutionary interdependence of the strength and specificity of symbiotic interactions with the complexity and productivity of their environment. We predict that interactions become less beneficial with increasing environmental quality and that the association of productivity with symbiont specificity depends on the relative strengths of tradeoffs between host range and other life-history parameters. However, as biotic complexity increases, pathogen specificity is predicted to decline, whereas mutualist specificity will increase. Testing these predictions on a geographical scale would contribute significantly to the predictive science of coevolution, and to our ability to manage biological interactions embedded in increasingly fragmented landscapes.

  17. Symbiotic microorganisms: untapped resources for insect pest control.

    PubMed

    Douglas, Angela E

    2007-08-01

    Symbiotic microorganisms offer one route to meet the anticipated heightened demand for novel insect pest management strategies created by growing human populations and global climate change. Two approaches have particular potential: the disruption of microbial symbionts required by insect pests, and manipulation of microorganisms with major impacts on insect traits contributing to their pest status (e.g. capacity to vector diseases, natural enemy resistance). Specific research priorities addressed in this article include identification of molecular targets against which highly specific antagonists can be designed or discovered, and management strategies to manipulate the incidence and properties of facultative microorganisms that influence insect pest traits. Collaboration with practitioners in pest management will ensure that the research agenda is married to agricultural and public health needs.

  18. FUSE Spectroscopy of the Accreting Hot Components in Symbiotic Variables

    NASA Astrophysics Data System (ADS)

    Sion, Edward M.; Godon, Patrick; Mikolajewska, Joanna; Sabra, Bassem; Kolobow, Craig

    2017-04-01

    We have conducted a spectroscopic analysis of the far-ultraviolet archival spectra of four symbiotic variables, EG And, AE Ara, CQ Dra, and RW Hya. RW Hya and EG And have never had a recorded outburst, while CQ Dra and AE Ara have outburst histories. We analyze these systems while they are in quiescence in order to help reveal the physical properties of their hot components via comparisons of the observations with optically thick accretion disk models and non-LTE model white dwarf photospheres. We have extended the wavelength coverage down to the Lyman limit with Far Ultraviolet Spectroscopic Explorer (FUSE) spectra. We find that the hot component in RW Hya is a low-mass white dwarf with a surface temperature of 160,000 K. We reexamine whether or not the symbiotic system CQ Dra is a triple system with a red giant transferring matter to a hot component made up of a cataclysmic variable in which the white dwarf has a surface temperature as low as ˜20,000 K. The very small size of the hot component contributing to the shortest wavelengths of the FUSE spectrum of CQ Dra agrees with an optically thick and geometrically thin (˜4% of the WD surface) hot (˜120,000 K) boundary layer. Our analysis of EG And reveals that its hot component is a hot, bare, low-mass white dwarf with a surface temperature of 80,000-95,000 K, with a surface gravity {log}(g)=7.5. For AE Ara, we also find that a low-gravity ({log}(g)˜ 6), hot (T˜ {{130,000}} K) WD accounts for the hot component.

  19. A statistical anomaly indicates symbiotic origins of eukaryotic membranes.

    PubMed

    Bansal, Suneyna; Mittal, Aditya

    2015-04-01

    Compositional analyses of nucleic acids and proteins have shed light on possible origins of living cells. In this work, rigorous compositional analyses of ∼5000 plasma membrane lipid constituents of 273 species in the three life domains (archaea, eubacteria, and eukaryotes) revealed a remarkable statistical paradox, indicating symbiotic origins of eukaryotic cells involving eubacteria. For lipids common to plasma membranes of the three domains, the number of carbon atoms in eubacteria was found to be similar to that in eukaryotes. However, mutually exclusive subsets of same data show exactly the opposite-the number of carbon atoms in lipids of eukaryotes was higher than in eubacteria. This statistical paradox, called Simpson's paradox, was absent for lipids in archaea and for lipids not common to plasma membranes of the three domains. This indicates the presence of interaction(s) and/or association(s) in lipids forming plasma membranes of eubacteria and eukaryotes but not for those in archaea. Further inspection of membrane lipid structures affecting physicochemical properties of plasma membranes provides the first evidence (to our knowledge) on the symbiotic origins of eukaryotic cells based on the "third front" (i.e., lipids) in addition to the growing compositional data from nucleic acids and proteins. © 2015 Bansal and Mittal. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  20. Rhizobium phaseoli symbiotic mutants with transposon Tn5 insertions.

    PubMed Central

    Noel, K D; Sanchez, A; Fernandez, L; Leemans, J; Cevallos, M A

    1984-01-01

    Rhizobium phaseoli CFN42 DNA was mutated by random insertion of Tn5 from suicide plasmid pJB4JI to obtain independently arising strains that were defective in symbiosis with Phaseolus vulgaris but grew normally outside the plant. When these mutants were incubated with the plant, one did not initiate visible nodule tissue (Nod-), seven led to slow nodule development (Ndv), and two led to superficially normal early nodule development but lacked symbiotic nitrogenase activity (Sna-). The Nod- mutant lacked the large transmissible indigenous plasmid pCFN42d that has homology to Klebsiella pneumoniae nitrogenase (nif) genes. The other mutants had normal plasmid content. In the two Sna- mutants and one Ndv mutant, Tn5 had inserted into plasmid pCFN42d outside the region of nif homology. The insertions of the other Ndv mutants were apparently in the chromosome. They were not in plasmids detected on agarose gels, and, in contrast to insertions on indigenous plasmids, they were transmitted in crosses to wild-type strain CFN42 at the same frequency as auxotrophic markers and with the same enhancement of transmission by conjugation plasmid R68.45. In these Ndv mutants the Tn5 insertions were the same as or very closely linked to mutations causing the Ndv phenotype. However, in two mutants with Tn5 insertions on plasmid pCFN42d, an additional mutation on the same plasmid, rather than Tn5, was responsible for the Sna- or Ndv phenotype. When plasmid pJB4JI was transferred to two other R. phaseoli strains, analysis of symbiotic mutants was complicated by Tn5-containing deleted forms of pJB4JI that were stably maintained. Images PMID:6325385

  1. New-old hemoglobin-like proteins of symbiotic dinoflagellates

    PubMed Central

    Rosic, Nedeljka N; Leggat, William; Kaniewska, Paulina; Dove, Sophie; Hoegh-Guldberg, Ove

    2013-01-01

    Symbiotic dinoflagellates are unicellular photosynthetic algae that live in mutualistic symbioses with many marine organisms. Within the transcriptome of coral endosymbionts Symbiodinium sp. (type C3), we discovered the sequences of two novel and highly polymorphic hemoglobin-like genes and proposed their 3D protein structures. At the protein level, four isoforms shared between 87 and 97% sequence identity for Hb-1 and 78–99% for Hb-2, whereas between Hb-1 and Hb-2 proteins, only 15–21% sequence homology has been preserved. Phylogenetic analyses of the dinoflagellate encoding Hb sequences have revealed a separate evolutionary origin of the discovered globin genes and indicated the possibility of horizontal gene transfer. Transcriptional regulation of the Hb-like genes was studied in the reef-building coral Acropora aspera exposed to elevated temperatures (6–7°C above average sea temperature) over a 24-h period and a 72-h period, as well as to nutrient stress. Exposure to elevated temperatures resulted in an increased Hb-1 gene expression of 31% after 72 h only, whereas transcript abundance of the Hb-2 gene was enhanced by up to 59% by both 1-day and 3-day thermal stress conditions. Nutrient stress also increased gene expression of Hb-2 gene by 70%. Our findings describe the differential expression patterns of two novel Hb genes from symbiotic dinoflagellates and their polymorphic nature. Furthermore, the inducible nature of Hb-2 gene by both thermal and nutrient stressors indicates a prospective role of this form of hemoglobin in the initial coral–algal responses to changes in environmental conditions. This novel hemoglobin has potential use as a stress biomarker. PMID:23610627

  2. Evolution of symbiotic organs and endosymbionts in lygaeid stinkbugs

    PubMed Central

    Matsuura, Yu; Kikuchi, Yoshitomo; Hosokawa, Takahiro; Koga, Ryuichi; Meng, Xian-Ying; Kamagata, Yoichi; Nikoh, Naruo; Fukatsu, Takema

    2012-01-01

    We investigated seed bugs of the genus Nysius (Insecta: Hemiptera: Lygaeidae) for their symbiotic bacteria. From all the samples representing 4 species, 18 populations and 281 individuals, specific bacterial 16S rRNA gene sequences were consistently identified, which formed a distinct clade in the Gammaproteobacteria. In situ hybridization showed that the bacterium was endocellularly localized in a pair of large bacteriomes that were amorphous in shape, deep red in color, and in association with gonads. In the ovary of adult females, the endosymbiont was also localized in the ‘infection zone' in the middle of each germarium and in the ‘symbiont ball' at the anterior pole of each oocyte, indicating vertical transmission of the endosymbiont through the ovarial passage. Phylogenetic analyses based on bacterial 16S rRNA, groEL and gyrB genes consistently supported a coherent monophyly of the Nysius endosymbionts. The possibility of a sister relationship to ‘Candidatus Kleidoceria schneideri', the bacteriome-associated endosymbiont of a lygaeid bug Kleidocerys resedae, was statistically rejected, indicating independent evolutionary origins of the endosymbionts in the Lygaeidae. The endosymbiont genes consistently exhibited AT-biased nucleotide compositions and accelerated rates of molecular evolution, and the endosymbiont genome was only 0.6 Mb in size. The endosymbiont phylogeny was congruent with the host insect phylogeny, suggesting strict vertical transmission and host–symbiont co-speciation over evolutionary time. Based on these results, we discuss the evolution of bacteriomes and endosymbionts in the Heteroptera, most members of which are associated with gut symbiotic bacteria. The designation ‘Candidatus Schneideria nysicola' is proposed for the endosymbiont clade. PMID:21814289

  3. The Recent Evolution of a Symbiotic Ion Channel in the Legume Family Altered Ion Conductance and Improved Functionality in Calcium Signaling[C][W

    PubMed Central

    Venkateshwaran, Muthusubramanian; Cosme, Ana; Han, Lu; Banba, Mari; Satyshur, Kenneth A.; Schleiff, Enrico; Parniske, Martin; Imaizumi-Anraku, Haruko; Ané, Jean-Michel

    2012-01-01

    Arbuscular mycorrhiza and the rhizobia-legume symbiosis are two major root endosymbioses that facilitate plant nutrition. In Lotus japonicus, two symbiotic cation channels, CASTOR and POLLUX, are indispensable for the induction of nuclear calcium spiking, one of the earliest plant responses to symbiotic partner recognition. During recent evolution, a single amino acid substitution in DOES NOT MAKE INFECTIONS1 (DMI1), the POLLUX putative ortholog in the closely related Medicago truncatula, rendered the channel solo sufficient for symbiosis; castor, pollux, and castor pollux double mutants of L. japonicus were rescued by DMI1 alone, while both Lj-CASTOR and Lj-POLLUX were required for rescuing a dmi1 mutant of M. truncatula. Experimental replacement of the critical serine by an alanine in the selectivity filter of Lj-POLLUX conferred a symbiotic performance indistinguishable from DMI1. Electrophysiological characterization of DMI1 and Lj-CASTOR (wild-type and mutants) by planar lipid bilayer experiments combined with calcium imaging in Human Embryonic Kidney-293 cells expressing DMI1 (the wild type and mutants) suggest that the serine-to-alanine substitution conferred reduced conductance with a long open state to DMI1 and improved its efficiency in mediating calcium oscillations. We propose that this single amino acid replacement in the selectivity filter made DMI1 solo sufficient for symbiosis, thus explaining the selective advantage of this allele at the mechanistic level. PMID:22706284

  4. The recent evolution of a symbiotic ion channel in the legume family altered ion conductance and improved functionality in calcium signaling.

    PubMed

    Venkateshwaran, Muthusubramanian; Cosme, Ana; Han, Lu; Banba, Mari; Satyshur, Kenneth A; Schleiff, Enrico; Parniske, Martin; Imaizumi-Anraku, Haruko; Ané, Jean-Michel

    2012-06-01

    Arbuscular mycorrhiza and the rhizobia-legume symbiosis are two major root endosymbioses that facilitate plant nutrition. In Lotus japonicus, two symbiotic cation channels, CASTOR and POLLUX, are indispensable for the induction of nuclear calcium spiking, one of the earliest plant responses to symbiotic partner recognition. During recent evolution, a single amino acid substitution in DOES NOT MAKE INFECTIONS1 (DMI1), the POLLUX putative ortholog in the closely related Medicago truncatula, rendered the channel solo sufficient for symbiosis; castor, pollux, and castor pollux double mutants of L. japonicus were rescued by DMI1 alone, while both Lj-CASTOR and Lj-POLLUX were required for rescuing a dmi1 mutant of M. truncatula. Experimental replacement of the critical serine by an alanine in the selectivity filter of Lj-POLLUX conferred a symbiotic performance indistinguishable from DMI1. Electrophysiological characterization of DMI1 and Lj-CASTOR (wild-type and mutants) by planar lipid bilayer experiments combined with calcium imaging in Human Embryonic Kidney-293 cells expressing DMI1 (the wild type and mutants) suggest that the serine-to-alanine substitution conferred reduced conductance with a long open state to DMI1 and improved its efficiency in mediating calcium oscillations. We propose that this single amino acid replacement in the selectivity filter made DMI1 solo sufficient for symbiosis, thus explaining the selective advantage of this allele at the mechanistic level.

  5. Transcriptional responses toward diffusible signals from symbiotic microbes reveal MtNFP- and MtDMI3-dependent reprogramming of host gene expression by arbuscular mycorrhizal fungal lipochitooligosaccharides.

    PubMed

    Czaja, Lisa F; Hogekamp, Claudia; Lamm, Patrick; Maillet, Fabienne; Martinez, Eduardo Andres; Samain, Eric; Dénarié, Jean; Küster, Helge; Hohnjec, Natalija

    2012-08-01

    The formation of root nodules and arbuscular mycorrhizal (AM) roots is controlled by a common signaling pathway including the calcium/calmodulin-dependent kinase Doesn't Make Infection3 (DMI3). While nodule initiation by lipochitooligosaccharide (LCO) Nod factors is well characterized, diffusible AM fungal signals were only recently identified as sulfated and nonsulfated LCOs. Irrespective of different outcomes, the perception of symbiotic LCOs in Medicago truncatula is mediated by the LysM receptor kinase M. truncatula Nod factor perception (MtNFP). To shed light on transcriptional responses toward symbiotic LCOs and their dependence on MtNFP and Ca(2+) signaling, we performed genome-wide expression studies of wild-type, Nod-factor-perception mutant1, and dmi3 mutant roots challenged with Myc- and Nod-LCOs. We show that Myc-LCOs lead to transient, quick responses in the wild type, whereas Nod-LCOs require prolonged incubation for maximal expression activation. While Nod-LCOs are most efficient for an induction of persistent transcriptional changes, sulfated Myc-LCOs are less active, and nonsulfated Myc-LCOs display the lowest capacity to activate and sustain expression. Although all symbiotic LCOs up-regulated a common set of genes, discrete subsets were induced by individual LCOs, suggesting common and specific functions for these in presymbiotic signaling. Surprisingly, even sulfated fungal Myc-LCOs and Sinorhizobium meliloti Nod-LCOs, having very similar structures, each elicited discrete subsets of genes, while a mixture of both Myc-LCOs activated responses deviating from those induced by single treatments. Focusing on the precontact phase, we identified signaling-related and transcription factor genes specifically up-regulated by Myc-LCOs. Comparative gene expression studies in symbiotic mutants demonstrated that transcriptional reprogramming by AM fungal LCOs strictly depends on MtNFP and largely requires MtDMI3.

  6. Construction of an artificial symbiotic community using a Chlorella–symbiont association as a model

    PubMed Central

    Imase, Masato; Watanabe, Keiji; Aoyagi, Hideki; Tanaka, Hideo

    2008-01-01

    Chlorella sorokiniana IAM C-212 produces a polysaccharide gel, termed a sheath, under photoautotrophic conditions. The C. sorokiniana sheath is a suitable habitat for several symbiotic microorganisms because it ensures close proximity between the C. sorokiniana and symbionts. In this study, we established a method for increasing the volume of the sheath produced by C. sorokiniana, and proposed a method for constructing artificial communities of Chlorella and symbiotic microorganisms. The C. sorokiniana sheath was increased by addition of calcium chloride solution. The sheath resulted in coflocculation of C. sorokiniana and the associated symbiotic bacteria, thus strengthening the bacterial–Chlorella symbiotic association. An application of this technique was demonstrated by constructing a complex of C. sorokiniana and a propionate-degrading bacterium (PDS1). Although propionate inhibited the growth of axenic C. sorokiniana, the C. sorokiniana–PDS1 complex showed good growth in a medium containing a high concentration of propionate. PMID:18269632

  7. The Symbiotic Relationship of Science and Technology in the 21st Century.

    ERIC Educational Resources Information Center

    Wiens, A. Emerson

    1999-01-01

    There are many examples in which science and technology complement each other. This is especially evident in biotechnology and genetic engineering. This symbiotic relationship is foundational to the technological culture of contemporary society. (SK)

  8. Life in cellulose houses: symbiotic bacterial biosynthesis of ascidian drugs and drug leads.

    PubMed

    Schmidt, Eric W; Donia, Mohamed S

    2010-12-01

    Ascidians (tunicates; sea squirts) are sources of diverse, bioactive natural products, one of which is an approved drug and many of which are potent drug leads. It has been shown that symbiotic bacteria living with ascidians produce some of the bioactive compounds isolated from whole animals, and indirect evidence strongly implicates symbiotic bacteria in the synthesis of many others. However, for the majority the producing organism has not been identified. In cases where a symbiotic origin has been definitively assigned, the resulting data lead to improved paths to drug discovery and development from marine animals. This review traces evidence for symbiotic production where such evidence exists and describes the strengths and limitations of that evidence. Copyright © 2010 Elsevier Ltd. All rights reserved.

  9. TIDALLY ENHANCED STELLAR WIND: A WAY TO MAKE THE SYMBIOTIC CHANNEL TO TYPE Ia SUPERNOVA VIABLE

    SciTech Connect

    Chen, X.; Han, Z.

    2011-07-10

    In the symbiotic (or WD+RG) channel of the single-degenerate scenario for type Ia supernovae (SNe Ia), the explosions occur a relatively long time after star formation. The birthrate from this channel would be too low to account for all observed SNe Ia were it not for some mechanism to enhance the rate of accretion on to the white dwarf. A tidally enhanced stellar wind, of the type which has been postulated to explain many phenomena related to giant star evolution in binary systems, can do this. Compared to mass stripping, this model extends the space of SNe Ia progenitors to longer orbital periods and hence increases the birthrate to about 0.0069 yr{sup -1} for the symbiotic channel. Two symbiotic stars, T CrB and RS Oph, considered to be the most likely progenitors of SNe Ia through the symbiotic channel, are well inside the period-companion mass space predicted by our models.

  10. Differential gene expression during pre-symbiotic interaction between Tuber borchii Vittad. and Tilia americana L.

    PubMed

    Menotta, M; Amicucci, A; Sisti, D; Gioacchini, A M; Stocchi, V

    2004-09-01

    Ectomycorrhizal formation is a highly regulated process involving the molecular reorganization of both partners during symbiosis. An analogous molecular process also occurs during the pre-symbiotic phase, when the partners exchange molecular signals in order to position and prepare both organisms for the establishment of symbiosis. To gain insight into genetic reorganization in Tuber borchii during its interaction with its symbiotic partner Tilia americana, we set up a culture system in which the mycelium interacts with the plant, even though there is no actual physical contact between the two organisms. The selected strategies, suppressive subtractive hybridisation and reverse Northern blots, allowed us to identify, for the first time, 58 cDNA clones differentially expressed in the pre-symbiotic phase. Sequence analysis of the expressed sequence tags showed that the expressed genes are involved in several biochemical pathways: secretion and apical growth, cellular detoxification, general metabolism and both mutualistic and symbiotic features.

  11. Deciphering The Hot Components in Symbiotic Variables: A Brave New Frontier

    NASA Astrophysics Data System (ADS)

    Sion, Edward

    We propose to investigate the physical properties of the hot components of symbiotic variable stars. They are binary star systems consisting of a red giant and a white dwarf (WD) orbiting each other close enough to interact. Material from the outflowing stellar wind of the red giant accretes onto the white dwarf, and an accretion disk may or may not form. Much of the outflowing red giant wind material forms a large nebula around the binary that is partially ionized by radiation from the accreting WD and from thermonuclear burning at its surface. The exact nature of the hot component, the efficiency of such wind-fed accretion, the rate of accretion onto the WD, whether accretion disks are even present, and why the hot components are so much hotter than their cataclysmic variable cousins, all remain poorly know. All previous attempts to determine WD temperatures, luminosities and accretion rates relied upon the modified Zanstra method and crude black body fitting. To deepen our understanding of the hot components, we propose to apply synthetic spectra for high gravity stars and accretion disks generated from state-of-the-art computer codes to the far ultraviolet archival spectra of 40 symbiotic stars, obtained with the International Ultraviolet Explorer (IUE) and Far Ultraviolet Spectroscopic Explorer (FUSE) spacecrafts. Since the WD is the most common end-product of stellar evolution ( > 95% of all the stars in the Galaxy evolve into white dwarfs), and the accretion disk whether from wind- fed accretion or Roche lobe overflow, is the most common universal structure resulting from mass transfer with angular momentum, and since both can be directly viewed in CVs in the ultraviolet (UV), an understanding of the consequences of accretion in these systems is the first step in a global understanding of accretion in other systems throughout the universe. These include protostellar objects, X-ray binaries (containing neutron star and black hole accretors), active galactic

  12. A Medicago truncatula NADPH oxidase is involved in symbiotic nodule functioning

    PubMed Central

    Marino, Daniel; Andrio, Emilie; Danchin, Etienne G J; Oger, Elodie; Gucciardo, Sébastien; Lambert, Annie; Puppo, Alain; Pauly, Nicolas

    2011-01-01

    Summary The plant plasma membrane-localized NADPH oxidases, known as respiratory burst oxidase homologues (RBOHs), appear to play crucial roles in plant growth and development. They are involved in important processes, such as root hair growth, plant defence reactions and abscisic acid signalling.Using sequence similarity searches, we identified seven putative RBOH-encoding genes in the Medicago truncatula genome. A phylogenetic reconstruction showed that Rboh gene duplications occurred in legume species. We analysed the expression of these MtRboh genes in different M. truncatula tissues: one of them, MtRbohA, was significantly up-regulated in Sinorhizobium meliloti-induced symbiotic nodules.MtRbohA expression appeared to be restricted to the nitrogen-fixing zone of the functional nodule. Moreover, using S. meliloti bacA and nifH mutants unable to form efficient nodules, a strong link between nodule nitrogen fixation and MtRbohA up-regulation was shown. MtRbohA expression was largely enhanced under hypoxic conditions. Specific RNA interference for MtRbohA provoked a decrease in the nodule nitrogen fixation activity and the modulation of genes encoding the microsymbiont nitrogenase.These results suggest that hypoxia, prevailing in the nodule-fixing zone, may drive the stimulation of MtRbohA expression, which would, in turn, lead to the regulation of nodule functioning. PMID:21155825

  13. The value of biodiversity in legume symbiotic nitrogen fixation and nodulation for biofuel and food production.

    PubMed

    Gresshoff, Peter M; Hayashi, Satomi; Biswas, Bandana; Mirzaei, Saeid; Indrasumunar, Arief; Reid, Dugald; Samuel, Sharon; Tollenaere, Alina; van Hameren, Bethany; Hastwell, April; Scott, Paul; Ferguson, Brett J

    2015-01-01

    Much of modern agriculture is based on immense populations of genetically identical or near-identical varieties, called cultivars. However, advancement of knowledge, and thus experimental utility, is found through biodiversity, whether naturally-found or induced by the experimenter. Globally we are confronted by ever-growing food and energy challenges. Here we demonstrate how such biodiversity from the food legume crop soybean (Glycine max L. Merr) and the bioenergy legume tree Pongamia (Millettia) pinnata is a great value. Legume plants are diverse and are represented by over 18,000 species on this planet. Some, such as soybean, pea and medics are used as food and animal feed crops. Others serve as ornamental (e.g., wisteria), timber (e.g., acacia/wattle) or biofuel (e.g., Pongamia pinnata) resources. Most legumes develop root organs (nodules) after microsymbiont induction that serve as their habitat for biological nitrogen fixation. Through this, nitrogen fertiliser demand is reduced by the efficient symbiosis between soil Rhizobium-type bacteria and the appropriate legume partner. Mechanistic research into the genetics, biochemistry and physiology of legumes is thus strategically essential for future global agriculture. Here we demonstrate how molecular plant science analysis of the genetics of an established food crop (soybean) and an emerging biofuel P. pinnata feedstock contributes to their utility by sustainable production aided by symbiotic nitrogen fixation.

  14. Genetic diversity and symbiotic compatibility among rhizobial strains and Desmodium incanum and Lotus spp. plants.

    PubMed

    Granada, Camille E; Strochein, Marcos; Vargas, Luciano K; Bruxel, Manuela; de Sá, Enilson Luiz Saccol; Passaglia, Luciane M P

    2014-06-01

    This work aimed to evaluate the symbiotic compatibility and nodulation efficiency of rhizobia isolated from Desmodium incanum, Lotus corniculatus, L. subbiflorus, L. uliginosus and L. glaber plants by cross-inoculation. Twelve reference strains and 21 native isolates of rhizobia were genetically analyzed by the BOX-PCR technique, which showed a high genetic diversity among the rhizobia studied. The isolates were also characterized based on their production of indolic compounds and siderophores, as well as on their tolerance to salinity. Fifteen of the 33 rhizobia analyzed were able to produce indolic compounds, whereas 13 produced siderophores. All the tested rhizobia were sensitive to high salinity, although some were able to grow in solutions of up to 2% NaCl. Most of the native rhizobia isolated from L. uliginosus were able to induce nodulation in all plant species studied. In a greenhouse experiment using both D. incanum and L. corniculatus plants, the rhizobia isolate UFRGS Lu2 promoted the greatest plant growth. The results demonstrate that there are native rhizobia in the soils of southern Brazil that have low host specificity and are able to induce nodulation and form active nodules in several plant species.

  15. Discovery of symbiotic nitrogen fixation and chemoautotrophy in cold-water corals.

    PubMed

    Middelburg, Jack J; Mueller, Christina E; Veuger, Bart; Larsson, Ann I; Form, Armin; van Oevelen, Dick

    2015-12-08

    Cold-water corals (CWC) are widely distributed around the world forming extensive reefs at par with tropical coral reefs. They are hotspots of biodiversity and organic matter processing in the world's deep oceans. Living in the dark they lack photosynthetic symbionts and are therefore considered to depend entirely on the limited flux of organic resources from the surface ocean. While symbiotic relations in tropical corals are known to be key to their survival in oligotrophic conditions, the full metabolic capacity of CWC has yet to be revealed. Here we report isotope tracer evidence for efficient nitrogen recycling, including nitrogen assimilation, regeneration, nitrification and denitrification. Moreover, we also discovered chemoautotrophy and nitrogen fixation in CWC and transfer of fixed nitrogen and inorganic carbon into bulk coral tissue and tissue compounds (fatty acids and amino acids). This unrecognized yet versatile metabolic machinery of CWC conserves precious limiting resources and provides access to new nitrogen and organic carbon resources that may be essential for CWC to survive in the resource-depleted dark ocean.

  16. Discovery of symbiotic nitrogen fixation and chemoautotrophy in cold-water corals

    PubMed Central

    Middelburg, Jack J.; Mueller, Christina E.; Veuger, Bart; Larsson, Ann I.; Form, Armin; Oevelen, Dick van

    2015-01-01

    Cold-water corals (CWC) are widely distributed around the world forming extensive reefs at par with tropical coral reefs. They are hotspots of biodiversity and organic matter processing in the world’s deep oceans. Living in the dark they lack photosynthetic symbionts and are therefore considered to depend entirely on the limited flux of organic resources from the surface ocean. While symbiotic relations in tropical corals are known to be key to their survival in oligotrophic conditions, the full metabolic capacity of CWC has yet to be revealed. Here we report isotope tracer evidence for efficient nitrogen recycling, including nitrogen assimilation, regeneration, nitrification and denitrification. Moreover, we also discovered chemoautotrophy and nitrogen fixation in CWC and transfer of fixed nitrogen and inorganic carbon into bulk coral tissue and tissue compounds (fatty acids and amino acids). This unrecognized yet versatile metabolic machinery of CWC conserves precious limiting resources and provides access to new nitrogen and organic carbon resources that may be essential for CWC to survive in the resource-depleted dark ocean. PMID:26644069

  17. Evidence for an Inorganic Carbon-Concentrating Mechanism in the Symbiotic Dinoflagellate Symbiodinium sp.1

    PubMed Central

    Leggat, William; Badger, Murray R.; Yellowlees, David

    1999-01-01

    The presence of a carbon-concentrating mechanism in the symbiotic dinoflagellate Symbiodinium sp. was investigated. Its existence was postulated to explain how these algae fix inorganic carbon (Ci) efficiently despite the presence of a form II Rubisco. When the dinoflagellates were isolated from their host, the giant clam (Tridacna gigas), CO2 uptake was found to support the majority of net photosynthesis (45%–80%) at pH 8.0; however, 2 d after isolation this decreased to 5% to 65%, with HCO3− uptake supporting 35% to 95% of net photosynthesis. Measurements of intracellular Ci concentrations showed that levels inside the cell were between two and seven times what would be expected from passive diffusion of Ci into the cell. Symbiodinium also exhibits a distinct light-activated intracellular carbonic anhydrase activity. This, coupled with elevated intracellular Ci and the ability to utilize both CO2 and HCO3− from the medium, suggests that Symbiodinium sp. does possess a carbon-concentrating mechanism. However, intracellular Ci levels are not as large as might be expected of an alga utilizing a form II Rubisco with a poor affinity for CO2. PMID:10594111

  18. Three-dimensional hydrodynamical models of wind and outburst-related accretion in symbiotic systems

    NASA Astrophysics Data System (ADS)

    de Val-Borro, M.; Karovska, M.; Sasselov, D. D.; Stone, J. M.

    2017-07-01

    Gravitationally focused wind accretion in binary systems consisting of an evolved star with a gaseous envelope and a compact accreting companion is a possible mechanism to explain mass transfer in symbiotic binaries. We study the mass accretion around the secondary caused by the strong wind from the primary late-type component using global three-dimensional hydrodynamic numerical simulations during quiescence and outburst stages. In particular, the dependence of the mass accretion rate on the mass-loss rate, wind parameters and phases of wind outburst development is considered. For a typical wind from an asymptotic giant branch star with a mass-loss rate of 10-6 M⊙ yr-1 and wind speeds of 20-50 km s-1, the mass transfer through a focused wind results in efficient infall on to the secondary. Accretion rates on to the secondary of 5-20 per cent of the mass-loss from the primary are obtained during quiescence and outburst periods where the wind velocity and mass-loss rates are varied, about 20-50 per cent larger than in the standard Bondi-Hoyle-Lyttleton approximation. This mechanism could be an important method for explaining observed accretion luminosities and periodic modulations in the accretion rates for a broad range of interacting binary systems.

  19. Genetic diversity and symbiotic compatibility among rhizobial strains and Desmodium incanum and Lotus spp. plants

    PubMed Central

    Granada, Camille E.; Strochein, Marcos; Vargas, Luciano K.; Bruxel, Manuela; de Sá, Enilson Luiz Saccol; Passaglia, Luciane M.P.

    2014-01-01

    This work aimed to evaluate the symbiotic compatibility and nodulation efficiency of rhizobia isolated from Desmodium incanum, Lotus corniculatus, L. subbiflorus, L. uliginosus and L. glaber plants by cross-inoculation. Twelve reference strains and 21 native isolates of rhizobia were genetically analyzed by the BOX-PCR technique, which showed a high genetic diversity among the rhizobia studied. The isolates were also characterized based on their production of indolic compounds and siderophores, as well as on their tolerance to salinity. Fifteen of the 33 rhizobia analyzed were able to produce indolic compounds, whereas 13 produced siderophores. All the tested rhizobia were sensitive to high salinity, although some were able to grow in solutions of up to 2% NaCl. Most of the native rhizobia isolated from L. uliginosus were able to induce nodulation in all plant species studied. In a greenhouse experiment using both D. incanum and L. corniculatus plants, the rhizobia isolate UFRGS Lu2 promoted the greatest plant growth. The results demonstrate that there are native rhizobia in the soils of southern Brazil that have low host specificity and are able to induce nodulation and form active nodules in several plant species. PMID:25071405

  20. Intracellular pH and its response to CO2-driven seawater acidification in symbiotic versus non-symbiotic coral cells.

    PubMed

    Gibbin, Emma M; Putnam, Hollie M; Davy, Simon K; Gates, Ruth D

    2014-06-01

    Regulating intracellular pH (pHi) is critical for optimising the metabolic activity of corals, yet the mechanisms involved in pH regulation and the buffering capacity within coral cells are not well understood. Our study investigated how the presence of symbiotic dinoflagellates affects the response of pHi to PCO2-driven seawater acidification in cells isolated from Pocillopora damicornis. Using the fluorescent dye BCECF-AM, in conjunction with confocal microscopy, we simultaneously characterised the pHi response in host coral cells and their dinoflagellate symbionts, in symbiotic and non-symbiotic states under saturating light, with and without the photosynthetic inhibitor DCMU. Each treatment was run under control (pH 7.8) and CO2-acidified seawater conditions (decreasing pH from 7.8 to 6.8). After 105 min of CO2 addition, by which time the external pH (pHe) had declined to 6.8, the dinoflagellate symbionts had increased their pHi by 0.5 pH units above control levels when in the absence of DCMU. In contrast, in both symbiotic and non-symbiotic host coral cells, 15 min of CO2 addition (0.2 pH unit drop in pHe) led to cytoplasmic acidosis equivalent to 0.3-0.4 pH units irrespective of whether DCMU was present. Despite further seawater acidification over the duration of the experiment, the pHi of non-symbiotic coral cells did not change, though in host cells containing a symbiont cell the pHi recovered to control levels when photsynthesis was not inhibited. This recovery was negated when cells were incubated with DCMU. Our results reveal that photosynthetic activity of the endosymbiont is tightly coupled with the ability of the host cell to recover from cellular acidosis after exposure to high CO2/low pH.

  1. Optical Manipulation of Symbiotic Chlorella in Paramecium Bursaria Using a Fiber Axicon Microlens

    NASA Astrophysics Data System (ADS)

    Taguchi, K.; Hirota, S.; Nakayama, H.; Kunugihara, D.; Mihara, Y.

    2012-03-01

    In this paper, chemically etched axicon fiber was proposed for laser trapping of symbiotic chlorella from paramecium bursaria. We fabricated axicon micro lenses on a single-mode bare optical fiber by selective chemical etching technique. The laser beam from fiber axicon microlens was strongly focused and optical forces were sufficient to move a symbiotic chlorella. From experimental results, it was found that our proposed fiber axicon microlens was a promising tool for cell trapping without physical contact.

  2. Swift observations of the 2015 outburst of AG Peg - from slow nova to classical symbiotic outburst

    NASA Astrophysics Data System (ADS)

    Ramsay, Gavin; Sokoloski, J. L.; Luna, G. J. M.; Nuñez, N. E.

    2016-10-01

    Symbiotic stars often contain white dwarfs with quasi-steady shell burning on their surfaces. However, in most symbiotics, the origin of this burning is unclear. In symbiotic slow novae, however, it is linked to a past thermonuclear runaway. In 2015 June, the symbiotic slow nova AG Peg was seen in only its second optical outburst since 1850. This recent outburst was of much shorter duration and lower amplitude than the earlier eruption, and it contained multiple peaks - like outbursts in classical symbiotic stars such as Z And. We report Swift X-ray and UV observations of AG Peg made between 2015 June and 2016 January. The X-ray flux was markedly variable on a time-scale of days, particularly during four days near optical maximum, when the X-rays became bright and soft. This strong X-ray variability continued for another month, after which the X-rays hardened as the optical flux declined. The UV flux was high throughout the outburst, consistent with quasi-steady shell burning on the white dwarf. Given that accretion discs around white dwarfs with shell burning do not generally produce detectable X-rays (due to Compton-cooling of the boundary layer), the X-rays probably originated via shocks in the ejecta. As the X-ray photoelectric absorption did not vary significantly, the X-ray variability may directly link to the properties of the shocked material. AG Peg's transition from a slow symbiotic nova (which drove the 1850 outburst) to a classical symbiotic star suggests that shell burning in at least some symbiotic stars is residual burning from prior novae.

  3. Three replicons of Rhizobium sp. Strain NGR234 harbor symbiotic gene sequences.

    PubMed

    Flores, M; Mavingui, P; Girard, L; Perret, X; Broughton, W J; Martínez-Romero, E; Dávila, G; Palacios, R

    1998-11-01

    Rhizobium sp. strain NGR234 contains three replicons: the symbiotic plasmid or pNGR234a, a megaplasmid (pNGR234b), and the chromosome. Symbiotic gene sequences not present in pNGR234a were analyzed by hybridization. DNA sequences homologous to the genes fixLJKNOPQGHIS were found on the chromosome, while sequences homologous to nodPQ and exoBDFLK were found on pNGR234b.

  4. Three Replicons of Rhizobium sp. Strain NGR234 Harbor Symbiotic Gene Sequences

    PubMed Central

    Flores, Margarita; Mavingui, Patrick; Girard, Lourdes; Perret, Xavier; Broughton, William J.; Martínez-Romero, Esperanza; Dávila, Guillermo; Palacios, Rafael

    1998-01-01

    Rhizobium sp. strain NGR234 contains three replicons: the symbiotic plasmid or pNGR234a, a megaplasmid (pNGR234b), and the chromosome. Symbiotic gene sequences not present in pNGR234a were analyzed by hybridization. DNA sequences homologous to the genes fixLJKNOPQGHIS were found on the chromosome, while sequences homologous to nodPQ and exoBDFLK were found on pNGR234b. PMID:9811668

  5. Diversification of DNA Sequences in the Symbiotic Genome of Rhizobium etli

    PubMed Central

    Flores, Margarita; Morales, Lucia; Avila, Agustín; González, Víctor; Bustos, Patricia; García, Delfino; Mora, Yolanda; Guo, Xianwu; Collado-Vides, Julio; Piñero, Daniel; Dávila, Guillermo; Mora, Jaime; Palacios, Rafael

    2005-01-01

    Bacteria of the genus Rhizobium and related genera establish nitrogen-fixing symbioses with the roots of leguminous plants. The genetic elements that participate in the symbiotic process are usually compartmentalized in the genome, either as independent replicons (symbiotic plasmids) or as symbiotic regions or islands in the chromosome. The complete nucleotide sequence of the symbiotic plasmid of Rhizobium etli model strain CFN42, symbiont of the common bean plant, has been reported. To better understand the basis of DNA sequence diversification of this symbiotic compartment, we analyzed the distribution of single-nucleotide polymorphisms in homologous regions from different Rhizobium etli strains. The distribution of polymorphisms is highly asymmetric in each of the different strains, alternating regions containing very few changes with regions harboring an elevated number of substitutions. The regions showing high polymorphism do not correspond with discrete genetic elements and are not the same in the different strains, indicating that they are not hypervariable regions of functional genes. Most interesting, some highly polymorphic regions share exactly the same nucleotide substitutions in more than one strain. Furthermore, in different regions of the symbiotic compartment, different sets of strains share the same substitutions. The data indicate that the majority of nucleotide substitutions are spread in the population by recombination and that the contribution of new mutations to polymorphism is relatively low. We propose that the horizontal transfer of homologous DNA segments among closely related organisms is a major source of genomic diversification. PMID:16237002

  6. Characterization of glutathione peroxidase diversity in the symbiotic sea anemone Anemonia viridis.

    PubMed

    Pey, Alexis; Zamoum, Thamilla; Christen, Richard; Merle, Pierre-Laurent; Furla, Paola

    2017-01-01

    Cnidarians living in symbiosis with photosynthetic dinoflagellates (commonly named zooxanthellae) are exposed to high concentrations of reactive oxygen species (ROS) upon illumination. To quench ROS production, both the cnidarian host and zooxanthellae express a full suite of antioxidant enzymes. Studying antioxidative balance is therefore crucial to understanding how symbiotic cnidarians cope with ROS production. We characterized glutathione peroxidases (GPx) in the symbiotic cnidarian Anemonia viridis by analysis of their isoform diversity, their activity distribution in the three cellular compartments (ectoderm, endoderm and zooxanthellae) and their involvement in the response to thermal stress. We identified a GPx repertoire through a phylogenetic analysis showing 7 GPx transcripts belonging to the A. viridis host and 4 GPx transcripts strongly related to Symbiodinium sp. The biochemical approach, used for the first time with a cnidarian species, allowed the identification of GPx activity in the three cellular compartments and in the animal mitochondrial fraction, and revealed a high GPx electrophoretic diversity. The symbiotic lifestyle of zooxanthellae requires more GPx activity and diversity than that of free-living species. Heat stress induced no modification of GPx activities. We highlight a high GPx diversity in A. viridis tissues by genomic and biochemical approaches. GPx activities represent an overall constitutive enzymatic pattern inherent to symbiotic lifestyle adaptation. This work allows the characterization of the GPx family in a symbiotic cnidarian and establishes a foundation for future studies of GPx in symbiotic cnidarians.

  7. Symbiotic bacteria contribute to increasing the population size of a freshwater crustacean, Daphnia magna.

    PubMed

    Peerakietkhajorn, Saranya; Tsukada, Koji; Kato, Yasuhiko; Matsuura, Tomoaki; Watanabe, Hajime

    2015-04-01

    The filter-feeding crustacean Daphnia is a key organism in freshwater ecosystems. Here, we report the effect of symbiotic bacteria on ecologically important life history traits, such as population dynamics and longevity, in Daphnia magna. By disinfection of the daphniid embryos with glutaraldehyde, aposymbiotic daphniids were prepared and cultured under bacteria-free conditions. Removal of bacteria from the daphniids was monitored by quantitative polymerase chain reaction for bacterial 16S rRNA gene. The population of aposymbiotic daphniids was reduced 10-folds compared with that of the control daphniids. Importantly, re-infection with symbiotic bacteria caused daphniids to regain bacteria and increase their fecundity to the level of the control daphniids, suggesting that symbiotic bacteria regulate Daphnia fecundity. To identify the species of symbiotic bacteria, 16S rRNA genes of bacteria in daphniids were sequenced. This revealed that 50% of sequences belonged to the Limnohabitans sp. of the Betaproteobacteria class and that the diversity of bacterial taxa was relatively low. These results suggested that symbiotic bacteria have a beneficial effect on D. magna, and that aposymbiotic Daphnia are useful tools in understanding the role of symbiotic bacteria in the environmental responses and evolution of their hosts. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

  8. Exploration of the core metabolism of symbiotic bacteria.

    PubMed

    Klein, Cecilia Coimbra; Cottret, Ludovic; Kielbassa, Janice; Charles, Hubert; Gautier, Christian; Ribeiro de Vasconcelos, Ana Tereza; Lacroix, Vincent; Sagot, Marie-France

    2012-08-31

    A large number of genome-scale metabolic networks is now available for many organisms, mostly bacteria. Previous works on minimal gene sets, when analysing host-dependent bacteria, found small common sets of metabolic genes. When such analyses are restricted to bacteria with similar lifestyles, larger portions of metabolism are expected to be shared and their composition is worth investigating. Here we report a comparative analysis of the small molecule metabolism of symbiotic bacteria, exploring common and variable portions as well as the contribution of different lifestyle groups to the reduction of a common set of metabolic capabilities. We found no reaction shared by all the bacteria analysed. Disregarding those with the smallest genomes, we still do not find a reaction core, however we did find a core of biochemical capabilities. While obligate intracellular symbionts have no core of reactions within their group, extracellular and cell-associated symbionts do have a small core composed of disconnected fragments. In agreement with previous findings in Escherichia coli, their cores are enriched in biosynthetic processes whereas the variable metabolisms have similar ratios of biosynthetic and degradation reactions. Conversely, the variable metabolism of obligate intracellular symbionts is enriched in anabolism. Even when removing the symbionts with the most reduced genomes, there is no core of reactions common to the analysed symbiotic bacteria. The main reason is the very high specialisation of obligate intracellular symbionts, however, host-dependence alone is not an explanation for such absence. The composition of the metabolism of cell-associated and extracellular bacteria shows that while they have similar needs in terms of the building blocks of their cells, they have to adapt to very distinct environments. On the other hand, in obligate intracellular bacteria, catabolism has largely disappeared, whereas synthetic routes appear to have been selected for

  9. On the nature of the symbiotic binary AX Persei

    NASA Technical Reports Server (NTRS)

    Mikolajewska, Joanna; Kenyon, Scott J.

    1992-01-01

    Photometric and spectroscopic observations of the symbiotic binary AX Persei are presented. This system contains a red giant that fills its tidal lobe and transfers material into an accretion disk surrounding a low-mass main-sequence star. The stellar masses - 1 solar mass for the red giant and about 0.4 solar mass for the companion - suggest AX Per is poised to enter a common envelope phase of evolution. The disk luminosity increases from L(disk) about 100 solar luminosity in quiescence to L(disk) about 5700 solar luminosity in outburst for a distance of d = 2.5 kpc. Except for visual maximum, high ionization permitted emission lines - such as He II - imply an EUV luminosity comparable to the disk luminosity. High-energy photons emitted by a hot boundary layer between the disk and central star ionize a surrounding nebula to produce this permitted line emission. High ionization forbidden lines form in an extended, shock-excited region well out of the binary's orbital plane and may be associated with mass loss from the disk.

  10. Evolution of the symbiotic binary system AG Dranconis

    NASA Technical Reports Server (NTRS)

    Mikolajewska, Joanna; Kenyon, Scott J; Mikolajewski, Maciej; Garcia, Michael R.; Polidan, Ronald S.

    1995-01-01

    We present an analysis of new and archival photometric and spectroscopic observations of the symbiotic star AG Draconis. This binary has undergone several 1 - 3 mag optical and ultraviolet eruptions during the past 15 years. Our combination of optical and ultraviolet spectroscopic data allow a more complete analysis of this system than in previous papers. AG Dra is composed of a K-type bright giant M(sub g) approximately 1.5 solar mass) and a hot, compact star M(sub h approximatelly 0.4 - 0.6 solar mass) embedded in a dense, low metallicity nebula. The hot component undergoes occasional thermonuclear runaways that produce 2 - 3 mag optical/ultraviolet eruptions. During these eruptions, the hot component develops a low velocity wind that quenches x-ray emission from the underlying hot white dwarf. The photoionized nebula changes its volume by a factor of 5 throughout an eruptin cycle. The K bright giant occults low ionization emission lines during superior conjunctions at all outburst phases but does not occult high ionization lines in outburst (and perhaps quiescence). This geometry and the component masses suggest a system inclination of i approximately 30 deg - 45 deg.

  11. Cristispira from oyster styles: complex morphology of large symbiotic spirochetes

    NASA Technical Reports Server (NTRS)

    Margulis, L.; Nault, L.; Sieburth, J. M.

    1991-01-01

    Crystalline styles (digestive organs) of bivalve mollusks provide the habitat for highly motile bacteria. Styles from freshly-collected oysters, Crassostrea virginica, were studied by electron microscopy; Cristispira spirochetes were abundant in these organs. Detailed study reveals these spirochetes to be among the most complex prokaryotic cells known. More than 600 periplasmic flagella and an adhering outer lipoprotein membrane (e.g., a 270 degrees sillon) form the ultrastructural basis for the "crista," first described by light microscopy. Unique rosette structures corresponding to the "chambers" or "ovoid inclusions" of light microscopy were detected at the periphery of all protoplasmic cylinders. Polar organelles and linearly aligned flagellar insertions are conspicuous. In size and complexity, Cristispira more resembles Pillotina, Diplocalyx, Clevelandina and Hollandina (large spirochetes symbiotic in termites) than it does Treponema. Cristispira pectinis (Gross, 1910), the type species; Spirillum ostrea (Noguchi, 1921); and another, less frequent bacterial symbiont are the predominant inhabitants of the dense style matrix. The ultrastructure of the spirillum and an electron micrograph of the third bacterium are shown.

  12. Symbiotic Solid State Drives: Management of Modern NAND Flash Memory

    NASA Astrophysics Da