Hydrogen metabolism and energy costs of nitrogen fixation

Stam, H.

doi:10.1016/0378-1097(87)90187-x

Cited by 11 publications

(10 citation statements)

References 120 publications

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“…2), indieates that eleetron alloeation to H* as part of total electron allocation over nitrogenase was unaffeeted. The ratio between H* and N, reduetion ean be altered in favour of H* reduetion with an energy limitation for nitrogenase aetivity as well as at low Fe-protein/MoFe-protein ratios in vitro (Stam et al 1987). If applied to the present data on symbiotie Frankia in vivo, the REvalues do not support the hypothesis of limited energy supply to nitrogenase in the root nodules.…”

Section: Discussioncontrasting

confidence: 71%

Nitrogenase activity decay and energy supply in Frankia after addition of ammonium to the host plant Alnus incana

Huss‐Danell

Hahlin

1988

Physiologia Plantarum

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A clone of Alnus incana (L.) Moench was grown in symbiosis with a local source of Frankia or with Frankia Ar14. Seven to 9‐week‐old plants were given 20 mM NH4Cl (20 mM KCl = control) for 3 days. Nitrogenase activity of intact plants decreased gradually within the 3 days of treatment to about 10% of the initial rates. Hydrogen evolution in air and total nitrogenase activity responded similarly to the treatment. Relative efficiency of nitrogenase thus remained the same throughout the study period. Control plants were not affected. Measurements of nitrogenase activity in root nodule homogenates (in vitro measurements) indicated loss of active nitrogenase rather than shortage of energy for nitrogenase activity in Frankia from ammonium‐treated plants. Shoots were exposed to 14CO2 and translocation of 14C to Frankia vesicle clusters prepared from root nodules was studied. Frankia vesicle clusters from ammonium‐treated plants contained about half as much 14C as those of control plants during all 3 days studied. One explanation for the observed effects is that a reduced supply of carbon to Frankia vesicles in the root nodules caused a reduced metabolic rate, including reduced protein synthesis and synthesis of nitrogenase.

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Section: Discussioncontrasting

confidence: 71%

Nitrogenase activity decay and energy supply in Frankia after addition of ammonium to the host plant Alnus incana

Huss‐Danell

Hahlin

1988

Physiologia Plantarum

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“…Marine N 2 fixation is performed by diverse prokaryotic organisms comprised predominantly of autotrophic cyanobacteria and heterotrophic bacteria (Zehr and Kudela, 2011). To supply the energetically expensive process of converting N 2 to ammonia Postgate and Eady, 1988;Stam et al, 1987), these organisms must obtain energy from either photosynthesis (cyanobacteria) or from bioavailable organic carbon compounds within the aquatic milieu (heterotrophic bacteria and mixotrophs). The total organic carbon (TOC) in the ocean contains dynamic particulate organic carbon (POC) and dissolved organic carbon (DOC) pools.…”

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confidence: 99%

Dynamics of transparent exopolymer particles (TEP) during the VAHINE mesocosm experiment in the New Caledonian lagoon

et al. 2016

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In the marine environment, transparent exopolymeric particles (TEP) produced from abiotic and biotic sources link the particulate and dissolved carbon pools and are essential vectors enhancing vertical carbon flux. We characterized spatial and temporal dynamics of TEP during the VAHINE experiment that investigated the fate of diazotroph-derived nitrogen and carbon in three replicate dissolved inorganic phosphorus (DIP)-fertilized 50 m 3 enclosures in the oligotrophic New Caledonian lagoon. During the 23 days of the experiment, we did not observe any depthdependent changes in TEP concentrations in the three sampled depths (1, 6, 12 m). TEP carbon (TEP-C) content averaged 28.9 ± 9.3 and 27.0 ± 7.2 % of total organic carbon (TOC) in the mesocosms and surrounding lagoon respectively and was strongly and positively coupled with TOC during P2 (i.e., days 15-23). TEP concentrations in the mesocosms declined for the first 9 days after DIP fertilization (P1 = days 5-14) and then gradually increased during the second phase. Temporal changes in TEP concentrations paralleled the growth and mortality rates of the diatomdiazotroph association of Rhizosolenia and Richelia that predominated the diazotroph community during P1. By P2, increasing total primary and heterotrophic bacterial production consumed the supplemented P and reduced availability of DIP. For this period, TEP concentrations were negatively correlated with DIP availability and turnover time of DIP (T DIP ), while positively associated with enhanced alkaline phosphatase activity (APA) that occurs when the microbial populations are P stressed. During P2, increasing bacterial production (BP) was positively correlated with higher TEP concentrations, which were also coupled with the increased growth rates and aggregation of the unicellular cyanobacterial Group C (UCYN-C) diazotrophs that bloomed during this period. We conclude that the composite processes responsible for the formation and breakdown of TEP yielded a relatively stable TEP pool available as both a carbon source and facilitating aggregation and flux throughout the experiment. TEP were probably mostly influenced by abiotic physical processes during P1, while biological activity (BP, diazotrophic growth and aggregation, export production) mainly impacted TEP concentrations during P2 when DIP availability was limited.

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“…As an exception, a high number of Rhizobium tropici strains possess the Hup trait but the hydrogenase activity displayed is not sufficient to eliminate the hydrogen evolved from nodules (23,26,43). Also, hydrogenase activity has been described for free-living cultures under nitrogen fixation conditions for Azorhizobium caulinodans ORS571 as well as for Sesbania rostrata bacteroids (40,41).…”

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Diversity and Evolution of Hydrogenase Systems in Rhizobia

Baginsky

Brito

Imperial

et al. 2002

Appl Environ Microbiol

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Uptake hydrogenases allow rhizobia to recycle the hydrogen generated in the nitrogen fixation process within the legume nodule. Hydrogenase (hup) systems in Bradyrhizobium japonicum and Rhizobium leguminosarum bv. viciae show highly conserved sequence and gene organization, but important differences exist in regulation and in the presence of specific genes. We have undertaken the characterization of hup gene clusters from Bradyrhizobium sp. (Lupinus), Bradyrhizobium sp. (Vigna), and Rhizobium tropici and Azorhizobium caulinodans strains with the aim of defining the extent of diversity in hup gene composition and regulation in endosymbiotic bacteria. Genomic DNA hybridizations using hupS, hupE, hupUV, hypB, and hoxA probes showed a diversity of intraspecific hup profiles within Bradyrhizobium sp. A large amount of hydrogen is released from legume root nodules during the nitrogen fixation process. This hydrogen production has been described as one of the major factors that affect the efficiency of symbiotic nitrogen fixation (39). Uptake hydrogenases allow endosymbiotic bacteria to oxidize the hydrogen produced by nitrogenase. This symbiotic hydrogen oxidation has been shown to reduce the energy losses associated with nitrogen fixation and to enhance productivity in certain legume hosts (1,14).A detailed characterization of the hydrogen uptake (hup) system has been carried out in Bradyrhizobium japonicum and Rhizobium leguminosarum bv. viciae (for a review, see reference 35). In both genera, the first component of this system is a membrane-bound, dimeric [NiFe] hydrogenase composed by two polypeptides of 35 and 65 kDa. These polypeptides are synthesized as precursors, which are proteolytically processed after metal cluster insertion. The hup genetic determinants are clustered in large DNA regions (20, 21), whose sequence analysis has revealed the presence of at least 17 common genes (hupSLCDFGHIJKhypABFCDEX) arranged in at least three operons with conserved gene composition and organization (35). Hydrogenase structural subunits are encoded by the hupS and hupL genes, whereas the remaining hup and hyp gene products are involved in the recruitment and incorporation of nickel and other metallic groups into the hydrogenase active site (for reviews, see references 12 and 35). Although the R. leguminosarum and B. japonicum hydrogenase systems are highly homologous, they show important differences in regulation and in the presence of specific genes. The hupE gene is specific for the R. leguminosarum UPM791 hup gene cluster. The function of its predicted product is unknown, but it has been proposed that it might act as a nickel transporter (35). In contrast, this strain lacks the hupNOP genes, whose gene products are involved in nickel metabolism in B. japonicum (16). Two completely different regulatory circuits control hydrogenase gene expression in these bacteria (36). Bradyrhizobium japonicum expresses hup genes in symbiosis as well as in microaerobic free-living cells. Four proteins are involved in regulation in this ...

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Hydrogen metabolism and energy costs of nitrogen fixation

Cited by 11 publications

References 120 publications

Nitrogenase activity decay and energy supply in Frankia after addition of ammonium to the host plant Alnus incana

Nitrogenase activity decay and energy supply in Frankia after addition of ammonium to the host plant Alnus incana

Dynamics of transparent exopolymer particles (TEP) during the VAHINE mesocosm experiment in the New Caledonian lagoon

Diversity and Evolution of Hydrogenase Systems in Rhizobia

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