Topic
Nitrogen fixation
About: Nitrogen fixation is a research topic. Over the lifetime, 7940 publications have been published within this topic receiving 232921 citations. The topic is also known as: GO:0009399.
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TL;DR: Acetylene reduction activity was demonstrated in pure cultures of two actinomycete strains isolated from nodules of Casuarina equisetifolia, comparable to that of free-living Rhizobium strains, but appeared to be less sensitive to pO(2) and more sensitive to the presence of combined nitrogen.
Abstract: Acetylene reduction activity was demonstrated in pure cultures of two actinomycete strains isolated from nodules of Casuarina equisetifolia. This activity was comparable to that of free-living Rhizobium strains, but appeared to be less sensitive to pO2 and more sensitive to the presence of combined nitrogen. Images
111 citations
TL;DR: This study demonstrated that there are important differences in the carbon dioxide and nitrogen fixation mechanisms among bioleaching bacteria that coexist in mining environments and provided an analysis of the potential regulatory pathways and functional networks that control carbon and nitrogenfixing in these microorganisms.
Abstract: Carbon and nitrogen fixation are essential pathways for autotrophic bacteria living in extreme environments. These bacteria can use carbon dioxide directly from the air as their sole carbon source and can use different sources of nitrogen such as ammonia, nitrate, nitrite, or even nitrogen from the air. To have a better understanding of how these processes occur and to determine how we can make them more efficient, a comparative genomic analysis of three bioleaching bacteria isolated from mine sites in Chile was performed. This study demonstrated that there are important differences in the carbon dioxide and nitrogen fixation mechanisms among bioleaching bacteria that coexist in mining environments. In this study, we probed that both Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans incorporate CO2 via the Calvin-Benson-Bassham cycle; however, the former bacterium has two copies of the Rubisco type I gene whereas the latter has only one copy. In contrast, we demonstrated that Leptospirillum ferriphilum utilizes the reductive tricarboxylic acid cycle for carbon fixation. Although all the species analyzed in our study can incorporate ammonia by an ammonia transporter, we demonstrated that Acidithiobacillus thiooxidans could also assimilate nitrate and nitrite but only Acidithiobacillus ferrooxidans could fix nitrogen directly from the air. The current study utilized genomic and molecular evidence to verify carbon and nitrogen fixation mechanisms for three bioleaching bacteria and provided an analysis of the potential regulatory pathways and functional networks that control carbon and nitrogen fixation in these microorganisms.
111 citations
TL;DR: 15N abundance values failed to distinguish N2 fixing from non-fixing woody species, and therefore, could not be used in the ecosystem to determine the dependence of putative nitrogen fixing species on N2 fixation.
Abstract: Studies of the variation in δ15N values for plants from a fire-prone Banksia woodland in South West Australia showed that pioneer herbaceous, non-mycorrhizal species which were active in nitrate reduction and storage, had the highest values (1.81%c). A detailed study of one such species Ptilotus polystachus demonstrated a close correspondence between the δ15N values of soil nitrate, xylem nitrate and leaf total nitrogen, suggesting an exclusive reliance on nitrate ions as nitrogen source. These pioneer species also showed a preponderance of the chloroplastic isoform of glutamine synthetase while woody species generally had higher activity associated with the cytosolic isoform. The group comprising monocotyledonous hemicryptophytes and geophytes contained species with slightly positive δ15N values and moderately active in nitrate reduction and storage. Nitrogen-fixing species had the lowest δ15N values (–0.36‰), irrespective of their apparent utilisation of nitrate. However, woody resprouter species which had low levels of nitrate reduction and storage had δ15N values which fell within the range of values obtained for the miscellaneous assemblage of N2-fixing species. Consequently, 15N abundance values failed to distinguish N2 fixing from non-fixing woody species, and therefore, could not be used in the ecosystem to determine the dependence of putative nitrogen fixing species on N2 fixation. The study demonstrated complex patterns of nitrogen utilization in the ecosystem in which exploitation of different nitrogen resources related to plant life form and the physiological attributes of nitrogen assimilation by component species.
111 citations
TL;DR: It is proposed that the net effect of aggregates on nitrogen loss is negligible in NO3−-depleted, fully oxygenated (surface) waters, and that patterns of N-transformation processes similar to those observed in this study arise also in other phytoplankton colonies, marine snow and fecal pellets.
Abstract: Colonies of N2-fixing cyanobacteria are key players in supplying new nitrogen to the ocean, but the biological fate of this fixed nitrogen remains poorly constrained. Here, we report on aerobic and ...
111 citations
TL;DR: It is concluded that inoculation with rhizobia and arbuscular mycorrhizal fungi could improve the efficiency in phosphorus use for symbiotic nitrogen fixation especially under phosphorus deficiency.
110 citations