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.
Papers published on a yearly basis
Papers
More filters
TL;DR: It is proposed that culture‐independent identification and isolation of bacteria that are enriched in rhizosphere and roots, followed by systematic testing and confirming their growth‐promoting capacity, is a necessary step towards designing effective microbial inoculants.
Abstract: Sugarcane is a globally important food, biofuel and biomaterials crop. High nitrogen (N) fertilizer rates aimed at increasing yield often result in environmental damage because of excess and inefficient application. Inoculation with diazotrophic bacteria is an attractive option for reducing N fertilizer needs. However, the efficacy of bacterial inoculants is variable, and their effective formulation remains a knowledge frontier. Here, we take a new approach to investigating diazotrophic bacteria associated with roots using culture-independent microbial community profiling of a commercial sugarcane variety (Q208(A) ) in a field setting. We first identified bacteria that were markedly enriched in the rhizosphere to guide isolation and then tested putative diazotrophs for the ability to colonize axenic sugarcane plantlets (Q208(A) ) and promote growth in suboptimal N supply. One isolate readily colonized roots, fixed N2 and stimulated growth of plantlets, and was classified as a new species, Burkholderia australis sp. nov. Draft genome sequencing of the isolate confirmed the presence of nitrogen fixation. We propose that culture-independent identification and isolation of bacteria that are enriched in rhizosphere and roots, followed by systematic testing and confirming their growth-promoting capacity, is a necessary step towards designing effective microbial inoculants.
81 citations
TL;DR: It is concluded that symbiotic N2 fixation plays an important role in maintaining high amounts of soil available N in undisturbed forest.
Abstract: Summary
• 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 δ15N values measured. Estimates of N2 fixation rates were calculated using the 15N natural abundance method. Pot experiments were conducted on the effect of N and P availability on N2 fixation using the 15N-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.
81 citations
TL;DR: Nitrogen fixation, as measured by the acetylene reduction method, has been detected in situ in stratified sediment cores from Kingoodie Bay, Tay Estuary, northeast Scotland and it is possible that these bacteria play an important role in supplying nitrogen to the nitrogen deficient Kingoodies Bay sediments.
81 citations
TL;DR: Gene silencing has been used to show that legume haemoglobins are crucial for growth and symbiotic bacteria can reduce enough N2 to provide the plant with sufficient ammonium for growth.
81 citations
TL;DR: CO(2) fixation is correlated with nitrogen fixation in alfalfa nodules and is demonstrated to provide 25% of the carbon required for assimilation of symbiotically fixed nitrogen in al falfa.
Abstract: In vivo CO(2) fixation activity and in vitro phosphoenolpyruvate carboxylase activity were demonstrated in effective and ineffective nodules of alfalfa (Medicago sativa L.) and in the nodules of four other legume species. Phosphoenolpyruvate carboxylase activity was greatly reduced in nodules from both host and bacterially conditioned ineffective alfalfa nodules as compared to effective alfalfa nodules.Forage harvest and nitrate application reduced both in vivo and in vitro CO(2) fixation activity. By day 11, forage harvest resulted in a 42% decline in in vitro nodule phosphoenolpyruvate carboxylase activity while treatment with either 40 or 80 kilograms nitrogen per hectare reduced activity by 65%. In vitro specific activity of phosphoenolpyruvate carboxylase and glutamate synthase were positively correlated with each other and both were positively correlated with acetylene reduction activity.The distribution of radioactivity in the nodules of control plants (unharvested, 0 kilograms nitrogen per hectare) averaged 73% into the organic acid and 27% into the amino acid fraction. In nodules from harvested plants treated with nitrate, near equal distribution of radioactivity was observed in the organic acid (52%) and amino acid (48%) fractions by day 8. Recovery to control distribution occurred only in those nodules whose in vitro phosphoenolpyruvate carboxylase activity recovered.The results demonstrate that CO(2) fixation is correlated with nitrogen fixation in alfalfa nodules. The maximum rate of CO(2) fixation for attached and detached alfalfa nodules at low CO(2) concentrations (0.13-0.38% CO(2)) were 18.3 and 4.9 nanomoles per hour per milligram dry weight, respectively. Nodule CO(2) fixation was estimated to provide 25% of the carbon required for assimilation of symbiotically fixed nitrogen in alfalfa.
81 citations