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: It is demonstrated that the daily cycle of nitrogen fixation in Trichodesmium sp.
Abstract: Trichodesmium sp. IMS 101, originally isolated from coastal western Atlantic waters by Prufert-Bebout and colleagues and maintained in seawater-based media, was successfully cultivated in two artificial media. Its characteristics of growth, nitrogen fixation, and regulation of nitrogen fixation were compared to those of natural populations and Trichodesmium sp. NIBB 1067. Results indicate that the culture grown in artificial media had nitrogen fixation characteristics similar to those when the culture is grown in seawater-based medium and to those of Trichodesmium sp. in the natural habitat. The study provides practical artificial media to facilitate the physiological studies of these important diazotrophic cyanobacteria, as well as the cultivation of other Trichodesmium species in future studies. Manipulations of the light/dark cycle were performed to determine whether or not the daily cycle of nitrogen fixation is a circadian rhythm. Cultures grown under continuous light maintained the cycle for up to 6 days. We demonstrated that the daily cycle of nitrogen fixation in Trichodesmium sp. IMS 101 was at least partially under the control of a circardian rhythm.
252 citations
TL;DR: It is found that all individuals of field‐collected Mediterranean fruit flies harbour large diazotrophic enterobacterial populations that express dinitrogen reductase in the gut, and nitrogen fixation was demonstrated in isolated guts and in live flies and may significantly contribute to the fly's nitrogen intake.
Abstract: Nitrogen, although abundant in the atmosphere, is paradoxically a limited resource for multicellular organisms. In the Animalia, biological nitrogen fixation has solely been demonstrated in termites. We found that all individuals of field-collected Mediterranean fruit flies (Ceratitis capitata) harbour large diazotrophic enterobacterial populations that express dinitrogen reductase in the gut. Moreover, nitrogen fixation was demonstrated in isolated guts and in live flies and may significantly contribute to the fly's nitrogen intake. The presence of similar bacterial consortia in additional insect orders suggests that nitrogen fixation occurs in vast pools of terrestrial insects. On such a large scale, this phenomenon may have a considerable impact on the nitrogen cycle.
249 citations
TL;DR: The results presented here show that the zooxanthellae of M. cavernosa acquire nitrogen from cyanobacterial nitrogen fixation, and that the distribution of corals with symbiotic cyanobacteria is positively correlated with increasing depth.
Abstract: Colonies of the Caribbean coral Montastraea cavernosa (Linnaeus) that harbor endosymbiotic cyanobacteria can fix nitrogen, whereas conspecifics without these symbionts cannot. The pattern of nitrogen fixation is diurnal and maximum rates occur in the early morning and evening. An analysis of delta N-15 stable isotope data showed that the zooxanthellae, but not the animal tissue, from colonies with cyanobacteria preferentially use the products derived from nitrogen fixation, and that these zooxanthellae also have a greater DNA content per cell, suggesting that these cells are in the DNA synthesis (S) and gap (G(2)) + Mitosis (M) phase of their cell cyle and are preparing to undergo cell division. Since nitrogen fixation did not occur during those times of the day when hyperoxia is known to occur, low oxygen concentrations might be required to support cyanobacterial respiration and provide the energy needed to fix nitrogen because the reaction centers of these cyanobacteria are uncoupled from light harvesting accessory pigments and the photosynthetic electron transport chain. Consistent with this were the depleted delta C-13 stable isotope signatures in all compartments of those corals with symbiotic cyanobacteria, which show an increase in heterotrophy compared with samples of M. cavernosa without cyanobacteria. Using modeled underwater light fields and measurements of photosynthesis, we show that the amount of time in which nitrogen fixation in these corals can take place increases with depth and that the distribution of corals with symbiotic cyanobacteria is positively correlated with increasing depth. The results presented here show that the zooxanthellae of M. cavernosa acquire nitrogen from cyanobacterial nitrogen fixation. Given that nitrogen limitation has long been proposed to contribute to the stability of these symbiotic associations, the mechanism by which zooxanthellae symbiosis in these corals is maintained remains an important question and the subject of future study.
247 citations
TL;DR: In this paper, the authors present results on a number of structural and physiological characteristics that allow arctic legumes to function in extreme environments, indicating that both the plants and their rhizobia have successfully adapted to arctic conditions.
Abstract: Biological nitrogen fixation is a phenomenon occurring in all known ecosystems. Symbiotic nitrogen fixation is dependent on the host plant genotype, the Rhizobium strain, and the interaction of these symbionts with the pedoclimatic factors and the environmental conditions. Extremes of pH affect nodulation by reducing the colonization of soil and the legume rhizosphere by rhizobia. Highly acidic soils (pH 8.0) tend to be high in sodium chloride, bicarbonate, and borate, and are often associated with high salinity which reduce nitrogen fixation. Nodulation and N-fixation are observed under a wide range of temperatures with optima between 20–30°C. Elevated temperatures may delay nodule initiation and development, and interfere with nodule structure and functioning in temperate legumes, whereas in tropical legumes nitrogen fixation efficiency is mainly affected. Furthermore, temperature changes affect the competitive ability of Rhizobium strains. Low temperatures reduce nodule formation and nitrogen fixation in temperate legumes; however, in the extreme environment of the high arctic, native legumes can nodulate and fix nitrogen at rates comparable to those observed with legumes in temperate climates, indicating that both the plants and their rhizobia have successfully adapted to arctic conditions. In addition to low temperatures, arctic legumes are exposed to a short growing season, a long photoperiod, low precipitation and low soil nitrogen levels. In this review, we present results on a number of structural and physiological characteristics which allow arctic legumes to function in extreme environments.
245 citations
01 Jan 1993
TL;DR: It is hoped that by the time of the next meeting, the enzymatic or transfer reactions carried out by the various nif genes involved in metal cluster assembly will be known in detail.
Abstract: this volume) to become associated with apodinitrogenase. The role of general chaperonins in promoting accumulation of nif gene products (Govezensky et al.1991) will be discussed in chapters of this section and may suggest roles for some of the nif-specific gene products to which no role has yet been ascribed. It is hoped that by the time of the next meeting, the enzymatic or transfer reactions carried out by the various nif genes involved in metal cluster assembly will be known in detail. Acknowledgements. The author wishes to acknowledge the contributions of his collaborators, GP Roberts, VK Shah, RM Allen, MJ Homer, R Chatterjee, J Allen and J Roll at the University of WI. Work from the laboratories of the author and his collaborators has been generously supported by the NIH and NRI/CGP.
244 citations