scholarly journals Nitrogen utilization and transformation ofStenotrophomonas maltophiliaW-6 with nitrogen-fixing ability

2018 ◽  
Author(s):  
Shutong Wang ◽  
Yi Xu ◽  
Zhenlun Li
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogen Cycle ◽  
Biological Nitrogen Fixation ◽  
Stenotrophomonas Maltophilia ◽  
Inorganic Nitrogen ◽  
Nitrate Removal ◽  
Nitrogen Utilization ◽  
Purple Soil ◽  
Nitrogen Fixing ◽  
Biological Nitrogen

AbstractStrain W-6 was isolated from the purple soil and successfully identifed asStenotrophomonas maltophiliaand used for the investigation on nitrogen utilization. Strain W-6 was monitored with the ability of biological nitrogen fixation when N2was used for the sole nitrogen source, and yet nitrogenase activity would be inhibited in the presence of extra nitrogen. Moreover, Strain W-6 could utilize NO3−, NO2−and NH4+for cell growth through assimilation, but unable to convert them to atmospheric nitrogen. Meantime, accumulation of nitrite was observed during the nitrate removal process, and the optimal conditions for nitrate removal were temperature of 20°C, shaking speed of 150 rpm, sodium succinate as the carbon source and C/N of 12. The experimental results indicate thatStenotrophomonas maltophiliautilize W-6 could utilize not only N2but also other nitrogen sources directly as its N substance. Therefore, heterotrophicAzotobactermay possess a great significance to nitrogen cycle except in biological nitrogen fixation.ImportanceAzotobacterspp. are found in soils worldwide, with features not simply for the nitrogen fixation, but for the energy metabolism relevant to agriculture. However, the role ofAzotobacterpotential in the function of nitrogen cycle except in biological nitrogen fixation is largely unknown. As such, whether bacteria utilize either inorganic nitrogen or organic nitrogen has remained obscure. The present studies indicate thatStenotrophomonas maltophiliaW-6 could highly efficient utilize nitrate, nitrite and ammonium etc. N substance and detect NH4+as final product. The transport velocities of nitrate-N to nitrite-N was quickly without gaseous nitrogen was produced. We probed the relationship between biological nitrogen fixation and N cycle via N conversion processes byS. maltophiliaW-6 with nitrogen-fixing ability

The Leeuwenhoek Lecture, 1992 Bacterial evolution and the nitrogen-fixing plant

1992 ◽  
Vol 338 (1286) ◽  
pp. 409-416 ◽  
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Bacterial Species ◽  
Nitrogen Fixing ◽  
Bacterial Evolution ◽  
Late Emergence ◽  
Biological Nitrogen

Biological nitrogen fixation is fundamental to the economy of the biosphere, yet it is restricted to a few dozen bacterial species. Why have plants not acquired it during evolution? No serious physiological or genetic obstacles seem to exist. Has a relatively late emergence, among genomically flexible prokaryotes, effectively precluded appropriate seletion pressure?

scholarly journals Biological Nitrogen Fixation in the Context of Global Change

2013 ◽  
Vol 26 (5) ◽  
pp. 486-494 ◽  
Author(s):  
José Olivares ◽  
Eulogio J. Bedmar ◽  
Juan Sanjuán
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Food Production ◽  
Agricultural Practices ◽  
N Fertilization ◽  
Agricultural Crops ◽  
Nitrogen Fixing ◽  
Sustainable Technologies ◽  
Use Efficiency ◽  
Biological Nitrogen

The intensive application of fertilizers during agricultural practices has led to an unprecedented perturbation of the nitrogen cycle, illustrated by the growing accumulation of nitrates in soils and waters and of nitrogen oxides in the atmosphere. Besides increasing use efficiency of current N fertilizers, priority should be given to value the process of biological nitrogen fixation (BNF) through more sustainable technologies that reduce the undesired effects of chemical N fertilization of agricultural crops. Wider legume adoption, supported by coordinated legume breeding and inoculation programs are approaches at hand. Also available are biofertilizers based on microbes that help to reduce the needs of N fertilization in important crops like cereals. Engineering the capacity to fix nitrogen in cereals, either by themselves or in symbiosis with nitrogen-fixing microbes, are attractive future options that, nevertheless, require more intensive and internationally coordinated research efforts. Although nitrogen-fixing plants may be less productive, at some point, agriculture must significantly reduce the use of warming (chemically synthesized) N and give priority to BNF if it is to sustain both food production and environmental health for a continuously growing human population.

Understanding plant-root interactions with rhizobacteria to improve biological nitrogen fixation in crops

2021 ◽  
pp. 163-194
Author(s):  
Ulrike Mathesius ◽  
◽  
Jian Jin ◽  
Yansheng Li ◽  
Michelle Watt ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Plant Root ◽  
Current Understanding ◽  
Plant Roots ◽  
Nitrogen Fixing ◽  
Root Interactions ◽  
Molecular Determinants ◽  
Abiotic Constraints ◽  
Biological Nitrogen

Plant roots have evolved with the presence of rhizobacteria that can colonise the surface or interior of the plant. Some of these rhizobacteria are actively recruited by the plant and carry out particular functions, in particular in nutrient acquisition. Nitrogen-fixing bacteria form associations with many plant species, either as external associations or as symbiotic endophytes. The symbiosis between legumes and nitrogen-fixing rhizobia has been studied in most detail and is the most important contributor to nitrogen fixation in agriculture. This chapter highlights our current understanding of the molecular determinants of legume nodulation as well as challenges for improvements of biological nitrogen fixation in legumes and non-legumes. There is a need for connecting out knowledge of the molecular regulation of nodulation with field-based studies that take into account the interaction of nodulation with biotic and abiotic constraints. In addition, current approaches for engineering new symbioses are discussed.

scholarly journals Transcriptional Analysis of an Ammonium-Excreting Strain of Azotobacter vinelandii Deregulated for Nitrogen Fixation

2017 ◽  
Vol 83 (20) ◽  
Author(s):  
Brett M. Barney ◽  
Mary H. Plunkett ◽  
Velmurugan Natarajan ◽  
Florence Mus ◽  
Carolann M. Knutson ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Stationary Phase ◽  
Gene Transcription ◽  
Biological Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Content Type ◽  
Ammonium Production ◽  
Biological Nitrogen

ABSTRACT Biological nitrogen fixation is accomplished by a diverse group of organisms known as diazotrophs and requires the function of the complex metalloenzyme nitrogenase. Nitrogenase and many of the accessory proteins required for proper cofactor biosynthesis and incorporation into the enzyme have been characterized, but a complete picture of the reaction mechanism and key cellular changes that accompany biological nitrogen fixation remain to be fully elucidated. Studies have revealed that specific disruptions of the antiactivator-encoding gene nifL result in the deregulation of the nif transcriptional activator NifA in the nitrogen-fixing bacterium Azotobacter vinelandii, triggering the production of extracellular ammonium levels approaching 30 mM during the stationary phase of growth. In this work, we have characterized the global patterns of gene expression of this high-ammonium-releasing phenotype. The findings reported here indicated that cultures of this high-ammonium-accumulating strain may experience metal limitation when grown using standard Burk's medium, which could be amended by increasing the molybdenum levels to further increase the ammonium yield. In addition, elevated levels of nitrogenase gene transcription are not accompanied by a corresponding dramatic increase in hydrogenase gene transcription levels or hydrogen uptake rates. Of the three potential electron donor systems for nitrogenase, only the rnf1 gene cluster showed a transcriptional correlation to the increased yield of ammonium. Our results also highlight several additional genes that may play a role in supporting elevated ammonium production in this aerobic nitrogen-fixing model bacterium. IMPORTANCE The transcriptional differences found during stationary-phase ammonium accumulation show a strong contrast between the deregulated (nifL-disrupted) and wild-type strains and what was previously reported for the wild-type strain under exponential-phase growth conditions. These results demonstrate that further improvement of the ammonium yield in this nitrogenase-deregulated strain can be obtained by increasing the amount of available molybdenum in the medium. These results also indicate a potential preference for one of two ATP synthases present in A. vinelandii as well as a prominent role for the membrane-bound hydrogenase over the soluble hydrogenase in hydrogen gas recycling. These results should inform future studies aimed at elucidating the important features of this phenotype and at maximizing ammonium production by this strain.

scholarly journals Metabolic model of nitrogen-fixing obligate aerobe Azotobacter vinelandii demonstrates adaptation to oxygen concentration and metal availability

2021 ◽  
Author(s):  
Alexander B Alleman ◽  
Florence Mus ◽  
John W Peters
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Metabolic Model ◽  
Metal Availability ◽  
Respiratory Protection ◽  
Nitrogen Fixing ◽  
A Genome ◽  
Biological Nitrogen ◽  
Genome Scale

There is considerable interest in promoting biological nitrogen fixation as a mechanism to reduce the inputs of nitrogenous fertilizers in agriculture, a problem of agronomic, economic, and environmental importance. For the potential impact of biological nitrogen fixation in agriculture to be realized, there are considerable fundamental knowledge gaps that need to be addressed. Biological nitrogen fixation or the reduction of N2 to NH3 is catalyzed by nitrogenase which requires a large amount of energy in the form of ATP and low potential electrons. Nitrogen-fixing organisms that respire aerobically have an advantage in meeting the energy demands of biological nitrogen fixation but face challenges of protecting nitrogenase from inactivation in the presence of oxygen. Here, we have constructed a genome-scale metabolic model of the aerobic metabolism of nitrogen-fixing bacteria Azotobacter vinelandii, which uses a complex electron transport system, termed respiratory protection, to consume oxygen at a high rate keeping intracellular conditions microaerobic. Our model accurately determines growth rate under high oxygen and high substrate concentration conditions, demonstrating the large flux of energy directed to respiratory protection. While respiratory protection mechanisms compensate the energy balance in high oxygen conditions, it does not account for all substrate intake, leading to increased maintenance rates. We have also shown how A. vinelandii can adapt under different oxygen concentrations and metal availability by rearranging flux through the electron transport system. Accurately determining the energy balance in a genome-scale metabolic model is required for future engineering approaches.

scholarly journals Biological Nitrogen Fixation in CMIP6 Models

2021 ◽  
Author(s):  
Taraka Davies-Barnard ◽  
Sönke Zaehle ◽  
Pierre Friedlingstein
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogen Cycle ◽  
Primary Productivity ◽  
Biological Nitrogen Fixation ◽  
Net Primary Productivity ◽  
Explanatory Power ◽  
Future Climate Change ◽  
Tight Coupling ◽  
Change Models ◽  
Biological Nitrogen

Abstract. Biological nitrogen fixation is the main source of new nitrogen into natural terrestrial ecosystems and consequently in the nitrogen cycle in many earth system models. Representation of biological nitrogen fixation varies, and because of the tight coupling between the carbon and nitrogen cycles, previous studies have shown this affects net primary productivity. Here we present the first assessment of the performance of biological nitrogen fixation in models contributing to CMIP6 compared to observed and observation-constrained estimates of biological nitrogen fixation. We find that 9/10 models represent global total biological nitrogen fixation within the uncertainty of recent global estimates. However, 6/10 models overestimate the amount of fixation in the tropics, and therefore the extent of the latitudinal gradient in the global distribution. For the SSP3-7.0 scenario of future climate change, models project increases in fixation over the 21st century of up to 80 %. However, while the historical range of biological nitrogen fixation amongst models is large (up to 140 kg ha−1 yr−1 at the grid cell level and 43–208 TgN yr−1 globally) this does not have explanatory power for variations in net primary productivity or the coupled nitrogen-carbon cycle. Models with shared structures can have significant variations in both biological nitrogen fixation and other parts of the nitrogen cycle without differing in their net primary productivity. This points to systematic challenges in carbon-nitrogen model structures.

scholarly journals Soil nitrogen response to shrub encroachment in a degrading semiarid grassland

2018 ◽  
Author(s):  
Thomas Turpin-Jelfs ◽  
Katerina Michaelides ◽  
Joel A. Biederman ◽  
Alexandre M. Anesio
Keyword(s):  
Nitrogen Fixation ◽  
Soil Nitrogen ◽  
Biological Nitrogen Fixation ◽  
Inorganic Nitrogen ◽  
Shrub Encroachment ◽  
Shrub Cover ◽  
Prosopis Velutina ◽  
Free Living ◽  
Semiarid Grassland ◽  
Biological Nitrogen

Abstract. Transitions from grass- to shrub-dominated states in drylands by woody plant encroachment represent significant forms of land cover change with the potential to alter the spatial distribution and cycling of soil resources. Yet an understanding of how this phenomenon impacts the soil nitrogen pool, which is essential to primary production in arid and semiarid systems, is poorly resolved. In this study, we quantified how the distribution and speciation of soil nitrogen, as well as rates of free-living biological nitrogen fixation, changed along a gradient of increasing mesquite (Prosopis velutina Woot.) cover in a semiarid grassland of the Southwestern US. Our results show that site-level concentrations of total nitrogen remain unchanged with increasing shrub cover as losses from intershrub areas (sum of grass and bare-soil cover) are proportional to increases in soils under shrub canopies. However, despite the similar carbon-to-nitrogen ratio and microbial biomass of soil from intershrub and shrub areas at each site, site-level concentrations of inorganic nitrogen increase with shrub cover due to the accumulation of ammonium and nitrate in soils beneath shrub canopies. Using the acetylene reduction assay technique, we found increasing ratios of inorganic nitrogen-to-bioavailable phosphorus inhibit rates of biological nitrogen fixation by free-living soil bacteria. Consequently, we conclude that shrub encroachment has the potential to significantly alter the dynamics of soil nitrogen cycling in dryland systems.

The fixed nitrogen sensitivity of biological nitrogen fixation in salt marshes sediments from the northeastern United States

2020 ◽  
Author(s):  
Romain Darnajoux ◽  
Rei Zhang ◽  
Katja Luxem ◽  
Xinning Zhang
Keyword(s):  
Nitrogen Fixation ◽  
Salt Marshes ◽  
Biological Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Inorganic Nitrogen ◽  
Ammonium Concentration ◽  
Desulfovibrio Vulgaris ◽  
Fixed Nitrogen ◽  
Sulfate Reducing ◽  
Biological Nitrogen

<p>Biological nitrogen fixation, the main input of fixed N into ecosystems, converts inert N<sub>2</sub> gas into bioavailable ammonium in an energetically costly reaction catalyzed by the prokaryotic metalloenzyme nitrogenase.  The high ATP and reductant requirements of N<sub>2</sub> fixation explain why this process is highly regulated in diazotrophs, with the presence of ammonium inhibiting nitrogenase expression and activity. Yet, several reports of N<sub>2</sub> fixation in ammonium- and nitrate-rich (10 to 300 µM) benthic environments challenge our understanding of a key environmental sensitivity of N<sub>2</sub> fixation. Field studies point to heterotrophic sulfate reducers as the likely diazotrophs in these benthic settings, but the fixed N sensitivity of sulfate-reducing diazotrophs is not well understood due to a dearth of culture studies. Additionally, assays of N<sub>2</sub> fixation in incubations rarely involve parallel measurements of dissolved inorganic nitrogen, possibly leading to experimental bias in favor of detecting activity under ammonium-replete initial conditions.</p><p>To help reconcile the environmental results, we investigate the ammonium sensitivity of N<sub>2</sub> fixation using the acetylene reduction assay and <sup>15</sup>N<sub>2</sub> tracer methods in i) the model sulfate-reducing diazotroph, <em>Desulfovibrio vulgaris</em> str. Hildenborough (DvH), ii) four enrichment cultures from salt marsh sediments of New Jersey, and iii) slurry incubations of sediments collected from three northeastern salt marshes. In all instances, we found that ammonium strongly inhibits biological nitrogen fixation, with nitrogenase activity only detectable when ammonium concentration is below a threshold of 10 µM (slurry incubation) or 2 µM (pure cultures, enrichments). Amendment of ammonium quickly inhibits nitrogen fixation and nitrogenase activity only resumes  once ammonium is depleted to the threshold level. Ammonium additions to actively fixing samples show complete inhibition of N<sub>2</sub> fixation within several hours post-addition. </p><p>Our measurements of the ammonium sensitivity of benthic N<sub>2</sub> fixation are consistent with the traditional understanding of nitrogen fixer metabolism and with early findings of Postgate et al. (1984) demonstrating that N<sub>2</sub> fixation by the sulfate reducer <em>Desulfovibrio gigas</em> is inhibited by ammonium levels that exceed 10 µM. These results help clarify a long-standing paradox in benthic nitrogen cycling. We suggest that prior observations of N<sub>2</sub> fixation at elevated ammonium levels could reflect methodological artifacts due to very fast depletion of ammonium during activity assays, legacy N<sub>2</sub> fixation activity associated with incomplete inhibition by ammonium, or spatial heterogeneity. Further work to standardize fixed N sensitivity assays could help with cross-study comparisons and with clarifying inconsistencies in our understanding of how environmental fixed nitrogen levels control nitrogen fixation.</p>

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