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.

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?

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 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

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 Role of Biological Nitrogen Fixation (BNF) in Sustainable Agriculture: A Review

2021 ◽  
Vol 4 (3) ◽  
Author(s):  
Rittwika Mukherjee ◽  
Supatra Sen
Keyword(s):  
Nitrogen Fixation ◽  
Sustainable Agriculture ◽  
Biological Nitrogen Fixation ◽  
Crop Production ◽  
Food Systems ◽  
Management Practices ◽  
Ghg Emissions ◽  
N Fertilization ◽  
Agricultural System ◽  
Biological Nitrogen

Agriculture has an enormous environmental footprint. One of the best ways to mitigate climate change is to create balanced food systems based on sustainable agriculture. To reduce the chemical dependence scientists are engineering crop plants for N 2 fixation and they are focused on the biological process BNF (Biological Nitrogen Fixation) for the needs of N2 for crop plant soils. N2 fixed by the BNF process reduces the production cost, Green House gas (GHG) emissions, pollution of surface and ground water. Several management practices are there which influence BNF process in agricultural system. They are N- fertilization species genotype and cultivar and seeding ratios. Better management practices can help to improve N2 fixation. This review highlights the agro-economic importance of BNF and shows it as a cost effective, non- polluting way to improve the soil fertility and crop production.

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