Nitrogen fixation

1976 ◽  
Vol 274 (934) ◽  
pp. 341-358 ◽  
Keyword(s):  
Nitrogen Fixation ◽  
Metabolic Regulation ◽  
Higher Plants ◽  
Focal Point ◽  
Nitrogenase Activity ◽  
Nitrogen Fixing ◽  
Blue Green Algae ◽  
International Biological Programme ◽  
The 1960S ◽  
Biological Programme

The International Biological Programme served as a focal point for studies on biological nitrogen fixation during the 1960s. The introduction of the acetylene reduction technique for measuring nitrogenase activity in the field led to estimates becoming available of the contribution of lichens, blue-green algae, nodulated non-legumes and bacterial-grass associations, as well as of legumes. Other studies carried out on the physiology and biochemistry of the process led to the eventual purification and characterization of the nitrogenase enzyme. These studies, collectively, provided the springboard for current work, so essential in view of the present energy crisis, on how to increase the use and efficiency of nitrogen-fixing plants, on the metabolic regulation of the nitrogenase enzyme and on the genetics of the nitrogen-fixing process, both in higher plants and in free-living micro-organisms.

Biological and ecological aspects of nitrogen fixation by free-living micro-organisms

1969 ◽  
Vol 172 (1029) ◽  
pp. 367-388 ◽  
Keyword(s):  
Nitrogen Fixation ◽  
Soil Fertility ◽  
Biological Nitrogen Fixation ◽  
Higher Plants ◽  
Symbiotic Association ◽  
Free Living ◽  
Blue Green Algae ◽  
Ecological Aspects ◽  
Micro Organisms ◽  
Biological Nitrogen

Biological nitrogen fixation is a characteristic of certain micro-organisms, which may be free-living or occur in symbiotic association with higher plants. The purpose of this paper is to summarize some of the biological and ecological aspects of nitrogen-fixation by free-living forms. Biochemical aspects have been reviewed in other contributions to this discussion by Drs Wilson, Burris, and Cox & Fay. Nitrogen fixation by heterotrophic micro-organisms has been considered by Jensen (1965); nitrogen fixation by blue-green algae by Fogg & Stewart (1965), and by Stewart (1966, 1969), while Moore (1966) has evaluated the contribution of nitrogen-fixing micro-organisms to soil fertility.

scholarly journals nifH Sequences and Nitrogen Fixation in Type I and Type II Methanotrophs

2001 ◽  
Vol 67 (9) ◽  
pp. 4009-4016 ◽  
Author(s):  
Ann J. Auman ◽  
Catherine C. Speake ◽  
Mary E. Lidstrom
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Freshwater Lake ◽  
Type I ◽  
Type Ii ◽  
Nitrogen Fixing ◽  
Protein Sequence Analysis ◽  
High Identity ◽  
Rice Roots ◽  
Methane Oxidizing Bacteria

ABSTRACT Some methane-oxidizing bacteria (methanotrophs) are known to be capable of expressing nitrogenase and utilizing N2 as a nitrogen source. However, no sequences are available fornif genes in these strains, and the known nitrogen-fixing methanotrophs are confined mainly to a few genera. The purpose of this work was to assess the nitrogen-fixing capabilities of a variety of methanotroph strains. nifH gene fragments from four type I methanotrophs and seven type II methanotrophs were PCR amplified and sequenced. Nitrogenase activity was confirmed in selected type I and type II strains by acetylene reduction. Activities ranged from 0.4 to 3.3 nmol/min/mg of protein. Sequence analysis shows that thenifH sequences from the type I and type II strains cluster with nifH sequences from other gamma proteobacteria and alpha proteobacteria, respectively. The translatednifH sequences from three Methylomonas strains show high identity (95 to 99%) to several published translated environmental nifH sequences PCR amplified from rice roots and a freshwater lake. The translated nifHsequences from the type II strains show high identity (94 to 99%) to published translated nifH sequences from a variety of environments, including rice roots, a freshwater lake, an oligotrophic ocean, and forest soil. These results provide evidence for nitrogen fixation in a broad range of methanotrophs and suggest that nitrogen-fixing methanotrophs may be widespread and important in the nitrogen cycling of many environments.

scholarly journals Distribution of blue-green algae in soils of Chittagong University campus and their nitrogen fixing capacity

1970 ◽  
Vol 37 (1) ◽  
pp. 49-53
Author(s):  
MA Gafur ◽  
Soltana Parvin
Keyword(s):  
Nitrogen Fixation ◽  
Green Algae ◽  
Rice Field ◽  
Maximum Amount ◽  
University Campus ◽  
Nitrogen Fixing ◽  
Batch Cultures ◽  
Blue Green Algae ◽  
Field Soils ◽  
Potential Maximum

Occurrence of blue-green algae in plain land, pond side, hilly area and dry rice field soils of Chittagong University Campus and N2 fixation of some of them have been studied. Twenty four species under 20 genera were identified and their number varied from 0.11×104/g to 2.8×104/g soil. Anabaena oryzae, Calothrix sp., Cylindrospermum majus and Hapalosiphon hibernicus and Nostoc spongiaeforme were selected for their nitrogen fixing potential. Maximum amount of total nitrogen was recorded in Nostoc spongiaeforme followed by Hapalosiphon hibernicus, Cylindrospermum majus, Anabaena oryzae and Calothrix sp. after 30 days growth in batch cultures.   Key words: BGA, Distribution, Nitrogen fixation doi:10.3329/bjb.v37i1.1563 Bangladesh J. Bot. 37(1): 49-53, 2008 (June)

scholarly journals Medicago truncatulaFerroportin2 mediates iron import into nodule symbiosomes

2019 ◽  
Author(s):  
Viviana Escudero ◽  
Isidro Abreu ◽  
Manuel Tejada-Jiménez ◽  
Elena Rosa-Núñez ◽  
Julia Quintana ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Specific Gene ◽  
Nitrogen Fixing ◽  
Loss Of Function ◽  
Model Legume ◽  
Endosymbiotic Bacteria ◽  
Signal Transduction Proteins ◽  
Iron Delivery

ABSTRACTIron is an essential cofactor for symbiotic nitrogen fixation. It is required by many of the enzymes facilitating the conversion of N2into NH4+by endosymbiotic bacteria living within root nodule cells, including signal transduction proteins, O2homeostasis systems, and nitrogenase itself. Consequently, host plants have developed a transport network to deliver essential iron to nitrogen-fixing nodule cells. Model legumeMedicago truncatula Ferroportin2(MtFPN2) is a nodule-specific gene that encodes an iron-efflux protein. MtFPN2 is located in intracellular membranes in the nodule vasculature, and in the symbiosome membranes that contain the nitrogen-fixing bacteria in the differentiation and early-fixation zones of the nodules. Loss-of-function ofMtFPN2leads to altered iron distribution and speciation in nodules, which causes a reduction in nitrogenase activity and in biomass production. Using promoters with different tissular activity to driveMtFPN2expression inMtFPN2mutants, we determined that MtFPN2-facilitated iron delivery across symbiosomes is essential for symbiotic nitrogen fixation, while its presence in the vasculature does not seem to play a major role in in the conditions tested.

A comparison of carbon source utilization for growth and nitrogenase activity in two Frankia isolates

1986 ◽  
Vol 32 (4) ◽  
pp. 353-358 ◽  
Author(s):  
Mary F. Lopez ◽  
Patricia Young ◽  
John G. Torrey
Keyword(s):  
Nitrogen Fixation ◽  
Carbon Source ◽  
Oxygen Uptake ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Carbon Sources ◽  
Alnus Rubra ◽  
Nitrogen Fixing ◽  
Pure Cultures

The carbon source requirements for the growth and nitrogen fixation of two morphologically distinct Frankia isolates were examined. Isolate ArI3 (from Alnus rubra) grew well on propionate, malate, acetate, and trehalose, and isolate CcI2 (from Casuarina cunninghamiana) grew best on pyruvate, acetate, and propionate. In general, the same carbon sources that supported growth supported both the development of vesicles and nitrogenase activity in long-term induction experiments in both isolates. However, ArI3 cultures induced on proprionate had 7 to 26 times the activity of other carbon sources and ArI3 cultures induced on acetate did not develop any detectable acetylene reduction. In a parallel set of experiments, cultures of both isolates were induced for nitrogenase activity on propionate and the resulting nitrogen fixing cultures were washed free of the organic acid by centrifugation. The washed cultures were incubated in the presence of various carbon sources to determine the ability of a particular substrate to supply energy directly for nitrogen fixation when vesicles and nitrogenase were already present. As was observed in the long-term induction experiments, pyruvate, propionate, and acetate supported the greatest activity in CcI2. Succinate and malate supported the greatest activity in ArI3, and propionate had very little stimulation of acetylene reduction. The reason for the lack of stimulation by propionate for washed cells of ArI3 was unclear but may have been due to toxic concentrations of the organic acid. In an attempt to compare the carbon utilization of ArI3 in pure culture with that in the alder symbiosis, oxygen uptake in the presence of various carbon sources of vesicles clusters isolate from Alnus rubra nodules inoculated with ArI3 was compared with the oxygen uptake of nitrogen-fixing pure cultures of ArI3. The oxygen uptake of the isolated vesicle clusters was stimulated by sucrose, trehalose, and glucose, but not by a variety of organic acids. In comparison, nitrogen-fixing pure cultures of ArI3 readily oxidized sugars and organic acids.

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