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At least 505 records · Page 28Linked to original sources
PubMed2004

A comparative study on phyllosphere nitrogen fixation by newly isolated Corynebacterium sp. & Flavobacterium sp. and their potentialities as biofertilizer.

A number of nitrogen fixing bacteria has been isolated from forest phyllosphere on the basis of nitrogenase activity. Among them two best isolates are selected and identified as Corynebacterium sp. AN1 & Flavobacterium sp. TK2 able to reduce 88 and 132 n mol of acetylene (10(8)cells(-1)h(-1)) respectively. They were grown in large amount and sprayed on the phyllosphere of maize plants as a substitute for nitrogenous fertilizer. Marked improvements in growth and total nitrogen content of the plant have been observed by the application of these nitrogen-fixing bacteria. An average 30-37% increase in yield was obtained, which is nearer to chemical fertilizer treatment. Comparatively better effect was obtained by application of Flavobacterium sp.

Corynebacterium↗
PubMed2006

Modeling the dynamic regulation of nitrogen fixation in the cyanobacterium Trichodesmium sp.

A physiological, unbalanced model is presented that explicitly describes growth of the marine cyanobacterium Trichodesmium sp. at the expense of N(2) (diazotrophy). The model involves the dynamics of intracellular reserves of carbon and nitrogen and allows the uncoupling of the metabolism of these elements. The results show the transient dynamics of N(2) fixation when combined nitrogen (NO(3)(-), NH(4)(+)) is available and the increased rate of N(2) fixation when combined nitrogen is insufficient to cover the demand. The daily N(2) fixation pattern that emerges from the model agrees with measurements of rates of nitrogenase activity in laboratory cultures of Trichodesmium sp. Model simulations explored the influence of irradiance levels and the length of the light period on fixation activity and cellular carbon and nitrogen stoichiometry. Changes in the cellular C/N ratio resulted from allocations of carbon to different cell compartments as demanded by the growth of the organism. The model shows that carbon availability is a simple and efficient mechanism to regulate the balance of carbon and nitrogen fixed (C/N ratio) in filaments of cells. The lowest C/N ratios were obtained when the light regime closely matched nitrogenase dynamics.

Carbon↗
PubMed1971

Transduction of the nitrogen-fixation genes in Klebsiella pneumoniae.

The bacteriophage P1 infects and functions as a generalized transducing phage for nitrogen-fixing strains of the coliform bacterium Klebsiella pneumoniae. Bacterial mutants (nif(-)) unable to grow on molecular nitrogen as a nitrogen source were found to be deficient in nitrogenase activity as assayed by the conversion of acetylene to ethylene. These mutants regained normal nitrogenase activity and the ability to grow on N(2) after transduction with lysates of P1 phage prepared from wild-type bacteria. Transductional analysis with P1 revealed that several nif genes are located on the genetic linkage map of Klebsiella near the histidine operon.

Anaerobiosis↗
PubMed1988

Identification and mapping of nitrogen fixation genes of Rhodobacter capsulatus: duplication of a nifA-nifB region.

Rhodobacter capsulatus mutants unable to fix nitrogen were isolated by random transposon Tn5 mutagenesis. The Tn5 insertion sites of 30 Nif- mutants were mapped within three unlinked chromosomal regions designated A, B, and C. The majority of Tn5 insertions (21 mutants) map within nif region A, characterized by two ClaI fragments of 2.5 and 25 kilobases (kb). The 17-kb ClaI fragment of nif region B contains six nif::Tn5 insertions, and the three remaining mutations are located on a 32-kb ClaI fragment of nif region C. Hybridization experiments using all 17 Klebsiella pneumoniae nif genes individually as probes revealed homology to nifE, nifS, nifA, and nifB in nif region A. The nifHDK genes were localized in nif region B. About 2 kb away from this operon, a second copy of the DNA fragments homologous to nifA and nifB, originally found in nif region A, was identified.

Chromosome Mapping↗
PubMed1994

Identification of a gene encoding a thioredoxin-like product necessary for cytochrome c biosynthesis and symbiotic nitrogen fixation in Rhizobium leguminosarum.

A Tn5-induced mutant of Rhizobium leguminosarum bv. viciae could not form nitrogen-fixing nodules on pea or vetch because of a lesion in electron transport to oxygen. The mutant lacked spectroscopically detectable cytochromes c and aa3. No proteins containing c-type cytochrome could be identified in the mutant by heme staining of proteins fractionated on polyacrylamide gels, indicating that the mutant was defective in maturation of all c-type cytochromes. The Tn5 mutation was determined to be located in a gene that was called cycY. The cycY gene product is homologous to the thioredoxin-like protein HelX involved in the assembly of c-type cytochromes in Rhodobacter capsulatus and to an open reading frame from a Bradyrhizobium japonicum gene cluster containing other genes involved in cytochrome c biogenesis. Our observations are consistent with CycY functioning as a thioredoxin that reduces cysteine residues in apocytochromes c before heme attachment.

Amino Acid Sequence↗