Isolates of the toxic, N(2)-fixing species Cylindrospermopsis raciborskii from various geographic locations were analyzed with respect to their genetic diversity based on the nifH and cpcBA-IGS genes. Gene sequences clustered according to their geographic origin, with the nifH sequences separating into European, Australian, and American groups and the cpcBA-IGS sequences separating into America...

Based on partial 16S sequences, we previously described a novel group of nonsymbiotic, acetylene reduction activity-positive actinomycetes which were isolated from surface-sterilized roots of Casuarina equisetifolia growing in Mexico. An amplified rRNA restriction analysis confirmed that these actinomycetes are distinct from Frankia, a finding substantiated by a 16S rRNA gene phylogenetic analy...

Spirochetes from termite hindguts and freshwater sediments possessed homologs of a nitrogenase gene (nifH) and exhibited nitrogenase activity, a previously unrecognized metabolic capability in spirochetes. Fixation of 15-dinitrogen was demonstrated with termite gut Treponema ZAS-9 and free-living Spirochaeta aurantia. Homologs of nifH were also present in human oral and bovine ruminal treponeme...

In this paper, we report the cloning and characterization of three Paenibacillus azotofixans DNA regions containing genes involved in nitrogen fixation. Sequencing analysis revealed the presence of nifB1H1D1K1 gene organization in the 4,607-bp SacI DNA fragment. This is the first report of linkage of a nifB open reading frame upstream of the structural nif genes. The second (nifB2H2) and third ...

The structural genes for nitrogenase, nifK, nifD, and nifr-r, are crucial for nitrogen fixation. Previous phylogenetic analysis of the amino acid sequence of nifH suggested that this gene had been horizontally transferred from a proteobacterium to the gram-positive/cyanobacterial clade, although the confounding effects of paralogous comparisons made interpretation of the data difficult. An addi...

Biological nitrogen fixing is an important source of nitrogen input in the natural ecological restoration of mine wastelands. The diversity of nifH genes in tailings samples under different plant communities in Yangshanchong and Tongguanshan wastelands in Tongling, was analyzed using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) approach. The nitrogen-fixing micro...

Expression of the nitrogen fixation gene, nifH, in the gut of the termite Neotermes koshunensis was characterized without cultivation. nifH cDNA was directly amplified from mRNA of the mixed microbial population in the gut by reverse transcription (RT)-PCR. Analyses of the RT-PCR products revealed that, among the diverse nifH sequences, only a few corresponding to an alternative nitrogenase (en...