Culture-Independent Characterization of a Gene Responsible for Nitrogen Fixation in the Symbiotic Microbial Community in the Gut of the Termite Neotermes koshunensis
AUTOR(ES)
Noda, Satoko
FONTE
American Society for Microbiology
RESUMO
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 (encoded by the anf gene) were preferentially transcribed in the termite gut. Expression of the anf gene was further investigated quantitatively under several termite feeding conditions by competitive PCR. The levels of expression of the anf gene were largely congruent with the nitrogen fixation activity displayed by the termite. The amounts of the genomic anf gene in the population showed no significant change, indicating that the level of expression was critical for nitrogen fixation activity. Interestingly, no significant decrease in the expression level was observed when the diet contained molybdenum (Mo), which represses ordinary anf genes. A 3.6-kb DNA region downstream of the anf gene was isolated and found to contain reading frames homologous to anfH, anfD, and anfG of the Bacteria domain which encode subunits of an alternative nitrogenase having no Mo as a cofactor. This DNA region also contained reading frames encoding glnB-like proteins, which is a common feature of the nitrogenase genes of the Archaea domain. These results indicate that the anf group of nitrogenase genes is the most important group of genes responsible for nitrogen fixation in N. koshunensis and that the anf gene possesses novel features with respect to the regulation of its expression and its gene organization.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=91664Documentos Relacionados
- Culture-Independent Analysis of Gut Bacteria: the Pig Gastrointestinal Tract Microbiota Revisited
- Culture-Dependent and Culture-Independent Characterization of Microbial Assemblages Associated with High-Temperature Petroleum Reservoirs
- Phylogenetic Diversity of Nitrogen Fixation Genes in the Symbiotic Microbial Community in the Gut of Diverse Termites
- Culture-Independent Molecular Analysis of Microbial Constituents of the Healthy Human Outer Ear
- Culture-Independent Microbial Community Analysis Reveals that Inulin in the Diet Primarily Affects Previously Unknown Bacteria in the Mouse Cecum