Novel methanotroph diversity evidenced by molecular characterization of particulate methane monooxygenase A (pmoA) genes in a biogas reactor.

The present study for the first time investigated the diversity of methanotrophs in a biogas reactor running on cattle dung by sequence analysis of the "functional" gene, particulate methane monooxygenase A (pmoA). Community structure was determined by operational taxonomic unit (OTU) phylogenetic analyses of 396 clones belonging to pmoA library. On the basis of 95% peptide identity, 396 inferred PmoA peptide sequences were clustered in 22 phylotypes. These OTUS were phylogenetically affiliated to alpha-proteobacteria (5.30% clones) and gamma-proteobacteria (94.7% clones) and were only distantly related to those of known methanotrophs, indicating the existence of unknown methanotrophs involved in aerobic methanotrophy inside the biogas plant. Good's coverage indicated that the present library covered 96.21% of the dominant species that could be cloned from the biogas reactor. The molecular approaches used in this study provided useful description of the microbial community involved in aerobic oxidation of methane.