Characteristics of Microbial Community Structure at the Seafloor Surface of the Nankai Trough

Phylogenetic analysis of bacteria and archaea on the seafloor surface of the Nankai Trough was conducted. DNA was extracted from a total of 14 samples (2 samples from 1 methane seep area and 12 samples from 12 general seafloor areas) and analyzed, targeting the 16S rRNA gene. As a result of the phylogenetic analysis of bacteria, 1 clone was found to have 96% homology with the 16S rRNA gene sequence of Methylomicrobium alcaliphilum, a halophilic methane-oxidizing bacterium, in a sample taken from the methane seep area. However, overall, no characteristic pattern was observed in the bacterial community structure between the methane seep area and the general seafloor. In contrast, in archaea, the genus Methanosarcina was predominantly detected in the samples from the methane seep area. Among them, many sequences that were closely related to anaerobic methane-oxidizing archaea, which perform anaerobic methane oxidation, were detected.