Complete genome sequence of the hyperthermophilic methanogen Methanocaldococcus bathoardescens JH146(T) isolated from the basalt subseafloor.

Methanocaldococcus bathoardescens JH146(T) is a hyperthermophilic and obligate hydrogenotrophic methanogen isolated from low-temperature (26 °C) hydrothermal vent fluid at Axial Seamount in the northeastern Pacific Ocean. It is most closely related to the N2-fixing methanogen Methanocaldococcus sp. FS406-22; however, they differ in that JH146 cannot fix N2 or reductively assimilate nitrate. In this study, we present the complete genome sequence of strain JH146(T) (1,607,556 bp) with its 1635 protein coding genes, and 41 RNA genes. Our analysis focuses on its methane production via the acetyl-CoA pathway and its deleted gene clusters related to nitrogen assimilation. This study extends our understanding of methanogenesis at high temperatures and the impact of these organisms on the biogeochemistry of subseafloor hydrothermal environments and the deep sea.