Comparison of thermophilic methanogens from submarine hydrothermal vents

An extremely thermophilic methanogen was isolated from hydrothermal vent sediment (80 degree -120 degree C) collected from the Guaymas Basin, Gulf of California, at a depth of approximately 2000 m. The isolate was a characteristic member of the genus Methanococcus based on its coccoid morphology, ability to produce methane from CO sub(2) and H sub(2), and DNA base composition (31.4 mol% G + C); it is distinguished from previously described extremely thermophilic vent methanogens by its ability to grow and produce methane from formate and in the composition of membrane lipids. The isolate appears to be a close relative of the previously described Methanococcus jannaschii), isolated from the East Pacific Rise hydrothermal vent system. From the frequency of isolation, it appears that extremely thermophilic methanococci are the predominant representatives of the methanogenic archaebacteria occurring at deep sea hydrothermal vents.