Aceticlastic and NaCl-Requiring Methanogen 'Methanosaeta pelagica' sp. nov., Isolated from Marine Tidal Flat Sediment

摘要

Acetate is a key compound for anaerobic organic matter degradation, and so far, two genera, Methanosaeta and Methanosarcina, are only contributors for acetate degradation among methanogens. An aceticlastic methanogen, designated strain 03d30qT, was isolated from a tidal flat sediment in Futtsu, Japan. The phylogenetic analyses based on 16S rRNA and mcrA genes revealed that the isolate belonged to the genus Methanosaeta, but the optimal Na+ concentration for growth shifted to marine environments unlike the other known Methanosaeta species. The quantitative estimation by using a real-time PCR indicated that the 16S rRNA gene of the genus Methanosaeta was detected in the sediments and the relative abundance ranged from 3.9% to 11.8% of the total archaeal 16S rRNA genes. Also, the amount of the genus Methanosaeta increased with increasing depth and was much higher than that of the genus Methanosarcina. This is the first report of marine Methanosaeta species, and on the basis of phylogenetic and characteristic studies, the novel species is proposed, "Methanosaeta pelagica" sp. nov., with types strain 03d30qT.