Isolation and Characterization of Methanothermobacter crinale sp. nov., a Novel Hydrogenotrophic Methanogen from the Shengli Oil Field

Abstract

ABSTRACT Syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis is an alternative methanogenic pathway in certain thermophilic anaerobic environments such as high-temperature oil reservoirs and thermophilic biogas reactors. In these environments, the dominant thermophilic methanogens were generally related to uncultured organisms of the genus Methanothermobacter . Here we isolated two representative strains, Tm2 T and HMD, from the oil sands and oil production water in the Shengli oil field in the People's Republic of China. The type strain, Tm2 T , was nonmotile and stained Gram positive. The cells were straight to slightly curved rods (0.3 μm in width and 2.2 to 5.9 μm in length), but some of them possessed a coccal shape connecting with the rods at the ends. Strain Tm2 T grew with H 2 -CO 2 , but acetate is required. Optimum growth of strain Tm2 T occurred in the presence of 0.025 g/liter NaCl at pH 6.9 and a temperature of 65°C. The G+C content of the genomic DNA was 40.1 mol% ± 1.3 mol% (by the thermal denaturation method) or 41.1 mol% (by high-performance liquid chromatography). Analysis of the 16S rRNA gene sequence indicated that Tm2 T was most closely related to Methanothermobacter thermautotrophicus ΔH T and Methanothermobacter wolfeii VKM B-1829 T (both with a sequence similarity of 96.4%). Based on these phenotypic and phylogenic characteristics, a novel species was proposed and named Methanothermobacter crinale sp. nov. The type strain is Tm2 T (ACCC 00699 T = JCM 17393 T ).