Methanosarcina baltica, sp. nov., a novel methanogen isolated from the Gotland Deep of the Baltic Sea

Abstract.

A novel methanogen, Methanosarcina baltica GS1-A^T, DSM 14042, JCM 11281, was isolated from sediment at a depth of 241 m in the Gotland Deep of the Baltic Sea. Cells were irregular, monopolar monotrichous flagellated cocci 1.5–3 µm in diameter often occurring in pairs or tetrads. The catabolic substrates used included methanol, methylated amines, and acetate, but not formate or H₂/CO₂. Growth was observed in a temperature range between 4° and 27°C with an optimum at 25°C. The doubling time with methanol as substrate was 84 h at 25°C, 120 h at 9°C, and 167 h at 4°C. The doubling time with acetate as substrate was 252 h at 25°C and 425 h at 20°C. After the transfer of methanol-grown cultures, long lag phases were observed that lasted 15–20 days at 25°C and 25 days at 4°–9°C. The NaCl optimum for growth was 2%–4%, and the fastest growth occurred within a pH range of 6.5–7.5. Analysis of the 16S rDNA sequence revealed that the strain was phylogenetically related to Methanosarcina. The sequence similarity to described species of <95.7% and its physiological properties distinguished strain GS1-A^T from all described species of the genus Methanosarcina.