ISOLATION AND CHARACTERIZATION OF METHANOLOBUS-BOMBAYENSIS SP-NOV, A METHYLOTROPHIC METHANOGEN THAT REQUIRES HIGH-CONCENTRATIONS OF DIVALENT-CATIONS

Methanolobus bombayensis B-1(T) (= OCM 438(T)) (T = type strain) was isolated from Arabian Sea sediments obtained near Bombay, India. This strain grew on methylamines, methanol, and dimethyl sulfide, but it did not catabolize H-2-CO2, acetate, or formate. The cells were nonmotile, irregular coccoids (diameter, 1.0 to 1.5 mu m) and occurred singly. Electron micrographs revealed that a cell membrane and a protein cell wall were present. The cells grew fastest at mesophilic temperatures, at a neutral pH, and at salinity levels near the salinity level of the ocean, and they required about 30 mM divalent cations (Mg2+ and Ca2+). The cells grew in mineral medium, but growth was greatly stimulated by yeast extract and peptones. The guanine-plus-cytosine content of the DNA was 39.2 +/- 0.1 mol%. A comparison of 16S rRNA sequences showed that strain B-1(T) was phylogenetically related to Methanolobus vulcani, but the sequences of these organisms differed by 2%.