Marinobacter alkaliphilus sp. nov., a novel alkaliphilic bacterium isolated from subseafloor alkaline serpentine mud from Ocean Drilling Program Site 1200 at South Chamorro Seamount, Mariana Forearc.

Novel alkaliphilic, mesophilic bacteria were isolated from subseafloor alkaline serpentine mud from the Ocean Drilling Program (ODP) Hole 1200D at a serpentine mud volcano, South Chamorro Seamount in the Mariana Forearc. The cells of type strain ODP1200D-1.5T were motile rods with a single polar flagellum. Growth was observed between 10 and 45-50 degrees C (optimum temperature: 30-35 degrees C, 45-min doubling time), between pH 6.5 and 10.8-11.4 (optimum: pH 8.5-9.0), and between NaCl concentrations of 0 and 21% (w/v) (optimum NaCl concentration: 2.5-3.5%). The isolate was a facultatively anaerobic heterotroph utilizing various complex substrates, hydrocarbons, carbohydrates, organic acids, and amino acids. Nitrate or fumarate could serve as an electron acceptor to support growth under anaerobic conditions. The G+C content of the genomic DNA was 57.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belonged to the genus Marinobacter and was the most closely related to M. aquaeolei strain VT8T and M. hydrocarbonoclasticus strain SP.17T, while DNA-DNA hybridization demonstrated that the new isolate could be genetically differentiated from the previously described species of Marinobacter. Based on the physiological and molecular properties of the new isolate, we propose the name Marinobacter alkaliphilus sp. nov., type strain: ODP1200D-1.5T (JCM12291T and ATCC BAA-889T).