Rhodothermus obamensis sp nov, a modern lineage of extremely thermophilic marine bacteria

A novel extremely thermophilic bacterium was isolated from a shallow marine hydrothermal vent environment (depth, 22 m) in Tachibana Bay, Nagasaki Prefecture, Japan. The cells of this organism were gramnegative rods. Growth occurred at temperatures between 50 and 85 degrees C (optimum temperature, 80 degrees C; doubling time at optimum temperature, 90 min), at pH 5.5 and 9.0 (optimum pH, 7.0), and in the presence of 1 and 5% NaCl (optimum NaCl concentration, 3%), The ne cv isolate was an aerobic heterotroph which utilized the following compounds as sole energy and carbon sources: yeast extract, peptone, starch, casein, Casamino Acids, a variety of sugars, some carboxylic acids, and amino acids. As determined by a sequence analysis of the 16S rRNA, the new isolate belongs to the genus Rhodothermus and represents a modern lineage of extreme thermophiles within the domain Bacteria. On the basis of the physiological and molecular properties of the new isolate, we describe a new species, Rhodothermus obamensis. The type strain of R. obamensis is strain OKD7 (= JCM 9785).