Thermus kawarayensis sp. nov., a new member of the genus Thermus, isolated from Japanese hot springs.

A long-rod-shaped thermophilic microorganism, strain KW11, was isolated from a hot springs located in the Kawarayu, Gunma, Japan. Cloning and preliminary sequence analysis of 16S rDNA showed that this isolate belongs to the genus Thermus. The cells were 10-20 microm long, about 0.8 microm in diameter, and produced no pigment in contrast with most of the Thermus species previously reported. KW11 was an aerobic heterotroph and grew at temperatures ranging from 40-73 degrees C, with optimal growth occurring at 68 degrees C. The pH range for growth was from 5.8-8.9, with optimal growth around pH 7. KW11 was sensitive to ampicillin, penicillin G, kanamycin, and streptomycin. The G+C content of DNA was 69 mol%. The main fatty acids were 16:0 (52.9%), iso-15:0 (22.1%), and iso-17:0 (15.6%). The 16S rDNA sequence of KW11 showed 96.0, 95.8, and 95.4% similarity with the sequences of T. aquaticus, T. igniterrae, and T. thermophilus, respectively, and less than 95% with other Thermus species. The physiological differences and phylogenetic evidence indicated that strain KW11 represents T. kawarayensis, a novel species of the genus Thermus. The type strain is isolate KW11T (JCM12314, DSM16200).