Thermus arciformis sp nov., a thermophilic species from a geothermal area

Two aerobic, Gram-negative, non-motile, non-sporulating, yellow-pigmented bacteria, strains TH92(T) and TH91, were isolated from a hot spring located in Laibin, Guangxi, in the south-eastern geothermal area of China. The isolates grew at 40-77 degrees C (optimally at 70 degrees C) and at pH 6.0-9.5 (optimally at pH 7.5-8.0). Phylogenetic analysis of 16S rRNA gene sequences and levels of DNA-DNA relatedness together indicated that the new isolates represented a novel species of the genus Thermus with closest affinity to Thermus aquaticus, Thermus igniterrae and Thermus thermophilus. Compared with their closest relatives, strains TH92(T) and TH91 were able to assimilate a wider range of carbohydrates, amino acids and organic acids as sole carbon sources for growth, such as lactose and melibiose. The new isolates had lower combined levels of C-16:0 and iso-C-16:0 compared with their closest relatives. On the basis of polyphasic taxonomic characterization, strains TH92(T) and TH91 are considered to represent a single novel species of the genus Thermus, for which the name Thermus arciformis sp. nov. is proposed. The type strain is TH92(T) (=CGMCC 1.6992(T) =JCM 15153(T)).