Thiomonas bhubaneswarensis sp. nov., an obligately mixotrophic, moderately thermophilic, thiosulfate-oxidizing bacterium

Abstract

A novel aerobic, obligately mixotrophic, moderately thermophilic, thiosulfate-oxidizing bacterium, S10^T, was isolated from hot-spring sediment samples collected from Atri, Bhubaneswar, India. The cells of this isolate stained Gram-negative and were strictly aerobic, non-sporulating, rod-shaped and motile with a single polar flagellum. Strain S10^T was positive for oxidase and catalase activities. It was capable of utilizing thiosulfate under mixotrophic growth conditions. Mixotrophic growth was observed at pH 6.0-8.5 and 25-45 °C; optimum growth occurred at pH 7.5-8.0 and 30-37 °C. The major cellular fatty acids were C_12:0 3-OH, C_16:1ω7c, C_16:0, C_17:0 cyclo, C_18:1ω7c and C19:0 cyclo ω8c. The DNA G+C content of strain S10^T was 64.8 mol%. 16S rRNA gene sequence analysis indicated that the bacterium clustered within the radiation of the genus Thiomonas and showed 98.0% similarity with Thiomonas perometabolis ATCC 23370^T and Thiomonas intermedia ATCC 15466^T. However, DNA-DNA reassociation values of strain S10^T with Thiomonas perometabolis JCM 20426^T and Thiomonas intermedia JCM 20425^T, its nearest phylogenetic relatives, were 46 and 39%, respectively. On the basis of phenotypic, physiological and chemotaxonomic properties, 16S rRNA gene sequence analysis and DNA-DNA reassociation studies, it is proposed that strain S10^T represents a novel species of the genus Thiomonas, Thiomonas bhubaneswarensis sp. nov.; the type strain is S10^T (=DSM 18181^T =JCM 14806^T).