A moderately thermophilic bacterial strain (HT4(T)) isolated from a hot spring sediment was characterized phenotypically and phylogenetically. Cells were Gram-negative, aerobic, non-sporulating, rod-shaped and motile by means of a single polar flagellum. Both oxidase and catalase activities were positive. Heterotrophic growth was observed at pH 6.0-8.5 and at 20-50 degrees C; optimum growth occurred at pH 7.5-8.0 and 37-42 degrees C. The major cellular fatty acids were C( 14 : 0) 3-OH, C(18 : 0) 3-OH, C( 18 : 1) 2-OH, C(18 : 1)omega 7c and C(19 : 0) cyclo omega8 c. The DNA G+C content of strain HT4(T) was 67.8 mol%. 16S rRNA gene sequence analysis indicated that strain HT4(T) clustered within the radiation of the genus Chelatococcus and showed 99.0 % similarity with Chelatococcus daeguensis CCUG 54519(T) and 96 % similarity with Chelatococcus asaccharovorans DSM 6462(T). However, levels of DNA-DNA relatedness between strain HT4(T) and Chelatococcus daeguensis CCUG 54519(T) and Chelatococcus asaccharovorans DSM 6462(T) were 52 and 20%, respectively. On the basis of the phenotypic, physiological and chemotaxonomic data, 16S rRNA gene sequence analysis and DNA-DNA hybridization results, strain HT4(T) is considered to represent a novel species of the genus Chelatococcus, for which the name Chelatococcus sambhunathii sp. nov. is proposed. The type strain is HT4(T) (=DSM 18167(T)=JCM 14988(T)).