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 6C; optimum growth occurred at pH 7.5-8.0 and 37-42 6C. The major cellular fatty acids were C 14 : 0 3-OH, C 18 : 0 3-OH, Exploration of bacterial species in hot springs is of importance owing to the intriguing biogeochemistry and extreme conditions of these environments. The vast majority of bacterial species belonging to the most recent lines of descent, such as the Proteobacteria, are mesophilic, although slightly thermophilic, moderately thermophilic and even extremely thermophilic species have been described from these bacterial lineages. The Alphaproteobacteria includes many mesophilic species, but also a few slightly thermophilic or moderately thermophilic species, namely Rubritepida flocculans , 1975), but the micro-organisms present in these environments have been little studied (but see Ghosh et al., 2003). This paper describes a bacterial strain (HT4 T ) isolated from a hot spring located at Athamallik, Orissa, India. Based on the results of the present polyphasic taxonomic study, strain HT4T is considered to represent a novel species of the genus Chelatococcus.The hot spring at Athamallik is situated at 80 m above sea level. It has a series of outlets within a radius of 70 m. The water temperature at the main outlet was 56 u C and in the surrounding areas ranged from 43 to 50 u C. The pH of sediment samples taken for analysis was 7.4. Sediment samples were transported to the laboratory without temperature control and subsequently transferred into 250-ml conical flasks containing 50 ml nutrient broth (Difco) and incubated on a shaker (ISF-1-V; Adolf Kuhner AG) at 200 r.p.m. and 45 u C. After 2 days incubation, the contents of the flasks were serially diluted and plated onto nutrient agar medium (Difco) and incubated at 37 u C for 4 days. Several colonies that developed at 37 u C were picked and purified by repeated streaking on the same medium. A colony with a mucoid cream colour was selected for further analysis; this was designated strain HT4 T .
Colonies of strain HT4T grown on nutrient agar were circular, 1.5-2.5 mm in diameter, mucoid and smooth.The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain HT4T is DQ322070.A supplementary table detailing the fatty acid composition of strain HT4T and other members of the genus Chelatococcus is available with the online version of this paper.