Two strains of phototrophic, purple non-sulfur bacteria capable of growing at low temperatures (5 6C) were isolated from the Himalayas. The two strains showed positive phototaxis and grew over a relatively wide temperature range (5-40 6C). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain JA194T clustered with members of the genus Rhodobacter. ) is sufficiently different from other Rhodobacter species to merit its description as the type strain of a novel species, for which the name Rhodobacter megalophilus sp. nov. is proposed.The genus Rhodobacter includes both motile and nonmotile species. Motile species of the genus have a single polar flagellum and those that lack flagellar motility include Rhodobacter veldkampii (Imhoff, 2005), Rba. vinaykumarii (Srinivas et al., 2007c), Rba. changlensis and Rba. ovatus (Srinivas et al., 2008). Rba. changlensis, a phototrophic bacterium from the Indian Himalayan region, was recently described by our group . In the present communication, we propose a novel species of this genus isolated from the Indian Himalayas, which has properties distinct from all other Rhodobacter species based on phenotypic and phylogenetic analysis.
Strain JA194T was isolated from a soil sample collected from Suraj tal near Sarchu [34u 179 N 77 u 589 E, 11 975 feet (3650 m) above sea level], in the Indian Himalayas. Strain JA247 was isolated from a soil sample collected from an army camp located at Kargil, Ladakh [34u 179 N 77 u 559 E, 18 050 feet (5502 m) above sea level], in the Himalayas. Purification of the strains and polyphasic study for their taxonomic characterization were performed as described by Srinivas et al. (2007a). For dendrogram construction, sequences were aligned by using the program CLUSTAL_X (Thompson et al., 1997) and the alignment was corrected manually. Phylogenetic analysis was carried out by using the PHYLIP package, version 3.5 (Felsenstein, 1993). The evolutionary distance matrix was calculated according to the distance model of Jukes & Cantor (1969). The evolutionary tree was constructed by using the neighbour-joining method (Saitou & Nei, 1987) and the resultant tree topologies were evaluated by bootstrap analysis based on 100 resamplings via the SEQBOOT and CONSENSE programs in the PHYLIP package.For metabolome fingerprinting, exponentially growing photoheterotrophic cultures were harvested by centrifugation (15 000 r.p.m. for 15 min for reference strain Rba. sphaeroides DSM 158 T ; 35 000 r.p.m. for 30 min for strains JA194T and JA247) and the resultant pellets were washed Abbreviation: FT-IR, Fourier transform infrared.The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains JA194 T and JA247 are AM421024 and AM421806, respectively.
Phase-contrast micrographs of cells of strain JA194T and FT-IR fingerprint analysis of the endometabolome and lipids of strain JA194 T and Rba. sphaeroides DSM 158 T are available as supplementary material with the online version of this paper.