Description of a phototrophic bacterium, Thiorhodococcus alkaliphilus sp. nov

Abstract

Strain JA878T was purified from a photoheterotrophic enrichment obtained from a sediment sample of a brown pond near Nari Salt Pan, Bhavnagar, Gujarat, India. Cells of the isolate were coccoid, motile by means of single polar flagellum and Gramstain- negative. The internal photosynthetic membrane architecture was vesicular. Strain JA878T contained bacteriochlorophyll a and spirilloxanthin series of carotenoids with rhodopin ( > 85 %) as the major component. Strain JA878T grew optimally at pH 10–11, and had no requirement for NaCl (tolerated up to 6 %, w/v) or vitamins for growth. C16 : 1ω7c/C16 : 1ω6c, C18 : 1ω7c/C18 : 1 ω6c and C16 : 0 were identified as the major fatty acids ( > 10 %). Phosphatidylglycerol, phosphatidylethanolamine, aminophospholipid and an unknown polar lipid were identified. Q8 was the predominant quinone system in strain JA878T. The DNA G+C content was 62.4 mol%. Highest 16S rRNA gene sequence similarity through EzTaxon-based BLAST analysis of strain JA878T was found with the type strains of Thiorhodococcus fuscus (99 %), Thiorhodococcus kakinadensis (98.6 %), Thiohalobacter thiocyanaticus (98.4 %), Thiophaeococcus fuscus (97.3 %) and other members of the class Gammaproteobacteria ( < 97.3 %), revealing a close affiliation to the genera Thiorhodococcus, Thiohalobacter and Thiophaeococcus. However, the phylogenetic treeing firmly placed the strain in the genus Thiorhodococcus. Phenotypic and chemotaxonomic evidence supported the affiliation of strain JA878T to the genus Thiorhodococcus and not to Thiohalobacter, Thiophaeococcus or other known genera of Chromatiaceae. Distinct physiological, genotypic and chemotaxonomic differences indicate that strain JA878T represents a novel species of the genus Thiorhodococcus, for which the name Thiorhodococcus alkaliphilus sp. nov. is proposed. The type strain is JA878T (=KCTC 15531T=JCM 31245T).