Rhodobium gokarnense sp. nov., a novel phototrophic alphaproteobacterium from a saltern

Abstract

A pink-pigmented, phototrophic, purple nonsulfur bacterium, strain JA173(T), was isolated in pure culture from a saltern in Gokarna, India, in a medium containing 2 % (w/v) NaCl. Strain JA173(T) was a non-motile Gram-negative rod that multiplied by budding. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain JA173(T) clusters with the class Alphaproteobacteria; highest sequence similarity (98 %) was to the type strain of Rhodobium orientis and 94 % similarity was observed to the 16S rRNA gene sequence of the type strain of Rhodobium marinum. However, DNA-DNA hybridization with R. orientis DSM 11290(T) revealed a relatedness value of only 35.1 % with strain JA173(T). Strain JA173(T) contained lamellar internal membranes, bacteriochlorophyll a and carotenoids of the spirilloxanthin series. Strain JA173(T) had an obligate requirement for NaCl (optimum growth at 2-6 %, w/v) and grew photoheterotrophically with a number of organic compounds as carbon source or electron donor. Photoautotrophic, chemoautotrophic and fermentative growth could not be demonstrated. Yeast extract was required for growth. Based on 16S rRNA gene sequence analysis, DNA-DNA hybridization data and morphological and physiological characteristics, strain JA173(T) is sufficiently different from other species of the genus Rhodobium to be recognized as a representative of a novel species, Rhodobium gokarnense sp. nov. The type strain is JA173(T) (=ATCC BAA-1215(T)=DSM 17935(T)=JCM 13532(T)).