Rhodovulum marinum sp. nov., a novel phototrophic purple non-sulfur alphaproteobacterium from marine tides of Visakhapatnam, India

A yellowish-brown bacterium was isolated from enrichment cultures inoculated with seawater samples from the eastern coast of India (Visakhapatnam) under photoheterotrophic conditions. Enrichment and isolation in a medium containing 2 % NaCl (w/v) yielded strain JA128(T), which has ovoid to rod-shaped cells, also forms chains and is non-motile. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA128(T) clusters with the Alphaproteobacteria and the sequence similarity with its closest relatives, Rhodovulum iodosum and Rhodovulum sulfidophilum, was 95 %. Strain JA128(T) contained vesicular intracytoplasmic membranes, bacteriochlorophyll a and carotenoids of the spheroidene series. Strain JA128(T) was mesophilic, slightly acidophilic, slightly halophilic and grew photoheterotrophically with a number of organic compounds as carbon source and electron donor. It was unable to grow photoautotrophically, chemoautotrophically or by fermentative modes. It did not utilize sulfide, thiosulfate or hydrogen as electron donors. Thiamine was required as a growth factor. Based on the 16S rRNA gene sequence analysis, morphological and physiological characteristics, strain JA128(T) was significantly different from other species of the genus Rhodovulum and was recognized as a novel species for which the name Rhodovulum marinum sp. nov. is proposed. The type strain is JA128(T) (=ATCC BAA 1215(T)=CCUG 52183(T)=JCM 13300(T)).