Rhodobacter aestuarii sp. nov., a phototrophic alphaproteobacterium isolated from an estuarine environment

Abstract

An ovoid to rod-shaped, phototrophic, purple non-sulfur bacterium was isolated from a brown-coloured microbial mat from the brackish water of Bhitarkanika mangrove forest, Dangmal, Orissa, India. Cells of strain JA296(T) were Gram-negative and motile, forming chains of four to eight cells. The colour of the cell suspension grown under anaerobic conditions in the light was yellowish green. Bacteriochlorophyll a and the carotenoids spheroidene and spheroidenone of the spirilloxanthin series were present as photosynthetic pigments. The bacterium was a facultative anaerobe and was able to grow photo-organoheterotrophically and chemo-organoheterotrophically. Thiamine was required as a growth factor. C(18 : 1)omega7c was the dominant fatty acid. Internal cytoplasmic membranes were of the vesicular type. Strain JA296(T) did not require NaCl for growth. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA296(T) was most closely related to Rhodobacter capsulatus ATCC 11166(T) (95.5 % sequence similarity) and clustered with species of the genus Rhodobacter of the family Rhodobacteraceae, class Alphaproteobacteria. On the basis of 16S rRNA gene sequence analysis and morphological and physiological characteristics, strain JA296(T) represents a novel species of the genus Rhodobacter, for which the name Rhodobacter aestuarii sp. nov. is proposed; the type strain is JA296(T) (=JCM 14887(T) =CCUG 55130(T)).