Marichromatium bheemlicum sp. nov., a non-diazotrophic, photosynthetic gammaproteobacterium from a marine aquaculture pond

Abstract

A rod-shaped, phototrophic, purple sulfur bacterium, strain JA124T, was isolated in pure culture from a marine aquaculture pond, located near Bhimunipatnam, in a medium that contained 3% NaCl (w/v). Strain JA124T is a Gram-negative, motile rod with a single polar flagellum. Strain JA124T has a requirement for NaCl, with optimum growth at 1.5-8.5%, and tolerates up to 11% NaCl. Intracellular photosynthetic membranes are of the vesicular type. Bacteriochlorophyll a and probably carotenoids of the spirilloxanthin series are present as photosynthetic pigments. Strain JA124T was able to utilize sulfide, sulfate, thiosulfate, sulfite, thioglycollate and cysteine as sulfur sources. Strain JA124T was able to grow photolithoautotrophically, photolithoheterotrophically and photo-organoheterotrophically. Chemotrophic and fermentative growth could not be demonstrated. Strain JA124T lacks diazotrophic growth and acetylene reduction activity. Pyridoxal phosphate is required for growth. During growth on reduced sulfur sources as electron donors, sulfur is deposited intermediately as a number of small granules within the cell. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA124T clusters with species of the genus Marichromatium belonging to the class Gammaproteobacteria. The highest sequence similarities of strain JA124T were found with the type strains of Marichromatium indicum (98%), Marichromatium purpuratum (95%) and Marichromatium gracile (93%) However, DNA-DNA hybridization with Marichromatium indicum DSM 15907T revealed relatedness of only 65% with strain JA124T. The DNA base composition of strain JA124T was 67 mol% G+C (by HPLC). Based on 16S rRNA gene sequence analysis, morphological and physiological characteristics and DNA-DNA hybridization studies, strain JA124T (=ATCC BAA-1316T=JCM 13911T) is sufficiently different from other Marichromatium species to merit its description as the type strain of a novel species, Marichromatium bheemlicum sp. nov. © 2007 IUMS.