Imhoffiella gen. nov., a marine phototrophic member of the family Chromatiaceae including the description of Imhoffiella purpurea sp. nov. and the reclassification of Thiorhodococcus bheemlicus Anil Kumar et al. 2007 as Imhoffiella bheemlica comb. nov.

Abstract

A coccoid-shaped phototrophic purple sulfur bacterium, strain AK35T, was isolated from a coastal surface water sample collected from Visakhapatnam, India. Cells were Gram-stain-negative, motile and purple, containing bacteriochlorophyll a and the carotenoid rhodopinal as major photosynthetic pigments. Strain AK35T was able to grow photoheterotrophically and could utilize a number of organic substrates. It was unable to grow photoautotrophically. Strain AK35T was able to utilize sulfide and thiosulfate as electron donors. The main fatty acids present were identified as C16?:?0, C18?:?1?7c, and C16?:?1?7c and/or iso-C15?:?0 2OH (summed feature 3). Strain AK35T contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and six unidentified lipids as polar lipids. The G+C content of the DNA of strain AK35T was 63.1?mol%. 16S rRNA gene sequence comparisons indicated that the isolate represented a member of the family� Chromatiaceae . 16S rRNA gene sequence analysis indicated that strain AK35T is phylogenetically distinctly positioned outside the groups of most members of the genus� Thiorhodococcus , clustered with members of the genera� Marichromatium and� Phaeochromatium , but was most closely related to� Thiorhodococcus bheemlicus with a pairwise sequence similarity of 98.75?%. Based on DNA-DNA hybridization between strain AK35T and� Thiorhodococcus bheemlicus MTCC 8120T a relatedness of 39.46?% was established. Distinct morphological, physiological and genotypic differences from these previously described taxa supported the classification of the new isolate as a representative of a novel species in a new genus, for which the name Imhoffiella purpurea gen. nov., sp. nov. is proposed. The type strain of Imhoffiella purpurea is AK35T (=JCM 18851T=KCTC 15575T=MTCC 12304T). In addition,� Thiorhodococcus bheemlicus is recognized as another species of this genus and transferred to Imhoffiella bheemlica comb. nov.