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.

摘要

A coccoid-shaped phototrophic purple sulfur bacterium, strain AK35(T), 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 AK35(T) was able to grow photoheterotrophically and could utilize a number of organic substrates. It was unable to grow photoautotrophically. Strain AK35(T) was able to utilize sulfide and thiosulfate as electron donors. The main fatty acids present were identified as C-16 : 0, C-18 : 1 omega 7c, and C-16 (: 1)omega 7c and/or iso-C-15 : 0 2OH (summed feature 3). Strain AK35(T) contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and six unidentified lipids as polar lipids. The G+ C content of the DNA of strain AK35(T) 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 AK35(T) 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 AK35(T) and Thiorhodococcus bheemlicus MTCC 8120(T) 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 AK35(T) (= JCM 18851(T) = KCTC 15575(T) = MTCC 12304(T)). In addition, Thiorhodococcus bheemlicus is recognized as another species of this genus and transferred to Imhoffiella bheemlica comb. nov.