Thiophaeococcus fuscus sp. nov., isolated from a lagoon.

A brown-coloured bacterium, designated strain JA633(T), was purified from a photoheterotrophic enrichment culture obtained from black sand of a lagoon. Cells of strain JA633(T) were coccoid-spherical, Gram-stain-negative and motile by means of polar flagella. Strain JA633(T) had an obligate requirement for NaCl and could tolerate up to 4% (w/v) NaCl. Internal photosynthetic membranes were present as vesicles. Photo-organoheterotrophy was the only growth mode observed. Strain JA633(T) contained bacteriochlorophyll a and a major (>85%) unidentified carotenoid of the spirilloxanthin series. Thiamine and p-aminobenzoic acid were required for growth. Major fatty acids were C(18 : 1)ω7c/C(18 : 1)ω6c, C(16 : 0) and C(16 : 1)ω7c/C(16 : 1)ω6c. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphotidylcholine and an unknown aminophospholipid were the major polar lipids in strain JA633(T). The DNA G+C content of strain JA633(T) was 64.5 mol%. Strain JA633(T) shared highest 16S rRNA gene sequence similarity with the type strains of Thiorhodococcus kakinadensis (96.9%), Thiophaeococcus mangrovi (96.3%) and Thiorhodococcus bheemlicus (96.2%), which belonged to the class Gammaproteobacteria. However, phylogenetic analysis based on 16S rRNA gene sequences showed that strain JA633(T) formed a separate clade along with Thiophaeococcus mangrovi JA304(T) whereas the members of the genus Thiorhodococcus remained as two distinct phylogenetic lineages. Based on morphological, physiological, chemotaxonomic and molecular evidence, strain JA633(T) was significantly different from the type strain of Thiophaeococcus mangrovi of the family Chromatiaceae. It is thus proposed that the strain be classified as a representative of a novel species, for which the name Thiophaeococcus fuscus sp. nov. is proposed. The type strain is JA633(T) ( = KCTC 15337(T) = NBRC 109958(T)).