A coccoid, phototrophic purple sulfur bacterium was isolated in pure culture from a mud sample collected from brackish water in the Bhitarkanika mangrove forest of Orissa, India, in a medium containing 2 % NaCl (w/v). This bacterium, strain JA304(T), was Gram-negative and had a requirement for NaCl. Intracellular photosynthetic membranes were of the vesicular type. The colour of the phototrophically grown culture was saddle-brown. Bacteriochlorophyll a and the carotenoid lycopene were present as photosynthetic pigments. Strain JA304(T) was able to grow photolithoautotrophically and could photoassimilate a number of organic substrates. Yeast extract was required for growth of strain JA304(T). The DNA G+C content was 68.1-68.9 mol%. 16S rRNA gene sequence comparisons indicate that the isolate represents a member of the Chromatiaceae within the class Gammaproteobacteria. According to sequence comparison data, strain JA304(T) is positioned distinctly outside the group formed by the four genera Thiocystis, Chromatium, Allochromatium and Thermochromatium, with only 86.7-91.0 % sequence similarity. Distinct morphological, physiological and genotypic differences from these previously described taxa support the classification of this isolate as a representative of a novel species in a new genus, for which the name Thiophaeococcus mangrovi gen. nov., sp. nov. is proposed. The type strain of Thiophaeococcus mangrovi is JA304(T) (=JCM 14889(T) =DSM 19863(T)).