Thioflavicoccus mobilis gen. nov., sp. nov., a novel purple sulfur bacterium with bacteriochlorophyll b.

A novel phototrophic purple sulfur bacterium was isolated from a flat, laminated microbial mat in a salt marsh near Woods Hole, Massachusetts, USA. The cells were monotrichously flagellated motile cocci with internal photosynthetic membranes of the tubular type. The main photosynthetic pigments were bacteriochlorophyll b and the carotenoid 3,4,3',4'-tetrahydrospirilloxanthin. The marine bacterium showed optimal growth in the presence of 2% salts. It was obligately phototrophic and strictly anaerobic. It grew photoautotrophically and photoassimilated acetate, pyruvate and ascorbate as the only organic substrates. In the presence of sulfide, elemental sulfur globules were formed inside the cells. Elemental sulfur was further oxidized to sulfate. The DNA base composition of the new bacterium was 66.5 mol% G+C. The 16S rDNA nucleotide sequence was most similar to strains of Thiococcus pfennigii, there being approximately 92-93% sequence similarity. The new bacterium is described as a new species and a new genus, and the name Thioflavicoccus mobilis is proposed; the type strain is 8321T (= ATCC 700959T).