Genus XIV Thiococcus Imhoff Sling and Petri 1998b 1139VP Johannes F Imhoff

Thi.o.coc'cus. Gr. n. thios sulfur; L. masc. n. coccus sphere; M.L. masc. n. Thiococcus sphere with sulfur.

Cells spherical, with diplococcus-shaped division stages, non-motile, multiply by binary fission. Gram negative, belong to the Gammaproteobacteria, and contain internal photosynthetic membranes consisting of bundles of ribbon-like branched tubes continuous with the cytoplasmic membrane. Individual cells colorless, color of cell suspensions is yellowish to orange-brown. Pho-tosynthetic pigments are bacteriochlorophyll b and carotenoids.

Obligately phototrophic and strictly anaerobic. Photolithoau-totrophic growth under anoxic conditions in the light with sulfide and S0 as electron donors. During oxidation of sulfide, S0 transiently stored inside the cells in the form of highly refractile globules. Final oxidation product is sulfate. In the presence of sulfide and bicarbonate, simple organic substrates photoassimi-lated.

Mesophilic bacteria with optimum growth at 20-35°C and neutral pH (pH range 6.5-7.5). May require salt for optimum growth.

Type species : Thiococcus pfennigii (Eimhjellen 1970) Imhoff, Suling and Petri 1998b, 1139 (Thiocapsa pfennigii Eimhjellen 1970, 193.)

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