Thiocapsa Gr n thios sulfur L n capsa box ML fem n Thiocapsa sulfur box

Cells spherical, 1.0-3.0 |im in diameter, diplococci before multiplication by binary fission, nonmotile. Tetrads may be formed after consecutive division in two perpendicular planes. Individual cells surrounded by a strong slime capsule and may contain gas vesicles. Gram negative, belong to the Gammaproteobacteria, and have internal photosynthetic membranes of vesicular type containing the photosynthetic pigments bacteriochlorophyll a and carotenoids.

Photolithotrophic growth under anoxic conditions in the light possible with sulfide, thiosulfate, and sulfur as electron donors. Hydrogen may also be used. During oxidation of sulfide, S0 is transiently stored inside the cells in the form of highly refractile globules. Sulfate is the final oxidation product. In the presence of sulfide and bicarbonate, simple organic substrates can be pho-toassimilated. Some species may grow chemoautotrophically or chemoheterotrophically under microoxic to oxic conditions in the dark. Storage materials: polysaccharides, poly-b-hydroxybu-tyrate, S0, polyphosphates. Vitamin B12 may be required.

Type species: Thiocapsa roseopersicina Winogradsky 1888, 84.

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