Genus XX Thiopedia Winogradsky 1888 85AL Johannes F Imhoff'di.a. G. n. thios sulfur; Gr. n. pedium a plain, a flat area; M.L. fem. n. Thiopedia sulfur plain.

Cells spherical to ovoid, nonmotile, and multiply by binary fission. Rectangular platelets formed with 4, 8, 16, 32, or more regularly arranged cells (up to 128 or 256 cells may stick together). Gram negative, contain irregularly shaped gas vesicles in the central part of the cell and internal photosynthetic membranes of vesicular type with bacteriochlorophyll a and carote-noids as photosynthetic pigments.

Photolithoautotrophic growth under anoxic conditions in the light with sulfide and S0 as electron donors. During oxidation of sulfide, S0 transiently stored in the peripheral part of the cell in the form of highly refractile globules. Final oxidation product is sulfate. In the presence of sulfide and bicarbonate, simple organic substrates are photoassimilated. Reduced sulfur compounds required as sulfur source.

Habitat: mud and stagnant water of ponds and lakes containing hydrogen sulfide, common planktonic bacterium in the sul-fide-containing hypolimnion of freshwater lakes.

Type species: Thiopedia rosea Winogradsky 1888, 85.

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