Genus XI Thermochromatium Imhoff Suling and Petri 1998b 1140VP

Johannes F. Imhoff and Michael T. Madigan' Gr. adj. thermos hot; Chromatium a genus name; M.L. neut. n. Thermochromatium the hot Chromatium.

Cells straight to slightly curved rods, multiply by binary fission, motile, most likely by polar flagella. Gram negative, belong to the Gammaproteobacteria, and contain internal photosynthetic membranes of vesicular type in which the photosynthetic pigments bacteriochlorophyll a and carotenoids are located.

Strictly anaerobic, obligately phototrophic, and require sul-fide-reduced media. Photolithoautotrophic growth under anoxic conditions in the light with sulfide and S0 as electron donors. 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, organic substrates can be photoassimilated.

Thermophilic freshwater bacteria with optimum growth at temperatures higher than 40°C, at neutral pH 7.0, and without a requirement for salt.

Habitat: sulfide-containing hot springs of neutral to alkaline pH having temperatures between 35 and 60°C. The mol% G + C of the DNA is: 60-63.

Type species : Thermochromatium tepidum (Madigan 1986) Imhoff, Suling and Petri 1998b, 1140 ( Chromatium tepidum Madigan 1986, 226.)

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