Genus IV Isochromatium Imhoff Sling and Petri 1998b 1141VP Johannes F Imhoff

I'' Gr. adj. isos equal, similar; Chromatium a genus name; M.L. neut. n. Isochromatium the similar Chromatium, the bacterium similar to Chromatium.

Cells straight to slightly curved rods, multiply by binary fission, motile by a polar tuft of flagella. Gram negative, belong to the Gammaproteobacteria, and contain internal photosynthetic membranes of vesicular type with bacteriochlorophyll a and carote-noids as photosynthetic pigments.

Obligately phototrophic and strictly anaerobic. Photolithoau-totrophic growth under anoxic conditions in the lightwith sulfide and S0 as electron donors. During oxidation of sulfide, S0 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 are photoassimilated.

Mesophilic bacteria with optimum growth at 25-35°C and a pH range from 6.5 to 7.6. Salt is required for growth at concentrations typical for marine bacteria.

Habitat: estuarine salt flats and salt marshes. The mol% G + C of the DNA ts: 62.2-62.8. Type species: Isochromatium buderi (TrUper and Jannasch 1968) Imhoff, SUling and Petri 1998b, 1141 (Chromatium buderi TrUper and Jannasch 1968, 364.)

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