Genus II Allochromatium Imhoff Suling and Petri 1998b 1140VP Johannes F Imhoff

Al'' Gr. adj. alios the other; Chromatium a genus name; M.L. neut. n. Allochromatium the other Chromatium.

Cells straight to slightly curved rods, single or in pairs, multiply by binary fission, motile 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.

Photolithoautotrophic growth occurs 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. Molecular hydrogen and thiosulfate may be used as electron donors. In the presence of sulfide and bicarbonate, organic substrates can be photoassimilated, potentially mixo-trophic. Some species may grow chemoautotrophically or che-moorganotrophically under microoxic to oxic conditions in the dark. Storage materials: polysaccharides, poly-b-hydroxybutyrate, S0, and polyphosphates. Vitamin B12 is required.

Mesophilic bacteria with growth at 25-35°C and pH 6.5-7.6. No distinct requirement for salt, except for strains that originate from the marine and brackish water environment and may tolerate or require low concentrations of salt.

Habitat: ditches, ponds, and lakes with stagnant freshwater containing hydrogen sulfide and exposed to the light; also sewage lagoons, estuaries, and salt marshes.

Type species: Allochromatium vinosum (Ehrenberg 1838) Im-hoff, Silling and Petri 1998b, 1141 ( Chromatium vinosum (Ehrenberg 1838) Winogradsky 1888, 99; Monas vinosa Ehrenberg 1838, 11.)

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