Differentiation of the genus Thiorhodococcus from other genera

The genus Thiorhodococcus is distinguished from other members of the family Chromatiaceae by phenotypic and genetic traits. The spherical, motile, purple sulfur bacteria of the genus Thiorhodo-

coccus are morphologically similar to Thiocystis species, but differ from them by their salt requirement and 16S rDNA sequence composition. Thiorhodococcus minor forms a separate lineage not specifically affiliated with other Chromatiaceae species (Imhoff et al., 1998b; see Fig. BXII.y.3 of the chapter describing the family Chromatiaceae). Characteristics useful for the differentiation of the genus Thiorhodococcus from other members of the family Chromatiaceae are shown in Table BXII.y.5 of the chapter describing the family Chromatiaceae.

Further Reading

Guyoneaud, R., Matheron, R., Liesack, W., Imhoff, J.F. and Caumette, P. 1997. Thiorhodococcus minus, gen. nov., sp. nov., a new purple sulfur bacterium isolated from coastal lagoon sediments. Arch. Microbiol. 168: 16-23.

Guyoneaud, R., Matheron, R., Baulaigue, R., Podeur, K., Hirschler, A. and Caumette, P. 1996. Anoxygenic phototrophic bacteria in eu-trophic coastal lagoons of the French Mediterranean and Atlantic Coast (Prevost Lagoon, Arcachon Bay, Certes Fishponds). Hydro-biologia 329: 33-43.

List of species of the

1. Thiorhodococcus minor Guyoneaud, Matheron, Liesack, Imhoff and Caumette 1998a, 328VP (Effective publication: Guyoneaud, Matheron, Liesack, Imhoff and Caumette 1997, 22.)

Cells spherical to slightly ovoid, 1.0-2.0 |im in diameter, highly motile by flagella, divide by binary fission, and form diplococcus-shaped division stages (Fig. BXII.y.17). Color of individual cells grayish, color of cell suspensions brown-orange. Photosynthetic pigments are bacteriochlorophyll a and carotenoids of the normal spirilloxanthin group, with rhodopin as major pigment.

Photolithoautotrophic growth under anoxic conditions in the light with hydrogen, sulfide, thiosulfate, and S0 as electron donors. In the presence of sulfide and hydrogen carbonate, acetate, propionate, lactate, glycolate, pyruvate, malate, fumarate, succinate, fructose, sucrose, ethanol, and propanol are photoassimilated. Chemolithotrophic growth with sulfide and thiosulfate, and chemoorganotrophic growth with acetate and fructose are possible under mi-crooxic conditions in the dark. Some strains (but not the type strain) assimilate sulfate. Nitrogen sources: ammonium salts and N2.

Mesophilic marine bacterium requiring NaCl for growth. Optimal growth at 2% NaCl (salinity range 0.5-9% NaCl), pH 7.0-7.2 (pH range 6.0-8.0), and 30-35°C.

Habitat: anoxic sediments from coastal lagoons and marine environments rich in sulfide.


The mol% G + C of the DNA is: 66.9 (HPLC). Type strain: CE2203, ATCC 700259, DSM 11518. GenBank accession number (16S rRNA): Y11316.

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