Taxonomic Comments

In the past, all rod-shaped, motile, purple sulfur bacteria without gas vesicles that store S0 inside their cells were classified as Chro-matium species (Pfennig and Traper, 1989). These species were not only phenotypically quite diverse, but also distantly related on a genetic basis, as indicated by the large variation in DNA base ratio within these bacteria (48.0-70.4 mol% G + C). 16S rDNA sequence analysis of recognized species of the family Chro-matiaceae gave support for a new classification, in which the type species of the genus, Chromatium okenii, appeared distant and separate from most of the other species previously assigned to this genus. The only other species showing sufficient phenotypic similarity to C. okenii to allow assignment to this genus is C. weissei (Imhoff et al., 1998b), although 16S rDNA sequence data for this species are currently not available.

Further Reading

Fowler, V.J., Pfennig, N., Schubert, W. and Stackbrandt, E. 1984. Towards a phylogeny of phototrophic purple sulfur bacteria - 16S rRNA oli-gonucleotide cataloguing of 11 species of Chromatiaceae. Arch. Micro-biol. 139: 382-387. Imhoff, J.F. 1992. Taxonomy, phylogeny and general ecology of anoxy-genic phototrophic bacteria. In Carr, and Mann (Editors), Biotechnology Handbook for Photosynthetic Prokaryotes, Plenum Press, London, New York. p. 83-92. Imhoff, J.F., Suling, J. and Petri, R. 1998. Phylogenetic relationships among the Chromatiaceae, their taxonomic reclassification and description of the new genera Allochromatium, Halochromatium, Isochro-matium, Marichromatium, Thiococcus, Thiohalocapsa, and Thermochro-matium. Int. J. Syst. Bacteriol. 48: 1129-1143. Imhoff, J.F. 2001a. True marine and halophilic anoxygenic phototrophic bacteria. Arch. Microbiol. 176: 243-254.

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