Taxonomic Comments

Previously, nonmotile, spherical, purple sulfur bacteria without gas vesicles have been united within the genus Thiocapsa. However, the results of genetic analyses indicate that two of the three species placed in this genus (the former Thiocapsa halophila and Thiocapsa pfennigii) were phylogenetically quite distant from the type species, Thiocapsa roseopersicina. Both species belong to the cluster containing truly marine Chromatiaceae species Figs. BXII.y.3 and BXII.y.4 of the chapter describing the family Chromatiaceae). Consequently, they were removed from the genus Thi-ocapsa and transferred to Thiococcus and Thiohalocapsa as Thio-coccus pfennigii and Thiohalocapsa halophila, respectively (Imhoff et al., 1998b).

Furthermore, Thiocapsa rosea and Thiocapsa pendens, previously known as Amoebobacter roseus and Amoebobacter pendens (Pfennig and Trtiper, 1971b; Pfennig, 1989a), are closely related genetically to Thiocapsa roseopersicina and were included in the genus Thiocapsa (Guyoneaud et al., 1998b).

The type species of the genera Amoebobacter and Thiocapsa were united and therefore a decision concerning the genus name had to be made. Because both genera and their type strains were included in the Approved List and had been legitimately published at the same date (Winogradsky, 1888), none of the genera and species had priority according to the rules of Nomenclature

(rules 23a and 24b). Thiocapsa is the better-known genus and the more appropriate name, and Thiocapsa roseopersicina one of the best-studied species of purple sulfur bacteria. Therefore, according to rule 42 and recommendation 42 of the International Code of Nomenclature of Bacteria (Lapage et al., 1992), the two bacteria were united within the genus Thiocapsa, and Thiocapsa ro-seopersicina retained as the type species (Guyoneaudetal., 1998b). Because the nomenclatural type had been removed from the genus Amoebobacter, the names of other Amoebobacter species were changed, according to rule 37a (see also genera Thiolamprovum and Lamprocystis).

Further Reading

Guyoneaud, R, Süling, J., Petri, R., Matheron, R., Caumette, P., Pfennig, N. and Imhoff, J.F. 1998. Taxonomic rearrangements of the genera Thiocapsa and Amoebobacter on the basis of 16S rDNA sequence analyses and description of Thiolamprovum gen. nov. Int. J. Syst. Bacteriol. 48: 957-964.

Pfennig, N. and Trüper, H.G. 1971. New nomenclatural combinations in the phototrophic sulfur bacteria. Int. J. Syst. Bacteriol. 21: 11-14.

Takacs, B.J. and Holt, S.C. 1971. Thiocapsa floridana; a cytological physiological and chemical characterization. I. Cytology of whole cells and isolated chromatophore membranes. Biochim. Biophys. Acta 233: 258-277.

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