Taxonomic Comments

The genus Thiodictyon presently comprises two species: T. elegans, the type species of the genus, and T. bacillosum. The latter species was originally described by Winogradsky (1888) as Amoebobacter bacillosus. Pfennig and Tr√Ęper (1971b) transferred Amoebobacter bacillosus to the genus Thiodictyon, because the rod-shaped cells are very similar to those of Thiodictyon elegans. In addition, according to the original description of the type species of the genus Amoebobacter (Amoebobacter roseus Winogradsky 1888), this genus should comprise only spherical, nonmotile species with gas vesicles. According to 16S rRNA oligonucleotide pattern analysis, Thiodictyon elegans is related to Thiocapsa species, including Thiocapsapendens and Thiocapsa rosea (Fowler et al., 1984). Studies on 16S rDNA sequence similarities of Thiodictyon species are expected to confirm this relationship. Because of the lack of genetic sequence information, Thiodictyon species have not been included in a recent reclassification of Chromatiaceae species (Gu-yoneaud et al., 1998b; Imhoff et al., 1998b).

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