Revision of species delineation in the genus Ectothiorhodospira

When the type strains and other strains of the six currently defined specie s of the genus Ectothiorhodospira were examined by DNA-DNA reassociation an d RFLP of 16S/23S rDNA (ribotype). only four genospecies could be found, Th e possibility of defining taxonomically meaningful species corresponding to these four genospecies was investigated by combining DNA relatedness and r ibotype data with other genotypic and phenotypic characters already describ ed in the literature, an approach known as polyphasic taxonomy, Following t his comparison, the type strain and another strain of Ectothiorhodospira va cuolata were found to be very similar to the type strain of Ectothiorhodosp ira shaposhnikovii and have been transferred to this latter species, Also, the type strain of Ectothiorhodospira marismortui and another previously un identified strain were found to be very similar to the type strain of Ectot hiorhodospira mobilis and have been transferred to this latter species, Due to the limited degree of reciprocal DNA relatedness, strains belonging eit her to Ectothiorhodospira marina or to Ectothiorhodospira haloalkaliphila a re still considered as belonging to separate species, even though they show a remarkable phenotypic similarity, This revision has led to the delineati on of only four species in the genus Ectothiorhodospira, namely E. mobilis, E, shaposhnikovii. E, marina and E, haloaikaliphila, E, vacuolata is recog nized as a junior synonym of E, shaposhnikovii and E, marismortui as a juni or synonym of E, mobilis.