THE PHYLOGENETIC RELATIONSHIP AMONG ECTOTHIORHODOSPIRACEAE - A REEVALUATION OF THEIR TAXONOMY ON THE BASIS OF 16S RDNA ANALYSES

Sequences of the 16S rRNA gene were determined from all type strains o f the recognized Ectothiorhodospira species and from a number of addit ional strains. For the first time, these data resolve the phylogenetic relationships of the Ectothiorhodospiraceae in detail, confirm the es tablished species, and improve the classification of strains of uncert ain affiliation. Two major groups that are recognized as separate gene ra were clearly established. The extremely halophilic species were rem oved from the genus Ectothiorhodospira and reassigned to the new genus Halorhodospira gen. nov., to recognize that the most halophilic eubac teria are species of this genus. These species are Halorhodospira halo phila comb. nov., Halorhodospira halochloris comb. nov., and Halorhodo spira abdelmakekii comb. nov. Among the slightly halophilic Ectothiorh odospira species, the classification of strains belonging to Ectothior hodospira mobilis and Ectothiorhodospira shaposhnikovii was improved. Several strains that were tentatively identified as Ectothiorhodospira mobilis form a separate cluster on the basis of their 16S rDNA sequen ces and are recognized as two new species: Ectothiorhodospira haloalka liphila sp. nov., which includes the most alkaliphilic strains origina ting from strongly alkaline soda lakes, and Ectothiorhodospira marina, describing isolates from the marine environment.