TAXONOMIC ANALYSIS OF A GROUP OF STRAINS OF BACTERIOCHLOROPHYLL B-CONTAINING PURPLE BACTERIA OF THE GENUS BLASTOCHLORIS

The phylogenetic and phenotypic structure of a group of bacteriochloro phyll b-containing purple bacteria of the genus Blastochloris was stud ied to determine the taxonomic status of these bacteria. The group inc luded the type strains of B. viridis and B. sulfoviridis and eight Bla stochloris strains isolated from different water bodies. By DNA-DNA hy bridization carried out by the optical method, three phylogenetic clus ters were identified within the group studied that corresponded to thr ee genospecies related, at a DNA homology level of 30-50%. Two of thes e genospecies were represented by the type strains of B. viridis and B . sulfoviridis and by three new isolates each; the third genospecies i ncluded two new isolates, KR-70sv and KR-101sv. Comparative analysis o f the fatty acid composition of four strains gave the same clusters as those yielded by DNA hybridization. Morphological and physiological i nvestigation confirmed that strains phylogenetically close to B. virid is and B. sulfoviridis indeed belonged to these species. However, stra ins KR-70sv and KR-101sv, constituting a separate genospecies, showed no significant phenotypic distinctions from B. sulfoviridis and were a ssigned to this species. Thus, out of eight new isolates, three were r eferred to B. viridis and five to B. sulfoviridis. The latter strains are phenotypically similar but phylogenetically divergent.