PHENOTYPIC AND GENETIC DIVERSITY OF CHLORINE-RESISTANT METHYLOBACTERIUM STRAINS ISOLATED FROM VARIOUS ENVIRONMENTS

Strains of pink-pigmented facultative methylotrophs which were isolate d previously from various environments and assigned tentatively to the genus Methylobacterium were characterized in comparison with authenti c strains of previously known species of this genus. Most elf the isol ates derived from chlorinated water supplies exhibited resistance to c hlorine, whereas 29 to 40% of the isolates from air, natural aquatic e nvironments, and clinical materials were chlorine resistant. None of t he tested authentic strains of Methylobacterium species obtained from culture collections exhibited chlorine resistance. Numerical analysis of phenotypic profiles showed that the test organisms could be divided into 19 clusters at a similarity level of 80%, at which all establish ed Methylobacterium. species tested were separated from each other exc ept M. organophilum and M. rhodesianum. The chlorine-resistant isolate s were randomly distributed among all clusters. The 16S ribosomal DNA (rDNA) sequence-based phylogenetic analyses showed that representative s of the isolates together with known Methylobacterium species formed a line of descent distinct from that of members of related genera in t he alpha-2 subclass of the Proteobacteria and were divided into three subclusters within the Methylobacterium group. These results demonstra te that there is phenotypic and genetic diversity among chlorine-resis tant Methylobacterium strains within the genus.