Phylogenetic analysis of dichloromethane-utilizing aerobic methylotrophic bacteria

The phylogenetic relationships of 12 aerobic dichloromethane-degrading bact eria that implement different C-1-assimilation pathways was determined base d on 16S ribosomal RNA sequences and DNA-DNA hybridization data. The restri cted facultative methylotroph "Methylophilus leisingerii" DM I with the rib ulose monophosphate pathway was found to belong to the genus Methylophilus cluster of the beta subclass of Proteobacteria. The facultative methylotrop h Methylorhabdus multivorans DM13 was assigned to a separate branch of the alpha-2 group of Proteobacteria. Paracoccus methylutens DM12, which utilize s C-1-compounds via the Calvin cycle, was found to belong to the alpha-3 gr oup of Proteobacteria (more precisely, to the genus Paracoccus cluster). Th us, phylogenetic analysis confirmed the taxonomic status of these recently characterized bacteria. According to the degree of DNA homology, several no vel strains of methylotrophic bacteria were divided into three genotypic gr oups within the alpha-2 group of the Proteobacteria. Genotypic group 1, com prising strains DM1, DM3, and DM5 through DM9, and genotypic group 3, compr ising strain DM10, were phylogenetically close to the methylotrophic bacter ia of the genus Methylopila, whereas genotypic group 2 (strain DM4) was clo se to bacteria of the genus Methylobacterium. The genotypic groups obviousl y represent distinct taxa of methylotrophic bacteria, whose status should b e confirmed by phenotypic analysis.