Analysis of the key functional genes in new aerobic degraders of dichloromethane

The genes of dichloromethane (CH₂C1₂, DCM) degradation have been characterized in the aerobic degraders “Gottschalkia methylica” DM15, “Ancylobacter dichloromethanicus” DM16, and Methylobac- terium extorquens DM17, isolated from different regions of Russia. The sequencing of the structural gene dcmA of DCM dehalogenase, followed by phylogenetic analysis, showed that the new degraders possess A-type dehalogenases. The DcmAs of the strains DM15 and DM17 were identical to the known orthologous proteins of Methylorhabdus multivorans DM 13 and Methylobacterium dichloromethanicum DM4, respectively. DcmA of the degrader DM16 differed by three amino acid substitutions from DcmA of strain DM4. In agreement with the organization of the cluster of DCM degradation genes in M. dichloromethanicum DM4, the regulatory gene dcmR and the open reading frame orf353, flanking dcmA, were identified in the new degraders. The similarity of DCM degradation genes in aerobic degraders of different taxonomic position and geographical origin suggests their distribution among methylotrophic bacteria by means of horizontal transfer.