Isolation and characterization of a new dichloromethane degrading bacterium, Ralstonia metallidurans, PD11

The widely used organic solvent dichloromethane (DCM) has various toxic effects including carcinogenesis. We isolated a DCM-degrading bacterium Ralstonia metallidurans PD11 from drainage water which grew with DCM as a sole carbon source. PD11 was a methylotrophic bacterium with the ability to grow with C1 compounds such as methanol or methylamine. Although the existence of methylotrophic bacteria having DCM-degrading ability has been reported, there has been no report on Ralstonia sp. to date. The DCM-degrading activity of PD11 was increased by acclimatization, finally reaching a level to degrade 2,500 mg DCM/l within a week. The cell-free extract of PD11 showed DCM-degrading activity by liberating chloride which was stimulated by addition of glutathione, suggesting that the DCM dehalogenationg enzyme could be classified into the glutathione S-transferase super family.