Metabolic methanisation of chloroform by a three component microbial community.
Chloroform is a highly toxic organochlorine found in subsurface environments due to its poor handling and disposal techniques by industry. Bioremediation of organochlorine polluted environments is a well established technique that utilises dehalogenating bacteria to reductively dechlorinate organochlorines to their hydrocarbon counterpart. One drawback of bioremediation is that chloroform is inhibitory to this microbial process. A key to the advancement of the bioremediation industry is the discovery of dahalogenating bacteria capable of complete chloroform metabolism.
Here we report for the first time a microbial population capable of rapid metabolic transformation of chloroform at high concentrations (~50 ppm) to methane. Cultures were established with sediment sampled 4.5 m below ground surface from an aquifer polluted for over 40 years with a mixture of organochlorine compounds. A combination of functional data, pyrosequencing, quantitative PCR and the application of labelled substrates were used to elucidate the participating microbial community members. Members of the Dehalobacter genus were found to first dehalo-respire chloroform to dichloromethane which was then fermented to formate and acetate. A hydrogenotrophic syntroph (i.e. a methanogen) was then required to drive this process forward to methane.