Metagenomic survey of chloroform fate in hypersaline lake Strawbridge in western Australia

Chloroform (CF) is an environmental contaminant that can be naturally formed in hypersaline lake Strawbridge in western Australia. Anaerobic enrichment cultures using sediments from this lake showed CF degradation to dichloromethane (DCM) and CO2. The potential microbes and genes involved in CF degradation were investigated using metagenome sequencing. Known organohalide-respiring bacteria and their reductive dehalogenase genes were not detected. Rather, acetogens like Clostridium and methanogens like Methanosarcina that are capable for co-metabolically degrading CF to DCM and CO2 were detected in the sediment microcosms and enrichment cultures. Additionally, haloalkane dehalogenase and oxygenase that are possibly involved in further aerobic degradation of DCM were also detected in the sediment microcosms and enrichment cultures. These findings show that microbiota may act as a filter for CF emission from hypersaline lakes to the atmosphere.