Abstract
Chloroform (CF) is an environmental contaminant that can be naturally formed in various environments ranging from forest soils to salt lakes. Here we investigated CF removal potential in sediments obtained from hypersaline lakes in Western Australia. Reductive dechlorination of CF to dichloromethane (DCM) was observed in enrichment cultures derived from sediments of Lake Strawbridge, which has been reported as a natural source of CF. No CF removal was observed in abiotic control cultures without artificial electron donors, indicating biotic CF dechlorination in the enrichment cultures. Increasing vitamin B12 concentration from 0.04 to 4 µM in enrichment cultures enhanced CF removal and reduced DCM formation. In cultures amended with 4 µM vitamin B12 and 13C labelled CF, formation of 13CO2 was detected. Known organohalide-respiring bacteria and reductive dehalogenase genes were neither detected using quantitative PCR nor metagenomic analysis of the enrichment cultures. Rather, members of the order Clostridiales, known to co-metabolically transform CF to DCM and CO2, were detected. Accordingly, metagenome-assembled genomes of Clostridiales encoded enzymatic repertoires for the Wood-Ljungdahl pathway and cobalamin biosynthesis, which are known to be involved in fortuitous and nonspecific CF transformation. This study indicates that hypersaline lake microbiomes may act as a filter to reduce CF emission to the atmosphere.
Highlights
Until the 1970s, halogenated organic compounds, organohalogens, were believed to originate exclusively from anthropogenic sources [1]
The top (0–12 cm) and bottom (>12 cm) layer sediments of Lake Strawbridge were slightly alkaline with a pH ranging from 8.2 to 8.5, whereas those of Lake Whurr were acidic with a pH of 4.6–5.4 (Table 1)
Water content, and total organic carbon (TOC) were higher in the top layer compared to the bottom layer of both lake sediments (Table 1)
Summary
Until the 1970s, halogenated organic compounds, organohalogens, were believed to originate exclusively from anthropogenic sources [1]. This long-held view was changed following the discovery of diverse organohalogens from natural environments. Over 5000 organohalogens with natural origins have been identified [2]. Overall anthropogenic sources were estimated to contribute to less than 10% of the global CF production of 700–820 Gg/y [5]. The formation of CF is mediated by biotic and abiotic processes, including burning of vegetation, chemical production by reactive iron species, and enzymatic halogenation [15]. Similar to other low molecular weight volatile organohalogens (VOX, e.g., chlorofluorocarbons), CF release into the atmosphere can cause ozone depletion and impact climate change [16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
