Mineralization versus fermentation: evidence for two distinct anaerobic bacterial degradation pathways for dichloromethane
- Univ. of Tennessee, Knoxville, TN (United States). Center for Environmental Biotechnology and Dept. of Civil and Environmental Engineering
- Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry
- Corteva Agriscience, Wilmington, DE (United States)
- The Chemours Company, Wilmington, DE (United States). Chemours Corporate Remediation Group
- Univ. of Tennessee, Knoxville, TN (United States). Center for Environmental Biotechnology, Dept. of Civil and Environmental Engineering, Dept. of Chemistry, Dept. of Microbiology, and Dept. of Biosystems; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Joint Institute for Computational Sciences (JIBS)
Dichloromethane (DCM) is an anthropogenic pollutant with ozone destruction potential that is also formed naturally. Under anoxic conditions, fermentation of DCM to acetate and formate has been reported in axenic culture Dehalobacterium formicoaceticum, and to acetate, H2 and CO2 in mixed culture RM, which harbors the DCM degrader ‘Candidatus Dichloromethanomonas elyunquensis’. RM cultures produced 28.1 ± 2.3 μmol of acetate from 155.6 ± 9.3 μmol DCM, far less than the one third (i.e., about 51.9 µmol) predicted based on the assumed fermentation model, and observed in cultures of Dehalobacterium formicoaceticum. Temporal metabolite analyses using gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy revealed that no 13C-labeled acetate was formed in 13C-DCM-grown RM cultures, indicating acetate was not a direct product of DCM metabolism. The data were reconciled with DCM mineralization and H2 consumption via CO2 reduction to acetate and methane by homoacetogenic and methanogenic partner populations, respectively. In contrast, Dehalobacterium formicoaceticum produced 13C-labeled acetate and formate from 13C-DCM, consistent with a fermentation pathway. Free energy change calculations predicted that organisms with the mineralization pathway are the dominant DCM consumers in environments with H2 <100 ppmv. These findings have implications for carbon and electron flow in environments where DCM is introduced through natural production processes or anthropogenic activities.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1606041
- Journal Information:
- The ISME Journal, Journal Name: The ISME Journal Journal Issue: 4 Vol. 14; ISSN 1751-7362
- Publisher:
- Nature Publishing GroupCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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