Acetylene-Fueled Trichloroethene Reductive Dechlorination in a Groundwater Enrichment Culture

Groundwater contamination by chlorinated solvents like trichloroethene (TCE) and perchloroethene (PCE) is a widespread environmental issue. These compounds can undergo abiotic degradation in the presence of certain minerals, producing acetylene (C2H2) as a byproduct. While acetylene is known to inhibit microbial processes such as TCE dechlorination, it can also serve as a carbon and energy source for acetylenotrophic bacteria. Prior research has demonstrated that acetylene can support TCE reductive dechlorination in laboratory cocultures containing specific microbial strains. However, the extent to which this coupling occurs in natural microbial communities remains unclear. This gap in knowledge motivated the investigation of acetylene-fueled dechlorination in a groundwater-derived enrichment culture, aiming to better understand the role of acetylene in bioremediation processes.

This study aimed to investigate whether acetylene can support reductive dechlorination of TCE and PCE in a microbial community derived from contaminated groundwater. The researchers sought to enrich a microbial community using acetylene as the sole electron donor and organic carbon source. The primary objective was to determine if acetylene-fueled dechlorination is possible in a natural microbial community, rather than only in synthetic laboratory cocultures. Additionally, the study aimed to identify the microbial taxa involved in this process and assess the functional potential of the enriched community through metagenomic analysis. By doing so, the researchers hoped to expand the understanding of how acetylene influences microbial metabolism in contaminated aquifers and whether this interaction is relevant in natural settings.

The study utilized a groundwater enrichment culture that was amended with acetylene as the sole electron donor and organic carbon source. The researchers monitored the dechlorination of TCE and PCE under anaerobic conditions to assess microbial activity. Metagenomic sequencing was performed on the enriched microbial community to identify potential functional genes and taxonomic composition. The metagenome was analyzed to determine the metabolic capabilities of the community and to detect the presence of acetylenotrophic bacteria. The researchers also assessed the stability of the enrichment culture over time and confirmed that dechlorination occurred in the presence of acetylene. No prior synthetic coculture experiments were used in this study, which focused on a natural microbial community. The study combined experimental and computational approaches to characterize the microbial interactions and metabolic functions involved in acetylene-fueled dechlorination.

The microbial community enriched with acetylene successfully dechlorinated TCE and PCE under anaerobic conditions, demonstrating that acetylene can serve as a carbon and energy source for dechlorinating bacteria. Metagenomic analysis revealed the presence of a novel acetylenotrophic bacterium in the phylum Actinobacteria, which had not been previously reported. The enriched community exhibited stable dechlorination activity over time, indicating that the process is reproducible and not transient. The results suggest that acetylene-fueled dechlorination can occur in natural microbial communities, not just in synthetic cocultures. The metagenome provided insights into the functional potential of the community, including genes associated with acetylene metabolism and reductive dechlorination. No other electron donors were required for the observed dechlorination, confirming that acetylene alone was sufficient to support the process. These findings indicate that acetylene can play a dual role as both an inhibitor and a fuel source in microbial dechlorination. The study provides the first evidence of an anaerobic acetylenotroph in Actinobacteria, expanding the known diversity of this metabolism.

The study demonstrates that acetylene can support reductive dechlorination of TCE and PCE in a natural microbial community derived from contaminated groundwater. The presence of a novel acetylenotrophic bacterium in the phylum Actinobacteria suggests that this metabolism may be more widespread in the environment than previously assumed. The results support the hypothesis that acetylene can serve as both an electron donor and a carbon source for dechlorinating bacteria, even in the absence of other organic substrates. The metagenomic analysis provides evidence that the enriched community contains the genetic potential for acetylene metabolism and dechlorination. The study confirms that acetylene-fueled dechlorination is possible in natural microbial communities, not just in synthetic cocultures. These findings contribute to the understanding of biotransformation processes in contaminated aquifers and suggest that acetylene may play a more significant role in microbial metabolism than previously recognized. The identification of a new acetylenotroph in Actinobacteria highlights the potential for undiscovered microbial diversity in contaminated environments.