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National Institute of Environmental Health Sciences (NIEHS) Superfund Research Program (SRP), 2 pp, 2020

According to a new NIEHS SRP study, TCE bioremediation using D. mccartyi strain 195 (Dhc195) may stall when arsenic is present. Adding As(III) led to a 50% decrease in Dhc195 cell growth and significant decrease in TCE degradation. When As(V) was added, Dhc195 converted As(V) to As(III) over time. While As(V) exposure did not initially impact TCE degradation, inhibition of TCE degradation was observed after exposure for >12 days, corresponding to the conversion of As(V) to As(III) and its subsequent accumulation. Significant genetic changes in the Dhc195 bacterial community were observed in response to As(III) and As(V). In As(III)-amended cultures, 52 protein-coding genes, or transcripts, were downregulated and 278 transcripts were upregulated. In cultures amended with As(V), 33 transcripts were downregulated and 332 transcripts were upregulated. Some of the gene regulation changes were shared between As(III) and As(V), but others were specific to the different types of arsenic. With exposure to both types of arsenic, genes involved in DNA repair, replication, and translation were found at higher levels, which is consistent with promoting DNA mutations in bacteria. The researchers also observed significant changes in metabolite abundances within the Dhc195 community in response to both types of arsenic. Based on these results, engineered bioremediation strategies, such as developing ways to inhibit conversion of As(V) to As(III) or providing the TCE-dechlorinating bacterial community with additional nutrients, could promote TCE degradation at arsenic-contaminated sites. See YouTube for video summary:

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