Among the chlorinated compounds, dioxins are at the top of the list in terms of toxicity and persistence in the environment. The Passaic River in New Jersey is highly contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin, the most toxic of the dioxin congeners. Despite fishing advisories, members of communities along the Passaic River continue to utilize it for sustenance fishing. We aimed to determine if dioxins are dechlorinated by bacteria native to the river sediments. We established anaerobic enrichment cultures inoculated with material from 1) original river sediment, 2) river sediment cultures previously enriched on trichloroethene, and 3) river sediment cultures previously enriched on dichlorobenzene. Microcosms were amended with three dioxin congeners: 2,7-dichlorodibenzo-p-dioxin (2,7-DiCDD); 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeTCDD); and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD). Select sets were also amended with trichloroethene or dichlorobenzene to test the additional effect of co-substrate during dioxin dechlorination. 16S rRNA gene amplicon sequencing was performed to assess differences in the community between active treatments. Whole-genome shotgun sequencing was also performed to learn about the breadth of functional genes in the entire microbial community of the 2,3,7,8-TeCDD- dechlorinating culture. After 1.5 years, dechlorination was observed in at least one treatment of all tested dioxin congeners. Preliminary 16S rRNA gene sequencing indicates dominance of a Dehalococcoidia phylotype in the 2,3,7,8-TeCDD dechlorinating enrichment. By the time of presentation, we expect to have identified potential reductive dehalogenases in the 2,3,7,8-TeCDD-dechlorinating culture from the sequenced metagenome. Further characterization of the bacteria involved in these processes can provide methods for monitoring dechlorination in contaminated sites and potentially lead to new in situ treatment technologies.

Anaerobic dechlorination of chlorinated dibenzo-p-dioxins in sediment cultures and clues from genetic sequencing

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.