Dehalobium species implicated in 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin dechlorination in the contaminated sediments of Sydney Harbour Estuary. (June 2022)

• Record Type: Journal Article
• Authors: Lee, Matthew; Liang, Gan; Holland, Sophie I.; O'Farrell, Casey; Osborne, Keith; Manefield, Michael J.
• Is Part Of: Marine pollution bulletin. Volume 179(2022)
• Publication Date: 2022-06
• Subjects: Polychlorinated dibenzo-p-dioxins -- Polychlorinated dibenzo-p-furans -- Microbial ecology -- Reductive dehalogenation -- Dehalococcoidia -- Dehalobium; Marine pollution -- Periodicals; Marine Biology -- Periodicals; Water Pollution -- Periodicals; Mer -- Pollution -- Périodiques; Publications périodiques; Pollution des mers; Lutte antipollution; Electronic journals; 363.7394
• DOI: 10.1016/j.marpolbul.2022.113690
• Languages: English
• ISSNs: 0025-326X

Abstract

Abstract: Polychlorinated dibenzo- p -dioxins and furans (PCDD/F) are some of the most environmentally recalcitrant and toxic compounds. They occur naturally and as by-products of anthropogenic activity. Sydney Harbour Estuary (Sydney, Australia), is heavily contaminated with PCDD/F. Analysis of sediment cores revealed that the contamination source area in Homebush Bay continues to have one of the highest levels of PCDD/F contamination in the world (5207 pg WHO-TEQ g −1 ) with >50% of the toxicity attributed to 2, 3, 7, 8-tetrachlorodibenzo- p -dioxin (2, 3, 7, 8-TCDD), the most toxic PCDD/F congener. Comparison of congener profiles at the contamination source area with surrounding bays and historical data provided evidence for the attenuation of 2, 3, 7, 8-TCDD and other congeners at the source area. This finding was supported by the detection of di-, mono- and unchlorinated dibenzo- p -dioxin. Microbial community analysis of sediments by 16S rRNA amplicon sequencing revealed an abundance of lineages from the class Dehalococcoidia (up to 15% of the community), including the genus Dehalobium (up to 0.5%). Anaerobic seawater enrichment cultures using perchloroethene as more biologically available growth substrate enriched the Dehalobium population by more than six-fold. The enrichment culture then proved capable of reductively dechlorinating 2, 3, 7, 8-TCDD to 2, 3, 7-TriCDD and octachlorodibenzo- p -dibenzodioxin (OCDD) to hepta and hexa congeners. This work is the first to show microbial reductive dehalogenation of 2, 3, 7, 8-TCDD with a bacterium from outside the Dehalococcoides genus, and one of only a few that demonstrates PCDD/F dechlorination in a marine environment. Highlights: PCDD/F congener analysis was carried out on sediments from nine locations in Sydney Harbour. PCDD/F concentrations at the source area in Homebush Bay remain among the highest in the world. Comparison on congener profiles between locations and with historical data provided evidence of their natural attenuation. Microbial community analysis of the sediments revealed an abundance of organohalide respiring bacteria. Anaerobic enrichment cultures showed that Dehalobium spp. are likely to be involved 2, 3, 7, 8-TCDD degradation.