Microbial Debromination of Polybrominated Diphenyl Ethers by Dehalococcoides-Containing Enrichment Culture

Abstract

Polybrominated diphenyl ethers (PBDEs), commonly used as flame retardants in a wide variety of consumer products, are emerging persistent pollutants and ubiquitously distributed in the environment. The lack of proper bacterial populations to detoxify these recalcitrant pollutants, in particular of higher brominated congeners, has confounded the attempts to bioremediate PBDE-contaminated sites. In this study, we report a Dehalococcoides-containing enrichment culture, PB, which completely debrominates 0.44 μM tetra-brominated diphenyl ether (BDE) 47 to diphenyl ether within 25 days (0.07 μM Br–/day) and extensively debrominates 62.4 ± 4.5% of 0.34 μM hepta-BDE 183 (0.006 μM Br–/day) with a predominant generation of penta- through tri-BDEs as well as small amounts of diphenyl ether within 120 days. Later, a marked acceleration rate (0.021 μM Br–/day) and more extensive debromination (87.7 ± 2.1%) of 0.38 μM hepta-BDE 183 was observed in the presence of 0.44 μM tetra-BDE 47, which is achieved via the faster growth rate of responsible bacterial populations on lower BDE-47 and debromination by expressed BDE-47 reductive dehalogenases. Therefore, the PB enrichment culture can serve as a potential candidate for in situ PBDE bioremediation since both BDE-47 and BDE-183 are dominant and representative BDE congeners and often coexist in contaminated sites.

Interactions of Brominated Flame Retardants with Membrane Models of Dehalogenating Bacteria: Langmuir Monolayer and Grazing Incidence X-ray Diffraction Studies

“…Among them, Dehalococcoides is the most widespread and the best-researched genus. , These small Gram-positive bacteria are widespread in soils, sediments, and porous aquifer rocks. They can subsequently dehalogenate even perhalogenated aromatic organics, such as hexachlorobenzene, and different highly brominated diphenyl ethers. , To perform dehalorespiration, Dehalococcoides need gaseous hydrogen, which they cannot produce themselves, thus cooperation in consortium with other bacteria is crucial for their effectiveness. − Rhodopseudomonas palustris is a Gram-negative versatile photosynthetic bacterium that can also degrade BFRs, but what is more, emits hydrogen. , Dehalococcoides and Rhodopseudomonas palustris are frequently applied in bioremediation processes, both in the ex situ and also in situ techniques. − They could also be effectively used to remediate BFR-contaminated soils. − However, BFRs, and their metabolites, are often toxic to different members of soil microbial consortia. , BFRs are hydrophobic and when absorbed from the soils they may damage the plasma membranes of the bacterial cells. − To be effectively metabolized, BFRs must be incorporated into the membrane, as multiple enzymes, including dehalogenases, are membrane-related. , Accumulated in the membrane, BFRs should not disturb its structure and impair functions.…”

“…They can subsequently dehalogenate even perhalogenated aromatic organics, such as hexachlorobenzene, 27 and different highly brominated diphenyl ethers. 28 , 29 To perform dehalorespiration, Dehalococcoides need gaseous hydrogen, which they cannot produce themselves, thus cooperation in consortium with other bacteria is crucial for their effectiveness. 25 − 28 Rhodopseudomonas palustris is a Gram-negative versatile photosynthetic bacterium that can also degrade BFRs, but what is more, emits hydrogen.…”