Dehalorespiration with Polychlorinated Biphenyls by an Anaerobic Ultramicrobacterium

Abstract

Anaerobic microbial dechlorination is an important step in the detoxification and elimination of polychlorinated biphenyls (PCBs), but a microorganism capable of coupling its growth to PCB dechlorination has not been isolated. Here we describe the isolation from sediment of an ultramicrobacterium, strain DF-1, which is capable of dechlorinating PCBs containing double-flanked chlorines added as single congeners or as Aroclor 1260 in contaminated soil. The isolate requires Desulfovibrio spp. in coculture or cell extract for growth on hydrogen and PCB in mineral medium. This is the first microorganism in pure culture demonstrated to grow by dehalorespiration with PCBs and the first isolate shown to dechlorinate weathered commercial mixtures of PCBs in historically contaminated sediments. The ability of this isolate to grow on PCBs in contaminated sediments represents a significant breakthrough for the development of in situ treatment strategies for this class of persistent organic pollutants.Polychlorinated biphenyls (PCBs) were manufactured between 1930 and 1978, and their widespread use in high-temperature electrical coolants, hydraulic fluids, paints, carbonless paper, and as dedusting agents has resulted in their global distribution in even the most remote regions of the planet and throughout the food chain. The 2005 Priority List of Hazardous Substances (http: //www.atsdr.cdc.gov/cercla/) published by the U.S. Agency for Toxic Substances and Disease Registry ranks PCBs fifth out of 275 substances. Ranking on this list is a combined metric based on the compound's prevalence at facilities within the United States, known or suspected toxicity, and potential for human exposure. With the discovery of Desulfomonile tiedjei strain DCB1 (24) in 1984, the door was opened for the study of bacteria that can reductively dechlorinate halogenated organic compounds that were manufactured for a wide range of applications throughout the 20th century. Subsequently, it was discovered that such bacteria can couple their growth to reductive dehalogenation in a process referred to as dehalorespiration (15) or halorespiration (15,22). There has been an explosion of discoveries in this field, resulting in the identification of dozens of different species and strains that are capable of dechlorinating compounds ranging from chlorinated ethenes (19) to dioxins (5). Most of the bacteria that reductively dechlorinate toxic halogenated industrial pollutants have turned out to be members of the genus Dehalococcoides. Although several of these microorganisms have been successfully developed for commercially viable bioremediation of soils contaminated with chlorinated solvents, a proven effective treatment for in situ treatment of PCBs does not currently exist. As a result, the only accepted treatments for PCBs are remedial technologies such as dredging and capping, which are expensive, disruptive to the environment, and impractical to implement over large areas and in remote locations.Dehalococcoides ethenogenes strain 195, the first of the...

Characterization of the microbial community from the marine sediment of the Venice lagoon capable of reductive dechlorination of coplanar polychlorinated biphenyls (PCBs)

“…This seems to indicate that other forms in addition to sulfate-reducing bacteria were involved in PCB dechlorination in the enrichment microcosms developed in this study. This hypothesis is supported by a recent evidence that the growth and activity of PCB-dechlorinating cultures is associated to the cooccurrence of sulfate-reducing bacteria [33].…”

Distribution of dehalogenation activity in subseafloor sediments of the Nankai Trough subduction zone

“…Members of the genera Dehalobium and Dehalococcoides belong to the class Dehalococcoidetes (subphylum II) within the phylum Chloroflexi [11][12][13]. Dehalobium chlorocoercia strain DF-1, isolated from Charleston harbour in South Carolina, is capable of respiring polychlorinated biphenyls [14,15]. Dehalococcoides mccartyi strain MB, isolated from San Francisco Bay, dechlorinates PCE to trans-1,2-dichloroethene (trans-DCE) [12,16].…”

ERC-group microflex: microbiology of Dehalococcoides-like Chloroflexi

“…Other electron acceptors used by Dehalococcoides species include chlorinated benzenes (Adrian et al 2000), biphenyls (Adrian et al 2009Fennell et al 2004), phenols (Adrian et al 2007, ethenes (Maymó-Gatell et al 1997;He et al 2003), dibenzofurans (Fennell et al 2004, and other halogenated alkanes and alkenes. Recently, a polychlorinated biphenyl dechlorinating strain (May et al 2008) and a strain able to grow by dechlorination of chlorinated propanes and other halogenated aliphates (Yan et al 2009) were identified. Both strains are loosely related to the Dehalococcoides.…”