Dehalorespiration with Polychlorinated Biphenyls by an Anaerobic Ultramicrobacterium

Abstract

Strain DF-1 was inoculated into sediments contaminated with weathered Aroclor 1260 to determine whether the augmentation would stimulate the dechlorination of congeners as they occur in the environment, adsorbed to sediment particles and in the presence of an indigenous bacterial population. The 8.9 mol% net decrease in double-flanked chlorines observed after bioaugmentation with DF-1 cannot be calculated directly from the abridged data set in Table 1 on page 2092 that highlighted only some of the changes in absolute amounts. A revised Table 1 (see following page) shows the congener profile that was used to calculate the moles percent decrease catalyzed by DF-1. There are disparities between the tables that resulted from normalization of the data in the published Table 1 to dry mass of soil. The revised moles percent analysis shows that non-double-flanked PCBs 63 and 153 did not decrease with the addition of DF-1, but a slight reduction of non-doubleflanked PCBs 136 and 66/95 was significant, possibly a result of DF-1 dechlorination products serving as "primers" that stimulated the activities by the indigenous population. The relative reduction of double-flanked PCBs 180 and 202 (and coelutants) also appears to be greater. Although we cannot confirm which double-flanked dechlorination reactions were catalyzed exclusively by DF-1, the revised table clearly supports our conclusion that bioaugmentation with DF-1 stimulated reductive dechlorination of weathered Aroclor-contaminated soil.

Genome sequencing of a single cell of the widely distributed marine subsurface Dehalococcoidia, phylum Chloroflexi

“…To date, our knowledge about the metabolic properties of members of this clade is derived from several closely related cultivated strains, that is, Dehalococcoides mccartyi strains (Lö ffler et al, 2012), Dehalogenimonas lykanthroporepellens strains (Moe et al, 2009), Dehalogenimonas alkenigignens strains (Bowman et al, 2012) and 'Dehalobium chlorocoercia' strain DF-1 (May et al, 2008). These isolates are unified by their ability to grow via organohalide respiration, that is, they use halogenated organic compounds as terminal electron acceptors while using hydrogen as an electron donor in an anaerobic respiration (Tas et al, 2010).…”

Quantifying Enhanced Microbial Dehalogenation Impacting the Fate and Transport of Organohalide Mixtures in Contaminated Sediments

“…All 13 phylotypes from the soil samples clustered within the dechlorinating Chloroflexi group. Some of the soil phylotypes grouped with the Dehalococcoides-group (Bedard et al, 2006;He et al, 2005;Waller et al, 2005) and the DF-1/SF-1-group May et al, 2008), whereas other putative dechlorinating soil phylotypes grouped within the broader Chloroflexi group. Two previous reports on bacterial communities in PCB contaminated soil identified bacteria closely related to Proteobacteria, the Holophage-Acidobacterium phylum, Actinobacteria, and Plantomycetales and Cytophagales (Nogales et al, 1999(Nogales et al, , 2001).…”

“…In the presence of weathered PCBs where the concentration is more limiting both kinetic and availability issues might affect the effectiveness of in situ PCB transformation. A recent study by May et al (2008) showed that bioaugmentation with DF-1 stimulated the reductive dechlorination of Aroclor 1260 (>5 ppm) in contaminated soil, which suggests that using bioaugmentation for treatment of low levels of weathered PCBs is feasible. Furthermore, found that the addition of D. ethenogenes strain 195 and pentachloronitrobenzene to microcosms stimulated the dechlorination of weathered PCB in contaminated sediments from Anacostia River, Washington DC.…”

“…Effective, economical methods for remediation of PCB contaminated sediments are lacking, however, progress has been made in understanding potential for biotransformation of PCBs in recent years. Discovery that anaerobic bacteria of the phylum Chloroflexi, including the genus Dehalococcoides and more distantly-related taxons, can dechlorinate PCBs may offer a promising avenue for bioremediation (Wu et al, 2000;Cutter et al, 2001;Fennell et al, 2004;Watts et al, 2005;Fagervold et al, 2005;Fagervold et al, 2007;Bedard et al, 2007;May et al, 2008;; and see review by Bedard, 2008). In this study we evaluated whether stimulating native Dehalococcoides populations or bioaugmentation could increase dechlorination of low concentrations of weathered PCBs, and whether the treatment effects persist over a relatively long time frame (> 1 year).…”

“…However, the effectiveness of bioaugmentation for dechlorinating low levels of PCBs most commonly associated with weathered PCB contaminated sites where both kinetic and availability issues might affect the effectiveness of in situ PCB transformation is currently unknown (Fish et al, 2001). A recent report by May et al (2008) showed that bioaugmentation with DF-1 stimulated the reductive dechlorination of weathered Aroclor 1260 (4.6 ppm) in contaminated soil microcosms, and found that the addition of "D. ethenogenes" and pentachloronitrobenzene stimulated the dechlorination of weathered Aroclors 1248, 1254 and 1260 (2.1 ppm) in sediment microcosms. Combined, these results suggest that using bioaugmentation for low levels of weathered PCBs is feasible.…”