PCB dechlorination hotspots and reductive dehalogenase genes in sediments from a contaminated wastewater lagoon

Abstract

Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants that are distributed worldwide. Although industrial PCB production has stopped, legacy contamination can be traced to several different commercial mixtures (e.g., Aroclors in the USA). Despite their persistence, PCBs are subject to naturally occurring biodegradation processes, although the microbes and enzymes involved are poorly understood. The biodegradation potential of PCB-contaminated sediments in a wastewater lagoon located in Virginia (USA) was studied. Total PCB concentrations in sediments ranged from 6.34 to 12,700 mg/kg. PCB congener profiles in sediment sample were similar to Aroclor 1248; however, PCB congener profiles at several locations showed evidence of dechlorination. The sediment microbial community structure varied among samples but was dominated by Proteobacteria and Firmicutes. The relative abundance of putative dechlorinating Chloroflexi (including Dehalococcoides sp.) was 0.01–0.19% among the sediment samples, with Dehalococcoides sp. representing 0.6–14.8% of this group. Other possible PCB dechlorinators present included the Clostridia and the Geobacteraceae. A PCR survey for potential PCB reductive dehalogenase genes (RDases) yielded 11 sequences related to RDase genes in PCB-respiring Dehalococcoides mccartyi strain CG5 and PCB-dechlorinating D. mccartyi strain CBDB1. This is the first study to retrieve potential PCB RDase genes from unenriched PCB-contaminated sediments.

Presence, Diversity, and Enrichment of Respiratory Reductive Dehalogenase and Non-respiratory Hydrolytic and Oxidative Dehalogenase Genes in Terrestrial Environments

“…Some putative RDase and dehalogenase genes were common to multiple lake sediments and enrichment cultures, while other genes were specific to a single location or a single culture. Previously published work found that the RDase genes or bacteria known to contain these enzymes were widely present at contaminated sites (Hendrickson et al, 2002; Müller et al, 2004; Mattes et al, 2017). RDase genes have also been identified in uncontaminated marine environments where concentrations of Cl-NOM are higher (Kawai et al, 2014) and in select terrestrial environments (Biderre-Petit et al, 2016; Weigold et al, 2016).…”

Microbial communities in polychlorinated biphenyl (PCB)-contaminated wastewater lagoon sediments: PCB congener, quantitative PCR, and 16S rRNA gene amplicon sequencing datasets

“…In September 2015, sediment samples were collected from 27 locations within the lagoon in an approximate grid pattern [1] . This was achieved by navigating to the desired sampling location in a small boat and using a hand auger to collect sediment samples.…”

“…The PCB congener, 16S rRNA gene amplicon sequencing, and qPCR datasets were obtained, in duplicate, from 27 sediment sample locations (for a total of 54 sediment samples) within a PCB-contaminated emergency overflow lagoon [1] . The latitude and longitude coordinates for the PCB-contaminated emergency overflow lagoon located are 37°06′47″N, 79°16′23″W.…”

Identifying New ‘Hotspot’ Heavy Metal Contamination in Industrial Zone Soil

“…Inorganic pollutants (TPH, PCB and heavy metals Cd, Pb, Ni, Cu and Hg) can be strongly accumulated in soil, water and plants, and significant quantities of toxic metals are discharged into ecosystems [9]. TPH and PCB are ubiquitous class organic pollutants that are a human health risk [10]. Heavy metals (HMs) occur naturally in the environment; however, the concentration of some HMs has increased tremendously since the beginning of the industrial revolution due to many industrial activities [11].…”