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Hydroxylated Polychlorinated Biphenyls Are Emerging Legacy Pollutants in Contaminated Sediments.

ABSTRACT: We measured the concentrations of 837 hydroxylated polychlorinated biphenyls (OH-PCBs, in 275 chromatographic peaks) and 209 polychlorinated biphenyls (PCBs, in 174 chromatographic peaks) in sediments from New Bedford Harbor in Massachusetts, Altavista wastewater lagoon in Virginia, and the Indiana Harbor and Ship Canal in Indiana, USA and in the original commercial PCB mixtures Aroclors 1016, 1242, 1248, and 1254. We used the correlation between homologues and the peak responses to quantify the full suite of OH-PCBs including those without authentic standards available. We found that OH-PCB levels are approximately 0.4% of the PCB levels in sediments and less than 0.0025% in Aroclors. The OH-PCB congener distributions of sediments are different from those of Aroclors and are different according to sites. We also identified a previously unknown compound, 4-OH-PCB52, which together with 4'-OH-PCB18 made up almost 30% of the OH-PCBs in New Bedford Harbor sediments but less than 1.2% in the Aroclors and 3.3% in any other sediments. This indicates site-specific environmental transformations of PCBs to OH-PCBs. We conclude that the majority of OH-PCBs in these sediments are generated in the environment. Our findings suggest that these toxic breakdown products of PCBs are prevalent in PCB-contaminated sediments and present an emerging concern for humans and ecosystems.

SUBMITTER: Saktrakulkla P

PROVIDER: S-EPMC8851693 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:We analyzed the transcriptional response of the actinomycete Rhodococcus aetherivorans I24 to biphenyl and polychlorinated biphenyls (PCBs). This species has not been extensively exposed to PCBs, as it was first isolated from a toluene contaminated aquifer, rather than a site contaminated with polychlorinated hydrocarbons. Using a microarray targeting 3524 genes, we assessed gene expression in minimal medium supplemented with various substrates (e.g. PCBs) and in both PCB-contaminated and non-contaminated sediment slurries. Relative to the reference condition (minimal medium supplemented with glucose), 408 genes were up-regulated in the various treatments. In medium and in sediment, PCBs elicited the up-regulation of a common set of 100 genes, including chaperones (groEL), a superoxide dismutase (sodA), alkyl hydroperoxide reductase protein C (ahpC), and a catalase/peroxidase (katG). Analysis of the R. aetherivorans I24 genome sequence identified orthologs of many of the genes in the canonical biphenyl pathway, but very few of these genes were up-regulated in response to PCBs or biphenyl. This study is one of the first which utilizes microarrays to assess the transcriptional response of a soil bacterium to a pollutant under conditions which more closely resemble the natural environment. Our results indicate that the transcriptional response of R. aetherivorans I24 to PCBs, in both medium and sediment, is primarily directed towards reducing oxidative stress, rather than catabolism. In addition, the identification of numerous genes expressed in contaminated soil specifically may have implications for the development of biosensors. Finally, comparative genomic and transcriptomic analyses suggest that the mere presence of orthologs of the required enzymes may not be sufficient to confer a vigorous biphenyl/PCB metabolism. RNA was isolated from cells incubated in the following: sediment from a PCB-contaminated industrial site, uncontaminated sediment from a comparable site, and defined media supplemented with glucose (3 g/L), glucose and biphenyl (3 g/L, 4.5 Î¼M), or glucose and PCBs (3 g/L, 5 mg/L Aroclor 1254). In all cases, there were 3 biological replicates and 2 technical replicates (repeat hybridizations). A total of 3524 genes are represented on the arrays; of these, 41 and 176 are found on the plasmids pRA2 and pRA3, respectively. On average, there are 3 distinct 24nt probes per gene.

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Hydroxylated Polychlorinated Biphenyls Are Emerging Legacy Pollutants in Contaminated Sediments.

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