Open AccessGrowth of Dehalococcoides spp. and increased abundance of reductive dehalogenase genes in anaerobic PCB-contaminated sediment microcosms
Author(s) -
Jessica M Ewald,
Shelby V Humes,
Andrés Martínez,
Jerald L. Schnoor,
Timothy E. Mattes
Publication year - 2019
Publication title -
environmental science and pollution research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.845
H-Index - 113
eISSN - 1614-7499
pISSN - 0944-1344
DOI - 10.1007/s11356-019-05571-7
Subject(s) - dehalococcoides , dehalogenase , reductive dechlorination , microcosm , betaproteobacteria , environmental chemistry , biology , bioremediation , sediment , microbiology and biotechnology , ecology , contamination , 16s ribosomal rna , chemistry , bacteria , genetics , actinobacteria , paleontology , organic chemistry , vinyl chloride , copolymer , polymer
Polychlorinated biphenyls (PCBs) contaminate 19% of US Superfund sites and represent a serious risk to human and environmental health. One promising strategy to remediate PCB-contaminated sediments utilizes organohalide-respiring bacteria (OHRB) that dechlorinate PCBs.However, functional genes that act as biomarkers for PCB dechlorination processes (i.e., reductive dehalogenase genes) are poorly understood. Here, we developed anaerobic sediment microcosms that harbor an OHRB community dominated by the genus Dehalococcoides. During the 430-day microcosm incubation, Dehalococcoides 16S rRNA sequences increased two orders of magnitude to 10 7 copies/g of sediment, and at the same time, PCB118 decreased by as much as 70%. In addition, the OHRB community dechlorinated a range of penta- and tetra-chlorinated PCB congeners including PCBs 66, 70 + 74 + 76, 95, 90 + 101, and PCB110 without exogenous electron donor. We quantified candidate reductive dehalogenase (RDase) genes over a 430-day incubation period and found rd14, a reductive dehalogenase that belongs to Dehalococcoides mccartyi strain CG5, was enriched to 10 7 copies/g of sediment. At the same time, pcbA5 was enriched to only 10 5 copies/g of sediment. A survey for additional RDase genes revealed sequences similar to strain CG5's rd4 and rd8. In addition to demonstrating the PCB dechlorination potential of native microbial communities in contaminated freshwater sediments, our results suggest candidate functional genes with previously unexplored potential could serve as biomarkers of PCB dechlorination processes.