Effects of Elevated Temperature on Dehalococcoides Dechlorination Performance and DNA and RNA Biomarker Abundance

摘要

Coupling thermal treatment with microbial reductive dechlorination is a promising remedy for tetrachloroethene (PCE) and trichloroethene (TCE) contaminated source zones. Laboratory experiments evaluated Dehalococcoides {Dhc) dechlorination performance, viability, and biomarker gene (DNA) and transcript (mRNA) abundances during exposure to elevated temperatures. The PCE-dechlorinating consortja BDI and OW produced ethene when incubated at temperatures of 30 ℃, but vinyl chloride (VC) accumulated when cultures were incubated at 35 or 40 ℃. Cultures incubated at 40 ℃ for less than 49 days resumed VC dechlorination following cooling; however, incubation at 45 ℃ resulted in complete loss of dechlorination activity. Dhc 16S rflNA, bvcA, and vcrA gene abundances in cultures showing complete dechlorination to ethene at 30 ℃ exceeded those measured in cultures incubated at higher temperatures, consistent with observed dechlorination activities. Conversely, biomarker gene transcript abundances per cell in cultures incubated at 35 and 40 ℃ were generally at least one order-of-magnitude greater than those measured in ethene-producing cultures incubated at 30 ℃. Even in cultures accumulating VC, transcription of the vcrA gene, which is implicated in VC-to-ethene dechlorination, was up-regulated. Temperature stress caused the up-regulation of Dhc reductive dehalogenase gene expression indicating that Dhc gene expression measurements should be interpreted cautiously as Dhc biomarker gene transcript abundances may not correlate with dechlorination activity.