A 1,1,1-Trichloroethane-Degrading Anaerobic Mixed Microbial Culture Enhances Biotransformation of Mixtures of Chlorinated Ethenes and Ethanes

Abstract

-TCA) is a common groundwater pollutant as a result of improper disposal and accidental spills. It is often found as a cocontaminant with trichloroethene (TCE) and inhibits some TCEdegrading microorganisms. 1,1,1-TCA removal is therefore required for effective bioremediation of sites contaminated with mixed chlorinated organics. This study characterized MS, a 1,1,1-TCA-degrading, anaerobic, mixed microbial culture derived from a 1,1,1-TCA-contaminated site in the northeastern United States. MS reductively dechlorinated 1,1,1-TCA to 1,1-dichloroethane (1,1-DCA) and then to monochloroethane (CA) but not further. Cloning of bacterial 16S rRNA genes revealed among other organisms the presence of a Dehalobacter sp. and a Desulfovibrio sp., which are both phylogenetically related to known dehalorespiring strains. Monitoring of these populations with species-specific quantitative PCR during degradation of 1,1,1-TCA and 1,1-DCA showed that Dehalobacter proliferated during dechlorination. Dehalobacter growth was dechlorination dependent, whereas Desulfovibrio growth was dechlorination independent. Experiments were also performed to test whether MS could enhance TCE degradation in the presence of inhibiting levels of 1,1,1-TCA. Dechlorination of cis-dichloroethene (cDCE) and vinyl chloride (VC) in KB-1, a chloroethenedegrading culture used for bioaugmentation, was inhibited with 1,1,1-TCA present. When KB-1 and MS were coinoculated, degradation of cDCE and VC to ethene proceeded as soon as the 1,1,1-TCA was dechlorinated to 1,1-DCA by MS. This demonstrated the potential application of the MS and KB-1 cultures for cobioaugmentation of sites cocontaminated with 1,1,1-TCA and TCE.

Identification of chlorinated solvents degradation zones in clay till by high resolution chemical, microbial and compound specific isotope analysis

“…The degradation of chlorinated ethanes such as 1,1,1-TCA involves a range of biotic and abiotic transformations in subsurface systems as reviewed by Scheutz et al (2011). The presence of 1,1,1-TCA in combination with chlorinated ethenes complicates the degradation of chlorinated ethenes as 1,1,1-TCA has been found to have an inhibitory effect on the reductive dechlorination of cis-DCE and VC (Chan et al, 2011;Duhamel et al, 2002;Grostern and Edwards, 2006;Scheutz et al, 2011).…”

Stable carbon isotope analysis to distinguish biotic and abiotic degradation of 1,1,1-trichloroethane in groundwater sediments

“…SI3). CA has been reported as the terminal dechlorination product of 1,1,1-TCA by 1,1,1-TCA degrading cultures in laboratory microcosm studies by Grostern and Edwards (2006) and others (referenced in Scheutz et al, 2011).…”

Overview of organohalide-respiring bacteria and a proposal for a classification system for reductive dehalogenases

“…Dehalococcoides mccartyi strain MB [60,61]). rdhA genes from consortia (KB-1, ACT-3 and WL) were included in cases where metagenome sequences or quantitative PCR studies allow connection of rdhA sequences with specific OHRB genera [24,[84][85][86]. Additionally, the rdhA genes were required to be full-length or close to full-length (greater than 300 amino acids), which excluded many partial rdhA genes in the database.…”