Under anaerobic conditions, Dehalogenimonas spp. and some Dehalococcoides strains are capable of utilizing chlorinated propanes as growth supporting electron acceptors.  Reductive dechlorination of 1,2,3-trichloropropane (TCP) by Dehalogenominas produces an unstable intermediate which can be hydrolyzed to form allyl alcohol or undergo reactions with sulfide-reducing agents for form allyl sulfides. In Dehalococcoides strains and Dehalogenimonas spp., 1,2-dichloropropane (DCP) undergoes dichloroelimination mediated by a dichloropropane dehalogenase to form propene.

Submit samples for CENSUS qPCR to quantify a halorespiring bacteria and functional genes responsible for anaerobic biodegradation of DCP and TCP.

TARGETCODERELEVANCE / DATA INTERPRETATION
DehalogenimonasDHGThe Dehalogenimonas isolates characterized to date utilize a variety of vicinally chlorinated alkanes including chlorinated propanes (1,2,3-TCP and 1,2-DCP) and chlorinated ethanes (1,1,2,2-TeCA, 1,1,2-TCA, and 1,2-DCA).
DehalococcoidesDHCWhile the range of compounds utilized varies by strain, some Dehalococcoides strains are capable of reductive dechlorination of DCP to propene.
Dichloropropane Dehalogenase1,2-DCPFunctional gene encoding the enzyme responsible for dechlorination of 1,2-DCP.

Although 1,3-dichloropropane (1,3-DCP) can serve as a growth supporting carbon and energy source under aerobic conditions, attempts to enrich and isolate aerobic 1,2,3-trichloropropane (TCP) and 1,2-DCP utilizing bacteria have been unsuccessful to date. Known haloalkane dehalogenase enzymes have shown little activity against chlorinated propanes.

However, chlorinated propanes can be susceptible to aerobic cometabolism. More specifically, methanotrophs expressing soluble methane monooxygenase (sMMO) are capable of co-oxidizing 1,2-DCP, 1,3-DCP and 1,2,3-TCP and cometabolism of 1,2,3-TCP has been also demonstrated for propane oxidizing bacteria. TCP cometabolism has also been observed for mixed cultures of aromatic hydrocarbon degraders that included strains utilizing toluene monooxygenase (RMO, RDEG), phenol hydroxylase (PHE) and toluene dioxygenase (TOD) pathways. However, no attempt was made to link TCP cometabolism to individual oxygenases.

CENSUS qPCR can be performed to quantify soluble methane monooxygenase and propane monooxygenase gnes.

TARGETCODERELEVANCE / DATA INTERPRETATION
Soluble Methane MonooxygenasesMMOWhen expressed, sMMO is capable of co-oxidation of 1,2-DCP, 1,3-DCP and 1,2,3-TCP.
Propane MonooxygenasePPOPropane oxidizing bacteria have been shown to be capable of cometabolism of TCP.

In Situ Microcosms (ISMs)

In Situ Microcosms (ISMs) are field deployed microcosm units containing passive samplers that provide the microbial, chemical, and geochemical data for simultaneous, cost-effective evaluation of multiple remediation options.

For remedy selection at TCP and DCP impacted sites, an ISM study typically includes:

    • An unamended MNA unit to evaluate monitored natural attenuation
    • A BioStim unit amended with an electron donor
    • A BioAug unit amended with a commercial bioaugmentation culture and an electron donor

Each ISM unit contains passive samplers – passive diffusion bags (PDBs) for VOCs analysis of contaminant concentrations, passive geochem samplers for dissolved gases (ethene, ethane, methane) and anions like sulfate, and Bio-Traps® for CENSUS qPCR quantification of Dehalogenimonas, Dehalococcoides, and DCP dehalogenase genes.

By comparing contaminant concentrations, daughter product formation, geochemical conditions, and concentrations of halorespiring bacteria between the MNA, BioStim, and BioAug units, site managers can evaluate each remediation option at a fraction of the cost of a lab bench treatability study or pilot scale study.