Monitoring for the Dehalogenating Bacterium

Environmental cleanup has become a top priority worldwide. Spills and disposal methods of the past have led to contaminated soils, sediments, ground waters and other areas that now must be decontaminated before they can be used beneficially. Government programs and regulations that focus more specifically on the issue of hazardous waste are now forcing companies to clean up contaminated sites.

Traditional methods used to clean up sites, such as removal of soils or pump and treat methods for aquifers, are costly and inefficient. The main obstacles associated with cleaning up a polluted site are how to remove the hazardous material and then where to dispose of it. A current method that allows companies to minimize these issues is bioremediation.

Bioremediation is a technique that uses naturally-occurring processes in a focused manner to speed up what would occur slowly over time. One of the most commonly-used methods involved in bioremediation is bioaugmentation, which is the treatment of contaminated sites with specific bacteria that have the ability to break down hazardous chemicals and convert them into non-toxic compounds that will be readily removed or absorbed by nature and will no longer cause further harm to the environment.

One such organism is the dehalogenating bacterium Dehalococcoides ethenogenes. Introduction of this bacterium to sites that have been contaminated with chlorinated solvents and other byproducts from industrial cleaners, such as tetrachloroethene (PCE), trichloroethene (TCE), dichloroethene (DCE), and vinyl chloride (VC), has been shown to increase the rate at which these compounds are removed from the environment.

Several bacterial groups have the ability to break down compounds such as PCE and TCE into DCE and vinyl chloride, but they do not have the capability to further carry out the steps required to remove these later compounds, which are highly toxic, from the environment. Dehalococcoides spp. are known to have the ability to break down DCE to VC, but only one species from this group, D. ethenogenes, has the capability to facilitate the final conversion of vinyl chloride into ethene which is far less toxic and is readily removed from the environment by other naturally-occurring processes.

Testing for dehalogenating bacteria and other organisms involved in remediation is a difficult process. These organisms are predominantly anaerobic and have such specialized growth requirements that it is very difficult to grow them in the lab, let alone enumerate them effectively. The use of DNA-based technologies has made this task much easier. Molecular methods such as PCR and Real Time-PCR (QPCR) are invaluable tools that have allowed researchers to study these organisms and to quantitate them accurately with a high degree of certainty from field samples. Gene targets for studying these organisms range from universal 16s rDNA genes to more specialized genes such as tceA and vcrA that are involved in the enzymatic pathways responsible for the final degradation processes.

Microbac Laboratories has now added quantitative analysis for Dehalococcoides ethenogenes to its molecular department capabilities. Along with detection of D. ethenogenes, Microbac can now quantitate levels of Dehalococcoides in a sample to aid in-site analysis for bioremediation plans. This will allow remediators to follow the progression of the clean-up process and to decide whether naturally-occurring communities are sufficient to deal with the contamination issue or if the site will require further augmentation with growth modifiers or bacterial cultures.


Authored by Robert Brooks, Microbac Laboratories, Inc.