Dehalocococcoides sp. GT
   
   
 

The bar in each image represents 200, 250, 250, 167 n moving clockwise beginning in the upper left.

Widespread groundwater contamination with chlorinated ethenes exists, and while some organisms dechlorinate tetrachloroethene (PCE) to trichloroethene (TCE) and dichloroethenes (DCEs), DCEs are toxic, and accumulate at PCE/TCE-impacted sites.  Strain GT dechlorinates TCE directly to ethene and is therefore an ideal candidate for overcoming the "DCE stall" and avoids formation of carcinogenic vinyl chloride (VC), both major obstacles in bioremediating chlorinated ethene contaminated sites.  Prior to Strain GT, only two other Dehalococcoides isolates that grow with VC and efficiently produce ethene were obtained, strains BAV1 and VS.  Strain GT possesses multiple reductive dehalogenase (RDase) genes suggesting that this organism dechlorinates a spectrum of chloroorganic compounds.  Further, the tceA gene, responsible for TCE reductive dechlorination in Dehalococcoides ethenogenes strain 195 and Dehalococcoides sp. strain FL2, is absent in strain GT suggesting that a different TCE RDase operates in strain GT.  Comparing the degree of gene similarities between closely related Dehalococcoides strains with distinctive characteristics will provide crucial information about RDase gene dissemination and the evolution of this poorly understood microbial group vital to the bioremediation of halogenated pollutants.

Strain GT is a key dechlorinator in Bio-Dechlor INOCULUM (BDI), a bioaugmentation consortium that was successfully applied at field sites for establishing bioreactive barriers.  Bioremediation approaches with Dehalococcoides-containing cultures have successfully achieved complete detoxification within relatively shorter time frames than competing technologies, while saving significant amounts of US taxpayer money, thus freeing up funds for other pressing problems or permitting treatment of more sites.

Despite their restricted metabolism, Dehalococcoides populations appear to be distributed in nature.  Our recognition of a biogeochemical chlorine cycle, and the discovery of an enormous diversity of naturally produced chloroorganic compounds might suggest that Dehalococcoides populations evolved a restricted lifestyle based on respiratory reductive dechlorination (i.e, chlororespiration) before mankind dramatically affected the flux of chlorinated chemicals into the environment.  Hence, analysis of the Dehalococcoides sp. strain GT genome could shed new light on the evolution of an ancient, deeply branching bacterial group, including the invention of reductive dechlorination as a respiratory process.