Dehalococcoides ethenogenes Strain 195, A Novel Eubacterium that Reductively Dechlorinates Tetrachloroethene (PCE) to Ethene.
Final rept. Aug 93-Oct 96,
CORNELL UNIV ITHACA NY DEPT OF CIVIL AND ENVIRONMENTAL ENGINEERING
Pagination or Media Count:
Tetrachioroethene PCE is a human carcinogen, and together with trichloroethane TCE, is widely used. Due to improper handling, they are among the most frequently found groundwater pollutants. A purified, PCE-dechlorinating enrichment culture was developed. This non-methanogenic, non-acetogenic culture could grow with H2 as the electron donor, indicating that H2PCE serves as an electron donoracceptor for energy conservation and growth. A novel anaerobic bacterium which dechlorinates PCE to the non-toxic product ethene ETH, Dehalococcoides ethenogenes strain 195, was isolated from this enrichment. This is the first pure culture capable of complete PCE dechlorination. D. ethenogenes strain 195 is an irregular coccus with an optimal growth temperature of 35 deg C and pH of 6.8-7.5. Phylogenetic analysis indicates that it is a eubacterium which shows no affiliation to known groups. Electron donors tested other than H2 were not utilized nor were electron donors other than TCE, cis-dichloroethene cis-DCE, 1,1-DCE, and dichloroethane, which could be freely interchanged and were dechlorinated to ETH. This organism could not grow on vinyl chloride or trans-DCE when provided as sole electron acceptors, but both were dechlorinated cometabolically by cells previously grown on PCE. The reduction of VC to ETH was the rate-limiting reaction to the complete dechlorination of PCE. PCE, TCE, cis-DCE, and 1,1-DCE inhibited ETH formation from VC when present, but, at low concentrations, their dechlorination coexisted with ETH production. Cultures grown on cis-DCE as sole electron acceptor could not dechlorinate PCE unless PCE and cis-DCE were added together.
- Medicine and Medical Research