Characterization of 1,2-dichloroethane (DCA) degrading bacteria isolated from South African waste water

Abstract

1,2-Dichloroethane (DCA), a potential carcinogen that is toxic to both terrestrial and aquatic ecosystems, is one of the most widely produced chemicals in the modern world. It is used as a metal degreaser, solvent, chemical intermediate and fuel additive. Contamination of the environment with DCA results from accidental spills and poor handling. To date, several bacterial isolates, capable of utilizing this compound as a sole carbon and energy source, have been identified in the northern hemisphere. This report focused on the isolation and characterization of bacterial isolates in the southern hemisphere that are capable of degrading DCA. Samples obtained from a waste water treatment plant in Durban, South Africa were batch cultured in minimal medium containing DCA and repeatedly sub-cultured every five days over a 25 day period. A halogen release assay was performed in order to determine whether individual isolates possessed dehalogenase activity. Confirmation of DCA utilization by bacterial isolates that were positive for dehalogenase activity was done by sub-culturing back into minimal medium containing DCA. It was found that five isolates possessed an identical hydrolytic dehalogenase gene following the design of primers based on known hydrolytic dehalogenase genes. Analysis of 16S rDNA sequences indicated that, all the South African isolates belonged to the genus Ancylobacter and were different from each other.

Key words: 1,2- dichloroethane, halogenated hydrocarbon, xenobiotic, dehalogenase.