Isolation and molecular characterization of bacteria from the gut of Eisenia fetida for biodegradation of 4,4 DDT

Abstract

There is a growing interest in the bio-application of microorganisms from the gut of earthworms on the bio-transformation of persistent and toxic pollutants during vermifiltration. Earthworms harbor beneficial microbes in their gut which symbiotically aid in biodegradation of pollutants in their drilosphere. Dichlorodiphenyltrichloroethane is an example of polychlorinated hydrocarbons and metabolites thereof that are persistent in the environment and are toxic to humans and animals. This study aimed at isolating and identifying 4,4 dichlorodiphenyltrichloroethane degrading microorganisms in the gut of Eisenia fetida acclimatized to sewage. Six pure isolates obtained from gut contents were cultured in minimum salt media supplemented with 15 mgL-1 dichlorodiphenyltrichloroethane followed by glucose yeast extract agar sprayed with 1% 4,4 DDT in ether (v/v). Two pure isolates positive for 4,4 dichlorodiphenyltrichloroethane biodegradation were inoculated on minimum salt yeast extract media containing 15 mgL-1 4,4 dichlorodiphenyltrichloroethane. The resulting metabolites were identified using Gas Chromatography. The positive isolates were identified using 16S rRNA gene analysis as Rhodococcus genus and the Bacillus genus, exhibiting 88.36% and 85.22% 4.4 DDT degradation respectively. The study demonstrated DDT-degradation by bacteria from the gut of Eisenia fetida. These findings can be useful in optimization of vermifilters for biodegradation of dichlorodiphenyltrichloroethane and other xenobiotics.