Biodegradation of Persistent Chlorinated Hydrocarbons Using Selected Freshwater Bacteria

Isolation and selection of potent degradative microorganisms against naturally persistent compounds considered as a powerful means for environmental detoxification. In the present study, the natural biotic capacity of water to degrade a mixture of four chlorinated hydrocarbons; DDT (1,1,1,-trichloro-2,2-bis (p-chlorophenyl) ethane); DDE (1,1-dichloro-2,2-bis (p-chlorophenyl) ethane); Lindane (1,2,3,4,5,6-hexachlorocyclohexane (γ-HCH); Endrin (1,2,3,4,10,10,hexachloro-6,7-epoxy-1, 4,4a,5,6,7,8a-octahydro-1,4-endo-5,8-dimethanophethalene) at two elevated levels (0.05 and 50 ppm) was investigated. Five bacterial species (Pseudmonas cepacia, Enterobacter agglomerans, Arthrobacter sp., Eschericia coli and Staphylococcus aureus) isolated and identified from a heavily polluted lake (L. Mariut) were investigated as biodegraders during the present work. Also, the ability of these pesticides to challenge the growth of the selected species has been examined. The tested bacterial species found to efficiently promote the degradation of the tested compounds. Degradation of DDT, DDE, Lindaine and Endrin were mediated by all the species. At the low concentration (0.05 ppm), the pesticide mixture was diminished by P. cepacia after 24 h exposure. On the other hand, Arthrobacter sp., E. coli, S. aureus and E. agglomerans were able to degrade the pesticide mixture totally after 48, 72, 72 and 96 h, respectively. At the high concentration (50.0 ppm), the tested bacteria were able to degrade >87.0% of the pesticide mixture. The inhibitory effect (p