Optimization of microbial assisted phytoremediation of soils contaminated with pesticides.

580 microbial strains were isolated from the rhizosphere of the plants Cucurbita pepo L. and Xanthium strumarium grown on soil contaminated with dichlorodiphenyltrichloroethane (DDT) and its metabolites. During the cultivation, two bacterial strains were selected because of their ability to grow on media containing 0.5-5.0 mg L-1 of dichlorodiphenyldichloroethylene (DDE) as the sole carbon source. They were identified as Bacillus vallismortis and Bacillus aryabhattai. Both of these species were shown to have a high capacity for the utilization of DDE - more than 90% of which was consumed after 21 days of cultivation. Laboratory experiments were carried out then to assess the possibility of using these strains for the decontamination of organochlorine pesticides (OCPs) contaminated soils. Inoculation of C. pepo and X. strumarium with our isolates B. vallismortis and B. aryabhattai resulted in a reduction of the pollutant stress to the plants as shown by an increase both in aboveground and in root biomass. The microorganisms enhanced the uptake and phytostabilization potential of C. pepo and X. strumarium and can be applied for the treatment of DDE contaminated soils.