Soil fungi isolated from DDT-polluted soils: assessment of tolerance, interspecific metabolic diversity and efficacy of rhizo-bioremediation

DDT (dichloro-diphenyl-trichloroethane) was widely used worldwide to control agricultural pests and vectors of several insect-borne human diseases, but its use was banned in most industrialized countries since 1972 due to toxicological concerns. However, due to its persistence in the environment, residues still remain in environ-mental compartments becoming long-term sources of exposure affecting organisms. The metabolic and enzy-matic versatility of fungi can be exploited for DDT biodegradation purposes. We have selected two fungal strains (Trichoderma harzianum and Rhizopus stolonifer) from DDT-contaminated agricultural soils, to study their tolerance to high concentration of DDT and to evaluate fungal interspecific functional diversity and catabolic versatility at the presence of DDT, by using Phenotype MicroArray™ system. Both strains showed clear toler-ance to high DDT concentration. Fungi were able to use the most of available microplate substrates, resulting in both high metabolic versatility and relevant ecological functionality in the colonisation of new sub-strates/habitats. The phenotype profile highlighted both inibithion and stimulation of co-metabolic activities in the presence of this xenobiotic, suggesting the activation of specific metabolic responses to cope with chemical stress. Rhizo-bioremediation trials were also performed using Cucurbita pepo cv. Soraya plants. Both fungi in-creased the capacity of the plant to uptake DDT isomers and metabolites in roots. The increased uptake was reflected also in higher translocation to green-tissues of the plant which would ease removal of residues from polluted sites. The results showed that the fungal species studied might provide powerful insight into the po-tentiality of rhizo-bioremediation.