Microcosm studies on the degradation of o,p′- and p,p′-DDT, DDE, and DDD in a muck soil

The muck soils of the north shore of Lake Apopka, near Orlando, Florida, USA are high in organic matter, inorganic nutrients, and water content. Ideally suited for agriculture, these soils have been exposed to a wide variety of agrochemicals. Some of the more recalcitrant organochlorine pesticides, such as DDT and its degradation products DDD and DDE, have persisted in the soil for over 30 years. Using the extracellular enzymes from wood rot fungi, it was demonstrated that it is possible to substantially reduce the amount of the o,p' and p,p' isomers of DDT, DDD, and DDE in this soil by more than 60% in 3 weeks. A fungal species with 99% DNA homology to Nectria mariannaeae was isolated from this muck soil and identified by nucleotide sequencing. When grown under nitrogen-limited conditions, this Nectria sp. has been shown to be comparable to Phanerochaete chrysosporium (ATCC 24725) in producing extracellular factors (or agents) that are capable of degrading these recalcitrant chlorinated chemicals.