Microbial degradation of DDT residues is one mechanism for loss of DDT from soil. In this review pathways for biodegradation of DDT, DDD, and DDE by bacteria and fungi are described. Biodegradation of DDT residues can proceed in soil, albeit at a slow rate. To enhance degradation in situ a number of strategies are proposed. They include the addition of DDT-metabolising microbes to contaminated soils and/or the manipulation of environmental conditions to enhance the activity of these microbes. Ligninolytic fungi and chlorobiphenyl degrading bacteria are promising candidates for remediation. Flooding of soil and the addition of organic matter can enhance DDT degradation. As biodegradation may be inhibited by lack of access of the microbe to the contaminant, the soil may need to be pre-treated with a surfactant. Unlike DDT, little is known about the biodegradation of DDE, and this knowledge is crucial as DDE can be the predominant residue in some soils.

The source, form, and fate of DDT residues in the environment are reviewed. Discussion is primarily from a New Zealand perspective, where a major use of DDT was the control of soil-dwelling pasture pests. Reasons for the persistence of DDT residues, the association between residues and soil components, and possible degradative and non-degradative losses from soils are discussed.

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Pure cultures of aerobic and anaerobic bacteria capable of oxidation and reductive dehalogenation of chloroethylenes, and aerobic bacteria involved in biodegradation of polychlorinated biphenyls (PCBs) were screened for their ability to cometabolize the persistent pollutant 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE). Bacterial cultures expressing methane monooxygenase (Methylosinus trichosporium), propane monooxygenase (Mycobacterium vaccae) and biphenyl 2,3-dioxygenase enzymes (Pseudomonas fluorescens and Rhodococcus globerulus), as well as bacteria reductively dechlorinating chloroethylenes (Acetobacterium woodii and Clostridium butyricum) could not degrade DDE. Cell-free extracts of M. trichosporium, M. vaccae, P. fluorescens and R. globerulus were also unable to transform DDE, indicating that cell wall and membrane diffusion barriers were not biodegradation limiting. These studies suggest that these bacteria can not degrade DDE, even when provided with cosubstrates that induce chlorophenyl- and dichloroethylene-group transforming enzymes.

Terrabacter sp. strain DDE-1, able to metabolize 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE) in pure culture when induced with biphenyl, was enriched from a 1-1-1-trichloro-2,2-bis(4-chlorophenyl)ethane residue-contaminated agricultural soil. Gas chromatography-mass spectrometry analysis of culture extracts revealed a number of DDE catabolites, including 2-(4′-chlorophenyl)-3,3-dichloropropenoic acid, 2-(4′-chlorophenyl)-2-hydroxy acetic acid, 2-(4′-chlorophenyl) acetic acid, and 4-chlorobenzoic acid.