ABSTRACT
Explosive compounds are very significant environmental contaminants. Their production, testing, use in conflict, and disposal has led to contaminated soils, sediments, and water around the world (Spain et al. 2000). These materials are intrinsically toxic to microbes, plants, animals, and man. In the United States, it is now a requirement that sites contaminated by these compounds are risk assessed and remediated to acceptable standards determined by sitespecific clean-up goals (Jerger and Woodhull 2000). Various remediation strategies have been adopted to date, and these have involved physical, chemical, and biological approaches (Newcombe and Crawford 2002). Physical techniques such as incineration, activated carbon absorption, and filtration are effective, but generate unwanted residues that still have to be treated. Chemical treatments have been tried, for example precipitation using surfactants and solvent extraction (Kaplan 1990) but again these approaches generate further residues that have to be disposed of. Biological treatments have included biostimulation of existing indigenous microflora and bioaugmentation where an explosive degrading microbial inoculum is added to the contaminated environment (Kaplan 1990). Biological approaches appear to be cost effective alternatives to other methods, but they have had limited success because of microbial sensitivity to toxic levels of explosive, toxic by-products of incomplete degradation and the length of time biological clean-up of a contaminated environment can take (Reddy 1995). This review seeks to summarize available information about the metabolic pathways involved in fungal biodegradation of explosives and to evaluate the distribution of these pathways across the taxonomic groups.
