Fungal interactions with the explosive RDX (hexahydro-1,3,5-trinitro-1,3,3-triazine)

The bacterially mediated, anaerobic biodegradation of the explosive RDX (hexahydro 1,3,5 trinitro-1,3,5-triazine) is well established. Reports of successful mineralization of RDX by white rot fungi, and the enhanced transformation of RDX in stirred as compared to static composts, led us to study the possible aerobic role of several filamentous fungi in RDX biodegradation. Cladosporium resinae, Cunninghamella echinulata var elegans, Cyathus pallidus and Phanerochaete chrysosporium were grown in the presence of 50 and 100 mu g ml(-1) of RDX on a vegetable juice agar. Little inhibition of radial growth was observed, while control cultures with TNT exhibited substantial inhibition. When 100 mu g ml(-1) of RDX was added to pre-grown mycelia in a nonlignolytic liquid medium, between 12 and 31% was lost after 3 days. In similar experiments using C-14-RDX, most of the label remained in the organic fraction, and little or none was found in the aqueous fraction, the volatile fraction or incorporated into cell walls. Although disappearance of RDX was observed for all four species tested, there was no evidence of mineralization. Mixed cultures of microorganisms, including both bacteria and fungi, merit further study as agents for the decontamination of munitions-contaminated soils.