Microbial communities associated with the biotransformation potential of insensitive explosives in surface soils

New insensitive explosive formulations containing 2,4-dinitroanisole (DNAN) and/or 3-nitro-1,2,4-triazole-5-one (NTO) have recently been incorporated into existing munitions. However, very little is known about the fate, toxicity, and microbial communities that degrade these new explosives. The objectives of this project were to determine the biodegradation rates and mechanisms of IMX-101, IMX-104, NTO, and DNAN, and to characterize and compare the microbial diversity of these explosive-degrading communities. Aerobic and anaerobic degradation rates were determined in soil microcosms with and without supplemental carbon and nitrogen. High throughput 16S rRNA gene sequencing was used to characterize soil microbial diversity and principle components analysis (PCoA) was used to compare the communities between treatments. Biological degradation of DNAN and NTO occurred under aerobic and anaerobic conditions both as the pure compounds and in the IMX formulations. The extents and rates of biodegradation were generally greater in the presence of supplemental carbon or under anaerobic conditions. Community analyses indicated the presence of dominant phyla belonging to the Proteobacteria, Firmicutes, Acidobacteria, and Bacteriodetes. Initial PCoA analysis of the microbial beta diversity hasn’t shown significant trends caused by exposure or biodegradation of the IMX formulations, NTO, or DNAN. The soil microbial communities across the three soils and treatments are being evaluated further to determine which phylotypes increase in abundance following NTO or DNAN degradation and thus may be benefitting from this degradation. Fundamental knowledge on the fate and effects of these new explosives can inform best management practices that sustain ecosystems and mission requirements.