Identification of Microbial Gene Biomarkers for in situ RDX Biodegradation.

摘要

Objectives of this project were to: (a) elucidate RDX degradation pathways in model RDX-degrading bacteria, (b) design and develop molecular tools to identify genes responsible for RDX biodegradation, and (c) correlate the response of biomarker(s) to concentrations of RDX and/or rates of RDX degradation. Gordonia sp. KTR9 and Shewanella oneidensis MR-1served as model bacterial systems for the aerobic and anaerobic degradation of RDX, respectively. Genome annotation and functional characterization of the plasmid pGKT2 in KTR9 revealed that xplA gene is both necessary and sufficient for RDX degradation. Shewanella oneidensis MR-1 was shown to efficiently degrade RDX anaerobically via two initial routes: (a) sequential N-NO2 reduction to the corresponding nitroso (N-NO) derivatives; and (b) mono-denitration followed by ring cleavage. The qPCR molecular tools described in this report have the potential to be used by remediation specialists for site characterization, treatment recommendations, and for evaluation and optimization of the treatment process. The fundamental information gained in this study suggests that XplA- mediated aerobic denitration of RDX may be subjected to inhibitory effects in response to nitrogen availability. Additional research is required to determine reliable guidelines to inform site managers of specific field concentrations of ammonium and nitrate that will increase RDX treatment times. Also, techniques to effectively lower the inorganic nitrogen concentrations to non-inhibitory levels for the aerobic RDX biodegradation pathway will need to be determined.