Characteristics of RDX degradation and the mechanism of the RDX exposure response in a Klebsiella sp. strain

Abstract Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a high-energy explosive that degrades with difficulty in the natural environment. The use of microbial remediation can effectively restore environments suffering from RDX pollution. In this study, a bacterial strain capable of efficient degradation of RDX was isolated from sewage. The bacterium was identified as a Klebsiella sp. Exposure to RDX at 40 mg L-1 increased the five-day biochemical oxygen demand (BOD5) to 971 mg L-1 and accelerated the logarithmic growth phase to occur at the 7th hour after inoculation, Overall, 81.9% of the RDX was degraded by 24 h. The surface of the bacterial cell became grooved and slightly curved. Levels of intracellular carboxylates, methyl-containing metabolites, primary aromatic amines, PO4-3, and ClO4- were altered after exposure to RDX solution. 362 different metabolites (DEMs) were identified using LC-MS metabolome analysis. Among them, 193 DEMs were upregulated and 169 DEMs were downregulated. The galactose metabolism pathway (ko00052) and the synthesis of other substances (such as UDP-glucose, D -galactose, D -fructose-1,6-bisphosphate, and dihydroxyacetone phosphate) were disrupted when the concentration of RDX was 40 mg L-1. The metabolites of cell membrane and cell wall were destroyed, such as lysophosphatidic acid (LPA) (0:0/16:0), phosphatidylethanolamine, and phosphatidylcholine.