Soil microecosystem collapse and revival: Dual-targeted HMX toxicity versus secretion system-mediated synthetic...

The persistent energetic compound cyclotetramethylene tetranitramine (HMX) poses increasing ecological threats. However, its micro-ecological toxicity mechanisms and effective remediation strategies remain inadequately understood. This study aimed to elucidate HMX's inhibitory mechanisms on soil microecology and develop a synergistic synthetic microbiome for effective remediation. HMX exhibited high persistence (94.4 % residual after 40 days) and acts through a 'dual-target inhibition' mechanism in soil: 1) inhibiting cytochrome c oxidase, disrupting the electron transport chain and reducing ATP synthesis; 2) chelating Zn²⁺/Ni²⁺ cofactors, inactivating key enzymes like β-glucosidase (reduced by 63.4 %). These actions culminated in a dual "energy-nutrition" crisis, suppressed functional genes (pccA, nosZ, phoD), and reduced microbial diversity (OTUs decreased by 11.7 %). Metabolomic analysis revealed five HMX transformation pathways in soil. To address this, a synthetic microbiome of six efficient strains (e.g., Bacillus megaterium) was constructed. This consortium achieved HMX degradation via a secretion system-mediated extracellular enzymatic cascade, confirmed by product deposition on cell surfaces (degradation rate: 84.7-96.4 % in 48 h). The ring-opening products were assimilated into the TCA cycle, fueling lipid and nucleotide metabolism. Inoculation with this functional consortium for 40 days successfully restored soil health, achieving 92.4 % HMX removal, a 3.11-fold increase in respiration, and recovered alpha diversity. This study provides a novel "microbiome-enhanced element cycle steady-state" paradigm for remediating military-contaminated sites.