Metabolic triage under oxidative stress: Peracetic acid drives Listeria monocytogenes into a persistent,...

The formation of Small Colony Variants (SCVs) by environmental biological hazards represents a formidable challenge to hazard detection and mitigation in engineered environments. In the present study, the physiological characteristics and formation mechanisms of Listeria monocytogenes SCVs induced by peroxyacetic acid (PAA) were investigated. PAA exposure resulted in the emergence of transient, miniaturized SCVs characterized by metabolic dormancy, indicated by an extended lag phase, reduced enzymatic activity, and ATP depletion. Transcriptional analysis revealed upregulation of stress response (sigB) and efflux (mdrL) genes, with concurrent downregulation of virulence (hly, inlA) and metabolic (betL, ftsZ) genes. Despite flaA upregulation, SCVs exhibited impaired motility but enhanced biofilm formation. Physiologically, SCVs displayed membrane hyperpolarization, elevated intracellular ROS, and cross-protection against acid, thermal, and osmotic stresses. Crucially, inhibition of ATP synthesis using CCCP shifted the population from culturable SCVs to a non-culturable state, confirming that SCV formation is an active, energy-dependent adaptation rather than a passive injury. Furthermore, while invasion capability was compromised, cell surface hydrophobicity and adhesion were significantly increased. These findings demonstrate that PAA drives L. monocytogenes into a defensive, dormant state that prioritizes persistence over pathogenesis, providing new insights into the toxicological responses and persistence strategies of this biological hazard under environmental oxidative stress.