From pristine bacteria to neo-transformants: Alterations in adaptive survival strategies and endogenous responses under re-stress.

Abstract

Antibiotic and non-antibiotic pollutants accelerate dissemination of antibiotic resistance genes (ARGs) via oxidative stress, yet most studies lack a full adaptive selection trajectory from naive states to resistance acquisition and subsequent re-exposure. Given the potential for sublethal photocatalytic stress to facilitate ARG dissemination, We constructed a four-stage continuum with 0.1 mg/L molybdenum disulfide (MoS2) as a representative photocatalytic nanomaterial, including pristine bacteria (PB), bacteria exposed to MoS2 under light/dark, respectively (LCB/DCB), pUC19-transformed ARBs from LCB/DCB, respectively (LTB/DTB), and re-exposed to MoS2 under light/dark, respectively (LTB+L/DTB+D). Then, differences in oxidative stress, membrane permeability, energy metabolism, extracellular polymeric substance (EPS) composition, transcriptomic regulation under light/dark conditions, and adaptive responses of LTB/DTB versus PB to various pollutants were investigated. Light-exposed MoS2 induced stronger oxidative stress than darkness triggering reactive oxygen species (ROS) burst, elevated antioxidant activities, lipid peroxidation, activated energy metabolism in LCB. LTB/DTB underwent metabolic remodeling with reduced adenosine triphosphate (ATP), ROS reversion to PB baseline, and lowered protein/polysaccharide (PN/PS) ratio but thickened polysaccharide layers to reduce exchange in EPS, indicating resource conservation. Upon re-stress, LTB+L displayed enhanced fitness including stronger ROS homeostasis, amplified antioxidant defenses and membrane integrity, while DTB+D showed certain advantages but weaker than LTB+L. Transcriptomics confirmed LTB/DTB upregulate nucleotide synthesis and membrane defense genes, whereas LCB/DCB activated catabolic pathways and antioxidant responses. Meanwhile, LTB exhibits stronger environmental adaptability than DTB. Collectively, this work reveals that MoS2 drive adaption of high-risk ARB populations under light conditions, thereby establishing a mechanistic framework for assessing ecological risks of photocatalytic nanomaterials.