Regulating oxygen avaibility mitigates oxidative stresses-induced antibiotic resistance gene expression in E. coli under climate warming

Abstract

Climate warming presents a critical challenge to global ecosystems, with rising temperatures inducing the emergence of antibiotic resistance genes (ARGs) in aquatic environments. Given the natural correlation between rising temperatures and declining oxygen levels in aquatic systems, we hypothesized that decoupling temperature and oxygen stress would reveal regulatory mechanisms mitigating ARG expression under future warming scenarios. Through transcriptomic analysis of Escherichia coli under temperature upshift (TU), dissolved oxygen upshift (DOU), and dissolved oxygen downshift (DOD), we identified 101 distinct regulons with 8 showing significant regulation (|log2FC| > 1.5). Key regulons (cusR, mhpR, pdhR) exhibited parallel regulation under TU and DOD but opposite patterns under DOU, revealing mechanistic links between temperature and oxygen stress through shared regulatory networks involving oxidative stress regulators (oxyR-metR) and aerobic respiration control (arcA-betI). Evolved strains from controlled temperature-oxygen fluctuations demonstrated sophisticated metabolic reprogramming, including enhanced carbohydrate metabolism, nucleotide biosynthesis, and putrescine degradation. These strains exhibited optimized energy metabolism through reduced downregulation of ATP synthase subunits and NADH dehydrogenase complex genes, preserving electron transport chain function under thermal stress. Simultaneously, they displayed strategic ROS management with reduced upregulation of peroxiredoxin (ahpF) and Cu/Zn-SOD (sodC), while reversing Fe-SOD (sodB) expression patterns. To validate these mechanisms, we conducted independent batch reactor experiments with two dissolved oxygen conditions (2-8 mg/L) using intermittent perturbation patterns. Non-targeted metaproteomic analysis revealed that lowered oxygen levels (2 vs. 8 mg/L) triggered comprehensive reconfiguration of antimicrobial resistance mechanisms, including downregulation of penicillin-binding proteins, alanine racemase, and cationic antimicrobial peptide resistance systems, while modulating two-component regulatory networks. Our findings reveal coordinated regulatory networks optimizing energy metabolism, ROS management, and antibiotic resistance, suggesting oxygen management strategies could mitigate climate warming effects on antibiotic resistance in aquatic environments.