Interfacial processes governing tetracycline-induced resistance on clay minerals

Soil minerals act as hotspots for antibiotics and microbial activity, posing potential risks for antibiotic resistance (AR) development. Understanding the mechanisms by which mineral interfacial processes regulate AR is critical for developing effective AR mitigation strategies. This study investigated the roles of two representative clay minerals, i.e. montmorillonite and kaolinite, in tetracycline (TET) induced AR. Results showed that kaolinite significantly enhanced bacterial resistance by 15.63-56.06-fold within the experimental concentration range (0.1-2.0 mg/L TET). In contrast, montmorillonite increased resistance at lower TET concentrations (0.1-1.0 mg/L) while decreasing it at higher concentrations (>1.0 mg/L), exhibiting dual concentration-dependence effects. Bacterial-mineral heteroaggregation amplifies TET exposure and bioavailability. Kaolinite increased TET bioavailability by 7.82 %-27.84 % and promoted intracellular TET residue, whereas montmorillonite reduced TET bioavailability by 5.17 % at 1.0 mg/L through interlayer TET adsorption. The sodium ions released by montmorillonite mediated osmotic stress in bacteria, activating ion transporters and leading to lower intracellular TET residue. This mineral-specific stress response synergizes with bioavailability-driven evolution to reshape resistance development. These findings highlight the crucial role of clay mineral interfaces in the development of AR, offering theoretical support for predicting and controlling AR in soil environments.