Molybdenum disulfide nanosheets promote the plasmid-mediated conjugative transfer of antibiotic resistance genes

The environmental safety of nanoscale molybdenum disulfide (MoS₂) has attracted considerable attention, but its influence on the horizontal migration of antibiotic resistance genes and the ecological risks entailed have not been reported. This study addressed the influence of exposure to MoS₂ at different concentrations up to 100 mg/L on the conjugative transfer of antibiotic resistance genes carried by RP4 plasmids with two strains of Escherichia coli. As a result, MoS₂ facilitated RP4 plasmid-mediated conjugative transfer in a dose-dependent manner. The conjugation of RP4 plasmids was enhanced as much as 7-fold. The promoting effect is mainly attributable to increased membrane permeability, oxidative stress induced by reactive oxygen species, changes in extracellular polymer secretion and differential expression of the genes involved in horizontal gene transfer. The data highlight the distinct dose dependence of the conjugative transfer of antibiotic resistance genes and the need to improve awareness of the ecological and health risks of nanoscale transition metal dichalcogenides.