The Effects of Polystyrene Nano/Microplastics on the Conjugative Transfer of Antibiotic Resistance Genes Between...

At present, studies on the impacts of nano/microplastics on the conjugative transfer of antibiotic resistance genes (ARGs) have been limited to transfer within the same bacterial species (Escherichia coli, E. coli). There is a lack of research on whether nano/microplastics could cause effects among different species. Therefore, this study investigated the effects and mechanisms of polystyrene nano/microplastics on the conjugative transfer of ARGs from the bacterial donor (E. coli) to the algal recipient (Microcystis aeruginosa, M. aeruginosa). It was found that nanoplastics significantly changed the transfer efficiency. For 20-nm plastics (1 mg/L), the transfer frequency was the highest, which was approximately 4.4 times higher than that of control. However, with further increases in concentration, the transfer frequency declined. This may be related to the death of algae and bacteria following the addition of nanoplastics. The effect of nanoplastics (200 nm, 10 mg/L) on conjugative transfer frequency reached the peak, which was approximately 6.2 times that of the control. The addition of nanoplastics significantly increased the cell membrane permeability. Gene expression analysis indicated that the addition of nanoplastics could significantly increase the expression levels of pore protein genes and conjugative transfer-related genes, ultimately increasing the transfer frequency of ARGs. This work provides important insights into evaluation of the environmental and health risks of ARGs caused by microplastics.