Effect of salt concentration on adhesion and toxicity of positively charged polystyrene nanoplastics toward bacterium Escherichia coli compared with yeast Saccharomyces cerevisiae

•Positively charged polystyrene nanoparticles (pPS-NPs) were used for nanoplastics.•Toxicity of pPS-NPs with 115-nm diameter toward bacterium and yeast was studied.•Cells were exposed to pPS-NPs in NaCl aqueous solutions (5–600 mM) at 25 °C for 0.5 h.•Bacterium Escherichia coli showed the NaCl-concentration-dependent cellular size.•E. coli was tolerant to the exposure of pPS-NPs due to its environmental adaptability.