Influence of physicochemical surface properties on the adhesion of bacteria onto four types of plastics

Bacterial adhesion onto plastics is common in natural environments and can also affect the fate and transport of plastics in aquatic environments. To date, the adhesion of bacteria to different types of plastics has not yet been systematically studied. In this study, we systematically investigated both the short-term and long-term adhesion of three types of bacteria (both model and wild-type bacteria) onto four types of plastics, including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC), which are the most frequently encountered plastics in aquatic environments. The results showed that the amount of bacteria that adhered to PE and PVC surfaces was much greater than that attached to PP and PET, regardless of the bacteria type in both short-term and long-term adhesion experiments, following the trend as: PE ≈ PVC > PP ≈ PET. The similar adhesion behavior of bacteria onto plastics that was found in both short-term and long-term experiments showed that the intrinsic surface properties of the different types of plastics influenced the bacterial adhesion. Therefore, physicochemical factors, including surface charge, hydrophobicity/hydrophilicity, roughness, and hardness of the plastics, were further characterized. Compared with the minimal differences in surface charge, hydrophobicity/hydrophilicity, and roughness among the different types of plastics, the surface hardness of the plastics was found to be the key factor dominating the adhesion of bacteria onto plastic surfaces. The results give insights to assess the fate and transport of different types of plastics in real environments.