Assessing biofilm formation and resistance of vibrio parahaemolyticus on UV-aged microplastics in aquatic environments

•Ultraviolet (UV) treatment alters physicochmical properties of microplastics (MPs).•Photodegradation of MPs boosts biofilm formation by vibrio parahaemolyticus.•Biofilm forming V. parahaemolyticus on MPs is virulent and resistant.•UV-aged MPs can increase vector potential for pathogens and threaten human health. UV degradation of marine microplastics (MPs) could increase their vector potential for pathogenic bacteria and threaten human health. However, little is known about how the degree of UV aging affects interactions between MPs and pathogens and how various types of MPs differ in their impact on seafood safety. This study investigated five types of UV-aged MPs and their impact on Vibrio parahaemolyticus, a seafood pathogen. MPs exposed to UV for 60 days showed similar physicochemical changes such as surface cracking and hydrophobicity reduction. Regardless of the type, longer UV exposure of MPs resulted in more biofilm formation on the surface under the same conditions. V. parahaemolyticus types that formed biofilms on the MP surface showed 1.4- to 5.0-fold upregulation of virulence-related genes compared to those that did not form biofilms, independently of UV exposure. However, longer UV exposure increased resistance of V. parahaemolyticus on MPs to chlorine, heat, and human gastrointestinal environment. This study implies that the more UV degradation occurs on MPs, the more microbial biofilm formation is induced, which can significantly increase virulence and environmental resistance of bacteria regardless of the type of MP. [Display omitted]