Microbial colonization and chemically influenced selective enrichment of bacterial pathogens on polycarbonate plastic

Plastic pollution in aquatic environments poses significant concerns due to its potential to serve as a refuge for aquatic pathogens. However, the role of plastic surfaces and microbial biofilm interfaces in facilitating pathogen development remains poorly understood. In this study, a microcosm setup was employed to investigate the interactions between plastics and the microbial community and examine the differences in bacterial community composition and potential pathogen occurrences between the plastisphere-biofilm and surrounding seawater. Community composition analysis combined with SEM observations over time indicated that biofilm extracellular polymeric substance formation over 14 days had a link with the relative abundance and succession patterns of pathogen taxa. Colony clusters were observed on biofilms from day 7 and coincided with higher bacterial pathogen dominance. On day 14, pathogen abundance overall decreased with a potentially degrading biofilm. Pseudomonas and Pseudoalteromonas were the dominant potential pathogen groups observed in the microcosm. When further subjected to chemical treatment as an imposed environmental stress over time, biofilm-associated Psuedoalteromonas sharply increased in abundance after three days of exposure, but quickly diminished by 14 days in favor of genera such as Acinetobacter, Pseudomonas, and Staphylococcus. These results suggest that environmental plastisphere-biofilms can promote the early selection, enrichment, and spread of pathogenic bacteria in the aquatic environment and could be later worsened under chemical and long-term pressure. This study provided new insights into the succession of pathogens in plastisphere biofilms, contributing to the understanding of pathogen risks involved in emerging plastisphere biofilms in light of global plastic pollution.