Dataset associated with "Colonization of Microplastics by Different Strains of Pseudomonas syringae Increases Ice-Nucleation Activity"

Microplastics (MPs) are increasingly detected throughout the atmosphere, raising questions about their persistence and uncertain effects on atmospheric processes, such as cloud formation. Recent studies suggest that MPs may act as ice-nucleating particles (INPs), facilitating the freezing of water at higher temperatures. Biological colonization may enhance this activity; for instance, the bacterium Pseudomonas syringae—a model organism for biological ice nucleation—is known to colonize and form biofilms on MPs. In this study, we examined the ice nucleation activity (INA) of MPs with and without colonization by P. syringae. Different strains of P. syringae, varying in their INA, were cultured on pristine and aged polystyrene (PS) and polyethylene (PE) MPs, 100 µm in diameter. All MPs studied (0.5µm to 100µm PS and 100µm PE) exhibited INA, with median freezing temperatures ranging from -21.0 °C to -23.8 °C. After aging via hydrothermal or photooxidation exposure, most MPs showed a slight but non-significant increase in the median freezing temperature. PE MPs froze at higher temperatures than PS MPs and the size of MPs did not appear to impact mean freezing temperatures. Biofilm colonization of MPs by P. syringae significantly increased median freezing temperatures by approximately 6.5 °C (p