Dose-Dependent Responses of Escherichia coli and Acinetobacter sp. to Micron-Sized Polystyrene Microplastics

Microplastics are ubiquitous environmental contaminants that can cause significant ecological damage because of their resistance to biodegradation. We evaluated the toxic effects of 1,040 nm polystyrene (PS) microplastics in two representative bacteria, Escherichia coli and Acinetobacter sp. In particular, we examined the effects of these PS microplastics on bacterial growth and viability, parameters related to oxidative stress (reactive oxygen species [ROS], lactate dehydrogenase [LDH], and malondialdehyde [MDA]), membrane integrity, and biofilm formation. An increasing concentration of PS microplastics decreased cell growth and viability in both species. These PS microplastics also decreased cell membrane integrity and increased biofilm formation in both species. Although both species exhibited adverse overall effects from PS microplastics, they had significant differences in specific indicators of oxidative stress. Correlation analysis demonstrated different correlations among measured experimental parameters (cell viability, ROS, LDH, MDA, and biofilm formation) in these two species. These results suggest that 1,040 nm PS microplastics decreased cell growth and viability by different mechanisms in E. coli and Acinetobacter sp.