Pseudomonas Stutzeri may alter the environmental fate of polystyrene nanoplastics by trapping them with increasing extracellular polymers

Pseudomonas Stutzeri (P. stutzeri) is a denitrifying bacterium that is essential in biological nitrogen removal. To study the interaction between P. stutzeri and polystyrene nanoplastics (PS-NPs), the effects of PS-NPs posed on P. stutzeri were evaluated in terms of bacterial growth, physiology, denitrification function and extracellular polymers (EPS) secretion. Results of confocal laser scanning microscopy (LCSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and flow cytometry confirmed that PS-NPs were trapped by P. stutzeri. Exposure to PS-NPs inhibited bacterial growth and expression of denitrification-related genes, but unaffected the denitrifying enzyme activities. The enhanced secretion of EPS caused PS-NPs and bacterial aggregation. And the enzyme activity of SOD in P. stutzeri was increased while that of CAT was decreased. The results of flow cytometry showed that high concentrations of PS-NPs increased the complexity of P. stutzeri cells. These results reveal that P. stutzeri may be affected after trapping PS-NPs and alter their environmental fate as well. SYNOPSIS: This study contributes to the understanding of the possible effect of P. stutzeri on the distribution of PS-NPs and illustrates the potential impact of PS-NPs on P. stutzeri.