Toxicity Of Polystyrene Microplastics To Marine Microorganisms

Microplastics,as emerging pollutants,have adverse effect to marine environment.Microorganisms can perform as both producer and decomposer in marine environment,and they play important roles in the recycling and utilization of carbon,nitrogen,sulfur and other elements.At present,there are relatively few studies on the effects of microplastics to microorganisms,and the interaction between microplastics and microorganisms are still unclear.Therefore,the toxicity of polystyrene microplastics(PS)was investigated using two different bacteria,Escherichia coli(Gram-negative)and Bacillus cereus(Gram-positive),as the tested organisms.The results showed that PS could inhibit the growth of E.coli cells,and PS with smaller size(i.e.,0.1 ?m)pose greater effect to E.coli.The presence of PS promoted the growth of B.cereus.The thicker cell wall of the Gram-positive bacteria might be the reason of the different toxicity of the two bacteria.In addition,the interaction between the two bacteria and PS particles was different.It was observed that E.coli cells adhered to the surface of 5 ?m PS by flagella,which indicated that microplastic could promote the ability of E.coli biofilms formation.The production of ROS,MDA,LDH and GSH in the two bacteria showed similar trends,which could not be the main reason for the difference in toxicity result.Meanwile,PS could not damage the bacteria's DNA.Polycyclic aromatic hydrocarbons(PAHs)are common persistent organic pollutants in coastal areas of China.Pyrene is one of the most common PAH pollutants.Microplastic pollution can affect the environmental behavior of PAHs,and the interaction between them may pose potential adverse effect on the community structure of microorganisms in marine sediments,thereby affecting the ecological function of sediments.Through 14-day micro-cosmic experiment,the interaction between PS and pyrene on the microbial community structure in marine sediments was investigated.Both richness and diversity of microbial community in sediments were decreased after the sediments were exposed to different treatment groups(i.e.,pyrene,PS,and pyrene adsorbed on PS,respectively).This was revealed by difference in the structure of community at genus level.The results of community analysis indicated that the adsorption of pyrene by PS may reduce the degradation ability of microbial community,and the slow release of pollutants caused by the adsorption of PS also weakened the impact of pollutants on the ecological function of the community itself.Three strains of Bacillus sp.,which could degrade pyrene,were isolated from sediment samples.The addition of PS of smaller size(i.e,0.1 ?m)could promote the degradation effect of the three bacteria,while large particle size of PS did not have significant impact on their degradation ability.