城市水体微塑料垂向分布下附着细菌群落结构和功能响应

Community Structure and Microbial Function Responses of Biofilms Colonizing on Microplastics with Vertical Distribution in Urban Water

微塑料作为环境微生物的附着载体已经引起了世界范围内的广泛关注.然而,水环境中微塑料往往呈现垂向分布特征,附着的细菌群落结构和功能是否会随之产生变化仍少见报道.因此,选取了水环境中常见的微塑料聚对苯二甲酸乙二醇酯(PET)和聚氯乙烯(PVC)为研究对象,通过野外水体垂向暴露,结合高通量测序技术,探究微塑料垂向分布下附着的细菌群落结构变化和功能表达响应.结果表明,相较于PVC微塑料,附着于PET微塑料上的细菌群落α多样性更高;随着暴露水深的增加,附着于PET和PVC两种介质的细菌群落丰富度和多样性均随之增加,且深水条件下(90 cm),附着于两种微塑料的细菌α多样性指数均明显高于其在30 cm和60 cm的值.蓝藻门(Cyanobacteria)、变形菌门(Protobacteria)、浮霉菌门(Planctomycetes)和疣微菌门(Verrucomicrobia)为PET和PVC附着细菌群落的优势物种.进一步分析发现,深水环境明显改变了附着于微塑料的细菌群落结构.相关功能预测表明,嘧啶代谢、氨基糖和核苷酸糖的代谢、淀粉和蔗糖代谢和酰胺生物合成代谢功能表达与水深深度呈正相关性;深水条件下,附着于两种微塑料的细菌功能表达明显增加,且PET上附着细菌的功能表达明显高于PVC.微塑料材质类型和水深深度均会影响附着的细菌群落结构组成和功能响应,相对而言,水深环境的影响更加显著,这可能与光照和浊度在垂向上的差异性有关.研究结果为揭示微塑料污染影响下的微生物响应和环境危害提供了基础支撑.

Microplastics have received increasing attention worldwide due to their carrier effects.In the aquatic environment,microplastics always show a vertical distribution,which thereby may change the structure and function of the attached microbial communities.However,few studies have focused on this alteration.In this study,the structural changes and functional expression responses of the attached bacterial communities to microplastics under vertical distribution were investigated in the field combined with high?throughput sequencing technology.Polyethylene terephthalate(PET)and polyvinyl chloride(PVC)were selected as the target microplastics,which were frequently detected in the aqueous environment.The results showed that theα-diversity of bacterial communities attached to PET microplastics was much higher than that of those attached to PVC microplastics.The abundance and diversity of the bacterial communities attached to PET and PVC both increased with the increase in water depth.Theα-diversity index of bacteria attached to the two typical microplastics was significantly higher in deep water(90 cm)than that in water 30 cm and 60 cm deep.The Cyanobacteria,Proteobacteria,Planctomycetes,and Verrucomicrobia were the dominant phyla in the attached bacterial communities.In addition,the deep water distinctly altered the bacteria community attached to different microplastics.The results of functional prediction showed that the functional expression of pyrimidine metabolism,amino sugar and nucleotide sugar metabolism,starch and sucrose metabolism,and aminoacyl-tRNA biosynthesis were positively correlated with water depth.In addition,the functional responses of the bacterial communities attached to microplastics were also increased,especially in deep water.Further,the bacterial functions of those attached to PET were significantly higher than that of those attached to PVC.This suggests that both the microplastic polymer and the water depth could affect the structure and function of the attached bacterial communities and that the water depth was more important,which may be related to the difference in the vertical distribution of light and turbidity.The results of this study provide a new insight into the microbial response to and environmental risk of microplastic pollution.