Assembly Of Microbial Community And Influencing Factors Of Pathogenic Related Microorganisms In Tap Water And The Yellow River In Lanzhou City

Objective:The Yellow River is an important source of tap water and agricultural irrigation water in Lanzhou,and its water quality safety is closely related to public health and human health.Microorganisms are the basic component of aquatic ecosystem,and exploring their seasonal dynamic changes is helpful for us to understand the ecosystem process driven by microorganisms.Currently,we know little about the seasonal changes of microbial community in the Yellow River water and tap water in Lanzhou city.Therefore,the changes of the composition,diversity,assembly,interaction of microbial community and the pathogenic related microorganisms in the Yellow River water and tap water in Lanzhou city in different seasons were studied in this experiment.Methods:In our study,water samples were taken from five sampling points along the Yellow River in Lanzhou and five tap water sampling points in Lanzhou in October 2019（autumn）,December 2019（winter）,May 2020（spring）and August2020（summer）.By 16S r RNA gene sequencing and the water quality detection,we examined the seasonal dynamics of microbial community in tap water and Yellow River water and the influencing factors of pathogenic related microorganisms.Results:（1）Compared with rare taxa,abundant ones in tap water and Yellow River water had wider niche breadth and more extensive distribution.In tap water,Rhizobiales＿UG1,Sphingomonadales＿UG1,Comamonadaceae＿UG2,Delftia,Pirellulaceae,Gemmataceae and Rhizobiales＿UG2 dominated the abundant community composition;Sphingomonadales＿UG1,Rhizobiales＿UG2,Rhizobiales＿UG1,Comamonadaceae＿UG2,ACK-M1,Sphingomonadales＿UG2 and Alphaproteobacteria dominated the rare community composition.In the Yellow River water,the abundant community was mainly composed of ACK-M1,Flavobacterium,Comamonadaceae＿UG2,Hydrogenophaga,Pelagibacteraceae,Aeromonadaceae,Rhodoferax,Oxalobacteraceae,Delftia,Sediminibacterium;the rare community was mainly composed of ACK-M1,Comamonadaceae＿UG2,Flavobacterium,Comamonadaceae＿UG1,Hydrogenophaga,Actinomycetales＿UG2 and Betaproteobacteria.（2）Compared with microbial richness and community dissimilarity in tap water,the microbial richness in the Yellow River water was higher,but their community dissimilarity was lower.In tap water and Yellow River water,rare taxa showed higher richness and community dissimilarity than abundant ones.There were no significant seasonal variations in the microbial richness of abundant and rare taxa in tap water and the Yellow River water.In tap water,the community dissimilarity of abundant taxa in winter was significantly higher than that in summer and autumn,while the community dissimilarity of rare taxa had no seasonal difference.In the Yellow River water,the community dissimilarity of abundant taxa had no seasonal difference,and the community dissimilarity of rare taxa in spring and summer was significantly higher than that in winter.（3）Deterministic and stochastic processes dominated the microbial community assembly in tap water and Yellow River water respectively.The community assembly of rare taxa of tap water in autumn and rare taxa of Yellow River water in spring and winter was shaped by stochastic processes,and the community assembly of abundant and rare taxa in other seasons was governed by deterministic processes.The deterministic process had a greater effect on abundant taxa than rare ones.The conductivity（CON）,total dissolved solids（TDS）,water temperature（TW）and nitrate nitrogen（NO₃^--N）mediated the balance between deterministic and stochastic processes.（4）The microbial network of the Yellow River water had higher network-level topological parameter values than the tap water microbial network.Within the microbial networks in tap water and the Yellow River,the values of node-level and network-level topological characteristics of abundant taxa were higher than those of rare ones,and more than 70%of key species belonged to rare taxa.（5）The average relative abundance of pathogenic related microorganisms in the Yellow River water,including Comamonas,Bacteroides,Aeromonas,Acinetobacter and Flavobacterium was higher than that in tap water.The types of pathogenic related microorganisms in rare taxa were higher than those in abundant taxa.The change of water temperature（TW）,conductivity（CON）and total dissolved solids（TDS）in aquatic ecosystem can change the abundance of some Pathogenic related microorganisms.Conclusions:（1）The dominant taxa of microorganisms in the Yellow River water and tap water were different,which may be beneficial to the improvement and upgrading of water quality in their habitats.The dominant genera of abundant and rare taxa in the same water body overlapped,which may be due to the complementary functions of abundant and rare microorganisms under environmental selection.（2）Generally speaking,the abundant and rare community richness in tap water and the Yellow River water had seasonal stability,while community dissimilarity of abundant taxa in tap water and rare taxa in Yellow River water fluctuated with the seasons.（3）Deterministic and stochastic processes dominated the microbial community assembly of the tap water and the Yellow River water respectively.In tap water and Yellow River water,the deterministic process dominated the abundant and rare community assembly in most seasons.Deterministic process had a stronger effect on abundant taxa than rare ones.The change of the water temperature can shift the balance between deterministic and stochastic processes.（4）In microbial networks,abundant taxa usually occupied the central position,which had a great influence on other co-occurrence relationships in the network,while rare taxa as keystones played an irreplaceable role in maintaining the structure and stability of the network.（5）The kinds of pathogenic related microorganisms in rare taxa were higher than in abundant ones,thus rare taxa had potential risks.Reducing conductivity（CON）and total dissolved solids（TDS）can reduce the abundance of pathogenic related microorganisms.