Community structure and function predication of bacterial communities in the upper reaches of the Three Gorges of the Yangtze River

Abstract:

[Objective] This paper aims to reveal the bacterial community structure in the Three Gorges of the Yangtze River,the topological properties of co-occurrence network and its hub microorganisms,and the metabolic functions of the bacterial community.[Methods] Water samples were collected from the mainstream and four tributaries (Xiangxi River,Daning River,Zhuyi River,and Meixi River) of the Yangtze River.PacBio 16S rRNA high-throughput sequencing and bioinformatics analysis were performed to elucidate the bacterial community structure and Tax4Fun was employed to predict the metabolic functions of the community.[Results] (1) The dominant phyla in the upper reaches of the Three Gorges of the Yangtze River were Proteobacteria(66.4%),Bacteroidetes(13.2%),and Cyanobacteria(6.2%).In Proteobacteria,Gammaproteobacteria was most abundant and followed by Alphaproteobacteria.The diversity index and richness index implied the rich microbial species in the study area.(2) Co-occurrence network formed a "small world" topology,and Sphingomonadaceae,Chloroflexi,Gemmataceae,Flectobacillus,and Cryomorphaceae were the central microorganisms which played a crucial part in maintaining the community structure and diversity.(3) A total of 6 functions in level 1 and 42 functions in level 2,which mainly involved in metabolism and genetic information processing,were found in Tax4Fun function prediction,suggesting the active metabolism of the bacterial community.[Conclusion] Bacterial community in the upper reaches of the Three Gorges was of high diversity,and the hub microorganisms were mainly rare microorganisms which played an important role in maintaining the community structure.The bacterial community in the upper reaches of the Three Gorges featured abundant metabolic pathways,which was beneficial to the health of the water body.Clarifying the distribution and interaction characteristics of microbial community could lay a scientific basis for the healthy ecosystem development,water resource utilization,and water environment improvement of the Yangtze River.

Key words:upper reaches of the Three Gorges;bacterial community structure;co-occurrence network;Tax4Fun function prediction