Composition and Predictive Functional Analysis of Rhizosphere Bacterial Communities in Riparian Buffer Strips in the Danjiangkou Reservoir, China

Abstract

Microbial communities play crucial roles in the global biogeochemical nitrogen cycle. To our knowledge, the compositions and functions of rhizosphere communities in riparian buffer strips have not been reported. In this study, rhizosphere soil samples were collected from herbs (Vetiveria zizanioides and Phragmites australis), trees (Pyrus betulifolia), and shrubs (Discocleidion rufescens) in the Danjiangkou Reservoir in June 2017. High-throughput sequencing was performed to analyze the community structure and diversity of bacteria. Phylogenetic analysis based on 16S rDNA sequences shows that the bacterial communities can be divided into 31 major phylogenetic groups. The dominant phylogenetic groups include Proteobacteria, Bacteroidetes, Actinobacteria, Gemmatimonadetes, and Acidobacteria. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) was used to determine the metabolic and functional abilities of the observed bacterial communities. Our results reveal a wide genetic diversity of organisms involved in various essential processes such as biosynthesis of other secondary metabolites, transcription, Glycan biosynthesis and metabolism, cell growth and death, and carbohydrate metabolism. Based on the 16S rRNA gene copy number of the detected phylotype, the bacterial rhizospheres of plants in riparian buffer strips can be ranked as follows:Discocleidion rufescens > Phragmites australis > Vetiveria zizanioides > Pyrus betulifolia. We analyzed the differences of different plants from the perspective of bacterial community composition and function and provide a foundation for vegetation construction and water environmental protection in riparian buffer strips of the Danjiangkou Reservoir.