Differentiation and Connection of the Bacterial Community Associated with <i>Silene nigrescens</i> Along the Soil-to-Plant Continuum in the Sub-Nival Belt of the Qiangyong Glacier

Plant microbiomes provide significant fitness advantages to their plant hosts, especially in the sub-nival belt. Studies to date have primarily focused on belowground communities in this region. Here we utilized high-throughput DNA sequencing to quantify bacterial communities in the rhizosphere soil as well as in the root and leaf endosphere compartments of Silene nigrescens to uncover the differentiation and interconnections of these bacterial communities along the soil-to-plant continuum. Our findings revealed that the bacterial communities exhibit notable variation across different plant compartment niches: the rhizosphere soil, root endosphere, and leaf endosphere. There was a progressive decline in diversity, network complexity, network modularity, and niche breadth from the rhizosphere soil to the root endosphere, and further to the leaf endosphere. Conversely, both the host plant selection effect and the stability of these communities showed an increasing trend. Total nitrogen and total potassium emerged as crucial factors accounting for the observed differences in diversity and composition, respectively. Moreover, source-tracking analysis indicated a migration of bacterial communities between the rhizosphere soil, root endosphere, and leaf endosphere. The genera Pseudomonas, Mycobacterium, Conexibacter, Arthrobacter, Sphingomonas, Aureimonas, Devosia, Pseudarthrobacter, and Pseudonocardia constituted the core of the bacterial microbiome. These taxa are shared across all three compartment niches and function as key connector species. Notably, Pseudomonas stands out as the predominant taxon among these bacteria, with nitrogen being the most significant factor influencing its relative abundance. These findings provide a novel, integrative perspective on the plant microbiome within sub-nival ecosystems.