Microbial communities of desert river: Distinct roles of abundant and rare bacteria in the Tarim River ecosystem

Desert inland rivers play crucial role in water resource supply and ecosystem maintenance. The composition and structure of microbial especially bacterial communities have important effects on water environment quality and ecological function. In this study, the composition, assembly mechanisms and co-occurrence network of bacterial communities were studied in Tarim River, the largest inland desert river in China. The research found significant differences in α-diversity and β-diversity between abundant and rare taxa across free-living and particle-associated bacteria. Pseudomonadota dominated bacterial communities, and the abundant taxa and rare taxa of both free-living and particle-associated showed a high variation of percentages. Verrucomicrobiota enriched in the abundant taxa of particle-associated bacteria. TOC, TN and NO₃-N had significant correlation with the composition of rare, total and abundant taxa of both free-living and particle-associated bacteria, while TP also had significant correlation with the composition of rare taxa of free-living bacteria. Total taxa in both free-living and particle-associated bacteria were more fitted by neutral model and influenced by stochastic processes, while the rare and abundant taxa were less influenced by stochastic processes. Furthermore, the co-occurrence network analysis revealed that rare taxa could serve as critical connectors and module hubs in free-living bacteria, compared to particle-associated bacteria. Overall, our study highlights the distinctive roles of abundant taxa and rare taxa in bacterial community assembly and ecosystem function in desert river ecosystems. Understanding these roles is essential for developing conservation strategies aimed at preserving microbial diversity and sustaining ecosystem services in vulnerable habitats.