Metagenomic analysis of the community structure and functional potential of Tamarix rhizosphere microbiomes along a soil salinity gradient

Yanzhi Wang¹Lijuan Zhang^1,2Wei Huang²Ning Wang²Meng Sun¹Longyuan Wu¹Wei Wang^2*Chong Shi^1*

• ¹Xinjiang Agricultural University, Ürümqi, China
• ²Xinjiang Academy of Agricultural Sciences Institute of Microbiology, Urumqi, China

To characterize the Tamarix rhizosphere microbiome across natural habitats, rhizosphere soils were collected from four sites in Xinjiang, China (S1–S4; increasing water-soluble total salinity), followed by measurements of soil physicochemical properties and shotgun metagenomic sequencing. Increasing salinity was associated with pronounced restructuring of community composition: low-to-moderate salinity samples (S1–S2) were dominated by bacteria, with Pseudomonadota, Actinobacteriota, and Bacteroidota as major phyla, whereas archaeal relative abundance increased in high and very high salinity samples (S3–S4), with Euryarchaeota becoming dominant. Functional annotation indicated that core metabolic pathways, including amino acid and energy metabolism, remained highly represented across samples, suggesting a degree of metabolic stability in the rhizosphere microbiome. Under high salinity, functions related to genetic information processing (e.g., translation and replication/repair) and ion transport were enriched, whereas lipid metabolism, cell motility, and signal transduction were reduced, indicating a functional shift from "growth expansion" toward "homeostasis maintenance." Mechanistic profiling further showed that the Na⁺/H⁺ antiporter system and V/A-type ATPases were enriched in the very high salinity group, while betaine-and ectoine-biosynthesis pathways were relatively reduced, suggesting an adaptive strategy centered on energy-dependent ion homeostasis with concurrent adjustment of osmoprotection. Collectively, these results elucidate structural and functional responses of the Tamarix rhizosphere microbiome to salinity gradients and provide a microbial basis for understanding plant–microbe interactions in arid saline–alkaline regions and for informing soil restoration efforts.