Comparative Microbiome Analysis of Rhodiola fastigiata Rhizosphere Versus Bulk Soil in Xizang with Targeted Isolation of Rhizosphere-Derived Functional Strains.

Rhodiola fastigiata, a critically endangered medicinal plant of the Qinghai-Xizang Plateau, faces severe threats from habitat degradation. This study aimed to support its microbial-assisted conservation by characterizing the rhizosphere microbiome and isolating functional plant growth-promoting (PGP) bacteria. Using high-throughput sequencing of the 16S rRNA gene and ITS region, we found the rhizosphere community to be distinct and enriched in key taxa (e.g., Sphingomonas, Mortierella). Metabolic predictions suggested upregulated stress-adaptive pathways. Crucially, from 126 isolates, we obtained four Bacillus strains that concurrently produce protease, amylase, and cellulase and solubilize phosphate-quantifying a multifunctional PGP profile critical for nutrient-poor soils. These culturable, spore-forming strains provide direct resources for developing synthetic inoculants. Our work bridges microbial ecology with applied biotechnology, delivering both a foundational microbial map and candidate strains to enable the cultivation and conservation of this endangered species in extreme environments.