Rhizospheric soil microbial community structure and metabolic characteristics of wild Cymbidium mastersii at...

Cymbidium mastersii, a perennial orchid of high ornamental value, faces severe survival challenges due to extremely low natural seed germination rates (<15%), habitat degradation, and illegal harvesting. It is listed as a Category II Nationally Protected Plant Species in China.

We examined the rhizosphere microbial communities and metabolomes of C. mastersii across elevation gradients. We investigated the rhizospheric soil microbial community composition and metabolic characteristics of C. mastersii across different elevations.

The dominant bacterial phylum was Pseudomonadota, with relative abundances of 38.22% (CmL, low elevation), 36.91% (CmM, mid-elevation), and 62.54% (CmH, high elevation). While the dominant bacterial genera varied significantly with elevation, taxonomic richness exhibited a consistent decline with increasing altitude (p < 0.05, linear regression), indicating altitudinal filtering of microbial diversity. LC-MS/MS metabolomic profiling identified 1,516 metabolites, predominantly enriched in lipid and lipid-like molecules, carbohydrates and derivatives, and aromatic compounds. Functional contribution analysis revealed Bradyrhizobium as the most influential taxon (10% variance explained), displaying a nonlinear elevational response. Correlation analysis of differential metabolites confirmed significant species-metabolite correlations (P < 0.05, R > 0.7). Our findings underscore the critical role of trophic interactions in shaping rhizosphere community assembly in alpine plants, thereby contributing to the broader understanding of microbial biogeography along elevational gradients.

This study not only confirms that the altitudinal gradient serves as a key environmental filter shaping the rhizosphere microecology of C. mastersii, but more importantly, by integrating metagenomic and metabolomic approaches, we systematically reveal for the first time that altitude differentially selects for microbial taxa with specific functions, ultimately driving the restructuring of the rhizosphere metabolic environment. Moving beyond mere community description, our work aims to elucidate the underlying pathways responsible for these shifts and their potential functional implications for host plant adaptation.