Microbiome and metabolomics analysis of different bryophytes under cadmium stress

Understanding the differences in physiological responses of various bryophytes to cadmium (Cd) stress can assist in the monitoring and remediation of heavy metal pollution. In this study, we investigated Cd concentration, physiological indicators, microbiome, and metabolites in the bryophytes Mnium laevinerve, Timmia bavarica, and Brachythecium salebrosum under simulated Cd stresses (0 (CK), 1 (T1), 10 (T2), and 100 (T3) mg·L− 1). Cadmium accumulation and physiological responses were dose-dependent and species-specific, with M. laevinerve exhibiting the highest accumulation and most significant physiological alterations. Furthermore, antioxidant enzyme activities and osmolyte levels generally increased and then decreased with rising Cd concentration, while photosynthetic pigments declined progressively. Moreover, metabolomic and microbiome analyses revealed species-specific shifts: differential metabolites (i.e., L-Asparagine, Stachyose, and Traumatic acid) and phyllosphere bacterial communities (notably Proteobacteria, Bacteroidota, and Actinobacteriota) showed significant alterations under Cd stress. The physiological, metabolomic, and microbiome integrated analysis highlighted that Cd resistance in M. laevinerve and T. bavarica was highly correlated with changes in specific phyllosphere bacterial phyla (Acidobacteriota and Actinobacteriota) and the metabolite L-Asparagine, suggesting a potential coordinated response. These findings provide a foundation for future research into biomonitoring and bioremediation of heavy metal pollution.