The Cd-Tolerance of Pepper ( <i>Capsicum annuum</i> L.) Is Linked with the <i>Rhizosphere</i> Bacterial Community Composition and <i>Rhizosphere</i> Soil Metabolite Profiles

Cadmium (Cd) poses a serious threat to plant growth, so the selection and breeding of Cd-tolerant pepper cultivars are effective methods to reduce Cd hazards. This study identified <i>C. annuum</i> G03 as a Cd-tolerant cultivar, evidenced by its superior leaf physiological activity under Cd stress compared to the sensitive <i>C. annuum</i> C07. 16S rDNA sequencing revealed a more complex bacterial symbiotic network in the bulk soil, rhizosphere, and root endophyte of <i>C. annuum</i> G03, enhancing its buffering capacity against Cd stress. Furthermore, correlation analysis between rhizosphere bacteria and metabolites indicated that <i>Armatimonadota</i> and <i>Bdellovibrionota</i> were the key functional bacteria of <i>C. annuum</i> G03. They can influence the levels of key metabolites such as nerolidol, glutathionylspermine, and alpha-linolenic acid, thereby reducing antioxidant damage and Cd ion uptake in plant roots. These findings provide valuable insights into the microbial mechanisms underpinning the tolerance of pepper to Cd stress.