Characterization of endophytic bacterial communities in Abelmoschus manihot under Cd stress and isolation of...

Abelmoschus manihot is a promising cadmium (Cd) hyperaccumulator for phytoremediation, but its endophytic bacterial community diversity and the bioremediation potential of its culturable endophytes remain underexplored. In this study, we employed high-throughput sequencing technology to comprehensively analyze the diversity, structure, and composition of endophytic bacteria in A. manihot under different levels of Cd stress. Our results showed that the root endosphere community was more strongly affected by Cd stress than the aboveground endosphere. Cd exposure markedly reduced bacterial diversity and altered the composition of the dominant genera in the root endosphere across different Cd concentrations. Network analysis revealed that Cd stress increased microbial connectivity in root communities while reducing network complexity in aboveground communities, indicating tissue-specific microbial adaptation. In the microbial networks, keystone taxa, primarily from the phyla Proteobacteria and Firmicutes, played essential roles in microbial interactions. Functional profiling through PICRUSt2 prediction revealed significant differences in the metabolic pathways of endophytic bacteria between plant compartments. Interestingly, pathways associated with transcription factors, quorum sensing, and glyoxylate and dicarboxylate metabolism were upregulated in both the root and leaf microbiomes under Cd stress. Furthermore, a core microbiome of 33 amplicon sequence variants (ASVs), dominated by Proteobacteria and Firmicutes, was consistently present across both root and aboveground tissues. 41 Cd-resistant endophytic strains were further isolated, among which the Bacillus strain BL-61 demonstrated strong potential for promoting plant growth and Cd accumulation. These findings underscore the critical roles of endophytic bacteria in hyperaccumulator adaptation to heavy metal stress and provide a foundation for developing microbe-assisted phytoremediation strategies.