Mangrove ecosystems play critical roles in global climate change and carbon sequestration . Understanding the mangrove-microbe interaction and their mechanisms i s a central question in ecology. To address this question, we investigated key microorganisms and their potential mechanisms for mangrove-microbe interactions by integrating metabolomics of root exudates, transcriptomics of root tissues, and metagenome sequencing analysis of sediment micro bial communities in a pot experiment with a native mangrove species (Kandelia obovata) and an introduced mangrove species (Sonneratia apetala).
We found that mangrove root exudate profiles were correlated with rhizosphere microbiomes , showing significant (p < 0.05) influences on the taxonomic or functional profiles between those two mangrove species. Specifically, the concentration of flavonoid catechin exhibited the most correlations with the abundance of microbial groups and functional genes, and flavonoid biosynthesis pathways were mediated by the transcription factor MYB118 of mangrove roots . Also, s ulfur-oxidizing Rhodobacteraceae was strongly correlated with catechin, which could be utilized as a carbon source , and recovered Rhodobacteraceae metagenome-assembled genomes (MAGs) showed genetic potentials for urea degradation, nitrite reduction, phosphate mineralization and regulation, and acyl-homoserine-lactone synthesis, which could promote mangrove growth and increase the plant-derived carbon by detoxifying sulfide, regulating phosphorus turnover, and mediating quorum sensing. In addition, the higher microbial necromass carbon in the carbon-rich mangrove sediment was related with sulfur oxidation, and chemoautotrophic sulfur-oxidizing Burkholderiales could be key microbial groups for transform ing plant-derived carbon to microbially-derived carbon. These findings reveal a key role of sulfur oxidiz ing microbial communities in mediating plant-microbe interactions, providing novel insights into plant-microb e interaction mechanisms in mangrove ecosystems.