Bacterial Community Patterns Across the Whole-Plant Continuum of Ormosia microphylla in Diverse Habitats

Ormosia microphylla is a national first-class protected wild plant in China that faces conservation challenges, including weak natural regeneration and limited environmental adaptability. Plant-associated bacterial communities are important components of host-associated microecosystems, but bacterial community patterns across the whole-plant continuum of O. microphylla remain poorly understood. To provide a descriptive micro-ecological baseline, we characterized bacterial communities across the rhizosphere–root–stem–leaf continuum of O. microphylla in three geographic habitats in Southwest China: karst mountainous area, a plateau-to-plain transitional slope zone, and a hilly area. High-throughput amplicon sequencing was used to analyze bacterial diversity and composition, and co-occurrence network analysis was used to describe statistical associations among bacterial taxa. Three main patterns were observed. First, bacterial alpha diversity generally declined from the rhizosphere to internal tissues (rhizosphere > root > stem > leaf). Second, bacterial composition varied by plant compartment and habitat. Dominant rhizosphere taxa differed among habitats, whereas internal tissues were generally dominated by Proteobacteria. Delftia showed relatively high abundance in several endophytic compartments, suggesting that this genus may be considered a candidate endophytic taxon for future validation. Third, co-occurrence network analysis showed habitat- and compartment-associated differences in network size, complexity, and positive/negative co-occurrence patterns. Overall, these results describe compartment- and habitat-associated bacterial community patterns in O. microphylla and provide a micro-ecological baseline for future culture-dependent and functional studies.