Diversity and Functional Analysis of Epiphytic and Endophytic Bacteria in Three Different Parts of Brasenia Schreberi.

Brasenia schreberi J.F. Gmel (B. schreberi) is a traditional medicinal and edible plant in China, with its mucilage exhibiting antibacterial, anti-inflammatory, and antioxidant properties. This study aimed to investigate the community structure and functional roles of epiphytic and endophytic microorganisms in mature leaves, young leaves, and petioles of B. schreberi, as well as their influence on mucilage biosynthesis. A total of 560 epiphytic and 118 endophytic bacterial ASVs were obtained from B. schreberi samples. Alpha diversity was consistently higher in the mature leaves and petioles of B. schreberi compared to its young leaves. Specifically, values for OTU counts, ACE, Chao1, Simpson, and Shannon indices were all elevated in the more developed tissues. Proteobacteria and Bacteroidota dominated the epiphytic bacterial communities across all tissues, while Proteobacteria and Firmicutes were dominant in the endophytic bacteria. The KEGG functional classification of epiphytic bacteria in mature and young leaves of B. schreberi showed significant differences in metabolic pathways, including amino acid metabolism, metabolism of terpenoids and polyketides, and energy metabolism. Our results elucidate the composition and diversity of bacterial communities on three parts of B. schreberi and preliminarily demonstrate the critical role of epiphytic bacteria in the biosynthesis of its mucilage.