Characterization of culturable endophytes and microbial communities in the rhizosphere and pitcher fluid of the carnivorous plant Nepenthes khasiana.

Endophytes colonize plant tissues through roots and shoots without causing harm and can move throughout the plant via its vascular system. However, little is known about culturable endophytes, particularly bacteria, in pitcher plants, and their possible entry through pitcher fluid remains unexplored. To address this gap, we isolated endophytes from the pitcher plant Nepenthes khasiana, and performed metagenomic analysis of its rhizospheric soil and pitcher fluid, from which bacteria and fungi were also isolated, to investigate the possible origin of these endophytes. We found that culturable endophytic bacteria were predominantly associated with roots and seeds, whereas endophytic fungi were more abundant across the N. khasiana pitcher. Although most endophytes were restricted to specific tissues, some exhibited a broader distribution across nearly the entire plant. Several OTUs from the rhizospheric soil matched endophytes at the genus level, including some that were also detected in the pitcher fluid. Specifically, three bacterial genera - Enterobacter, Staphylococcus and Bacillus - and one fungal genus, Cladosporium, detected in the pitcher fluid, matched the isolated endophytes. These findings suggest that endophytes in N. khasiana most likely originate from the rhizosphere, with possible migration into the pitcher fluid.