Diversity, community composition, and antibacterial activity of endophytic fungi isolated from two Gynostemma species

Endophytic fungi are recognized as important sources of bioactive natural products, yet the extent to which host plant identity and chemistry shape their community assembly and functional potential remains insufficiently understood. To address this, we comparatively investigated the diversity, community composition, and antibacterial activity of endophytic fungi isolated from two co-cultivated medicinal plants with distinct saponin and flavonoid profiles-Gynostemma pentaphyllum and Gynostemma longipes. A total of 179 fungal isolates were obtained from five tissue types and identified using internal transcribed spacer sequencing, representing 50 taxa. Diversity analysis revealed that G. pentaphyllum harbored higher species richness and isolation rates than G. longipes. Antibacterial activity of fungal extracts tested separately against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa was highly strain-dependent, with S. aureus showing the highest susceptibility. Notably, Fusarium sp. GYP-36 exhibited strong broad-spectrum activity, producing inhibition zones up to 25.5 mm against E. coli when tested with 10 μL of 1 mg mL^-1 extract, and displaying a minimum inhibitory concentration of 64 μg mL^-1 against both E. coli and S. aureus. Multivariate analyses indicated that fungal taxonomic identity was significantly associated with antibacterial activity, whereas host species and tissue origin showed statistically non-significant effects on the antibacterial activity of fungal isolates. Collectively, these findings demonstrate that functional bioactivity is predominantly governed by fungal taxonomy, while host-associated chemical traits play a secondary but significant role in shaping community assembly. Furthermore, this study highlights Gynostemma-associated endophytes as promising reservoirs for the discovery of novel antimicrobial agents, particularly through the untapped potential of taxa such as Fusarium sp. GYP-36.