Contact-independent antagonistic activity of endophytic Diaporthe biconispora PBS24-3 against Penicillium spp.: dual culture, culture filtrate, metabolomics, and molecular network analysis.
TL;DR
Findings demonstrate that D. biconispora PBS24-3 mediates antifungal antagonism through a contact-independent, secretome-driven mechanism.
Abstract
The treatment of invasive fungal infections remains challenging due to the limited availability of antifungal agents and the rapid emergence of drug resistance. Endophytic fungi, shaped by chemically mediated interactions within plant-associated niches, represent an important source of antifungal activity. Here, we investigated the contact-independent antagonistic potential of the endophytic fungus Diaporthe biconispora PBS24-3 against two opportunistic Penicillium species. In dual-culture assays, D. biconispora PBS24-3 consistently formed stable inhibition zones without direct hyphal contact, and antifungal activity was fully reproduced by cell-free culture filtrates, indicating a secretome-mediated mode of antagonism rather than physical competition. The inhibitory effect was target-dependent, with stronger mycelial growth inhibition observed for P. citrinum (65.97 ± 2.22%) than for P. sumatrense (45.10 ± 4.45%); notably, the inhibition against P. sumatrense was comparable to that of itraconazole under the same experimental conditions. Microscopic examination revealed hyphal distortion and reduced conidiation in treated Penicillium cultures. In parallel, untargeted UHPLC-Orbitrap-HRMS/MS metabolomic profiling combined with molecular network analysis revealed a chemically complex, multi-component secretome dominated by secondary-metabolite families consistent with antifungal activity. These findings demonstrate that D. biconispora PBS24-3 mediates antifungal antagonism through a contact-independent, secretome-driven mechanism.