Antifungal Activity and Potential Mechanisms of Two Bafilomycin Analogues Isolated from Streptomyces sp. NEAU-Y11 against Colletotrichum orbiculare.

Cucumber anthracnose, caused by Colletotrichum orbiculare, severely affects the cucumber yield and quality. In this study, two active compounds, bafilomycin C1 and JBIR-100, were isolated from strain NEAU-Y11 and exhibited strong antifungal activity against C. orbiculare, with EC50 values of 0.0491 and 0.1042 μg/mL, respectively, significantly lower than those of the commercial fungicide (4.42 μg/mL). Pot experiments demonstrated effective control of cucumber anthracnose at 0.2 μg/mL for bafilomycin C1 and 0.4 μg/mL for JBIR-100, with efficacies reaching 78.5 and 67.7%, respectively. Microscopy and biochemical analyses indicated that both compounds disrupted the fungal cell wall, membrane, and redox homeostasis, leading to cell death. Transcriptome analysis further revealed the effects of bafilomycin C1's on amino acid metabolism, cell structure, redox homeostasis, and DNA double-strand break repair. These findings suggest that bafilomycin C1 and JBIR-100 are promising candidates for use as agrochemical fungicides to control C. orbiculares and may serve as a basis for developing next-generation antifungal agents.