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

Cucumber anthracnose, caused by <i>Colletotrichum orbiculare</i>, 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 <i>C. orbiculare</i>, 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 <i>C. orbiculares</i> and may serve as a basis for developing next-generation antifungal agents.