Antifungal Mechanism of Crude Lipopeptide Extract from Bacillus velezensis TCS001 Against Colletotrichum camelliae

Colletotrichum camelliae, the primary causative agent of anthracnose, severely threatens oil-tea camellia (Camellia oleifera) cultivation. Microbial lipopeptides are efficient, eco-friendly secondary metabolites that exhibit broad-spectrum antifungal activity, promote plant growth, and elicit host systemic resistance. This study evaluated the biocontrol potential of Bacillus velezensis TCS001, a marine-derived bacterium capable of synthesizing these bioactive compounds. The crude lipopeptide extract (CLE) from strain TCS001 exhibited dose-dependent fungicidal activity against C. camelliae within a range of 1.56–200 mg/L, yielding a median effective concentration (EC50) of 53.33 mg/L. CLE treatment suppressed conidial germination and induced severe hyphal shriveling and structural deformities. Crucially, in vivo inoculation assays confirmed that CLE significantly attenuated pathogen virulence on C. oleifera leaves. Transcriptomic profiling revealed that the CLE triggered substantial transcriptional reprogramming in C. camelliae. Key pathways involved in cell wall biosynthesis, energy production, amino acid metabolism, and cell-cycle progression were significantly down-regulated, while intracellular oxidative stress was simultaneously induced. Collectively, these findings demonstrate that TCS001 lipopeptides orchestrate a multi-target molecular suppression of fungal growth and pathogenicity, establishing a robust theoretical framework for deploying B. velezensis TCS001 to manage oil-tea camellia anthracnose.