The transition to the Green Deal era requires the discovery of alternative sources of bioactivity and an in-depth understanding of their toxicity to target and non-target organisms. Endophytes have recently emerged as a source of bioactivity of high potential for applications in plant protection, used either per se as biological control agents or their metabolites as bioactive compounds. The olive tree endophytic isolate Bacillus sp. PTA13 produces an array of bioactive lipopeptides (LPs), which additionally exhibit reduced phytotoxicity, features that make them candidates for further research focusing on olive tree plant protection. Here, GC/EI/MS and 1H NMR metabolomics were employed to study the toxicity of a Bacillus sp. PTA13 LP extract on the olive tree pathogen Colletotrichum acutatum, which causes the devastating disease olive anthracnose. The discovery of resistant isolates of the pathogen to the applied fungicides makes the research on the development of improved sources of bioactivity of paramount importance. Analyses revealed that the applied extract affects the metabolism of the fungus by interfering with the biosynthesis of various metabolites and its energy production. LPs had a great impact on the aromatic amino acid metabolism, the energy equilibrium of the fungus and its fatty acid content. Additionally, the applied LPs affected the levels of pathogenesis-related metabolites, a finding that supports their potential for further research as plant protection agents.
Keywords: bacillomycins; fengycins; lipopeptides; mechanism of action; natural products; olive anthracnose; pesticides; surfactins.