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The bacterium, Bacillus amyloliquefaciens Pc3, was previously isolated from Antarctic seawater and has been found to show antagonistic activity against the fungus, Rhizoctonia solani ACCC 36316, which causes a severe disease known as Sclerotinia sclerotiorum in rapeseed plants. Bacillus lipopeptides had been widely used as biocontrol agents for plant diseases. In this study, we isolated 11 lipopeptide compounds from B. amyloliquefaciens Pc3 culture broth via reversed-phase high-performance liquid chromatography (RP-HPLC) and used matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) to identify these as iturin A (C14, C15, C16, C17), fengycin B (C14, C15, C16, C17), and surfactin (C14, C15, C16). We further found that the addition of exogenous alkanoic acids, including myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, octadecanoic acid, and nonadecanoic acid, to the bacterial growth media could promote lipopeptide production and enhance the antifungal activities of crude lipopeptide extracts from B. amyloliquefaciens Pc3. In addition, the transcriptional levels of three lipopeptide synthesis genes, ituD, fenA, and srfA-A, and two fatty acid metabolism-related genes, FabI, which encodes enoyl-ACP reductase, and FadB, which encodes enoyl-CoA hydratase, were found to be upregulated in cells grown with exogenous alkanoic acids. Among the six alkanoic acids tested, those with odd carbon chain lengths had a greater effect on lipopeptide production, antifungal activity, and target gene upregulation than those with even carbon chain lengths. These results provide a practical approach for the efficient production of lipopeptides in Bacillus amyloliquefaciens Pc3.

A novel LCI like antibacterial protein produced by Bacillus sp. MD-5, which was isolated from the Arctic Ocean sediment sample during the sixth Chinese National Arctic Expedition in 2014, was purified and characterized. After saturation of Bacillus sp. MD-5 culture supernatant with ammonium sulfate and separation with ion-exchange chromatography and high performance liquid chromatography (HPLC), an antibacterial protein (MD) was purified. The MD protein was determined to be a novel LCI like antibacterial protein with molecular weight of about 7.0 kDa using liquid chromatograph-mass spectrometer (LC-MS) identification and the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). It displayed antibacterial activity against Staphylococcus aureus at minimum inhibitory concentration (MIC) of 7.33 μg/mL. MD protein possessed high thermostability and wide range of pH tolerance, and had a certain extent of protease, surfactant and metal ion resistance. MD protein was suggested to inhibit the growth of S. aureus through inhibiting peptidoglycan biosynthesis in the view of TEM detection. These results suggested that MD may represent a novel antibacterial protein with potential application in controlling S. aureus in food industry.