Pyoung Il Kim

Structural characterization and temperature-dependent production of C17-fengycin B derived from Bacillus amyloliquefaciens subsp. plantarum BC32-1

Cyclic lipopeptides were produced by Bacillus amyloliquefaciens subsp. plantarum strain BC32-1 that was isolated from yellow loess soil in the Jeonnam province of South Korea. Several lipopeptides were isolated from the bacteria using organic solvent extraction and reverse-phase high-performance liquid chromatography (RP-HPLC). Purified iturin-, surfactin-, and fengycin-type lipopeptides were identified using liquid chromatographymass spectrometry (LC-MS) analysis. Among the lipopeptides, C17-fengycin B showed strong antifungal activity against the phytopathogenic fungus, Fusarium oxysporum f. sp. radicis-lycopersici, and then the fengycin was further characterized by UV, Fourier transform-infrared spectroscopy (FT-IR), and LC-MS/MS analyses. C17-fengycin B was highly produced at quantities of up to 15 µg/mL at 37°C, whereas little amount of the fengycin was produced at 25°C. Purified C17-fengycin B inhibited mycelial growth of F. oxysporum with a minimal inhibitory concentration of 50 µg/mL. This study suggests that C17-fengycin B is a major antifungal component produced by the BC32-1 strain that could be used as an environmentally friendly agent to control the phytopathogenic F. oxysporum.

Isolation and structural elucidation of pelgipeptin E, a novel pore-forming pelgipeptin analog from Paenibacillus elgii with low hemolytic activity

Pelgipeptins are cyclic lipopeptides composed of nine amino acids and a short fatty acid chain. In the present study, we report a novel pelgipeptin peptide that was isolated from Paenibacillus elgii BC34-6 and named pelgipeptin E (PGP-E). The molecular mass of PGP-E was 1072 Da as determined by liquid chromatography-mass spectrometry and the amino acid sequence was elucidated by tandem mass spectrometry. The complete molecular structure of PGP-E was characterized using 2D NMR spectroscopy. PGP-E consisted of a cyclic peptide backbone of Dab1-Val2-Dab3-Phe4-Leu5-Dab6-Val7-Leu8-Ser9 and a lipid chain (-CH2CH2CH3). PGP-E had broad antimicrobial activity against gram-negative and -positive bacteria, including methicillin-resistant Staphylococcus aureus strains. Furthermore, the mode of action of PGP-E was investigated using calcein dye leakage and membrane depolarization assays, which suggest that PGP-E acts via a membrane-active mechanism. The hemolytic activity of PGP-E was significantly lower than that of melittin, a well-known membrane-active peptide derived from bee venom. These results suggest that PGP-E is a potential candidate in the development of new peptide antibiotics.