Bacillus subtilis SSE4 produces subtulene A, a new lipopeptide antibiotic possessing an unusual C15 unsaturated β‐amino acid

Abstract

<jats:p>Subtulene A, a new cyclic lipopeptide, was isolated from the culture broth of <jats:italic>Bacillus subtilis</jats:italic> SSE4. This antibiotic compound contained the seven common α‐amino acids, <jats:sc>l</jats:sc>‐Asn‐1, <jats:sc>d</jats:sc>‐Tyr‐2, <jats:sc>d</jats:sc>‐Asn‐3, <jats:sc>l</jats:sc>‐Gln‐4, <jats:sc>l</jats:sc>‐Pro‐5, <jats:sc>d</jats:sc>‐Asn‐6, <jats:sc>l</jats:sc>‐Ser‐7 and the unique β‐amino acid‐8 present in the iturin family. 1D and 2D NMR, as well as MS analyses, identified the β‐amino acid as 3‐amino‐13‐methyltetradec‐8‐enoic acid, an Iso C15 long chain β‐amino acid. <jats:italic>B. subtilis</jats:italic> SSE4 was also found to produce iturin A. <jats:italic>B. subtilis</jats:italic> SSE4 culture filtrate exhibited both antifungal and antibacterial activities.