Deacylation of Calcium‐Dependent Antibiotics from Streptomyces violaceoruber in Co‐culture with Streptomyces sp. MG7‐G1

When Streptomyces violaceoruber grows together with Streptomyces sp. MG7‐G1, it reacts with strongly induced droplet production on its aerial mycelium. Initially the metabolite profile of droplets from S. violaceoruber in co‐culture with Streptomyces sp. MG7‐G1 was compared to samples from S. violaceoruber in single‐culture by using high‐performance liquid chromatography‐mass spectrometry (HPLC‐MS). Then, the exudate from agar plates of co‐cultures and single cultures (after freezing and thawing) was also analysed. Several compounds were only observed when S. violaceoruber was grown in co‐culture. Based on their high‐resolution ESI mass spectra and their comparable retention times to the calcium‐dependent antibiotics (CDAs) produced by S. violaceoruber, the new compounds were suspected to be deacylated calcium‐dependent antibiotics (daCDAs), lacking the 2,3‐epoxyhexanoyl residue of CDAs. This was verified by detailed analysis of the MS/MS spectra of the daCDAs in comparison to the CDAs. The major CDA compounds present in calcium ion‐supplemented agar medium of co‐cultures were daCDAs, thus suggesting that Streptomyces sp. MG7‐G1 expresses a deacylase that degrades CDAs.