Deacylation of calcium-dependent antibiotics from Streptomyces violaceoruber in co-culture with Streptomyces sp. MG7-G1

Abstract

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 using high-performance liquid chromatography-mass spectrometry (HPLC-MS). Then, also the exudate from agar plates of co-cultures and single cultures (after freezing and thawing) was 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. violaceo-ruber 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 deacylated CDAs in comparison to the CDAs. The major CDA compounds present in calcium ion supplemented agar medium of co-cultures were daCDAs, suggesting that Streptomyces sp. MG7-G1 expresses a deacylase that degrades CDAs.