A rare peptide scaffold in kineomicins, the glycopeptide antibiotics produced by Actinokineospora auranticolor DSM 44650.

Discovery of novel antibiotics is crucial to counteract bacterial resistance spread. Aiming to expand the available arsenal of last-resort glycopeptide antibiotics (GPAs), we mined the actinobacterial genomes of Pseudonocardiales. We thus identified a biosynthetic gene cluster (BGC) encoding for a GPA with a novel peptide scaffold, not fitting into the existing classification of GPA types. By cultivating the producer strain, Actinokineospora auranticolor DSM 44650, an antibiotic complex-named kineomicins (Kmc)-was identified and characterized by microbiological assays, LC-MS, and MS/MS analyses. A comprehensive model for Kmc biosynthesis was then proposed by a thorough investigation of kineomicin BGC (knm). The structure of the main complex congener (KmcB), resolved by NMR spectroscopy, proved to be unique. Finally, the remarkably high antibiotic production rate, up to >1 g L(-1) Kmc in benchtop bioreactor, indicated A. auranticolor as a natural GPA overproducer, holding promise as a potential host for heterologous expression of GPA BGCs.