A Novel Depsipeptide Produced by Paenibacillus alvei 32 Isolated from a Cystic fibrosis Patient
The important viscosity of the respiratory tract mucus of Cystic fibrosis (CF) patients impairs the mucociliary transport system and allows the growth of numerous micro-organisms. Among them, Pseudomonas aeruginosa and Staphylococcus aureus are known to be responsible for pulmonary infections. We imagined that CF microflora could also harbour micro-organisms naturally equipped to compete with these pathogens. A method was developed to recover these antibiotic-producing strains within 20 CF sputum. Using this approach, we have isolated an unusual Gram-positive bacterium identified as Paenibacillus alvei by Api galleries and 16S rRNA gene sequence analysis. This strain has inhibited the growth of P.aeruginosa, S. aureus and Klebsiella pneumoniae, in co-cultures. A liquid mineral medium named MODT50 was designed and optimised for the production and the recovery of the antimicrobial compounds. The supernatant has inhibited the growth of all Gram-positive strains tested, even Methicillin-resistant S.aureus. One antimicrobial compound with a peptide structure (mainly active against S.aureus, Micrococcus luteus, and Pseudomonas stutzeri) has been purified and characterised by liquid chromatography-mass spectrometry. The new active molecule (m/z 786.6) named depsipeptide l possesses a 15-guanidino-3-hydroxypentadecanoic acid side chain (m/z 298) linked on a cyclic part of four amino acids residues (Ser, two Leu/Ile, Arg). This work reports for the first time the production of such a molecule by a P.alvei strain in a mineral medium. The CF lung microflora might represent a valuable source for the discovery of new antimicrobial-producing strains.
KeywordsPaenibacillus alvei Antimicrobial-peptide Cystic fibrosis Depsipeptide Fusaricidin
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