• Open Access

Paenimacrolidin, a novel macrolide antibiotic from Paenibacillus sp. F6-B70 active against methicillin-resistant Staphylococcus aureus

Authors


E-mail haichung@zju.edu.cn; Tel. (+86) 571 88981107; Fax (+86) 571 88981107;

E-mail mblab@163.com; Tel. (+86) 571 88206627; Fax (+86) 571 88206627.

Summary

Paenibacillus sp. F6-B70 was selected from several dozens of isolates with activity against methicillin-resistant Staphylococcus aureus using a 16S rDNA-based screening method. F6-B70 contained polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) clusters in its genome revealed by PCR amplification of conserved adenylation and ketosynthase (KS) domains. Phylogenetic data suggested that the strain hosts trans-AT PKSs and their product may be a branched molecule. An antibiotic was subsequently isolated from the methanol extract of F6-B70 cells. The molecular formula of the antibiotic was deduced to be C33H50NaO6 ([M + Na]+, m/z 565.3505) by analysis of electrospray ionization mass spectral data. Elucidation of the structure by nuclear magnetic resonance and infrared spectroscopy revealed that the active compound, paenimacrolidin (PAM), was a novel 22-membered macrolide with side-chains. The new antibiotic, mainly as a bacteriostatic agent, inhibits a couple of multidrug-resistant Staphylococcus sp. strains. The antibiotic capacity of PAM was compromised by its instability, which can be overcome significantly with addition of an anti-oxidant. To our knowledge, this is the first report of the isolation of an active macrolide from paenibacilli, which may be a promising source of novel antibiotics.

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