Production and partial purification of a peptide antibiotic from Staphylococcus epidermidis

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Abstract
When grown on solid or in liquid brain heart infusion at 37.degree. C, S. epidermidis NCIB 11536 produced antibiotic activity against a wide range of gram-positive bacteria. Production was influenced by aeration, pH, glucose concentration and specific growth rate. Inhibitory activity could be concentrated by (NH4)2SO4 precipitation (30-55% saturation). On Sephadex G50 using 0.05 mol/l sodium phosphate buffer, pH 6.0, 2 peaks of antibiotic activity were detected. The 1st peak eluted with the void volume (Kd = 0) and the 2nd peak was retained by the gel (Kd = 0.73-0.77). These 2 substances did not represent the monomeric and polymeric forms of a staphylococcal bacteriocin. The low MW inhibitor, which was responsible for > 95% of the recovered activity on Sephadex G50, could be partially purified by a combination of gel filtration on Biogel P2 and ion-exchange chromatography on Sephadex C-25. Yields were increased by combining these 2 steps into a single procedure (duocolumn). The semi-purified inhibitor was desalted using Sep-pak C18 cartridges. Biological activity was resistant to enzymic denaturation except by high concentrations of trypsin (50 units/.mu.g, 3 h, 25.degree. C). This peptide antibiotic is different from any previously described stapylococcal inhibitors.