Isolation and characterization of microcin E492 from Klebsiella pneumoniae

The production of a dialyzable peptidic antibacterial named microcin E492 by the strain of faecal origin Klebsiella pneumoniae RYC492 has previously been reported. In this paper, a procedure to extract this antibiotic from liquid cultures of the producer strain is described. This method was based in the quantitative retention of the microcin on the hydrophobic matrix Bondapak C18 and led to highly active pigment- and salt-free concentrates appropriate for further purification by high pressure liquid chromatography. The characterization of purified preparations indicated that microcin E492 was a basic and hydrophobic peptide with an apparent molecular mass of about 5,000, acid- and heat-resistant and much more active in minimal than in rich medium. These properties are discussed with regard to the likely ecological role of the microcin in the microbial ecosystem of the intestine.