THE ACTIVITY OF MICROCIN E492 FROM KLEBSIELLA-PNEUMONIAE IS REGULATEDBY A MICROCIN ANTAGONIST

Microcin E492 is a polypeptide antibiotic that is produced and excrete d by Klebsiella pneumoniae. Different growth conditions of the produce r strain affect microcin activity. The production of a microcin antago nist is responsible for the changes in microcin activity. The microcin antagonist is induced when cells are iron-deprived, resulting in a lo w microcin activity. The microcin antagonist was purified using a proc edure developed for the isolation of a catechol-type siderophore, and its activity was titrated using purified microcin. The inhibitory effe ct of the microcin antagonist is not observed when this compound is fo rming a complex with iron. The same inhibitory effect on microcin acti vity was obtained using purified enterochelin from Escherichia coli. T he microcin antagonist was identified as enterochelin through thin-lay er chromatography.