Resistance of<i>Escherichia coli</i>to penicillins: II. An improved mapping of the<i>ampA</i>gene

Abstract

The first mutation step towards ampicillin resistance in Escherichia coli occurs in the ampA gene, and gives resistance to a D, L-ampicillin concentration of 10 μg/ml. Using interrupted conjugation and transduction experiments ampA was found to be located at 82 min on the time scale of Taylor &amp; Thoman (1964). A number of adjacent markers were studied and the probable gene order of the ampA region was found to be argH-metA-uvrA-ampA-purA-fdp-pyrB . Two independent alleles of ampA were cotransduced with fdp + and purA + . The phenotypic expression of ampA in a purA strain has been investigated.