Resistance ofEscherichia colito penicillins: II. An improved mapping of theampAgene

Abstract
The first mutation step towards ampicillin resistance inEscherichia colioccurs in theampAgene, and gives resistance to a D, L-ampicillin concentration of 10 μg/ml. Using interrupted conjugation and transduction experimentsampAwas found to be located at 82 min on the time scale of Taylor & Thoman (1964). A number of adjacent markers were studied and the probable gene order of theampAregion was found to beargH-metA-uvrA-ampA-purA-fdp-pyrB. Two independent alleles ofampAwere cotransduced withfdp+andpurA+. The phenotypic expression ofampAin apurAstrain has been investigated.

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