Genetic analysis of some mutations causing resistance to tetracycline inEscherichia coliK12

Abstract

Mutations in at least five different genetic loci cause some degree of resistance to Chloramphenicol, Tetracycline or both antibiotics inEscherichia coliK12. Two have been identified as chromosomal genes:cmlAnear λ prophage andcmlBnearpyrD. A third, giving mucoid antibiotic-resistant mutants, is probablycapR(Ion) nearlac. Another group of mucoid mutants gives marked increases in resistance to Tetracycline and in sensitivity to Puromycin; these mutants do not occur atcapR. Although all the mutations have rather small effects on resistance level, the patterns of resistance to the three antibiotics appear to be characteristically different for mutations at different loci.