Genetical analysis of rifampicin resistant mutants of E. coli K 12

Summary E. coli rifampicin-resistant (rif-r) mutants were divided into two conventional groups: A, resistant to 50–100g/ml of rifampicin both on complete and minimal medium and B, sensitive to these concentrations of rifampicin on minimal, but resistant on complete medium. RNA polymerase from rif-r-A mutants is resistant to high concentrations of rifampicin in vitro while the enzyme from rif-r-B mutants but slightly if at all differs from the wild-type enzyme in its response to the drug.All rif-r-A and rif-r-B mutants are closely linked and map between argH and thi on E. coli K 12 chromosome. We failed to isolate any rifampicin-resistant mutants which would map outside this region.