Multi-step resistance to Chloramphenicol in RC-stringentEscherichia coliK12—its effect on the induction of RNA synthesis by antibiotics under amino acid starvation

Abstract

A multi-step Chloramphenicol (CM)-resistant derivative of an RC-stringent strain ofEscherichia coliauxotrophic for threonine and leucine was resistant also to Aureomycin (AM) and Puromycin (PM). All three antibiotics released the repression of RNA synthesis due to amino acid starvation in the CM-sensitive parent strain, their relative activities being about 1:10:100 for AM: CM: PM. High doses of AM and CM failed to induce RNA synthesis. The CM-resistant strain required greater concentrations of each antibiotic than the sensitive strain to induce the same level of RNA synthesis, and appeared to be about one hundred times, ten times and five times more resistant to CM, AM and PM, respectively, than the sensitive strain.