Mechanism of Chloramphenicol and Tetracycline Resistance in Escherichia coli

The protein-synthesizing activity of cell-free preparations of Escherichia coli was estimated by adding radioactive amino acids according to the system of Matthei & Nirenberg (1961). Cell-free systems were prepared from antibiotic-sensitive strains of E. coli and from resistant variants, and the sensitivity of amino acid incorporation to inhibition by chloramphenicol and tetracycline determined. The same sensitivity was shown for the sensitive as for the resistant strains.