Phenotypes represented by a mutational change in a 50s ribosomal protein component, 50-8, in Escherichia coli

Summary An erythromycin resistant (ery ^r) mutant of Escherichia coli Q13, QE107, was characterized by (1) the cross resistance of the cells to several macrolide antibiotics such as erythromycin, tylosin, spiramycin, oleandomycin and leucomycin, (2) the reduced affinity of its ribosomes to erythromycin and probably to the other macrolides mentioned above, (3) a low peptidyl transferase activity of its ribosomes and (4) an altered 50-8 protein of the 50s ribosomal subunits. These characters were always transferred together with the ery marker in the transduction experiments.Preliminary data of part of this work has been published (Tanaka, Teraoka, Tamaki, Watanabe, Osawa, Otaka and Takata, 1971).