Properties of ribosomes from erythromycin resistant mutants of Escherichia coli.

Summary We have studied the in vitro properties of ribosomes from several mutants resistant to erythromycin. Mutations in three different genes may confer resistance to erythromycin. Two of them are structural genes for proteins L4 and L22 of the large subunit. The third mutation (in eryC gene) seems to affect mainly the small subunit. The mechanism of action of the antibiotic may involve both subunits.     

Cytoplasmic inheritance of erythromycin resistant mutations in Paramecium aurelia

Summary Erythromycin inhibits the growth of wild type Paramecia and eventually kills the cells. 24 erythromycin resistant mutants (22 U.V. induced, 2 spontaneous) have been isolated. They fall into att least three phenotypic classes on the basis of their level of resistance and of thermosensitivity.Genetic analysis of three mutants shows that the resistance character is cytoplasmically inherited, as evidenced by its clonal inheritance, its transfer through cytoplasmic bridges and its non-segregation at meiosis.The results suggest that these mutants may be mitochondrial mutants analogous to those described in yeast.     

Penicillin-resistant Variants of Pneumococci

All of the 74 strains of pneumococci isolated from human infections from 1963 to 1964 proved to be uniformly and highly susceptible to penicillin. Of these strains, 15 were identified by capsule-swelling reactions and were submitted to serial transfer in the presence of increasing concentrations of penicillin. Highly penicillin-resistant mutants were selected from 14 of the 15 strains, whereas one strain was moderately resistant. Of these mutants, 11 could still react with specific antiserum, and all of the mutants could be identified by fermentation reactions and optochin inhibition. The in vitro development of penicillin resistance in these mutants did not result in a change in cell-wall composition sufficient to diminish bile solubility. The possibility of encountering rising penicillin resistance among pneumococci, as well as the possibility that such mutants may react atypically, should be kept in mind.     

Turbidimetric and potentiometric studies of ribosomal subunits from an erythromycin resistant mutant of Escherichia coli.

Turbidimetric and potentiometric techniques were applied to the analysis of an EryR mutant. Results show that in the mutant, the 30S subunits are drastically altered, as indicated by a higher Mg2+ requirement for subunit association and by an important difference in the titratable groups. Replacement of parental 50S by mutant 50S subunits does not decrease the association capacity with 30S parental subunits, but a structural difference is detected in the mutant 50S with potentiometric measurements. The mutation results in decreased ribosomal in vitro activities at 22 degrees C including lowered polyphenylalanine synthesis, drastic altered initiation step and the loss of erythromycin binding to the ribosomes. The results extend previous observation of a gene eryC part in the maturation of both subunits.