FIG. 3.

Growth and penicillin-induced killing of the S. gordonii parent (A) and penicillin-induced killing of the Tol1 mutant (B) monitored by viable counts and quantification of a 427-bp fragment of 16S rRNA. In both cases, the number of copies of rRNA was proportional to the viable counts. The insets at the bottom of the graphs depict crude 23S and 16S rRNA prepared from culture aliquots removed at various times during penicillin treatment and separated by agarose gel electrophoresis. In the kill-susceptible parent (A), the bands disappeared after 24 h of drug treatment. In the kill-resistant Tol1 mutant (B), the bands remained visible. Details and experimental reproducibility are described in the legend for Fig. 1.