FIG 4.

Effect of nalidixic acid concentration on survival and rate of protein synthesis. Exponentially growing cultures of wild-type cells (strain 3505) were treated with nalidixic acid (Nal) at the indicated concentrations for 1 h. Aliquots were diluted, plated, and incubated for determination of CFU and calculation of percent survival (empty squares). Rate of protein synthesis (filled circles) from a parallel culture was determined by pulse labeling with ³⁵S-labeled methionine (1 μCi ³⁵S-methionine per 200 μl culture) for 5 min followed by determination of acid-insoluble radioactivity. Inhibition of protein synthesis is expressed relative to the rate of a parallel untreated culture. Dashed line indicates inhibition of protein synthesis by 20 μg/ml chloramphenicol. Data are means from at least three independent experiments; error bars represent standard errors of the mean.