Lincomycin increases the half-life of β-lactamase mRNA

Escherichia coli K-12 strains isolates carrying plasmid pBR322 were grown in the presence of subinhibitory concentrations of lincomycin, which stimulated β-lactamase synthesis about 2.5-fold, and the effects of the drug on the synthesis and degradation of bla mRNA were studied. The bla mRNA levels determined by 1-min pulse-labeling with [³H]uridine were significantly higher in a lincomycin-containing culture than in the control culture, indicating that stimulation of β-lactamase synthesis is caused by an increase in the amount of bla mRNA. The enhancing effect of lincomycin was observed in strains harboring pBR322ΔP1 and pBR322ΔP3, which lacked the P1 or P3 promoter, respectively, as well as in the strain harboring pBR322. S1 nuclease analysis showed that the half-life of bla mRNA increased about 2.7-fold when lincomycin was present. These results indicate that the increase in β-lactamase synthesis caused by lincomycin is due to an increase in the stability of bla mRNA rather than activation of its synthesis.