FIG. 3.

Promoter activity in LB broth as measured by chloramphenicol resistance. L. monocytogenes DP-L2986, DP-L2989, and DP-L2812 carrying the hly, actA, and control reverse-orientation actA promoter fusions, respectively, were cultured in buffered LB broth in the absence (light bars) or presence (dark bars) of 10 μg of chloramphenicol per ml. After 5 h, bacterial growth was assessed by measuring the OD₆₀₀. The data represent the mean ± standard deviation for three individual experiments. The addition of increasing doses of chloramphenicol at the onset of L. monocytogenes 10403S culturing in LB broth and measurement of the OD₆₀₀ at various time points demonstrated an MIC of 5 μg/ml (data not shown).