FIG. 8.

Influence of the degree of supercoiling on transcription of the esp promoter. EDL933(pUJ3) was grown in M9-glucose medium supplemented with 10 mM (open symbols) or 430 mM (solid symbols) NaCl in the presence of 0 (triangles), 5 (circles), 20 (squares), or 50 (diamonds) μg of the gyrase inhibitor novobiocin per ml, and β-galactosidase activities were determined at different time intervals. Results are expressed as relative light units (rlu) per 10⁵ bacteria and are means of three independent experiments; standard deviations were lower than 5%. The background values for EDL933 containing the promoterless plasmid were at least 10-fold lower than the basal values at the tested conditions and were subtracted from each sample. No differences in growth were observed at the novobiocin concentrations tested (not shown).