Table 3.

Expression of β-lactamase from the norApromoter in transcriptional fusions in E. coliDH5αa

PlasmidMICb(μg/ml)Ratiocβ-Lactamase activityd (u/mg)Ratio
pWN2018211.2 ± 0.41
pBF8-30321617.5 ± 1.714
pBF7-7321617.2 ± 1.514
  • a Cells containing the specified plasmids were grown in LB broth and sonicated prior to determination of β-lactamase activity, which was assayed as specified in Table 2, footnotea.

  • b MIC of ampicillin, determined on Mueller-Hinton agar.

  • c MICs and β-lactamase activities were normalized to that of the strain carrying the vector alone.

  • d β-Lactamase activities are expressed in units per milligram of proteins and are the means ± standard deviations of at least three determinations.