Fig. 2. Transcription levels of leuO regulated by various concentrations of LeuO in the presence or absence of the H-NS.

Transcription levels of leuO as measured by β-galactosidase activities from ΔleuO(pBBR12-leuO-ara) (solid bars) or ΔleuOΔhns(pBBR12-leuO-ara) (open bars) harboring pMZtc-leuO. Culture conditions are described in Materials and Methods. To induce the expression of LeuO, the culture was split into four aliquots after reaching an A₆₀₀ of 0.4, and then various concentration of L-arabinose were added (0, 0.001, 0.01, 0.1%). Error bars denote standard deviations of three independent experiments (**p < 0.005; *p < 0.05 in Student’s t test).