FIG 2.

Effect of the regulator, regulator-induced expression time, and inducer concentrations on the activity of the promoter P_xylA. (A) Organization of the putative A514 xylose catabolism locus, as well as reporter constructs used to detect activity of P_xylA. P, promoter; gfp, green fluorescent protein gene. (B) Activities of P_xylA and P_van under various inducing conditions. For bars 1 to 5, either 0 mM or 0.2 mM (final concentration) xylose was added when strains were at the mid-exponential phase. After 6 h of induction, green fluorescence intensity was measured to determine the promoter activity. Bars 6 and 7 represent the P_van activity in A_Pvan at the mid-exponential phase and the stationary phase, respectively. Bars 8 and 9 represent the XylR-P_xylA activity in A_R-PxylA at the stationary phase, which was exposed to 0 mM or 2 mM xylose for 12 h, respectively. pTT, pPROBE-TT; Con, concentration. (C) Time point-dependent induction of XylR-P_xylA activity. Response of XylR-P_xylA to different growth phases at which 0.2 mM xylose (final concentration) was added. Fluorescence intensity was measured every 3 h until A_R-PxylA entered the stationary phase. (D) Xylose concentration-dependent induction of XylR-P_xylA activity. A_R-PxylA at the mid-exponential phase was exposed to different concentrations of xylose for 6 h. For panels B, C, and D, all of the strains were cultivated in M9 medium supplemented with 15 mM vanillic acid. Fluorescence intensity, which was detected to determine the promoter activity, is expressed in arbitrary units normalized for 10⁶ CFU.