FIG. 6.

Regulation of the expression of the cip-cel operon by the carbon source and effect of the cis-acting CRE deletion on this regulation. Strains ATCC 35319(pPSV1) and ATCC 35319(pPSV1ΔCRE) grown in cellobiose (2 g liter⁻¹)-containing minimal medium were used to inoculate various 100-ml cultures. Carbon sources were added (as indicated at the bottom) at final concentrations of 5 g liter⁻¹ (MN300 cellulose) and 4 g liter⁻¹ (cellobiose [Clb], glucose [Glu], arabinose [Ara], and xylose [Xyl]). The CAT activities determined by using cells collected in the mid-exponential growth phase reflect the expression driven by the P1 (filled bars) and P1ΔCRE (open bars) promoters. Experiments were performed twice. For CAT activities, the bars indicate the means of three experiments, and the error bars indicate the standard deviations.