FIG. 7.

Xylose uptake into Z. palmae/pMFY31-Pgap-xylA/xylB-Pgap-tal/tktA. The acclimated strain was cultured statically under the conditions described in the legend to Fig. 6. Washed cells precultured in xylose (A) or glucose (B) were suspended to give a concentration of 8.2 mg (dry weight) of cells/ml in 2 ml of 2× T medium without a carbon source. Uptake was then initiated by adding to the cell suspension 2 ml of 80 g/liter xylose containing 1.5 μCi [U-¹⁴C]xylose (a) or 2 ml of a mixture of 80 g/liter glucose and 80 g/liter xylose containing 1.5 μCi [U-¹⁴C]xylose (b). Samples (100 μl) were removed at 2-min intervals and passed through membrane filters, after which the filters were washed with 3 ml of cold saline and transferred to 10 ml of scintillation cocktail for radioassay. The diamonds indicate the xylose uptake, which is expressed as nanomoles of xylose per milligram (dry weight) of cells. The asterisks indicate the rate of xylose uptake (nmol/min · mg of cells).