Analysis of xylose operon regulation by Mud (Apr, lac) fusion: trans effect of plasmid coded xylose operon

Abstract

The regulation of the Escherichia coli xylose operon was investigated by Mud (Apr, lac) fusion. β-Galactosidase activity from the xyl::Mud (Apr, lac) fusion was induced by xylose but not by arabinose and repressed by glucose. The chromosomal fusion was used to analyze the trans effect of plasmid borne xyl genes. The xylA gene repressed the expression of the xyl::Mud (Apr, lac) but xylose isomerase activity was not required for this repression. The results suggest that the regulation of the xylose operon may not be exclusively by a separate regulatory element but that the xylA gene may control the expression of the operon.