Contributions of Xy1R, CcpA and HPr to catabolite repression of the xyl operon inBacillus subtilis

The xyl operon of Bacillus subtilis is regulated at the level of transcription by xylose induction via the Xyl repressor and by catabolite repression. We have investigated the influence of ccpA, ptsH, ptsG and xylR mutations on catabolite repression of xylA expression. The results indicate that full glucose repression of the xyl operon requires CcpA, Hpr and XylR. In contrast, fructose repression depends on CcpA and Hpr, but not on XylR. The ptsH1 mutation relieves catabolite repression only partially, suggesting the possibility that other presently unknown signals are sensed by CcpA.