Uncoupling expression of genes coding for the synthesis of proteins involved in transport and utilization of fructose in Escherichia coli K-12]

A novel mutation fruS localised in the fru operon has been obtained. The mutation uncouples expression of genes determining fructose specific uptake and utilization. In the fruS bacteria fruA and fruF genes (coding for enzyme II and FPr, respectively) become constitutive, while the fruK gene (responsible for fructose-1-phosphate kinase synthesis) remains inducible. In contrast to the already known mutations making the whole fru operon constitutive, the fruS mutation: 1) does not lead to xylitol sensitivity; 2) does not depress growth on lactate, pyruvate and alanine; 3) does not decrease PEP-synthase activity.