The utilization of fructose by Escherichia coli. Properties of a mutant defective in fructose 1-phosphate kinase activity.

1. The isolation and properties of a mutant of Escherichia coli devoid of fructose 1-phosphate kinase activity are described. 2. This mutant grew in media containing any one of a variety of substances, including hexoses, hexose 6-phosphates, sugar acids and glucogenic substrates, at rates not significantly different from those at which the parent organism grew on these substrates. However, only the parent grew on fructose or fructose 1-phosphate. 3. Fructose and fructose 1-phosphate inhibit the growth of the mutant, but not of its parent, on other carbon sources. 4. Even though not previously exposed to fructose, the mutant took up [(14)C]fructose rapidly but to only a small extent: [(14)C]fructose 1-phosphate was identified as the predominant labelled product. In contrast, the equally rapid but more extensive uptake of [(14)C]fructose by the parent organism required prior growth in the presence of fructose.