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Mutations Affecting the Dissimilation of Mannitol by Escherichia coli K-12¹

^a Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115

ABSTRACT

Mutants of Escherichia coli K-12 defective in the mannitol-specific enzyme II complex of the phosphoenolpyruvate phosphotransferase system (PTS) or lacking mannitol-1-phosphate dehydrogenase have been isolated. These mutants fail only to grow on mannitol. Growth of the dehydrogenase-negative mutant on casein hydrolysate can be abruptly inhibited by exposure to mannitol. A mutant with constitutive expression of both of these enzymes has also been isolated. All three mutations are clustered in a region represented at min 71 of the Taylor map. In a mutant with less than 5% of the activity of enzyme I of the PTS, both the enzyme II complex and the dehydrogenase remain inducible by mannitol. In the mutant defective in the enzyme II complex, mannitol is able to induce the dehydrogenase. Thus, mannitol, rather than its phosphorylated product, seems to be the inducer.

² Present address: Service Génétique Cellulaire, Institut Pasteur, Paris 15, France.

¹ A portion of this work was submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree at Harvard University, Cambridge, Mass., June 1971.