A mutation affecting gluconate catabolism in Escherichia coli: the locus for the main high affinity transport.

The bioH-malA region of the E. coli chromosome (min 75.5) includes the gntT gene which encodes a high affinity transport for gluconate. Other gnt loci have not been characterized in this region; nevertheless, because lesions in it affect severely the utilization of gluconate, it has been suggested as being more complex. This region was investigated with respect to gluconate catabolism through the characterization of suitable E. coli strains lysogenized with a specialized transducing phage carrying the bioH-malA region of the bacterial chromosome (lambda cI857st68h80d2bioH-malA). It was found that the region transduced by this phage while includes the gntT gene lacks other gnt loci that might code additional activities for transport of gluconate or its phosphorylation. Moreover, the pleiotropic lesion gntM2, previously mapped into this region and suggested as altering gntT or a presumptive regulator gene that might be involved in this catabolism, resulted recessive in lysogens (partial diploids) containing the defective prophage. The results obtained supported the idea that gntM2 is an allele of gntT; consequently those results suggested the precise position of this gene on the cromosomic map and the central role that its product might have in the initial incorporation of gluconate in E. coli.