Carbohydrate Accumulation and Metabolism in Escherichia coli: Characteristics of the Reversions of ctr Mutations1

AUTOR(ES)

Wang, Richard J.

RESUMO

The reversion behavior of pleiotropic carbohydrate mutants, previously designated as ctr, was studied. The mutants revert to complete restoration of the wild-type phenotype, as well as to a spectrum of partial wild-type phenotypes. Lac+ reversions were found in the lac region (11 min) and some Mal+ reversions occurred at malB (79 min), at a distance from the site of the ctr mutations (46 to 47 min). About one-third of Lac+ and Mal+ revertants were constitutive for uptake of their respective substrates, and one-third modified for inducibility. The remaining third were not distinguishable from wild type. Induction of a ctr mutation in a lac constitutive strain, either operator or repressor mutant, did not affect lactose metabolism. A polar-like ctr mutant, deficient in both enzyme I and heat-stable protein of the phosphoenolpyruvate-dependent phosphotransferase strain was also described. Partial revertants of ctr were still found to lack enzyme I.

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