[Catabolyte repression of Escherichia coli K12 mutants with defects in different systems of glucose transport].

The phenomenon of glucose catabolite repression was studied in E. coli mutants inable to transport this carbohydrate. The pts 1, H mutant P34 was much less sensitive to the repressive effect of glucose on beta-galactosidase synthesis than the parent type. The 1103 mutant devoid of enzyme 1 of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) behaves in the same way as P34 mutant after addition of glucose to casamino acid mineral medium. However, in minimal medium with succinate as the sole source of carbon, cells of the 1103 mutant show enhanced sensibility to transient glucose repression. The effect of hypersensibility disappears when the lac I mutation leading to constitutive the beta-galactosidase synthesis is introduced in 1103 mutant. It is shown that the enhanced sensibility of beta-galactosidase synthesis to glucose transient repression in 1103 mutant is an effect of the aburpt decrease in its growth rate in the presence of succinate and most probably this decrease leads to "inducer exclusion" of the lac operon. It is also shown that if one introduces the P34 mutation in strain JD3 devoid of one of the enzymes II for glucose (and due to this resistant to glucose catabolite respression) then the level of resistance in double mutant does not increase in spite of considerable supression of 14C glucose accumulation. In connection with this the role is discussed of separate components of the E. coli K 12 glucose transport system in realization of the phenomenon of catabolite repression.