Biochemical consequences of mutational damage to common components of the Erwinia phosphoenolpyruvate-dependent phosphotransferase system (the HPr protein and enzyme I) were studied. The transport of glucose, mannose, fructose, and mannitol inErwinia was shown to require a preliminary induction of proteins of the phosphotransferase system. A drastic decrease in the rate of the transport of these carbohydrates was observed in ptsI and ptsH mutants. A disturbance in the common components suppresses the synthesis of inducible enzymes (β-galactosidase, complexes of pectolate lyases and cellulases) and renders it resistant to catabolite repression by glucose, but mutants were shown to retain intracellular cAMP content. Erwinia mutants devoid of common components of the system lack phytopathogenic features. The appearance of an intact ptsI allele in the cell completely repaired pleiotropic disturbances in these mutants.