Cell Division Inhibition in Salmonella typhimurium Histidine-Constitutive Strains: an ftsI -Like Defect in the Presence of Wild-Type Penicillin-Binding Protein 3 Levels

Histidine-constitutive (His c ) strains of Salmonella typhimurium undergo cell division inhibition in the presence of high concentrations of a metabolizable carbon source. Filaments formed by His c strains show constrictions and contain evenly spaced nucleoids, suggesting a defect in septum formation. Inhibitors of penicillin-binding protein 3 (PBP3) induce a filamentation pattern identical to that of His c strains. However, the His c septation defect is caused neither by reduced PBP3 synthesis nor by reduced PBP3 activity. Gross modifications of peptidoglycan composition are also ruled out. d -Cycloserine, an inhibitor of the soluble pathway producing peptidoglycan precursors, causes phenotypic suppression of filamentation, suggesting that the septation defect of His c strains may be caused by scarcity of PBP3 substrate.