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 unde rgo cell division inhibition in the presence of high concentrations of a metabolizable carbon source. Filaments formed by His(c) strains sho w con strictions and contain evenly spaced nucleoids, suggesting a def ect in septum formation. Inhibitors of penicillin-binding protein 3 (P BP3) induce a filamentation pattern identical to that of His(c) strain s. However, the His(c) septation defect is caused neither by reduced P BP3 synthesis nor by reduced PBP3 activity. Gross modifications of pep tidoglycan composition are also ruled out. D-Cycloserine, an inhibitor of the soluble pathway producing peptidoglycan precursors, causes phe notypic suppression of filamentation, suggesting that the septation de fect of His(c) strains may be caused by scarcity of PBP3 substrate.