SUMMARY: A cell division mutant of K12 , the temperature sensitive strain, was pulse-labelled with [H]diaminopimelic acid (DAP) during growth in minimal salts medium both at the permissive (28°C) and restrictive (42°C) temperature. In contrast to other known cell division mutants, filaments obtained during growth at 42°C show no sign of persisting or newly initiated constrictions. The location of the incorporated DAP in dividing cells and in filaments was analysed with an improved autoradiographic method in which preparations of well-spread sacculi are covered with a dry emulsion. From the populations of sacculi complete distributions were obtained, which compared well with those of the intact cells. The grain-density distributions of cells dividing at 28°C showed that the rate of surface synthesis was strongly increased at the site of constriction at the expense of the activity in the lateral wall, suggesting a redistribution of surface synthesis activity. In individual filaments elongating at 42°C no indication for the existence of narrow or broad growth zones was found, suggesting a dispersed mode of lateral wall synthesis. These observations are in accordance with theoretical predictions on the rate of surface synthesis during the constriction period in cells which elongate at a constant diameter.


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