Metal ion content of Escherichia coli versus cell age

The potassium, calcium, magnesium, and zinc ion content of cells in exponential and synchronously growing cultures of Escherichia coli B/r was determined with an X-ray fluorescence spectrometer and an atomic absorption spectrophotometer. Cellular potassium, calcium, and magnesium content increased smoothly during the cell cycle, but cellular zinc showed a steplike increase about 10 to 15 min after cell division in a culture having a doubling time of 47 min. The possible role of cellular zinc in the control of cell division is discussed.