| Method |
The amount of diaminopimelic acid (Dap) in the cell wall of Escherichia coli was measured in two ways. A radiochemical method first described by us in 1985 (F. B. Wientjes, E. Pas, P. E. M. Taschner, and C. L. Woldringh, J. Bacteriol. 164:331-337, 1985) is based on the steady-state incorporation of [3H]Dap during several generations. Knowing the cell concentration and the specific activity of the [3H]Dap, one can calculate the number of Dap molecules per sacculus. The second method measures the Dap content chemically in sacculi isolated from a known number of cells. With both methods, a value of 3.5 x 10(6) Dap molecules per sacculus was obtained. |