Autolysis of unwashed exponential-phase Escherichia coli cells was efficiently promoted by first submitting them to a quick downshock with distilled water before an upshock with 0.5 M sodium acetate, pH 6.5. The association of these two osmotic shocks had a remarkable synergistic effect and led to significant decreases in turbidity and viability. Different factors influencing the rate of cell lysis were examined. A close correlation was established between autolysis and the degradation of peptidoglycan. Both phenomena were induced by the same shock treatment, followed similar kinetics, and were efficiently blocked by addition of divalent cations. Cell lysis was also inducible by a shock treatment with 10(-3) M ethylenediaminetetraacetic acid or ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid and blocked by the addition of divalent cations.