Lysis of Escherichia coli by ethylenediaminetetraacetate and phospholipases as measured by beta-galactosidase activity.

A permeaseless mutant of Escherichia coli, which produces beta-galactosidase constitutively, was treated briefly with ethylenediaminetetraacetate and then with the phospholipases of Bacillus cereus. Cell lysis occurred, as indicated by an increase in beta-galactosidase activity and a decrease in absorbancy of the cell suspension. The susceptibility of the cells to attack by ethylenediaminetetraacetate and the phospholipases was markedly affected by the age of the cells when harvested. The results suggest that permeability changes may be associated with the activity of a phospholipase that specifically degrades phosphatidyl ethanolamine. A sonic-treatment method for determining the total beta-galactosidase content of E. coli cells, which is independent of their age when harvested, is described.