Divalent Cations and EDTA

The colicin A lysis protein, Cal, is synthesized at the same time as colicin A by Escherichiu coli harbouring plasmid pColA after induction by mitomycin C. Its function in the induced bacteria involves the release of colicin A, quasi-lysis, the death of the producing cells and the activation of the outer membrane phospholipase A. We have found that these various functions are affected differently by treatment of the induced cells with Triton X-100, divalent cations or EDTA. Triton X-100 and EDTA caused increased quasi-lysis and a higher level of mortality of the producing cells, but while Triton X-100 enhanced the release of colicin A, EDTA reduced it. Divalent cations protected the cells against both killing and quasi-lysis without greatly affecting colicin release. The effects of these agents were similar for both wild-type and phospholipase A mutants and depended only on the presence of a functional cal gene.