PERMEABILITY OF THE ESCHERICHIA-COLI OUTER-MEMBRANE TO ETHIDIUM IONS AND PERIPLASMIC ALKALINE-PHOSPHATASE DURING ENHANCED SYNTHESIS OF THE ALKALINE-PHOSPHATASE

The outer membrane of various Escherichia coli strains overproducing p eriplasmic alkaline phosphatase was found to be permeable not only to the enzyme, but also to ethidium ions, which normally do not penetrate into gram-negative bacteria. In the absence of the outer membrane lip oprotein, the permeability of the membrane to these compounds and its sensitivity to membranotropic agents increase, indicating a role of th e lipoprotein in the barrier properties of the outer membrane. A negat ive correlation was revealed between the contents of lipoprotein and l ipopolysaccharide in the outer membrane and between their content and alkaline phosphatase secretion into the medium. It is suggested that t he increased permeability of the Escherichia coli outer membrane durin g overproduction of the secreted protein is due to impaired biogenesis of membrane components.