Expression of hemolysin genes in E. coli directed by viral promoters. Hemolysis of sheep blood erythrocytes by E. coli DH5α containing the vlly coding sequence without promoter (panels A and D), with the promoter from the polyhedrin gene (P PH: panels B and D) or with the immediate early promoter from CMV (P CMV: panels C and D). Panels A to C show the hemolysis in blood agar plates visible as cleared zones around the colonies. Panel D indicates the percentage of erythrocytes lysed in a liquid blood assay. The columns show the average of two measurements.