Biochemical characterization of φX174‐protein‐E‐mediated lysis of Escherichia coli

Energetic and permeability properties of Escherichia coli cells were determined prior to and during lysis caused by expression of the cloned gene E of bacteriophage φX174. Before onset of cell lysis the transmembrane gradients for K + , Na + or Mg 2+ /ions, the level of ATP and the membrane potential, were unaffected. All these parameters changed simultaneously at the time of lysis onset, as monitored by measurements of culture turbidity as well as by determining the various specifications over a period of 1 min. During cell lysis chromosomal DNA was fragmented whereas plasmid DNA was liberated in its intact supercoiled form. Cytoplasmic constituents were released almost entirely, as indicated by the activity of β‐galactosidase in the supernatant fraction of protein‐Elysed cells. Periplasmic enzymes were only found in limited amounts in the cell supernatant and most remained associated with the cell ghosts. Such ghosts exhibited no gross cell damage or morphological alterations when compared with intact E. coli by light microscopy. All parameters investigated indicated that protein‐E‐mediated lysis of E. coli is caused by the formation of a transmembrane tunnel structure through the envelope complex of the bacterium.