Structural Changes in Escherichia coli Infected with a φX174 Type Bacteriophage

The coliphage α 3, which is morphologically similar to φX174, was shown by acridine orange staining to contain single-stranded DNA. Its infective process was studied by the electron microscopy of thin sections of Escherichia coli infected at high multiplicity. The latent period was found to be about 13 min. but no obvious structural changes were visible in host cells until 10 min. after infection, when the plasma membrane began to retract from the poles. At 14 min. intracellular phage was detected and bulges appeared on the cells at their midpoint. At 21 min. many cells were in the form of spheroplasts and others were beginning to lyse. Spheroplasts formed by phage infection lysed differently from those produced by penicillin.