INFECTION OF ESCHERICHIA COLI BY T2 AND T4 BACTERIOPHAGES AS SEEN IN ELECTRON MICROSCOPE .3. MEMBRANE-ASSOCIATED INTRACELLULAR BACTERIOPHAGES

The formation of newly synthesized T2 and T4 bacteriophages in Escherichia coli has been studied with the electron microscope using the thin-sectioning technique. Intracellular viruses frequently are radially oriented with their heads near the centers of the infected bacteria and with the distal tips of their tails in close proximity to the cell membranes. Investigations of certain amber mutants have shown that when intracellular phage heads are synthesized but not attached to tails, these heads are not arranged in the characteristic radial orientation. Therefore, it seems that the phage tail is responsible for the observed orientation of newly formed T2 and T4 particles. High resolution micrographs show that intracellular phages appear to be associated with bacterial membranes by thin fibers, probably short tail fibers, extending from their baseplates. Evidence is discussed which indicates that during the process of phage assembly the interaction between the T4 gene 12 product and the phages' tail pins may occur on the membranes of infected bacteria. © 1969.