Development of H-Sh and P1kcvir phages in Shigella flexneri F6S studied by fluorescence microscopy and electron microscopy

Abstract

The electron microscopic examination of ultrathin sections of Shigella flexneri F6S cells infected with either H-Sh or P1kcvir phages has shown that the protein vacuoles found in these infected cells by means of fluorescence microscopy have ultramicroscopic structure. In electron micrographs the vacuoles first appear as small, round, homogeneous cytoplasmic “dense bodies” which later on become larger cytoplasmic vacuoles containing a thick reticulum not made of DNA. In nearly bursting cells the vacuoles contain phage heads, tails, and mature phages. The vacuoles do not have a limiting membrane. When Kellenberger osmium tetroxide fixative is used, the vacuoles and their thick net content can be seen clearly, but intracellular phages are very rarely seen even on pictures showing numerous extracellular phages. After glutaraldehyde fixation the intracellular phage heads and tails are clearly visible. Phage tails are mainly seen in the interior of the vacuoles and phage heads at the periphery.