ELECTRON-MICROSCOPIC STUDIES ON INTRACELLULAR PHAGE DEVELOPMENT - HISTORY AND PERSPECTIVES

This review is centered on the applications of thin sections to the st udy of intracellular precursors of bacteriophage heads. Results obtain ed with other preparation methods are included in so far as they are e ssential for the comprehension of the biological problems. This type o f work was pioneered with phage T4, which contributed much to today's understanding of morphogenesis and form determination. The T4 story is rich in successes, but also in many fallacies. Due to its large size, T4 is obviously prone to preparation artefacts such as emptying, flat tening and others. Many of these artefacts were first encountered in T 4. Artefacts are mostly found in lysates, however, experience shows th at they are not completely absent from thin sections. This can be expl ained by the fact that permeability changes induced by fixatives occur . The information gained from T4 was profitably used for the study of other phages. They are included in this review as far as electron micr oscopic studies played a major role in the elucidation of their morpho genetic pathways. Research on phage assembly pathways and form determi nation is:a beautiful illustration for the power of the integrated app roach which combines electron microscopy with biochemistry, genetics a nd biophysics. As a consequence, we did not restrict ourselves to the review of electron microscopic work but tried to integrate pertinent d ata which contribute to the understanding of the molecular mechanisms acting in determining the form of supramolecular structures.