CONTENTS 



I Introduction 1 



1 . Definition 1 



2. Discovery of bacteriophages 2 



3. Nature of bacteriophages 4 



4. Origin of bacteriophages 6 



5. Lysogeny 8 



6. Classification of phages 11 



II The Infective Process 13 



1. The one-step growth experiment 14 



2. Adsorption 15 



3. Penetration 17 



4. Multiphcation 18 



5. Lysis of host cell and release of phage progeny. . 20 



6. Lysis in fluid media 21 



7. Lysis on soHd media 22 



III Enumeration of Bacteriophage Particles 27 



1 . Plaque counts 27 



2. Dilution end-points 30 



3. Measurement of lysis-time 31 



4. Intracellular phage 32 



IV Size and Morphology of Bacteriophages 35 



1. Electron microscopy of bacteriophage particles. . 35 



2. Ultrafiltration 41 



3. Analytical centrifugation 42 



4. Diff'usion constants 43 



5. Electrophoresis 44 



6. Ionizing radiations 44 



7. Nonionizing radiations 46 



8. Weight of the infectious particle 46 



9. Summary 47 



V Effects of Physical and Chemical Agents (Except 



Radiations) on Bacteriophage Particles 49 



1. EflTectof pH 50 



2. Urea and methane 50 



3. Detergents 51 



IX 



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