Ultrastructure of Bacterial Viruses

Mter the discoveryof the tobacco mosaic virus by D. I. Ivanov skU in 1892 [14], the new science of virology was born and began to develop rapidly. The number of viruses now known is enormous and they can infect nearly all animal and plant organisms. Microorganisms themselves are no exception to this rule. Despite intensive study of Vlruses, their origin and nature are still a subject for speculation and hypothesis. The general concept of viruses embraces a wide group of biologically active structures occupying an intermediate position between living and nonliving matter. The dual character of viruses is determined by the fact that, while they do not possess an inde pendent system of metabolism, which is a characteristic feature of every living being, they nevertheless carry within themselves all the necessary information for autoreproduction. A striking feature of the virus is that it consists essentially of two components: a protein envelope and the nucleic acid con tained within it. In contrast to the elementary structural unit of the living or ganism, the cell, which contains two types of nucleic acid (DNA and RNA), the virus particle contains only one type of nucleic acid - either DNA or RNA. It is perhaps this which is responsible for the imperfection of the virus as a living organism.

1. Electron-Microscopic Methods of Investigation of Bacteriophages.- The Supporting Grids.- Preparation of the Mounting Film.- Methods of Preparing Suspensions of Bacteriophages.- Methods of Obtaining Concentrated Suspensions of Phages.- Purification of Biological Preparations.- Contrasting of Objects.- Methods of Fixation of Bacteria for Preparation of Ultrathin Sections.- Terminology.- 2. Classification of Phages Based on Morphological Characteristics.- 3. Filamentous Phages and Phages with Tail Analogs.- Filamentous Phages (Group I).- Phages with Tail Analogs (Group II).- 4. Short-Tailed Phages (Group III).- Subgroup I: Phages of Type T3 and T7.- Subgroup II: Phages of Type P22, sd.- 5. Phages with a Noncontracting Tail (Group IV).- Structural Variation among Phages with a Noncontracting Tail.- 6. Phages with a Tail Possessing a Contractile Sheath (Group V).- Phage T2 HO.- Phage No. 1 of Bacillus mycoides.- Phage N19 of Bacillus mycoides.- Phages of Bacillus subtilis.- Staphylococcal and Streptococcal Phages.- 7. Defective Phages and Bacteriocins.- 8. Action of Chemical and Physical Agents on Various Phages.- Action of pH.- Urea and Other Agents Breaking Hydrogen Bonds.- Detergents.- Freezing and Thawing.- The Effect of Temperature.- Action of Adenosinetriphosphatase on Phages.- 9. The Aggregative Properties of Phage Proteins.- Polysheaths.- Polyrods.- Polyheads.- 10. Phosphatase Activity of Phages and Some Properties of the Contractile Phage Protein.- Localization of Phosphatase Activity in Structural Elements of Phage T2.- Physicochemical Properties of the Contractile Protein of Phage T2.- 11. Organization of Phage DNA During Its Replication in the Bacterial Cell.- Conclusion.- Literature Cited.