The Biochemistry of the 

 Bacterial Viruses 



E. A. EVANS, Jr. 



The contemporary biochemist, being a practical man, is for the most 

 part working in areas that are amenable to his efforts and give him 

 information of a precise, detailed, and orderly nature, such as we have 

 at the moment with respect to the oxidation of carbohydrates in muscle 

 tissue. However, there are certain areas of biological interest which 

 would seem not to lie entirely within our biochemical reach and which 

 are also not clearly beyond it. Although these frequently offer sharp 

 reminders of our limitations, they give also the pleasures of unexpected 

 discovery. The study of the mechanism of viral reproduction is such 

 a field at the moment. The contributions of the chemist to the rapidly 

 developing understanding of this process must necessarily lag behind 

 the more dexterous explorations of the microbiologist and geneticist, 

 but they have the virtue of carrying the description, even though 

 incomplete, to the ultimate molecular level. 



However, to discuss the biochemistry of viral reproduction is to 

 speak of special cases. The agents which we define as viruses, purely 

 from an operational point of view, embrace a range of composition 

 and morphology that makes it unwise to expect or predict general 

 characteristics. They may vary in size from the small spherical parti- 

 cles responsible for foot and mouth disease or tobacco necrosis, roughly 

 of the magnitude of certain protein molecules, to agents as large as 

 that of vaccinia^ larger than some microorganisms. A similar degree 

 of heterogeneity is shown in what we know of their chemical com- 

 position. The smaller particles { the bacterial, plant, and insect viruses) 

 appear to contain only nucleic acid (either DNA or RNA) and protein 

 in varying proportions, but the larger agents contain lipides and a 

 variety of other components. However, the difficulties involved in the 



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