218 THE PHYSICS OF VIRUSES 



The kind of process envisaged is shown in Fig. 8.10. The 

 center, internally active i)art of the virus is thought of as long 

 and thin and comprising nucleoj)rotein units joined together by a 

 mixture of Van der Waals forces and hydrogen bonds. The units 

 are firmly, but not inseparably, bound. This long, thin unit offers 

 a large surface area to the metabolizing bacterium and, as a 

 result, rapidly changes the molecular environment so that fresh 

 nucleoprotein begins to be formed. As this takes place, the 

 immediate neighborhood begins to be populated by subunit 

 nucleoproteins, each capable of influencing protein and nucleic- 

 acid synthesis as described earlier. These are attracted to the 

 original nucleoprotein and also to one another and begin to form 

 alongside the first virus element as shown in Fig. 8.10b. As they 

 aggregate to form new lines along the old virus, the ionic atmos- 

 phere changes to make possible a re])ulsion. As soon as there are 

 several lines formed on each side of the parental virus, the Van 

 der Waals attraction ceases to be enough to overcome the ionic 

 repulsion, and the new units are driven out. Some are complete 

 and some are not. Each unit now starts its double process, of 

 charging the metabolic synthesis mechanism and of mutual 

 accretion. 



This process will develop exponentially, and before long the 

 cellular metabolism will have become almost wholly a virus me- 

 tabolism contained in the cellular envelope. At a stage, which is 

 about three-quarters of the whole duration of single cell develop- 

 ment, the nucleic acid synthesis becomes essentially complete. A 

 further protein synthesis continues until the virus i)articles are 

 covered with a protein sheath which includes the enzymes 

 necessary to produce cellular lysis and entry in the first place. 

 These are able to produce lysis in any event and, in the case of 

 bacterial viruses, do so, liberating a burst in the well-known way. 



We have mentioned that some incomplete virus chains will be 

 formed. To some extent, these must remain until the burst occurs 

 and must be part of the whole debris which is found at that 

 time. However, there must also be some over-all checking proc- 

 ess, as suggested by Dancoff (1949), which renders the multi- 

 plication of smaller units unfavorable. Perhaps this can be found 



