INTRACELLULAR MULTIPLICATION OF BACTERIAL VIRUSES 239 



the "T-even" strain T2, T4, and T6. This limited range of experimental 

 material permitted direct comparison and integration of the results of many- 

 different workers and was of great heuristic value, although it now seems 

 likely that the discovery and understanding of other aspects of bacteriophages 

 of no less fundamental interest than their multiplication, e.g., of lysogeny and 

 transduction, was retarded by the choice of this particular phage-host 

 system. Almost all of the insight into the subject matter of the present chapter, 

 however, has come from experiments carried out with the T-even phages. 

 Hence, it may be assumed that, unless exphcitly stated otherwise, and with 

 the exception of the section devoted to comparative bacterial virology, the 

 post- 1940 work mentioned in the following pages concerns one of these three 

 closely related bacteriophage strains. 



The topics of this chapter have been the subject of numerous reviews since 

 d'Herelle's first monograph on the bacteriophage in 1921 and the publication 

 of the polemics of d'Herelle, Twort, Bordet, Gratia, and others at the 1922 

 Meeting of the British Medical Association {Brit. Med. J. 1922, 289-299). The 

 reader who wishes to acquire a first-hand acquaintance with the evolution of 

 the knowledge of bacterial virus multipHcation may profit by perusal of some 

 of these reviews, like those of Bronfenbrenner (1928), Bordet (1931), Burnet 

 (1934), Delbriick (1942, 1946), Cohen (1949), Luria (1950), and Hershey (1952, 

 1956). 



II. Kinetics of Phage Reproduction^ 



A. One-Step Growth 



The basic manifestation of bacteriophagy is the following: A growing 

 bacterial culture is inoculated with an emidsified sample of the ecological 

 environment of the bacterial type imder study, whereupon lysis of the 

 infected culture suddenly ensues several hours later. A second bacterial 

 culture is now infected with a very high dilution of this lysate and lysis of 

 the second culture again ensues suddenly after several hours' incubation. The 

 process of lysing bacterial cultures by inoculation with high dilutions of 

 previous lysates can be continued indefijiitely, i.e., the lytic principle, or 

 bacteriophage, is serially transmissible. From the very start, d'Herelle 

 interpreted this phenomenon in terms of infection of a few bacteria of the 

 culture by a few phage particles in the inoculum, followed by intrabacterial 

 multiplication of the infecting phages to yield an issue of many progeny 



^ In all of the experiments discussed in this chapter, the assay for the number of 

 infective bacteriophage particles is carried out by means of the •plaque-counting method 

 and the temperatm-e of incubation is in the vicinity of 37°C. A description of the experi- 

 mental techniques and methods employed in modem bacteriophage research can be 

 found in Adams (1950). 



