J. BRONFENBRENNER 537 



RELATION BETWEEN LYSIS AND PRODUCTION OF PHAGE 



Dissolution of bacteria and the accumulation of the active agent causing this dis- 

 solution are the two characteristics which originally centered the attention of Twort 

 on the phenomenon of transmissible lysis. Although in his original publication Twort' 

 described most of the properties of the active agent (which was later called "bacterio- 

 phage"), he did not commit himself on the question of its nature, origin, or mode 

 of action. It is apparent, however, that he considered the disintegration of bacteria 

 as the main part of the process, and the regeneration of the active agent as a neces- 

 sary consequence. With this basic conception in mind, Twort saw a priori three al- 

 ternative possibilities for explaining the mechanism of the phenomenon he discovered. 

 Each of these possibilities, formulated by him merely as suggestions, were later de- 

 veloped and supported by others. The first two suggestions were outlined on the as- 

 sumption that the active agent is derived from the bacteria themselves. The third 

 one is based on the assumption that bacteriophage originates outside the bacteria. 



The first possibility is that the active agent represents the filterable stage in the 

 abnormal life cycle of bacteria, capable of inducing a similar deviation in the devel- 

 opmental process of other homologous bacteria.^ The second possibility is that the 

 active agent is an autolytic enzyme which destroys bacteria and which is, in turn, 

 set free in increasing amounts as bacteria undergo dissolution. ^ The third possibility 

 suggested by Twort is that the active agent is not a product of bacteria, but an auton- 

 omous virus capable of destroying bacteria by causing an acute infectious disease. 1 



As stated previously, all the views of Twort as well as of those who developed them 

 further, and particularly those of D'Herelle, suggest that lysis of bacteria is the main 

 phenomenon, the increase in concentration of the active agent being only the con- 

 sequence of the former.^ Since the accumulation of phage, according to such views, 



'Twort, F. W.: Lancet, 2, 1241. 1915. 



2 This conception has been later offered independently by Gamaleia (Gamaleia, N. F.: Prophy- 

 lakticheskaia medicina, p. 28. 1925) and also by NicoUe (NicoUe, C: Arch. Inst. Pasteur de Tunis, 14, 

 105. 1925) as the most logical explanation of the phenomenon of transmissible lysis. No experi- 

 mental evidence was oflered by these authors in support of their views. 



3 The view that the active agent is a ferment is held by a large group of workers today. How- 

 ever, they fail to consider the fact that living bacteria are not affected by enzymes applied from with- 

 out. See Kuttner, A. G.: Proc. Soc. Expcr. Biol. (2° Med., 18, 222. 192 1; Pico, C. E.: Compt. rend. 

 Soc. de binl., 87, 687. 1922; Prausnitz, C: Klin. Wchnschr., i, 1639. 1922; Hajos, K.: Ztschr.f.Im- 

 mimitdtsforsch., Orig., 37, 147. 1923; Combiesco, D.: Compt. rend. Soc. dc biol., 87, 17. 1922; Davison, 

 W. C.: Ahstr. Bad., 6, 159. 1922. 



■•This is essentially the same conception which was formulated independently by D'Herelle two 

 years later. Following the progress of the lysis under a microscope, D'Herelle came to the conclusion 

 that the active agent is an organized corpuscular parasite (protobe) which is attracted to bacteria 

 in virtue of chemotaxis. "The protobe then penetrates the peripheral zone of the bacterium (the 

 openings made remaining open) and multiplies within the bacterial protoplasm, forming a colony 

 composed of a number of elements varying with the conditions of the moment. When the process 

 of multiplication is completed the parasitized bacterium ruptures and undergoes a sudden dissolu- 

 tion. This liberates the young protobes, and each of the latter is then ready to repeat the process and 

 parasitize the nearest bacterium. Thus the cycle begins anew, and continues until all of the bacteria 

 present in the media have disappeared" {The Bacteriophage and Its Behavior [trans. Smith], p. 370. 

 1926). 



sd'Herelle, F.: The Bacteriophage and Its Behavior, p. 74. 1926. 



