ANDRE LWOFF AND ANTOINETTE GUTMANN 



the nucleus obligatorily accompanies the production of bacteriophages, then it is 

 evident that no bacterium could survive phage production. But it is possible to 

 conceive of production of bacteriophages without destruction of an essential 

 bacterial organelle. It is necessary, however, to think of a way for the bacterio- 

 phages to come out. One knows that lysogenic bacteria adsorb the bacterio- 

 phages. One is thus obliged to envisage a variation of bacterial properties which 

 allows certain bacteria to adsorb bacteriophages at certain stages and to let them 

 out at other stages. It is also possible to conceive that the bacteriophage is 

 liberated when all the elements capable of fixing the bacteriophage are "satu- 

 rated." Thus liberation of bacteriophages in the absence of bacterial lysis is 

 theoretically possible, but at the present time we do not know of any such case.^ 

 And in the only case in which the mode of liberation of bacteriophages by a 

 lysogenic strain was studied with techniques offering sufficient guarantees, the 

 mode of liberation of bacteriophages was bacterial lysis. 



VII. Factors of Bacteriophage Production 



The reader has no doubt noticed that in certain of our experiments all of the 

 bacteria put into a little drop grew and multiplied, whereas in others all the 

 descendants of one bacteria lysed. We thought at the outset that the sudden 

 change of medium was responsible for the onset of bacteriophage production. 

 In order to explain the fact that only a certain percentage of the bacteria was 

 lysed, the hypothesis was envisaged according to which this change only induced 

 the lysis if it took place at certain stages of the life cycle of the bacterium; for 

 instance, during nuclear division. But, we subsequently observed considerable 

 differences between different series of the experiments. On a certain day, for 

 example, we had put 18 bacteria in three drops; all of them divided. The 153 

 bacteria from these divisions were lysed by lysozyme: no bacteriophages. There 

 had been no production of bacteriophage. On another day, we started with 38 

 bacteria divided among 5 drops. The descendants of three groups did not show 

 any lysis. The descendants of two groups did lyse partially, and all of the 

 descendants of two other groups lysed. The following results correspond to the 

 study of 104 groups of bacteria: 



Initial number 6 4 8 4 8 4 4 



Maximum number 17 41 29 13 34 8 10 



Number of lysed bacteria 12 14 8 10 



Proportion of lysed bacteria.... 0/17 0/41 0/29 12/13 14/34 8/8 10/10 



iW. H. Price noticed a massive liberation of bacteriophages by cultures of Staphylococcus 

 muscae of constant optical density. The ratio of bacteriophages to bacteria rises from 0.2 

 to 26 in about 30 minutes. A similar phenomenon was observed in cultures of Bacillus rnega- 

 terium by A. Lwoff, L. Siminovitch, and N. Kjeldgaard (unpublished observations), who 

 interpret the phenomenon in the following manner: The optical density of the culture remams 

 fairly constant, or increases slightly, but the bacteria lyse in the course of the dilutions which 

 precede spreading for assay on the petri dishes. This phenomenon shall be described and 

 discussed in detail in a communication which shall appear soon in this periodical. We thus 

 consider that the experiments of Price do not bring any proof of liberation of bacteriophages 

 in the absence of bacterial lysis. 



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