INVESTIGATIONS ON A LYSOGENIC BACILLUS 

 MEGATERIUM 



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Andre Lwoff and Antoinette Gutmann 



Department of Microbial Physiology of the Institut Pasteur 



I. Introduction 



We call lysogenic bacteria those bacteria which perpetuate the capacity to 

 form bacteriophages without intervention of exogenous bacteriophages. This 

 definition will be discussed and justified in the course of this work. Thanks to 

 the investigations of J. Bordet, of F. Burnet and M. McKie, of Den Dooren de 

 Jong, of E. and E. Wollman, and of J. Gratia, it is known: 1. that in a lysogenic 

 strain lysogeny is an attribute of every bacterium and, in the case of sporogenic 

 species, of every spore; 2. that lysogeny persists after repeated passages in the 

 presence of a specific anti-bacteriophage serum; 3. that lysogenic bacteria adsorb 

 the bacteriophages which they produce; 4. that lysozyme lysis does not liberate 

 bacteriophages from potentially lysogenic bacteria; 5. that, starting from certain 

 sensitive strains infected by a given bacteriophage, one can isolate lysogenic 

 bacteria which produce a bacteriophage identical to the original bacteriophage. 



It thus seems strange that the very existence of lysogenic bacteria could have 

 been put in doubt by A. D. Hershey and J. Bronfenbrenner (1948), who wrote: 

 "How virus is transmitted from cell to cell in lysogenic cultures seemingly 

 refractive to lysis remains to be clarified. It must be concluded, however, that 

 the phenomenon of lysogenesis, frequently cited as evidence for the spontaneous 

 intracellular origin of virus, can equally well be explained as some type of 

 association between exogenous virus and incompletely susceptible bacterium." 

 It seems that one must look for the origin of the skepticism in a possibly too 

 narrow definition of "true" lysogeny due to M. Delbriick (1946), which restricts 

 lysogeny to the case where the bacteriophage is liberated by bacteria in the 

 absence of lysis. Since no example of this phenomenon is known, lysogeny 

 vanishes. This "true" lysogeny was contrasted by M. Delbriick with "pseudo- 

 lysogeny," in which bacteriophages are liberated following the lysis of sensitive 

 bacteria, the latter being produced by mutation in the course of the growth of a 



Translated from the French and reprinted by permission of the 

 authors and the Institut Pasteur from the Annales de l'Institut 

 Pasteur, 78, 711-739 (1950). (N.B. A part of the section 

 "Materials and Techniques" has been omitted from the translation 

 of this paper.) 



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