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bacilli infected with a virus. Elimination of the virus, which can be done by a 

 variety of methods, leads to production of a non-toxicogenic or non-pathogenic 

 strain. A large amount of experimental data leads to the conclusion that there 

 is a 1 to 1 correspondence between cells carrying the virus and those able to 

 produce the toxin. 



CHARGAFF: Who did this, work? 



SPIEGELMAN: It was first observed by Freeman in 1950. Groman in 

 Seattle has done the most extensive work and recently, Foxdale and Pappen- 

 heimer in New York have contributed to the problem. The most recent paper by 

 Groman (9) presents the most conclusive evidence on the question. 



KAMEN: Is that in the Journal of Bacteriology? 



SPIEGELMAN: Yes, most of this work has been published in the 

 Journal of Bacteriology. 



I think that most of us who have been close to this area in the last sev- 

 eral years, have found it difficult to digest the amazing amount of fundamentally 

 new and unexpected information that has emerged from these researches. Cer- 

 tainly the ability of exogenous agents to incorporate themselves completely into 

 the genetic apparatus of host cells and confer not only the obvious property of 

 lysogeny but, in addition, other genetic properties is most unexpected. 



Let me describe one ingenious experiment that demonstrates clearly 

 that for a while the viral agent remains as an independent entity in the cytoplasm 

 These experiments were carried out by Lederburg and Stocker. They possessed 

 a non-lysogenic strain that was also non-motile, lacking flagella. They exposed 

 this strain to a viral agent derived from an organism that was motile. If the 

 viral agent were to incorporate itself into the genetic apparatus of the host im- 

 mediately and also carry over the genetic ability to produce flagella, then all of 

 the cells produced from such an infected cell would be capable of producing 

 flagella. Should the virus remain in the cytoplasm for a time, however, and be 

 transmitted in a random manner from one cell generation to the next, then some 

 cells would come off lacking the viral agent and therefore, also the genetic abil- 

 ity to produce flagella. These possibilities were tested by placing virus-infect- 

 ed non-motile organisms on a moist agar plate. As soon as a cell produces 

 flagella it will start to move and in the course of changing its position, it will 

 divide. If one of the daughter cells comes out lacking the viral particle, it will 

 lose its flagella and, therefore, be unable to move. The daughter cell possess- 

 ing flagella will move on. Under these circumstances then, you would expect to 

 obtain a trail of non-motile ancestors along the path of the flagellated organisms. 

 This trail eventually disappears when the virus agent becomes fixed in the 

 chromosomes. Such trails were indeed observed in these experiments and they 

 represent a beautiful demonstration on a cellular basis that there is a lag before 

 these agents become fixed into the genetic apparatus. 



KAMEN: Well, if I wanted to concoct (which would take us into the 

 noon hour) a theory of radiation it would be that in every cell population you have 

 a certain percentage that is radiosensitive by virtue of the fact that you have in- 

 corporated into the chromosomal apparatus a unit that is lysogenic. 



SPIEGELMAN: That is where Pollard's magnification theory may 

 come in. We must bear in mind the possibility that these represent very special 

 biological groups that have evolved this symbiosis. 



