196 Discussion 



and a lysis transformation such as we have demonstrated might easily 

 produce a dramatic increase in resistance in such a mixed culture. 



Lederberg: Since Dr. Hotchkiss has brought this up, a word of caution 

 may be added. There has been some misunderstanding in the literature 

 about the possible role of transformation in the development of resistance 

 in bacterial cultures. It has been suggested, for example, that an initial 

 resistant cell might arise by some unspecified process, perhaps by spon- 

 taneous mutation, and that this quality could then spread through the 

 population by a transformational process. In all of these cases you are 

 very lucky indeed if you get anywhere near one new resistant for each 

 resistant cell which has died and released its DNA. In most cases that 

 figure is very low, and in no case does it exceed one in any practical 

 situation. For this reason, transformation is not a means by which the 

 proportion of resistant cells in a culture can rapidly increase. 



