BACTERIA WITH HIGH LEVELS OF SPECIFIC ENZYMES 105 



increase in the number in the chromosome itself or by incorporation of 

 the lac genes into an autonomous unit replicating independently of the 

 chromosome, such as an episome. At present there is no reason to be- 

 lieve that the presumed extra lac genes in the strains isolated here are 

 associated with the F factor. Moreover, it will be difficult to establish 

 their episomic character if the episome is not transferable from cell to 

 cell. 



It is possible that the high rates of /?-galactosidase observed here 

 result from mutations which cause the individual galactosidase genes to 

 function more rapidly in the processes leading to protein synthesis, 

 whatever this means. But obviously a decision cannot be made, from 

 the present evidence, between this and the other possible explanations 

 suggested here. Further studies of the genetics and physiology of these 

 bacteria are required. 



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