nelson: screening methods in microbiology 327 



of knowledge of the biosynthetic paths and mode of action of anti- 

 biotics at the molecular level. A beginning- to the solution of these 

 problems is now being made (35, 48, 53, 60, 71 , 83, 86, 117). It is possi- 

 ble that the empirical approach has been over extended, and an 

 amount of effort comparable to that expended on repetitive screening 

 but directed towards these two problems would provide methods for 

 designing rather than discovering new antibiotics. 



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