UNITY AND DIVERSITY IN THE METABOLISM OF MICRO-ORGANISMS 



sible areas for the microbes. Barely had one specialist among micro- 

 organisms been discovered when another even more spectacular one 

 was announced; the microbiological theatre resembled one grand 

 naturalistic vaudeville show. 



However great may be our admiration for those who, through their 

 intuition and ingenious experimentation, have guided this flight of 

 general microbiological discoveries, and however indispensable has 

 been this thorough exploration of the microbial world for the contin- 

 ued development of microbiology, in the long run this approach 

 could not persistently be satisfying. Even while the main current of 

 microbiological research was concentrated on the diversity, a field of 

 study gradually developed in which a search for unity in the diversity 

 became apparent. It would be unjust to depict this trend as an entire- 

 ly new and recent development. Far from it: many classical figures in 

 microbiological science, and its founder, Pasteur, in the very first 

 place, must receive honourable mention in this connexion. Neverthe- 

 less, one may safely say that the attempt to view microbial metabolism 

 in the light of the outcome of general physiological research has been 

 deliberately initiated by the German physiologist and hygienist Rub- 

 ner, only at the beginning of the twentieth century. And we may im- 

 mediately add that thus far this approach has found very little re- 

 sponse. This regrettable fact can be readily explained by the circum- 

 stance that microbiology has hitherto developed primarily as an ap- 

 plied science. By far the majority of medical, technological, and agri- 

 cultural microbiologists have studied the role of microbes in the im- 

 portant and eminently practical problems they had to face. And of the 

 relatively very small number of investigators who did have the oppor- 

 tunity and desire to study microbes for their own sake, the majority 

 was under the spell of the diversity; quite understandably so in view 

 of the fascination of this type of work. 



If now I am going to embark on the attempt to give you a glimpse 

 of the unity that can be discovered in microbial metabolism, I do so 

 with the full knowledge that it is but a meagre account I have to 

 offer. That nevertheless I have ventured to solicit your attention for 

 this topic finds its explanation in the fact that I shall thus have the 

 opportunity to make you realize that this still presents an immense 

 field of endeavour. It seems to me that the solution of the problems in 



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