STUDIES IN THE NITROGEN METABOLISM OF 



BACTERIA* 



H. J. Sears 



From the Department of Bacteriology and Immunology of Stanford University, California 



A chemical study of the metabolism of any organism is generally 

 understood to mean a study of the food materials, the changes which 

 take place in these materials within the organism, the agencies which 

 bring about these changes, and the character and composition of the 

 excretory products. It is obvious that the food materials of micro- 

 organisms may be as completely studied as those of higher forms. To 

 determine the changes these undergo within the cell, however, and the 

 exact composition of the excretory products is a problem of a much 

 more difficult nature than the same task would be in the case of the 

 higher plant and animal species. 



At present, students of bacterial metabolism must content them- 

 selves solely with the study of the beginning and the end of the process. 

 What takes place within the cell can only be surmised from the nature 

 of the enzymes which have been expressed from the bacterial bodies 

 and from the composition of the products of bacterial action. Fur- 

 thermore, it must be recognized that the substances found in a bac- 

 terial culture medium after a period -of growth need not all neces- 

 sarily represent the end products of metabolism. There are numerous 

 possibilities for alteration of the true metabolic products by means of 

 their mutual action upon one another. 



In the knowledge of these difficulties, therefore, we shall have to 

 interpret the title of this paper to mean merely a study of the nitrog- 

 enous constituents of the food supply of bacteria and a chemical 

 examination of the products of the action of bacteria upon these food 

 substances. 



There has been no attempt on the part of investigators to make a 

 complete study of the metabolism of any micro-organism. In fact, 

 such a study would, in most cases, include so wide a variety of food 

 materials and metabolic end products that the large amount of work 

 involved would hardly be in keeping with the benefit to be gained from 



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