INTRODUCTION 



13 



lated a revival of interest in studies of the development of bacterial toxins and 

 has opened entirely new fields of research such as the microbiological assay of 

 vitamins and amino acids. The importance of these new paths of investigation 

 can, as yet, only be estimated but it is already apparent that the knowledge which 

 has been acquired is of essential value in an understanding of bacterial metabo- 

 lism. Among studies in the first of these fields may be mentioned the work of 

 Mueller and his associates^^'^^'^^'^^'^*-^^ on the production of diphtheria toxin; 

 that of Tamura et al.^® of toxin of Clostridium welchii; that of Bunney and 

 Loerber2'''28 on scarlet fever toxin, and of Favorite and Hammon^^ on staphylo- 

 coccus enterotoxin. The work of Snell and Wright^^ may be mentioned as but one 

 of many references to investigations on the assay of vitamins by means of 

 microbiological methods. Closely associated with research of this nature are such 

 studies as those of Mueller^^'^^ on pimelic acid as a growth factor for Corynebac- 

 terium diphtheriae, and those of O'Kane^^ on synthesis of riboflavin by staphylo- 

 cocci. 



In this brief discussion of certain phases of bacterial nutrition we have at- 

 tempted to indicate the complexity of the subject and to emphasize the impor- 

 tance of continued study of bacterial nutrition. Difco Laboratories has been en- 

 gaged in research closely allied to this problem in its broader aspects since 1914 

 when Bacto-Peptone was first introduced. Difco Dehydrated Culture Media, and 

 ingredients of such media, have won universal acceptance as useful and depend- 

 able laboratory adjuncts in all fields of microbiology. 



'I: 



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