BIOCHEMISTRY OF STREPTOCOCCUS HEMOLYTICUS 219 



whereas the structural needs are practically complete when the 

 cell attains its morphological maturity. Consequently the fuel 

 requirement is one of comparatively long diuation. According 

 to the same authors, a rapid disintegration of fuel materials 

 occurs in the case of saprophytic bacteria. In other words, such 

 microorganisms must, in general, be considered more active 

 chemically than are pathogenic bacteria. 



In the experiments conducted with the streptococcus it has 

 been noted that growth in vitro is always accompanied by elabor- 

 ation of acid products through the fermentation of materials of 

 carbohydrate nature.- No medium has ever been used which 

 does not respond to the fermentative activities of this organism. 

 Kendall, Day, and Walker (1913b) state that when bacteria 

 are metabolizing carbohydrate the nitrogen requirement is 

 minimal, so that in glucose broth cultures of Streptococcus hemo- 

 lyticus we would expect the katabolic or ''fuel" phase to pre- 

 dominate over the anabolic or structural phase of metabolism. 



Moreover, the presence of horse serum in broth was found to 

 exercise a decided stimulatory effect upon growth rate and acid 

 formation, and also proved effective in permitting growth through- 

 out a wider range of hydrogen-ion concentration. From a con- 

 sideration of the fundamental features of bacterial metabolism 

 as outUned in the foregoing discussion, it would seem obvious 

 that these phenomena represent a stimulated metabolism of the 

 organisms brought about through some property of the serum. 

 It was suggested previously that structural or growth-accessory 

 substances are perhaps furnished by this material thus permitting 

 the organisms to inaugurate their metabolic activities earlier 

 with consequent reduction of lag. This theory would be in 

 accord with the statement of Kendall, Day, and Walker (1913b) 

 that the structural function always precedes the vegetative or 

 fuel function chronologically, inasmuch as the cell must be 

 formed before it can carry on its appropriate activities. 



The following experiments represent an attempt to study the 

 metaboUsm of the streptococcus in various culture media with 

 an especial effort to determine whether correlation exists between 

 the rates of acid formation and the rates of other metabolic 

 processes in (1) glucose broth, and in (2) glucose-serum broth. 



