BIOCHEMISTRY OF STREPTOCOCCUS HEMOLYTICUS 231 



in which the organisms are making their growth. During this 

 period, in which it may be presumed that anaboUc processes 

 are actively under way, the organisms are utihzing amino acids 

 for structural purposes. This would cause the latter to decrease 

 in concentration in the medium and furthermore would produce 

 an increased excretion of ammonia through the katabolism of a 

 part of the absorbed amino acids. 



5. Subsequent to the period in which the organisms have made 

 their growth a rise in the curves of amino acid formation is mani- 

 fest. In the cultures containing horse serum this rise is initiated 

 by the sixth hour; in the glucose culture it appears by the ninth 

 hour. A decrease in ammonia output, in general, accompanies 

 the rise in amino acid formation. These findings indicate that 

 a decreased utilization of nitrogenous materials ensues after the 

 organism has passed its maximum period of growth, despite the 

 fact that proteolysis continues. 



6. A marked difference in nitrogen metabolism between a 

 passage strain and a laboratory strain of Streptococcus hemolyticus 

 is noted during the first three hours of incubation in glucose 

 serum broth. Whereas the passage strain shows a definite 

 decrease in amino acid output coupled with an increased am- 

 monia excretion, the laboratory strain exhibits a decided increase 

 in amino acid output coincident with a slight decrease in am- 

 monia formation. Whether or not this represents a permanent 

 deviation in metabolism resulting from continued transplantation 

 upon artificial culture media is a question that for the present 

 must remain undecided. 



REFERENCES 



Anthony, B. V. A., and Ekroth, C. V. 1916 Practical observations on titra- 

 tion and adjustment of culture media. J. Bact., 1, 209. 



Avery, O. T., and Cullen, G. E. 1919a The use of final hydrogen-ion con- 

 centration in differentiation of Streptococcus hemolyticus of human and 

 bovine types. J. Exper. M., 29, 215. 



Avery, O. T., and Cullen, G. E. 1919b Hydrogen-ion concentration of cul- 

 tures of pneumococci of the different types in carbohydrate media. 

 J. Exper. M., 30, 359. 



Ayers, S. H. 1916 Hydrogen-ion concentration in cultures of streptococci. 

 J. Bact., 1, 84. 



