STUDIES IN THE METABOLISM OF ACTINOMYCETES 



IV. CHANGES IN REACTION AS A RESULT OF THE GROWTH OF 

 ACTINOMYCETES UPON CULTURE MEDIA 



SELMAN A. WAKSMAN and JACOB S. JOFFE 



Department of Soil Microbiology, New Jersey Agricultural Experiment Station 



Received for publication July 11, 1919 



We have a great deal of information on the influence of reac- 

 tion upon the growth of microorganisms as well as on the changes 

 of reaction of the medium which result from the growth of these 

 organisms. But, unfortunately, the largest amount of work along 

 this line has been done by merely titrating the medium, using a 

 single indicator, with acid or alkali solutions. Very few at- 

 tempts have been made actually to measure the concentration of 

 the hydrogen-ions in solution and study the effect of the buffers 

 upon these changes in reaction and thus obtain more definite data 

 upon the changes in reaction produced by microorganisms. This 

 has been recently pointed out by Clark and Lubs (1917) in a 

 series of investigations. Another point to be considered is the 

 fact that most of the studies of the changes of reaction of culture 

 media produced by microorganisms were conducted with protein 

 and peptone rich media, where the buffer effect of the substances 

 is very important, an effect which was usually not taken into 

 consideration. 



Michaelis and Marcora (1912) stated that B. coli will produce 

 in lactose bouillon, independent of the lactose content and initial 

 alkalinity of the solution, a concentration of lactic acid equiva- 

 lent to pH 5.0 and thus approach a maximum acidity for the 

 organism. 



Clark (1915) confirmed the conclusion of Michaelis and Mar- 

 cora (1912) that the final hydrogen-ion concentrations are a phys- 

 iological constant for B. coli; the greater the buffer effect of the 



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