STUDIES IN THE METABOLISM OF ACTINOMYCETES IV. CHANGES IN REACTION AS A RESULT OF THE GROWTH OF ACTINOMYCETES UPON CULTURE MEDIA

Abstract

We have a great deal of information on the influence of reaction 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 attempts 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 microtorganisms 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 equivalent to pH 5.0 and thus approach a maimum acidity for the organism. Clark (1915) confirmed the conclusion of Michaelis and Mar-cora (1912) that the final hydrogen-ion concentrations are a physiological constant for B. coli; the greater the buffer effect of the 31