The Influence of pH Value and Aeration on the Growth of Aerobacter aerogenes and Bacterium coli in defined Media

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Abstract
The growth of A. aerogenes (NCTC-418) and B. coli (NCTC-5928) in glucose ammonium salt media was studied. The total amt. of growth depends on the pH, and is always greater in aerated cultures. Aeration of cultures, in which growth has stopped, stimulates growth. With B. coli there is a lag phase after aeration is started, and in the presence of excess glucose the pyruvate concn. immediately increases. Cessation of growth at pH values which have no effect in fresh media, is due to the production of formic acid, which is more toxic at lower pH. When A. aerogenes is grown in media containing an excess of citrate, growth in unaerated cultures ceases at a pH slightly higher than that at inoculation. Aeration causes growth to continue with further consumption of citrate.