Alkali-metal ions in the metabolism of Bact. lactis aerogenes II. Connexion with viability, growth rate and enzyme activity

Abstract

The viability of Bact. lactis aerogenes is uninfluenced by deficiency of potassium in the medium. The dehydrogenase activity towards glucose is less affected by an adverse pH when there is sufficient supply than when there is a deficiency of this ion. The deaminase activity towards asparagine or alanine is equally dependent on the pH in both cases. Maximum growth rates (in a glucose medium) are independent of pH over a range where the glucose dehydrogenase activity drops markedly, but decreases in this latter activity can be to a considerable extent compensated for if the cells are allowed to take up potassium or rubidium ions (as shown by experiments with 86 Rb). Protective response to an adverse pH seems to involve two factors, first, an absorption of alkali-metal ions associated with intermediates in the oxidation of the carbon substrate, and secondly, adaptive changes accompanying growth.