The effect of the pH of the medium during growth on the enzymic activities of bacteria (Escherichia coli and Micrococcus lysodeikticus) and the biological significance of the changes produced

Researches of recent years on the enzymic activities of micro-organisms have shown that the bacterial cell possesses a very variable enzymic constitution. Karstrom 1938 pointed out that bacterial enzymes can be divided into two main classes: adaptive enzymes which are formed by the cell in response to the presence of the specific substrate, and constitutive enzymes which are formed whether the corresponding substrate is present during growth or not. This covers only one aspect of enzyme variation as both adaptive and constitutive enzymes undergo considerable variation with the physical conditions holding during growth. Thus the activities of the cells may alter with the tempe-ature and degree of anaerobiosis during growth, the age of the culture and the presence in the medium of substances which are not related to the enzyme substrate, etc. The present communication deals with the alterations in enzyme activities of two organisms, E. coli and. M. lysodeikticus, with the pH of the medium in which they are