The enzymes of Bacillus coli communis . Part VI.―The alternative modes by which B. coli communis may bring about the anaerobic decomposition of glucose

Abstract

The previous work which has been described in this series, has led to the recognition of the independence of many of the enzymes of Bacillus coli communis (see this series, 1914, 1917, 1920) and finally to a simple theory of bacterial fermentation in general (see this series, 1924). While admitting that some of the enzymes of bacteria may be specifically adapted to get upon certain configurations of atoms, this theory postulates that there exist within the bacteria cells, in all cases, enzymic mechanisms of a more fundamental character, a few of which suffice to bring about a great variety of chemical changes. These fundamental mechanisms divide themselves into two groups —those connected with intramolecular oxidations and reduction, and those concerned with the separation of carbon atoms. Stabilisation of the products of primary cleavage is considered to occur automatically and not to require additional enzymes. The course of any fermentation would depend upon the relative rates of action of these two fundamental modes of decomposition. The rate of action of the oxidation-reduction mechanism would moreover be conditioned by the availability of acceptors for oxygen and hydrogen, and hence this mode of decomposition is more complex and not so independent of the conditions as the latter mode, which brings about simple cleavage and intramolecular rearrangement of atoms. If this theory is correct it should follow that when the conditions of like for a micro-organism are difficult (as for example when the nutrition is poor, when there is prolonged anaerobiosis, and when the organism is old, or enfeebled by toxic influences) it should bring about less oxidation and reduction, and more simple cleavage and intramolecular rearrangement of the substrate. In the case of B. coli communis therefore, less alcohol, formic acid, succinic acid and carbon dioxide, and more lactic acid. The case of acetic acid cannot be considered for the moment, as it might conceivably arise by either mechanism.