Dehydrogenations Produced by Resting Bacteria. IV

Abstract

Resting bacteria may be investigated in a similar manner to enzymic or catalytic systems, and their reactions are independent of those which occur only when proliferation is proceeding. One hundred three substances were examined as possible donators or acceptors of H in Eresence of resting Bacillus coli (using the methylene lue technique). Since 56 of these are activated, that is, can donate or accept H under conditions when they are inert in the absence of the organism, it seems doubtful that 56 specific "H transportases" exist in the cell. The main site of reduction is at the outer surface of the organism, of which the cell membrane is as characteristic a feature as any structure within the cell. The physico-chemical constitution of the cell membrane is discussed at length with reference to the existence over the cell surface of many locally intense electric fields, these being a function of the "geography" of the surface. A consideration of the effects induced in a molecule by the application of an external electric field may form the basis of an interpretation of the mechanism of activation. These effects are investigated on the lines laid down by Sir J. J. Thomson, and many examples are given of equation representing the change after maximum activation, the polarizing field being the activating source. A variety of considerations outlined permit a consistent interpretation of asymmetric oxidation of the double bond; relative inertness of glutaconic acid compared with fumaric acid; relative inertness of glutaric acid compared with succinic acid; oxidation of branched chains; differences between activations of cis and trans isomers; differences between activations of aspartic and glutaminic acids; and the [alpha] oxidation of propionic acid in contrast to the general rule of [beta] oxidation. Predictions from the theory are made and verified. It does not follow that there do not exist in the cells certain specific enzymes related to oxidation-reduction processes. Their presence may be possible, for if a certain structure possesses chemical or physical characteristics closely related to some particular substrate, then only the latter may become "accessible" to the activating power of the structure, which would be regarded as a specific enzyme. The mechanism of activation, however, would still be explained on the lines indicated. From such considerations it is held that a surface structure may induce a variety of reactions, each differing in some way from the other, so that the appearance of the presence of a large number of enzymes is obtained. The cell surface, or an intracellular surface, can, in a sense, be regarded as an assemblage of specific enzymes, but enzymes which are inseparable because they are actually a function of the surface structure. As such structures become smaller in size, the variety of reactions to which they give rise will become smaller and hence the specificity of their effects will apparently become greater until eventually a structure may be reached for which high specificity may be claimed; but there is no distinct line of demarcation between such a highly specific structure and that of a cell surface (such as B. coli) which can accomplish at least 56 activations.