The latent fermenting powers of bacteria.—Nos. I - Ill

Abstract

In the series of communications published in the 'Proceedings of the Royal Society' from 1914 to 1921 the writer (1) has traced the fluctuations in the various products of the degradation of carbohydrates under the influence of B . coli , and, amongst the various relationships which are to be seen, has drawn attention to the specially close relationship between succinic and acetic acids. A glance at the structural formulæ of these substances is sufficient to give the impression that a relation between them is most likely; but when we reflect upon the origin of succinic acid from carbohydrates we are faced with the difficulty that succinic acid is among the few end-products of fermentation which contain four carbon atoms. According to an earlier theory of the degradation of carbohydrates by bacteria (2), which runs parallel with the generally accepted theory of fermentation by yeast (3), (4), there is first a cleavage of the molecule of six carbon atoms into two molecules of three carbon atoms. On this theory succinic acid would have to be reformed by a resynthesis. But although this theory of primary cleavage into two triad molecules is true in very many cases, it is, according to the many results which the writer has accumulated lately, certainly not the whole truth, for there are other lines of break-down of the glucose molecule. That such might be the case was hinted at two years ago, but it was desired to accumulate more evidence. This evidence forms the subject of this and following communications. and a more comprehensive theory of fermentation by bacterial enzymes is propounded, which in brief is this: that carbohydrates can be split anywhere between two carbon atoms, so that a molecule of six may break up into two threes, three twos, a two and a four, and so on. The idea underlying the glycerine experiments was this: if succinic acid arises by the splitting of a molecule of glucose into a tetrad and a dyad molecule, then none should arise from the glycerine; whereas, if succinic acid is formed by a re-synthesis from two dyad molecules, it should arise from glycerine as well as from glucose. This, as will be seen later, was not the crucial test it appeared to be at the time; yet the results of the fermentation of glycerine are of interest, leading as they did to a series of experiments which revealed latent fermenting powers in bacteria.