Glucose and Mannitol by B. coli communis. 



89 



Each line is equivalent to a molecule of acetic acid, and the three are thus 

 equivalent to a molecule of glucose. 



Above and to the right is succinic acid, below and to the left acetaldehyde. 

 Ignoring the dotted line, to the left is alcohol. On the right below, the 

 removal of oxygen by an acceptor is represented ; if this acceptor is 

 acetaldehyde the product becomes acetic acid. Above and to the left 

 hydrogen is represented as being separated from the glucose molecule in 

 proportion corresponding to the oxygen, the two phenomena representing the 

 action of the reductase, the action of which it was suggested was impaired 

 under certain conditions (Grey, 1914). The acetaldehyde is thus represented 

 as having three possibilities as regards transformation. It may, as has been 

 previously suggested to account for the tendency under certain conditions for 

 alcohol and acetic acid to appear in equimolecular proportions (Harden, 1901), 

 undergo the Cannizarro condensation into equimolecular proportions of the 

 acid and the alcohol. It may become oxidised to the acid by the oxygen 

 represented on the right or reduced by the hydrogen represented on the left 

 of the scheme. 



The key for the working of such a mechanism is the existence of an 

 enzyme, or a co-operation between enzymes, capable of effecting simul- 

 taneously oxidation and reduction. Any interference with such a mechanism 

 would lead to a simultaneous diminution in the production of alcohol, acetic 

 acid and succinic acid. This simultaneous diminution has been established by 

 experiment as actually occurring. 



The Comjxirison iettveen the Fermentation of Glucose and that of Mannitol. 



In an earlier communication* the writer expressed the view that the 

 fermentation of mannitol and glucose by B. coli communis was brought about 

 by the same set of enzymes and that in general it was highly probable that 

 bacteria dealt with all carbohydrate molecules, and molecules of substances 

 allied to them such as the corresponding alcohols, upon a plan which was 

 characteristic for the bacterium ; in other words, that the products obtained 

 by the action of a bacterium depended upon the bacterial content of enzymes 

 rather than on the nature of the sugar. Only in the case of the formation of 

 the first intermediate product might a special enzynie be necessary for a 

 special carbohydrate configuration, but once the first intermediate product is 

 formed the remainder of the fermentation is effected in all cases in the same 

 way, modified only by the secondary reactions which may occur in the direction 

 of further reduction or oxidation, should the conditions give opportunity for 

 .such changes. 



* Grey, E. C, ' Eoy. Soc. Proc.,' B, vol. 87, p. 472 (1914). 



