Glucose and Mannitol by B. coli communis. 



91 



With regard to the removal of the hypothetically produced acetaldehyde 

 from the sphere of the fermentation by reduction, it may be noted that one 

 would expect in the case of a mannitol fermentation not to be able to detect 

 the presence of as much acetaldehyde in the solution as in the case of a 

 similar fermentation with glucose. The writer has sought for acetaldehyde^in 

 the case of mannitol fermentation and has failed to detect it, a fact in 

 harmony with the above consideration. 



Summary and Conclusions. 



By allowing B. coli communis (suspended in saline solution) to act on 

 glucose it has been found that the proportion between the products of 

 decomposition differs considerably from that obtained in the earlier experi- 

 ments in which the organism was allowed to grow in a mixture of glucose 

 and peptone, a greater proportion of alcohol, acetic acid, and succinic acid, 

 and smaller proportion of lactic acid being obtained. 



The conclusions wliich may be drawn from the results refer in the first 

 place to B. coli communis in particular, and in the second place to bacterial 

 fermentation in general. 



In particular it has been shown that : 



(1) Succinic acid has an origin in common with acetic acid and alcohol. 



(2) The formation of lactic acid is independent of the formation of the 

 above three products. 



(3) The enzymes which effect the decomposition of glucose also co-operate 

 in the decomposition of mannitol. 



With regard to bacterial fermentation in general the experimental results 

 point to the independence of the intracellular ferments. 



The experiments of Harden and Penfold,* and later of the writer,f upon 

 B. coli conwiunis grown in the presence of a chloroacetate showed that by 

 artificial selection a strain could be obtained which yielded products from 

 glucose in different proportions from those in which they were formed by the 

 original strain, and since this difference in proportion of products must 

 correspond to a difference in proportion of the enzymes forming them, or of 

 the activity of these enzymes, which for practical purposes is the same thing, 

 it is clear that artificial selection can vary the proportion between certain 

 enzymes, and this is good evidence that they are independent of one another 

 in the original cell. The further results here recorded give additional 

 evidence of this, for they show that with the unselected organism, even when 

 the whole process of fermentation only occupies 48 hours, considerable 



* Harden, A., and Penfold, W. J., ' Roy. Soc. Proc.,' B, vol. 85, p. 415 (1912). 

 t Grey, E. C, ' Eoy. Soc. Proc.,' B, vol. 87, p. 472 (1914). 



VOL. XC. — B. I 



