66 PHYSIOLOGY OF BACTERIA 



to assume a different enzyme for each individual step in 

 each fermentation. 



Kluyver and Donker point out that different intensi- 

 ties of the affinity of the catalyst for hydrogen, i.e. 

 different intensities of the activation of hydrogen atoms 

 might bring about quite different reactions. They 

 further call attention to the great influence of hydrogen 

 ion concentration upon the reduction potential (see 

 p. 88). This potential will very probably be inter- 

 linked somehow with the activation of hydrogen. 



Another cause for differences of intensity of activation 

 by the same catalyst might be their arrangement within 

 the cell, and the distance between activator (catalyst) 

 and substrate (hydrogen donator). It will be shown on 

 p. 263 that a very definite arrangement of the essential 

 molecules in the cell is necessary. If the distance 

 between catalyst and substrate is larger in one species 

 than in another, the loosening of the bond of a certain 

 hydrogen atom will not be so great, and this may bring 

 about a different type of reaction. 



Besides, the type of reaction always depends upon 

 the hydrogen acceptors present. If oxygen and an 

 oxygen activator are available, the reaction must be 

 different from that under anaerobic conditions, even 

 with the same hydrogen activators (see the gas ratio of 

 Bact. coli, p. 64). 



While our knowledge is not sufficient to make accurate 

 statements, the present outlook in biochemistry indicates 

 that the complexity in fermentation processes does not 

 lie so much in the innumerable number of different com- 

 pounds reacting, but more in the adaptability of the 

 reacting compounds to all different conditions. 



Another step in this direction is the attempt of Utkina-Ljubowzowa 

 and Steppuhn (1929, 1930) to prove that the autolytic enzymes of 



