136 PHYSIOLOGY OF BACTERIA 



No other data on rates of fermentation are known which could be 

 used for a similar analysis. 



SUMMARY OF FACTS 



The rate of enzyme action is accelerated by an increase 

 of temperature. At high temperatures, the deterioration 

 of the enzyme becomes also an important factor. 



The optimum temperature of enzyme action is nothing 

 definite; it shifts gradually, as the experiment is pro- 

 longed, to lower temperatures. This holds true for all 

 isolated enzymes, including yeast juice. 



For living cells, this holds true only above the optimum 

 temperature. At and below this point, the rate of 

 fermentation is constant. 



Fermentation will take place at very low temperatures 

 where growth has ceased altogether. Large numbers 

 of cells must be used to prove this. 



With some organisms, e.g., with thermophilic bacteria, 

 it does not seem probable that fermentation will occur 

 at very low temperatures, though no experiments have 

 been made. 



SUMMARY OF THEORIES 



The temperature coefficient of the rate of enzyme 

 action is normal. It is independent of that of enzyme 

 deterioration. 



The temperature coefficient of enzyme deterioration 

 is much higher than normal. 



The simultaneous action of these two processes brings 

 about the complex of symptoms briefly described as 

 '^Tammann principle," i.e., high initial rates of enzyme 

 action at very high temperatures rapidly decrease with time 

 and soon come to an end; slower rates at medium tem- 

 peratures, lasting longer, decrease more slowly, but give 



