ENERGY SUPPLY OF THE CELL 



135 



At — 1°C., all strains decreased slowly in plate count 

 (see p. 224). From the first period of observation, the 

 temperature coefficients Qio were found: 



Between — l^C. and 



Between 5.5°C, and 

 10°C. 



Strept. cremoris 23 

 Strept. cremoris 18 

 Strept. lactis 



2.7 



6.1 



The experiment was discontinued on account of a break- 

 down of the lowest incubator. The few experiments 

 are not sufficient to draw conclusions regarding the 

 cause of the minimum temperature. They suffice 

 entirely, however, to demonstrate that fermentation 

 will take place at temperatures considerably below the 

 minimum for growth. Whether these results can be 

 generalized so far as to state that fermentation takes 

 place at all temperatures until the freezing of the 

 medium, seems very doubtful. 



An explanation may perhaps develop from Crozier's (1924) 

 analysis of the temperature relations of biological oxidations. He 

 demonstrated graphically, by plotting rates against the reciprocal 

 of absolute temperature (see p. 121) that at different points, different 

 processes may dominate the rate of life functions. The critical 

 thermal increment fj, = 2A for biological oxidations is frequently 

 11,500 above 15°C., and 16,100 or 16,700 at the lower temperatures. 

 The reduction of methylene blue by Bad. coli in the presence of 

 succinic acid shows )u = 16,700 (Quastel and Whetham, 1924). 



For the alcoholic fermentation, the ju-values are quite different. 

 There is apparently no oxidation connected with alcoholic fermenta- 

 tion. Slator's data, according to Crozier's computation, show /x = 

 12,250 above 21°C., and M = 22,200 below 2rC. which means a higher 

 temperature coefficient at the lower temperature. Why this is 

 the case, and why 21°C. is the critical temperature, is still unknown. 



