386 PHYSIOLOGY OF BACTERIA 



Since the death rate by oxidation is known for dry Micrococci 

 (p. 308) and the death rate by heat has also been determined, (p. 

 320), the rates from the two causes can be calculated for all tem- 

 peratures, assuming the temperature coefficient for oxidation to be 

 3.16, and that of hydrolysis to be 28.9. Table 127 gives these. 



While these calculations have no sound basis at all, and are 

 entirely speculative, they illustrate the possibility that a bacterium 

 in the same medium might die at 20°C. from oxidation (death by 

 oxidation being ten times as rapid as by hydrolysis), while at 40°C., 

 it may die from hydrolysis (death from hydrolysis here being six 

 to twenty times as rapid as that by oxidation). 



(e) SUMMARY OF FACTS 



Bacteria and yeasts die if food is lacking. The 

 decrease of living cells is more rapid in water than in 

 balanced salt solutions. In well balanced solutions, 

 which are specific for each species, the bacteria may show 

 hardly any decrease of viable cells for three to four days. 

 If death is accelerated in water, it seems safe to assume 

 that they do not die from starvation, but from other 

 causes. One of these has been found to be cold-shock. 

 The greater viability, if the water used for making salt 

 solutions is distilled twice, suggests the presence of traces 

 of toxic substances in the distilled water. These are 

 counteracted by peptone or meat extract, but not by 

 sugar or balanced salt solutions. 



Most of the experiments supposed to be starvation 

 experiments really present death by other causes. The 

 true death by starvation must show a survivor curve 

 starting parallel to the abscissa, and must show an 

 increasing death rate. 



In the absence of oxygen, starving cells of Bad. coli 

 die more slowly, while starving cells of Bad. typhosum 

 die more rapidly. 



Bad. coli can survive in water very much longer than 

 most other bacteria. 



