BACTERIAL AUTOLYSIS 573 



ing from pll 7.0 to 9.0. A series of tests made upon E. prodig- 

 iosus in different hydrogen ion concentrations showed that, 

 although slow digestion took place at pH 4.0, the most rapid 

 digestion occurred at pH 7.0. Rosenow claimed that the en- 

 zyme action demonstrated by him in the pneumococcus is 

 favored in a +0.5 medium (phenolphthalcin titration). Dernby 

 (1917 and 1918), held, on the other hand, that a pH of 6.0 was 

 the most favorable for the autolysis of animal organs. 



The very slight changes which were observed in the Bad. 

 coli suspensions are of particular interest and soUcit further in- 

 quiry. In the first set of experiments very little enzymatic 

 action of any sort could be demonstrated, and then in 4 of 

 the suspensions only. In the second series (Charts 4 and 5) a 

 slight reduction in biuret (1 per cent to 6 per cent) and an 

 increase in amino acids were shown in every instance barring 

 experiment Via from which the possibihty of contamination 

 cannot be excluded. The chemical changes in these suspensions 

 were so slight as not to be indicated at all by the conductivity 

 tests. As the 2 heated controls showed almost the same change 

 as the unheated test samples the "autolysis" manifestations 

 become all the more insignificant. It is possible, however, that 

 the heating at 60° and 75°C. may not have been sufficient to 

 destroy the enzj-mes. Abbott and Gildersleeve (1903) found 

 that heating at 100° for fifteen to thirty minutes did not always 

 destroy certain bacterial enzymes. Meyer (1911) reported 

 that the proteases of Pseudomonas pyocyanea are little affected 

 by 15 minutes of exposure to 100°C. Wells and Corper (1912) 

 describe Upolytic enzjTnes in Mycobacterium tuberculosis which 

 are not entirely destroyed in thirty minutes at 100°. On the 

 other hand, Fermi (1894) found 55 to 70'' to be sufficient to 

 destroy the proteolytic enzjmies of bacteria. 



The possibihty of shght decreases in biuret and increases in 

 amino nitrogen from causes other than autolysis must not be 

 ignored. If, in the process of harvesting the bacterial growths 

 any appreciable amount of peptone with its various biuret-giv- 

 ing substabces should be removed from the agar medium, and 

 if the suspended organisms elaborate enzymes which act on any 



