CLASSIFICATION OF ACIDURIC BACTERIA 415 



Although the failure of B. acidophil-aerogenes first, to produce 

 gas in a given carbohydrate and then to ferment it entirely, is 

 suggestive in view of the numerical relationships of the differ- 

 ent strains, we are not at liberty to conclude absolutely that 

 such failures are instances of suppressed function and not real 

 cultural differences. The cultural differences shown in the 

 table are those found in freshly isolated strains and were not 

 brought about intentionally. Prolonged artificial cultivation 

 or other means might bring about such alterations, but until 

 these are observed actually to occur it is better to assume that 

 these differences are absolute and classify the organisms 

 accordingly. 



BACILLUS BULGARICUS 



In table 3 are the organisms that correspond to the Bacillus 

 bulgaricus. Some of these strains were obtained from the 

 American Museum of Natural History while others were from 

 commercial preparations of one kind or another. One strain 

 was isolated from the saliva of a man, who, as far as could be 

 determined, had not recently taken this bacillus. Two strains 

 came from grade B. milk and made it appear that B, bulgaricus, 

 in common with other lactic acid bacteria is able to survive the 

 temperature of pasteurization. Experiments made to test the 

 heat resisting properties of B. acidophilus, B. acidophil-aerogenes 

 and B. hidgaricus showed them to be capable, in twenty-four 

 hour broth culture, of surviving moist heat for one hour at 65°C. 



Examination of the table shows that there is a very fair degree 

 of uniformity between the various members of this group, both 

 as regards colony formation and action on milk, fifteen out of 

 seventeen strains showing close resemblance in this respect. 

 Cultural tests permit their separation into four types. White 

 and Avery (1910) recognized two types of B. bulgaricus. Their 

 type A consisted of bacilli that were rapid fermenters, forming 

 inactive lactic acid and exhibiting no granules, while type B 

 showed granules, was less active and formed levo-rotary acid. 

 These characteristics are not exclusive properties of B. bulgaricus. 



