VITAL ACTIVITIES OF BACTERIA 147 



C 6 H 12 6 = 2C 2 H 6 + 2C0 2 

 Grape-sugar 2 alcohol 2 carbon dioxide. 



Or, C H 12 6 = 2C 3 H 6 3 



Grape-sugar 2 lactic acid 



Or, C 6 H 12 3C 2 H 4 2 



Grape-sugar 3 acetic acid 



Oxidizing fermentation, as in the production of acetic 

 acid from alcohol, is less commonly encountered. Here the 

 energy is acquired not by the decomposition but by the oxi- 

 dation of the alcohol. 



The proteolytic ferments, which are somewhat analogous 

 to trypsin being capable of changing albuminous bodies 

 into soluble and diffusible substances are very widely dis- 

 tributed. The liquefaction of gelatin, which is chemically 

 allied to albumin, is due to the presence of a proteolytic fer- 

 ment or trypsin. The production of proteolytic ferments by 

 different cultures of the same varieties of bacteria varies con- 

 siderably. Even among the freely liquefying bacteria, such 

 as the cholera spirillum and M. pyogenes, poorly liquefying 

 varieties have been found repeatedly. These observations 

 have detracted considerably from the value of the property 

 of liquefying gelatin as a positive means of identifying bac- 

 teria. Nearly all conditions which are unfavorable to the 

 growth of bacteria seem to interfere more or less with their 

 liquefying power. 



Certain bitter tasting products of decomposition are 

 formed by liquefying bacteria in media containing proteid, 

 as, for example, in milk. Certain bacteria also produce dias- 

 tatic ferments which convert starch into sugar. 



Inverting ferments are of very frequent occurrence. 

 Among bacteria these ferments withstand a temperature of 

 100 C. for more than an hour. 



Rennet-like ferments or substances having the power of 

 coagulating milk with neutral reaction, independent of acids, 

 are occasionally found among bacteria. B. prodigiosus, for 

 instance, in from one to two days coagulates to a solid mass 



