THE BIOLOGICAL ACTIVITIES OF BACTERIA 47 



nature of the changes produced by them are true, these enzymes are 

 brought into close relationship to the proteolyzers, although a coagula- 

 tion can hardly be regarded as a true katabolic process. In milk where 

 the lab-action becomes evident by precipitation of casein, a strict dif- 

 ferentiation must be made between this coagulation and that brought 

 about by acids or alkalies. In the former case, casein is not only pre- 

 cipitated and converted into paracasein, but is actually changed so that 

 when redissolved it js no longer precipitated by lab.' 



Coagulating enzymes for milk proteids, blood, and other pro1;eid 

 solutions are produced by a large variety of bacteria. They hav6 been 

 observed in cultures of the cholera vibrio, B. prodigiosus, B. pyoCyaneus, 

 and several others.^ 



The lab enzymes are easily destroyed by temperatures of 70° C. and 

 over, and are very susceptible to excessive acidity or alkalinity. 



Fat-Splitting Enzymes (Lipase). — The fat-splitting powers of bac- 

 teria have been less studied than some of the other bacterial func- 

 tions and are correspondingly more obscure. It is known, nevertheless, 

 that the process is due to an enzyme and that it is probably hydrolytic 

 in nature. The following formula represents the simplest method in 

 which some of the molds and bacteria produce cleavage of fats into 

 glycerin and fatty acid. 



C3 H, (C„ H,„_, 0,)3 + 3H, O = C3 H, (OH3) + 3C„ H^^ O, 



Glycerin Fatty acid 



Some of the bacteria endowed with the power of producing lipase 

 are the spirillum of cholera, B. fluorescens liquefaciens, B. prodigiosus, 

 B. pyocyaneus, Staphylococcus pyogenes aureus, and some members of 

 the streptothrix family. The methods of investigating this function of 

 bacteria, originated by Ejkmann, ' consists in covering the bottom of a 

 Petri dish with tallow and pouring over this a thin layer of agar. Upon 

 this, the bacteria are planted. Any diffusion of lipase from the bacterial 

 colonies becomes evident by a formation of white, opaque spots in the 

 tallow. Carriere^ was able to demonstrate a fat-splitting ferment for the 

 tubercle bacillus. Apart from the importance of these enzymes in 

 nature for the destruction of fats, they are industrially important be- 



1 Oppenheimer, " Die Fermente u. ihre Wirkung," Leipzig, 1903. 

 ' Torini, Atti dei laborat. d. sanita, Rome, 1890. 

 a Ejkmann, Cent. f. Bakt., I, xxix, 1901. 

 *.Carritire, Comptes rend, de la soc. de biol., 53, 1901. 



