PROTEOLYTIC ENZYMES OF BACTERIA 97 



gelatine in cultures which have been growing for a 

 considerable time. These form intracellular enzymes 

 which diffuse very slowly, if at all, from normal living 

 cells, but escape readily from unhealthy involution forms 

 or cells which are dead. 



The enzymes manufactured by bacteria chiefly 

 resemble trypsin. Like the latter, their action is gen- 

 erally most energetic in neutral or alkaline media, and 

 the majority of them break down proteins into peptones, 

 amino - acids, ammonia, and other basic substances. 

 They all peptonise and liquefy gelatine, some of them 

 even when the medium is faintly acid. Emmerling and 

 Reiser investigated the action of Bact. fluorescens lique- 

 faciens on gelatine, and found a peptone present in the 

 " liquefied " medium along with methylamine, trimethyl- 

 amine, choline, and betaine ; ammonia was also set free. 

 Streptococcus longus cultivated under anaerobic con- 

 ditions in a medium containing fibrin produced tyrosine, 

 leucine, trymethylamine, methylamine, ammonia, and 

 some pyridine bases, as well as acetic, propionic, butyric, 

 and succinic acids. 



The production of enzymes by bacteria and the 

 amount obtained depend upon the kind of organism, 

 the composition of the nutrient medium, temperature, 

 and other factors. A few species, such as Bs. subtilis, 

 Bact. prodigiosum, and Bact. pyocyaneum, can form them 

 in nutrient solutions devoid of organic nitrogenous com- 

 pounds, but the majority only give rise to enzymes 

 when grown in meat juice, broth, milk, and other media 

 containing proteins. Most carbohydrates hinder the 

 formation of enzymes more or less completely without 

 checking the growth and development of the bacteria. 

 Some of the sugars, such as glucose, may inhibit their 

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