BACTERIAL ENZYMES 109 



Gram's method of staining depends on the formation of an 

 iodin-pararosanilin-proteid compound which is not easily disso- 

 ciated by water in the case of bacteria that stain by this method, 

 and which is readily dissociated and dissolved out in the case 

 of bacteria that do not retain the stain. Only pararosanilin 

 dyes (gentian violet, methyl violet, victoria blue) form such 

 combinations, the rosanilin dyes (fuchsin, methylene-blue) not 

 being suitable. 



The acid-fast bacilli (leprosy, tubercle, and allied forms) owe 

 their characteristic resistance to both staining and destaining 

 processes, to their high fat content, which modifies greatly the 

 penetration by stains and reagents. It is said that organisms 

 not ordinarily acid-fast may be made so by increasing their fat 

 contents by growing them on fat-rich media. According to 

 Bulloch and Macleod 1 the acid-fastness of the tubercle bacillus 

 depends not on the ordinary ether-soluble fats, but on a high 

 molecular alcohol of undetermined composition, soluble in boil- 

 ing absolute alcohol. 



BACTERIAL ENZYMES 



The metabolic processes of bacteria seem to be closely depend- 

 ent upon enzyme action, just as with higher cells. 2 Liquefaction 

 of gelatin is a familiar example of the enzyme action of bacteria ; 

 and since the filtered cultures of liquefactive bacteria are also 

 capable of digesting gelatin, the enzymes are evidently excreted 

 from the cells. Dead bacteria, killed by thymol or by other 

 antiseptics that do not destroy proteolytic enzymes, will also 

 digest gelatin. Numerous investigations have established the 

 wide-spread occurrence of many soluble enzymes both in bacteria 



1 Loe. cit. 



2 One must distinguish between "enzymes" and "ferments," although since 

 most of the characteristic fermentative actions of yeast and other cells have 

 been found to be produced by intracellular enzymes, the distinction is not 

 always easy to make. Gotschlieh (Kolle and Wassermann's Handbuch, vol. i, 

 p. 104) would distinguish them as follows: "Fermentation is a direct func- 

 tion of the living protoplasm, and serves as its source of energy." " Enzyme 

 action is not directly dependent on the living protoplasm, and does not serve 

 the organism as a source of energy." Exception can readily be taken to these 

 definitions, however, for the latest indications are that nearly all of the separate 

 processes that go to make up the process of fermentation are enzyme processes. 

 Fermentation may, therefore, be looked upon as the action of living organisms, 

 being the sum of the action of the enzymes of the organisms together with 

 certain other chemical processes not brought about by enzymes. In general, 

 the distinction is made chiefly on the ground that we can stop fermentative 

 processes by means of certain antiseptics that kill the causative organisms, but 

 which do not greatly impair the enzymes. Even this distinction is more 

 quantitative than qualitative, for very dilute solutions of enzymes are nearly 

 as susceptible to antiseptics as are bacteria (Kaufmann, Zeit. physiol. Chem., 

 1903 (39), 434). 



