THE BIOLOGICAL ACTIVITIES OF BACTERIA 49 



splitting enzymes are formed by many plants (malt) and by animal 

 organs (pancreas, saliva, liver). Among microorganisms amylase is 

 produced by many of the streptothrix group, by the spirilla of Asiatic 

 cholera and of Finkler-Prior, by B. anthracis, and many other bacteria. 

 A large number of the bacteria found in the soil, furthermore, have 

 been shown to produce amylases. By cultivating bacteria upon starch- 

 agar plates, amylase can be readily demonstrated by a clearing of the 

 medium immediately surrounding the colonies.' 



Since, of course, there are several varieties of starches, it follows that 

 the exact chemical action of amylase differs in individual cases. The 

 determination of the structural disintegration of starch by these fer- 

 ments is fraught with much difficulty, owing to the polymeric constitu- 

 tion of the starches. Primarily, however, a cleavage takes place into 

 a disaccharid such as maltose (hexobiose) , and the non-reducing sugars 

 and dextrin. Beyond this point, however, the further cleavages are 

 subject to much variation and are not entirely clear. The dextrins 

 upon further reduction yield eventually dextrose. 



Cellulose. — Cellulose is fermented by a limited number of bacteria, 

 most of them anaerobes. The chemical process by which this takes place 

 is but poorly understood.^ 



Gelase. — An agar-splitting ferment has been found by Gran.' 



Invertase. — ^The enzymes which hydrolyticaUy cause cleavage of 

 saccharose into dextrose and levulose are numerous. The chemical 

 process takes place according to the following formula: 



Ci2 H22 On -I- H2 = C|, H12 Oo + Cj HiaOu 

 Saccharose Dextrose Levulose 



Invertase is produced by many of the yeasts. It is one of the most 

 common of the enzymes produced by bacteria, and has been found in 

 cultures of B. megatherium, B. subtilis, pneumococcus, some strepto- 

 cocci, B. coli, and many others. Invertase is usually very susceptible to 

 heat, being destroyed by temperatures of 70° C. and over. A slightly 

 acid reaction of media abets the inverting action of these enzymes. 

 Strong acids and alkahes inhibit them. Inverting enzymes may be 

 precipitated out of solution by alcohol. Antiseptics even in weak con- 

 centrations will inhibit their action. 



1 Ejkmann, Cent. f. Bakt., xxix, 1901, and xxxv, 1904. 



2 Omelianski, Lafar's " Handb. d. teehn. Mykologie," Bd. iii, Chap. 9. 



3 Gran, B^rgens Museum Aarbog, 1902, Hft. I. 



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