82 



BACTERIAL METABOLISM 



from bacterial attack, and inasmuch as proteus bacilli prepare gelatin 

 for assimilation through the action of a proteolytic ferment, the 

 ferment is not elaborated by them under these conditions. A pre- 

 cisely similar restriction of the development of gelatin-liquefying 

 ferments by utilizable sugars occurs in cultures of cholera vibrios and 

 other bacteria which habitually liquefy this medium. In each instance 

 the same explanation holds true. 



4. Diphtheria bacilli do not produce their characteristic powerful 

 extracellular toxin in the presence of utilizable carbohydrate dex- 

 trose as Theobald Smith 1 showed several years ago. The toxin is 

 only formed in sugar-free media. In this case again the dextrose 

 shields the protein of culture media from attack by the diphtheria 

 bacillus, and consequently prevents the formation of toxin which 

 is apparently a true excretion produced incidental to the utilization 

 of protein for energy by these organisms. Similarly, tetanus and 

 Shiga bacilli fail to produce toxin in the presence of utilizable carbo- 

 hydrates. 



5. Colon and proteus bacilli produce considerable amounts of 

 indol in sugar-free media, but no indol in the same media to which 

 utilizable sugar has been added. Here again the carbohydrate is 

 attacked by these organisms in preference to the protein. The fol- 

 lowing table summarizes briefly the salient features of the above 

 discussion : 



Chemical composition of bacteria. 



1. Pfeiffer bacillus 



Pneumo bacillus 



Rhinoscleroma bacillus . 



Sugar- free media. 2 



Nitrogen substance, 



per cent. 



. . 70.0 



. . 79.8 



76.2 



Dextrose media. 2 



Nitrogen substance, 



per cent. 



53.7 

 63.6 

 62.1 



2. Diphtheria bacillus 



B. dysenteries (Shiga) 



4. B. proteus 



Sp. cholerse . 



5. B. coli, B. proteus: 



Odor .... 

 Reaction . 

 Products . 



Sugar-free media. 

 Powerful extracellular toxin 



of which on the average 



0.005 c.c. kills guinea-pigs. 

 Powerful extracellular toxin 



produced. 

 Toxin present. 

 Soluble, extracellular gela- 



tinase formed. 

 Soluble, extracellular gela- 



tinase formed. 



Foul. 



Strongly alkaline. 

 H2S, indol, phenols, am- 

 monia, etc. 



Sugar media. 



No toxin produced; several 

 cubic centimeters medium 

 fails to kill guinea-pigs. 



No toxin produced. 



No toxin present. 

 No gelatinase formed. 



No gelatinase formed. 



None. 



Strongly acid. 



H 2 , CO 2 , lactic acid. 



1 Tr. Assn. Am. Phys., 1896. 



2 Nitrogenous constituents and reaction precisely the same in both sugar-free and 

 sugar-containing media. The only difference is that the dextrose medium contains 

 1 per cent, of dextrose in addition. The organisms studied have, therefore, a choice 

 between protein and sugar for catabolic purposes. 



