82 
BACTERIAL METABOLISM 
vibrios and certain 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— glucose 
—as Theobald Smith^ showed some years ago. The toxin is only 
formed in sugar-free media. In this case again the glucose 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 carbohydrates. 
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 
following table summarizes briefly the salient features of the above 
discussion : 
Sugar-free media- Glucose media^ 
(nitrogen substance), (nitrogen substance), 
Chemical composition of bacteria. per cent. per cent. 
1. Pfeiffer bacillus 70.0 53.7 
Pneumo-bacillus 79.8 63.6 
Rhinoscleroma bacillus 76 . 2 62 . 1 
Sugar-free media. Sugar media. 
2. Diphtheria bacillus Powerful extracellular toxin No toxin produced; several 
of which on the average cubic centimeters of 
0.005 cc. kills guinea-pigs medium fails to kill guinea- 
pigs. 
3. B. tetani .... Powerful extracellular toxin No toxin produced. 
produced 
B. dysenterise (Shiga) Toxin present No toxin present. 
4. B. proteus Soluble, extracellular gela- No gelatinase formed. 
tinase formed 
Sp. cholerse Soluble, extracellular gela- No gelatinase formed, 
tinase formed. 
5. B. coli, B. proteus: 
Odor ... Foul None. 
Reaction Strongly alkaline Strongly acid. 
Products H2S, indol, phenols, am- H2, CO2, lactic acid, 
monia, etc. 
The observations recorded above, and the work of many investi- 
gators besides, show very definitely that bacteria utilize available 
carbohydrates for energy. The principal products arising from the 
decomposition of carbohydrates for energy are organic acids, chiefly 
lactic and acetic. The products of energy, furthermore, whether car- 
bohydrate or protein be utilized, are far greater in amount and reac- 
tivity than the waste from the structural phase of bacterial metabolism. 
1 Jour. Exper. Med., 1899, 4, 373. 
2 Nitrogenous constituents and reaction precisely the same in both sugar-free and 
sugar-containing media. The only difference is that the glucose medium contains 
1 per cent of glucose in addition. The organisms studied have, therefore, a choice 
between protein and sugar for catabolic purposes. See also Bacteria as Chemical Rea- 
gents, Kendall: Chem. and Metall. Eng., 1921, 24, 3. 
