74 BACTERIAL METABOLISM 
According to Vaughan,* betaimidazoleethylamine is possibly the 
active poisonous principle of the protein molecule.- Recent investi- 
gations would suggest that its liberation in the intestinal tract as the 
result of bacterial decomposition of protein there and its absorption 
into the body may be associated with symptoms of considerable 
severity. B. welchii (the gas bacillus) may produce physiologically 
significant amounts of a histamine-like substance both in cultural media 
and the small intestine^ This substance, applied to the intestinal 
mucosa, causes histamine-like contracture provided the reaction is 
slightly alkaline. The substance is apparently only formed as a pro- 
duct of bacterial metabolism in the usual media containing utilizable 
carbohydrates. 
B. Reactions of Bacteria in Media Containing Both Utilizable 
Nitrogenous Substances (Protein and Their Derivatives) and Carbo- 
hydrates.— Carbohydrates contain no nitrogen; consequently pure 
carbohydrate solutions are not complete foods for bacteria. They are 
important chiefly as sources of energy to them. Generally speaking 
carbohydrates containing two, four, seven or eight carbon atoms are 
not readily fermentable by bacteria. Those containing six carbon 
atoms, particularly glucose, are most readily utilizable, those with three 
carbon atoms, generally speaking, somewhat less so. Bioses, con- 
taining tweh'e carbon atoms, and starches appear to be hydrolyzed to 
sugars containing six carbon atoms before they are finally oxidized. 
The final utilization of sugars for energy by bacteria varies accord- 
ing to the type of organism; the following qualitative reactions are 
illustrative of some of the general types of decomposition usually met 
with. 
The preliminary step in the utilization of sugars and carbohydrates 
of greater complexity than the hexoses, e. a., lactose, saccharose, and the 
starches, is believed to be usually a hydrolytic cleavage of the complex 
saccharine substance, thus: 
C12H22OU + H2O = CeHnOe + C6H12O6 
Lactose. Glucose. Galactose. 
The simpler molecules are then utilized for energy in one of several 
different ways, depending upon the organism. Thus alcoholic, lactic, 
acetic and butyric acid fermentations are well recognized. 
In the early days of fermentation study, before the complexities of 
the process were realized, and following Gay-Lussac,* doubtless, who 
made the first study of this important group of reactions, it was 
customary to class fermentations as pure alcoholic, lactic, acetic or 
butyric processes, in accordance with the equations: 
• Protein Split Products, 1913, p. 293. 
2 See Kendall, Alexander and Holmes: Jour. Infec. Dis., 1927, 41, 137. Kendall 
and Varney: Ibid., 1927, 41, 156. 
3 Kendall and Schmitt: Ibid., 1926, 39, 250. 
' Ann. Chem." et Phvs., ISIO. 76. 245. 
