390 THE COLI-CLOAC.E— PROTEUS GROUP 
saccharose is not decomposed by the strains of the colon bacillus 
commonly found in the intestinal tract. Occasionally a saccharose- 
fermenting strain is encountered in the feces. ^ 
The reactions of the colon bacillus in milk are variable; typical 
strains produce enough acid from the fermentation of the lactose to 
cause an acid coagulation in from one to three days at 37° C. Neu- 
tralization of the acid by alkali redissolves the coagulum and the 
medium resumes its normal appearance. Occasional strains do not 
cause coagulation even after boiling the milk.^ Gas is not produced in 
appreciable amounts in milk by B. coli, and the organism leaves the 
milk proteins practically intact even after prolonged incubation— 
the carbohydrate constituents alone are acted upon.^ The addition 
of peptone to milk, however, leads to the formation of gas.^ Coagula- 
tion does not as a general rule occur in litmus milk, but boiling the 
medium usually causes rapid clotting. The ordinary litmus of com- 
FiG. 53.— Bacillus coli, broth culture. 
merce contains considerable amounts of calcium carbonate. This may 
neutralize some of the acid products of fermentation, reducing the 
acidity below the coagulation point. This explanation does not 
account for the same phenomenon in milk colored with pure litmus 
or azolitmin. Gelatin is not liquefied by B. coli. Nitrates are reduced 
to nitrites. Occasional strains are strongly hemolytic. 
(6) Enzymes. ~'&o\nh\e proteolytic and lipolytic enzymes have not 
been detected in cultures of B. coli. Buxton^ has demonstrated 
both a maltase and a lactase in maltose and lactose cultures of the 
organism respectively. '^ The investigations of Franzen and Steppuhn^ 
1 Theobald Smith: Am. Jour. Med. Sci., 1895, 110, 283. 
- Ibid., Fermentation Tube, p. 201. 
3 Kendall, Day and Walker: Jour. Am. Chem. Soc, 1914, 36, 1945. 
■• Ishikawa: Jour. Infec. Dis., 1927, 41, 238. ^ Am. Med., 1903, 6, 137. 
° See Harden and Zilva: The Reducing Enzyme of B. coli, Biochem. Jour., 1915, 9, 
379. 
' Ztschr. f. physiol. Chem., 1912, 77, 129, 
