ACID-PRODUCTION AND OTHER CHARACTERS OF 

 BACILLUS-COLI-LIKE BACTERIA FROM 

 FECES AND SEWAGE ' 



MAX LEVINE 



From the Department of Bacteriology of the Iowa State College, Ames 



The ability to decompose carbohydrates with the formation of 

 acid has long been recognized as one of the characteristics of Bacillus- 

 coli-like bacteria. This property of acid-production is the basis for 

 the isolation of B. coli on the Wurtz litmus-lactose-agar plate, and 

 also for the separation of B. coli from its relatives, B. typhosus and 

 B. paratyphosus, on the Conradi-Drigalski agar medium. The ability 

 to ferment various substances has been further utilized as a basis for 

 the subdivision of the colon-aerogenes group. In these studies on 

 classification, however, attention has been focused upon gas-formation 

 rather than upon acid-production. 



Browne, 1 in an extensive study of certain factors influencing acid- 

 production, points out that Bacillus-coli-like bacteria isolated from 

 oysters formed less acid from carbohydrates than those isolated from 

 human stools, and he attributed the difference to a loss of fermenting 

 power by the organisms in their passage through sewage from the 

 intestines to the oysters. Unfortunately, this investigator did not dif- 

 ferentiate the different types of organisms with which he was work- 

 ing. It is entirely probable that the smaller amount of acid observed 

 among the oyster strains was due to a greater incidence of some par- 

 ticular type or species of Bacillus-coli-like microorganism rather than 

 to a loss of fermenting power on the part of the intestinal forms. 

 [After the completion of the experimental work for this paper, an 

 article appeared by Clark and Lubs, 2 who pointed out that bovine fecal 

 strains of B. coli give rise to a higher H+- ion concentration in glu- 

 cose than do nonfecal (grain) strains.] 



The present investigation was undertaken to determine the fol- 

 lowing : 



1. Do Bacillus-coli-like organisms from different sources (par- 

 ticularly animal sources) give rise to different amounts of acid in the 



1 Jour. Infect. Dis., 1914, 15, p. 580. 

 3 Ibid., 1913, 17, p. 797. 



