392 M. R. SMIRNOW 



FERMENTATION OF SUGARS 



The results obtained with these substances on B. coli with 

 reference to variations in sugar fermentations can be best seen 

 in the accompanying tables. The most striking changes here 

 also were seen in those organisms exposed to glucose and phenol. 

 The former completely inhibited both acid and gas formation 

 in all the sugars tested in three different strains. In two others, 

 glucose varied the amount of acid and gas formation, with an 

 occasional complete inhibition in some of the sugars. Phenol 

 inhibited these fermentations in all of the sugars in only one 

 strain, and in four others, diminished this reaction to the point 

 of inhibition at times only and in different carbohydrates. Sodium 

 chloride and sodium sulphate had less effect than did phenol, 

 giving usually slight variations in amount of acid or gas pro- 

 duced with an occasional inhibition. 



Inhibition of all the sugar fermentations in any one experi- 

 ment was almost always accompanied by inhibition of the 

 usual changes in milk, the characteristic growth on potato, and 

 the formation of indol. In other words, the most typical varia- 

 tions were those in which all acid or ferment production was 

 inhibited. 



VARIATIONS IN INDOL PRODUCTION 



The production of indol is held by many bacteriologists to 

 be as important a biological characteristic of B. coli as its fer- 

 mentations of the sugars, and is even thought to be of greater 

 importance in its differentiation. This reaction, however, even 

 under normal conditions varies considerably in its quantity and 

 time of appearance with most strains, and at times requires 

 more deUcate tests than the usual Salkowski method for its 

 determination. 



In the experiments here reported it appears that of the varia- 

 tions induced in B. coli that of indol production is the first to 

 take place, often disappearing in the third or fourth culture in 

 glucose broth. This does not hold however when the bacteria 

 are grown in the other media, as evidenced below. 



