286 KAN-ICHIRO MORISHIMA 



subcultures of these strains from xylose broth to xylose broth 

 ten strains (not Lieutenant Colwell's strains) became xylose 

 fermenters in twenty-four hours (or somewhat later) after a 

 few transfers. 



CROSS FERMENTATION OF BACTERIA IN DIFFERENT SUGARS 



It might be supposed that a single enzyme produced by 

 bacteria when cultivated in sugar media, especially those closely 

 related, such as xylose and arabuiose, might ferment more than 

 one sugar. To test this supposition, 6 xylose fermenters, 7 

 arabinose fermenters, 9 dulcitol fermenters (all fermenting in 

 twenty-four hours) and 6 xylose slow fermenters, 6 arabinose 

 slow fermenters and 7 dulcitol fermenters were inoculated into 

 three sets of sugar media. We could not find any evidence of 

 cross fermentation. After thirty-five days' incubation the fer- 

 menter of a given sugar still continued to ferment the same 

 sugar, and no other. Therefore, the enzymes produced by 

 bacteria are, as assumed by many workers, specific for each 

 sugar. 



DURATION OF THE FERMENTING POWER 



Some strains, which had been artificially induced to ferment 

 certain sugars, maintained their fermenting power after three 

 or four months, or even half a year, although few transplanta- 

 tions were made from one fresh medium to another, this being 

 done in some cases to media containing no sugar. Other strains, 

 however, lost their fermenting power quickly, after only one or 

 two transplantations. Dulcitol fermenters especially are apt 

 to be changeable. Our records show two strains which at first 

 fermented dulcitol in twenty-four hours. Later one of them 

 fermented dulcitol only after four days and the other after 

 twenty-one days. Similarly a strain which at first fermented 

 arabuiose in twenty-four hours, later required six days for the 

 fermentation of this sugar. 



