60 VARIATIONS IN FERMENTING POWER [CH. v 



and Sherrick, 1911) failed to develop high and low acid 

 forming strains of streptococcus lacticus and Glenn (1911) 

 records a similar failure in the case of B. proteus. 



The significance op variations in the 

 "Sugar Reactions." 



A consideration of the action of bacteria on carbohydrates 

 and a comparison with the similar action of other (vegetable) 

 cells, such as yeast, justify certain conclusions. 



1. The splitting up of the carbohydrate is undoubtedly 

 efiFected through the agency of enzymes or " organised 

 ferments," the functions of which are inhibited or destroyed 

 by antiseptics, such as carbolic acid, sodium beuzoate, 

 monochlor-acetic acid. 



2. The fermentation of a particular carbohydrate is 

 dependent on the activity of a particidar ferment, so that the 

 power to ferment one carbohydrate is quite independent of 

 the power to ferment another. 



This is well illustrated by Goodman's experiments. The 

 two strains obtained by him from a culture of B. diphtherias, 

 one with greatly increased fermenting power towards dextrose 

 and the other with almost complete absence of such power, 

 both showed an augmentation of their power to ferment 

 saccharose and a diminution of their power to ferment 

 maltose. Penfold succeeded in modifying strains of B. coli, 

 B. enteritidis Oaertner and B. Grunthal by growing them 

 in the presence of a certain antiseptic, with the result that 

 they lost the power to produce gas from the sugars while 

 still retaining the power to produce gas from the corresponding 

 alcohols. 



3. The three stages in the process of fermentation, 

 namely the preliminary stage of " inversion " (in the case of 

 the di-saccharides) and the two final stages in which acid is 

 first formed and then split up into gases, are due to the 

 activity of three diflerent enzymes. Failure to produce gas 

 may be due to the absence or the inhibition of any one of 

 these three enzymes. Failure to produce acidity may be due 



