XI. B, 4 



Wade: Carbohydrate Fermentation 



171 



From this summary may be drawn definite conclusions as to 

 the fermentation activities of B. pestis in the media used. 



LIMITATION OF ACID TOLERANCE 



In the 0.5 per cent bouillon series (Table III) the cultures, 

 irrespective of the nature of the sugar, the extent of growth, 

 or the primary acidity, showed a maximal acidity of about 2.5 

 per cent, which reaction was obtained with several sugars. This 

 indicates a rather remarkably constant limit of acid tolerance 

 for the various strains. 



The influence of concentration of carbohydrate on end reac- 

 tion. — That increase of sugar, up to a certain point at least and 

 under certain conditions, causes an increase in the rapidity or 

 the degree of the reaction is axiomatic. The effect of varia- 

 tion in amount depends, to a certain extent at least, upon the 

 activity of the organism against the particular sugars used. For 

 instance, 0.5 per cent dextrose serum-water was as completely 

 acidified as was the 1 per cent medium. On the other hand, 

 1.5 or 2 per cent maltose or arabinose serum-waters would 

 probably have reacted more strongly than did those of 1 per 

 cent concentration to be shown in Table VI. In order to de- 

 monstrate whether widely different concentrations of sugar would 

 have any influence on the final acidity, a series of peptone-water 

 cultures was made, dextrose and mannite being the sugars used. 

 Three strains of organisms with somewhat different fermenta- 

 tion activities were selected. The titration results appear in 

 Table V. 



Table V. — Final acidity produced in peptone waters containing different 



amounts of carbohydrates. 





Strain— 



Control 

 (average 

 of two). 



B. 



G. 



L 



Dextrose: 



2.00 

 2.16 

 2.16 

 2.24 

 2.16 



1.76 



1.68 



1.8 



1.75 



1.84 



1.72 

 1.80 

 1.92 

 1.84 

 2.00 



1.32 

 1.32 

 1.32 

 1.40 

 1.32 



1.92 

 1.88 

 2.04 

 1.92 

 2.12 



1.44 



1.48 

 1.44 

 1.00 

 1.48 



0.68 

 0.76 

 0.84 

 0.88 

 1.00 



0.64 

 0.60 

 0.62 

 0.44 

 0.48 



1.0 per cent , 







2.5 per cent 



Mannite: 



0. 5 per cent 



1.0 per cent 







2.6 percent 





