14 



BIILLETIIS]" 782, U. S. DEPAETMEjSTT OF AGRICULTURE. 



tion. It will be noted that in medium A, 25 cultures showed a 

 distinct fermentation of dextrose, the hydrogen-ion concentration 

 in most cases going from P^ 6.9 (control) to P^ 4.5, a few cultures 

 reached about Pg. 6.0, and only 19 cultures changed from Pg 6.9 to 

 Pjj 6.5 or lower. These cultures it was believed fermented dextrose 

 but were called plus or minus. 



Table 5.- 



-Res-ults of fermentation of dextrose in synthetic media tcith different buffer 

 contents. 



Culture 

 No. 



Medium A. Medium B 



Dex- 

 trose 



fer- 

 men- 



ta- 

 tion. 



Dex- 

 trose 



fer- 

 men- 



ta- 

 tion. 



Medium C. 



Dex- 

 trose 



fer- 

 men- 



ta- 

 tion. 



Sum- 

 mary 



of 

 dex- 

 trose 



fer- 

 men- 



ta- 

 tion. 



Medium A. 



Culture 

 No. 



Dex- 

 trose 



fer- 

 men- 



ta- 

 tion. 



Medium B. Medium C. 



Dex- 

 trose 



fer- 

 men- 



ta- 

 tion. 



J'h. 



Dex- 

 trose 



fer- 

 men- 



ta- 

 tion. 



Sum- 

 marj- 



of 

 dex- 

 trose 

 fer- 

 men- 



ta- 

 tion. 



Control . . 



10 

 12 

 31 

 49 

 59 



60 

 61 

 62 

 66 

 72 



73 

 101 

 102 

 103 

 104 



105 

 106 

 107 

 108 

 111 



112 

 113 

 114 

 116 

 117 



118 

 119 

 120 

 121 

 122 



123 

 124 

 125 



126 

 128 



4.5 



+ 



5.5 



4.5 



+ 



5.4 



5.7 



+ 



6.2 



4.5 



+ 



5.4 



6.9 





7.2 



6.9 



_ 



7.2 



6.9 



_ 



7.2 



6.9 



_ 



7.2 



6.9 



_ 



7.2 



5.8 



+ 



6.2 



6.9 



_ 



7.2 



6.6 



± 



7.2 



6.6 



± 



7.2 



6.9 



— 



7.2 



6.7 



± 



7.2 



6.6 



± 



7.2 



6.9 





7.2 



4.5 



+ 



5.5 



6.5 



± 



7.2 



6.9 



- 



7.2 



4.5 



4- 



6.0 



4.5 



4- 



5.5 



6.9 





7.2 



6.7 



± 



7.2 



6.6 



± 



7.2 



6.9 



_ * 



7.2 



6.7 



± 



7.2 



4.5 



+ 



5.5 



4.5 



+ 



6.2 



6.9 





7.2 



4.5 



+ 



4.5 



6.7 



± 



7.2 



6.5 



± 



7.2 



6.6 



± 



7.2 



6.9 





7.2 



4.8 



5.9 



Control.. 



130 

 131 

 132 



133 

 134 



135 

 136 

 137 

 138 

 139 



140 

 141 

 142 

 143 



144 



145 

 146 

 147 

 303 

 309 



314 

 317 

 319 

 321 

 322 



325 

 326 

 340 

 353 

 354 



356 

 361 

 362 



6.9 



6.9 



6.6 

 6.6 



4.5 

 4.5 



6.7 

 6.5 

 4.5 

 6.6 

 6.9 



6.5 

 4.5 

 6.9 

 4.5 

 6.6 



6.9 

 6.6 

 6.9 

 6.9 

 6.9 



5.6 

 6.9 

 6.2 

 6.2 

 6.2 



6.2 

 6.2 

 6.9 

 6.9 

 6.9 



6.2 

 6.0 

 0.3 



7.2 

 7.2 

 7.2 

 6.2 

 6.2 



7.2 

 7.2 

 5.0 

 7.2 

 7.2 



7.2 

 6.0 



7.2 

 5.4 

 7.2 



7.2 

 7.2 

 7.2 

 7.2 

 7.2 



6.3 

 7.2 

 6.5 

 6.3 

 6.4 



6.5 

 6.5 

 7.2 

 7.2 

 7.2 



6.5 

 6.4 

 6.2 



Medium B, while having less buffer than medium A, contained 

 also less dextrose, and in it only 25 cultures showed a positive 

 fermentation. Medium C was then tried and it contained the same 

 amount of dextrose as medium A but half the sodium-ammonium 

 phosphate. As this medium had considerably less buffer than 

 medium A, it was expected that the cultures showing only a slight 

 change in Ph in medium A would show a much larger change in 

 medium C. This was found to be the case, as is shown in the table. 



