BACTERIAL NUTRITION 



371 



The first part of this investigation involved a study of the 

 utihzation of Witte's peptone by different types of bacteria. 

 In later experiments other brands of peptone were investigated. 

 The test media were, as a rule, simple nutrient broths such as 

 are used for routine work in the laboratory. These solutions 

 were always transferred to large test tubes in amounts of 10 cc. 

 The water lost by evaporation was accurately replaced after the 

 incubation period, and preliminary to the testing. 



Witte's peptone 



In tables 1, 2 and 3 are recorded the results of the experiments 

 on the utihzation of Witte's peptone. It will be seen that each 

 of the organisms studied is capable of reducing the amount of 

 biuret-giving substances, though for the gelatin-non-liquefying 

 organisms at least a week's incubation is required to show any 



TABLE 1 

 Showing the utilization of Witte's peptone 



ORGANISMS 



Control 



Subtilis group, average 3 members. 



B. prodigiosus 



P. vulgaris, average 2 strains 



P. mirabilis 



Staph, aureus, 3 strains 



Staph, albus 



B. 

 B. 

 B. 

 B. 

 B 



cloacae 



typhi 



paratyphi A 



coli, average 4 strains 



diphtheriae, average 2 strains. 



12.0 

 3.3 

 4.0 

 5.0 

 4.0 

 2.0 



4.0 

 4.0 

 2.0 

 0.0 

 1.0 

 5.0 



SORENSEN 

 TEST 



18.0 

 49.0 

 42.0 

 52.0 

 62.0 

 47.0 

 52.0 

 52.0 

 32.0 

 32.0 

 43.0 

 37.0 



BIURET 



TEST 



1.0 



0.0 



0.0 



0.0 



0.30 



0.55 



0.50 



0.40 



0.65 



0.70 



0.75 



0.60 



Medimn employed: 1 per cent peptone, 0.25 per cent Liebig's beef extract, 

 and 0.5 per cent NaCl. Incubation at 30°C. for three weeks. 



Note: When results with similar organisms do not differ widely they are 

 averaged for the sake of brevity. 



The standard biuret figure for the control is given as 1.0 in all of the tables. 

 According to this system a reduction of 40 per cent in the amount of biuret- 

 giving substances is recorded as 0.60, and one of 100 per cent as 0.0. 



Reaction of culture fluids is given in the first column. The results are stated 

 in terms of n/20 acid or alkali. The italic figures denote alkaline reaction. 



