374 



NATHAN BERMAN AND LEO F. RETTGER 



A marked difference in the degree of utilization of the protein 

 material in these different products was observed. The Diges- 

 tive Ferments Company peptone (Difco) showed approximately 

 the same degree of resistance to bacterial attack by the gelatin- 

 non-liquefying bacteria and the intermediate group of organisms 

 (Staph, aureus and Staph, albus and B. cloacae, as the Witte. On 

 the other hand, "aminoids" and the Eimer and Amend product 

 seem to have undergone the greatest amount of degradation of 

 protein or the more complex biuret-giving substances in the 

 process of manufacture, according to the biuret reduction figures. 

 The ''aminoids"^ brand was reduced by B. coli, B. typhi and 



TABLE 4 

 Showing the utilization of Digestive Ferments Company peptone 



ORQANISMS 



Control 



Subtilis group, 3 strains 



B. prodigiosus 



P. vulgaris, 3 strains 



Staph, aureus and albus, 4 strains... 

 B. typhi and B. paratyphi A and B. 



B. coli, 4 strains 



B. diphtheriae, no. 8 



16.0 

 7.5 

 8.0 

 5.0 

 1.5 

 2.0 

 1.5 

 8.0 



SORENSEN 

 TEST 



32.0 

 64.0 

 62.0 

 50.0 

 50.0 

 44.0 

 44.0 

 42.0 



BIURET TEST 



1.0 



0.0 



0.0 



0.2 



0.77 



0.73 



0.7 



0.75 



Mediiun: 0.5 per cent peptone, 0.25 per cent beef extract, 0.5 per cent NaCl. 

 Incubation at 30°C. for three weeks. 



B. paratyphi from a biuret value of 1.0 to 0.3 and 0.4, and by 

 B. diphtheriae to 0.1 and 0.3, as compared to 0.4 and 0.5 for the 

 Eimer and Amend product. The remaining brands occupy an 

 intermediate position between these two extremes. 



The experimental evidence at hand indicates that most of the 

 nitrogen present in commercial peptones is in a form too complex 

 to be utilized directly. B. subtilis, B. .prodigiosus, P. vulgaris 

 and the closely related forms are able to digest the different 

 peptones completely, whereas those organisms which are not 



1 Two brands of "aminoids" have been used in this laboratory. The one 

 contains an appreciable amount of biuret-giving substances, while the other is 

 biuret-free. The former was employed in these experiments. 



