BACTERIAL NUTRITION 369 



THE UTILIZATION OF DIFFERENT BRANDS OF COMMERCIAL PEPTONE 



Laboratory culture media with few exceptions contain "pep- 

 tone" as their main nitrogenous ingredient. At the present time 

 various brands of this soluble protein and amino acid complex 

 are available in the open market. The most popular and best 

 known is the Witte product, which until quite recently was used 

 almost exclusively. Chemical analyses indicate that this prod- 

 uct has been incorrectly labelled. It has been more than thirty 

 years since Kiihne and Chittenden (1884) published their results 

 of the analysis of Witte's peptone. They found the prepara- 

 tion to be rich in albumose. The uniformity of this brand as to 

 composition has made it the universal standard for many years. 



At the present time several American brands of peptone are on 

 the market which bid fair to take the place of the Witte product, 

 but none of which have as yet attained the individual promi- 

 nence of the foreign brand. Chemical tests have shown that the 

 American brands differ to a considerable extent in their com- 

 position. 



Several methods are available for the study of '^ peptone" 

 utilization. A brief review will show, however, how far from 

 adequate, with few exceptions, these methods are, and how they 

 may readily lead to wrong conclusions. 



Abderhalden, Pincussohn and Walther (1910) employed 

 optical methods in their investigation of the action of certain 

 pathogens on peptone. Since the optical properties of the prod- 

 ucts of decomposition may have a neutralizing effect, the use 

 of such a test is open to error. The presence of meat extract 

 in a medium may also interfere. 



Crabill and Reed (1915) studied the biochemical activities of 

 microorganisms by pouring the test media into Petri dishes and 

 inoculating them with the bacteria under investigation. The 

 digestion and utilization of the medium could thus be deter- 

 mined by direct observation of the plates. Like the auxano- 

 graphic method of Eijkmann (1901), this is a qualitative pro- 

 cedure and consequently not suitable for the present problem. 



