QUALITATIVE CATABOLIC REACTIONS OF BACTERIA 73 



V. QUALITATIVE CATABOLIC REACTIONS OF BACTERIA. 



The chemical changes observed in cultures of ordinary bacteria are 

 chiefly those associated with the breakdown of organic substances for 

 energy they are reactions of the catabolic phase of bacterial meta- 

 bolism. It should be again emphasized that the energy reactions the 

 catabolic reactions are those which are most profoundly influenced 

 by the composition of the nutritive substrate upon which the organisms 

 are grown. 



A. Reactions of Bacteria in Media Containing Only Nitrogenous 

 Substances (Proteins or Protein Derivatives) Which are Utilized 

 for the Energy Requirements of Bacteria. Proteins are composed 

 of amino-acids, of which some seventeen are recognized. Bacteria 

 which decompose protein appear to act upon these amino-acids in the 

 last analysis, and several types of reaction are recognized at the present 

 time. Each kind of organism utilizes protein or protein derivatives 

 somewhat differently and characteristically, but in general one or more 

 of the following types of reactions are involved either successively or 

 simultaneously in the catabolism of these substances. The reactions 

 follow i 1 



1 . R.CH 2 .CHNH 2 .COOH + H 2 = R.CH 2 .CH 2 .COQH 4- NH* Re- 

 ductive deaminization of amino-acid to fatty acid with the same 

 number of carbon atoms. 



2. R.CH 2 .CHNH 2 .COOH + H 2 O = R.CH 2 .CHOH.COOH + NH 3v 

 Hydrolytic deaminization of amino-acid to oxy-acid with the same 

 number of carbon atoms. 



3. R.CH 2 .CHNH 2 .COOH + O 2 = R.CH 2 .CO.COOH + NH 3 . Oxi- 

 dative deaminization of amino-acid to keto-acid with same number of 

 carbon atoms. 



4. R.CH 2 .CHNH 2 .COOH-R.CH 2 .CH 2 .HN 2 + CO 2 . Carooxylic 

 decomposition of amino-acid to amine with one less carbon atom. 



5. R.CH 2 .CH 2 .COOH -* R.CH 2 .CH 3 . + CO 2 . Carboxylic decom- 

 position of fatty acid. 



6. R.CH 2 .CH 2 .COOH + 3O = CH 2 .COOH + CO 2 + H 2 O. Carbo- 

 xylic decomposition with the formation of a fatty acid with one less 

 carbon atom. 



A few illustrations will indicate the nature of these changes in amino- 

 acids with the production of certain substances of clinical interest : 

 1. Formation of indol from tryptophan. Indol is a substance pro- 



* See Kruse, Allgem. Mikrobiol., 505-536, for literature. 



