88 BACTERIAL METABOLISM PRODUCTS 



and generally, but not always, sulphur, and sometimes phosphorus. 

 The proportion of these constituents is approximately C, 50-55 

 per cent.; H, 6-7.3 per cent.; 0, 19-24 per cent.; N, 15-19 per cent. 

 S, when present, 0.3-2.5 per cent.; and P, 0.4-0.8 per cent. They are 

 substances which in the main consist of combinations of oc amino- 

 acids or their derivatives. The decomposition products of proteins 

 include proteoses, peptones, peptides, carbon dioxid, ammonia, 

 hydrogen sulphid and amino-acids. The amino-acids constitute a 

 long list of important substances which contain nuclei belonging 

 either to the aliphatic, carbocylic, or heterocyclic series. The 

 present list includes glycocoll (glycin) alanin, serin, phenylalanin, 

 tyrosein, cystin, tryptophan, histidin, valin, argin, leucin, isoleucin, 

 lysin, aspartic acid, glutamic acid, prolin, oxyprolin, and norleucin. 

 Many, especially of the saprophytic bacteria which occur in 

 the soil, have the power of breaking down native proteins with the 

 formation of the various amino-acids. Undoubtedly the complex 

 organic compounds which are being isolated from the soil, and 

 which are assumed by some to play such an important part in soil 

 fertility, have just such an origin. But it is usually the case in all 

 media that the bacterial catabolism carry the substance much farther 

 than the amino-acid. The extent of this change varies greatly with 

 the species of microorganisms and the conditions under which they 

 are acting. Kendall summarizes some of the further changes which 

 may occur as follows: 



1. The reductive deaminization of amino-acids to fatty acids with 

 the same number of carbon atoms. 



RCH 2 CHNH 2 COOH + H 2 = RCH 2 CH 2 COOH + NH 3 



2. Hydrolytic deaminization of amino-acids to oxyacids with the 

 same number of carbon atoms. 



R GHz CHNHz COOH + H 2 O = R GHz CHOH COOH + NH 3 



3. Oxidative deaminization of amino-acids to keto-acids with the 

 same number of carbon atoms. 



R GHz CHNHz COOH + O 2 = R GHz CO COOH + NH 3 



The above reactions may be taken as types of the last stages of 

 the reactions brought about by the ammonifying bacteria within 

 the soil. 



4. Carboxylic decomposition of amino-acid to amine with one 

 less carbon atom. 



R CHz CH NHz COOH = R GHz CH2 NH 2 + CO 2 



5. Carboxylic decomposition with the formation of fatty acids. 



R GHz CH 2 COOH = R GHz CH 3 + CO 2 



