CHAPTER XVII 



UTILIZATION OF ALIPHATIC AND AROMATIC 

 COMPOUNDS BY BACTERIA 



S. A. KOSER 



University of Illinois 



Investigations of the carbon and nitrogen requirements of bacteria have directed 

 attention to the relatively simple compounds of these elements which in many cases 

 appear to be readily utilized by the organisms, both as a source of structural material 

 for building new protoplasm and also as a source of energy. The utilization of the com- 

 moner carbohydrates which are widely used in the ordinary fermentation tests is well 

 known. In addition to these, however, there are many other chemical groups which 

 are susceptible to bacterial attack. In the amino acids, the purines and extractives, 

 the alcohols, and the organic acids or their salts, we have a wide range of compounds 

 of definite chemical structure in which the nitrogen or carbon is supplied in a great 

 variety of different combinations. 



The utilization of these compounds has been studied in several ways, by qualita- 

 tive or quantitative tests for a certain component of a complex medium and by the 

 use of isolated compounds in chemically definite media. In the latter case an amino 

 acid, for example, may be added to a solution of certain inorganic salts so that it con- 

 stitutes the sole supply of available nitrogen. By varying the amino acids or other 

 nitrogenous compounds we can determine the ability of the organism to make use of 

 certain chemical groupings. Also, by analysis of cultures developing under these con- 

 ditions we can determine the products formed and thereby gain an insight into the 

 mode of attack and breakdown which the organism employs. It does not necessarily 

 follow, of course, that the same type of decomposition will take place under other con- 

 ditions or in the presence of other foodstuffs. 



UTILIZATION OF NITROGENOUS COMPOUNDS 



The common observation that most bacteria can develop readily in digests of 

 protein material has led to investigation of the availability of single, isolated amino 

 acids or other simple compounds of nitrogen. Added impetus has perhaps been given 

 to this line of study by the studies on animal nutrition in which it has been shown 

 that certain amino acids are indispensable for growth. In considering the nitrogen 

 requirements of bacteria the question arose whether certain amino acids are also in- 

 dispensable for the growth and reproduction of these forms. Can the inability of 

 certain pathogens to develop on ordinary media be explained by the lack of certain 

 essential components of nitrogen which are not supplied by the usual laboratory 

 media? May different species or groups of bacteria be distinguished from one another 

 by the ability of one to utilize certain simple compounds which the other is unable to 

 attack? Can the various toxin-producing types make use of simple amino acids and 

 if so is the toxin elaborated in their presence? 



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