ARTHUR ISAAC KENDALL 229 



energy phase comprises those chemical changes which the mature microbic cell 

 induces in its environment in fulfilment of its particular and characteristic chemical 

 activity. 



The amounts of substance required for the structural and energy phases respec- 

 tively, are very unlike. Fifteen millions of bacteria of ordinary size would scarcely 

 balance an ounce weight.' The weight of a simple bacterial cell, therefore, is little 

 indeed, and about 85 per cent of this is water. On the other hand, the amount of 

 substance transformed for energy by bacterial cells is, or may be, relatively great. 

 Hence, the expenditure of foodstuffs in the energy, as contrasted to the structural 

 phase, is frequently in the order of hundreds to one. 



Yet it is not a matter of indifference just what the chemical nature of these phases 

 is dependent upon. Bacteria, like other known living things, are nitrogen-containing. 

 Hence some suitable source of nitrogen must be available for structural needs. On 

 the other hand, most bacteria may derive the oxidizable carbon for their energy 

 requirement either from compounds containing nitrogen as well as oxygen, as in the 

 amino acids and their complexes, or from carbohydrates having a suitable configura- 

 tion. Fats on the whole are probably not particularly suited for the energy require- 

 ments of most bacteria. 



There is also a group of non-nitrogenous substances, departing somewhat from 

 the carbohydrate configuration, as certain organic acids (tartaric, for example), which 

 are acceptable sources of carbon for energy by many bacteria. A discussion of this 

 problem, however, is without the scope of this chapter, which deals more specifically 

 with carbohydrates. 



Carbohydrates frequently have a profound effect upon the character of the sub- 

 stances produced by bacterial action. Thus, to cite a few well-known examples:^ 



The diphtheria bacillus growing in a suitable nitrogenous medium produces the 

 characteristic, deadly, well-known soluble toxin which makes the organism formid- 

 able. If, before the organisms are cultivated, some glucose is added to such a medium, 

 the microbe produces considerable amounts of acid, principally lactic, but no toxin 

 whatsoever. 



The proteus bacillus produces large amounts of indol, and forms a soluble, proteo- 

 lytic enzyme when it is cultivated in a suitable nitrogenous medium. If, however, 

 before the organism is inoculated, some glucose is added to the nitrogenous medium, 

 it no longer produces indol nor the proteolytic enzyme. It forms considerable amounts 

 of lactic acid instead.^ 



In a similar manner the various strains of Bacillus coli produce indol and phenolic 

 bodies from the nitrogenous constituents of ordinary nutrient broth, but the addition 

 of glucose to such a medium prior to inoculation with the microbe changes it into a 

 lactic-acid-producing microbe. These latter observations have some significance in 

 the genesis of indol in the intestinal tract. ^ 



It appears, therefore, that the addition of utilizable carbohydrate to nitrogenous 



' Kendall, A. I.: Civilization and the Microbe, p. 17. 1923. 



^ See Kendall, A. I.: Physiol. Rev., 3, 438. 1923. 



i Kendall, A. I., Cheetham, H. C, and Hamilton, C. S.: /. Infect. Dis., 30, 251. 1922. 



^ Kendall. A. I.: Bacteriology, General, Pathological and Intestinal (2d ed.), p. 70. 1921. 



