BACTERIAL METABOLISM WITHIN THE BODY 669 



nitrogen, as an element of great structural significance, and carbon, of 

 peculiar importance as the basis of the energy phase of bacterial 

 metabolism. 



a. Structural Chemical Requirements. Bacteria can not multiply 

 in non-nitrogenous media, and the organisms of interest and significance 

 to man derive their nitrogen requirements from nitrogen in combination 

 with carbon, hydrogen and oxygen of the amino-acid complexes poly- 

 peptids, peptones, or proteins. The more fastidious organisms, as the 

 Gonococeus and Meningococcus, require, or at least develop best in, media 

 containing protein but little altered from the state in which it exists in 

 the human or animal body. Others grow very well indeed in media con- 

 taining less highly organized nitrogen, as for example that of peptone. 

 None will grow in the absence of this element ; hence, it may be regarded 

 as an essential structural element, Nitrogen has no energy value, however, 

 for parasitic or pathogenic microbes. 



b. Energy Chemical Requirements. Bacteria derive their energy 

 from the oxidization of carbon, in the last analysis, and the state of com- 

 bination of this element with others particularly oxygen and hydrogen 

 [as well as nitrogen in proteins and protein derivatives] determines to a 

 very considerable degree the nature of the products of specific bacterial 

 metabolism. The influence of associative elements upon bacterial metab- 

 olism and even the specificity of bacterial action, from the viewpoint of 

 energy, is shown in the following well authenticated series of illustrations : 



4. The General Nature of the Products of Bacterial 



Growth, Arising from the Utilization of Proteins 



and of Carbohydrates for Energy Toxin, 



Indol and Enzyme Formation. 



Diphtheria Toxin. It is well known that the soluble or exotoxin of 

 the diphtheria bacillus is the specific product which makes this organism 

 formidable to man. Diphtheria toxin is also excreted incidentally to the 

 growth of the microbe in plain nutritive broth, which consists essentially 

 of a neutral mixture of peptone, meat extractives, salts and water. In 

 such a medium, the diphtheria bacillus develops rapidly and within a 

 week or ten days the filtrate of this culture medium, freed from all bacteria 

 or other particulate matter, is extremely toxic for guinea pigs. Indeed, 

 0.025 cubic centimeter of such bacteria-free broth frequently kills 250 

 gram guinea pigs within four days with very definite specific symptoms 

 and lesions. 



Contrast this highly toxic broth with that resulting from the growth 

 of the same organism under precisely the same conditions in the same 



