BACTERIAL METABOLISM WITHIN THE BODY 679 



is quite similar to that of all living cells. The amount of material re- 

 quired to meet the structural requirements of bacteria, and to replace 

 losses incidental to the formation of soluble enzymes and other elements, 

 is very little. Usually, also, the structural waste incidental to the elabora- 

 tion of the bacterial substance is inconspicuous in amount and reactivity. 



The cytoplasm of the bacterial cell is always more or less poisonous 

 when it is liberated within the tissues of an animal or man, that of the 

 saprophytic types of bacteria being quite as reactive on the whole in this 

 regard as that of the very virulent organisms, as Bacillus diphtherias 

 (Vaughan). The significance of bacterial infection, however, is asso- 

 ciated primarily with the growth of bacteria in the tissues, or with the 

 absorption into the tissues of products incidental to their growth. In 

 other words, the energy phase of bacterial metabolism is in all probability 

 of the greatest importance from the viewpoint of microbic infection and 

 microbic intoxication. 



The products arising from the transformation of nutritive substances 

 into energy by bacteria are of two principal types nitrogen-containing, 

 or derivatives thereof, and non-nitrogenous. The former arise from pro- 

 teins or protein derivatives, the latter from carbohydrates, less commonly 

 from fats. 11 



The composition of the highly complex nitrogenous bacterial toxins, as, 

 for example, that of the diphtheria bacillus, is unknown, although it may 

 be separated from solution by protein precipitants, and it appears to 

 have some points of resemblance to that group of the proteins known as 

 the globulins. From the viewpoint of the present discussion, diphtheria 

 toxin, and the soluble bacterial toxins in general, may be defined as soluble 

 products of unknown but complex composition, containing nitrogen, aris- 

 ing from the utilization of proteins or protein derivatives for energy by 

 specific bacteria. 



In general, the measurable changes induced in the nitrogenous con- 

 stituents of culture media by the great majority of pathogenic microbes, 

 as deamination, or changes in amino nitrogen, are quantitatively the 

 same. (See table page 677.) The nitrogenous metabolism of bacteria 

 which produce soluble toxins, as the diphtheria, tetanus, and Shiga bacilli, 

 is comparable in magnitude and general characteristics to that of such 

 pathogenic bacteria as the typhoid bacillus, in whose cultures soluble, 

 specific toxins have not been detected. 



The qualitative changes induced by these same organisms upon ni- 

 trogenous [protein] substances are, on the contrary, quite unknown. The 

 elucidation of the chemical structure of toxins and other harmful nitro- 

 gen-containing products of the transformation of protein, or protein de- 

 rivatives, is a problem for the bacterio-chemist of the future to solve. 



"There is some evidence that lecithin and similar phosphatids may be decom- 

 posed by bacterial action with the liberation of physiologically active substances. 



