CHAPTER IV. 



BACTERIAL METABOLISM. 



I. GENERAL. 



II. THE NATURE OF BACTERIAL MET- 

 ABOLISM. 



III. NITROGEN METABOLISM. 



IV. CARBON METABOLISM. 



V. QUALITATIVE CATABOLIC REAC- 

 TIONS OF BACTERIA. 



A. In Media Containing Only 



Utilizable Nitrogenous 

 Substances. 



B. In Media Containing Both 



Utilizable Nitrogenous 

 Substances and Utilizable 

 Carbohydrates . 



VI. THE QUALITATIVE INFLUENCE OF 

 UTILIZABLE CARBOHYDRATES 

 UPON THE ELABORATION OF 

 PROTEOLYTIC ENZYMES. 

 VII. QUANTITATIVE MEASURE OF BAC- 

 TERIAL METABOLISM. 

 VIII. THE SIGNIFICANCE OF BACTERIAL 

 METABOLISM. 



IX. FERMENTATION AND PUTREFAC- 

 TION. 



I. GENERAL BACTERIAL METABOLISM. 



Two distinct phases may be recognized in the life-history of a 

 bacterial cell; an anabolic or constructive phase, during which the 

 cell becomes morphologically complete; and a catabolic, vegetative, 

 or fuel phase, in which the mature organism reacts chemically upon 

 its environment to provide the energy (fuel) necessary for the main- 

 tenance of the cell. Chronologically, the anabolic phase precedes the 

 catabolic phase; that is to say, the bacterial cell must be morpho- 

 logically complete before it can bring about its characteristic energy 

 transformations; practically the two phases overlap somewhat. 



The actual amount of material required for the anabolic phase of the 

 bacterial cell is very small, for the actual weight of the average 

 bacterium is but 0.000,000,0016 of a milligram, approximately (see 

 page 25). The structural phase is practically ended, aside from the 

 replacement of comparatively slight losses of substance incidental 

 to the elaboration of soluble enzymes or to additional requirements 

 for the formation of structural elements, such as capsules, when the 

 organism is morphologically complete. The waste incidental to the 

 utilization of material for purely anabolic needs is likewise very small 

 in amount, and the total environmental change attributable to the 

 purely constructive phase of bacterial metabolism is slight andordin- 

 arily disregarded. 1 



Kendall, Jour. Med. Res., 1911, N. S. f xx, 140. 



