CHAPTER III. 



THE CHEMISTRY OF BACTERIA. THE EFFECT OF 

 BACTERIA ON THEIR ENVIRONMENT. 



A. GENERAL. 



B. CHEMICAL CONSTITUTION OF BAC- 



TERIA. 



1 . Elementary Composition. 



2. Chemical Constitution. 



3. Chemical Composition. ' 



C. COMPOSITION OF THE MORPHOLOGI- 



CAL COMPONENTS OF THE 

 BACTERIAL CELL. 



1. Cell membrane. 



2. Capsule. 



3. Cytoplasm. 



4. Spores. 



D. FOOD RELATIONSHIPS OF BACTERIA. 



1. General. . 



2. Sources of Food. 



(a) Nitrogen. 

 (6) Carbon. 



(c) Hydrogen. 



(d) Oxygen. 



(e) Inorganic Salts. 



A. GENERAL CHEMISTRY OF BACTERIA. 



THE practical significance of bacteria is summed up in the nature 

 and extent of the chemical changes which they induce in their environ- 

 ment, the result of their multiplication and vegetative activity. These 

 changes are essentially analytical, for the function of bacteria in 

 nature is to transform dead organic matter from complex unstable 

 combinations of carbon, hydrogen, nitrogen, and oxygen, which are 

 worthless in the economy of nature, to fully mineralized, stable inor- 

 ganic compounds of these elements, which may be resynthesized by 

 plants. 



A small but formidable group of bacteria, chiefly those pathogenic 

 for plants, animals and man, act directly upon the living plant or 

 animal organism, producing changes in them which may be tempor- 

 arily incompatible with their well-being, and not infrequently lead to 

 their death and eventually to their mineralization. The pathogenic 

 bacteria, therefore, are also analytical in their activities and do not 

 differ essentially in this respect from the saprophytic types. 



It is necessary to consider briefly the method of the interchange 

 of material between the vegetable and animal kingdoms in order to 

 understand the full significance of bacterial action in the economy of 

 nature. All animals require preformed organic compounds for their 

 sustenance. They are unable to build up these compounds of which 

 their tissues are composed from chemical elements or from simple 

 inorganic salts. They are, therefore, dependent directly or indirectly 

 upon the synthetic activities of green plants for their foodstuffs. The 

 green plants by virtue of the chlorophyll contained within their leaves 



