CHAPTER III. 
THE CHEMISTRY OF BACTERIA. THE EFFECT OF 
BACTERIA ON THEIR ENVIRONMENT. 
A. General. 
3. Cytoplasm. 
B. Chemical Constitution of Bacteria. 
4. Spores. 
1. Elementary Composition. 
D. 
Food Relationships of Bacteria 
2. Chemical Constitution. 
1. General. 
3. Chemical Composition. 
2. Sources of Food. 
C. Composition of the Morphological 
(a) Nitrogen. 
Components of the Bacterial 
(b) Carbon. 
Cell. 
(c) Hydrogen. 
1. Cell membrane. 
(d) Oxygen. 
2. Capsule. 
(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 vegetati\'e 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 foodstuff's. The 
green plants by virtue of the chlorophyll contained within their leaves 
and stems possess the power of combining COo, water and nitrogenous 
salts under the influence of sunlight directly into the highly complex 
