CHAPTER III 



THE CHEMISTRY OF THE BACTERIAL CELL 



There are certain chemical elements essential to 

 the existence of bacteria. Being composed of protein, 

 carbohydrates, fats and waxes, the bacteria must have 

 the elements that enter into the building of these sub- 

 stances. Hence, carbon, nitrogen, hydrogen, oxygen 

 and sulfur are indispensable for their development. 

 Aside from these, they require, like the higher plants, 

 lime, magnesia, phosphoric acid, potash and, perhaps, 

 iron. The proportion of some of these constituents 

 taken up by bacteria may be so slight as to preclude 

 their recognition, even by the most refined chemical 

 tests. Moreover, the proportions taken up are affected 

 both by the species of bacteria and by the composition 

 of the culture medium. 



Certain classes of bacteria — among them the species 

 found in drinking-water — can develop and multiply 

 on quantities of nitrogen compounds so minute as to 

 be altogether insufficient for hundreds of other species. 

 Similarly, certain groups of soil bacteria are known to 

 require much larger quantities of lime and phosphoric 

 acid than are required by other groups. This fact is of 

 great significance in the struggle for existence among 

 the bacterial inhabitants of the soil. 



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