PART II. 



PHYSIOLOGY OF MICROORGANISMS* 



DIVISION I. 



NUTRITION AND METABOLISM. 

 INTRODUCTION. 



PRINCIPLES OF NUTRITION AND METABOLISM. The nutrition and 

 metabolism of microorganisms is based on the same principles that regu- 

 late animal and plant metabolism. Only in a few instances, i.e., in the 

 anaerobiosis and in nitrogen fixation, we have processes unparalleled 

 in the more highly developed organisms. Since it will be necessary fre- 

 quently to refer to plant and animal nutrition in the course of this discus- 

 sion, these principles, therefore, are briefly discussed in the following 

 paragraph. 



Green plants feed only on inorganic substances. They assimilate car- 

 bon dioxide (CO 2 ) from the air which unites with water, nitrates, potassium, 

 calcium, and other salts of the soil and form the body substances of the 

 plant. The cellulose, starch, sugar, protein and all other compounds 

 constituting the plant cells are produced from the above mentioned 

 inorganic substances. This formation of organic compounds requires a 

 certain amount of energy. If cellulose is burned to carbon dioxide (CO 2 ) 

 and to water (H 2 O), a certain amount of energy is liberated in the form 

 of heat. Consequently the same amount of energy will be needed to 

 produce cellulose from carbon dioxide and water; for the law of the 

 conservation of energy requires that if a certain process liberates a certain 

 quantity of energy, the reverse process will require the same quantity of 

 energy. Green plants get their energy from the sunlight. The radiant 

 energy of light is transformed by the chlorophyl granules of the plant 

 leaves into chemical energy which causes the formation of organic com- 



* Prepared by Otto Rahn. 



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