CHAPTER XII 



CHEMICAL CHANGES PRODUCED BY MICROORGANISMS 

 ENERGY RELATIONSHIPS 



MICROORGANISMS, like all other forms of life, as long as 

 they are living and growing require a constant supply of 

 energy. This is used by the organism in various ways. 

 Energy is required in some cases for manufacture of food, 

 in all cases for the building up of complex compounds 

 such as protoplasm. Energy is necessary for growth and 

 for movement. Many of the chemical changes brought 

 about by microorganisms are the result of their methods 

 of securing energy. 



Microorganisms show great variation in the manner 

 in which they secure their growth energy, and in the 

 manner in which it is utilized. Some microorganisms 

 require organic food, others are capable of manufacturing 

 their own food. Some live under aerobic conditions, 

 others under anaerobic conditions. A knowledge of the 

 sources of energy available to microorganisms and of the 

 ways in which they make use of this energy is therefore 

 necessary. 



Sources of Energy. Apparently the common, source of 

 < lu-rgy made use of by all forms of life is oxidation. An 

 additional source of energy utilized by some forms of life 

 is sunlight. Most species of higher plants possess the 

 green coloring material chlorophyll which enables them 

 to make use of the energy of the sun's rays for the pur- 

 pose of manufacturing their food from inorganic com- 

 pounds, primarily from carbon dioxide and water with 

 the formation of carbohydrates, particularly starch. 



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