XX11 CONTENTS 



teria obtaining their energy from the oxidation of simple carbon com- 

 pounds. Methane bacteria. Bacteria oxidizing carbon monoxide. Bac- 

 teria oxidizing hydrogen 61 



Chapter IV 



BACTERIA FIXING ATMOSPHERIC NITROGEN 



Nitrogen fixation in nature. Classification of nitrogen-fixing bacteria. Iso- 

 lation of anaerobic bacteria. Morphology of the anaerobic bacteria. 

 Distribution of anaerobic nitrogen-fixing bacteria in the soil. Physiology 

 of anaerobic nitrogen-fixing bacteria. Non-symbiotic nitrogen fixing 

 aerobic bacteria. Description of species of Azotobacter. Morphology 

 and life cycle of Azotobacter. Physiology of Azotobacter. Other non- 

 symbiotic nitrogen-fixing bacteria. Symbiotic nitrogen fixation by nodule 

 bacteria. Historical. Nomenclature. Media. Nodule formation. Iso- 

 lation of organism from nodules. Isolation from soil. Colony appearance. 

 Morphology and life cycle of organism. Motility. Physiology of nodule 

 bacteria. Specific differentiation. Nodule formation by non-leguminous 

 plants. Nodule formation in the leaves of some plants 103 



Chapter V 



HETEROTROPHIC, AEROBIC BACTERIA REQUIRING COMBINED NITROGEN 



General classification. Spore-forming bacteria. Classification of spore- 

 forming bacteria. Occurrence of spore-forming bacteria in the soil. Non- 

 spore-forming bacteria. Classification. Occurrence of non-spore-forming 

 bacteria in the soil. Thermophilic bacteria. Mycobacteria. Myxobacteria 141 



Chapter VI 



ANAEROBIC BACTERIA 



Oxygen tension in the growth of bacteria. Methods of isolation of anaerobic 

 bacteria from the soil. Cultivation of anaerobes. Classification of soil 

 anaerobes. Physiological activities of anaerobic bacteria. Soil processes 

 in which anaerobic bacteria take an active part 160 



Chapter VII 



BACTERIA REDUCING NITRATES AND SULFATES 



General classification of nitrate reducing bacteria. Organisms reducing 

 nitrates to nitrites. Organisms reducing nitrates to ammonia. Bacteria 

 reducing nitrates to atmospheric nitrogen. Description of some typical 

 denitrifying bacteria. Bacteria reducing sulfates to hydrogen sulfide. . . . 180 



Chapter VIII 



BACTERIA CAPABLE OF DECOMPOSING CELLULOSES AND OTHER COMPLEX 

 CARBOHYDRATES AND HYDROCARBONS IN THE SOIL 



Microorganisms concerned in the decomposition of celluloses in nature. 

 Anaerobic bacteria. Aerobic bacteria. Decomposition of cellulose by 



