Ammonia Bacteria 



163 



of it. There are differences in the chemical processes 

 by means of which the different species produce am- 

 monia. The protein substances from which it is derived 

 are complex and insoluble, and the bacteria cannot 

 use them as food in this insoluble form. The bacteria 

 are like higher plants in this respect, and can only draw 

 their food from the dissolved materials in the medium 

 in which they live. 



Fig. 24. Ammonifying bacteria. — 1. Bacterium mycoides; X 3,000. (Nadson.) 

 2. Bacterium mycoides; involution toiraB] X 3,000. (Nadson.) 3. Bacterium 

 lumeacens. (Myer.) 4. Protma vulgaris; X 3,000. (Nadson.) S. Proteua 

 vulgaris; involution forms; X 3,000. (Nadson.) 



