CLASSIFICATION OV BACTERIA ;^^ 



Several other important fermentations are due to bacteria, as the 

 causal organisms, namely, the butyric, cellulose, and mucilaginous 

 fermentations. The retting of vegetable fibers, the manufacture of 

 indigo, the curing of tobacco are all dependent on bacterial fermentations. 



The saprogenic organisms are concerned with decay, or putrefac- 

 tion. The decomposition of dead animal and plant bodies is far from 

 being a simple putrefactive process. Nitrogenous and non-nitrogenous 

 bodies are both concerned in the putrefactive changes and they are 

 broken down into simpler nitrogenous and non-nitrogenous compounds, 

 or even elements. Proteins are split up into albumoses and peptones, 

 aromatic compounds (indol and skatol), amino compounds (leucin, 

 tyrosin, glycocol) , fatty and aromatic acids and inorganic end products 

 (nitrogen, ammonia, hydrogen, methane, carbon dioxide and hydrogen 

 sulphide). Ptomaines andjother poisonous bodies are formed known 

 as toxins, a name applied indiscriminately to all bacterial poisons.' 



The activity of all these organisms in causing decomposition of 

 animal and plant products is important in preserving the circulation 

 of carbon and nitrogen in nature. Without such destructive changes, 

 the elements carbon and nitrogen would be combined in such a form 

 as to be forever lost to animals, and plants. In the dissolution of these 

 complex bodies, the simpler chemic compounds are released and can 

 be used over again by Hving animals and plants. Much should be 

 made of the circulation of the elements in nature and the two chief 

 cycles are the carbon cycle and the nitrogen cycle with a sulphur and 

 phosphorus cycle as well. There are two main processes in organic 

 hfe: the constructive processes (anabolism), and the destructive 

 processes (katabolism). Construction is accomphshed mainly by green 

 plants and the prototrophic bacteria. Destruction is the work of 

 animals, metatrophic and paratrophic organisms; which have to break 

 down organic matter to Hve. Thus the elements of the organic world 

 are kept in perpetual circulation. 



Paratrophic Bacteria. — ^These organisms occur only in the tissues 

 and vessels of living organisms and are, therefore, true parasites. Many 

 of them are responsible for animal and plant diseases and the special 

 types, as far, as they concern this book, namely, those which induce 



'Consult Lathrop, Elbert C: The Organic Nitrogen Compounds of Soils and 

 Fertilizers. Journ. Franklin Inst. 183 : 169-206, Feb.; 303-321, Mch.; 465- 

 498, Apr., 1917- 

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