ANAEROBIC BACTERIA 175 



probably coming in most cases originally from the soil has 

 been made by Weinberg and Seguin. 67 

 III. Bacteria obtaining their oxygen from inorganic salts: 



1. Bacteria reducing nitrates. 



2. Bacteria reducing sulfates. 



Both of these groups are described in detail elsewhere (p. 180). 



Anaerobic organisms may occur in the soil in great abundance; 

 Ucke 68 found a garden soil to contain 13| million cells of anaerobic bac- 

 teria and 500,000 spores per 1 gram of soil. In some cases individual 

 species are found in the soil in great abundance. Kiirsteiner, for exam- 

 ple, found as many as 1 million and more cells of Bac. putrificus per 1 

 gram of soil. Bac. amylobacter was found by Bredemann to be present 

 in practically every soil examined, both in the surface layer and in the 

 subsoil, in cultivated soils, in primeval forests and in pure sand; the 

 organism occurred only irregularly in acid peat soil. Out of 200 sam- 

 ples of Swiss soils examined, only seven did not contain this organism. 69 

 The number of colonies formed on artificial media are considerably less 

 than the actual number of organisms actually present in the soil; this is 

 brought out by the results of Dorner, 69 who found that out of 1000 

 spores present in a medium, only 3 germinated and developed into 

 colonies, while out of 1000 vegetative cells, 45.1 produced colonies. 



By the use of the dilution and selective culture method, Duggeli 70 

 found 1000 to 1,000,000 anaerobic butyric acid bacteria per gram of 

 soil, to 1000 anaerobic cellulose-decomposing bacteria, 100 to 1,000,000 

 anaerobic nitrogen-fixing bacteria, from 100 to 1,000,000 anaerobic 

 protein-decomposing bacteria and 100 to 1,000,000 pectin-decomposing 

 bacteria. By the deep tube method, only between 19,000 and 900,000 

 anaerobic bacteria were found per gram of soil. This is due to the 

 fact that no single solid medium can be devised which would be favorable 

 for the development of all anaerobic bacteria. 



Various anaerobic bacteria take an active part in the composting 

 of manure in the heap, whenever there is an insufficiency of aeration. 

 The so-called phenomenon of "putrefaction" is chiefly a result of the 

 decomposition of protein substances under anaerobic conditions, due to 



67 Weinberg, M., and Seguin, P. La gangrene gazeuse. Masson & Cie. Paris. 

 1918. 



68 Ucke, A. Ein Beitrag zur Kenntnis der Anaeroben. Centrbl. Bakt. I, 23: 

 996-1001. 1898. 



"Dorner, 1924 (p. 165). 

 70 Duggeli, 1921 (p. 39). 



