108 PRINCIPLES OF SOIL MICROBIOLOGY 



cum. When a pure culture is wanted, the culture is pasteurized (at 75° for 10 

 minutes), whereby the non-spore forming aerobe is killed and the spore-forming 

 Clostridium is obtained pure. 26 



Bredemann 27 used a solid medium of the following composition: 



Glucose 1.0 gram [Agar 1.6 grams 



or 



Witte peptone 1.2 grams [Gelatin 20.0 grams . 



Liebig's meat extract. . 0.8 gram Distilled water 100 cc. 



NaCl 0.2 gram Reaction slightly alkaline 



The various butyric acid bacteria, including the CI. yastorianum, grow 

 very well on this medium, which can be used both for the isolation and 

 cultivation of the organisms. 



26 Omeliansky, W. L., and Solounskoff, M. Sur la distribution des bacteries 

 azotofixatrices dans les sols russes. Arch. Sci. Biol. 18: 1-24. 1915. 

 "Bredemann, 1909 (p. 109). 



PLATE VI 

 Non-Symbiotic Nitrogen Fixing Bacteria 



25. Clostridium pastorianuvi (Bac. amylobacler) , stage preceding spore-forma- 

 tion; stained with gentian violet, X 660 (from Omeliansky and Solounskoff). 



26. Clostridium pastorianum (Bac. amylobacter) , spore-formation, X 660 

 (after Winogradsky and Omeliansky). 



27. Clostridium pastorianum (Bac. amylobacler), large involution forms; dark 

 color due to coloration of the glycogen with iodine (after Bredemann and 

 Omeliansky). 



28. Azolobacler chroococcum, young culture (from Krzemieniewski). 



29. Az. chroococcum, resting forms of sarcina type (from Krzemieniewski). 



30. Az. chroococcum, thread forms, individual cells undergoing division (from 

 Krzemieniewski) . 



31. Az. chroococcum, growth on agar, showing the darkening of the culture 

 (from Krzemieniewski). 



32. Az. agile, grown on phosphate-glucose agar, 2 days old, X 660 (from 

 Beijerinck). 



33. Az. agile, showing fiagella, stained by method of Zettnow, X 660 (from 

 Beijerinck). 



34. Bac. asterosporus, 1-5, showing different stages of development and spore 

 formation; 6, spore with folded envelope; 7, cross section of spore (after Brede- 

 mann and Omeliansky). 



35. Az. vinelandii (from Lipman). 



36. Bac. malabarensis: A, culture on meat extract agar; B, on soil infusion- 

 mannite agar; C, soil infusion mannite solution (from Lohnis and Pillai). 



