THE NITRIFYING BACTERIA 603 



them of sufficient technical interest to justify for purposes 

 of illustration a more or less detailed description of one of 

 them. 



These very important and interesting nitrifying organisms, 

 of which there appear to be several, evade all efforts to 

 isolate them from the soils and to cultivate them by the 

 methods commonly employed in bacteriological work. 

 They can be successfully studied only through the employ- 

 ment of special media. 



The organism generally known as the nitro-monas of 

 Winogradsky will serve as an illustration: It is a short, 

 oval, and frequently almost spherical cell. It reproduces 

 by segmentation as usual for bacteria, but there is little 

 tendency for the daughter-cells to adhere together or to 

 form chains. In cultures they are commonly massed 

 together, by a gelatinous material, in the form of zooglea. 

 It does not form spores, and is probably not motile, though 

 Winogradsky believes he has occasionally detected it in 

 active motion. As has been stated, it does not grow upon 

 ordinary nutrient media, and cannot, therefore, be isolated 

 by the means commonly employed to separate different 

 species of bacteria. The most astonishing property of 

 this organism is its ability to grow and perform its specific 

 fermentative function in solutions devoid of organic matter. 

 It is believed to be able to obtain its necessary carbon from 

 carbon dioxide. For its isolation and cultivation Wino- 

 gradsky recommends the following solution: 



Ammonium sulphate 1 gram 



Potassium phosphate 1 gram 



Pure water . 1000 c.c. 



