ON NITRIFICATION^ 



III. THE ISOLATION AND DESCRIPTION OF THE NITRITE 



FERMENT^ 



AUGUSTOBONAZZI 



(with plate xiv) 



Introduction 



As a part of the physiological investigations upon nitrification 

 carried on in this laboratory, the isolation of pure cultures of the 

 nitrite-forming organisms became a necessity. Since difficulties 

 in the isolation of these organisms have been encountered by 

 many workers in the field of soil bacteriology, and since no accurate 

 description of the organisms of nitrification from North American 

 soils has been pubUshed as yet, it was deemed advisable to de- 

 scribe the organisms responsible for the formation of nitrites in 

 the Ohio soils and the methods used in their isolation. 



The following contribution, which is the result of a long period 

 of study, is here given to describe an organism, capable of form- 

 ing nitrites from ammonia, isolated in a pure state from Wooster 

 soil after many unsatisfactory attempts. 



Historical 



In 1890 Jordan and Richards (4) in Massachusetts stated 

 that they had isolated a nitrifying organism which was capable 

 of oxidizing ammonia salts to nitrates when grown in solutions 

 free of organic matter. The dilution method was the one relied 

 upon by these investigators for obtaining pure cultures. Their 

 description of this nitrifier is here reproduced. 



' Contribution from the Laboratory of Soil Biology, Ohio Agricultural Experi- 

 ment Station. 



^ The first paper of this series dealing with the subject of nitrification appeared 

 under the title "Preliminary observations" in Ohio Agric. Exper. Sta. Technical Bull. 

 7. 1915. The second paper under the title "Intensive nitrite formation in solution" 

 appeared in Jour. Bacteriology 1918. Thanks are due Dr. E. R. Allen, in whose 

 laboratorj' this work was undertaken, for kind advice and criticism. 



Botanical Gazette, vol. 68] [194 



