5. Nitrosomonas 



A culture labeled Nitrosomonas europaea was received from 

 Dr. Martin Alexander of Cornell University. Dr. Alexander stated 

 that the culture was not pure and that attempts at purification had 

 not been successful. Another culture with the same label was ob- 

 tained from the American Type Culture Collection (ATCC). 



Flagellar Characteristics 



Stains were made directly from the broth culture furnished by 

 Dr. Alexander. Two types of flagellated bacteria were seen. Most 

 numerous was a small rod with polar monotrichous flagellation. 

 The wavelength of the flagellum was exceptionally short averaging 

 0.93 micron. A much smaller number of rod shaped organisms had 

 polar monotrichous flagella of much greater wavelength, averaging 

 2.3 microns, or about 2i/^ times the other one. The soma of the 

 organism with the long wavelength flagellum did not take the 

 flagella stain and was practically invisible. The author did not 

 plate or attempt to grow the Alexander culture in the proper syn- 

 thetic medium. However a transfer was made into peptone-yeast 

 extract broth, and growth appeared. This growth had a pinkish- 

 brown color, water insoluble; flagella stain showed polar mono- 

 trichous flagella of 2.2 micron wavelength. Morphologically the 

 organism was similar to the one with the long wavelength seen 

 in the original culture. The real N. europaea would thus seem to 

 be the type with the short wavelength flagella illustrated in Fig. 4a. 



The ATCC culture of N. europaea, 12248 was stained directly 

 from the original suspension. The predominant flagellation was 

 polar monotrichous, with a smaller proportion of polar multitri- 

 chous individuals. The flagellar wavelength was rather variable 

 ranging from 1.3 to 1.6 microns. On transfer to nutrient broth 

 good growth was obtained of organisms with the same flagellation 

 found in the original suspension. No growth was obtained in media 

 free from organic matter. This organism apparently is not auto- 

 trophic and not typical of Nitrosomonas. 



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