180 R. E. BUCHANAN 



Key to the genera of Nitrobacteriaceae 



A. Cells rod shaped. 



1. Oxidizing ammonia to nitrous acid. Motile. 



Genus 1. Nitrosomonas 



2. Oxidizing nitrous acid to nitric acid Genus 2. Nitrobacter 



B. Cells spherical Genus 3. Nitrosococcus 



Genus 1. Nitrosomonas Winogradsky, 1892, p. 127 



Sj'nonym : 



Nitromonas Winogradsky 

 Cells rod shaped. Motile. Not growing readily on organic 

 media. Oxidizing ammonia to nitrates. 



The type species is Nitrosomonas europoea Winogradsky. 



Genus 2. Nitrobacter Winogradsky, 1892, p. 127 



Cells rod shaped, non-motile, not growing readily on organic 

 media, oxidizing nitrates to nitrates. 



Winogradsky named no species, although one was described. 

 It may be termed Nitrobacter winogradski and regarded as the 

 type species. 



Genus 3. Nitrosococcus Winogradsky, 1892, p. 127 



Cells spherical. Not growing readily on organic laboratory 

 media. Oxidizes ammonia to nitrites. 



Winogradsky termed the single species "les microbes nitreux 

 de nouveau monde" but without a species name. It may be 

 termed Nitrosococcus americanus and regarded as the type. 



REFERENCES 



Blanchard, R. 1906 Spirilles, spirochetes et autres microorganisms a corps 



spirale. La Semaine Medical, 26, 1. 

 Billet, A. 1890 Contribution a I'etude de la morphologie et du developpe- 



ment des Bacteriacees. Extrait du Bulletin scientifique de la France 



et de la Belgique. Paris. 

 CoHN, Ferdinand 1872 Untersuchungeniiber Bakterien. Beitrage zur Biolo- 



gie der Pflanzen 1 (Heft 1), 127-244. 

 CoHN, Ferdinand 1875 Ihitersuchungen liber Bakterien II. Beitrage z. 



Biologic d. Pflanzen 1 (Heft 3): 141-208. 



