THE FAMILIES AND GENERA OF THE BACTERIA 201 



bacter. Endospores never formed. Obligate aerobes, capable 

 of securing growth energy by the direct oxidation of carbon, 

 hydrogen or nitrogen or of simple compounds of these. Non- 

 parasitic (except in genus Rhizobium) — usually water or earth 

 forms. 



Tribe I. Nitrobactereae 



Organisms deriving their life energy from oxidation of simple 

 compounds of carbon and nitrogen (or of alcohol). 



Genus 1. Hydrogenomonas Orla-Jensen 1909, p. 311 



Monotrichic short rods capable of growing in the absence of 

 organic matter, and securing growth energy by the oxidation of 

 hydrogen (forming water). Kaserer (1905) who first described 

 the organism states that his species will also grow well on a variety 

 of organic substances. 



The type species is Hydrogenomonas pantotropha (Kaserer 

 1906) Orla-Jensen. Nikleuski (1910) described two additional 

 species, H. vitrea and H. flava. 



Genus 2. Methanomonas Ora-Jensen 1909, p. 311 



Monotrichic short rods capable of growing in the absence of 

 organic matter and securing growth energy by the oxidation of 

 methane (forming carbon dioxide and water). The type species 

 is Methanomonas methanica (Sohngen 1906) Orla-Jensen. 



Genus 3. Carboxydomonas Orla-Jensen 1909, p. 311 



Autotrophic rod-shaped cells capable of securing growth en- 

 ergy by the oxidation of carbon monoxide (forming carbon diox- 

 ide). The type species, Carboxydomonas oligocarbophila (Bei- 

 jerinck and van Delden 1903) Orla-Jensen, is described as non- 

 motile. 



Genus 4. Acetobacter Fuhrmann 1905, p. 8 



Synonyms: Mycoderma Persoon 1822; Ulvina Kuetzing 1837; Um- 

 bina Naegeli 1849; Bacteriopsisf Trevisan 1885; Gliacoccus Maggi 1886; 

 Acetimonas Jensen 1909. 



