FAMILY XITROBACTERIACEAE 



77 



Key to the species of genus Hydrogenomonas. 



A. Xot sensitive to high O2 concentrations. Growth in solution media under 



autotrophic conditions characterized by turbidity without pellicle formation. 



1. Hydrogenomonas pantotropha. 



B. Sensitive to high O2 concentrations. Growth in solution media under auto- 



trophic conditions characterized by pellicle adhering to walls of container. 



2. Hydrogenomonas vitrea. 



C. Sensitive to high O2 concentrations. Growth in solution media under auto- 



trophic conditions without pellicle formation. 



3. HTjdrogenomonas flava. 



1. Hydrogenomonas pantotropha 

 (Kaserer) Orla-Jensen. [Bacillus pan- 

 totrophus Kaserer, Cent. f. Bakt., II 

 Abt., 16, 1906, 688; Orla-Jensen, Cent, 

 f. Bakt., II Abt., 22, 1909, 311.) From 

 Greek pantos, everything and trophos, 

 feeds on; M.L. omnivorous. 



Rods: 0.4 to 0.5 by 1.2 to l.o microns 

 with rounded ends. Occur singly, in 

 pairs, and in chains. Encapsulated. Ac- 

 tively motile by means of a single long 

 polar flagellum. Gram stain not re- 

 corded. Bipolar staining in old cultures. 



Inorganic solution : When cultivated 

 under an atmosphere of O2, CO2 and 

 Ho, the liquid becomes turbid without 

 pellicle formation. 



Inorganic solid media : When cultivated 

 under an atmosphere of O2, CO2 and H2, 

 the colonies are yellow and slimy, and the 

 agar plates have an odor resembling hot 

 soapy water. 



Gelatin colonies: Yellow, smooth, 

 rarely concentrically ringed or greenish. 



Gelatin stab: Growth only at surface. 

 .\s a rule no liquefaction. 



Agar colonies: Same as on gelatin, 

 greenish, often slimy. 



Broth: Turbid, somewhat slimy, and 

 occasional pellicle. 



Milk: Xo coagulation. A yellow pelli- 

 cle forms. Medium becomes slimy and 

 assumes a dirty flesh color. 



Potato: Moist, yellow, glistening. 



Indole is not formed. 



Hydrogen sulfide is not formed. 



Nitrite is not produced from nitrate. 



Does not act on carbohydrates. 



Aerobic. 



Optimum temperature 28° to 30°C. 



Facultative autotroph. 



Distinctive characters : Develops auto- 

 trophically in inorganic medium under an 

 atmosphere of Ho, O2 and CO2. Oxidizes 

 hydrogen to water and uses CO2 as the 

 source of carbon for growth. 



Source : Isolated from soil near Vienna. 



Habitat : Probably widely distributed 

 in soil. 



2. Hydrogenomonas vitrea Xiklewski. 

 (Jahrb. f. wissensch. Botanik, 48, 1910, 

 113). From Latin vitreus, of glass, trans- 

 parent. 



Rods: 2.0 microns in length, cells ad- 

 hering to each other as by slime. Mo- 

 tility not observed. 



Agar colonies on inorganic medium in 

 presence of Ho, Oo and CO2: Delicate, 

 transparent, with slight fluorescence, and 

 yellow center. Surface folded. Do not 

 develop readih' beneath the surface of 

 medium. 



Agar streak on inorganic substrate : 

 Same as agar colonics except that growth 

 is spreading. 



Inorganic liquid medium in presence of 

 H2, O2 and COo: Pellicle, adherent to 

 wall of tube. Good development when 

 there is from 2 to 8 per cent oxygen in 

 the gas. At higher Oo concentrations 

 good growth occurs only in association 

 with H. flava or other bacteria. 



Oxidizes hydrogen to water. 



Microaerophilic, growing in an atmos- 

 phere of low oxygen tension, not exceed- 

 ing 8 per cent. 



Facultative autotroph. 



