SUBGROUPS AND GENERA OF THE BACTERIACEAE 53 



Plump rods, without spares, Gram-negative, motile by means of 

 peritrichous flagella, or non-motile, liquefying gelatin very slowly 

 or not at all. Usually showing marked power to ferment carbo- 

 hydrates, frequently with gas production. 



The type species is Bacterium coli Escherich. 



The genus is a large one, including many species. It is gen- 

 erally divided into subgroups based primarily upon the fermen- 

 tative reactions. It may be convenient to recognize these as 

 subgenera separated from each other by the characteristics 

 noted in the following key: 



Key to the subgenera of Bacterium 



A. Organisms which show a maximum of fermentative power, including fermen- 



tation of lactose, ' rarely pathogenic, some forms slowly liquefy gelatin. 



Subgenus 1. Aerobacter {or Eu-Bacterium) . 



B. Organisms not showing maximum fermentative power, never producing gas 



in lactose, frequently pathogenic, never liquefying gelatin. 



1. Producing acid and gas from glucose, sometimes other sugars, 



but not from lactose Subgenus 2. Salmonella 



2. Producing gas from none of the carbohydrates, acid sometimes 



formed Subgenus 3. Eberthella 



Subgenus 1. Aerobacter Beijerinck, 1900, p. 198 



Fermenting both glucose and lactose with formation of both acid 

 and gas. Pathogenicity slight. 



Type species is Bacterium (Aerobacter) coli Escherich. 



Subgenus 2. Salmonella, Lignicres, 



Fermenting glucose but not lactose with formation of acid and 

 gas. Frequently pathogenic. 



The type species is Bacterium (Salmonella) cholerae suis? 



Subgenus 3. Eberthella sub gen. no v. 



Not producing gas from any of the carbohydrates, acid may or 

 may not be formed. 



The type species is Bacterium (Eberthella) typhi. Fliigge. 



THE JOURNAL OF BAECTRIOLOGT, VOL. Ill, NO. 1 



