394 THE COLI—CLOACM— PROTEUS GROUP 
BACILLUS PROTEUS GROUP. 
Synonyms.— Proteus vulgaris, Proteus mirabilis, Proteus zenkeri, 
Proteus zopfii, Proteus fluorescens. 
Historical.— The proteus group comprises several closely-related 
bacilli found commonly in soil, in water rich in organic matter, as 
sewage, in human feces, and associated with the decay of organic 
matter. The important members of the group were first isolated in 
pure culture and described by Hauser.^ 
Morphology.— The proteus bacilli are rod-shaped organisms of vari- 
able length which occur singly and in pairs as a rule; less commonly 
they remain adherent in short chains. The size of individual cells 
varies considerably, even in the same culture. The limits of varia- 
tion are comprised within the following dimensions: diameter from 
0.6 to 0.8 micron, length from 1 to 3.5 microns. Proteus bacilli 
are actively motile and possess a large number of peritrichic flagella^ 
which are frequently seen as a tangled filamentous mass surrounding 
each individual cell.'' Special staining methods are required for the 
demonstration of these flagella. The organisms produce no spores 
and form no capsules. They stain with ordinary anilin dyes, but 
somewhat faintly, and they are Gram-negative. 
Fig. 54.— Bacillus proteus, flagella stain. X 1500. (Gunther.) 
Isolation and Culture.— The members of the proteus group develop 
rapidly on gelatin at room temperature; the organisms typically 
liquefy the medium with great rapidity. Some strains liquefy gelatin 
but slightly or even not at all.^ The colonies of rapidly liquefying 
strains in 5 per cent gelatin are frequently very characteristic; the 
organisms tend to remain adherent, forming masses of bacilli which 
slowly move around in an area of liquefied gelatin. Hauser^ recognized 
four types of proteus bacilli classified according to their ability to 
liquefy gelatin: Proteus vulgaris liquefies gelatin rapidly; Proteus 
mirabilis liquefies gelatin slowly; Proteus zenkeri and Proteus zopfii 
> Ueber Faulnisbakterien und deren Beziehungen zur Septikamie, Leipzig, 1885. 
2 Zettnow: Centralbl. f. Bakteriol., 1891, 10, 689. 
' Massea (Centralbl. f. Bakteriol., 1891, 9, 106) states that young bacilli may possess 
from 60 to 100 flagella. 
^ Bengston: Jour. Infec. Dis., 1919, 24, 428. 
^ Loc. cit. 
