BACILLUS PROTEUS GROUP 359 



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. 1 



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 1.0 to 3.5 microns. Proteus bacilli 

 are actively motile and possess a large number of peritrichic flagella 2 

 which are frequently seen as a tangled filamentous mass surrounding 

 each individual cell. 3 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. 



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 4 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 

 do not liquefy this medium. The latter, Proteus zopfii, exhibits 

 negative geotropism on slanted solid media. It is now recognized 

 that cultures of B. proteus may gradually lose their gelatin-liquefying 

 power after prolonged cultivation, so that a cultural transition from 



B. proteus to B. zenkeri may be observed in the laboratory. A dis- 



ft 



1 Ueber Faulnisbakterien und deren Beziehungen zur Septikamie, Leipzig, 1885. 



2 Zettnow, Centralbl. f. Bakt., 1891, x, 689. 



3 Massea (Centralbl. f. Bakt., 1891, ix, 106) states that young bacilli may possess 

 from 60 to 100 flagella. 



4 Loc. cit. 



