CHAPTER 26 

 CHROMOBACTERIUM AND ACHROMOBACTERIUM 



CHROMOBAGTERIUM 



Definition. — Chromobacterium. 



Small, non-sporing, aerobic rods, usually motile and usually Gram-negativo, 

 producing a yellow, red, or violet pigment, which is generally insoluble in water. 

 Saprophytic ; commonly found in water or soil. 



Type species. Chromobacterium, violaceum. 



Numerous organisms of this group have been isolated at various times from 

 water, soil, sewage, and occasionally from contaminated food-stufEs. Chr. violaceum 

 was described by Bergonzoni in 1881 (see Report 1920). Chr. prodigiosum was first 

 observed by Bizio in 1823 (see Breed and Breed 1924), who found it in " bleeding 

 polenta ". Chr. aquatile was isolated from water by Frankland and Frankland 

 in 1889. 



The classification of these organisms presents considerable difficulties. The 

 American Committee of Bacteriologists has created a genus, which they call Erythro- 

 hacillus, for the inclusion of those bacilli which produce a red or pink pigment. 

 The genus Chromohacterium they reserve for those bacilli which produce a violet 

 pigment. As these organisms have received relatively little attention from bacterio- 

 logists, and as in consequence their properties have been incompletely studied, it 

 would seem advisable for the moment to group all the aerobic non-sporing pigment- 

 forming rods into the single genus Chromobacterium. With regard to the naming 

 of the individual species within the genus, there is considerable confusion. One 

 and the same organism has frequently been described under two names, and specific 

 names have been given to organisms which appear to be merely varieties of 

 existing species. We shall therefore describe in some detail those organisms which 

 undoubtedly deserve specific rank, and shall refer briefly to others whose claim to 

 this distinction is more doubtful. 



Morphology. — The organisms of this group are small rods, varying in length from 

 about 1-0 to 3-0 /<, and in breadth from about 0-5 to 0-7 //. Chr. prodigiosum may 

 be regarded as an exception, since it is usually described as a small cocco-bacillus. 

 It is necessary to point out, however, that the size of this organism is subject to 

 considerable variation, and that even on the same type of medium a single strain 

 may at one time give rise to cocco-bacilli, and at another to rod-forms indistinguish- 

 able from those formed by other members of Chromobacterium (Fig. 129). Motility 

 is a frequent characteristic, and is dependent on the possession of peritrichate 

 or sometimes polar flagella. Most members of this group are Gram-negative. 



Cultural Reactions.^Growth occurs readily on the ordinary media ; a parti- 

 cularly heavy growth is generally observed in broth. 



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