A Comparative Study of the Friedländer and Coli-aerogenes Groups

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Abstract
The difficulty of distinguishing between members of the Friedlander and of the coli-aerogenes groups of organisms, and the inadequacy of the present taxonomic criteria are emphasized. The usual definition of the Friedlander group does not necessarily exclude organisms of the coli-aerogenes group when these are in the mucoid (M) phase. The confusion surrounding their relationships has been due in part to a failure to consider carefully the variational aspects of the problem. A study was made of 100 gram-negative, non-spore-forming, non-motile encapsulated bacillary forms. In the present paper the occurrence and characteristics of normal and variant forms maintained under ordinary conditions of stock culture transfer are reported. Three principal phases, the mucoid (M), the smooth (S) and the rough (R), were found to characterize the coli-aerogenes, as well as the Friedlander cultures. 3 well-defined transitional colony forms were also recognized. A tendency toward M [long dash]> S variation characterized the majority of mucoid (M) strains under ordinary laboratory conditions. 80 S variants maintained under similar conditions proved relatively stable. No constant cultural or morphological differences which could be considered of significance in establishing classificatory criteria were observed among the organisms of the various groups, when they were in either the M, S or R phase. Cultures which were preserved for further study by the method of "lyophile" desiccation showed no cultural evidences of dissociative change.

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