THE OCCURRENCE OF DIFFERENT TYPES OF THE 

 COLON-AEROGENES GROUP IN WATERS 



L. A. ROGERS 



Research Laboratories of the Dairy Division, United States Department of 



Agriculture 



Received for publication August 14, 1917 



Recent work on the colon-aerogenes group of bacteria (Levine, 

 1916; Rogers, Clark and Davis, 1914; Rogers, Clark and Evans, 

 1914 and 1915; Winslow and Kligler, 1916) has confirmed and 

 amplified the view held by most bacteriologists that the group 

 includes two distinct types or species represented by B. coli 

 and B. aerogenes. Although the distinction between the two 

 types has not been very clearly defined, the former has been 

 considered as the predominant organism of the feces of warm 

 blooded animals. 



The work cited has demonstrated that there is a real difference 

 between the two colon types and that this difference can be 

 detected by certain simple laboratory tests. 



The B. coli type is characterized by the production of ahnost 

 exactly equal volumes of hydrogen and carbon dioxide in the 

 anaerobic fermentation of glucose, the failure to give the Voges- 

 Proskauer reaction, the formation of indol from tryptophane 

 and the comparatively low fermentative ability of a greater part 

 of the cultures. 



The B. aerogenes type, on the other hand produces an excess 

 of carbon dioxide over hydrogen in the anaerobic fermentation 



1 Published by permission of the Secretary of Agriculture. 



The writer wishes to acknowledge his indebtedness to his colleagues, particu- 

 larly to Dr. William M. Clark for assistance and for many suggestions. 



Since this paper was written, the writer has had the privilege of reading two 

 manuscripts by Winslow and Cohen. They cover much the same ground as this 

 paper and the results and conclusions drawn are substantially in accord with 

 those given here. 



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