42 



starch. Other fermentable substances lactose, maltose, galactose and 

 mannitol were also observed but as these substances were all attacked with 

 gas formation they need not be considered. 



As was discussed in detail in Chapter II, the investigations of Harden, 

 Smith, Rogers and others on carbohydrate and nitrogen metabolism have 

 demonstrated adequately and conclusively that the colon group includes 

 two distinct subgroups, the methyl -red positive- Voges Proskauer negative- 

 uric acid negative group designated herein as the coli section, and methyl 

 red negative Voges Proskauer positive-uric acid positive group or aerogenes 

 section. These two main sections are recognized and each is subdivided 

 into species on the basis of correlated characters as described above. 



KEY TO THE MORE IMPORTANT SPECIES OF THE COLON GROUP. 



The colon group includes all non sporing Gram negative short rods, 

 fermenting glucose and lactose with acid and gas production and which 

 grow aerobically. 



I. Not producing acetyl methyl carbinol (Voges Proskauer reaction 

 negative) ; acid to methyl red, and carbon dioxide and hydrogen 

 produced in approximately equal volumes from glucose. Can- 

 not utilize uric acid as a source of nitrogen. 



COLI SECTION 



A. Sucrose not attacked. 



1. Salicin fermented with acid and gas. 



1. Boot, coli 



2. Salicin not attacked. 2. Bact. acidi-lactici 



B. Sucrose fermented with acid and gas. 



1. Motile. 3. Bact. communior 



2. Non-motile. 



a. Salicin fermented with acid and gas. 



4. Bact. neapolitanum 



b. Salicin not fermented. 5. Bact. coscoroba 



II. Producing acetyl methyl carbinol (Voges Proskauer reaction posi- 

 tive) ; alkaline to methyl red, and forms two or more times as 

 much carbon dioxide as hydrogen from glucose. Capable of 

 utilizing uric acid as a source of nitrogen. 



AEROGENES SECTION 



A. Glycerol and starch fermented with acid and gas formation; non 



motile, gelatin not liquefied. 6. Bact. aerogenes 



B. Glycerol and starch not fermented; motile, gelatin liquefied. 



7. Bact. cloacae 



In the 1917 and 1920 Standard Methods of Water Analysis the coli 

 section is not differentiated into species. The aerogenes section is sub- 

 divided on the fermentation of adonitol into a fermenting variety sup- 

 posedly of fecal origin and a non-fermenting variety which is regarded 

 as of non-fecal origin. The value of adonitol for this distinction has 

 not as yet been adequately investigated and is not generally accepted. 



