COLON-AEROGENES GROUP OF BACTERIA 



287 



BACTERIAL STRAINS 



Aerogenes type (from soils) 



Coli type (from soils) 



Coli type (from feces) 



447 



20 



173 



Results with dulcitol too incomplete to include in table. The figures indi- 

 cate both acid and gas production. 



All of the strains fermented glucose and lactose. Sucrose was 

 attacked by both the colon and aerogenes types, although the 

 high gas ratio group was as a group more active than the other, 

 excluding the soil coli. 



The present results do not bear out the contention that the 

 fecal and non-fecal types of aerogenes may be differentiated by 

 fermentation in adonitol, as 152 soil aerogenes strains out of 

 the 447 attacked the adonitol, whereas the remaining 295 did 

 not. These findings agree in principle with those of Winslow 

 and Cohen, who observed that "a greater proportion of B. 

 aerogenes from the unpolluted sources attacked adonite than did 

 those from the polluted waters." 



ATYPICAL STRAINS 



In the present collection of organisms which resemble the 

 aerogenes type, 18 at first appeared to occupy an intermediate 

 position where complete correlation could not be established. 



They persisted in giving methyl red positive and Voges and 

 Proskauer positive reactions in all three of the media employed, 

 after one, three and five days' incubation. Impurity of the 

 cultures was suspected and repeated platings were resorted to. 

 In this way the number of non-correlating organisms was reduced 

 from 18 to 4, although contaminating organisms could not be 

 demonstrated. 



The methyl red positive strains whose hydrogen ion concen- 

 tration was on the border line of the methyl red range (5.7 to 

 5.9) were made to return to their typical methyl red negative 

 reactions by repeated plating, their pH values being raised to 



