BIOLOGICAL VARIATIONS OF BACTERIA^ 

 I. Induced Variations in the Cultural Characters 



OF B. COLI 



M. R. SMIRNOW 

 Yale Medical School, New Haven, Connecticut 



Variations in the biological characteristics of the various mem- 

 bers of the Colon-typhoid group have been reported by num- 

 erous investigators. These range from mere observations as 

 to peculiarities in the fermentative or other biological tests 

 up to actual mutations as interpreted by De Vries. 



The most important observations along the latter line are 

 reported by Massini (1907), who isolated a type of B. coli he 

 called "B. coli-mutahilis." In his observations, he found this 

 organism would produce flat colorless colonies on Endo's medium, 

 if transplanted every twenty-four hours. When transplanted 

 at a later period, however, it would produce nodular shaped 

 colonies which became red. The colorless colonies always gave 

 rise to colorless colonies when transplanted not later than twenty- 

 four hours, whereas the red colonies once obtained, never gave 

 rise to any but red colonies irrespective of the time of transfer. 

 The knob like colonies appeared only on lactose media though 

 other carbohydrate media were used. He observed a single 

 reversion from the red to the colorless type, which, however, 

 could not be repeated. 



Burk (1908) reports the isolation of a similar mutant and 

 records careful observations which were continued over a period 

 of five months. 



Of the more interesting reports in literature on modifications 

 of B. coli and allied organisms may be mentioned those of Peck- 



^ Read in part, before the meeting of the Society of American Bacteriologists, 

 held at Philadelphia, December, 1914. 



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