192 



The Production of Variation in the Physiological Activity of 

 Bacillus coli by the Use of Malachite- Green. 

 By Cecil Kevis. 



(Communicated by Sir J. R Bradford, Sec. R.S. Beceived February 22, — 

 Read March 28, 1912.) 



In a paper published last year (1) I showed that by the cultivation of 

 a typical Bacillus coli in peptone broth containing steadily increasing 

 quantities of malachite-green, the organism could be trained to develop 

 without difficulty, even in the presence of O'l per cent, of the dye, but 

 that, at the same time, the organism underwent a profound change, and 

 lost the power of producing gas in certain sugars and polyhydric alcohols, 

 the attack ceasing at the acid stage. The properties of the organism so 

 produced were of a permanent character. 



As the change was at the moment unique, it was necessary to produce, 

 if possible, the same change in other organisms of the same type, on 

 account of the far-reaching deductions which may be made from this 

 variation. In the case recorded, however, the possibility of contamination 

 was practically excluded by the precautions employed, while mathematically 

 it was almost negatived. 



Four organisms (three being typical strains of Bacillus coli, and the 

 fourth Bacillus acicli lactis Hueppe) were carefully plated out, and grown 

 for periods of seven days in peptone broth (reaction + 1) to which 

 increasing amounts of malachite-green had been added until 010 per cent, 

 was present. The cultures were incubated at 37° C. After a suitable 

 interval (about 15 to 20 reinoculations carried out with every precaution 

 against accidental contamination) the cultures were plated out and examined 

 for physiological activity. 



Of the four organisms, which may be distinguished as Coli A, B, and C, 

 and Hueppe, the two latter showed practically no change, though some of 

 the reactions were delayed. Considerable variations in the type of colony 

 were observed, but this is quite usual. The four organisms showed very 

 varying resistance to the malachite-green, ffueppe and Coli B were very 

 susceptible, and had to be carefully acclimatised, while the other two found 

 no difficulty in development in presence of the dye. The susceptibility 

 appears, however, to have no bearing on the physiological change. 



The other two had, however, undergone exactly the same change as that 

 previously recorded, and the various colonies examined consisted of organisms 



