[ 63 ] 



IV. 



ON A VIOLET COLOURING-MATTER AND ITS PRODUCTION 

 BY A CERTAIN BACTERIUM. 



By W. J. HARTLEY, B.A. 



[communicated by sir WALTER N. HARTLEY, F.R.S.] 



[Read May 20 : Published July 11, 1913.] 



In the course of an examination of the waters used in certain Irish creameries 

 a sample was examined in which a chromogenic bacterium of a briglit violet 

 colour was found. The sample was delivered at the Royal College of Science, 

 Dublin, on April 17th, 1912, from a creamery in County Wexford. On the 

 same day 0"1 and I'O c.c. were plated out in gelatine in the usual manner, 

 and incubated in the dark at 20° C. ; on April 23rd it was noticed that two 

 colonies had a distinctly blue appearance, and sub-cultures were made from 

 one of them. 



The cultural characters were found to be variable. For instance, gelatine 

 was sometimes liquefied in seven, sometimes in fourteen, and sometimes not 

 in twenty-one days. 



The thermal death-point after exposure to moist heat for one minute is 

 apparently between 50° and 55° C. Sub-cultures from a culture previously 

 heated to 50° C. produce little colour and liquefy rapidly ; otherwise lique- 

 faction rarely or never precedes colour-production. 



Colour-production varies curiously. Agar colonies show colour in 

 concentric rings. Agar streak-cultures usually produce colour on the 

 margin, spreading inwards and intensifying till the tenth day. Sometimes 

 colour is not produced for twenty-one days, and liquefaction may then 

 occur. 



Colour was not produced unless more water were present than was 

 sufficient for the growth of the organism. The addition of sterile water to a 

 well-grown, colourless, partly desiccated culture seventy-two days old, was 

 followed by colour and liquefaction in forty-eight hours. 



Experiments to find whether the colour is excreted or contained in the 

 organism were inconclusive. With the exception of the statement of Mace,' 



' Mace, Traite de Baetoriologie, 1897, pp. 849-853. 

 HCIENT. PROC. R.D.S., VOL. XIV., NO. IV, K 





