GROUP FORMING A PINK OR RED PIGMENT 635 



Pathogenicity. — Non-pathogenic to man and animals. 



Chr. janthinum, found in water and soil ; is said to be motile by one or two polar flagella. 

 Colonies on agar are at first milky white, but later become violet. Liquefaction of gelatin 

 is slow. On broth it forms a violet siurface pellicle. Optimum temperature 30° C. 

 It is doubtful whether this organism is a distinct species. 



Chr. amethystium is a non-motile bacillus found in water. On agar the growth is 

 first non-pigmented, later it assumes a dark violet colour with a wrinkled surface of metallic 

 lustre. Gelatin is liquefied ; a violet surface pellicle forms on the liquid. In broth a 

 surface pelUcle appears ; the fluid itself is coloured brown. Optimum temperature 30° C. 



Chr. coeruleum is said to be motile by polar flagella. Colonies are spreading and of 

 a bluish-grey colour. Slow liquefaction of gelatin. Greyish surface pellicle on broth. 

 Milk is rendered sky-blue at the surface, and is digested with an alkaline reaction. The 

 pigment is soluble in water and alcohol, but. not in ether or chloroform. Optimum tem- 

 perature 30° C. 



Group Forming a Pink or Red Pigment. — The most important member of this 

 group is Chr. prod-igiosum. It was first demonstrated by Bartolomeo Bizio in 

 1823 as a cause of " bleeding polenta " (Breed and Breed 1924). Infections of 

 meat, fish, bread and other articles of food with this organism from time to time 

 give rise to alarm. Klein (1894) describes an instance where the food in a large 

 mercantile establishment in London became contaminated with it. In spite of 

 the fact that the residents consumed pink meat for some days, they suffered 

 from no apparent ill-effects. The pigment is soluble in absolute alcohol, ether, 

 chloroform, benzol, and carbon disulphide, but is insoluble in water. An alcoholic 

 solution when acted on by mineral acids is turned first carmine-red, then reddish- 

 violet. Alkalies ivin it brownish-yellow, and chlorine water, after turning it 

 reddish-brown, then golden -yellow, finally decolorizes it. In the spectrum, blue 

 and violet are completely absorbed, and an absorption band is seen in the green. 

 Wrede (1930) gives its empirical formula as C20H25N3O, and says that only one 

 of the nitrogen atoms will combine with acids. The pigment is destroyed in a 

 few days by sunlight. It is very resistant to reduction, but is fairly easily oxidized. 

 In synthetic media it is formed only in the presence of magnesium sulphate and a 

 phosphate, preferably potassium phosphate (Kuntze 1900, and Sullivan 1905-06). 

 Its formation is said to be inhibited by the presence of calcium salts (Bordet 1930). 

 It is produced most readily at 22° C, and according to Amako (1930) there is a 

 close parallelism in cultures between the catalase content and the amount of pigment 

 formed. 



Hefferan (1904), whose detailed study is one of the most valuable on this 

 group of bacteria, proposed the following classification. 



Pigment insoluble in water : 



Group I. Chr. prodigiosum, Chr. indicum, Chr. kielense, etc. Pigment 

 red at first, later becomes darker — carmine or violet-red. 



Group II. Chr. ruhricxim, Chr. ruber, etc. Develop more slowly. Pig- 

 ment is orange-red or yellow-red, never becoming darker. 



Group III. Chr. mycoides roseum, etc. Pigment is salmon-pink, coral- 

 pink, rose, or flesh-coloured. 



Pigment soluble in water : 



Group IV. Chr. lactis erythrogenes, Chr. rubefaciens, etc. Eose-red pig- 

 ment. 



