THE PIGMENTS OF MICRO-ORGANISMS 389 



II. Insoluble in water — 



{a) Soluble in other solvents, e.g. brown 

 pigment of Flavobacteriiun sicaveolens. 



(6) Insoluble in other solvents, e.g. the 

 black and brown pigments of Actino- 

 myces, Azotobacter cJiroococcum ; the 

 melanin from Ps. ceruginosa. 



Certain organisms, notably of the genera Pseudomonas 

 and Acetobacter, are capable of oxidising tyrosine, quinic 

 acid and similar substances in the medium with formation 

 of black or brown pigments. 



The constitution of a few of these pigments has been 

 established completely, and fragmentary knowledge is 

 available about some others. Prodigiosin, 020^^250X3, 

 the red pigment of Sermtia viarcescens (B. prodigiosus) , 

 has been shown to have the structure : — 



^^OCHa 



Violacein, C42II35O5X5 or C50H42O8N6, the violet pigment of 

 Chr. violaceum, contains one or more pyrrole nuclei with 

 hydrocarbon side chains, being similar in constitution to 

 prodigiosin. 



The purple bacteria of the genus RJiodovibrio contain 

 complex mixtures of carotenoid pigments, including 

 rhodopin, containing one hydroxyl group and two double 

 bonds ; rhodovibrin, a polyene alcohol ; rhocloviolascene, 

 C42H60O2J containing two methoxyl groups and thirteen 

 double bonds, probably having the structure : — 



