THE PIGMENTS OF MICRO-ORGANISMS 391 



an acetyl group instead of a vinyl group on one of the 

 carbon atoms. Bacteriochlorophyll is probably carried 

 on different proteins in the Thiorhodacece, Athiorhodacece 

 and the green sulphur bacteria, since they give different 

 absorption spectra. C. diphtherice produces porphyrins, 

 possibly derived from cytochrome. 



Azotobacter chroococcum and CI. ivelchii produce 

 black melanin pigments from t^TOsine, whilst the latter 

 also forms a pigment of the thio -amino type. 



Actinomyces tvaksmanii is said to give an anthocyanin 

 pigment, but the chemical properties of the pigment 

 are not altogether those of an anthocyanin. A. coelicolor 

 and A. viola ceus-ruher give pigments which are blue in 

 alkaline solution and red in acid solution, closely resem- 

 bling azolitmin. 



Several phenazine pigments are known. Pj^ocyanin, 

 the blue, chloroform soluble pigment of Pseudomonas 

 ceruginosa (B. pyocyaneus) has the constitution 

 N 0- 



1 yi y[ ^' , or possibly a dimeric form of it. A 



N + 



N OH 



CH3 

 second, yellow pigment, a-hydroxj^phenazine, I I ll I 



N 



occurs in older culture of Ps. ceruginosa. Pyocyanin 

 can act as a hydrogen carrier in the reduction of cyto- 

 chrome, and can act as a hydrogen acceptor in the 

 formation of phosphoglyceric acid from glucose by the 

 action of the apozymase-cozjTnase system (see p. 202). 

 Pyocyanin is bactericidal (see p. 177). Pseudomonas 

 chloromphis yields a green, crystalline pigment, chloro- 

 raphin, which, on exposure to air, changes to the crystal- 

 line, yellow pigment, oxychlororaphin, m.p. 241° C. The 



