ANTIBIOTICS 17U 



N OH 



%/%^/\/ 



Pyocyaiiin, which is thermostable, has strong bacterio- 

 static power against Gram -positive and Gram -negative 

 bacteria and comparatively little effect against moulds 

 or yeasts. Hemipyocyanin is less active against bacteria 

 but considerably more active against yeasts and fungi. 

 The similar pigment, chlororaphin, formed by Ps. chloro- 

 raphis (see p. 391), is also somewhat inhibitory to bacteria. 



In virtue of its oxonium structure, pyocyanin is 

 known to act as an oxygen carrier in the oxidation of 

 a-hydroxyglutaric acid to a-ketoglutaric acid in presence 

 of a dehydrogenase occurring in animal tissues. It is 

 possible that the antibiotic effect of pyocyanin is due to 

 interference in some such process in bacterial metabolism. 



Pyocyanin is highly toxic to animals as w^ell as being 

 bactericidal ; hemipyocyanin is much less toxic and has 

 about the same bactericidal power as the f la vines. It 

 has no staining properties. 



Spinulosin. — P. sjnmdosmu gives rise to the red 

 pigment . spinulosin, 3 : 6-dihydroxy-4-methoxy-2 ; 5- 







il 



toluqumone, , which is hydroxy-fumigatin 







(see p. 163). It is a weaker bacteriostatic agent than 

 fumigatin, being active against Gram-positive organisms 

 at concentrations of 1 in 6000 to 1 in 10,000. The loss 

 in activity as compared with fumigatin is attributed 

 to the additional hydroxyl group since, in a series of 

 tolquinone derivatives, those members containing hy- 

 droxyl groups are less active than those without. 



