SUBSTANCES PRODUCED BY BACTERIA 181 



stance into solution. The active substance was again dissolved in alcohol 

 and taken up in ether. The ether solution was washed with water, evapo- 

 rated, and dried. One liter of a 30-day-old culture of B. mesentericus 

 gave 1 62 mg. of petrol-ether-soluble fatty acids and an oily substance 

 of a brownish color. It was neutralized with NaOH solution and tested. 

 The extract diluted to 1:7,500 killed diphtheria} a 1:1,000 dilution 

 was required to kill staphylococci. Iso-valerianic acid and oleic acid, 

 isolated from this material, had a similar bactericidal action. Weaken- 

 ing of the substance by heating was demonstrated and was believed to 

 be due to a break in the double bond of the oleic acid. 



E. coli exerts an antagonistic effect in vivo when injected subcutane- 

 ously or when used for feeding. It produces (367, 369) a thermolabile 

 substance that was considered to be a lipoid in character. However, 

 some of the antibiotics of E. coli, namely the colicines, appear to be 

 definitely proteins or polypeptides. 



Pyocyanin is a dark blue pigment, red in acid solution, m.p. 133° C, 

 water soluble and amphotheric. It is extracted with chloroform, then 

 reextracted by acidulated water. It is characterized by a wide antibiotic 

 spectrum and high toxicity to animals. This pigment was first studied 

 by Fordos in 1 860 (277). Since then many contributions have appeared 

 dealing with formation and nature of this pigment. Several formulae 

 have been suggested for pyocyanin (461, 935, 1036), one of which is 

 shown in Figure 18. The structure of pyocyanin has considerable simi- 

 larity to chlororaphin and iodinin, obtained from Chromobacterium 

 (596), and two synthetic compounds, phenazine and acridine (939). 

 Since Ps. aeruginosa is an extremely variable organism, the nature and 

 abundance of the pigment are variable. Keeping the organism for 5 

 minutes at 57° C. or cultivating it in liquid egg-albumin has been found 

 to result in destruction of some of its pigment-producing properties 



(330,557). 



Hemipyocyanin is found in old cultures of Ps. aeruginosa (843) and 

 is synthesized (1036) from pyocyanin. It is a yellow pigment, m.p. 

 158° C, with basic and phenolic properties. It is moderately bacterio- 

 static and strongly fungistatic (883). 



Prodigiosin is produced by S. marcescens. It is insoluble in water and 

 is active against B. anthracis (1035). 



