SUBSTANCES PRODUCED BY BACTERIA 163 



may be produced under certain conditions. It was excreted into the me- 

 dium as a leuco base. 



Pyocyanase is soluble in ether, benzol, benzene, and petrol ether. It 

 can be separated (370) into several lipoids, the action of which shows 

 slight variation. This preparation consists of a phosphatide, a neutral 

 fat, and a free fatty acid. The antibacterial properties have been attrib- 

 uted to the last constituent (410). A definite relation has been observed 

 between the number of double bonds and the activity of the substance 

 (SSy 409). According to Dressel (185), most fatty acids exert bacteri- 

 cidal and bacteriolytic effects upon gram-positive bacteria, whereas 

 gram-negative organisms are not lysed, Pyocyanase acts upon various 

 bacteria, including the colon-typhoid group, though the ability of the 

 substance to inhibit the growth of this group of bacteria has been denied 

 by some workers (370). 



Many commercial pyocyanase preparations have been found to be of 

 little practical value. This is believed to be due largely to a lack of recog- 

 nition of the importance of strain specificity, conditions of cultivation 

 of organism, and methods of extraction of the active substance (501, 



763). 



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

 and abundance of the pigment are also influenced by these conditions. 

 Keeping the organism for five 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 (129, 321, 522). 



Pyocyanin was first studied by Fordos in i860 (279). Since then 

 many contributions have appeared dealing with formation and nature 

 of this pigment. Several formulae have been suggested for pyocyanin 

 (452, 603, 913, 1006), one of which is shown in Figure 16. The struc- 

 ture of pyocyanin has considerable similarity to chlororaphin and io- 

 dinin, obtained from Chromobacterium {SSS^ SS^) ^^^ two synthetic 

 compounds, phenazine and acridine (919). 



Besides Ps. aeruginosa, spore-forming bacteria, including B. mesen- 

 tericus, were also found to produce antibiotic agents of a lipoid nature. 

 The cell-free filtrate of this organism killed diphtheria bacteria in 

 4 minutes (1016), but when diluted to i per cent it required 24 hours 

 to effect a kill. The substance was not affected by heating for 30 seconds 



