180 CHEMICAL NATURE OF ANTIBIOTIC SUBSTANCES 



The broth culture of the organism may also be first extracted with 

 ether, giving pyocyanase, and the residue treated with chloroform, 

 yielding pyocyanin. The solution left after the removal of the blue 

 chloroform extract may be again treated with ether, giving a yellow 

 pigment, which also has some activity (529). This pigment is a deriva- 

 tive of pyocyanin and is often designated (1036) as hemipyocyanin. It 

 may also be obtained by acidifying pyocyanin with acetic acid and heat- 

 ing. The fluorescin remaining in the culture after the ether and chloro- 

 form extraction was found to be inactive. In old cultures, pyocyanin is 

 changed into a brown pigment, pyoxanthose. A fourth pigment, which 

 is yellow in transmissible light and fluorescent-green in reflected light, 

 is produced under certain conditions. It was excreted into the medium 

 as a leuco base. 



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

 (766). It can be separated 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 

 attributed to the last constituent (421 ). A definite relation has been ob- 

 served between the number of double bonds and the activity of the sub- 

 stance (59, 420). According to Dressel (197), most fatty acids exert 

 bactericidal 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 (372). 



B. mesenter'icus and other spore-forming bacteria also produce anti- 

 biotic agents of a lipoid nature. The substance is not affected by heating 

 for 30 seconds at 100° C. but is weakened at 1 15° C. for 10 minutes. It 

 is considered similar in its bactericidal properties to pyocyanase. 



Alcohol and acetone extracted from B. mesentericus a weakly active 

 substance (419) that diffused through a cellophane membrane and 

 could be partly absorbed on a Berkfeld filter. When shaken directly 

 with ether, the culture lost its antibacterial properties. The ether extract 

 was concentrated and ammonia added, and the solution was treated with 

 50 per cent alcohol. The alcohol was then removed, and the residue was 

 acidified and treated with petrol ether, which brought the active sub- 



