92 BACTERIA AS ANTAGONISTS 



effective j composition of medium, glycerol-containing media being 

 most favorable J and method of extraction of active substance from cul- 

 ture media. 



The enzymatic nature of pyocyanase was not universally accepted, 

 largely because of the thermostability of the substance (489). Dietrich 

 (171) ascribed the action of pyocyanase to a change in osmotic pressure, 

 Raubitchek and Russ (733) emphasized that the solubility of the sub- 

 stance in ether, chloroform, or benzol is not indicative of an enzyme, 

 nor is the fact that temperatures of o to 37° C. fail to influence its ac- 

 tivity {55, 185,409,669,919). 



Ps, aeruginosa was found to produce (409), in addition to pyocya- 

 nase, a blue pigment, pyocyanin. Both substances possess lytic proper- 

 ties, 1:1,000 dilution of the pigment being able to lyse E. coli in 

 6 hours (366). The pigment was believed (501) to act only on gram- 

 positive bacteria. Pyocyanin was said (407) to be more effective in 

 younger cultures, and pyocyanase in older. 



In order to test the action of Ps. aeruginosa upon other bacteria, 

 Kramer (501) placed a drop of a suspension of this organism upon a plate 

 inoculated with M. tuberculosis or with V. metchnikovi. In 24 hours, a 

 sterile zone surrounded the colony of the antagonist, the width of the 

 zone depending upon the moisture content of the medium, the degree 

 of diffusion of the active substance, its concentration, and the resistance 

 of the test bacteria. When the two pathogens were inoculated into liquid 

 media and the antagonist was introduced simultaneously or within 24 

 hours, the latter had a decided bactericidal effect. No bactericidal fil- 

 trate could be obtained. These results were confirmed (634, 919), the 

 conclusion being reached that the active molecules do not pass through 

 the ultrafilter (949). Pyocyanin had a bactericidal action also upon 

 S. hemolyticus, S. albus, S. aureus, C. difhtheriae, M. tuberculosis, V. 

 metchnikovi, and the Y-Ruhr bacillus, but not upon P. vulgaris, E. coli, 

 or the typhoid organism. In general, gram-positive bacteria were 

 largely affected. 



More recently, Schoental (809) succeeded in isolating three anti- 

 bacterial substances from the chloroform extracts of cultures of Ps. 

 aeruginosa: (a) a blue pigment, pyocyanin j (b) a yellow pigment, 

 tf-oxyphenazine, a derivative of pyocyanin j and (c) an almost colorless 



