NONSPORE-FORMING BACTERIA 91 



tion, media in which Ps. aeruginosa had grown depressed the growth 

 of other microorganisms including S. marcescens, Ps. fluorescens, and 

 Saccharomyces cereviseae; spore formation by the last was favored 

 (762). 



The specific antagonistic action of Ps. aeruginosa upon various bac- 

 teria was found by early investigators to be due to the production of an 

 active heat-resistant substance (120, 299). By filtering the culture 

 through a Berkfeld, evaporating to a small volume, dialyzing through 

 a parchment membrane, precipitating with alcohol, and drying over 

 sulfuric acid, Emmerich and Low (236) obtained a preparation which 

 was designated as pyocyanase. It was soluble in water and highly bac- 

 teriolytic. 



Pyocyanase was at first looked upon as an enzyme belonging to the 

 class of nucleases. It was found to have, even in very low concentrations, 

 a marked destructive effect upon diphtheria, cholera, typhus, and 

 plague organisms, as well as on pyogenic streptococci and staphylococci. 

 It rapidly dissolved V . comma cells and in a few seconds rendered in- 

 active such bacterial toxins as that of diphtheria. Since the bacteriolytic 

 action of pyocyanase was in direct proportion to the time of its action 

 and concentration, and in inverse proportion to the numbers of bacteria 

 acted upon, its enzymatic nature was believed to be substantiated. The 

 preparation withstood heating in flowing steam for 2 hours. Other 

 proteolytic systems of bacteria are known to be resistant to high tem- 

 peratures and to remain active even when kept in a moist state for 1 5 to 

 30 minutes at 100° C. ( i ). Pyocyanase was believed to be transformed 

 in the bodies of animals into high molecular proteins which still re- 

 tained the bacteriolytic action of the free enzyme. 



Since the early work of Emmerich and Low, an extensive literature 

 has accumulated on the nature of pyocyanase. Its lytic effect has been 

 established against diphtheria (52), streptococci (237), meningococci, 

 the typhoid organism, pneumococci (yb(i)^P. festis ( 246) , Vibrio metch- 

 nikovi (501), V. comma (692), and many others (794). There has been 

 considerable disagreement, however, concerning the chemical nature 

 and therapeutic action of pyocyanase (234, 322), due largely to the 

 variation in the nature of the preparations obtained (540). Kramer 

 (501), for example, has shown that the activity of the substance de- 

 pends on three factors: nature of strain, not all strains being equally 



