1 64 ANTISEPTICS 



VIII. ANTAGONISTIC SUBSTANCES FROM MICROORGANISMS 



Just as higher ammals are protected against invasion 

 of microorganisms by the secretion of antibodies, lyso- 

 zymes, and the bactericidal compounds of blood, saliva 

 and milk, so some microorganisms prevent the intrusion 

 of others into their ''Lebensraum" by secreting toxic 

 substances. Certain notable antagonisms between diff- 

 erent species have been known for a long time. As early 

 as 1887, Garre reported the inhibition of staphylococci 

 and typhoid bacteria by certain fluorescent species. The 

 pyocyanase of Pseudomonas aeruginosa {pyocyanea) 

 has been studied very extensively. In recent years, much 

 attention has been paid to antibiotic substances from mi- 

 croorganisms in the hope that they might be useful in 

 chemotherapy (see review by Waksman, 1941). This hope, 

 however, had to be abandoned in the case of most of 

 these substances because of their toxicity to man. Only 

 gramicidin and penicillin have been retained on the list 

 of the probably useful bacterial products but the search 

 for similar compounds continues. 



The long list of organisms which produce substances 

 toxic to other microorganisms includes hyphomycetes, 

 actinomycetes, sporulating and non-sporulating bacteria, 

 but no yeasts and no protozoa. While most groups of 

 microorganisms are represented in this list, there are 

 only a few species in each group. 



Concerning the chemical nature of antibiotic agents, 

 much remains to be investigated. There is enough evi- 

 dence, however, to state that they belong to quite dif- 

 ferent chemical groups. Dubos (1935) described an 

 enzyme, which dissolves the capsule of pneumococci and 

 is so specific that it attacks only Type III. On the other 

 hand, the substance called pyocyanase, which was as- 

 sumed to be an enzyme, is probably a lipoid. Gramicidin 



