C H A V I i: \{ I 1 



Antagonistic Properties 



Phonoiiiena of Association and Antago- 

 nism 



Soils and water iiasins arc iiihabilcHl by 

 mixed inicrohioloiiical populations. .Vnioiig 

 the nuMiihors of these populations numerous 

 associations and antagonisms occur. Com- 

 plex populations also occur in other sub- 

 strates, as in human and animal digestive 

 tracts, where they may be responsible for 

 certain mixed infections. 



I'asteiH", the biochemist, and DeBary, the 

 botanist, were the first to emphasize the 

 significance of possible antagonistic relations 

 among different microorganisms li\'ing in 

 such mixed populations. When two organ- 

 isms were grown on the same substrate, one 

 usually was found, sooner or later, to over- 

 Avhelm and e\-en bring about the death of 

 the ()th(M'. Such antagonistic activities em- 

 brace phenomena other than mere competi- 

 tion for or exhaustion of nutrients: they were 

 found to be due largely to the formation of 

 specific chemical substances (antil)iotics) 

 responsible for these effects. 



The terms "antagonism" and "antibiosis" 

 usually refer to the rexhiction in growth and 

 activities of organisms living in association. 

 The organisms thus affected may respond 

 bj^ exhibiting temporary or permanent modi- 

 fications in their physiological characteris- 

 tics; their morphology may l)e changed; a 

 reduction in virulence may also result. Se^'- 

 eral tj^pes of antagonism are now recognized: 

 1. Antagonism in vivo versus antagonism in 

 vitro. 2. Bacteriostatic or fungistatic, bac- 



tericidal oi- fungicidal, and lytic effects. 3. 

 Antagonism of function versjis antagonism 

 of growth. 4. Direct and indirect antagonism. 

 5. One-sided or two-sided antagonism. 6. Iso- 

 antagonism and heteroantagonism, namely, 

 antagonism between strains of the same 

 species and antagonism among different 

 species. 



Among the xarious types of antagonism, 

 the most definite and best understood are 

 those that result in the formation of anti- 

 biotic substances, formerly spoken of as 

 toxins, lysins, or bacteriolysins. The physi- 

 cal, chemical and biological properties of 

 these substances vary greatly. Some are de- 

 stroyed by boiling, others on exposure to 

 light. Some are resistant to heat and to ultra- 

 violet rays. Some are soluble in water, others 

 in special solvents. Some are highly toxic 

 to animals, others are relati^Tly nontoxic. 



Numerous early investigators observed 

 the depressive effect of fungi upon bacteria 

 and vice versa. It is sufficient to mention 

 the observations of Tyndall (1876). How- 

 ever, the first well-recognized antibacterial 

 preparation was that of pyocyanase, pro- 

 duced by Ps. aeruginosa, formerly known as 

 B. pyocyaneus. Emmerich and Low (1899) 

 considered pyocyanase to be an enzyme sys- 

 tem. Emmerich and Saida (1900) actually 

 used it to destroy (dissolve) tubercle bacilli. 

 Subsequent to these early studies, an ex- 

 tensive literature accumulated on the pro- 

 duction of antibacterial substances by bac- 

 teria, culminating in the treatise by 



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