MICROBIAL ANTAGONISMS AND PRODUCTION OF ANTIBIOTICS 



9 



expression of our luck oi knowledge of the 

 nutrition of the organisms that we so label 

 (Gaullery, 1902). The pathogenic actino- 

 mycetes all fall in the group of facultative 

 parasites, as amply illustrated in Volume I, 

 Chapters 17 and 18, and in \\)lume II, 

 Chapters 2 and 3. 



Antagonism 



Antagonism is the phenomenon hy which 

 one living organism inhibits the growth of 

 another one by creating an unfavorable set 

 of conditions such as the production of toxic 

 chemical substances. In the case of micro- 

 organisms, antimicrobial sul)stances may be 

 of two types: (1) chemical compounds toxic 

 in high concentrations, such as certain acids 

 (nitric, sulfuric, acetic, butyric, lactic, fu- 

 maric) and alcohols (ethyl, butyl); (2) 

 chemical substances toxic in xcry dilute 

 solutions. These are called antibiotics and 

 are usually selective in their antimicrobial 

 action, being much moi-e active against 

 certain microorganisms than against others. 



The phenomena of antagonism among 

 microorganisms, notably among actinomy- 

 cetes and bacteria, ha\-e been examined in 

 detail by Greig-Smith (1917), Millard and 

 Taylor (1927), Alexopoulos and Ilerrick 

 (1942), Waksman (1937, 1945, 1947), Florey, 

 Chain et al. (1949, 1952), and Rehacek ct al. 

 (1960). The ecological aspects of microbial 

 antagonisms have been reviewed by Brian 

 (1957) and Waksman (19(U). In discussing 

 the phenomena of symbiosis and antagonism, 

 one cannot overlook the phenomena of 

 adaptation (Stanier, 1953). 



Definition of an Antibiotic 



The word antibiotic is now an integral 

 part of the vocabulary of the layman as well 

 as of the scientist and the medical man. Like 

 any term that is employed widely, however, 

 the word is often used loosely. 



As pointed out previously, the word 

 antibiosis was used in 1889 by Vuillemin to 

 describe a type of association in which one 



living creature was destroying another in 

 order to sustain its own life. This broad con- 

 cept changed in time, and Papacostas and 

 Gate (1928) limited the meaning of the word 

 in their re\'iew of the problem of bacterial 

 associations. According to them, when one 

 organism was exerting an injurious effect 

 upon another in vitro, the type of association 

 should be called "antibiosis"; when the 

 same phenomenon occurred in vivo the 

 association should be called "antagonism." 



The noun antibiotic was introduced by 

 Waksman in 1942 (1947) to designate a 

 chemical substance of microbial origin which 

 had the property to inhil^t the growth of 

 microorganisms. Waksman in 1947 published 

 the following definition of the word: "An 

 antibiotic is a chemical substance, produced 

 by microorganisms, which has the capacitj' 

 to inhil)it the growth and even to destroy 

 bacteria and other microorganisms." Bene- 

 dict and Langlykke, later in 1947, modified 

 this definition to comprise substances which 

 act upon certain organisms at least, in very 

 dilute solutions. This ([ualification avoided 

 the inclusion among antibiotics of such 

 products of microbial metabolism as acetic 

 acid and ethyl alcohol. Waksman recognized 

 the \alidity of this argument and corrected 

 his original definition in 1951. 



Se\'eral workers suggested that the word 

 antibiotic should not be limited to substances 

 produced by microorganisms. They felt that 

 the use of a specific term for the product of 

 microorganisms would seem to imply that 

 microorganisms have a special property that 

 other organisms do not have. Since higher 

 plants and animals are known to produce 

 substances similar to and in certain cases 

 identical with antibiotics, why not apply 

 the term to all substances of biological origin 

 which have the aforementioned properties? 



Mascherpa (1954) proposed the following 

 definition: "Antibiotics are substances spon- 

 taneously produced by living organisms (or 

 synthetically obtained, l)ut with analogous 

 structui'e to that of natural products) en- 



