30 



NATURE, FORMATION, AND ACTIVITIES 



against several strains of S. lavendiilae, but 

 inactive against others. This was true of 

 some other forms. In no case was one strain 

 autoinhibited. 



This should not be considered, however, 

 as justifying the broad generalization, much 

 emphasized by Krassilnikov (1950, 1951, 

 1958), that because some antibiotic-produc- 

 ing organisms are resistant to their own 

 antibiotics the general conclusion may be 

 reached that antibiotics form a kind of 

 defense mechanism for different micro- 

 organisms living in mixed populations. It 

 must rather be looked upon as an isolated 

 instance in a complex group of relationships 

 among organisms li\ing in mixed populations 

 (Waksman, 1956; see also Okami et ai, 1960). 



Alusilek (1957), for example, demon- 

 strated that the growth of *S. aurcofaciens 

 on an agar medium was not inhil)ited l)y the 

 antibiotics of the tetracycline group, but 

 was inhibited by other antibiotics. This was 

 true also of an actinomycin-producing 

 actinomycete that was not inhil)ited by its 

 own antibiotic. On the other hand, S. 

 griseus, S. rimosus, and erythromycin- 

 producing actinomycetes were not inhibited 

 by the antibiotics produced by these or- 

 ganisms or by similar antibiotics; at the 

 same time, they were not inhibited by 

 \'arious antibiotics produced by different 

 other organisms. The conclusion was reached 

 that the finding of resistance of an unknown 

 actinomycete to a certain antibiotic cannot 

 in itself serve as a method for identifying 

 actinomycetes producing known antibiotics. 



Other Antimicrobial Systems 



Certain actinomycetes were found capal)le 

 of producing substances that possess marked 

 bacteriolytic properties. These were quite 



distinct from phages, although some of them 

 exerted an autolytic effect; they were known 

 long before the true nature of the antibiotics 

 became recognized. This is true of the 

 "bacteriolytic enzyme of Sti'eptothrix" 

 studied by Gratia (Gratia and Dath, 1924- 

 1927) and designated by Welsch (1937) as 

 actinomycetin. It is also true of the "actino- 

 myces lysozyme," recognized by Kriss 

 (1939) and by Krassilnikov and Koreniako 

 (1940). Welsch et at. (1955) later isolated 

 frcjm the actinomycetin preparation several 

 substances, one of which was designated as 

 actinozyme; another was designated as 

 actinolysin, and was active against both 

 dead and living bacterial cells. Whether 

 these substances should be considered as 

 enzyme systems, and more specifically, 

 autolytic or generally lytic enzymes, or 

 whether they should be considered as true 

 antibiotics is a subject for further study. 

 Here one approaches the borderline of 

 biological systems that may be considered 

 either antibiotic or enzyme, or even vitamin, 

 since some of the antibiotics have, in certain 

 concentrations, a definite growth-promoting 

 effect upon lower and higher forms of life. 



Numerous other preparations possessing 

 antil)iotic properties have been isolated from 

 cultures of actinomycetes. These range from 

 well defined compounds such as the phena- 

 zines ("^'agishita, 1960) to crude preparations. 

 In many cases the information is so limited 

 that it is difficult to place the preparation in 

 one or another of the above groups. Further 

 study of many of these preparations may 

 have been abandoned, since no practical 

 significance could be attached lo them. These 

 substances are listed in Part B of this 

 volume. 



