Waksman — 118 — Actinomycetes 



9.0; it is thermolabile and is destroyed by ultraviolet radiations. Ac- 

 tinomycetin, as well as the living S. albus, has a lytic action upon living 

 gram-positive and upon dead gram-negative bacteria. The bacteriolytic 

 properties of the living S. alhiis and of the actinomycetin preparation 

 upon dead or living cells of bacteria was said to be due to a lytic prin- 

 ciple, designated as actinozyme. 



Isolation of antihiotics.— The first true antibiotic of actinomycetes 

 was isolated in 1940 from a culture of Actinoviyces CStreptoviyces^ 

 antihioticus. This substance was designated as actinomycin (490). It 

 proved to be highly interesting from a chemical and biological point of 

 view and it affected a large number of bacteria, mostly the gram-positive 

 types. Unfortunately, actinomycin proved to be extremely toxic to the 

 animal body (491) and did not offer, therefore, any chemotherapeutic 

 potentialities. 



Later, two other substances, proactinomycin (129) and micromono- 

 sporin (468), were isolated. These agents had limited antibacterial 

 spectra and, for one reason or another, they too failed to offer promise 

 as chemotherapeutic agents. Later, other antibiotics were isolated. 

 Attention was concentrated upon the isolation of antibiotics active 

 against gram-negative bacteria, an acid-fast group of bacteria which in- 

 clude the tuberculosis organism. These substances varied greatly in 

 their antibiotic spectra, in their chemical properties, and in their in invo 

 activities. 



A number of antibiotics are now known to be produced by actino- 

 mycetes, as shown in Table 22. Some of the substances listed are, no 

 doubt, closely related to others or vary from them only in certain minor 

 properties. Some of these substances are produced by different organ- 

 isms; this is true, for example, of actinomycin, v/hich is formed by a 

 great variety of cultures (465, 505). Some organisms, on the other 

 hand, produce more than one substance; S. griseiis, for example, pro- 

 duces 2 forms of streptomycin, actidione, and an antibiotic present in 

 the mycelium of the organism, later designated as streptocin (466). 



Some of the antibiotics of actinomycetes are active largely on gram- 

 positive bacteria. Others are also active against gram-negative forms. 

 Some, like streptothricin, are active against fungi. Some, like actidione 

 and antimycin, are largely active upon fungi. Some, like neomycin 

 (471) and streptomycin are completely inactive upon fungi. Some are 

 active against trichomonads, as is the case of streptocin. Some are active • 

 against rickettsiae and even against certain viruses, including phages 

 (392). These antibiotics also vary gready in their toxicity to animals. 

 Some, like actinomycin and xanthomycin, are highly toxic. Others, 

 like streptomycin, aureomycin, and Chloromycetin, are relatively non- 

 toxic. 



The differences in antibacterial action are frequently quantitative 

 rather than qualitative. Streptomycin and streptothricin, for example. 



