164 



THE ACTINOMYCETES, Vol. I 



mj^cetes to antibiotics produced b}^ other 

 organisms has been used as a method of se- 

 lecting and identifying such cultures. A cer- 

 tain culture may be sensitive to its own anti- 

 biotic to only a limited degree, but it may 

 be much more sensitive to other antibiotics. 

 Some strains of *S'. griseus, however, have 

 been found to be much less sensiti\'e to strep- 

 tomycin than are many other strains. Ex- 

 posure to streptomycin has been used as a 

 method of selection of new cultures, pre- 

 sumably higher-yielding types. 



An examination of data on the efficiency 

 of conversion of substrate to streptomycin 

 indicates that approximately 15 per cent of 

 the carbon added to the medium, either as 

 carbohydrate or as glycerol, may be con- 

 verted to streptomycin. The actinomycetes 

 producing chlortetracycline and chloram- 

 phenicol are also capable of incorporating 

 into the respective antibiotics substantial 

 quantities of the chloride ion present in the 

 medium. It is also probable that the grisein- 

 producing strains of S. griseus do likewise 

 with iron. Gottlieb and Anderson (1947) 

 have shown that the peak of streptomycin 



production lagged behind the growth peak. 

 The presence of oxygen was essential for 

 streptomycin synthesis (See also Woodruff 

 and Ruger, Eiser and ]\IcFarlane, Christen- 

 son et aL). 



The effect of nutrition of S. griseus upon 

 streptomycin production has been studied 

 by Bermett (1947). The effect of different 

 amino acids on the biosynthesis of strepto- 

 mycin is illustrated in Table 41. 



The biosynthesis of chlortetracycline by 

 *S'. aureofaciens has been studied by DiMarco 

 (1956), and of erythromycin by Corum et al. 

 (Table 42). The effect of specific nutrients 

 upon the formation of different actinomy- 

 cins and upon the constituent forms of the 

 same actinomycins has been examined by 

 Brockmann and his group, by Schmidt-Kast- 

 ner, and by Katz et al. (1958). 



Hunter et al. have shown, by the use of 

 C''*02 , that the carbon of the guanidine side 

 chains in streptomycin is derived largely, if 

 not entirely, from COo . Further information 

 on the mechanism of biosynthesis of antibi- 

 otics has been given hy Gwatkin, Herold 

 et al., Petty and Matrishin, Yagashita and 



Table 41 

 Effect of different amino acids on growth and streptomycin production by S. griseus (Spilsbiiry) 



