140 



THE ACTINOMYCETES, Vol. I 



cent. Growth was not affected at concentra- 

 tions lower than 0.009 M but was inhibited 

 at that and higher concentrations. 



Chahipka (1957) found that of the various 

 ions tested (K, Na, Mg, Ca, Fe, and Zn), 

 only K (0.05 M) caused a significant in- 

 crease in the mycelial mass of S. griseus 

 and in protease formation. According to 

 Saunders and Syh-ester, Zn, Cu, Fe, Mg, and 

 Mn were necessary for optimum streptomy- 

 cin production. 



Metals had a beneficial effect on growth 

 and streptomycin production also in com- 

 plex media. Spilsbury used a peptone-meat 

 extract medium. The ions of lead, tin, ura- 

 nium, vanadium, cerium, strontium, chlorine, 

 iodine, and fluorine had no appreciable ef- 

 fect at any concentration employed. Slight 



stimulation of growth appeared to result 

 from ions of bromine at 2 parts per million, 

 zirconium at 10 parts per million, and all 

 concentrations of molybdenum employed. 

 Bismuth and lithium were slightly toxic at 2 

 parts per million; aluminium, cobalt, and 

 nickel were toxic at 10 parts per million; 

 cadmium proved to be extremely toxic at 

 all concentrations employed. The metals 

 most likely to prove worthy of investigation 

 were considered to be copper, iron, manga- 

 nese, zinc, and molybdenum, together with 

 the major salt constituents, notably sodium 

 nitrate, potassium phosphate, and magne- 

 sium sulfate. Tryptophan was shown to be 

 essential in the early stages of development. 

 It is of further interest to note that whereas 

 copper and iron caused an increase in growth, 



PARTS PEH MILLION OF METAL ADDED. 



Figure 67. Effect of copper, manganese and molybdenum on dry weight of S. griseus (Reproduced 

 from: Spilsbury, J. F. Brit. Mycol. Soc. Trans. 31: 217, 1948). 



