ESSENTIAL METALLIC ELEMENTS 



to 



tion existed between the amount of iron supplied in the medium and the 

 ability of Rhizohium trijolii to synthesize certain vitamins. In the pres- 

 ence of suboptimal concentrations of iron the addition of certain vitamins 

 replaced iron to a certain degree. A quantitative study of the ^ntamins 

 synthesized by Torulopsis utilis has shown the iron concentration to be 

 important (Lewis, 1944). Increased amounts of thiamine, riboflavin, 

 nicotinic acid, and pyridoxine were synthesized on media low in iron, while 

 the amounts of biotin, inositol and p-aminobenzoic acid were decreased. 



L) 10 15 20 



Mg. ferric sulfate per liter 



Fig. 14. The effect of iron [Fe2 (804)3] in overcoming the inhibitory action of copper 

 (CuS04-5H20) on the production of penicilUn by Penicillium chnjsogenum X-1612. 

 An amount of copper sufficient to inhibit peniciUin production entirely did not affect 

 the amount of growth. The fungus was cultured submerged in a lactose-starch- 

 dextrin-ranmonium sulfate medium for 7 days. (Curves drawn from data of Koffler 

 et al., Jour. Bad. 53 : 120, 1947. Pubhshed by permission of The Williams & Wilkins 

 Company.) 



There has been a great deal of interest in the effects of iron and other 

 metallic ions on various microbiological processes. Perlman et al. (1946) 

 have shown that the iron concentration is an important factor in citric 

 acid fermentation by Aspergillus niger. The optimum iron concentration 

 for citric acid production varied over tenfold for different strains of 

 A. niger. The effect of iron on penicillin production has been studied by 

 Kofl^ler et al. (1947), who concluded that the effect of the ash of corn steep 

 is due to iron and phosphate. Chromium increased penicillin production 

 above that obtained with iron and phosphate, presumably by neutralizing 

 the effect of other ions. Similarly an antagonism was shown to exist 

 between copper and iron. The antagonistic effect of copper and iron on 

 the production of penicillin by Penicillium chrysogenum X-1612 is shoA\Ti 

 in Fig. 14. 



