MINIIHAI. Ml.l "AHol.ISM AND I'.IM'l.Cr Ol' SAI/I'S ( »\ CIJOW'IMI 



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chemical and nut ril ioiial .^liidics ol' metals 

 ill \arinus metabolic I'eactions. .Mdlylidc- 

 iium. coppcM', and iron are said to lie mo,si 

 closely assoi'iated with elect I'ou-t ranst'errinu; 

 systems. ""Phese metals are not reiniired spe- 

 eilieally t'oi' the comlMnation of substrate to 

 protein, l)iit ratht>r t'unction as "el(M'tron 

 couplers" from one protein system to an- 

 otlu'r. Matiuesium and, to some tlej2;r(H', man- 

 ijanese function primarily in ij;roup transfer 

 i-eactions. particularly those iin-olvinjj; phos- 

 phate. Manganese and, to a lessor dosroo, 

 zinc and magnesium, predominate in general 

 (Mizymatic decarboxylation and hydrolysis 

 reactions. 



Some metals form a stable metal-protein 

 complex and in such cases are considered to 

 be specific. In other cases, there are enzjmies 

 in which the metal may easily be separated 

 from the protein and be replaced in function 

 by a metal of equivalent \'alency. 



Metals may also play an important role 

 as a structural part of a specific molecule. 



Ivxamples of this kind are the iron in the 

 antibiotic gi'isein, cobalt in \ itamin li|j , and 

 iron ill a st rept oiiiycete |)igmeiit known as 

 ferroxci'din. 



Outward manifestations of the effects of 

 metals u|)on a microorganism can be ob- 

 ser\-ed as changes in giowth, sporulation, 

 and ability to utilize ceitain substrates as 

 \v(»ll as the formation of metabolic products 

 such as pigments, antil)iotics, and vitamins. 

 'The effect of metals on streptomycete mi- 

 t lit ion has been studied largel}^ from the 

 point of \iew of antibiotic production. It is 

 conunon practice to use complex organic 

 media to which are added mineral salt solu- 

 tions containing the metals considered to be 

 beneficial for growth and antibiotic forma- 

 tion. The metals usually used are potassium, 

 magnesium, iron, zinc, copper, calcium, and 

 manganese. Streptomycin formation by S. 

 griseiis has been studied more than any other 

 reaction in connection with the effects of 

 metals in the actinomycete system. 







