Early Stages in the Metabolism of Iron 



201 



Table 5. Relationship between added iron and itoic acid 



FORMATION BY B. SubtUis 



The initial iron contamination was eliminated by oxine treatment of the 



medium prior to the addition of the remaining mineral elements. Itoic 



acid was determined as the ferric complex 



Nutritional Availability of Iron Complexed by Itoic Acid 



The growth response of B. subtilis to ferric chloride and to an equivalent 

 amount of iron supplied as Fe+++ — Itoicg is given in Table 6. In the early 

 phase of growth, free iron appeared to be somewhat more available to the 

 organism; after 40 hr this discrepancy had disappeared and the complexed 

 form of iron always provided slightly superior cell yields. It is also interesting 

 to note that in the presence of externally added itoic acid, better growth was 

 obtained after a certain stage in the culture after which contaminating iron in 

 the medium would be expected to become limiting. This suggests that itoic 

 acid increases the availability of the trace amounts of iron that are present. 



Table 6. Growth response of B. subtilis to 



FERRIC chloride AND TO IRON SUPPLIED AS THE 



ITOIC ACID COMPLEX 



Duplicate growth flasks received the following additions (added 

 as solutions previously sterilized by ultrafiltration): 179 m//- 

 mole FeCl3-6H,0 and 539 m//mole itoic acid; 539 m//mole 

 itoic acid; 179 ni/imole FeCla-eHjO and none (control). Sterile 

 distilled water was added to give a final volume of 10 ml and each 

 flask was then inoculated with a very dilute suspension B. subtilis 



Metabolism of Itoic Acid in the Presence of Iron 



Table 7 records the result of adding excess iron to a culture of B. subtilis 

 which contained a high level of pre-formed itoic acid. It is apparent that, in 

 the presence of iron, the organism possesses a powerful mechanism for the 

 elimination of itoic acid from the medium. From the previously determined 



