The accumulation of phenolic acids and coproporphyrin by iron-deficient cultures of Bacillus subtilis

Phenolic acids started to accumulate before coproporphyrin in cultures of B. subtilis grown under conditions of iron deficiency. If hemin synthesis was reduced or prevented, both phenolic acid accumulation and the iron-uptake capacity of the cells were decreased. A mutant strain unable to synthesize hemin accumulated phenolic acids only if the culture medium was extracted with hydroxyquinoline to remove residual iron. A mixture of iron and 2,3-dihydroxybenzoic acid was more effective than iron alone in reducing coproporphyrin accumulation by iron-deficient cultures. It is suggested that phenolic acids are produced by B. subtilis to solubilize the iron in the medium; under iron deficiency the biosynthetic pathway for phenolic acids is derepressed so that residual iron in the medium will be made available to the cell as the phenolic acid: iron complex.