Formation of the enzymes synthesizing 2,3-dihydroxybenzoic acid (DHB) inBacillus subtilisis repressed by iron. DHB does not appear to be involved in regulating its own biosynthesis. Hemin may be involved in regulating DHB synthesis. DHB synthetase is inhibited by severalm-substituted benzoic acids. The inhibitors do not affect the growth rate ofB.subtilisand DHB appears not to be necessary for growth under the conditions used. Inhibition of DHB synthesis during growth under iron-deficient conditions reduces the iron uptake capacity ofB.subtilis.