Feeding defects of alcS mutants are related to alcaligin production. The bars indicate the mean diameters of growth stimulation zones in iron-restricted EDDA agar plates, including the 6-mm diameter of the sample wells, and the error bars indicate standard deviations (n =3). Iron restriction by EDDA chelation resulted in alcaligin production by alcaligin-positive indicator bacteria seeded into the agar. (A) Growth stimulation by 1.25 mM ferric chloride. (B) Growth stimulation by 300 μM alcaligin. Abbreviations for strains used are as follows: wt, B013N; alcS, BRM16; alcS alcA, BRM27; alcS alcA/alcA+, BRM27(pBB21); alcA, BRM26; alcA/alcA+, BRM26(pBB21).