FIG. 3.

alcR-dependent induction of alc operon transcription. β-Galactosidase reporter activities associated with expression of the alcA::mini-Tn5 lacZ1 fusion element of BRM1(pRK415) were compared with those of the isogenic ΔalcR1 derivative BRM13 carrying the control plasmid vector pRK415, the alcR⁺ plasmid pRK15, or the ΔalcR1 mutated plasmid pRK16. β-Galactosidase activities were measured for cells cultured in iron-replete SS medium or in iron-depleted SS medium supplemented with 20 μg of purified alcaligin/ml. β-Galactosidase activities are expressed in Miller units (means ± 1 standard deviation; n = 3). Solid bars, iron-replete cultures; hatched bars, iron-depleted cultures supplemented with alcaligin.