FIG. 2.

Iron-regulated expression and cotranscription of alcA, alcB, and alcC. Genetic maps of alcA′-′lacZ, alcAB′-′lacZ, and alcABC′-′lacZ translational fusions carried on the designated plasmids are shown. Deletions of the 105-bp NdeI-AseI fragment containing the alcA promoter-operator region shown in Fig. 1 are indicated (triangles). Levels of β-galactosidase expressed in wild-type B. bronchiseptica B013N containing alc′-′lacZ fusion plasmids in response to iron-replete (Fe+) and iron-depleted (Fe−) growth conditions are reported in Miller units (21) and are expressed as means of triplicate measurements (n = 3) ± standard deviations.