FIG. 4.

Alcaligin inducer requirements of B. pertussis UT25 and B. bronchiseptica B013N mutant AlcR proteins produced from reciprocally mutated alcR alleles borne on multicopy plasmids. (A) alcA::mini-Tn5 lacZ1 transcriptional activities were monitored in strain BRM13 complemented with wild-type and mutated alcR⁺ plasmids constructed by overlap extension PCR. Each species' alcR genes were altered by a single nucleotide to the nucleotide sequence of the wild-type alcR gene of the other species. β-Galactosidase activities were measured for cells cultured in iron-replete SS medium (solid bars), iron-depleted SS medium (open bars), or iron-depleted SS medium supplemented with 20 μg of purified alcaligin/ml (hatched bars). β-Galactosidase activities are expressed in Miller units (mean ± 1 standard deviation; n = 3). (B) The relative degree of constitutivity of AlcR is depicted as in Fig. 2B. Multicopy alcR⁺ plasmids: Bp wt, pRK/N_pC_p; Bb wt, pRK/N_bC_b; Bp G103S, pRK/Bp-G103S; Bb S103G, pRK/Bb-S103G.