FIG. 5.

Hemin-responsive BhuR expression in B. bronchiseptica. The growth of iron-starved B. bronchiseptica wild-type (B013N) and isogenic bhuR mutant (BRM21) cultures with or without added hemin is described in Materials and Methods. Total-membrane fractions were prepared from cells harvested 8 h after the addition of hemin and analyzed by SDS-PAGE. −Fe, cells grown under iron-depleted conditions; −Fe +Hm, cells grown under iron-depleted conditions and supplemented with 5 μM hemin. Arrowheads, positions of the putative BhuR outer membrane receptor protein. Migration positions of the protein standards and their molecular masses in kilodaltons are designated.