Unusual structure of the tonB-exb DNA region of Xanthomonas campestris pv. campestris: tonB, exbB, and exbD1 are essential for ferric iron uptake, but exbD2 is not.

Unusual structure of the tonB-exb DNA region of Xanthomonas campestris pv. campestris: tonB, exbB, and exbD1 are essential for ferric iron uptake, but exbD2 is not.