Agrobacterium tumefaciens membrane-bound ferritin plays a role in protection against hydrogen peroxide toxicity and is negatively regulated by the iron response regulator.

An Agrobacterium tumefaciens membrane-bound ferritin (mbfA) mutant was generated to assess the physiological functions of mbfA in response to iron and hydrogen peroxide (H2O2) stresses. Wild-type and the mbfA mutant strains showed similar growth under high- and low-iron conditions. The mbfA mutant was more sensitive to H2O2 than wild-type strain. Expression of a functional mbfA gene could complement the H2O2-hypersensitive phenotype of the mbfA mutant and a rhizobial iron regulator (rirA) mutant, suggesting that MbfA protects cells from H2O2 toxicity by sequestering intracellular free iron, thus preventing the Fenton reaction. The expression of mbfA could be induced in response to iron and to H2O2 treatment. The iron response regulator (irr) also acted as a repressor of mbfA expression. An irr mutant had high constitutive expression of mbfA, which partly contributed to the H2O2-hyperresistant phenotype of the irr mutant. The data reported here demonstrate an important role of A.similar to tumefaciens MbfA in the cellular defence against iron and H2O2 stresses.