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

Abstract

An Agrobacterium tumefaciens membrane-bound ferritin (mbfA) mutant was generated to assess the physiological functions of mbfA in response to iron and hydrogen peroxide (H 2O 2) stresses. Wild-type and the mbfA mutant strains showed similar growth under high- and low-iron conditions. The mbfA mutant was more sensitive to H 2O 2 than wild-type strain. Expression of a functional mbfA gene could complement the H 2O 2-hypersensitive phenotype of the mbfA mutant and a rhizobial iron regulator (rirA) mutant, suggesting that MbfA protects cells from H 2O 2 toxicity by sequestering intracellular free iron, thus preventing the Fenton reaction. The expression of mbfA could be induced in response to iron and to H 2O 2 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 H 2O 2-hyperresistant phenotype of the irr mutant. The data reported here demonstrate an important role of A. tumefaciens MbfA in the cellular defence against iron and H 2O 2 stresses. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.