subtilis strain is used as the recipient cell. We thank T. Hoshino, Y. Sadaie, and the late K. Kakinuma for bacterial strains, and M. Okamura, K. Ohta, and K. Niwa for technical assistance. “
“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 selleck inhibitor 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. tumefaciens MbfA in the cellular defence against Olaparib in vitro iron and H2O2 stresses. Agrobacterium tumefaciens is a phytopathogenic bacterium. Iron restriction and oxidative burst are vital environmental stresses for phytopathogens during the infection of hosts. Plants have the ability to capture iron (Mila et al., 1996) and increase the production of reactive oxygen species as a host defence response (Wojtaszek, 1997). Iron and oxidative stress are closely linked. Excessive amounts of intracellular free iron are toxic to cells owing

to its participation in the production of reactive hydroxyl radicals via the Fenton reaction (Fe2+ + H2O2 Fe3+ + OH− + OH˙) (Imlay et al., 1988). Therefore, iron regulation and oxidative stress resistance are key abilities of pathogenic bacteria that determine a successful infection during interaction with the host. Bacteria can prevent iron toxicity by depositing excess iron in iron-storage proteins (Andrews et al., 2003). Iron-storage Lck proteins are generally known as ferritins. At least twelve protein families have been classified as members of the Ferritin-like superfamily (Andrews, 2010). These twelve families share a characteristic four-helical bundle that contains conserved amino acid residues for iron binding. Among the twelve families, the Ferritin family is the best characterized. The Ferritin family consists of three subgroups: the ferritins (Ftn), the bacterioferritins (Bfr) and the DNA-binding protein from starved cells (Dps proteins).