It has been reported that D. radiodurans can recover from exposure to γ-radiation at 15 kGy, a dose lethal to most life forms. IR can directly damage biomacromolecules and can also produce reactive oxygen species (ROS) that can indirectly attack both proteins and DNA [3, 4]. Therefore, cellular defense against ROS-induced protein and DNA damage is proposed to be important to the radiation resistance of D. radiodurans
. Manganese plays an important role in the antioxidant systems of bacteria and can relieve the phenotypic deficit of sod-null Escherichia coli . Interestingly, Daly and coworkers found that the Mn/Fe ratio of most IR-resistant bacteria is higher than that of IR-sensitive bacteria. The group see more also found that D. radiodurans grown in manganese-deficient 17-AAG nmr medium was relatively more sensitive to IR than the bacteria grown in manganese-containing medium, suggesting that the accumulation of intracellular manganese ions can protect proteins from ROS-induced damage and can help in the survival of D. radiodurans in extreme environments [5, 7, 8]. Although manganese can improve cellular ROS resistance, excess
manganese is toxic to cells. Thus, maintenance of the intracellular Mn concentration homoeostasis is a challenge. In bacteria, two main classes of manganese transporters have been identified–Nramp H+-Mn2+ transporters and the ATP-binding
cassette (ABC) Mn2+ permeases . Recently, a manganese efflux system was identified in Streptococcus pneumoniae, and this was found to play important roles in host pathogenesis and H2O2 resistance . Many genes involved in the maintenance of manganese ion homeostasis have been reported in D. radiodurans, such as dr1709, dr2523 , dr2539 , and dr0615 . Therefore, it would Ergoloid be very interesting to determine whether D. radiodurans possesses a similar manganese efflux system. In this study, we identified a manganese efflux gene (dr1236) in D. radiodurans and demonstrated that it plays an important role in maintaining the homeostasis of intracellular Mn. The null mutant mntE – was Epoxomicin cell line highly sensitive to manganese ions. When the intracellular level of manganese ions was increased by mutating dr1236, the mutant showed clearly enhanced resistance to oxidative stress. Our results also demonstrated that increased intracellular Mn levels could substantially suppress protein oxidation (carbonylation) in D. radiodurans exposed to H2O2, indicating that manganese transport and regulation may be involved in the cellular resistance of D. radiodurans to oxidative stress. Results and discussion D. radiodurans encodes a putative manganese efflux protein By searching the D. radiodurans genome http://www.ncbi.nlm.nih.