21 March 2007
Manganese Key To Radiation-Proofing Of Organisms
by Kate Melville
Exploring methods to protect living organisms from chronic or acute doses of radiation, military researchers say they have uncovered how an unusual bacterium manages to deal with radiation exposure that would kill any other living creature.
Describing their work in PLoS Biology, the researchers from the Uniformed Services University of the Health Sciences (USU) say their discovery could lead to new avenues of exploration for radioprotection in diverse settings.
In the past, efforts to protect against ionizing radiation have focused on DNA damage and repair, but the bacterium in question - Deinococcus radiodurans - has nothing obviously unusual in its DNA repair components and employs quite a different method, relying instead on protein oxidation.
Investigating the mechanism behind this, USU's Michael J. Daly found that resistant bacterial cells had significantly different metal concentrations, pointing to high levels of manganese and low iron levels as possible influences on cellular recovery following irradiation. Daly's team showed that the most resistant bacterial species contained approximately 300 times more manganese and three times less iron than the most sensitive species.
In the new study, which examined the consequences of this disparity, the researchers demonstrated that high cytosolic manganese and low iron concentrations enable resistance by protecting proteins, but not DNA, from ionizing radiation-induced oxidative damage.
The findings point to new avenues of exploration for protection from radiation, which could eventually influence how individuals are treated for exposure to chronic or acute doses of radiation. In the civilian sector, this may mean better outcomes from radiation therapy and new ways to contain toxic runoff from radioactive Cold War waste sites.
Source: Henry M. Jackson Foundation for the Advancement of Military Medicine