Novel Insights into Bacterial Radiation Resistance Developed from DOE Microbial Genome Program


In a paper that has been accepted for publication in next month’s FEMS Microbiology Reviews, Michael Daly of the Uniformed Services University of the Health Sciences and colleagues (including scientists from Howard University, NIH, Pacific Northwest National Lab, and the University of Minnesota) develop the concept that radiation resistant microbes such as Deinococcus radiodurans (capable of resisting doses up to 2000 times what is lethal for humans) is not due to unusual or extra genes that less resistant bacteria lack, but rather that due to regulatory alterations that permit them to use their repair mechanisms much more efficiently. A characteristic observed in radiation resistant bacteria is the accumulation of high levels of intracellular Manganese (Mn) ions and the relative dearth of Iron (Fe); just the opposite is seen in bacteria that are sensitive to radiation. Mn is known to suppress the formation of oxygen radicals while Fe tends to promote their formation, suggesting a link between radical formation (consequent to normal cell metabolism) and DNA damage. This may lead to the identification of ways to increase radiation resistance by adjusting Mn/Fe ratios in cells prior to radiation exposures.