“Conan the Bacterium’s” Secrets Illuminated
Insights into How Deinococcus radiodurans Resists Extreme Doses of Radiation
The bacterium Deinococcus radiodurans was discovered in 1957 in a can of meat that had been irradiated in order to sterilize it for longer shelf life. Typically, cultures of Deinococcus (sometimes called “Conan the Bacterium”) can withstand up to a million Rads (10,000 Grays) of ionizing radiation, roughly 2000 times the LD50 for humans. Exactly what mechanisms Deinococcus radiodurans uses to repair all the breaks in its DNA caused by radiation at this dose level remains poorly understood but recent work by Michael Daly, of the Uniformed Services University of the Health Sciences in Bethesda, MD, is providing some intriguing clues. In work supported by the Office of Biological and Environmental Research’s (BER) Natural and Accelerated Bioremediation Research and Microbial Genome Programs, and grounded in the availability of the complete genome sequence of this bacterium (determined by The Institute for Genomic Research with BER funding), Daly and collaborators find that Deiococcus radiodurans cells accumulate very high intracellular levels of manganese (Mn) but display extremely low levels of iron (Fe), suggesting a protective role for the Mn and a deleterious role for the Fe. This work is scheduled for publication on September 30 in ScienceExpress, a service of Science, with print publication to follow a few weeks after that. Furthermore, a similar profile of levels of these elements is found in other relatively radioresistant bacteria. This work suggests that radiation resistance could be altered by adjusting intracellular Mn and/or Fe levels. In human cancer therapies, treatments with agents reducing Mn or increasing Fe potentially could increase the radiosusceptibility of targeted cells thus improving prospects for survival.