I’m intrigued by extremophiles – bacteria that push the limits of the survivable – and a recent research article in PLOS Biology turned up something unexpected behind the mechanism of the radiation resistance (2000x the lethal dose for humans) of Deinococcus radiodurans. Initial work assumed that it had exceptional DNA repair mechanisms, which allowed it to repair the breaks in DNA produced by irradiation. The sequencing of the genome showed DNA repair was no more or less complex or sophisticated at the genomic level than those in other, more fragile, bacteria. The difference may well be in the bacterium’s ability to protect its proteins from radiation damage, so that the DNA-repair enzymes can do their job. D radiodurans has an extremely high manganese concentration, which detoxifies the reactive oxygen intermediates produced by ionizing radiation, combined with a low iron concentration. The combination protects against oxidative damage to proteins.

• Paradox Resolved? The Strange Case of the Radiation Resistant Bacteria, is a summary of the article’s background and findings in the April 2007 issue of PLOS Biology