Radioprotection in D. radiodurans, a radiation resistant bacterium

Deinococcus radiodurans is a bacterium that is extremely resistant to gamma radiation. Great interest in this organism led to its complete genomic sequencing in 1999. Some experiments have demonstrated that when the superoxide dismutase (SOD, a metalloenzyme that dismutates superoxide (O2-) to O2 and H2O2) is cloned out of the organism, the radiation resistance drops significantly. Understanding the mechanism of this bacterial superoxide dismutase (MnSOD) would help us to understand a large component of radioresistance exhibited by this organism and to address possibly engineering radioresistance into other organisms. Other facets of the extreme radiation resistance exhibited by D. radiodurans are thought to lie in particular membrane components and a unique resistance to dehydration.

The lifetime of superoxide (O2-) following its production by pulse radiolysis in the presence of superoxide dismutases from different sources and at varying superoxide dismutase concentrations: A: 1:1 MnSOD:O2- B 1:7 MnSOD:O2- C: 1:50
MnSOD:O2- ; a: human MnSOD; b: e coli MnSOD; c: Dr MnSOD

We are studying differences in D. radiodurans MnSOD and bacterial/human MnSOD using the fast kinetic technique of pulse radiolysis at BNL. We also use this facility to address reactivity of membrane components (e.g., aconitase, catalase). A longer-term goal is to look at membrane surface structure of D. radiodurans both before and after irradiation to help understand radiation resistance and dehydration. The use of bacteria for the remediation of heavy metal and radioactive waste (e.g. isotopes of uranium and plutonium, mercury) is very promising and has, in some cases, been translated into reality. The involvement of this particular bacterium lies in its extreme radiation resistance and efforts to engineer remediation function into D. radiodurans or to enhance the bacterium's existing ability to reduce heavy metals is underway elsewhere. The use of a bacterial system to accumulate and isolate the contaminants in the event of bombs or attacks on nuclear reactors/nuclear waste remediation facilities would represent an attractive cleanup method. Understanding the basic differences between D. radiodurans and other organisms in the above-mentioned systems (MnSODs, membrane components, membrane surface) may allow us to engineer radiation resistance into other bacterial systems that are already useful in non-radioactive cleanup.

This program is supported by a Laboratory-Directed Research and Development Grant (LDRD). We acknowledge Brookhaven National Laboratory for this support.

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Last Modified: June 28, 2012