Conan the Bacterium Radiation Resistance and Deinococcus radiodurans Jacqueline Parker
Outline What is Deinococcus radiodurans? History and Phylogeny Repair Mechanisms of Deinococcus Current Interest in Deinococcus Conclusion and References
What is Deinococcus radiodurans? “Little berry that withstands radiation” Resistant to dehydration and genotoxic chemicals, Deinococcus has the ability to withstand remarkably large amounts of ionizing radiation. Deinococcus thrives at levels of 1.5 million rads and can withstand levels of up to 3.0 million
History and Phylogeny First appeared in the 1950s in canned meat that had been experimentally irradiated as means of preservative Represented on many phylogenetic trees to be close in evolutionary distance to another widely known extremophile Thermus aquaticus Phylogenetic Tree
Repair Mechanisms of Deinococcus Radiation results in double stranded breaks in the DNA
Repair Mechanisms of Deinococcus Deinococcus is able to withstand and repair radiation damage sometimes resulting in 200 or more double-stranded breaks in the DNA at one time 2 Main Steps: 1: single-strand annealing 2: RecA and homologous recombination
Theories Deinococcus has 4-10 DNA molecules per cell. When grown under conditions which cause a reduction in genome copy number, Deinococcus becomes less resistant to radiation. “Life-Saver Hypothesis” Circular DNA is easily stacked with identical DNA sequences near each other.
Current Interest in Deinococcus Bioremediation: Deinococcus as a vehicle for metabolizing residual chemical wastes Deinococcus radiodurans equipped with genes enabling the organism to metabolize metals such as Uranium would be a lucrative and safer way to eliminate waste Ability to withstand drought and high doses of radiation may have been indicative of other origins
Conclusion Deinococcus has the ability to withstand remarkably large amounts of ionizing radiation using repair mechanisms that include single-strand annealing and the protein RecA and homologous recombination Different theories are being investigated as to how these repair mechanisms are utilized to promote efficiency in the organism Deinococcus is currently being researched as a viable tool for industrial clean up uses that may include doses of radiation that would otherwise be lethal to other organisms
References Brown, James et al. “Universal trees based on large combined protein sequence data sets” Nature 28 (2001) 281-285. Gupta, Radhey S. “Protein Phylogenies and Signature Sequences: A Reappraisal of Evolutionary Relationships among Archaebacteria, Eubacteria, and Eukaryotes” Microbiology and Molecular Biology Reviews 62 (1998): 1435-1491. Makarova, Kira S. et al. “Genome of the Extremely Radiation-Resistant Bacterium Deinococcus radiodurans Viewed from the Perspective of Comparative Genomics” Microbiology and Molecular Biology Reviews 65 (2001): 44- 79. Rothschild, Lynn H. Insight Nature 409 (2001) 1092-1101. Venkateswaran, Amudhan et.al. “Physiologic Determinants of Radiation Resistance in Deinococcus radiodurans” Applied and Environmental Microbiology 66 (2000) 2620-2626.