Deinococcus Radiodurans: A Comparative Genomic Analysis

Deinococcus radiodurans is an interesting obligate aerobic and polyextremophilic bacterium, harboring characteristics that allow for growth and survival under some of the world’s harshest conditions. In 1956, Arthur W. Anderson et al. discovered the bacterium while conducting food sterilization experiments at the Oregon Agricultural Experimental Station in Corvalis. After using substantial doses of gamma radiation on canned meat, the researchers found that the meat still spoiled, and D. radiodurans was subsequently isolated. In 1999, strain ATCC BAA-816’s DNA was sequenced by the Institute for Genomic Research, with further comparative genomic analysis published by the American Society for Microbiology (White, 1999). Fifty-nine years later,

radiodurans is no exception. The bacterium can survive acute doses of ionizing radiation at levels exceeding 10,000 Gy, and is proficient at growing under chronic levels of 60 Gy/hour. For comparison, the average human cannot survive 5 Gy of radiation, and Escherichia coli is sterilized by 2,000 Gy (Daly, 2011). Secondary to radiation-resistance is D. radiodurans’ ability to repel DNA damage in the presence of hydrogen peroxide, dessication, and ultraviolet light. Conclusive reasoning for such efficient and extraordinary survival does not currently exist, but most research points to the bacterium containing “…all systems for DNA repair, DNA damage export, desiccation and starvation recovery, and genetic redundancy present in one cell” (White, 1999). Instead of a single genomic copy, D. radiodurans cells contain between three and ten copies of its genome, often physically layered on top of each other. This unusual layout of genetic material may account for its amazing DNA repair mechanisms, allowing the microbe to mend its genome with no mutagenesis after 2,000 double-stranded DNA breaks; an amount 130 times greater than what E. coli can handle. Regarding the conversion and production of energy, D. radiodurans has a curious feature that aligns it more with archaea and eukaryotes: a vacuolar ATP synthase protein instead of the F1F0 variant found in most other free-living bacteria. Due to partial conservation of the vacuolar ATP operon compared to archaea, scientists believe the genes were disseminated through horizontal transfer (Makarova,