Friday Fellow: Conan the Bacterium

ResearchBlogging.orgby Piter Kehoma Boll

Most people would agree that 2016 was a hard year. So let’s try to make 2017 better by starting this year with a tough Friday Fellow, actually the toughest of them all: Conan the bacterium, or Deinococcus radiodurans.

A relative of Taq, Conan the bacterium is a rather large bacterium, measuring 1.5 to 3.5 µm in diameter and usually forming groups of four organisms sticking together, a formation known as tetrad. It is an extremophilic bacterium, able to resist to very harsh environments. Actually, Conan the bacterium is one of the most radiation-resistant organisms known to date and can also resist extremes of cold, dehydration, vacuum, and acid. Its popular name was based on the character Conan the Barbarian.

deinococcus_radiodurans

A tetrad of Deinococcus radiodurans.

Conan the bacterium was discovered in 1956 during an experiment that tried to sterilize canned food using high doses of radiation. One bacterium survived the high doses of gamma radiation and was identified as a new species.

Later, a group of scientists suggested that the high degree of radioresistence was an adaptation to the Martian environment, so this could be an alien bacterium! But that’s actually bullshit. Conan the bacterium has nothing significantly different from other lifeforms on Earth, but how did such a resistance to radiation evolve? Background radiation on Earth is very weak, so it could not appear by natural selection.

The results of some experiments published in 1996 revealed that strains of D. radiodurans that are susceptible to desiccation are also susceptible to radiation. Thus, the most likely explanation is that the high resistance to radiation is simply a side-effect to the resistance to desiccation, a condition much more common in the bacterium’s environment.

The mechanism that allows Conan the bacterium to withstand radiation is very complex, but includes an ability to rebuild DNA strains from fragments, which is helped by the fact that each cells contains four copies of the bacterial chromosome, so that a partially-damaged strain can serve as a model to repair another partially-damaged strain.

Our tiny fellows are always full of amazing surprises!

– – –

References:

Mattimore, V., & Battista, J. (1996). Radioresistance of Deinococcus radiodurans: functions necessary to survive ionizing radiation are also necessary to survive prolonged desiccation. Journal of Bacteriology, 178 (3), 633-637 DOI: 10.1128/jb.178.3.633-637.1996

Wikipedia. Deinococcus radiodurans. Available at <https://en.wikipedia.org/wiki/Deinococcus_radiodurans&gt;. Access on January 2, 2017.

Zahradka, K., Slade, D., Bailone, A., Sommer, S., Averbeck, D., Petranovic, M., Lindner, A., & Radman, M. (2006). Reassembly of shattered chromosomes in Deinococcus radiodurans Nature DOI: 10.1038/nature05160

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