Could you withstand a nuclear fall out?

2 Mar

by Amberley Stephens

Humans couldn’t, a cockroach couldn’t, however Deinococcus radiodurans can.  It has been named one of the world’s toughest bacteria. Humans are killed by around 400-1000 rads of ionising radiation, a cockroach would be killed after 4000-10000 rads (radiation absorbed dose)  and would not survive nuclear fall out, contrary to popular belief. D.radiodurans can happily live and replicate through 1.5million rads of ionising radiation and survive up to 3million rads.

How can it survive such high levels of radiation? It has superior DNA repair systems. DNA becomes damaged during exposure to radiation if cell DNA repair systems can not repair the damage it leads to cell death and or cancer, depending on length and strength of exposure. D.radiodurans has special mechanisms to protect it against death. Unlike our DNA, that is wound around histone proteins and packed as nucleosomes for protection, D. radiodurans has DNA wound in a tighter structure called a toroid. This means when its DNA breaks it is held together, unlike ours which is more likely to drift away making it harder to repair. It also has four to ten copies of its DNA kept in different parts of the cell. When enzymes repair the DNA they compare it to another strand to avoid mistakes and mutations.

Not only can D.radiodurans survive nuclear fall out, but it is resilient against heat, cold, acid and it can survive in outer space. It may be expected that this remarkable bacterium is only found in the deepest seas or surrounding the hottest volcanoes, however it can actually be found in your back garden. It may seem strange that bacteria so resilient survives in soil, however its ability to survive radiation is only a side effect of adapting to severe desiccation; lack of water causes similar stresses on DNA as radiation.

D.radiodurans has been modified by scientists to decontaminate toxic nuclear sites. The mercuric reductase gene detoxifies ionic mercury found in nuclear waste. Not only is this a fascinating bacteria species but it also cleans up the mess we make!


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