Have you ever wondered what would survive a nuclear disaster? What comes to mind? Cockroaches? Cher? What about bacteria?! The Guinness Book of World Records
called Deinococcus radiodurans
the “world’s toughest bacterium”. That’s no surprise when your nickname is “Conan the Bacterium
was discovered by Arthur W. Anderson in 1956. Anderson was working in Corvallis, Oregon at the Oregon Agricultural Experiment station. The researchers were attempting to sterilize canned foods with gamma radiation. When a can of meat spoiled, they discovered Deinococcus radiodurans
are spherical bacteria, but they actually live in groups of four cells - a tetrad. Deinococcus
has a thick cell wall which makes it appear Gram-positive when stained. However, it has two membranes, so more closely resembles a Gram-negative cell.
Just how tough is Deinococcus
? A chest X-ray produces about 1 mGy
of radiation, 5 Gy kills a human, and 200-800 Gy kills E. coli
can survive 5,000 Gy. When exposed to 15,000 Gy, it’s viability decreased to 37%. Not too shabby.
What makes Deinococcus
radioresistant? According to Claire M. Fraser of The Institute for Genome Research (the group that sequenced the Deinococcus
genome), “the organism can put its genome back together with absolute fidelity”. Radiation damages cells because it breaks apart DNA. Deinococcus
actually has fewer DNA repair proteins than most bacteria, but it is particularly good at making those repairs. It also totes around 4-10 copies of its genome, where most bacteria just have 1. It probably uses these backups to help repair damage. There is some data to suggest that Deinococcus
also uses manganese
to combat oxidative damage and nitric oxide
to jump start growth after DNA repair.
Of course, all of these superpowers are being harnessed by us humans in one way or another. Many researchers want to use Deinococcus
for bioremediation at highly radioactive sites. Not only can it be engineered to break down contaminants like toluene
, but it is virtually the only bacterium that can survive the harsh conditions. Since it’s a glutton for punishment, Deinococcus
could also be used to break down sewage on long-distance space flights. Last, and my personal favorite, a group at Imperial College London translated the song
“It’s a Small World” into DNA bases and stored it in the Deinococcus
genome (at least we’ll be able to sing Disney songs after the world ends).
So, the next time someone asks you what will survive a nuclear disaster, you can tell them cockroaches, Cher, AND Deinococcus
Sources: University of Florida, MicrobeWiki, PNAS
, New Scientist
, Genome News Network, NASA, Science Daily, Wikipedia