Microbe Profiles: Deinococcus radiodurans
Read all about Conan the Radiation Loving Bacterium
Deinococcus radiodurans is one of my favorite species of bacteria (it even made the Guinness Book of World Records!). I came across it a few years ago when researching life that could survive on other planets, and it’s image soon became a favorite for wallpapers and profile pictures.
It’s a species that can seem pretty unassuming on first glance, but it’s strange habitat tells us there’s some spooky molecular action going on. Radiodurans thrives in radioactive waste.
The story of this extremophile’s discovery is an epic one. In 1956, researchers who had made the link between microbes and rotting food wanted to see if gamma radiation could sterilize canned meat and prevent it from rotting. When the meat still rotted after being bombarded with rays, they were able to pinpoint Radiodurans as the cause and the species claimed its title as one of the most radioresistant organisms on Earth.
As a polyextremophile, it can also brave desiccated, frozen environments and survive vacuum (maybe even the vacuum of space!).
How does it look?
The species has been described as a pinkish, reddish, spherical bacterium ranging from 1.5–3.5 microns in diameter. Perhaps the most notable thing about their structure is their tendency to stick together in groups of four — a tetrad, which has definitely been implicated in it’s radioresistance.
It stains gram positive, which means that it should have a thick layer of peptidoglycan in its cell membrane, but it’s actual cell structure is more similar to gram negative bacteria.
Where does it live?
While it was originally isolated in controlled lab conditions, it’s also been found in a few natural environments. Since bacteria and microbes in general are so small and widespread (they rule the Earth from their microscopic thrones), it’s hard to give an unabridged account of their whereabouts.
They seem to like temperatures between 30 and 37 degrees Celsius and its been found living in soil and granite in Antarctic dry valleys and in elephant feces. Maybe not a species you’d like to go searching for yourself!
How did it get it’s superpowers?
Radiation is the emission of energy in the form of high energy, subatomic particles or electromagnetic waves, which can penetrate and even shatter DNA and other microscopic structures found within cells. When D. radiodurans gets bombarded with ionizing radiation, the results are no different. Where it does differ, is having several copies of it’s chromosomal DNA and exquisitely efficient DNA repair mechanisms.
Recent works have shown that D. radiodurans doesn’t seem to have particularly unique DNA repair pathways that aren’t found in other organisms. It relies on ‘recombinational’ DNA repair mechanisms that are present in other species (including E. coli) that do not have the same magical abilities. Radiodurans seems to make small tweaks and novel augmentations to repair proteins that may be responsible for it’s DNA resistance.
It’s also thought that their cartenoid pigments (responsible for the species red color) act as free radical scavengers, adding some resistance from radiation. The species also has multiple copies of their DNA (packed into 4 major parts — chromosmes and plasmids) that are pretty hearty molecularity. The way the DNA loops around has even been compared to a lifesaver!
Despite all this, we still don’t seem to have evidence that accounts for all the marvelous superpowers D. radiodurans has.
What has astrobiology done with the species?
Remember we mentioned Antarctic dry valleys? Well, that habitat thought to most closely resemble Martian land. Of course, Mars has an atmosphere 1000x thinner than Earth’s and its around 95% carbon dioxide, but it’s still fun to think about!
The species has also been noted because of a crucial feature that seems to be shared with many polyextremophiles — genetic redundancy. Multiple copies of genetic information so if the first one blow, you’ll probably have a spare.
Our search for extraterrestrial life is ultimately limited to what we can find on Earth. We can only find conditions on other planets and see if there’s any current Earthling that can withstand those conditions.
Mars is a favorite when talking about this species and life in general. It’s got tons of water, but nothing that’s drinkable. It’s stored below the surface, or in polar ice caps. Rocks and other forms of potential shelter all emit some kind of radiation, so ‘hiding’ from the elements isn’t really possible.
The best case scenario for our Martian comrades is if they were able to assemble at a time when Mars was more hospitable and gradually evolve to develop badass properties, or more advanced methods of hibernation and protection.
How can it help us?
Bioremediation!
It lives where humans can’t so it could be used to help clean up nuclear disasters with the right engineering. With some freaky chemistry some microbes are naturally adorned with, D. radiodurans might be able to sequester radioactive metals, nasty, unstable contaminants that can cause fatal injuries in most other organisms.
Microbes are also used to biodegrade trash, so it could also be engineered to break down organic waste in highly dangerous environments. It’s a lot of hard work and it’s just the tip of what microbes do for us every day like ward off harmful invaders and synthesize vitamins.
Hopefully, this gives you all a better understanding of this amazing bacterium and, most importantly, the microbial diversity that is all around us — unseen and often ignored. Don’t forget to show the microbes your love.
Don’t take my word for it! View the full list of citations and additional resources here.
If you like the Microbe Profiles, you might enjoy this guide to the Suctorians.
Hi! I’m flagellate. When I’m not swimming in agar, or writing about my favorite microbes, you can find me making up stories about the end of the world, and helping science get funded.
