Animal Angles: Berry Interesting!
by Ruth Tenzer Feldman
I'd like you to meet Deinococcus radiodurans. The name means “strange berry that withstands radiation.” This pinkish-red bacterium is strange indeed.
D. radiodurans might have come from “stardust” that landed on early Earth and Mars, but the bacterium wasn't discovered until 1956. It was found in a can of meat that spoiled, even though the meat had been zapped with a huge dose of radiation. Since then, D. radiodurans has shown up in widely varying environments, from the Marslike granite beds of Antarctica to hot springs and llama feces.
Radiation energizes atoms enough to break their chemical bonds and shatter an organism's genetic material. While you and I would die after exposure to 50 to 100 rads of radiation, this bacterium can survive 1.5 million to 3.0 million rads!
Here's how. D. radiodurans has four to ten copies of its genome, so it has lots of extra material available to repair itself after radiation damage. The bacterium uses proteins to recombine breaks in its strands of genetic information. These proteins search through the genome copies to find and use the correct intact portion to mend the damaged strand.
Other bacteria have extra genetic material and can repair damaged DNA. But D. radiodurans survives better than they do because it repairs itself completely within 12 to 24 hours. That's amazing!
Scientists think that D. radiodurans could survive radiation-filled space and harsh conditions on Mars. The bacterium could be genetically altered to make medicines humans might need on Mars and to help terraform (make Earthlike) the Martian environment.
Meanwhile, D. radiodurans is very useful on Earth. We know the complete sequence of its genome and are designing variants of D. radiodurans that thrive in toxic waste sites. Genetic cousins are already turning mercury and toluene (a toxic solvent) into less dangerous substances. In a sense, this “strange berry” is terraforming Earth. I'm glad to make its acquaintance!
- DNA: Deoxyribonucleic acid, the type of nucleic acid that carries genetic information in most living things. Made up of two strands that are twisted into a double helix shape, it is found in chromosomes.
- genome: A complete set of chromosomes (stringlike bodies that contain genes in the nucleus of a cell).
- rad: A unit of energy absorbed from ionizing radiation.
- What have scientists discovered about the Deinococcus radiodurans bacterium?
[anno: Scientists have discovered that the Deinococcus radiodurans bacterium can withstand up to 1.5 to 3.0 million rads.]
- What applications are scientists exploring for the Deinococcus radiodurans bacterium here on Earth?
[anno: Scientists have been studying how to make waste sites less toxic by using the bacterium to transform mercury and toluene.]
- The article mentions terraforming Mars. If scientists are looking at ways to use Deinococcus radiodurans on the surface of Mars, what kinds of conditions probably exist on the surface of Mars that make the planet dangerous to humans?
[anno: If scientists are looking at ways to alter the conditions on Mars by using this bacterium, it means that the surface of Mars has too much radiation for people to survive there right now.]
- What might be another use for this bacterium here on Earth? Think about what the bacterium does. How might people benefit from the use of the bacterium or the bacterium's abilities? Consider how the bacterium might be used in a hospital situation, an emergency situation, or an everyday situation. Write a sentence or two explaining how people might benefit from the use of this bacterium and why the bacterium would be useful in this application.
[anno: Answers will vary. Students may suggest using the bacteria in sunscreen to improve the ability of a lotion to block harmful UV rays. Students may suggest that the bacterium could be used to help toxic spills in the ocean. Students may also suggest that the bacterium be used in medical procedures, such as helping to contain radiation therapy for cancer patients.]