LSU researchers study organisms’ DNA repair
It may be many more lifetimes before humans discover a cure for cancer or learn whether there is life on Mars.
Whether those discoveries happen within the next several centuries or not, LSU researchers believe they have evidence that those discoveries are at least possible, locked away in a sixth-floor freezer of the university’s Life Sciences building.
It’s in that freezer that Brent Christner, an associate professor of biological sciences, and his colleagues store several hundred pounds of ice they had shipped from such far-off places as Siberia and Antarctica.
Some of the ice samples are rectangular chunks about the size of a computer screen. Other samples are baseball bat-size cylinders called ice cores. Some of them are 30,000 years old.
Within those ice samples, Christner and his team observed that even when frozen, certain single-celled organisms, like bacteria and viruses, have the capability to repair their own DNA, even after being blasted by doses of radiation that would mean certain death for a person.
Under the scientific belief that Mars was once like Earth, Christner said it’s not outlandish to assume that the same type of single-celled organisms that exist today in some of Earth’s most extreme weather conditions could also exist on Mars — now a frigid planet with a surface temperature of about minus-50 degrees Celsius that is constantly being bombarded by cosmic radiation because of its thin atmosphere.
“It follows that if we are going to look for evidence of life on Mars, we shouldn’t be looking for corpses,” Christner said. “We should be looking for living organisms probably frozen and living beneath the planet’s surface.”
He said conventional wisdom is that frozen organisms are essentially lifeless and subject to decay. His research, however, shows that there can be complex biological processes going on under those same conditions.
It’s during that decaying process that DNA strands — where the genetic “instructions” of all living creatures reside — break apart.
“Just think of an organism that is trapped in ice over extended periods of time and its DNA is being broken into pieces,” Christner said.
To simulate that in the lab, his team took the amount of radiation an organism could expect to be exposed to over 225,000 years and directed it at the bacteria they are studying over the course of an hour.
“We hurt the cells with radiation, damaged their DNA,” he said. “We didn’t want to kill anything, we just wanted to give them a black eye, we just wanted to injure them.”
Once the cells were damaged, they were placed inside a freezer. Over the course of two years, researchers observed that not only were the organisms repairing their own DNA strands, but they were making the repairs in a precise and orderly fashion, essentially guaranteeing the organism would become viable again.
Based on those observations, Christner said, the “habitability on Mars is looking better every day. I’m not saying these cells are immortal, but cells could exist in these environments for millions of years. There could be life on Mars.”
Christner also said it is foreseeable that research on the enzymes that promote DNA repair could have some value in treating diseases such as cancer.
“I’m not saying this is directly applicable to cancer treatment, but this could provide some biotechnical value,” he said. “We are learning how these enzymes work, learning how they are able to stitch DNA together.”
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Visit http://brent.xner.net/ for more information on Christner’s research.