USU student finds bacteria gene that repairs damage from sun
Finding from roof of BNR building sheds light on skin cancer
Wes Mortensen, a recent graduate of Utah State University, has made a discovery in his undergraduate research with bacteria that may some day help eradicate skin cancer.
After a year of research and a summer of experiments on the roof of USU's Biology and Natural Resources building, Mortensen concluded that RpoS, one of many genes found in two strains of bacteria located on the leaves and roots of plants, was responsible for the repair of damage done by the sun's ultraviolet light. Mortensen's study proved that without this gene, which is part of the genome within the bacteria, UV light can eventually destroy the organism.
Although bacteria and humans aren't exactly comparable when it comes to cell structure and genetic material, all are living organisms and have the potential to be hurt by the sun's rays.
"Bacteria get sunburned too," said Ann Anderson, a professor in the biology department, and one of Mortensen's project supervisors.
The results from Mortensen's study may bring scientists and researchers one step closer to understanding the way UV light affects cells in general. The idea for the project originally came from Anderson, who often helps students find research projects to spice up their resumes, and also to help "introduce [students] to a new thought process -- to see their brains function at a different level."
Mortensen, who was already filling out his applications to medical school, was in need of some type of research project to boost his chances of getting in. Anderson said the study on how UV light affects organisms had been a hot topic over the last few years and plans for the study were already underway. Mortensen, excited that he would be doing research that may some day benefit millions of people, joined the team.
"The project was a grant proposal for years," she said.
It was a matter of implementing it, and Mortensen was just the person to pick up that part of the project.
Mortensen said it was already known that some genes do the job of repairing DNA damaged by the sun's rays. DNA, short for the scientific term deoxyribonucleic acid, is the basic material every living organism is made of, and known as one of the building blocks of life.
Cancer may be the result of too much damage to a certain part of an organism's DNA. In the case of skin cancer, the gene that is responsible for repair has been exposed to so much UV light over time that the cell can't function anymore.
"Ten thousand people die every year from skin cancer," Mortensen said. "There are genes in the body responsible for repairing damage, that is their job. When the gene is overwhelmed, that is when cancer develops."
Since it is known that UV light is capable of damaging DNA, Mortensen's and Anderson"s plan was to try to pinpoint which genes in the bacteria are responsible for this repair.
Bacteria isolated from the roots and leaves, which contained RpoS were to be left in direct sunlight for between six and seven hours on the roof of the BNR building. Some had the RpoS, already thought to be responsible for repairing UV damage in the plants, removed. Then, all of the bacteria would be exposed to the same amount of sunlight, with some receiving more amounts of certain types of UV light than others. This would allow Mortensen to study the effects of different doses of UV on the bacteria, while determining whether RpoS was what he was looking for.
Mortensen also decided to see which was more affected by UV light, the bacteria from the roots or from the leaves. He hypothesized that the bacteria from the leaves, which are constantly exposed to sunlight, would withstand the UV better than the bacteria from the root.
Before he could start the experiment, Mortensen had to make media for the bacteria to thrive in. The recipe for this includes protein and sugar. The media Mortensen produced ended up as a yellow, somewhat thick mixture, which he referred to as "the chicken broth," because that is exactly what it looks like. It was then transferred to plates, or petri dishes.
Mortensen then needed to find a way to filter which type of UV the bacteria would receive. There are three types of UV light, A, B, and C. Type C is the shorter in wavelength and the most dangerous. The earth"s ozone layer completely blocks these rays from entering the atmosphere. Type B, which makes up 5 percent of the UV light that does enter the atmosphere, is the next smallest in wavelength, and thus it is assumed to be the most dangerous. Type A makes up the remaining 95 percent of penetrating UV. It has the longest wavelength, and is assumed by many to be the least harmful.
The filters Mortensen built were made to allow only a certain wavelength of UV light to pass through and reach the bacteria. The first was Triacetate, which allows both UV-A and UV-B to pass through. The second was Mylar, which allows UV-A to pass through, but blocks UV-B. The third was Llumar, which allows neither type of ray to permeate. The final filter was tin foil, which was the control, and obviously allows no light to pass through.
After doing the experiment a few times, Mortensen discovered that there was too much condensation on the filters, which might affect the results. To solve this problem, the plates were placed in a tub of water, which was kept somewhere between 22 and 27 degrees Celsius. A dome made of Triacetate, the filter that allowed both types of rays to pass through, was placed over the tub to keep condensation to a minimum.
Anderson said she was impressed with Mortensen's ability and ideas, and in unexpected situations like this, when it came to actually doing the project, he thought of a lot of it on his own.
"[Mortensen] built the chamber and worked out the mechanics," she said. "That was all his."
From July to August of 2000 between 9:30 a.m. and 4:30 p.m. on days when the sun was shining, Mortensen conducted his UV light experiment. Every hour he would remove a sample from each plate and analyze his findings. The time passed rather quickly, he said. There was plenty of entertainment from the BNR rooftop.
"I saw that big fire start up on the mountain behind the university," Mortensen said. "I thought it was just a bonfire, but before I knew it the whole thing was on fire. It was pretty cool to watch."
The fire also led to the biggest mishap of the project. After one day's experiment was over, Mortensen was on the roof gathering up the materials to bring inside. He was glancing up at the burning mountain while he dumped the water from the tub onto the gravel rooftop. He was a little too close to the edge, and most of the water gushed four stories down onto the heads of some curious people below, who had stopped to watch the blaze.
"I heard some screams, so I looked over the edge," he said. "Those people were not happy people after that."
The drenched passers-by made it a point to tell Mortensen's superiors about his "irresponsible behavior." They wanted to be sure no one got wet again. "It"s a good thing they did," Mortensen said with a sly smile, "since that is what I spent my spare time doing."
By August enough data had been collected to make a conclusion. The hypothesis was wrong. The bacteria from both the roots and leaves that had the RpoS removed eventually died or suffered irreparable damage when exposed to hours of sunlight.
As far as the effects the filters had on the bacteria, Mortensen discovered that UV-A, which passed through both the Triacetate and the Mylar, had the most detrimental affect. In simple terms, this means that 95 percent of the UV rays that pass through Earth's atmosphere are potentially dangerous and even lethal to organisms.
Anderson said that these results should be taken seriously in regards to skin cancer.
"In our research, we read that as little as 20 minutes in the sun in the hot part of the day can do damage to DNA," she said. "If it is not corrected, it can cause mutations that may lead to cancer."
Anderson said that although it is a "leap of faith" for people to accept the significance results that a student found while researching the DNA of the bacteria, the structure of these cells and human cells "have the same basic ingredients." So these findings are important.
In his written conclusion about the project Mortensen wrote, "If RpoS has such a profound effect" it is likely that humans have similar mechanisms.
Determining whether there are genetic traits associated with skin cancer in humans could help identify the genes involved. As the ozone depletes, we may some day need to genetically-modify our own protective genes to improve their effectiveness."
Just before Spring Break, Mortensen received an acceptance letter to medical school at the University of Utah. He is hoping to continue his studies, and possibly become a dermatologist. He said this research has been enlightening and has become a great source of pride.
On March 17, Mortensen attended NCUR 2001, the National Conference for Undergraduate Research, where he gave a poster presentation of his study. The conference was held in Lexington at the University of Kentucky, where students in many areas of research congregated to publicize their findings. Mortensen said he had a good time and was excited to share his findings with others.
"I"m really proud of it," he said. "It has been exciting and interesting to say the least."
The future physician smiled humbly as he also recalled having his results approved for publication in an upcoming issue of Current Microbiology. He was also quick to give credit to Anderson and others who helped make the project possible.
Anderson said she enjoyed working with such a "multitalented individual." She said she was amazed at the energy of Mortensen, who divided his time among his research, his wife, his church and even volunteer work.
"Sometimes we had to say,"Take off, go recharge your battery." she recalled. "He is a unique individual who can juggle more than an acrobat with his hands full and still come out with a smile."