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Gene Sequence Something To Smile About

Scientists reveal genetic code for gum disease bacterium

THURSDAY, June 14, 2001 (HealthDayNews) -- Scientists have finished decoding the genetic sequence of a nasty bacterium that's linked to some of the most severe cases of gum disease, and as of this week, anyone on the Internet can take a look at their data.

The bacterium is called Porphyromonas gingivalis, and it's thought to play a major role in adult periodontitis – a chronic, progressive gum disease that can lead to tooth loss.

"This will be the first time that an oral pathogenic bacterium has ever been sequenced," says Dennis Mangan, the chief of the Infectious Diseases and Immunity Branch at the National Institute of Dental and Craniofacial Research (NIDCR), which supported the project.

"This will hopefully open up a whole new window of opportunities for us to learn more about the pathogenesis of disease, diagnosis, treatment and prevention."

According to Mangan, about 10 percent to 20 percent of Americans have a serious form of periodontal disease involving severe destruction of the tissue that supports the teeth. "This bug seems to be involved in quite a few or a high percentage of those [serious] cases of periodontal disease," he says. Current treatments involve tooth scaling, root planing and surgery.

The project, which was carried out by the Institute for Genomic Research (TIGR) in Rockville, Md., and the Forsyth Institute in Boston, started more than five years ago. At the time, the Institute was supporting research to sequence a few of the genes involved in the bacterium, but Mangan soon learned that new technology would make it possible to sequence the entire genome at a fraction of the cost. The final tab for the project came to between $1.1 million and 1.5 million.

The result: a sequence containing 2.2 million DNA base pairs. Researchers are now taking the completed sequence and "annotating" specific genes – giving them names and determining what they do.

Using special software, says Mangan, a researcher anywhere in the world can look for genes that may or may not be present in the bacterium. "We might be able to find out what … makes them so nasty and causes so much destruction of the oral tissue."

Potentially, he says, if researchers learn which genes are responsible for causing disease, targeted therapies could be developed. "You might just need to knock out or neutralize genes X, Y and Z then," says Mangan. "You might not need to kill the entire bacterium, which would get you away from antibiotic resistance."

Mangan points out that because this bacteria is anaerobic, meaning it can't be exposed to oxygen for long, researchers require special facilities to grow this bug in the lab. "Now, people that don't even have the ability to grow bacteria at all can take at look at this genome and learn a lot about what it can and can't do,"

Dr. Ann Griffin, an associate professor of pediatric dentistry at Ohio State University in Columbus, Ohio, says that while the developments won't happen overnight, "it's going to make work on P. gingivalis a lot easier."

Griffen says that researchers still aren't sure how large a role P. gingivalis plays in gum disease, because other bacterial species that exist in the mouth have not yet been cultured or studied. "Figuring out P. gingivalis isn't going to be the whole story," she says.

But if none of those bacteria cause disease, says Griffen, then P. gingivalis plays a very important role, because only two other organisms have been linked consistently to gum disease.

Griffen says that she's looking forward to the sequences of different strains of the P. gingivalis bacterium, which could be used to determine what parts of the genome actually cause disease

"It could definitely suggest genes for drug targets," she says.

Mangan says there's much more work to come, both on P. gingivalis and other bacteria. "This is just the starting point for so much more research to be done, and at a much more accelerated pace that what we've been doing over the past 10, 15, 20 years."

What To Do

Take a look at the genome for yourself at The Institute for Genomic Research Web site or check out the Porphyromonas gingivalis Genome Project site.

Recent research has suggested that bacteria in your swap genes to create even nastier germs.

You can also learn more about dental health by checking out these previous HealthDay stories.

SOURCES: Interviews with Dennis F. Mangan, Ph.D., chief, Infectious Diseases and Immunity Branch Division of Extramural Research, National Institute of Dental and Craniofacial Research, Bethesda, Md.; and Ann L. Griffen, D.D.S., associate professor, Department of Pediatric Dentistry, Ohio State University, Columbus, Ohio; TIGR Web site
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