Scientists decipher tooth decay bug’s genome

Researchers in Oklahoma have deciphered the complete genome sequence of Streptococcus mutans, the main organism implicated in causing tooth decay. The work, supported by the National Institute of Dental and Craniofacial Research, has been made freely available online. Said one of the team members involved in the four-year effort: “Building on this basic research may one day lead us to new approaches for preventing and treating tooth decay.” Added another: “By targeting the adherence genes, for example, we might be able to develop a way of preventing S. mutans from sticking to teeth.” From the National Institute of Dental and Craniofacial Research :Scientists Decipher Genome Sequence of S. Mutans

Scientists have deciphered the complete genome sequence of Streptococcus mutans, the main organism implicated in causing tooth decay. The scientists have made each piece of sequencing data freely available online during the course of the four-year project. Supported by the National Institute of Dental and Craniofacial Research (NIDCR), the sequencing project was carried out by researchers at the University of Oklahoma. The paper describing their work will be published online this week at the Proceedings of the National Academy of Sciences Web site (www.pnas.org).

“This is an extremely powerful tool for the scientific community,” said NIDCR’s Director Dr. Lawrence Tabak. “It will allow researchers to systematically and comprehensively study the pathogen most implicated in tooth decay. It will enable us to identify genes involved in acid tolerance, biofilm formation and communication as well as other genes important in the functioning of S. mutans. Building on this basic research may one day lead us to new approaches for preventing and treating tooth decay.” Although the incidence of tooth decay has declined over the past generation, it is still the single most common chronic childhood disease — 5 times more common than asthma. More than 50 percent of 5- to 9-year-old children have at least one cavity or filling, and that proportion increases to 78 percent among 17-year-olds.

S. mutans is one of the myriad organisms found in the human mouth. It has the ability to stick to teeth and to produce acids when exposed to sugars and carbohydrates. Tooth decay occurs when a susceptible tooth is exposed to these acids, which — over prolonged periods of time — dissolve and weaken tooth enamel.

“Until now, we’ve had only pieces of the puzzle,” said Dr. Joseph Ferretti, the study’s senior author, from the Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center. “It’s very satisfying to have the complete sequence. With the data available online, researchers around the world can access it from their offices. They’ll be able to discover in weeks information that once took years to obtain,” Dr. Ferretti said.

With the S. mutans sequence now available, the scientists say it will be possible to identify genes that might be potential targets for new therapies. There are more than 1,900 recognized genes on the one circular chromosome of S. mutans. Of those recognized genes, scientists have already attributed likely biological functions to 63 percent of them. These genes are involved in a range of tasks, including cell division, cell wall synthesis, metabolism, transport, virulence, adherence, signaling, and other functions. “By targeting the adherence genes, for example, we might be able to develop a way of preventing S. mutans from sticking to teeth,” said first author Dr. Dragana Ajdic, also with the Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center.

The sequence, which contains two million base pairs, will also be useful to scientists studying other microbes, the scientists say. “If we identify a certain function in S. mutans, we can look to see if related bacteria have similar properties,” said Dr. Ajdic. “This can go a long way in adding to our knowledge of bacteria.”

Within the past few years, NIDCR has funded 13 genome sequencing projects for oral microbes, including those associated with dental decay, periodontal (gum) disease, and oral candidiasis, a fungal infection.

The sequence data for S. mutans is available at: http://www.genome.ou.edu/smutans.html, http://www.oralgen.lanl.gov/, and through GenBank (accession number AE014133).

Working on the S. mutans project with Drs. Ferretti and Ajdic, were Dr. William McShan, Dr. Robert McLaughlin, Gorana Savic, Jin Chang, Matthew Carson, and Charles Primeaux from the Department of Microbiology and Immunology, University of Health Sciences Center, Oklahoma City, and Runying Tian, Steve Kenton, Honggui Jia, Shaoping Lin, Yudong Qian, Shuling Li, Dr. Hua Shu, Dr. Fares Najar, Hongshing Lai, Jim White, and Dr. Bruce Roe from the Department of Chemistry and Biochemistry, University of Oklahoma in Norman, Oklahoma.

The NIDCR is part of the National Institutes of Health in Bethesda, Md. The Institute is the nation’s leading supporter of research on oral, dental, and craniofacial health. NIH is an agency of the U.S. Department of Health and Human Services.

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