Researchers at Forsyth Dental Center are tracing the identity of unknown and emerging microbes, some of which have foiled the efforts of investigators around the country. Using the newest molecular methods, Floyd Dewhirst and Bruce Paster, associate professors in the Harvard School of Dental Medicine's Department of Oral Biology, are identifying mysterious bacterial species that may be the cause of dental root caries and periodontitis. But the search is not limited to the oral cavity. Dewhirst and Paster have received funding from the Centers for Disease Control in Atlanta to ID 1,000 bacterial cultures on the CDC's most wanted list.
When clinical microbiology laboratories come across an unknown bacterium, they often send it to a state microbiology laboratory for identification. If the state laboratory cannot identify it, the sample is sent to the CDC. If the CDC is stumped, the sample will be sent to Forsyth. "If there's some unknown organism--we are the ones who are going to identify it," says Paster.
The traditional phenotypic methods of bacterial identification rely on how a bacterium behaves, its shape, and what food sources it uses for growth. The molecular approach, which zeroes in on genetic material, can be quicker and more specific. And identified DNA sequences provide phylogenetic information about how each bacterium is related to other members of its species.
Dewhirst and Paster are masters of microbial phylogeny and characterization. They have identified bacteria from such varied sites as mouse intestines, 57-year-old Dead Sea water, bird feces, and termite guts. The "flashlight" they use to illuminate the shadowy phylogenetic relationships between microorganisms is the sequence of the 16S ribosomal RNA gene.
"This gene has conserved regions and very variable regions," says
Dewhirst. The conserved, unchanging sections allow the researchers to zoom in on
the informative gene. From there, they can
Contact: Peta Gillyatt
Harvard Medical School