Here is yet another good reason to brush your teeth regularly. Scientists at the SUNY Buffalo School of Dental Medicine have found that oral bacteria can exchange genes, which could make them more destructive and less susceptible to drug treatments. "These findings could be important in the transfer of antibiotic resistance between plaque organisms, as well as with more harmful bacteria," says researcher Howard Kuramitsu. In other words, oral bacteria that can now be eradicated with antibiotics may one day be immune to such treatments.

Kuramitsu and postdoctoral researcher Bingyan Wang investigated whether genetic exchange would be possible between oral spirochete and streptococcus bacteria using a plasmid, a genetic element that exists outside of chromosomes in some species of bacteria. The plasmid, which was resistant to antibiotics, served as a marker: the Streptococcus gordonii used in the experiment is by nature able to actively take up extracellular DNA and maintain some of its genetic information.

To conduct their experiment, the scientists created two scenarios: In one, they cultivated Streptococcus gordonii in the presence of the plasmid. In the other, they cultivated Streptococcus gordonii without the plasmid, but alongside another bacteria¿Treponema denticola¿that contained the plasmid. After cultivation, they found that the Streptococcus gordonii in both cases contained the plasmid.

"Our studies demonstrated genetic exchange between two markedly distinct oral bacteria," Kuramitsu says. "Therefore, exchange between two closely related bacteria, such as the one responsible for dental caries¿Streptococcus mutans¿and the harmless Streptococcus gordonii is highly probable.