Bacteria battle against toxic fluoride

December 22, 2011

Regular use of fluoride-containing toothpaste and mouthwash has long been known to strengthen the enamel on teeth. But new research by Howard Hughes Medical Institute (HHMI) scientists finds that fluoride also has dramatic effects on bacteria inside the mouth -- including those that form plaque and can cause cavities.

HHMI researcher Ronald Breaker of Yale University has discovered the cellular chain of events that occurs inside a bacterium after it encounters fluoride in its environment. His team's findings reveal that many bacteria try to fend off fluoride - which the organisms treat as a toxic substance - by throwing it out. The presence of such a transport system indicates that fluoride itself has antimicrobial properties, Breaker said. The findings are published online in Science Express on December 22, 2011.

Breaker's lab studies non-coding RNA, stretches of genetic material that play regulatory roles in the cell instead of coding for proteins. Using different computer algorithms, he and his colleagues analyze the genomes of organisms to identify signature sequences in genetic material that likely indicate the presence of noncoding RNA. Among the types of non-coding RNAs they find are regulatory molecules called riboswitches. Normally, the role of a riboswitch is easy to deduce: Riboswitches are attached to the genes that they regulate. If the gene is needed to produce a certain compound, the riboswitch is usually sensitive to that compound, so when its level increases or decreases in the cell, the riboswitch can cause more or less to be made. Aside from their interest in the biology of riboswitches, Breaker's group is studying these genetic switches because they could represent new drug targets and might be used to control the activity of genes inserted into cells as gene therapies.

In a recent set of experiments, Breaker's team identified a new riboswitch that was attached to a handful of genes with vague or unknown functions. They were stumped. "We knew we had a riboswitch but we didn't know what it bound," says Breaker. "And we were very intrigued because it was one of the only non-coding RNAs we've ever found that's present in both bacteria and archaea. That suggests that it has ancient origins and an important role in the cell," he notes.

So Breaker and his colleagues put the RNA in a test tube and began to mix in different chemicals, observing whether or not they bound to the riboswitch. They worked through a long list of more common chemicals before they stumbled on fluoride. The addition of fluoride was an accident -- fluoride was a contaminant in a sample of a different chemical they were testing.

Once Breaker's group found that the riboswitch bound to fluoride, they were able to show that the genes controlled by the riboswitch are those that help the cell fight the toxicity of fluoride. Fluoride, a negatively charged ion, binds aggressively to some metabolites and essential enzymes. If fluoride floods a cell, it can quickly shut down cellular processes. The fluoride-sensing riboswitch, Breaker's team discovered, turns on a gene coding for ion channels that transport fluoride back out of the cell.

"This riboswitch is detecting fluoride buildup in the cell and turning on genes to help overcome that buildup," says Breaker. Whether or not the riboswitch is successful, and fast enough, determines whether a bacterium can fight the effects of fluoride.

"Our data not only help explain how cells fight the toxicity of fluoride, but it also gives us a sense of how we might be able to enhance the antimicrobial properties of fluoride," says Breaker. "In the future we might be able to use this knowledge to make fluoride even more toxic to bacteria." Blocking the fluoride channel, for example, makes cells 200 times more sensitive to fluoride, the researchers showed. Finding other ways to enhance fluoride's effects--by inactivating the riboswitch or shutting off other downstream genes--could make fluoride an even better antimicrobial agent.
-end-


Howard Hughes Medical Institute

Related Bacteria Articles from Brightsurf:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.

How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.

Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.

Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.

Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.

Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.

How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.

The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?

Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.

Read More: Bacteria News and Bacteria Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.