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Scientists have found a mechanism to protect bacteria from fluoride
Last reviewed: 01.07.2025
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Scientists from Yale (USA) have uncovered molecular tricks used by bacteria to counteract fluoride, which is found in toothpastes and mouthwashes to combat cavities.
In the December issue of Science Express, the researchers report that sections of RNA called riboswitches, which control gene expression, detect fluoride build-up and activate bacteria's defenses against its effects, including promoting tooth decay.
"Riboswitches are specialized detectors that recognize fluoride," says Henry Ford II, professor, chair of the department of molecular and cellular biology, and senior author of the study.
Fluoride is an ingredient in many toothpastes that significantly reduces the development of dental caries. Fluoride-containing toothpastes have been available since the 1950s.
Riboswitches counteract the effects of fluoride on bacteria. "If fluoride accumulates to toxic levels in a cell, the riboswitch grabs the fluoride and then activates genes that can block its action," Brecker said.
"We were stunned when we found fluorine-capturing riboswitches," Brecker said. "Scientists had argued that an RNA molecule was not a good choice for use as a sensor for fluorine because fluorine and RNA molecules are negatively charged and should not interact. Yet we found more than 2,000 such RNAs in many organisms."
By tracking riboswitches in numerous bacterial species, the team found that these RNAs are ancient molecules, and that many microorganisms have learned to overcome toxic levels of fluoride throughout their history. Bacteria that thrive in the human mouth have also been shown to have riboswitches that protect against fluoride toxicity.
"Cells have had to deal with fluoride toxicity for billions of years, so they've developed mechanisms to deal with it," said the study's author. Now that these defense mechanisms are known, scientists may be able to manipulate these processes and make fluoride more effective at fighting bacteria. Scientists at Yale University have discovered protein channels through which fluoride is pumped out of cells. Blocking these channels will cause fluoride to accumulate in bacteria, making it more effective at fighting cavities.
Fluoride is the 13th most abundant element in the earth's crust. Its use in toothpaste and water treatment began a controversy 60 years ago that continues today. In the UK and other European Union countries, fluoride is used to a much lesser extent because of fierce public opposition.
Excess fluoride has a major negative impact on human health. Fluoride accumulation extracts magnesium from blood lymph, promotes calcium leaching from bone tissue, which in turn settles in the muscles, lungs and kidneys of a person. Fluoride salts accumulate in bones, causing osteochondrosis, affecting the shape, color and direction of tooth growth, the condition and mobility of joints, and the formation of bone growths.
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