New Insight on the Response of Bacteria to Fluoride

Aqueous F− at 10-100 μM inhibits phosphoryl-transfer enzymes essential for energy production and nucleic acid synthesis, making it potentially toxic to cells.

“Aqueous F−, ubiquitous in the environment at 10–100-µM levels, is potentially toxic to cells because at these concentrations it inhibits phosphoryl-transfer enzymes essential for energy production and nucleic acid synthesis (Adamek et al., 2005; Breaker, 2012).”

CrcB export proteins function as passive fluoride-specific ion channels that require Na+ ions for transport activity.

“In contrast, CrcB export proteins function as passive fluoride-specific ion channels that require Na+ ions for transport activity (4, 5, 23–26).”

At sublethal concentrations, fluoride disrupts microbial metabolic processes by inhibiting key enzymes such as enolase and pyrophosphatases, often by forming complexes with essential metal cofactors.

“At sublethal concentrations, fluoride disrupts metabolic processes by inhibiting key enzymes, such as enolase and pyrophosphatases, often by forming complexes with essential metal cofactors (4, 5).”

ΔFluc E. coli is hypersensitive to F− in pH-neutral media, and this effect is reversed by expressing F− exporters with a rescue plasmid.

“In previous work, a Fluc-knockout (ΔFluc) strain of E. coli was shown to be hypersensitive to F−, as assessed by growth in pH-neutral media, and this effect could be reversed by expressing F− exporters in the bacteria with a rescue plasmid (Breaker, 2012; Stockbridge et al., 2012).”

Plasma membranes of many bacteria, yeasts, and protozoa carry F− exporter proteins to maintain cytoplasmic F− below inhibitory concentrations.

“Accordingly, plasma membranes of many bacteria, yeasts, and protozoa carry F− exporter proteins to maintain cytoplasmic F− below inhibitory concentrations (Breaker, 2012; Stockbridge et al., 2012, 2013; Li et al., 2013).”

Proteins expressed via fluoride riboswitches include higher copy numbers of enolase, stress genes, DNA repair functions and hypothetical proteins.

“Proteins expressed via fluoride riboswitches include higher copy numbers of enolase, stress genes, DNA repair functions and hypothetical proteins.”

Thousands of fluoride-sensing riboswitches have been discovered in many diverse bacterial strains.

“On the first point, thousands of fluoride‐sensing riboswitches (Fig. 5) have been discovered in many diverse bacterial strains (Baker et al., 2012; Breaker, 2012).”