title: Bacterial fluoride resistance, Fluc channels, and the weak acid accumulation effect.
abstract: Fluoride ion (F(-)) is a ubiquitous environmental threat to microorganisms, which have evolved a family of highly selective "Fluc" F(-) channels that export this inhibitory anion from their cytoplasm. It is unclear, however, how a thermodynamically passive mechanism like an ion channel can protect against high concentrations of external F(-). We monitored external F(-) concentrations in Escherichia coli suspensions and showed that, in bacteria lacking Fluc, F(-) accumulates when the external medium is acidified, as a predicted function of the transmembrane pH gradient. This weak acid accumulation effect, which results from the high pKa (3.4) and membrane permeability of HF, is abolished by Fluc channels. We also found that, although bacterial growth is inhibited by high concentrations of F(-), bacteria can withstand cytoplasmic F(-) at levels a hundred times higher than those that inhibit proliferation, resuming growth when the F(-) challenge is removed.
authors.affiliation: Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02453 Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02453.
authors.forename: Chunhui
authors.initials: C
authors.lastname: Ji
authors.affiliation: Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02453 Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02453.
authors.forename: Randy B
authors.initials: RB
authors.lastname: Stockbridge
authors.affiliation: Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02453 Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02453 cmiller@brandeis.edu.
authors.forename: Christopher
authors.initials: C
authors.lastname: Miller
mesh_terms: D049109:Cell Proliferation; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005459:Fluorides / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport
chemical_list: D029968:Escherichia coli Proteins; D007473:Ion Channels; D005459:Fluorides