title: Fluoride and organic weak acids as respiration inhibitors for oral streptococci in acidified environments.
abstract: Oxygen metabolism (respiration) of Streptococcus mutans GS-5 involving NADH oxidases, mainly of the H(2)O-producing type, was found to be acid sensitive, as was NADH oxidase activity of cell extracts. Respiration of intact cells in acidified media was also highly sensitive to fluoride, with a 50% inhibitory concentration of about 0.02 mM at pH 4. In contrast, NADH oxidases in cell extracts were fluoride insensitive. Fluoride inhibition of respiration of intact cells was related to weak-acid effects leading to enhanced proton permeability of cells, cytoplasmic acidification and resultant acid inhibition of NADH oxidases and glycolysis. Organic weak acids, such as indomethacin and benzoate, were also effective inhibitors. H(2)O(2) production by intact cells of Streptococcus sanguis NCTC 10904, a peroxide producer, was similarly inhibited by fluoride or organic weak acids in acidified media. Thus, weak acids act as respiratory inhibitors for oral streptococci indirectly by acidifying the cytoplasm rather than acting as direct inhibitors of NADH oxidases.
authors.affiliation: Department of Microbiology & Immunology and Center for Oral Biology, University of Rochester Medical Center, Rochester, NY 14642-8672, USA.
authors.forename: T-N
authors.initials: TN
authors.lastname: Phan
authors.forename: P T M
authors.initials: PT
authors.lastname: Nguyen
authors.forename: J
authors.initials: J
authors.lastname: Abranches
authors.forename: R E
authors.initials: RE
authors.lastname: Marquis
mesh_terms: D000143:Acids / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001565:Benzoates / Q000494:pharmacology; D018441:Biofilms; D002327:Cariostatic Agents / Q000494:pharmacology*; D002457:Cell Extracts; D003470:Culture Media; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D003593:Cytoplasm / Q000187:drug effects; D005459:Fluorides / Q000494:pharmacology*; D006019:Glycolysis / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007213:Indomethacin / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010100:Oxygen / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D011522:Protons; D013295:Streptococcus mutans / Q000187:drug effects* / Q000378:metabolism; D013298:Streptococcus sanguis / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000143:Acids; D000900:Anti-Bacterial Agents; D001565:Benzoates; D002327:Cariostatic Agents; D002457:Cell Extracts; D003470:Culture Media; D016861:Cyclooxygenase Inhibitors; D009097:Multienzyme Complexes; D011522:Protons; D006861:Hydrogen Peroxide; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D005459:Fluorides; D010100:Oxygen; D007213:Indomethacin