title: Flow cytometry analysis of germinating Bacillus spores, using membrane potential dye.
abstract: Germination of Bacillus anthracis spores is necessary for the transcription of plasmidic genes essential to the infection. Assessing germination potential is crucial to predict the risk associated with pathogenic Bacillus exposure. The aim of this study was to set up a viability assay based on membrane potential in order to predict the earliest germination event of spores. B. cereus and two strains of B. subtilis were used. The spores were isolated with a sodium bromide gradient. Approximately 10(7) spores were incubated at 37 degrees C in tryptic soy broth (TSB). Aliquots were harvested at predetermined times and stained with 3,3'-dihexyloxacarbocyanine iodide [DiOC(6)(3)] or with bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC(4)(3)]. Fluorescence characteristics were obtained using flow cytometry. The earliest detectable activation of membrane potential occurred after 15 min of incubation in TSB using DiOC(6)(3). Using DiBAC(4)(3), the earliest detectable signal was after 4 h of incubation. Control experiments using carbonyl cyanide m-chlorophenylhydrazone (CCCP)-treated spores did not show any change in the fluorescence intensity over time. Since no membrane potential and no germination were detected in CCCP-treated spores, the activation of membrane potential seems to be associated with germination. DiOC(6)(3) can be used as an early membrane potential indicator for spores. DiBAC(4)(3), by contrast, is not a early membrane potential marker.
authors.affiliation: Institut Universitaire de cardiologie et de pneumologie, Centre de recherche Hôpital Laval, Université Laval, 2725 Chemin Ste-Foy, Ste-Foy, QC, Canada, G1V 4G5.
authors.forename: Christian
authors.initials: C
authors.lastname: Laflamme
authors.forename: Jim
authors.initials: J
authors.lastname: Ho
authors.forename: Marc
authors.initials: M
authors.lastname: Veillette
authors.forename: Marie-Chantal
authors.initials: MC
authors.lastname: de Latrémoille
authors.forename: Daniel
authors.initials: D
authors.lastname: Verreault
authors.forename: Anne
authors.initials: A
authors.lastname: Mériaux
authors.forename: Caroline
authors.initials: C
authors.lastname: Duchaine
mesh_terms: D001407:Bacillus / Q000502:physiology*; D002232:Carbocyanines; D005434:Flow Cytometry / Q000379:methods*; D008564:Membrane Potentials; D013171:Spores, Bacterial / Q000502:physiology
chemical_list: D002232:Carbocyanines; C007392:3,3'-dihexyl-2,2'-oxacarbocyanine