title: Comparison of polyvinyl chloride membrane electrodes sensitive to alkylphosphonium ions for the determination of the electrical difference (delta psi) of Streptococcus mutans and Lactobacillus casei.
abstract: Polyvinyl chloride membrane electrodes sensitive to tetraphenyl phosphonium (TPP+), butyltriphenyl phosphonium ( bTPP +), and methyltriphenyl phosphonium ( mTPP +) ions have been compared for the determination of the electrical potential difference (delta psi) of the oral bacteria, Streptococcus mutans DR0001 /6 and Lactobacillus casei RB1014 . All three types of electrode proved suitable for determining delta psi, although the TPP+-sensitive electrode was particularly susceptible to interference by protonmotive force (delta p) dissipators known to inhibit sugar uptake by the bacteria. The mTPP +-sensitive electrode was the least affected. Similarly, both strains had a high nonspecific binding capacity for TPP+ and bTPP + ions, and this increased for all three ions when the bacteria were heated to 80 degrees C for 1 h to abolish glucose uptake and metabolism. This heat-treatment procedure is therefore not a suitable control for determination of nonspecific binding to cells. However, 1% (v/v) toluene, 20 microM gramicidin, or 10 microM valinomycin effectively depolarized the bacteria without interfering with nonspecific binding. The ionophores were therefore used subsequently for the determination of nonspecific binding of the lipid-soluble cations. The mTPP + ion and corresponding electrode proved the most effective system, and delta psi values of -89 and -107 mV were obtained for S. mutans and L. casei, respectively, harvested from glucose-limited continuous cultures and incubated in 100 mM Hepes-KOH buffer (pH 7.0), containing 1 mM dithiothreitol and 10 mM glucose. Although the delta psi of S. mutans decreased significantly in the presence of Mes-KOH and potassium phosphate buffers at pH 7.0, it increased to -119 mV in Tris-HCl buffer (pH 7.0).(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D001693:Biological Transport, Active; D004563:Electrochemistry / Q000295:instrumentation*; D004566:Electrodes; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007780:Lacticaseibacillus casei / Q000378:metabolism*; D008564:Membrane Potentials; D008567:Membranes, Artificial; D009055:Mouth / Q000382:microbiology; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D011143:Polyvinyl Chloride; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013295:Streptococcus mutans / Q000378:metabolism*; D014320:Triphenylmethyl Compounds
chemical_list: D008567:Membranes, Artificial; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; C032536:butyltriphenylphosphonium; D011143:Polyvinyl Chloride; D012964:Sodium; D005947:Glucose; D011188:Potassium; C013289:tetraphenylphosphonium