scholarly journals Transmembrane electrical potential and transmembrane pH gradient in the acidophile Thiobacillus ferro-oxidans

1979 ◽  
Vol 178 (1) ◽  
pp. 195-200 ◽  
Author(s):  
J C Cox ◽  
D G Nicholls ◽  
W J Ingledew
Keyword(s):  
Membrane Potential ◽  
Intracellular Ph ◽  
Co2 Fixation ◽  
Electrical Potential ◽  
Sole Source ◽  
Ph Gradient ◽  
Electrochemical Gradient ◽  
Transmembrane Electrical Potential ◽  
External Ph

Thiobacillus ferro-oxidans is capable of using the oxidation of Fe2+ by O2 at pH 2.0 as the sole source of energy for growth and CO2 fixation. The bacterium maintains an intracellular pH of 6.5 over a range of external pH from 1.0 to 8.0, as measured by [14C]acetate and [3H]methylamine distribution. The membrane potential was estimated by the distribution of the lipid-soluble cation dibenzyldimethylammonium and the anion SCN-. At pH 2.0 (the pH of growth) during Fe2+ oxidation the transmembrane pH gradient is 4.5 units with an opposing membrane potential of -10mV, giving a proton electrochemical gradient of +256mV. This gradient is actively maintained.

Proton Motive Potential Difference Across the Plasma Membrane of Plant Cells: a Comparison of Cultured Cells and Protoplasts From Italian Ryegrass (Lolium multiflorum Lam.) Endosperm

1984 ◽  
Vol 11 (3) ◽  
pp. 119 ◽  
Author(s):  
RJ Henry ◽  
A Schibeci ◽  
BA Stone
Keyword(s):  
Plasma Membranes ◽  
Cultured Cells ◽  
Lolium Multiflorum ◽  
Electrical Potential ◽  
Italian Ryegrass ◽  
Ph Gradient ◽  
Cytoplasmic Ph ◽  
Transmembrane Electrical Potential ◽  
Main Component ◽  
External Ph

The electrochemical proton gradient (ΔμH+) was measured across the plasma membranes of ryegrass (Lolium multiflorum Lam.) endosperm cells grown in suspension culture. The pH gradient (ΔpH) and the transmembrane electrical potential (ΔΨ) of cells and protoplasts were compared. The pH gradient (ΔpH) was measured from the distribution of acetylsalicylic acid and 5,5-dimethyloxazolidine and the membrane potential (ΔΨ) was calculated from the distribution of the lipophilic tetraphenylphosphonium cation (TPP+) between the cells and medium. The protoplasts and cells maintained a similar ΔpH. At the external pH of the growth medium (pH 5.5), the cytoplasmic pH was about 7. Under these conditions the ΔΨ was -60 mV (negative inside) for cells and -46 mV for protoplasts. ΔpH and ΔΨ have values which vary reciprocally depending on the external pH. The main contributor to ΔμH+ at pH 4.0 is ΔpH whereas, at pH 7.0, ΔΨ is the main component. The external K+ concentration influences the cytoplasmic pH significantly only at the higher external pH values.

scholarly journals Membrane potential of mitochondria in intact lymphocytes during early mitogenic stimulation

1984 ◽  
Vol 217 (2) ◽  
pp. 453-459 ◽  
Author(s):  
M D Brand ◽  
S M Felber
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Concanavalin A ◽  
Mitochondrial Membrane ◽  
Ph Gradient ◽  
Electrochemical Gradient ◽  
Inner Membrane ◽  
Mitogenic Stimulation ◽  
Ion Movements

The mitochondrial membrane potential (delta psi m) in intact lymphocytes was calculated by measuring the distribution of radiolabelled methyltriphenylphosphonium cation. The value obtained was 120 mV. The pH gradient across the mitochondrial membrane in situ (delta pH m) was estimated to be 73 mV (1.2 pH units). Thus the electrochemical gradient of protons was about 190 mV. Addition of the mitogen concanavalin A did not alter delta psi m, showing that, if movement of Ca2+ across the inner membrane of lymphocyte mitochondria occurs when concanavalin A is added, it is accompanied by charge-compensating ion movements.

Bioenergetics of membrane transport in Synechococcus R-2 (Anacystis nidulans, S.leopoliensis) PCC7942

1998 ◽  
Vol 76 (6) ◽  
pp. 1127-1145
Author(s):  
Raymond J Ritchie
Keyword(s):  
Membrane Potential ◽  
Intracellular Ph ◽  
Anacystis Nidulans ◽  
Transport Systems ◽  
Electrochemical Gradient ◽  
Accumulation Ratio ◽  
Electrogenic Transport ◽  
Wide Range ◽  
Transport Of Ions ◽  
Photosynthesis And Respiration

Specialized chemical probe techniques need to be used to measure the membrane potential (delta psii,o) or the intracellular pH (pHi) of the cyanobacterium Synechococcus R-2 (PCC7942). The pHi of Synechococcus is essentially a set point (7.3) over a wide range of extracellular pH (pHo) from 7 to 11. Maintenance of the pHo is strongly Na+-dependent and the cells cannot tolerate acid pHo. The 86Rb+-valinomycin method of measuring the delta psii,o has inherent limitations, the most obvious being that the valinomycin treatment itself might alter the membrane potential. 201Tl+ has been found in Synechococcus to distribute across the plasmalemma passively, and so the accumulation ratio of the ion ([Tl+]i/[Tl+]o or Tl+i,o) can be used to calculate the apparent delta psii,o. The two types of probe give comparable results in Synechococcus. Polarizations of the delta psii,o of cells, because of electrogenic transport of ions, can be detected from its effects upon the uptake rate of permeant cations using both the 86Rb+-valinomycin and 201Tl+ methods. HCO3- hyperpolarized delta psii,o, whereas NH4+, CH3NH3+, and K+ led to depolarization. Most active transport systems, including the HCO3- pump, in cyanophytes appear to be ATP binding cassette (ABC) type ATP pumps. Few cotransport (H+ or Na+) driven mechanisms have been identified. A substantial proportion of the power available from photosynthesis and respiration is used to maintain ionic gradients and the membrane potential and in the light a large part (10%) is used to import inorganic carbon.Key words: cyanobacteria, membrane potential, intracellular pH, electrochemical gradient, bioenergetics.

Extracellular acidification at the surface of depolarized voltage-clamped snail neurones detected with eccentric combination pH microelectrodes

1987 ◽  
Vol 65 (5) ◽  
pp. 1001-1005 ◽  
Author(s):  
R. C. Thomas
Keyword(s):  
Membrane Potential ◽  
Intracellular Ph ◽  
Extracellular Ph ◽  
Electrochemical Gradient ◽  
Extracellular Acidification ◽  
Surface Ph ◽  
Buffering Power ◽  
Snail Neurones ◽  
Series Of Experiments ◽  
Ph Microelectrodes

A new design of double micropipette was used to measure intracellular pH, membrane potential, and surface pH of superfused snail neurones. A third double micropipette was used to control the membrane potential via a CsCl-filled barrel and inject HCl iontophoretically. In one series of experiments the surface pH fell by up to one-third of a pH unit when the membrane potential was clamped to 20 mV, pHi was initially 6.7, and extracellular pH was about 7.4 in a medium buffered either with 2 mM HEPES or 2.7% CO2 and 20 mM bicarbonate. In a second series in which surface pH was observed during brief depolarizations to different potentials with different pHi, the potential at which the surface began to acidify varied with pHi with a slope of 32 mV per pH unit. The results confirm that H+ ions leave depolarized snail neurones if the electrochemical gradient is favourable and show that CO2–bicarbonate buffered solutions have a low effective extracellular buffering power for rapid additions of acid.

Intracellular pH and Survival of Listeria monocytogenes Scott A in Tryptic Soy Broth Containing Acetic, Lactic, Citric, and Hydrochloric Acids

1991 ◽  
Vol 54 (1) ◽  
pp. 15-19 ◽  
Author(s):  
POLLA S. ITA ◽  
ROBERT W. HUTKINS
Keyword(s):  
Acetic Acid ◽  
Listeria Monocytogenes ◽  
Intracellular Ph ◽  
Cell Number ◽  
Ph Gradient ◽  
Experimental Conditions ◽  
Log Reduction ◽  
Specific Effects ◽  
Lactic Acids ◽  
External Ph

To study the effect of citric, acetic, lactic, and hydrochloric acids on Listeria monocytogenes Scott A, growth, survival, and intracellular pH (pHin) values were determined during growth in a pH-controlled fermentation vessel. Under the experimental conditions, L. monocytogenes Scott A grown in tryptic soy (plus yeast extract) broth survived even when the pH was reduced to 3.5. For most acids, L. monocytogenes maintained a pH gradient (intracellular pH-external pH) of about 1.0 pH unit and a pHin near 5.0. When the citric and lactic acid-treated cells at pH values 3.5, 4.0, and 4.5 were incubated for a longer time (24 h), both the pH gradient and the pHin values decreased. Although citric and lactic acids were more effective in lowering the pHin, acetic acid had the greatest effect on cell survival. A greater than 4-log reduction in cell number occurred when L. monocytogenes was held in acetic acid-treated broth for 24 h at pH 3.5 even though the pHin was 5.0. The results suggest that inhibition of L. monocytogenes by acids is caused not by a decrease in the intracellular pH, per se, but rather by specific effects of undissociated acid species on metabolic or other physiological activities.

Intracellular pH and membrane potassium conductance in rabbit distal colon

1990 ◽  
Vol 258 (2) ◽  
pp. C336-C343 ◽  
Author(s):  
M. E. Duffey ◽  
D. C. Devor
Keyword(s):  
Membrane Potential ◽  
Intracellular Ph ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Potassium Conductance ◽  
Co2 Concentration ◽  
Distal Colon ◽  
Bathing Solution ◽  
Electrical Potential Difference ◽  
K Concentration

Intracellular pH (pHc) was measured in the short-circuited epithelium of rabbit distal colon using H(+)-selective microelectrodes. pHc was 6.91 +/- 0.02 (SE) when the bath pH was 7.4. Intracellular HCO3- activity (acHCO3-) was estimated from these measurements to be 8 +/- 0 mM. When we replaced all Cl- in the tissue bathing solutions with the impermeant anion gluconate, pHc rose to 7.44 +/- 0.08 and acHCO3- increased to 30 +/- 6 mM. These results demonstrate that this tissue contains a Cl(-)-HCO3- exchange mechanism. During the Cl- replacement the apical membrane electrical potential difference hyperpolarized from -55 +/- 1 to -74 +/- 3 mV, suggesting that membrane ionic conductance had changed. Elevation of either the apical or basolateral membrane bathing solution K+ concentration produced a greater depolarization of membrane potential during Cl- replacement than when tissues were bathed in normal electrolyte solutions. In additional experiments, pHc was raised by lowering the bath CO2 concentration while the bath Cl- concentration was kept normal. Under these conditions, membrane potential hyperpolarized and was more sensitive to the elevation of bath K+ concentration than when pHc was normal. These results suggest that membrane K+ conductance in this tissue is increased by intracellular alkalinization.

scholarly journals Complementary and Overlapping Selectivity of the Two-Peptide Bacteriocins Plantaricin EF and JK

1999 ◽  
Vol 181 (16) ◽  
pp. 4848-4852 ◽  
Author(s):  
Gert N. Moll ◽  
Emile van den Akker ◽  
Håvard H. Hauge ◽  
Jon Nissen-Meyer ◽  
Ingolf F. Nes ◽  
...  
Keyword(s):  
Lactobacillus Plantarum ◽  
Ion Selectivity ◽  
Electrical Potential ◽  
High Conductivity ◽  
Ph Gradient ◽  
Target Cells ◽  
Monovalent Cations ◽  
Transmembrane Electrical Potential

ABSTRACT Plantaricin EF and JK are both two-peptide bacteriocins produced byLactobacillus plantarum C11. The mechanism of plantaricin EF and JK action was studied on L. plantarum 965 cells. Both plantaricins form pores in the membranes of target cells and dissipate the transmembrane electrical potential (Δψ) and pH gradient (ΔpH). The plantaricin EF pores efficiently conduct small monovalent cations, but conductivity for anions is low or absent. Plantaricin JK pores show high conductivity for specific anions but low conductivity for cations. These data indicate that L. plantarum C11 produces bacteriocins with complementary ion selectivity, thereby ensuring efficient killing of target bacteria.

Contributions of K+:Cl- cotransport and Na+/K+-ATPase to basolateral ion transport in malpighian tubules of Drosophila melanogaster

1999 ◽  
Vol 202 (11) ◽  
pp. 1561-1570 ◽  
Author(s):  
S.M. Linton ◽  
M.J. O'Donnell
Keyword(s):  
Drosophila Melanogaster ◽  
Membrane Potential ◽  
Cyclic Amp ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Minor Role ◽  
Electrochemical Gradient ◽  
Tubule Cells

Mechanisms of Na+ and K+ transport across the basolateral membrane of isolated Malpighian tubules of Drosophila melanogaster were studied by examining the effects of ion substitution and putative inhibitors of specific ion transporters on fluid secretion rates, basolateral membrane potential and secreted fluid cation composition. Inhibition of fluid secretion by [(dihydroindenyl)oxy]alkanoic acid (DIOA) and bumetanide (10(−)4 mol l-1) suggested that a K+:Cl- cotransporter is the main route for K+ entry into the principal cells of the tubules. Differences in the effects of bumetanide on fluxes of K+ and Na+ are inconsistent with effects upon a basolateral Na+:K+:2Cl- cotransporter. Large differences in electrical potential across apical (>100 mV, lumen positive) and basolateral (<60 mV, cell negative) cell membranes suggest that a favourable electrochemical gradient for Cl- entry into the cell may be used to drive K+ into the cell against its electrochemical gradient, via a DIOA-sensitive K+:Cl- cotransporter. A Na+/K+-ATPase was also present in the basolateral membrane of the Malpighian tubules. Addition of 10(−)5 to 10(−)3 mol l-1 ouabain to unstimulated tubules depolarized the basolateral potential, increased the Na+ concentration of the secreted fluid by 50–73 % and increased the fluid secretion rate by 10–19 %, consistent with an increased availability of intracellular Na+. We suggest that an apical vacuolar-type H+-ATPase and a basolateral Na+/K+-ATPase are both stimulated by cyclic AMP. In cyclic-AMP-stimulated tubules, K+ entry is stimulated by the increase in the apical membrane potential, which drives K+:Cl- cotransport at a faster rate, and by the stimulation of the Na+/K+-ATPase. Fluid secretion by cyclic-AMP-stimulated tubules was reduced by 26 % in the presence of ouabain, suggesting that the Na+/K+-ATPase plays a minor role in K+ entry into the tubule cells. Malpighian tubules secreted a Na+-rich (150 mmol l-1) fluid at high rates when bathed in K+-free amino-acid-replete saline (AARS). Secretion in K+-free AARS was inhibited by amiloride and bafilomycin A1, but not by bumetanide or hydrochlorothiazide, which inhibit Na+:Cl- cotransport. There was no evidence for a Na+ conductance in the basolateral membrane of unstimulated or cyclic-AMP-stimulated tubules. Possible mechanisms of Na+ entry into the tubule cells include cotransport with organic solutes such as amino acids and glucose.

scholarly journals Evidence for an electrogenic 3-deoxy-2-oxo-d-gluconate–proton co-transport driven by the protonmotive force in Escherichia coli K12

1977 ◽  
Vol 168 (2) ◽  
pp. 211-221 ◽  
Author(s):  
A Lagarde
Keyword(s):  
Escherichia Coli ◽  
Membrane Potential ◽  
Membrane Vesicles ◽  
Ph Gradient ◽  
Protonmotive Force ◽  
Chemical Gradient ◽  
Escherichia Coli K12 ◽  
Relative Contribution ◽  
Isolated Membrane Vesicles ◽  
External Ph

Evidence is presented indicating that the carrier-mediated uptake of 3-deoxy-2-oxo-D-gluconate and D-glucuronate in Escherichia coli K12 is driven by the deltapH and deltapsi components of the protonmotive force. 1. Approximately two protons enter the cells with each sugar molecule, independent of the sugar and the strain used. 2. In respiring cells, the magnitude of the pH gradient alone, as measured by distribution of [3H]acetate, appears to be insufficient to account for the chemical gradient of 3-deoxy-2-oxo-D-gluconate that is developed between pH 6.0 and 8.0. 3. If the external pH is varied between 5.5 and 8.0, 3-deoxy-2-oxo-D-gluconate uptake is gradually inhibited by valinomycin plus K+ ions, whereas the inhibition caused by nigericin is concomitantly relieved, thus reflecting the relative contribution of deltapH and deltapsi to the total protonmotive force at each external pH. 4. 3-Deoxy-2-oxo-D-gluconate can be transiently accumulated into isolated membrane vesicles in response to an artificially induced pH gradient. The process is stimulated when the membrane potential is collapsed by valinomycin in the presence of K+ ions.

Sign in / Sign up

Export Citation Format

Share Document