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At least 19 recordsLinked to original sources
PubMed1976

Proton-motive force and the motile behavior of Bacillus subtilis.

Changes in the proton-motive force cause a transient change in the motile behavior of Bacillus subtilis cells. Both an increase and a decrease in the proton-motive force caused transient tumbling. Simultaneous decrease of proton-motive force and increase of attractant concentration lessens the response toward the attractant. A simultaneous increase of proton-motive force and increase of attractant concentration prolonges the response toward attractant. A hypothesis explaining the various effects is given.

Bacillus subtilis↗
PubMed1978

Energy supply for active transport in anaerobically grown Escherichia coli.

Escherichia coli K-12, grown under anaerobic conditions with glucose as the sole source of carbon and energy without any terminal electron acceptor added, contains a fumarate reductase system in which electrons are transferred from formate or reduced nicotinamide adenine dinucleotide via menaquinone and cytochromes to fumarate reductase. This fumarate reductase system plays an important role in the metabolic energy supply of E. coli, grown under so-called "glycolytic conditions," as is indicated by the growth yields and maximal growth rates of mutants impaired in electron transfer or adenosine triphosphatase (uncB). In mutants deficient in menaquinone, cytochromes, or fumarate reductase, these values are considerably lower than in mutants deficient in ubiquinone or a functional adenosine triphosphatase. Electron transfer in this fumarate reductase system leads to the generation of a membrane potential, as is indicated by the uptake of the lipophilic cation triphenylmethylphosphonium by membrane vesicles prepared from cytochrome-sufficient and uncB cells. The generation of a proton-motive force by the fumarate reductase system was also demonstrated by the uptake of amino acids under anaerobic conditions in membrane vesicles of cytochrome containing and uncB cells grown under glycolytic conditions. Membrane vesicles of cytochrome-deficient cells failed to accumulate triphenyl-methylphosphonium and amino acids under these conditions, indicating that cytochromes are essential for the generation of a proton-motive force. Using glutamine uptake as an indication of the generation of ATP and proline uptake as an indication of the generation of a proton-motive force, it was demonstrated in whole cells that the proton-motive force is formed by ATP hydrolysis in cytochrome-deficient cells and by electron transfer in the uncB cells. In cytochrome-containing cells it was not possible to distinguish between these two possibilities, but the growth parameters suggest that, under glycolytic conditions, the proton-motive force is generated via electron transfer in the fumarate reductase system rather than via ATP hydrolysis.

Adenosine Triphosphate↗
PubMed1976

Energy coupling in the active transport of amino acids by bacteriohodopsin-containing cells of Halobacterium holobium.

Growth of Halobacterium halobium under illumination with limiting aeration induces bacteriorhodopsin formation and renders the cells capable of photophosphorylation. Cells depleted of endogenous reserves by a starvation treatment were used to investigate the means by which energy is coupled to the active transport of [14C]proline, -leucine, and -histidine. Proline was readily accumulated by irradiated cells under anaerobiosis even when the photophosphorylation was abolished by the adenosine triphosphatase inhibitor N,N'-dicyclohexylcarbodimiide (DCCD). The uptake of proline in the dark was limited except when the cells were allowed to accumulate adenosine 5'-triphosphate (ATP) by prior light exposure or by the oxidation of glycerol. DCCD inhibited this dark uptake. These findings essentially support Mitchell's chemiosmotic theory of active transport. The driving force is apparently the proton-motive force developed when protons are extruded from irradiated bacteriorhodopsin or by the dydrolysis of ATP by membrane adenosine triphosphatase. Carbonylcyanide m-chlorophenylhydrazone (CCCP), a proton permeant known to abolish membrane potential, was a strong inhibitor of proline uptake. Leucine transport was also apparently driven by proton-motive force, although its kinetic properties differed from the proline system. Histidine transport is apparently not a chemiosmotic system. Dark- or light-exposed cells show comparable initial rats of histidine uptake, and these processes were only partially inhibited by DCCD or CCCP. The histidine system apparently does not utilize ATP per se since comparable rates of uptake were exhibited by cells of differing intracellular ATP levels. Irradiated cells did effect a greater total accumulation of histidine than dark-exposed cells. These findings suggest that ATP is needed for sustained transport.

Adenosine Triphosphatases↗
PubMed1976

Light-induced membrane potential and pH gradient in Halobacterium halobium envelope vesicles.

Illumination of envelope vesicles prepared from Halobacterium halobium cells causes translocation of protons from inside to outside, due to the light-induced cycling of bacteriorhodopsin. This process results in a pH gradient across the membranes, an electrical potential, and the movements of K+ and Na+. The electrical potential was estimated by following the fluorescence of a cyanine dye, 3,3'-dipentyloxadicarbocyanine. Illumination of H. halobium vesicles resulted in a rapid, reversible decrease of the dye fluorescence, by as much as 35%. This effect was not seen in nonvesicular patches of purple membrane. Observation of maximal fluorescence decreases upon ilumination of vesicles required an optimal dye/membrane protein ratio. The pH optimum for the lightinduced fluorescence decrease was 6.0. The decrease was linear with actinic light intensity up to about 4 X 10(5) ergs cn-2 s-1. Valinomycin, gramicidin, and triphenylmethylphosphonium ion all abolished the fluorescence changes. However, the light-induced pH change was enhanced by these agents. Conversely, buffered vesicles showed no pH change but gave the same or larger fluorescence changes. Thus, we have identified the fluorescence decrease with a light-induced membrane potential, inside negative. By using valinomycin-K+-induced membrane potentials, we calibrated the fluorescence decrease with calculated Nernst diffusion potentials. We found a linear dependence between potential and fluorescence decrease of 3 mV/%, up to 90 mV. When the envelope vesicles were illuminated, the total proton-motive force generated was dependent on the presence of Na+ and K+ and their concentration gradients across the membrane. In general, K+ appeared to be more permeable than Na+ and, thus, permitted development of greater pH gradients and lower electrical potentials. By calculating the total proton-motive force from the sum of the pH and potential terms, we found that the vesicles can produce proton-motive forces near--200 mV.

Cell Membrane↗
PubMed1975

Accumulation of arsenate, phosphate, and aspartate by Sreptococcus faecalis.

Uptake of arsenate and phosphate by Streptococcus faecalis 9790 is strictly dependent on concurrent energy metabolism and essentially unidirectional. targinine supports uptake only in presence of glycerol or related substances; glycerol is not directly involved in transport but depletes the cellular orthophosphate pool and thus relieves feedback inhibition of transport. Uptake of phosphate and arsenate is stimulated by K+ and by other permeant cations. The results suggest that electroneutrality is preserved by compensatory movement of either H+ or OH minus. Ionophores and N,N'-dicyclohexylcarbodiimide, which prevent establishment of a proton motive force, block the accumulation of thiomethylgalactoside and of threonine but not that of arsenate or phosphate. We conclude that arsenate accumulation requires adenosine 5'-triphosphate but is not driven by the proton-motive force. However, conditions and reagents that lower the cytoplasmic pH do inhibit accumulation of arsenate and phosphate, suggesting that uptake depends on the capacity of the cells to maintain a neutral or alkaline cytoplasm. We therefore propose that phosphate accumulation is an electroneutral exchange for OH driven by adenosine 5'-triphosphate or by a metabolite thereof. Accumulation of aspartate and glutamate also requires adenosine 5'-triphosphate but not the proton-motive force and may involve a similar mechanism.

Adenosine Triphosphate↗
PubMed1978

Control of the chemotactic behavior of Bacillus subtilis cells.

The effects of nigericin, valinomycin and some lipophilic cations on the motile behavior of non-starved and methionine-straved Bacillus subtilis cells were studied. For valinomycin and nigericin a quantitative relationship between the flux in the proton-motive force and the duration of the twiddle response was found. Lipophilic cations bind to the ion gate controlling the twiddle frequency and thereby cause the cells to swim smoothly. To explain the transmission of the chemotactic signal a model is given in which receptors, a hyperpolarizing wave, an ion gate and two methylation sites, viz. methyl-accepting chemotaxis proteins and a further methylation site (MT), play a role. For the transmission of the signal caused by an attractant both the hyperpolarizing wave and an interaction between receptor and methylation site (MT) are needed. The methyl-accepting chemotaxis proteins are involved in the adaptation/deadaptation to altered levels of attractant. Artificial changes in the proton-motive force act directly on the ion gate, which finally controlls the twiddle frequency of the cells.

Anti-Bacterial Agents↗
PubMed1979

Inactive to active transitions of the mitochondrial ATPase complex as controlled by the ATPase inhibitor.

The hydrolytic and phosphorylation activities of the ATPase complex of bovine heart mitochondria are regulated by the ATPase inhibitor of Pullman and Monroy [1]. The inhibiting action of the peptide on ATPase activity can be overcome by a proton-motive force. Submitochondrial particles that contain the inhibitor, either intrinsically or externally added, show a lag that precedes phosphorylation. Particles devoid of the inhibitor, of particles that are in an 'active' state fail to present the lag. Accordingly, the data indicate that, prior to the onset of phosphorylation, the ATPase complex undergoes a transition to an active state through a process that involves the inhibitor. The transition depends on the concentration of ATP, 50 microM ATP giving 50% inhibition of the proton-motive force-induced transition.

Adenosine Triphosphatases↗
PubMed1977

Light energy conservation processes in Halobacterium halobium cells.

In Halobacterium halobium, proton pumping driven by light or by respiration generates an electrochemical potential difference across the membrane. Energy storage in this form is only transient. Cellular energy transducers competing with proton leaks stabilize this free energy as high energy phosphate bonds, electrochemical potential of other ions, and chemical potential of amino acids and possibly other chemical species. The pH changes induced by light or by respiration in cell suspensions are complicated by proton flows associated with the functioning of the cellular energy transducers. Dominant is the proton inflow coupled to the synthesis of ATP, which has been kinetically resolved. A proton-per-ATP ratio of about 3 is calculated from simultaneous measurements of photophosphorylation and the proton inflow. This value is compatible with the chemiosmotic coupling hypothesis. The time course of the light-induced changes in membrane potential indicates that light-driven pumping increases a dark preexisting potential of about 130 mV only by a small amount (20-30 mV). The complex kinetic features of the membrane potential changes do not closely follow those of the pH changes, indicating that flows of ions other than protons are involved. A qualitative model consistent with the available data is presented. A salient feature of this model is a sudden relaxation of the protonmotive force by a proton inflow through the ATPase when the preexisting protonmotive force is increased by light or respiration and reaches a critical value. The trigger could be either the proton-motive force, the pH gradient, or possibly the internal pH.

Aerobiosis↗
PubMed1978

Phosphate transport in membrane vesicles from Escherichia coli.

Escherichia coli strain AN710 possesses only the PIT system for phosphate transport. Membrane vesicles from this strain, which contain phosphate internally, perform exchange and active transport of phosphate. The energy for active transport is supplied by the respiratory chain with ascorbate phenazine methosulphate as electron donor. To a lesser extent also the oxidation of D-lactate energizes phosphate transport; the oxidation of succinate is only marginally effective. Phosphate transport is driven by the proton-motive force and in particular by the pH gradient across the membrane. This view is supported by the observation that phosphate transport is stimulated by valinomycin, inhibited by nigericin and abolished by the uncoupler carbonyl cyanide m-chlorophenylhydrazone. Neither inhibitor affects phosphate exchange. The phosphate analogue arsenate inhibits both the exchange reaction and active transport. Both processes are stimulated by K+ and Mg2+, the highest activities being observed with both ions present. Membrane vesicles have also been isolated from Escherichia coli K10, a strain which possesses only a functional PST phosphate transport system. These vesicles perform neither exchange nor active transport of phosphate, although active transport of amino acids is observed in the presence of ascorbate-phenazine methosulphate or D-lactate.

Bacteriolysis↗
PubMed1979

Rapid pH and deltamuH+ jump by short laser pulse.

The excited state (S1) of sulfononaphthols has a pK value well below that of the ground state, consequently intensive illumination of their aqueous solution should lead to acidification. In this study the second harmonies of a ruby laser pulse (10 MW, 30 ns at 347.2 nm) were used for excitation of a sulfononaphthol solution, resulting in a lowering of the pH from 8 to 4. The change in pH was demonstrated by spectral changes of the pH indicators Bromocresol Green, Bromothymol Blue, Bromocresol Purple and Phenol Red. The magnitude of the pH change was calculated from the kinetics of the changes in the indicators' absorbance and from fluorescence intensity of naphtholate. Sulfononaphthols, due to their hydrophylic nature, cannot permeate across phospholipid membranes. Taking advantage of this property, liposomes containing sulfononaphthol were prepared and irradiated by the laser pulse. Evidence is given that under such conditions the change in pH was limited to the space enclosed in the liposomes. The resulting proton-motive force (deltamuH+ = 180 -- 240 mV) is adequate for perturbing the energy-coupled reactions of oxidative phosphorylation. Possible applications of this technique in chemical physics, chemistry, biochemistry and bioenergetics are discussed.

Hydrogen-Ion Concentration↗
PubMed2026

Oxygen-responsive bacterial glycosphingolipid links symbiont fitness and immune development in neonatal host.

Symbiotic gut bacteria must re-establish themselves in every host generation, yet the molecular strategies enabling this inheritance remain poorly understood. Here, we show that Bacteroides fragilis uses a membrane glycolipid, alpha-galactosylceramide (BfaGC), to colonize the neonatal gut. Genome-wide fitness profiling revealed that BfaGC biosynthesis is selectively required during early life, when transient oxygenation creates a physiological bottleneck for strict anaerobes. Mechanistically, BfaGC reduces membrane proton permeability, sustaining the proton-motive force that supports aerobic respiration. This oxygen-responsive adaptation simultaneously generates a host-facing immunomodulatory signal that calibrates neonatal natural killer T (NKT) cell development, linking bacterial fitness to immune maturation through a single metabolite. The same mechanism also enables niche expansion by enterotoxigenic strains, revealing context-dependent consequences. Notably, this strategy is distinct among gut Bacteroidales: other prominent members synthesize a different sphingolipid subclass supporting broader fitness, implying divergent evolutionary strategies. Our findings provide time-resolved insight into how bacterial metabolites shape host-microbiota symbiosis across development.

Bacteroides fragilis↗
PubMed1979

Energy coupling to the transport of inorganic phosphate in Escherichia coli K12.

The nature of the energy source for phosphate transport was studied in strains of Escherichia coli in which either one of the two major systems (PIT, PST) for phosphate transport was present. In the PIT system, phosphate transport is coupled to the proton-motive force. The energy source for the PST system appears to be phosphate-bond energy, as has been found in other systems involving binding proteins. High concentration gradients of phosphate (between 100 and 500) are established by both systems.

Aerobiosis↗
PubMed1977

Comparison of the effects of two lipophilic acids, hexachlorophene and decanoate, on Bacillus subtilis.

The minimal growth-inhibitory amount of either hexachlorophene (HCP) or decanoate stopped growth, respiration, adenosine 5'-triphosphate synthesis, and amino acid transport of Bacillus subtilis in a culture containing amino acids and citrate as carbon sources. The electron transport system was not affected by this dose. Addition of 27.8 mM glucose or 10 mM malate to an inhibited culture did not reverse the binding of HCP or decanoate to the cells, but it allowed resumption of growth, respiration, and adenosine 5'-triphosphate synthesis, as the glucose or malate then supplied the needed carbon. The addition of glucose or malate did not reverse amino acid transport inhibition caused by decanoate, but it did reverse that due to HCP. However, if the dose of HCP was raised in the presence of glucose or malate, only growth and amino acid transport were affected; this indicates that both HCP and decanoate act at their minimal growth inhibitory doses by inhibiting substrate transport. As active transport of amino acids and ketoacids depends on the proton gradient and the membrane potential of the cells, we conclude that the primary effect of these lipophilic acids is the destruction of the proton-motive force.

Adenosine Triphosphate↗
PubMed1978

ATP hydrolysis and synthesis by the membrane-bound ATP synthetase complex of Methanobacterium thermoautotrophicum.

The membrane-bound ATP synthetase complex of Methanobacterium thermoautotrophicum showed maximum activity for ATP hydrolysis at pH 8, at temperatures between 65 and 70 degrees C, and at an ATP-Mg2+ ratio of 0.5. Anaerobic conditions were not prerequisite for enzyme activity. The enzyme showed a Km value for ATP of 2 mM, and activity was Mg2+ dependent; Mn2+, Co2+, Ca2+, and Zn2+ could replace Mg2+ to some extent. Other nucleoside triphosphates could be hydrolyzed. N,N'-dicyclohexylcarbodiimide inhibited ATP hydrolysis. A proton-motive force, artificially imposed by a pH shift or valinomycin, resulted in ATP synthesis in whole cells. The ATP synthetase complex of the thermophilic methanogenic bacterium is similar to those described in aerobic and anaerobic microorganisms.

Adenosine Diphosphate↗
PubMed1976

Speculations on the evolution of ion transport mechanisms.

Primate cells evolved a plasma membrane to restrict the loss of important molecules. The osmotic problems that then arose were solved in one of several ways. Of major importance was the evolution of specific ion pumps, to actively extrude those salts whose inward diffusion would have led to swelling and lysis. In addition, these pumps allowed the cell to store energy in the form of ion gradients across the membrane. Thus, even in the earliest stages, the evolution of ion transport systems coincided with the development of mechanisms which catalyzes the energy transformations. It is postulated that an "ATP"-driven proton pump was one of the first ion transport systems. Such a proton pump would extrude hydrogen ions from the cell, establishing both a transmembrane pH gradient (alkaline inside) and a membrane potential (negative inside). This difference in electrochemical potential for protons (the proton-motive force) could then drive a variety of essential membrane functions, such as the active transport of ions and nutrients. A second major advance was the evolution of an ion transport system that converted light energy into a form which could be used by the cell. The modern model for this is the "purple membrane" of Halobacterium halobium, which catalyzes the extrusion of protons after the capture of light. The protonmotive force generated by such a light-driven proton pump could then power net synthesis of ATP by a reversal of the ATP-driven proton pump. A third important evolutionary step associated with ion transport was the development of a system to harness energy released by biological oxidations. Again, the solution of this problem was to conserve energy as a protonmotive force by coupling the activity of a respiratory chain to the extrusion of protons. Finally, with the development of animal cells a more careful regulation of internal and external pH was required. Thus, an ATP-driven Na+-K+ pump replaced the proton-translocating ATPase as the major ion pump found in plasma membranes.

Adenosine Triphosphatases↗
PubMed1977

Evidence for energy-dependent change in phosphate binding for mitochondrial oxidative phosphorylation based on measurements of medium and intermediate phosphate-water exchanges.

Characteristics of the exchange reactions catalyzed by beef heart submitochondrial particles give new insight into energy transducing steps of oxidative phosphorylation. The uncoupler-insensitive portion of the total Pi in equilibrium HOH exchange in presence of ATP, ADP, and Pi is the intermediate Pi in equilibrium HOH exchange, that is the exchange occurring with Pi formed by hydrolysis of ATP prior to release of Pi from the catalytic site. The exchange of medium Pi with HOH is as sensitive to uncouplers as the Pi in equilibrium ATP exchange and net oxidative phosphorylation, demonstrating a requirement of an uncoupler-sensitive energized state, probably a transmembrane potential or proton gradient, for bringing medium Pi to the reactive state. The covalent bond forming and breaking step at the catalytic site (ADP + Pi in equilibrium ATP + HOH) appears relatively insensitive to uncouplers. Thus to the extent that uncouplers dissipate transmembrane proton-motive force, it is unlikely that such a force is used to drive ATP formation by direct protonations of Pi oxygens. When only Pi and ADP are added and formation of ATP from added ADP by adenylate kinase and subsequent ATP hydrolysis are adequately blocked, no Pi in equilibrium HOH exchange can be observed, demonstrating a requirement of energization by ATP binding and cleavage for such an exchange. This uncoupler-insensitive energization is suggested to represent a conformationally energized state that can be used reversibly to develop a transmembrane protonmotive force accompanying ADP and Pi release. Rates of various exchanges as estimated by improved procedures are compatible with all oxygen exchanges occurring by dynamic reversal of ATP hydrolysis at the catalytic site.

Adenosine Diphosphate↗
PubMedDate not supplied

[Mechanism of metabolic and ionic germination of "Bacillus licheniformis" spores treated with hydrogen peroxide (author's transl)].

Spores of Bacillus licheniformis 109-2A0 lost their refractility and absorbancy at 640 nm in the presence of metabolizable molecules (L-alanine). The same occurred with spores treated with 4.4 mol/1 hydrogen peroxide, pH 2.0, at 65 degrees C, even after 5 min of treatment. In addition, these transformations could be promoted after 2 min of treatment by inorganic ions (KI). This possibility occurs following a kinetics of activation. Thermodynamic parameters showed this activation to be combined with a molecular re-organization. Loss of refractility or absorbancy, induced by L-ala or KI, was inhibited by inhibitors of membrane functions or of L-alanine dehydrogenase, enzyme of which a noticeable activity was demonstrated in treated spores. Only 10% of spore calcium leaked during the treatment. Therefore loss of refractility or absorbancy caused by molecules metabolizable or not seemed to correspond to a physiological germination. The first even of the metabolic, as well as or the ionic germination could well be a modification of the spore membrane proton-motive force.

Alanine↗