Ionophore Antibiotics

Bakker, Evert P.

doi:10.1007/978-3-642-46403-4_5

Cited by 19 publications

(13 citation statements)

References 188 publications

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“…Potassium ions are required for growth; orientation of growth in media of very low K+ content (0.1 mM) could not be studied because under these conditions the antibiotic becomes excessively inhibitory to growth. However, the failure of the powerful K+ ionophore valinomycin (1,24) to orient growth of the rhizoids (Fig. 3) suggests that enhanced K+ flux is not responsible for the effects of gramicidin D.…”

Section: Resultsmentioning

confidence: 99%

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Oriented growth of Blastocladiella emersonii in gradients of ionophores and inhibitors

Harold¹,

Harold²

1980

J Bacteriol

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To investigate whether ion currents help to localize growth and development of Blastocladiella emersonii, we grew the organisms in gradients of various ionophores and inhibitors. Gradients were generated by placing into the culture fine glass fibers coated with insoluble inhibitors; in some cases, inhibitors were adsorbed onto beads of ion-exchange resin. Organisms growing in many of these gradients exhibited a striking tendency for the thalli to grow toward the fiber. This proved to be misleading; the cells grew not toward the source of the ionophore but into the unoccupied zone of inhibition adjacent to the fiber. Fibers coated with gramicidin-D induced marked effects on the growth of the rhizoids, which were greatly enlarged and grew toward and onto the fiber. None of the other inhibitors produced such effects, except for beads coated with the proton conductors tetrachlorosalicylanilide and compound 1799. The results suggest that orientation of rhizoid growth results from enhancement of proton flux across the plasma membrane. Growth of the rhizoids was also strongly oriented by gradients of inorganic phosphate and an amino acid mixture; gradients of glucose, K+, Ca2+, and glutamate were ineffective. We propose that a major physiological function of the rhizoid is to transport nutrients to the thallus. Finally, we examined the effects of a series of benzimidazole antitubulins as well as the cytochalasins. These did not orient growth but grossly perturbed the pattern of cellular organization, producing small spherical cells with multiple stunted rhizoids. The findings are interpreted in terms of the interaction of an endogenous transcellular proton current with elements of the cytoskeleton in the determination of form.

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Section: Resultsmentioning

confidence: 99%

“…Gramicidin is a channel-forming ionophore that allows the passage of K+, Na+, and H+ (1,24). It is unlikely that Na+ movements are involved in the orientation of growth; sodium is apparently not required for growth of B. emersonii (28), and its omission did not reduce the effectiveness of gramicidin gradients (data not shown).…”

Section: Resultsmentioning

confidence: 99%

Oriented growth of Blastocladiella emersonii in gradients of ionophores and inhibitors

Harold¹,

Harold²

1980

J Bacteriol

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“…Table II shows that vanadate and nigericin, which, respectively, inhibit H+ extrusion and collapse membrane ApH values without inhibiting energy metabolism (3,11,18), block IAA enhancement of GS activity. These agents also block enhancement of enzyme activity by FC (data not shown).…”

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confidence: 99%

Auxin and Fusicoccin Enhancement of β-Glucan Synthase in Peas

Ray¹

1985

Plant Physiol.

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Fusicoccin (FC), like indoleacetic acid (IAA), causes Golgi-localized B-1,4-glucan synthase (GS) activity to increase when applied to pea third internode segments whose GS activity has declined after isolation from the plant. This suggests that GS activity is modulated by H' extrusion; in agreement, vanadate and nigericin inhibit the GS response. The GS response is not due to acidification of the cell wall. Treatment of tissue with heavy water, which in effect raises intracellular pH, mimics the MATERIALS AND METHODS Pea (Pisum sativum cv Alaska) seedlings were grown and third internode segments 8 mm long were cut as described (27), except that for all experiments other than that ofTable I, each internode was abraded (14) by stroking with an aqueous paste of No. 305 emery powder (Edmund Scientific, Barrington, NJ) which was then rinsed off by vigorous agitation in water, before cutting the segment. The segments were kept 2 to 3 h at 35C in moist air to deplete their GS activity (27).Lots of 30 segments, each in a small Stender dish, were pretreated usually for 30 to 60 min at 35°C in a medium containing 30 mm sucrose, 0.8 mm citric acid/Pipes (Tris salt) buffer pH 6.5 (unless specified otherwise in figure or table legends), containing usually 1 mM KCI, plus indicated additions. This pretreatment medium was removed and 2.0 ml of a similar incubation medium, with or without IAA or FC as indicated, the initial pH of which had been carefully measured to 0.01 pH unit with a semimicro glass electrode, were added, and the dishes were kept normally at 35C for 60 or 90 min (the incubation period). The incubation medium was removed and its pH was remeasured, while the segments were rinsed with ice water and held on ice until they were homogenized to prepare membranes for enzyme assay. H+ extrusion was estimated from the measured drop in pH (ApH) of the medium during incubation, using the postincubation titration curve

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“…The values of Ail and PMF given were corrected for nonspecific binding of tetraphenylphosphonium to the membrane, using cells in the presence of the uncoupler carbonyl cyanide-p-(trifluoromethoxy)-phenylhydrazone (50 ,uM). These values are imprecise due to the uncertainty involved in quantitative corrections for binding to energized cells (2,5,38,63,67).…”

Section: Chemicals [14c]tetraphenylphosphonium Bromide Wasmentioning

confidence: 99%

“…One of the ways to distinguish between response to a potential change and signaling by way of fluctuations in A*, is to clamp the potential at a constant value and study the effect of this clamping on the response of the bacteria to a chemical stimulant. A clamped potential can be achieved with valinomycin, a K+-specific ionophore (5,53), in the presence of external K+. Such an approach has been applied successfully to nonperitrichous bacteria, in which chemotaxis of Spirochaeta aurantia (20,21) and phototaxis of Rhodospirillum rubrum (24) were inhibited by this treatment.…”

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confidence: 99%

Voltage clamp effects on bacterial chemotaxis

Margolin¹,

Eisenbach²

1984

J Bacteriol

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To examine whether or not sensory signaling in bacteria is by way of fluctuations in membrane potential, we studied the effect of clamping the potential on bacterial chemotaxis. The potential was clamped by valinomycin, a K+-specific ionophore, in the presence of K+. Despite the clamped potential, sensory signaling did occur: both Escherichia coli and Bacillus subtilis cells were still excitable and adaptable under these conditions. It is concluded that signaling in the excitation and adaptation steps of chemotaxis is not by way of fluctuations in the membrane potential.

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Ionophore Antibiotics

Cited by 19 publications

References 188 publications

Oriented growth of Blastocladiella emersonii in gradients of ionophores and inhibitors

Oriented growth of Blastocladiella emersonii in gradients of ionophores and inhibitors

Auxin and Fusicoccin Enhancement of β-Glucan Synthase in Peas

Voltage clamp effects on bacterial chemotaxis

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