Differential permeability for lipophilic compounds in uncoupler-resistant cells of Escherichia coli

1992 ◽  
Vol 1099 (1) ◽  
pp. 45-50 ◽  
Author(s):  
Edward G. Sedgwick ◽  
Philip D. Bragg
Keyword(s):  
Escherichia Coli ◽  
Lipophilic Compounds ◽  
Differential Permeability ◽  
Resistant Cells

Proflavine binding and release by sensitive and resistant Bacillus subtilis

1970 ◽  
Vol 16 (10) ◽  
pp. 973-981
Author(s):  
Gy. Barabas ◽  
B. M. Mehta ◽  
D. J. Kushner
Keyword(s):  
Escherichia Coli ◽  
Bacillus Subtilis ◽  
Organic Acids ◽  
Resistant Strain ◽  
Binding Capacity ◽  
Sensitive Strain ◽  
Growth Media ◽  
Sodium Salts ◽  
Salts Of Organic Acids ◽  
Resistant Cells

Proflavine binding of a sensitive strain of Bacillus subtilis and of a resistant strain derived from it was compared. Proflavine was bound very rapidly and more was bound at 0 °C than at 37 °C. Boiling increased the proflavine-binding capacity at 37 °C of sensitive but not of resistant cells. The binding capacity of sensitive and resistant cells suspended in buffer was the same; this was also true in various growth media. If cells were able to grow in the presence of proflavine their proflavine content decreased.Bound proflavine was released when cells were treated with growth media or with the salts of growth media. Sodium salts of organic acids also caused a release. This effect seemed due to their Na+ content, and was somewhat higher for resistant than for sensitive cells. The mechanism of proflavine resistance in B. subtilis is probably different from that of Escherichia coli, which is thought to depend on an energy-driven release of bound proflavine.

The adsorption of bacteriophages by sensitive and resistant cells of Escherichia coli strain B

1955 ◽  
Vol 231 (1185) ◽  
pp. 291-291
Keyword(s):  
Escherichia Coli ◽  
Adsorption Isotherms ◽  
Coli Strain ◽  
Susceptible Host ◽  
Bacterial Virus ◽  
Phage Adsorption ◽  
Mutant Strains ◽  
Resistant Strains ◽  
Resistant Cells

The adsorption isotherms of T2 and a tryptophan-requiring strain of T4 have been measured on Escherichia coli B and on mutant strains resistant to these bacteriophages. The susceptible host adsorbs the phages and each cell becomes saturated with approximately 300 particles of phage. L-Tryptophan is necessary for the adsorption of the T4 strain. The isotherms are of the general Langmuir type, showing that phage adsorption is reversible, and it is concluded that the irreversible step of adsorption is suppressed in this system because of the occurrence of lysis from without. Resistant strains adsorb no bacteriophage at all, which shows that resistance is due to external exclusion of the bacterial virus. This type of resistance is compared with other types in which the agent has access to the cell and in which internal exclusion operates.

scholarly journals Stages of Polymyxin B Interaction with theEscherichia coli Cell Envelope

2000 ◽  
Vol 44 (11) ◽  
pp. 2969-2978 ◽  
Author(s):  
Rimantas Daugelavičius ◽  
Elena Bakiene˙ ◽  
Dennis H. Bamford
Keyword(s):  
Escherichia Coli ◽  
Pore Formation ◽  
Cytoplasmic Membrane ◽  
Cell Envelope ◽  
Polymyxin B ◽  
Bactericidal Effect ◽  
Bactericidal Action ◽  
Lipophilic Compounds ◽  
Permeability Characteristics ◽  
New Findings

ABSTRACT The effects of polymyxin B (PMB) on the Escherichia coli outer (OM) and cytoplasmic membrane (CM) permeabilities were studied by monitoring the fluxes of tetraphenylphosphonium, phenyldicarbaundecaborane, and K+ and H+ions. At concentrations between 2 and 20 μg/ml, PMB increased the OM permeability to lipophilic compounds and induced a leakage of K+ from the cytosol and an accumulation of lipophilic anions in the cellular membranes but did not cause the depolarization of the CM. At higher concentrations, PMB depolarized the CM, forming ion-permeable pores in the cell envelope. The permeability characteristics of PMB-induced pores mimic those of bacteriophage- and/or bacteriocin-induced channels. However, the bactericidal effect of PMB took place at concentrations below 20 μg/ml, indicating that this effect is not caused by pore formation. Under conditions of increased ionic strength, PMB made the OM permeable to lipophilic compounds and decreased the K+gradient but was not able to depolarize the cells. The OM-permeabilizing effect of PMB can be diminished by increasing the concentration of Mg2+. The major new findings of this work are as follows: (i) the OM-permeabilizing action of PMB was dissected from its depolarizing effect on the CM, (ii) the PMB-induced ion-permeable pores in bacterial envelope were registered, and (iii) the pore formation and depolarization of the CM are not obligatory for the bactericidal action of PMB and dissipation of the K+gradient on the CM.

scholarly journals STUDIES ON THE MECHANISM OF TUMOR INHIBITION BY L-ASPARAGINASE

1968 ◽  
Vol 127 (6) ◽  
pp. 1055-1072 ◽  
Author(s):  
J. D. Broome
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Tumor Inhibition ◽  
Normal Tissues ◽  
Synthetic Capacity ◽  
Resistant Cells

L-asparaginases of agouti serum and Escherichia coli cause a profound lowering in the level of free asparagine in the blood of treated mice and also in the tissues. During treatment, normal tissues and resistant 6C3HED lymphomas survive unharmed with intracellular asparagine levels which are critically low for sensitive lymphomas. An explanation for this contrast between the two types of lymphoma is provided by the finding that resistant cells have not only a higher asparagine synthetic capacity than sensitive cells but appear able to utilize endogenous asparagine preferentially for protein synthesis. Cell-free extracts of resistant cells contain an asparaginase synthetase, but this is not found in preparations from sensitive cells.

scholarly journals Compensation of the Metabolic Costs of Antibiotic Resistance by Physiological Adaptation in Escherichia coli

2013 ◽  
Vol 57 (8) ◽  
pp. 3752-3762 ◽  
Author(s):  
Nadine Händel ◽  
J. Merijn Schuurmans ◽  
Stanley Brul ◽  
Benno H. ter Kuile
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Expression Profiles ◽  
Cellular Stress Response ◽  
Physiological Adaptation ◽  
Initial Increase ◽  
Wild Type ◽  
Content Type ◽  
Metabolic Costs ◽  
Resistant Cells

ABSTRACTAntibiotic resistance is often associated with metabolic costs. To investigate the metabolic consequences of antibiotic resistance, the genomic and transcriptomic profiles of an amoxicillin-resistantEscherichia colistrain and the wild type it was derived from were compared. A total of 125 amino acid substitutions and 7 mutations that were located <1,000 bp upstream of differentially expressed genes were found in resistant cells. However, broad induction and suppression of genes were observed when comparing the expression profiles of resistant and wild-type cells. Expression of genes involved in cell wall maintenance, DNA metabolic processes, cellular stress response, and respiration was most affected in resistant cells regardless of the absence or presence of amoxicillin. The SOS response was downregulated in resistant cells. The physiological effect of the acquisition of amoxicillin resistance in cells grown in chemostat cultures consisted of an initial increase in glucose consumption that was followed by an adaptation process. Furthermore, no difference in maintenance energy was observed between resistant and sensitive cells. In accordance with the transcriptomic profile, exposure of resistant cells to amoxicillin resulted in reduced salt and pH tolerance. Taken together, the results demonstrate that the acquisition of antibiotic resistance inE. coliis accompanied by specifically reorganized metabolic networks in order to circumvent metabolic costs. The overall effect of the acquisition of resistance consists not so much of an extra energy requirement, but more a reduced ecological range.

scholarly journals In Vivo 31P Nuclear Magnetic Resonance Investigation of Tellurite Toxicity in Escherichia coli

2004 ◽  
Vol 70 (12) ◽  
pp. 7342-7347 ◽  
Author(s):  
Elke M. Lohmeier-Vogel ◽  
Shiela Ung ◽  
Raymond J. Turner
Keyword(s):  
Escherichia Coli ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ph Gradient ◽  
Resistance Determinants ◽  
Intracellular Atp ◽  
Atp Levels ◽  
Glycolytic Intermediates ◽  
Nuclear Magnetic ◽  
Resistant Cells

ABSTRACT Here we compare the physiological state of Escherichia coli exposed to tellurite or selenite by using the noninvasive technique of phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. We studied glucose-fed Escherichia coli HB101 cells containing either a normal pUC8 plasmid with no tellurite resistance determinants present or the pTWT100 plasmid which contains the resistance determinants tehAB. No differences could be observed in intracellular ATP levels, the presence or absence of a transmembrane pH gradient, or the levels of phosphorylated glycolytic intermediates when resistant cells were studied by 31P NMR in the presence or absence of tellurite. In the sensitive strain, we observed that the transmembrane pH gradient was dissipated and intracellular ATP levels were rapidly depleted upon exposure to tellurite. Only the level of phosphorylated glycolytic intermediates remained the same as observed with resistant cells. Upon exposure to selenite, no differences could be observed by 31P NMR between resistant and sensitive strains, suggesting that the routes for selenite and tellurite reduction within the cells differ significantly, since only tellurite is able to collapse the transmembrane pH gradient and lower ATP levels in sensitive cells. The presence of the resistance determinant tehAB, by an as yet unidentified detoxification event, protects the cells from uncoupling by tellurite.

scholarly journals Resistance of Escherichia coli to tetracyclines. Changes in permeability to tetracyclines in Escherichia coli bearing transferable resistance factors

1967 ◽  
Vol 105 (1) ◽  
pp. 371-378 ◽  
Author(s):  
T J Franklin
Keyword(s):  
Escherichia Coli ◽  
Tetracycline Resistance ◽  
Free Medium ◽  
Intact Cells ◽  
Resistance Factors ◽  
E Coli ◽  
Low Concentrations ◽  
R Factors ◽  
Drug Free ◽  
Resistant Cells

1. When strains of Escherichia coli, bearing transferable factors for resistance to the tetracyclines (R-factors), and previously cultured in the absence of the tetracyclines, are grown for 15–30min. in a low, subinhibitory, concentration (10μg./ml.) of oxytetracycline or tetracycline, there is a rapid and striking increase in resistance to oxytetracycline or tetracycline, this being associated with a marked fall in the absorption of the drug by the cells. 2. Very short preincubation (1min.) with oxytetracycline, followed by growth for 15–30min. in drug-free medium, produces a marked fall in the absorption of the drug by the resistant cells. Preincubation for 30min. with very low concentrations (0·05μg./ml.) of oxytetracycline produces a similar effect. 3. β-Apo-oxytetracycline, which has very little antibacterial activity, also induces a decreased absorption of oxytetracycline. 4. The ability to exclude oxytetracycline is retained by preincubated resistant cells after growth for 2hr. in drug-free medium. However, after growth for 16hr. in drug-free medium, the cells absorb oxytetracycline freely. 5. Chloramphenicol and proflavine inhibit the adaptive decrease in tetracycline absorption. 5-Fluorouracil has only a slight effect. 6. Spheroplasts prepared from resistant cells show an impaired response to preincubation with tetracycline, compared with intact cells. 7. The relevance of these results to the probable mechanism of tetracycline resistance in R-factor-bearing E. coli is discussed.

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