scholarly journals Cation Transport in Escherichia coli

1965 ◽  
Vol 49 (2) ◽  
pp. 221-234 ◽  
Author(s):  
Wolfgang Epstein ◽  
Stanley G. Schultz
Keyword(s):  
Escherichia Coli ◽  
Growth Medium ◽  
Cation Transport ◽  
Major Determinant ◽  
Sudden Increase ◽  
Rapid Loss ◽  
Rapid Changes ◽  
K Concentration

Measurement of cellular K and Na concentrations in growing Escherichia coli indicates that the osmololity of the medium is a major determinant of the cell K concentration. In contrast, the cell Na concentration is independent of the medium osmolality and is largely dependent on the Na concentration of the medium. Sudden changes in the osmolality of the medium lead to rapid changes in K content. Washing the cells with solutions of lower osmolality results in a very rapid loss of K, which is greater in more dilute and in cold solutions. A sudden increase in the osmolality of the growth medium produces a rapid uptake of K by a mechanism whose rate is a saturable function of the K concentration of the medium and which appears to involve an exchange of K for cellular H.

scholarly journals Cation Transport in Escherichia coli

1963 ◽  
Vol 47 (2) ◽  
pp. 329-346 ◽  
Author(s):  
Stanley G. Schultz ◽  
Wolfgang Epstein ◽  
A. K. Solomon
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Cation Transport ◽  
Fresh Medium ◽  
Half Time ◽  
K Uptake ◽  
Acid Media ◽  
E Coli ◽  
K Concentration ◽  
Kinetics Of

The resuspension of K-poor, Na-rich stationary phase E. coli in fresh medium at pH 7.0 results in a rapid uptake of K and extrusion of Na by the cells. In all experiments net K uptake exceeded net Na extrusion. An investigation of the uptake of glucose, PO4, and Mg and the secretion of H by these cells indicates that the excess K uptake is not balanced by the simultaneous uptake of anions but must be accompanied by the extrusion of cations from the cell. The kinetics of net K uptake are consistent with the existence of two parallel influx processes. The first is rapid, of brief duration, and accounts for approximately 60 per cent of the total net K uptake. This process is a function of the extracellular K concentration, is inhibited in acid media, and appears to be a 1 for 1 exchange of extracellular K for intracellular H. The second influx process has a half-time of approximately 12 minutes, and is not affected by acid media. This process is a function of the intracellular Na concentration, is dependent upon the presence of K in the medium, and may be ascribed to a 1 for 1 exchange of extracellular K for intracellular Na.

scholarly journals Cation Transport in Escherichia coli

1962 ◽  
Vol 46 (1) ◽  
pp. 159-166 ◽  
Author(s):  
Stanley G. Schultz ◽  
Norman L. Wilson ◽  
Wolfgang Epstein
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Growth Medium ◽  
Bacterial Culture ◽  
Cation Transport ◽  
Logarithmic Phase ◽  
E Coli

The intracellular Cl concentration in E. coli has been studied as a function of the Cl concentration in the growth medium and the age of the bacterial culture. The ratio of extracellular to intracellular Cl concentration is shown to be 3.0 in the logarithmic phase and 1.13 in the stationary phase, both ratios being independent of the extracellular Cl concentration. If it may be assumed that Cl is passively distributed in this organism, these results are consistent with a transmembrane P.D. of 29 mv, interior negative, during the logarithmic phase, and 3 mv, interior negative, in the stationary phase.

scholarly journals Characterization of the basolateral membrane conductance of Necturus urinary bladder.

1987 ◽  
Vol 89 (4) ◽  
pp. 541-562 ◽  
Author(s):  
J R Demarest ◽  
A L Finn
Keyword(s):  
Electrical Properties ◽  
Basolateral Membrane ◽  
Membrane Conductance ◽  
Transference Numbers ◽  
Sudden Increase ◽  
Membrane Selectivity ◽  
Rapid Changes ◽  
K Concentration ◽  
Passive Electrical Properties

Necturus urinary bladders stripped of serosal muscle and connective tissue were impaled through their basolateral membranes with microelectrodes in experiments that permitted rapid changes in the ion composition of the serosal solution. The transepithelial electrical properties exhibited a marked seasonal variation that could be attributed to variations in the conductance of the shunt pathway, apical membrane selectivity, and basolateral Na+ transport. In contrast, the passive electrical properties of the basolateral membrane remained constant throughout the year. The apparent transference numbers (Ti) of the basolateral membrane for K+ and Cl- were determined from the effect on the basolateral membrane equivalent electromotive force of a sudden increase in the serosal K+ concentration from 2.5 to 50 mM/liter or a decrease in the Cl- concentration from 101 to 10 mM/liter. TK and TCl were 0.71 +/- 0.05 and 0.04 +/- 0.01, respectively. The basolateral K+ conductance could be blocked by Ba2+ (0.5 mM), Cs+ (10 mM), or Rb+ (10 mM), but was unaffected by 3,4-diaminopyridine (100 microM), decamethonium (100 microM), or tetraethylammonium (10 mM). We conclude that a highly selective K+ conductance dominates the electrical properties of the basolateral membrane and that this conductance is different from those found in nerve and muscle membranes.

scholarly journals Cation Transport in Escherichia coli

1966 ◽  
Vol 49 (3) ◽  
pp. 469-481 ◽  
Author(s):  
Wolfgang Epstein ◽  
Stanley G. Schultz
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Cation Transport ◽  
Experimental Conditions ◽  
Tightly Coupled ◽  
K Concentration

K influx and net K flux have been measured in suspensions of chloramphenicol-arrested Escherichia coli. The rate of K exchange in the steady state was independent of the K concentration of the medium over a 200-fold range. Under a number of experimental conditions the rate of exchange may be considerably increased or decreased without changing the cellular K content. These results show that under these conditions changes in K influx are associated with equal changes in K efflux, and suggest that the latter process is, at least in part, both carrier-mediated and tightly coupled to the influx process.

scholarly journals Cation Transport in Escherichia coli

1962 ◽  
Vol 46 (2) ◽  
pp. 343-353 ◽  
Author(s):  
Stanley G. Schultz ◽  
Wolfgang Epstein ◽  
David A. Goldstein
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Cation Transport ◽  
E Coli ◽  
Dense Suspension ◽  
K Concentration ◽  
Kinetics Of

The present study is concerned with the measurement of the unidirectional K flux in E. coli. Methods are described by means of which a fairly dense suspension of cells may be maintained in a well defined steady-state with respect to the intracellular K concentration and the pH of the medium. The kinetics of K42 exchange under these conditions are consistent with the presence of a single intracellular K compartment with a unidirectional K flux of 1 pmol/(cm2 sec.). This rate is independent of the extracellular K concentration over the range studied. The simultaneous rate of H secretion averages 16 pmols/(cm2 sec.) indicating that in the steady-state the efflux of metabolically produced H is not linked mole for mole to K movement.

scholarly journals Effect of the Osmotic Pressure of the Growth Medium on fabB Mutants of Escherichia coli

1974 ◽  
Vol 117 (3) ◽  
pp. 971-977 ◽  
Author(s):  
J. H. F. F. Broekman ◽  
Johan F. Steenbakkers
Keyword(s):  
Escherichia Coli ◽  
Osmotic Pressure ◽  
Growth Medium

scholarly journals Scorpion Venom Antimicrobial Peptides Induce Siderophore Biosynthesis and Oxidative Stress Responses in Escherichia coli

mSphere ◽  
2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Mohamed M. Tawfik ◽  
Magnus Bertelsen ◽  
Mohamed A. Abdel-Rahman ◽  
Peter N. Strong ◽  
Keith Miller
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Peptides ◽  
Antimicrobial Agents ◽  
Venom Gland ◽  
Cation Transport ◽  
Content Type ◽  
Starting Point ◽  
Wide Range ◽  
Initial Starting ◽  
Increased Susceptibility

ABSTRACT The increasing development of microbial resistance to classical antimicrobial agents has led to the search for novel antimicrobials. Antimicrobial peptides (AMPs) derived from scorpion and snake venoms offer an attractive source for the development of novel therapeutics. Smp24 (24 amino acids [aa]) and Smp43 (43 aa) are broad-spectrum AMPs that have been identified from the venom gland of the Egyptian scorpion Scorpio maurus palmatus and subsequently characterized. Using a DNA microarray approach, we examined the transcriptomic responses of Escherichia coli to subinhibitory concentrations of Smp24 and Smp43 peptides following 5 h of incubation. Seventy-two genes were downregulated by Smp24, and 79 genes were downregulated by Smp43. Of these genes, 14 genes were downregulated in common and were associated with bacterial respiration. Fifty-two genes were specifically upregulated by Smp24. These genes were predominantly related to cation transport, particularly iron transport. Three diverse genes were independently upregulated by Smp43. Strains with knockouts of differentially regulated genes were screened to assess the effect on susceptibility to Smp peptides. Ten mutants in the knockout library had increased levels of resistance to Smp24. These genes were predominantly associated with cation transport and binding. Two mutants increased resistance to Smp43. There was no cross-resistance in mutants resistant to Smp24 or Smp43. Five mutants showed increased susceptibility to Smp24, and seven mutants showed increased susceptibility to Smp43. Of these mutants, formate dehydrogenase knockout (fdnG) resulted in increased susceptibility to both peptides. While the electrostatic association between pore-forming AMPs and bacterial membranes followed by integration of the peptide into the membrane is the initial starting point, it is clear that there are numerous subsequent additional intracellular mechanisms that contribute to their overall antimicrobial effect. IMPORTANCE The development of life-threatening resistance of pathogenic bacteria to the antibiotics typically in use in hospitals and the community today has led to an urgent need to discover novel antimicrobial agents with different mechanisms of action. As an ancient host defense mechanism of the innate immune system, antimicrobial peptides (AMPs) are attractive candidates to fill that role. Scorpion venoms have proven to be a rich source of AMPs. Smp24 and Smp43 are new AMPs that have been identified from the venom gland of the Egyptian scorpion Scorpio maurus palmatus, and these peptides can kill a wide range of bacterial pathogens. By better understanding how these AMPs affect bacterial cells, we can modify their structure to make better drugs in the future.

Influence of Electrolytes Added to Growth Medium on Electrophoretic Potential of Escherichia Coli.

1935 ◽  
Vol 32 (9) ◽  
pp. 1572-1573 ◽  
Author(s):  
G. W. Pearce ◽  
M. W. Lisse ◽  
R. P. Tittsler
Keyword(s):  
Escherichia Coli ◽  
Growth Medium
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