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Subcellular Min oscillations as a single-cell reporter of the action of polycations, protamine, and gentamicin on Escherichia coli.

Downing BP, Rutenberg AD, Touhami A, Jericho M - PLoS ONE (2009)

Bottom Line: We found rapid and substantial increases in the average MinD oscillation periods in the presence of any of these polyvalent cations.We also found striking interdependence in the action of the small cations with protamine or gentamicin, distorted oscillations under the action of intermediate levels of gentamicin and Ca(++), and reversible freezing of the Min oscillation at high cationic concentrations.Intracellular Min oscillations provide a fast single-cell reporter of bacterial response to extracellular polycations, which can be explained by the penetration of polycations into cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.

ABSTRACT

Background: In Escherichia coli, MinD-GFP fusion proteins show rapid pole to pole oscillations. The objective was to investigate the effects of extracellular cations on the subcellular oscillation of cytoplasmic MinD within Escherichia coli.

Methodology/principal findings: We exposed bacteria to the extracellular cations Ca(++), Mg(++), the cationic antimicrobial peptide (CAP) protamine, and the cationic aminoglycoside gentamicin. We found rapid and substantial increases in the average MinD oscillation periods in the presence of any of these polyvalent cations. For Ca(++) and Mg(++) the increases in period were transient, even with a constant extracellular concentration, while increases in period for protamine or gentamicin were apparently irreversible. We also found striking interdependence in the action of the small cations with protamine or gentamicin, distorted oscillations under the action of intermediate levels of gentamicin and Ca(++), and reversible freezing of the Min oscillation at high cationic concentrations.

Conclusions/significance: Intracellular Min oscillations provide a fast single-cell reporter of bacterial response to extracellular polycations, which can be explained by the penetration of polycations into cells.

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Related in: MedlinePlus

Variation of MinD oscillation period with gentamicin.(A) In 10 mM HEPES buffer at pH of 7.0, the period increases with gentamicin concentration (open diamonds). As shown in the inset, for three bacteria labeled B1, B2 and B3, for gentamicin concentrations of 70 µM or higher the wave form of polar intensity oscillations often became more like square-waves, where the intensity at the poles remained stationary for longer time periods. In the presence of 10 mM HEPES buffer and 20 mM Ca++ the oscillation period increase (filled circles) is that expected for 20 mM Ca++ alone and periods were independent of the gentamicin concentration within our measurement error. (B) Oscillation periods as function of gentamicin concentration (no added Ca++) for nine bacteria at a pH of 7.0. The period increases rapidly at low concentrations for all bacteria. Changes in the period on further increase in the gentamicin concentration varied widely in both sign and magnitude. The general trend was for the period to increase with increasing concentration, but some bacteria exhibited occasional decreases (dotted lines). Lines are an aid to the eye for each bacterium.
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pone-0007285-g008: Variation of MinD oscillation period with gentamicin.(A) In 10 mM HEPES buffer at pH of 7.0, the period increases with gentamicin concentration (open diamonds). As shown in the inset, for three bacteria labeled B1, B2 and B3, for gentamicin concentrations of 70 µM or higher the wave form of polar intensity oscillations often became more like square-waves, where the intensity at the poles remained stationary for longer time periods. In the presence of 10 mM HEPES buffer and 20 mM Ca++ the oscillation period increase (filled circles) is that expected for 20 mM Ca++ alone and periods were independent of the gentamicin concentration within our measurement error. (B) Oscillation periods as function of gentamicin concentration (no added Ca++) for nine bacteria at a pH of 7.0. The period increases rapidly at low concentrations for all bacteria. Changes in the period on further increase in the gentamicin concentration varied widely in both sign and magnitude. The general trend was for the period to increase with increasing concentration, but some bacteria exhibited occasional decreases (dotted lines). Lines are an aid to the eye for each bacterium.

Mentions: The aminoglycoside antibiotic gentamicin also produced considerable period lengthening. Addition of gentamicin at about 5 µg/ml (10.7 µM) immediately reduced the mobility of bacteria in the flow cell and increased their average oscillation period. Period results for gentamicin in 10 mM HEPES buffer at pH = 7.0 are shown in Fig. 8A (open diamonds). The periods, averaged over groups of bacteria, tended to increase rapidly initially with low gentamicin concentration and then rose more slowly as the concentration was further increased to 71 µM. At this concentration the bacteria started to exhibit more rounded shapes but these shape changes were not as pronounced as for the Ca++ effects at 100 mM shown in Fig. 5A. We also observed a striking non-sinusoidal Min oscillation at 71 µM of gentamicin, as shown in the inset in Fig. 8A, for three individual bacteria. The oscillation traces appear more like square waves. Similar non-sinusoidal oscillations were occasionally observed for high Ca++ levels. Unlike for Ca++ and Mg++, the period changes for gentamicin were not reversible. Return to control solution did not shorten periods even after four hours. Fig. 8B shows the variation of oscillation periods with gentamicin concentration for 9 individual bacteria that remained localized during all ion exchanges. Although all bacteria show an initial period increase at low concentration, subsequent changes were bacterium dependent with the occasional bacterium at high gentamicin concentration even having a faster period (open squares and open diamonds).


Subcellular Min oscillations as a single-cell reporter of the action of polycations, protamine, and gentamicin on Escherichia coli.

Downing BP, Rutenberg AD, Touhami A, Jericho M - PLoS ONE (2009)

Variation of MinD oscillation period with gentamicin.(A) In 10 mM HEPES buffer at pH of 7.0, the period increases with gentamicin concentration (open diamonds). As shown in the inset, for three bacteria labeled B1, B2 and B3, for gentamicin concentrations of 70 µM or higher the wave form of polar intensity oscillations often became more like square-waves, where the intensity at the poles remained stationary for longer time periods. In the presence of 10 mM HEPES buffer and 20 mM Ca++ the oscillation period increase (filled circles) is that expected for 20 mM Ca++ alone and periods were independent of the gentamicin concentration within our measurement error. (B) Oscillation periods as function of gentamicin concentration (no added Ca++) for nine bacteria at a pH of 7.0. The period increases rapidly at low concentrations for all bacteria. Changes in the period on further increase in the gentamicin concentration varied widely in both sign and magnitude. The general trend was for the period to increase with increasing concentration, but some bacteria exhibited occasional decreases (dotted lines). Lines are an aid to the eye for each bacterium.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2749335&req=5

pone-0007285-g008: Variation of MinD oscillation period with gentamicin.(A) In 10 mM HEPES buffer at pH of 7.0, the period increases with gentamicin concentration (open diamonds). As shown in the inset, for three bacteria labeled B1, B2 and B3, for gentamicin concentrations of 70 µM or higher the wave form of polar intensity oscillations often became more like square-waves, where the intensity at the poles remained stationary for longer time periods. In the presence of 10 mM HEPES buffer and 20 mM Ca++ the oscillation period increase (filled circles) is that expected for 20 mM Ca++ alone and periods were independent of the gentamicin concentration within our measurement error. (B) Oscillation periods as function of gentamicin concentration (no added Ca++) for nine bacteria at a pH of 7.0. The period increases rapidly at low concentrations for all bacteria. Changes in the period on further increase in the gentamicin concentration varied widely in both sign and magnitude. The general trend was for the period to increase with increasing concentration, but some bacteria exhibited occasional decreases (dotted lines). Lines are an aid to the eye for each bacterium.
Mentions: The aminoglycoside antibiotic gentamicin also produced considerable period lengthening. Addition of gentamicin at about 5 µg/ml (10.7 µM) immediately reduced the mobility of bacteria in the flow cell and increased their average oscillation period. Period results for gentamicin in 10 mM HEPES buffer at pH = 7.0 are shown in Fig. 8A (open diamonds). The periods, averaged over groups of bacteria, tended to increase rapidly initially with low gentamicin concentration and then rose more slowly as the concentration was further increased to 71 µM. At this concentration the bacteria started to exhibit more rounded shapes but these shape changes were not as pronounced as for the Ca++ effects at 100 mM shown in Fig. 5A. We also observed a striking non-sinusoidal Min oscillation at 71 µM of gentamicin, as shown in the inset in Fig. 8A, for three individual bacteria. The oscillation traces appear more like square waves. Similar non-sinusoidal oscillations were occasionally observed for high Ca++ levels. Unlike for Ca++ and Mg++, the period changes for gentamicin were not reversible. Return to control solution did not shorten periods even after four hours. Fig. 8B shows the variation of oscillation periods with gentamicin concentration for 9 individual bacteria that remained localized during all ion exchanges. Although all bacteria show an initial period increase at low concentration, subsequent changes were bacterium dependent with the occasional bacterium at high gentamicin concentration even having a faster period (open squares and open diamonds).

Bottom Line: We found rapid and substantial increases in the average MinD oscillation periods in the presence of any of these polyvalent cations.We also found striking interdependence in the action of the small cations with protamine or gentamicin, distorted oscillations under the action of intermediate levels of gentamicin and Ca(++), and reversible freezing of the Min oscillation at high cationic concentrations.Intracellular Min oscillations provide a fast single-cell reporter of bacterial response to extracellular polycations, which can be explained by the penetration of polycations into cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.

ABSTRACT

Background: In Escherichia coli, MinD-GFP fusion proteins show rapid pole to pole oscillations. The objective was to investigate the effects of extracellular cations on the subcellular oscillation of cytoplasmic MinD within Escherichia coli.

Methodology/principal findings: We exposed bacteria to the extracellular cations Ca(++), Mg(++), the cationic antimicrobial peptide (CAP) protamine, and the cationic aminoglycoside gentamicin. We found rapid and substantial increases in the average MinD oscillation periods in the presence of any of these polyvalent cations. For Ca(++) and Mg(++) the increases in period were transient, even with a constant extracellular concentration, while increases in period for protamine or gentamicin were apparently irreversible. We also found striking interdependence in the action of the small cations with protamine or gentamicin, distorted oscillations under the action of intermediate levels of gentamicin and Ca(++), and reversible freezing of the Min oscillation at high cationic concentrations.

Conclusions/significance: Intracellular Min oscillations provide a fast single-cell reporter of bacterial response to extracellular polycations, which can be explained by the penetration of polycations into cells.

Show MeSH
Related in: MedlinePlus