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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

Effect of excitation illumination on MinD periods.MinD oscillation period in 10 mM HEPES buffer at pH 7.0 as function of cumulative exposure time to excitation illumination. The cumulative exposure time represents the sum of the exposure times used for all images taken of a group of bacteria. The time interval between exposures in a sequence of images was 4.5 seconds (to determine the period) and the interval between repeated sequences was 10 minutes (to recover the steady-state response to previous illumination). Repeated exposure of a group of bacteria to the fluorescence excitation light lengthened their average GFP-MinD oscillation period.
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pone-0007285-g003: Effect of excitation illumination on MinD periods.MinD oscillation period in 10 mM HEPES buffer at pH 7.0 as function of cumulative exposure time to excitation illumination. The cumulative exposure time represents the sum of the exposure times used for all images taken of a group of bacteria. The time interval between exposures in a sequence of images was 4.5 seconds (to determine the period) and the interval between repeated sequences was 10 minutes (to recover the steady-state response to previous illumination). Repeated exposure of a group of bacteria to the fluorescence excitation light lengthened their average GFP-MinD oscillation period.

Mentions: Small increases in the MinD oscillation period were observed in 10 mM HEPES buffer in the absence of any cations, proportional to the cumulative amount of 450- to 490-nm excitation illumination. When the illumination and viewing region was shifted to unexposed bacteria, shorter periods were again recorded. In Fig. 3 we show the oscillation periods as function of cumulative exposure time for a group of bacteria. To determine the oscillation period the exposure would typically be 6000 ms: 30 exposures with an exposure time of 200 ms each. For cumulative exposures of 25000 ms the period increase is about 10 s. This photon-induced period lengthening was avoided for experiments involving multiple cation concentrations and/or multiple time-points by imaging different groups of bacteria for each period determination. To measure multiple periods in a single bacterium we used short exposures of 50 ms to 100 ms together with the minimum number of images needed for period determination. For data taken before this effect became apparent (see, e.g., Fig. 4A), we corrected for the phototoxic period slowing using the best-fit line in Fig. 3. When compared, these corrected periods agreed with periods taken with changing fields of view.


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)

Effect of excitation illumination on MinD periods.MinD oscillation period in 10 mM HEPES buffer at pH 7.0 as function of cumulative exposure time to excitation illumination. The cumulative exposure time represents the sum of the exposure times used for all images taken of a group of bacteria. The time interval between exposures in a sequence of images was 4.5 seconds (to determine the period) and the interval between repeated sequences was 10 minutes (to recover the steady-state response to previous illumination). Repeated exposure of a group of bacteria to the fluorescence excitation light lengthened their average GFP-MinD oscillation period.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0007285-g003: Effect of excitation illumination on MinD periods.MinD oscillation period in 10 mM HEPES buffer at pH 7.0 as function of cumulative exposure time to excitation illumination. The cumulative exposure time represents the sum of the exposure times used for all images taken of a group of bacteria. The time interval between exposures in a sequence of images was 4.5 seconds (to determine the period) and the interval between repeated sequences was 10 minutes (to recover the steady-state response to previous illumination). Repeated exposure of a group of bacteria to the fluorescence excitation light lengthened their average GFP-MinD oscillation period.
Mentions: Small increases in the MinD oscillation period were observed in 10 mM HEPES buffer in the absence of any cations, proportional to the cumulative amount of 450- to 490-nm excitation illumination. When the illumination and viewing region was shifted to unexposed bacteria, shorter periods were again recorded. In Fig. 3 we show the oscillation periods as function of cumulative exposure time for a group of bacteria. To determine the oscillation period the exposure would typically be 6000 ms: 30 exposures with an exposure time of 200 ms each. For cumulative exposures of 25000 ms the period increase is about 10 s. This photon-induced period lengthening was avoided for experiments involving multiple cation concentrations and/or multiple time-points by imaging different groups of bacteria for each period determination. To measure multiple periods in a single bacterium we used short exposures of 50 ms to 100 ms together with the minimum number of images needed for period determination. For data taken before this effect became apparent (see, e.g., Fig. 4A), we corrected for the phototoxic period slowing using the best-fit line in Fig. 3. When compared, these corrected periods agreed with periods taken with changing fields of view.

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