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Related Concept Videos

Membrane Fluidity01:23

Membrane Fluidity

152.0K
Cell membranes are composed of phospholipids, proteins, and carbohydrates loosely attached to one another through chemical interactions. Molecules are generally able to move about in the plane of the membrane, giving the membrane its flexible nature called fluidity. Two other features of the membrane contribute to membrane fluidity: the chemical structure of the phospholipids and the presence of cholesterol in the membrane.
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Total Internal Reflection Fluorescence Microscopy01:05

Total Internal Reflection Fluorescence Microscopy

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Total internal reflection fluorescence microscopy or TIRF is an advanced microscopic technique used to visualize fluorophores in samples close to a solid surface with a higher refractive index, such as a glass coverslip. TIRF only allows fluorophores in proximity to the solid surface to be excited. When light from a medium with a lower refractive index (such as air) hits the glass coverslip at a critical angle, the light undergoes total internal reflection stead of passing through the glass.
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Related Experiment Video

Updated: Jun 23, 2025

Single-Molecule Imaging of Lateral Mobility and Ion Channel Activity in Lipid Bilayers using Total Internal Reflection Fluorescence TIRF Microscopy
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Quantification of membrane fluidity in bacteria using TIR-FCS.

Aurélien Barbotin1, Cyrille Billaudeau1, Erdinc Sezgin2

  • 1Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France.

Biophysical Journal
|June 15, 2024
PubMed
Summary

Researchers developed a new assay to measure bacterial membrane fluidity using total internal reflection-fluorescence correlation spectroscopy (TIR-FCS). This method quantifies how temperature changes affect bacterial membrane fluidity and adaptation responses in live bacteria.

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Area of Science:

  • Microbiology
  • Biophysics
  • Cell Biology

Background:

  • Plasma membrane fluidity is crucial for bacterial cell function, impacting protein activity, respiration, transport, and antibiotic resistance.
  • Environmental stresses like temperature changes necessitate tight regulation of membrane fluidity for bacterial adaptation.
  • Existing methods for measuring membrane fluidity are often unsuitable for small, curved bacterial cells.

Purpose of the Study:

  • To develop and validate a novel assay for directly measuring membrane fluidity in live bacteria.
  • To quantify bacterial membrane fluidity dynamics in response to temperature variations and cold shock.
  • To investigate differences in membrane fluidity regulation between bacterial species.

Main Methods:

  • Development of a total internal reflection-fluorescence correlation spectroscopy (TIR-FCS) assay for live bacteria.
  • Utilizing simulations validated by experiments to correct for bacterial size, curvature, and geometry in diffusion measurements.
  • Quantifying the diffusivity of fluorescent membrane markers to determine membrane fluidity.

Main Results:

  • The developed TIR-FCS assay successfully measured bacterial membrane fluidity.
  • Steady-state membrane fluidity was lower at 20°C compared to 37°C and varied between Bacillus subtilis and Staphylococcus aureus at 37°C.
  • Cold shock caused a further decrease in membrane fluidity, with recovery observed within 30 minutes in both species.

Conclusions:

  • The novel TIR-FCS assay provides a minimally invasive tool for studying bacterial membrane fluidity.
  • This assay enables quantitative analysis of bacterial adaptation to environmental temperature changes.
  • The findings offer new perspectives for studying bacterial membrane responses to various external factors, including antibiotics and viral infections.