Bacterial Motility Reveals Unknown Molecular Organization

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Lyotropic liquid crystals (LCs) offer unique environments for studying biological microorganisms.
• Flagellated bacteria, like Escherichia coli, show altered motility in disodium cromoglycate (DSCG) solutions.

Purpose of the Study:

• To investigate the behavior of Escherichia coli in DSCG-water solutions of varying concentrations.
• To understand the physical mechanisms behind bacterial motility changes in LCs.

Main Methods:

• Observation of bacterial movements in DSCG solutions.
• Measurement of DSCG solution viscosity as a function of concentration.
• Experimental identification of a bacterial sticking phenomenon.

Main Results:

• A pretransition zone was identified below the isotropic-LC transition (~10 wt % DSCG) starting at 6±1 wt %.
• Bacterial sticking to surfaces and each other was observed in this pretransition zone.
• Bacterial propulsive force and DSCG aggregate length increased significantly in the pretransition zone.

Conclusions:

• Osmotic pressure-induced depletion forces may cause bacterial sticking.
• Bacterial motility in DSCG solutions is strongly influenced by concentration-dependent physical properties.
• Findings offer insights into bacterial behavior in complex fluids and potential applications in diagnostics and wound healing.