Bending forces plastically deform growing bacterial cell walls.

Area of Science:

• Microbiology
• Biophysics
• Cell Biology

Background:

• Bacterial cell walls are crucial for maintaining cell shape and integrity against internal and external forces.
• The mechanisms by which bacteria adapt their cell walls to diverse physical environments remain largely unknown.

Purpose of the Study:

• To investigate how mechanical stresses regulate bacterial cell wall growth and shape maintenance.
• To elucidate the physical principles governing bacterial cell deformation and shape recovery.

Main Methods:

• Experimental application of precisely controllable hydrodynamic forces to growing bacterial cells (Escherichia coli and Bacillus subtilis).
• Development of theoretical models based on dislocation-mediated growth to explain observed cell deformation.
• Quantitative comparison of experimental results with theoretical predictions.

Main Results:

• Bacteria exhibit two distinct deformation modes: elastic rod-like behavior under transient forces and plastic deformation during active cell wall synthesis.
• Deformed bacterial cells demonstrate a remarkable ability to recover their original shape after force removal.
• A single dimensionless parameter, derived from physical properties, effectively describes cell responses across various conditions.

Conclusions:

• Mechanical stress is a key regulator of bacterial cell wall growth and shape.
• Dislocation-mediated growth theory accurately predicts bacterial cell deformation and shape recovery.
• These findings offer insights into the robust mechanisms bacteria employ to maintain shape in dynamic physical environments.