Mechanisms for maintaining cell shape in rod-shaped Gram-negative bacteria

Area of Science:

• Microbiology
• Biophysics
• Cell Biology

Background:

• Bacterial cell shape is crucial for functions like motility and adhesion.
• The peptidoglycan cell wall determines bacterial shape, but its assembly mechanism remains unclear.
• Maintaining micron-scale shape during growth is a key challenge in bacterial cell biology.

Purpose of the Study:

• To investigate the biophysical mechanisms underlying robust cell shape maintenance in rod-shaped bacteria.
• To explore the roles of peptidoglycan synthesis spatial regulation, glycan-strand properties, and mechanical forces in shape determination.
• To quantify the robustness of cell shape in Escherichia coli under various conditions.

Main Methods:

• Developed a biophysical model for rod-shaped cell growth dynamics.
• Quantified cell shape robustness in different genetic backgrounds and with division-inhibiting antibiotics.
• Analyzed the impact of peptidoglycan insertion patterns, cell-wall density, and stress on shape.

Main Results:

• Rod-shape maintenance requires peptidoglycan synthesis to be insensitive to cell-wall density and stress fluctuations.
• A simple helical insertion pattern is sufficient for significant cell elongation without shape loss.
• Newly inserted peptidoglycan strand length and pre-stretching regulate bacterial cell width.

Conclusions:

• Bacterial cell shape is robustly maintained through simple physical rules governing cell-wall growth.
• Spatial regulation and mechanical properties of peptidoglycan synthesis are key to bacterial morphogenesis.
• Understanding these principles offers insights into bacterial growth and potential therapeutic targets.