Synopsis: Balancing forces in a petri dish

A simple model explores some of the factors that constrain the shape of rodlike bacteria as they grow.
Synopsis figure
Illustration: H. Jiang et al., Phys. Rev. Lett. (2010)

In times of plenty, bacteria follow a cycle of feeding, growing, and dividing. Holding the shape of bacteria in place as they grow is a layer of peptidoglycan—glycan strands cross-linked by peptides—that envelopes the cell wall. (The disruption of peptidoglycan production is the main effect of penicillin in fighting bacterial infections.)

An interesting feature of many rod-shaped bacteria is that new peptidoglycan, which is produced at the interior of the cell, mainly travels to the sidewalls, so the bacteria grow along their length and not at their ends. Writing in Physical Review Letters, Hongyuan Jiang and Sean Sun at The Johns Hopkins University, US, consider how the balance between chemical and elastic energy could explain the morphology of rod-shaped bacteria.

Jiang and Sun model the bacteria wall as an elastic balloon that is stretched using the chemical energy stored in a “patch” of newly arrived peptidoglycan. They show that a balance of these forces limits the radius of a rodlike bacteria’s poles (ends) but allows the cell’s length to grow linearly in time.

Though Jiang and Sun’s model neglects more complex features of the cell wall’s structure, their simple result may serve as a useful guideline for predicting the dynamics of cell growth. – Jessica Thomas


More Announcements »

Subject Areas

Biological PhysicsInterdisciplinary Physics

Previous Synopsis

Nuclear Physics

The limits of a closed shell

Read More »

Next Synopsis

Biological Physics

Electrons in hot water

Read More »

Related Articles

Focus: How to Compare Books or Genomes
Complex Systems

Focus: How to Compare Books or Genomes

A mathematical technique for comparing large symbol sets suggests that less frequently used words are mainly responsible for the evolution of the English language over the past two centuries. Read More »

Synopsis: Playing Games with Schrödinger
Interdisciplinary Physics

Synopsis: Playing Games with Schrödinger

Models that treat economic and biological behavior in terms of game-play resemble quantum mechanics. Read More »

Synopsis: Cells Go with the Crowd
Biological Physics

Synopsis: Cells Go with the Crowd

A simple model suggests a way in which clusters of cells could follow concentration gradients in cases where individual cells cannot. Read More »

More Articles