Optimal Cell Length for Exploration and Exploitation in Chemotactic Planktonic Bacteria

Area of Science:

• Microbiology
• Biophysics
• Mathematical Biology

Background:

• Motile bacterioplankton often exhibit elongated morphologies, commonly linked to enhanced chemotaxis.
• The optimal cell length for efficient chemotaxis remains unclear, despite its ecological significance.

Purpose of the Study:

• To investigate the existence of an optimal cell length for chemotaxis.
• To understand how physical constraints and the exploration-exploitation trade-off influence chemotactic efficiency.

Main Methods:

• Utilized cephalexin-treated Escherichia coli in microfluidic devices with stable chemical gradients.
• Employed an Individual-Based-Model (IBM) for sensitivity analysis.
• Simulated chemotactic performance in a phycosphere model.

Main Results:

• Intermediate-length cells showed the tightest aggregation to chemoattractants in experiments.
• IBM analysis revealed intermediate lengths are optimal for transient chemotaxis, while longer cells are superior at steady states.
• Short cells exhibited poor chemotaxis due to directionality loss; long cells were hindered by brief, slow runs.

Conclusions:

• Cell length significantly impacts chemotactic efficiency, with optimal length being context-dependent.
• Environmental stability, transient vs. steady states, and microenvironment characteristics (e.g., phycosphere) influence optimal cell size selection.