A constant size extension drives bacterial cell size homeostasis

Area of Science:

• Microbiology
• Cell Biology
• Systems Biology

Background:

• Cell size control is crucial for cell cycle progression.
• The prevailing model suggested bacteria divide at a critical size threshold.

Purpose of the Study:

• To experimentally test the critical size paradigm for bacterial cell size control.
• To elucidate the mechanism of cell size homeostasis in evolutionarily distant bacteria.

Main Methods:

• Single-cell microscopy was employed to track bacterial growth and division.
• Mathematical modeling was used to analyze cell size dynamics.

Main Results:

• Direct experimental evidence disproved the critical size threshold model.
• Escherichia coli and Caulobacter crescentus achieve size homeostasis by constant size increment between divisions, regardless of initial cell size.
• This mechanism robustly reduces size variations exponentially over generations.

Conclusions:

• Bacterial cell size control is achieved through a constant growth increment mechanism, not a critical size.
• This principle applies to various division types and growth rates.
• Constant size extension is likely regulated near the division process, offering new insights into cell-cycle control.