Where and how many: evolutionary diversification of a molecular switch regulating flagellar patterns

Area of Science:

• Microbiology
• Molecular Biology
• Evolutionary Biology

Background:

• Flagella are essential rotating organelles enabling bacterial locomotion and environmental navigation.
• Bacterial flagellation patterns (number and location) vary significantly across species.
• A conserved molecular switch involving FlhF and FlhG regulates these diverse flagellation patterns.

Purpose of the Study:

• To review the mechanisms by which the FlhF/FlhG switch controls bacterial flagellation patterns.
• To explore the evolutionary origins of the FlhF and FlhG proteins.
• To highlight how ancient cellular machineries are repurposed for novel regulatory functions.

Main Methods:

• Review of existing literature on bacterial flagellar regulation.
• Analysis of the molecular mechanisms of the FlhF/FlhG switch.
• Comparative genomics and evolutionary analysis of FlhF and FlhG.

Main Results:

• The FlhF/FlhG switch, comprising a GTP-binding protein and an ATPase, is conserved across many bacterial species.
• FlhG stimulates the GTPase activity of FlhF, mediating flagellation pattern control.
• Evolutionary origins of FlhF and FlhG are linked to the signal recognition particle (SRP) system and MinD-dependent cell division machinery, respectively.

Conclusions:

• The FlhF/FlhG system demonstrates how evolution repurposes ancient protein machineries to establish new regulatory functions.
• This conserved switch provides a key mechanism for controlling diverse bacterial flagellation patterns.
• The adaptability of protein-based regulatory networks is exemplified by this system.