Flagellar Motors: The Secret Behind Bacteria’s Nearly 100% Energy Efficiency

When people think of motors, they typically envision those in vehicles or machines. However, biological motors have existed for millions of years, especially in microorganisms. Many bacteria rely on tail-like structures called flagella, which rotate to propel them through fluids. This movement is powered by a protein complex known as the flagellar motor.

The flagellar motor consists of two main components: the rotor and the stators. The rotor is a large rotating structure anchored to the cell membrane that drives the flagellum’s movement. Surrounding the rotor, the stators are smaller structures with ion pathways that transport protons or sodium ions, depending on the bacterial species. As these charged particles pass through, the stators undergo structural changes that apply force to the rotor, causing it to spin. While much research has focused on the stators, the exact structure and function of their ion pathways remain unclear.

A team led by Assistant Professor Tatsuro Nishikino from Nagoya Institute of Technology studied the flagellar motor in Vibrio alginolyticus, with collaborators from Osaka University, Kyoto Institute of Technology, and Nagoya University. Their findings, published in Proceedings of the National Academy of Sciences on December 30, 2024, used cryo-electron microscopy (CryoEM) to capture high-resolution images of normal and genetically modified V. alginolyticus. The team identified key molecular cavities for sodium ions by imaging stator complexes in various states.

New Model Explains Sodium Ion Flow Through the Flagellar Motor Stator in Vibrio alginolyticus and How Phenamil Inhibits It

Based on their results, the team proposed a model explaining sodium ion flow through the stator. The subunits forming the stators in Vibrio alginolyticus arrange in a ring, acting as size-based filters that selectively allow sodium ions into the identified cavities. The researchers also explored how phenamil, an ion-channel blocker, inhibits sodium ion flow through the stator.

Proposed Model of Sodium Ion Flow
The study’s findings could have significant medical implications. As Tatsuro notes, “Flagellar-based movement plays a role in the infections and toxicity of some pathogenic bacteria. One motivation behind this study was finding ways to restrict bacterial movement and inactivate them. Understanding the molecular mechanism of flagellar motility is crucial for this goal.”

In addition, insights into flagellar motors could lead to innovative designs for microscopic machines. Tatsuro explains, “Flagellar motors are molecular nanomachines with a diameter of roughly 45 nm and an energy conversion efficiency close to 100%. Our findings are a major step toward understanding their torque-generation mechanisms, which are essential for engineering nanoscale molecular motors.”

We hope further research will continue to uncover the secrets of these incredible natural machines!

Read Original Article: Scitechdaily

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