Wheels of life.
Image credits Morgan Beeby/Imperial College London.

Pretty, isn’t it? This is an image of a bacterial flagellum, the only example of a biological wheel that we know of. Spun by nano-sized protein motors, it acts as a propeller powering bacteria such as Campylobacter forward.

Morgan Beeby and his colleagues at the Imperial College London used electron microscopy to image these structures in high resolution and three dimensions for the first time. With the powerful magnification these microscopes are capable of, even the tiny mechanisms that provide minute amounts of torque to the motors become visible.

Beeby’s team used electron cryotomography, a method that freezes the bacteria, to allow the motor to be imaged from all angles.

These wheels come in a wide variety of shapes, sizes, and power output. Campylobacter’s motor for example is powerful enough to allow the bacteria to penetrate through the protective layer of cells in your digestive tract. A wheel-like structure at the base of the flagellum, called a stator, provides the torque necessary for this.

Campylobacter and Salmonella motors.
Image credits Morgan Beeby/Imperial College London.

Campylobacter has almost twice as many stators as Salmonella, and these sit in a wider ring — this gives it increased torque and leverage.

In fact, these motors are so efficient that nano-roboticists are looking for ways to incorporate them into their nanites to avoid having to develop and build their own.

The full paper, titled “Diverse high-torque bacterial flagellar motors assemble wider stator rings using a conserved protein scaffold” has been published online in the journal PNAS and can be read here.


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