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Scientists uncover Campylobacter’s swimming tactics

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Scientists uncover Campylobacter’s swimming tactics

Researchers have found out how Campylobacter can swim faster in stickier liquids, such as in human guts.

Findings could help scientists halt the foodborne bacteria, because they show how the shape of its body and components that help it swim are all dependent on each other to work. This means any disruption to one part could stop the bacteria from getting through the body and into the gut.

A key step in Campylobacter jejuni’s invasion of the body is swimming through the viscous, or sticky, mucous layer of the gut. Researchers already know that Campylobacter jejuni swims faster in viscous liquids than in less-viscous liquids, like water, but until now they didn’t know why.

Scientists from Imperial College London, Gakushuin University in Tokyo and University of Texas Southwestern Medical Center filmed Campylobacter jejuni in action. Results are published in the journal PLOS Pathogens.

A tail of two ends
Campylobacter jejuni uses its two opposing tails, called flagella, to help it move. It has a flagellum at each end of its body that spin around to propel itself through liquid.

“It seemed very strange that the bacteria had a tail at both ends – it’s like having two opposing motors at either end of a ship. It was only when we watched the bacteria in action that we could see how the two tails work cleverly together to help the bacteria move through the body,” said co-first author Dr. Eli Cohen, from the Department of Life Sciences at Imperial College London.

The team created strains that had fluorescent flagella and used high-speed microscopy to see what happened as they swam around. They did this by mimicking a high-viscosity medium environment.

Scientists discovered that to move forward, the bacteria wrap the leading flagella around their helically shaped bodies, meaning both flagella were then pointing in the same direction and providing thrust. To change direction, they changed which flagella were wrapped around their body, enabling 180 degree turns and potential escape from confined spaces.

More to study and preventing infection
They found that the wrapping of tails was easier when swimming through viscous liquids; the stickiness helping push the leading flagella back around the body. The increase in wrapping at higher viscosity was accompanied by a rise in swimming velocity. In less-viscous liquids neither flagella were able to wrap around the body.

Videos do not solve all issues as the mechanism by which unwrapping occurs remains unclear. It is also not certain how unwrapped cells in low-viscosity media are able to swim at all.

Lead researcher Dr. Morgan Beeby, from the Department of Life Sciences at Imperial College London, said in setting out to understand how Campylobacter jejuni moves, the team resolved the apparent paradoxes of how it swims in one direction with opposing flagella and how it goes faster in more viscous liquids.

“As well as solving some long-standing mysteries, the research could also help researchers find new way to prevent infection by Campylobacter jejuni, by targeting any of its interconnected structures that help it move around.”

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