Researchers from Imperial College London, Kitakyushu University in Tokyo and the University of Texas Southwest Medical Center have found the reason as to why a species of bacteria (which is known for food poisoning) can swim faster in stickier liquids; in this case, the human gut. With this research, the potential to stop the bacteria before entering the gut can be established.
Campylobacter jejuni is responsible for millions of food poisoning cases every year, and a key step in its invasion of the body is swimming through the viscous (sticky) mucous layer of the guts. Researchers have observed that C. jejuni swims faster in viscous liquids than in less-viscous liquids, like water, but until now they didn’t know why. So they went on to film C. jejuni in action to uncover the mystery. Their results are published in PLOS Pathogens.
C. Jejuni uses its tail called flagella, to swim in the gut. However what had confused scientists was that there were two opposing flagella at each end which spin around to propel itself through the 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.”
Co-first author Dr. Eli Cohen, from the Department of Life Sciences at Imperial
The team created C. jejuni strains that have fluorescent flagella and used high-speed microscopy to see what happened as they swam around. They discovered that to move forward, the bacteria wrapped their leading flagella around their helically shaped bodies, meaning both flagella were then pointing in the same direction and providing unified thrust. To change direction, they changed which flagella were wrapped around their body, enabling quick 180 degree turns and potential escape from confined spaces. They also found that the process of wrapping the flagella was easier when swimming through viscous liquids; the stickiness helped push the leading flagella back around the body. In less-viscous liquids neither flagella were able to wrap around the body.
“Our study kills two birds with one stone: in setting out to understand how C. jejuni moves, we resolved the apparent paradoxes of how it swims in one direction with opposing flagella and how it swims faster in more viscous liquidLead researcher Dr. Morgan Beeby, from the Department of Life Sciences at Imperial
Through this research, the team was able to find that the helical shape of the bacteria was crucial for allowing the wrapping mechanism of the flagella, which shows co-dependence of both the body and the flagella.