Scientists have made a discovery which could lead to finding ways to stop the spread of certain bacteria that cause food poisoning.
Many bacteria can swim, allowing them to infect and spread in the case of pathogenic species. Almost all swimming species of bacteria move using corkscrew-like propellers called flagella. Bacterial flagella are made up of thousands of protein building blocks arranged in spiraling chains.
The scientists, including researchers from the University of York in England, discovered that some types of bacteria have evolved complex flagella made up of many different types of proteins to enable them to escape when trapped in small spaces.
Species of bacteria such as Campylobacter jejuni, which causes food poisoning, maintain multiple components in their flagella, according to the research published in the Nature Communications journal.
In many of their natural environments flagellated bacteria have to move through structured environments, such as sediments, mucus layers or biofilm matrices, where the bacteria are at risk of getting stuck in passages too narrow for cells to pass. In these environments, polarly flagellated bacteria may use the flagella-mediated screwing movement to escape from traps or to enable a passage through.
Researchers created a mutant incapable of this screwing motility. The strain retained vigorous free swimming, but spreading through soft agar was diminished, demonstrating that this mode of movement likely gives an advantage for moving through structured environments.
Co-author of the work, Laurence Wilson, from the department of physics at the University of York, said the study gives a better understanding of the physics of bacterial infection which could lead to new ways of blocking the transmission of harmful infections.
“The question of why some bacteria such as E. coli have flagella made up of one type of protein while others have more complicated flagella made up of many different types has been a longstanding mystery,” he said.
“Nature likes to keep things simple. In any machine, more components mean more things that could go wrong. Our study has shown that complicated flagella have a function which helps bacteria escape when they get stuck in tight spaces, an advantage which outweighs the cost of maintaining genes to encode the various protein building blocks.”
The team looked at a species of bacteria called Shewanella putrefaciens and found that when they get stuck in a tight space their multi-component flagella buckle, wrapping around the cell bodies and allowing them to corkscrew free.
Building blocks in the flagella of this species are arranged in the optimal way as when they removed or swapped around, the bacteria’s ability to swim, in open waters or in tight spaces was impaired.
Researchers from the Institute of Microbiology and Molecular Biology in Geissen, Germany, established where the different building blocks lie within individual flagellum. Computer scientists from The Philipps University of Marburg, Germany then built simulations to test the effect of slowly varying the physical properties of the flagellum.
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