Cholera, which kills about 95,000 people each year, is caused by Vibrio cholerae bacteria that infect the small intestine. These bacteria use flagella—tail-like rotary structures—to swim toward and penetrate intestinal cells. Although researchers long knew the proteins that form flagella, the precise molecular arrangement and how the parts assemble and rotate remained a major gap in knowledge.
Researchers at Yale School of Medicine published new findings in Nature Microbiology that resolve this gap by imaging flagella in living V. cholerae at near-atomic resolution. Jun Liu, the senior author, said such resolution is needed to understand assembly and rotation. Wangbiao Guo, the first author, described the structure as a “70-year mystery.” The team developed a microscopy approach that involved engineering bacteria with flagella proteins that light up, freezing the cells in liquid ethane, and using a powerful electron microscope to capture the structures.
The images reveal how four flagella proteins occupy specific positions inside a hydrophilic protective casing, or sheath. That sheath had prevented earlier studies from resolving the structure. The work shows the flagellum core is similar to other bacteria but the surface differs, suggesting unique adaptations within the sheath. One possibility is that the hydrophilic sheath acts like a lubricant, so the flagellum can rotate independently of the outer casing and move more effectively through liquid and the mucus layer of the small intestine.
Liu said the images and methods open paths for further study and could help develop drugs that target flagella or find other ways to attack cholera. The study was supported by the National Institutes of Health, the National Science Foundation, Yale University, and several foundations. The content is the authors’ responsibility. Source: Yale.
Difficult words
- flagellum — tail-like structure bacteria use to swimflagella
- hydrophilic — attracted to water; mixes with water easily
- sheath — a protective covering around a structure
- rotary — turning around a central point or axis
- resolution — level of detail visible in an image
- lubricant — a substance that reduces friction between surfaces
- assemble — to join parts together into a whole
- penetrate — to enter or pass through something
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How could new images of flagella help scientists develop drugs to attack cholera? Give reasons.
- What are possible benefits and risks of using high-resolution imaging to study disease-causing bacteria?
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