It looks like a caterpillar: this organism lives in the human mouth

Updated 8/23/2022 at 15:54

  • Hundreds of species of bacteria live in the human mouth.
  • One of them resembles caterpillars: the so-called Neisseriaceae.
  • The research team took a closer look at these organisms and discovered how the caterpillar-like form develops – and why it is helpful.

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It is warm and humid, making it a comfortable environment for microscopic bacteria: the oral cavity. There are over 700 species of bacteria in the mouth, including the Neisseriaceae. They look like small caterpillars: rod-shaped bacterial species that are usually elongated and adhering to each other. This species, belonging to the microbial family, occurs in approximately one in two people.

A research team led by environmental cell biologist Silvia Bulgheresi of the University of Vienna and microbial genetics Frédéric Veyrier of the Institut national de la recherche scientifique (INRS) has discovered new information about small organisms. The research paper has been published by the team in Nature Communications.

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The shape of the caterpillar helps bacteria stick to the mouth

To find out how oral bacteria grow and divide, scientists took a closer look at the Neisseriaceae. For the study, the team used electron microscopy to examine the shape of cells in the entire Neisseriaceae family. These include not only caterpillars-like threads, but also standard cellular forms, stamens and cocoons.

The bacteria likely developed the shape of a caterpillar to adapt to their habitat – the mouth. Because the mouth is not ideal for microbes. “The epithelial cells that line the inner surface of the mouth are constantly shed, and along with the flow of saliva, organisms that settle on this surface fight for a foothold,” reads a press release from the University of Vienna.

As a result, the Neisseriaceae likely continued to develop. The caterpillar shape allows them to stick better.


Scanning electron microscope image resembling a caterpillar of the bacterioid Simonsiella muelleri, up to four micrometers long.

© Sammy Nyongesa and Frédéric Veyrier / University of Vienna

The Neisseriaceae have developed a special way of cell division and cooperation

The authors of the study found that the organisms evolved from rod-shaped ancestors. Their cell division is usually strange, then they break apart. However, some commensal Neisseriaceae attach themselves to the substrate in tips and divide longitudinally, ie along their long axis. After the division is complete, the cells stick together and form threads that resemble caterpillars.

Some of its cells form different shapes. The researchers assume that this enables them to perform certain functions of the whole thread: “Multicellularity enables cells to cooperate, for example in the form of division of labor, and thus can help bacteria survive the nutritional stress.” Study author Frédéric Veyrier explains: “We suspect that the shape of the cell has changed in the course of evolution by revising its elongation and division processes, perhaps for better development in the oral cavity.”

Neisseriaceae may be helpful in further research

Silvia Bulgheresi from the Department of Functional and Evolutionary Ecology at the University of Vienna says: “In addition to helping to understand the evolution of cell shape, multicellular Neisseriaceae could be useful for studying how bacteria learned to live on the surface of animals, the only place ever found. Incidentally, half of us carry them in our mouths.

Sammy Nyonges, a PhD student on the Veyrier team at INRS, suggests that the evolutionary approach adopted in Neisseriaceae research could ‘discover new, unexpected target proteins’. However, according to the researchers, genetic tools are needed to study bacteria more closely.

Sources used:

  • nature announcements: “The evolution of longitudinal division in multicellular bacteria of the Neisseriaceae family” (August 22, 2022)
  • University of Vienna media portal: “Caterpillar-shaped bacteria crawling in our mouths” (August 22, 2022)
  • sciencealert.de: “This caterpillar-like organism can now crawl in your mouth” (23 Aug 2022)

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