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“Like bacteria hitch-hiking on the fungi”—study shows how organisms “walk” across teeth

Researchers at the University of Pennsylvania discovered that oral bacteria can pair with fungi to create a type of organism that moves across teeth at an incredible speed, facilitating dental decay. (Image: AnaLysiSStudiO/Shutterstock)

PHILADELPHIA, US: A research team from the University of Pennsylvania has found that, within hours of growth, groupings of bacteria were able to “leap” more than 200 times their own body length across dental surfaces, offering an insightful explanation into the mechanism behind rapid bacterial colonisation and dental caries.

In a university press release, co-author Prof. Hyun (Michel) Koo, founding director of the Center for Innovation and Precision Dentistry at the university, stated that, although the organisms comprising the biofilm in the laboratory were non-motile, the combination of bacteria and fungi created a “superorganism”: an assemblage that was far more difficult to remove from teeth than either of its two constituents alone.

The research team was originally studying severe childhood caries in toddlers when they were shocked to find that the blend of bacteria and fungi actually developed the ability to “walk” and “leap”, when neither could do so before. The organisms in question, Streptococcus mutans and the fungus Candida albicans, were identified as the main components of the biofilm causing the severe caries in toddlers.

Dr Zhi Ren, a postdoctoral fellow working in the laboratory and one of the co-authors of the paper, utilised a form of microscopy that allowed the team to observe the changes in the organisms in real time. The bacteria and fungi were able to develop unexpected levels of adhesion and microbial tolerance. The fungi sprouted hyphae, which enabled the bacteria to better attach themselves and prevent removal.

Despite the secure attachment, the new assemblage was still able to move itself forward, “like bacteria hitch-hiking on the fungi,” said Prof. Koo. This ability meant that, once the assemblages were tested on human teeth in a laboratory model, the biofilm spread much faster than anticipated, because the organisms were able to move as they grew.

The findings could not only help dentists better understand the levels of prevention necessary to stave off severe caries, but could also help clinicians understand bacterial proliferation in other areas of medicine.

The study, titled “Interkingdom assemblages in human saliva display group-level surface mobility and disease-promoting emergent functions”, was published in the 11 October 2022 issue of the Proceedings of the National Academy of Sciences.


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