Dental cavity microbes create “superorganism” cluster

USA: A study led by researchers from the University of Pennsylvania School of Dental Medicine found that microbial groupings of bacteria and fungi found in tooth decay were more resistant to antimicrobials than their single-species equivalents.

The findings, published in in the journal Proceedings of the National Academy of Sciences (PNAS), suggests that when the fungus and bacteria cluster together, they form a “superorganism” that can crawl and leap across teeth – even spread to other parts of the body.

Almost accidental discovery

Found in the saliva of toddlers with severe childhood tooth decay, these assemblages can effectively colonize teeth.

“This started with a very simple, almost accidental discovery while looking at saliva samples from toddlers who develop aggressive tooth decay,” says Hyun (Michel) Koo, a professor at Penn Dental Medicine and a co-corresponding author on the paper.

Real-time live microscopy helped experiments

“Looking under the microscope, we noticed the bacteria and fungi forming these assemblages and developing motions we never thought they would possess: a ‘walking-like’ and ‘leaping-like’ mobility.”

The new set of findings came through further research by postdoctoral fellow in Koo’s group, Zhi Ren, was using microscopy that allows scientists to visualize the behavior of living microbes in real time.

Ren is the first author on the paper and part of the first cohort of the NIDCR T90R90 postdoctoral training program within Penn’s Center for Innovation & Precision Dentistry.

“(The technique) opens new possibilities to investigate the dynamics of complex biological processes,” he says.

The discovery led to a series of experiments using real-time live microscopy to study the attachment and eventual growth process.

“Leaping” microbes spread fast and wide

The researchers discovered that the microbial communities moved quickly and far – at velocities of more than 40 microns per hour on the tooth-like surface, which is comparable to the speed of fibroblasts, a type of cell in the human body involved in wound healing.

The scientists observed the assemblages “leaping” more than 100 microns across the surface within the first hours of growth. “That is more than 200 times their own body length,” Ren says, “making them superior to most vertebrates in terms of body size.”

Because these assemblages are found in saliva, targeting them early on could be a therapeutic strategy to prevent childhood tooth decay, says Koo. “If you block this binding or disrupt the assemblage before it arrives on the tooth and causes damage, that could be a preventive strategy.”

Beyond the applications for treating this specific disease, the researchers say, the new findings might be applicable in microbial biology in general.

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