Your Toothbrush Is Teeming With Unknown Viruses, Say Microbiologists

Your bathroom is teaming with biodiversity. Microbiologists have discovered a rainforest of unknown microbial species from your toothbrush to your showerhead. But should we be concerned?

In a new study published in Frontiers in Microbiomes, researchers from Northwestern University collected samples from 32 toothbrushes and 92 showerheads across the United States and found hundreds of different viruses on their surfaces, many of which had never been seen before.

“We may think of our toothbrushes and showerheads in one way, but in another sense, they are a habitat for microbes, a place where microbial ecology happens,” the study’s lead author, Erica Hartmann, told Newsweek. “It’s a microbial world; we just live in it.”

The particular microbes detected in this study belong to a group of viruses called bacteriophage, which have evolved to infect bacteria, not humans.

“There’s nothing in our findings that suggests any need for concern or increased cleaning,” Hartmann said. However, that doesn’t mean the researchers aren’t excited by their findings.

“Toothbrushes and showerheads harbor phage that are unlike anything we’ve seen before,” Hartmann said. “Not only did we find different phage on toothbrushes and showerheads, we found different phage on each toothbrush and each showerhead. This amount of diversity is huge, and it isn’t because of anything specific to toothbrushes or showerheads. There are just so many phage out there waiting to be discovered.”

So, why should we care about these bacteria-infecting viruses?

“There’s a lot of interest in harnessing phage for biotechnology or medical applications,” Hartmann said. “Penicillin comes from moldy bread. It could be that the next great antibiotic will be based on something that grew on your toothbrush.”

For example, phage viruses could be used to kill disease-causing bacteria in plumbing systems and waterways.

“We want to look at all the functions these viruses might have and figure out how we can use them,” Hartmann said. “Even if this doesn’t lead to some great new technology, it’s important to observe and record the diversity of phage because it expands our fundamental understanding of biology.”

The study follows previous research by Hartmann and colleagues at the University of Colorado at Boulder, which investigated the bacteria that live on these bathroom surfaces.

“This project started as a curiosity,” Hartmann said. “We wanted to know what microbes are living in our homes. If you think about indoor environments, surfaces like tables and walls are really difficult for microbes to live on. Microbes prefer environments with water. And where is there water? Inside our showerheads and on our toothbrushes.”

This doesn’t mean you should instantly bleach down your toothbrush and shower head—microbes are all around us, the vast majority of which do not make us sick. Many may even be beneficial.

“It’s really important to work with the microbes, not against them so that we don’t create worse problems for ourselves—like superbugs,” Hartmann said.

Instead of disinfectant, soaking your showerheads in vinegar can help remove calcium buildup. You should also replace your toothbrush every three to four months or when the bristles are worn or frayed, as this can affect how effectively they remove plaque and food from your teeth.

“By staying curious and really learning about the microbes that surround us, we will be able to make better decisions about things like how we design and care for our showerheads and toothbrushes—and potentially make some revolutionary new discoveries in the process,” Hartmann said.

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Huttelmaier, S., Shuai, W., Sumner, J., & Hartmann, E. M. (2024). Phage communities in household-related biofilms correlate with bacterial hosts but do not associate with other environmental factors.
Frontiers in Microbiomes
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