Beyond brushing teeth: Can our mouth clean itself?

Most of us dread brushing and flossing. But what if your mouth could clean itself? Scientists are working on ways to hack the bacteria in your mouth so they do the dirty work for you – literally.

The idea is simple: help the good bacteria grow strong and push the bad ones out. If it works, it could mean fewer cavities, less scraping at the dentist and, maybe one day, no more brushing or flossing.

Bacteria battle inside your mouth

Your mouth is home to hundreds of kinds of bacteria. Some help you, and others hurt you. Right now, they’re all battling it out for space on your teeth.

The sticky film you feel after a long day? That’s a biofilm – a mix of bacteria all building a home together on your enamel. Some of them eat sugar and make acid, which wears away your teeth and causes cavities.

For years, researchers focused on identifying the bad bacteria – like Streptococcus mutans – and targeting those. But there’s a catch. Even within a single species of bacteria, there are hundreds of strains. That makes things complicated.

So, instead of trying to classify every strain, a research team led by scientists at UC Berkeley is zooming in on the bacteria’s DNA – specifically, the parts of it that drive how bacteria act in your mouth.

Molecules that help bacteria stick

By digging into a huge database of bacterial DNA from saliva samples, the researchers found something interesting.

A group of genes – called a gene cluster – showed up in strains that were more often linked to the presence of cavities. This cluster produces two molecules that help bacteria stick to each other and to your teeth.

One molecule makes bacteria clump up like glue. The other enables bacteria to make molecules that join and form chains, like a string. Together, these sticky molecules help bacteria form a strong biofilm – that gunky layer you feel on your teeth when you haven’t brushed.

Not all strains have this cluster. But some of the worst cavity-causing strains do, including the infamous S. mutans.

Smarter bacteria for teeth cleaning

The scientists believe they can take these sticky-making genes and move them into bacteria that are actually good for your mouth.

Streptococcus salivarius already supports a healthy mouth but struggles to stick to your teeth, which makes it a weak probiotic.

By boosting it with the sticky genes, researchers think they can help S. salivarius form a stronger biofilm. That way, the helpful bacteria can push out the harmful ones and take over the neighborhood – possibly reducing the need for constant brushing.

“Particular strains belonging to the same species can be a pathogen or a commensal or even probiotic,” explained Wenjun Zhang, a chemical and biomolecular engineering professor at UC Berkeley who led the research.

“After we better understand these molecules’ activity and how they can promote strong biofilm formation, we can introduce them to the good bacteria so that the good bacteria can now form strong biofilms and outcompete all the bad ones.”

What makes these molecules special

The gene cluster includes about 15 pieces of DNA. These don’t keep the bacteria alive – they’re part of what’s called a “specialized” metabolic pathway. In simple terms, they let bacteria make extra tools to help them compete.

Some bacteria use these extra genes to produce antibiotics. Others use them to grab more nutrients. In this case, the genes make sticky molecules that help bacteria hold on to your teeth better.

These specialized metabolites enhance survival in certain ways, noted McKenna Yao a Berkeley graduate student and co-first author of the study.

“Many, for example, are antibiotics, so they can kill other bugs, or others are involved in metal acquisition – they help the bacteria monopolize the resources in their environmental niche,” said Yao.

“Being able to produce these, especially in a microbial community, helps the bacteria boot out the other guy and guard their resources.”

The researchers named the sticky molecules mutanoclumpins. They think that if they can fully understand how these work, they could either stop bad bacteria from making them or help good bacteria use them better.

Brushing teeth still matters – for now

This isn’t the team’s first discovery. A couple of years ago, they found a different gene cluster that produces an unknown antibiotic in oral bacteria. Another one made a different type of sticky molecule.

This new discovery adds a further piece to the puzzle of how bacteria in your mouth work together – or against each other.

“We are looking for something which is correlated with cavities, with disease. If one day we can prove that, under certain conditions, this is really a bad molecule you want to prevent, we might develop genetic or chemical inhibitors to inhibit their production, so hopefully the bacteria will not make them, and you have fewer cavities,” Zhang said.

“Meanwhile, we also look at other molecules correlated with health, allowing a simple strategy to directly engineer the microbes to make more of them.”

The future goal is to build a full map of all these special molecules – to see what exactly your oral bacteria are up to. That could lead to smarter ways of managing oral health, with engineered probiotics doing most of the work. But for now, brushing still matters.

“The best way you can remove the biofilm on your teeth is to brush,” Yao said. “We believe that there’s actually a better way of disrupting that biofilm, but we’re just beginning to understand what the complexity is within the mouth.”

The full study was published in the journal Proceedings of the National Academy of Sciences.

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