Mucus has a secret ingredient that stops bacteria in its tracks

Flu season is here and in turn, we’ve returned to the familiar sights and sounds of runny snot and thick phlegm. However, most of the time, mucus isn’t just a side-effect of illness. The slime, which coats over 200 square feet of our bodies including our eyes, mouths, and urinary tracts, actually serves a very important physiological purpose.

New research shows it can interfere with bacteria’s communication and behavior, effectively making them harmless and keeping us healthier in the process.

It’s been established that mucus is essentially the body’s security bouncer. It physically traps bacteria, viruses, toxins, and environmental ultra-fine particles like dust and pollution, acting as the first line of defense against invaders. The immune cells, antibodies, and antimicrobial proteins in mucus then attack and kill pathogens, before they get the chance to spread throughout the body and cause infection.

Sometimes, the mucus is coughed up or sneezed out — which is the body’s way of expelling pathogens. Mucus also acts as a lubricant under the skin’s surface, helping minimize friction between organs.

Now scientists from the Massachusetts Institute of Technology (MIT), Ohio State University, and Harvard Medical School have announced another powerful way mucus protects us: In a study released Monday in Nature Microbiology they revealed that mucus contains one key component that can disarm pathogens and prevent infection: “glycans,” which are specialized branches of sugar molecules. Hundreds of different glycans are found in mucus, and they have the ability to regulate how microbes behave.

Essentially, glycans bond with mucins, which are the building blocks of mucus, forming a toilet brush-like structure. Subsequently, glycans stop bacteria from communicating with each other, forming infectious biofilms, or attaching to surfaces.

“What we have in mucus is a therapeutic gold mine,” corresponding author Katharina Ribbeck, Ph.D., the Mark Hyman, Jr. Career Development Professor of Biological Engineering at MIT, explains. “These glycans have biological functions that are very broad and sophisticated. They have the ability to regulate how microbes behave and really tune their identity.”

To get to the bottom of what glycans can do, the team examined how they interact with a particular pathogen that causes infections in people with cystic fibrosis or compromised immune systems.

To do this, they first had to isolate glycans and exposed them to bacteria called Pseudomonas aeruginosa. After that exposure, the behavior of the bacteria changed dramatically: They no longer produced toxins, could attach or kill host cells, or express the genes essential for bacterial communication. In other words, they became way less harmful.

Glycans’ ability to disarm microbes makes a major, simple difference: If bacteria can’t function well, it’s much harder for them to inflict damage and cause infection.