The Grossest Hero of the Body: How Mucus Fights Bacteria

(Photo : James Archer/U.S. Centers for Disease Control and Prevention - Medical Illustrator)

Many of us feel negative about mucus, especially during allergy and cold seasons, and think of it as just a mere annoyance. However, recent research suggests that mucus does a lot more than we think.

While scientists already knew that mucus acts as a lubricant and as a physical barrier to bacteria and viruses, researchers from the Massachusetts Institute of Technology, Ohio State University, and Harvard Medical School teamed up to look more into the properties of mucus. Published in the latest issue of Nature Microbiology, they looked specifically at how mucus and its components interact with a bacteria called Pseudomonas aeruginosa.

P. aeruginosa is a commonly found bacteria that's known for its multiple drug and antibiotics resistances. It often strikes when the body's immune system is compromised (called opportunistic infections). At large quantities, they can manifest into biofilms to create inflammation and sepsis.

When exposed to several types of mucus, not only did P. aeruginosa biofilms disintegrate, but they also suppressed several functions important for P. aeruginosa virulence like quorum sensing (the ability to express certain genes relative to cell population), siderophore biosynthesis (the creation of iron-transporting compounds important to bacterial growth), and type-3 secretion (the ability to detect and infect other organisms).

Not only does mucus provides a physical barrier, but it also hinders the actions of bacteria like P. aeruginosa. As to why this occurs, the researchers found that the answer lies in a type of compound called glycans, sugar molecules with specialized behavior. These glycans attach to mucins, proteins that are responsible for the gel-like characteristics of mucus, to create structures that are behind mucus' bacteria-inhibiting properties.

This research now gives us a lot more insight into the importance of mucus to our immune system, more important than we ever thought. Not only do they help provide lubrication and a physical barrier to pathogens, but its components also have actual virulence-inhibiting properties. Thanks to this study, we can now exactly pinpoint what is responsible: specialized sugar molecules called glycans.

This study now lays the groundwork for future research into mucus. While we now know who is responsible, the actual mechanism as to what exactly goes on between mucin glycans and bacteria has yet to be determined.

There's also the question of why diseased mucus no longer exhibits these bacteria-inhibiting properties, although the authors propose that this is due to mucin's ability to bond to microorganisms, as well as its inherent protective properties, being altered by the diseased mucus.

Being able to isolate and create a library of mucin–glycans would have tremendous effects, especially for bacteria that have proven to be resistant to both drugs and antibiotics. Researching the exact effects of specific glycans could develop into new treatment strategies and therapeutics.

There's a lot more work to be done, and it seems like we've only scratched the surface, but it's a real possibility that this can now bring in more interest in this often-overlooked field of study. You never know, you might have compounds found in mucus to thank for your life one day.