Everyone hates mucus,  but what exactly is it? Mucus is not just the awful phlegm from your cough, it is actually a large and complex macromolecule found in our eyes, lungs, and gut, consisting of a protein backbone with complex sugars, also called glycans, attached to that backbone. It is usually thought that our mucus works as a simple barrier that physically shields our body from pathogens and other foreign substances. However, scientists at MIT recently discovered that the glycans, or sugars, in our mucus can actually trigger biochemical responses that protect us from pathogens.

In order to study how mucus affects bacterial formation of biofilms, which is an indicator of mucosal infection common in diseases like cystic fibrosis, Wheeler et al. decided to test the effects of mucus on the bacteria, Pseudomonas aeruginosa. A normally harmless bacteria, P. aeruginosa can cause a lung infection in people with abnormal mucus production. They found that mucus did disrupt the formation of biofilms, but instead of a typical mechanical disruption, it did so by triggering a biochemical response in the bacteria, changing the way the bacteria grows! Certain genes in the bacteria that cause toxicity were also downregulated, further “taming” the bacteria. They were intrigued by their results, but what in the mucus had caused this? By testing each component of the mucus, they found that the glycans in the mucus are the structures that “tamed” P. aeruginosa. They were able to recreate similar protective biochemical responses by using free mucus glycans, while simple carbohydrates such as monosaccarides were not able to trigger significant responses.

This study uncovered a new protective mechanism by our mucus, but it also opened a new can of worms. For example, how does the bacteria recognize and interact with the glycans? Are the glycans binding to a regulatory site in the bacteria, or are they affecting the metabolism of the bacteria? What specific glycans have this effect? The authors already have some hypotheses for these questions, and finding out the answers would improve our understanding of mucus’ role in bacterial infection, and also potentially inspire new generations of therapeutics for the treatment of bacterial infections. 

Managing Correspondent: Wei Li

News Article: How mucus tames microbes. Science Daily.

Sweet-Talking Slime Mollifies Pathogens. Genetic Engineering & Biotechnology News.

Original Article: Mucin glycans attenuate the virulence of Pseudomonas aeruginosa in infection. Nature.

Read More about Mucus: All About That Mucus: How it keeps us healthy

Image Credit: Image by Luisella Planeta Leoni from Pixabay

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