Tag Archives: mucus

Molecules in mucus subdue microbes to make them harmless

More than 200 square meters of our bodies — including the digestive tract, lungs, and urinary tract — are lined with mucus. Far from being a gross waste product, this slippery secretion produced by, and covering, the mucous membranes serves an important physiological purpose.

It has been established that mucus is the body’s security bouncer physically trapping pathogens, toxins, and fine particles like dust and pollution. The cells of the immune system in the mucus then attack and neutralize the invading germs before they get the opportunity to spread throughout the body and cause infection. In some instances, mucus is coughed up or expelled – which is the body’s way of forcing the pathogens out of the body. Mucus also lubricates the eyes so they can blink and the throat so it can swallow. It also serves as a lubricant under the skin’s surface to help minimize friction between the organs.

New research at the Massachusetts Institute of Technology (MIT) and published in Nature Microbiology shows one of mucus’s unexpected beneficial properties: mucus contains sugars that can interfere with bacteria’s communication and behavior, effectively stopping the formation of dangerous, tough biofilms and making them harmless.

The research was funded by the National Institute of Biomedical Imaging and Bioengineering, the National Institutes of Health, the National Science Foundation, the National Institute of Environmental Health Sciences, and the MIT Deshpande Center for Technological Innovation.

Katharina Ribbeck and her colleagues study compounds called mucins in mucus. Mucins are long polymers, or molecular chains, densely studded with sugars. They “look like mini bottlebrushes,” Ribbeck said, except bristling with sugar molecules where whiskers would be.

“What we have in mucus is a therapeutic gold mine,” said Ribbeck, the Mark Hyman, Jr. Career Development Professor of Biological Engineering at MIT. “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.”

Ribbeck and others have shown that mucus can stop microbes from binding to surfaces. Researchers focused on how glycans were interacting with an opportunistic microbial pathogen called Pseudomonas aeruginosa, the bacterium commonly causing serious infections in people with weak immune systems and cystic fibrosis patients.

They found that when bacteria were exposed to glycans isolated from mucus, they were disarmed; the microbes stopped attaching to or killing host cells, halted production of toxic molecules, and microbial genes that are involved in bacterial communications weren’t expressing. The new study is the first to “identify that the glycan component” — that is, the sugars grafted to the mucins — “is responsible for suppressing antagonistic microbial behaviors.”

They now plan to study the impact of individual glycans out of hundreds that can be found in mucus. They also want to investigate how glycans affect other kinds of pathogens like Candida albicans and Streptococcus bacteria. They already know that glycans can stop Streptococcus from sharing genes, a primary way that drug resistance spreads among microbes.

“What we find here is that nature has evolved the ability to disarm difficult microbes, instead of killing them. This would not only help limit selective pressure for developing resistance, because they are not under pressure to find ways to survive, but it should also help create and maintain a diverse microbiome,” Ribbeck says.

Scientists, including Ribbeck, are also looking into the development of artificial mucus, which might be a new approach to fighting pathogens that does not involve traditional antibiotic drugs.

Researcher finds new immune system in mucus

Think about mucus – what comes to mind? It’s slimy, it’s gross, no one really likes it, right? Well, as a team from San Diego State University showed, mucus is also home to a very powerful immune system that has the possibility to change the way doctors treat a number of diseases.

Bacteriophages are basically viruses that infect and replicates within bacteria. The research addressed all sorts of animals, from sea anemones to mice and humans, and found that bacteriophages adhere to the mucus of all of them. They placed bacteriophage on top of a layer of mucus-producing tissue and observed that the bacteriophage formed bonds with sugars within the mucus, adhering to its surface every single time.


They then challenged them by injecting E. Coli in the mucus, and they found that the bacteriophage attacked and killed off the E. coli in the mucus, effectively forming an anti-microbial barrier protecting the host from infection and disease.

In order to test their discovery, they then conducted parallel research on non-mucus producing cells, infecting them with E. Coli, in the same fashion. The results were disastrous for the cells.

“Taking previous research into consideration, we are able to propose the Bacteriophage Adherence to Mucus — or BAM — is a new model of immunity, which emphasizes the important role bacteriophage play in protecting the body from invading pathogens,” Barr said.

But what makes this finding really special is that that the bacteriophage are already present on all humans and animals; they are recruited almost as mercenaries by cells who support them and then act as protectors to the host, attacking invaders on their own.

“The research could be applied to any mucosal surface,” Barr said. “We envision BAM influencing the prevention and treatment of mucosal infections seen in the gut and lungs, having applications for phage therapy and even directly interacting with the human immune system.”

Research paper.


Why is Rudolph’s nose red? Scientists explain


(c) Flickr

Labelled as an outcast by the rest of Santa’s sleigh pulling reindeer, Rudolph the red-nose reindeer, though mocked off, is indispensable and without him Christmas might not make it to every house from all corners of the globe. With his very shiny nose, Rudolph guides Santa’s sleigh even through the harshest of weather, but exactly why is his nose so red? Dutch scientists suggest that Rudolph’s nose has  microvascular flow issue in his nasal mucosa.

“In colder climates and also when they are higher up in the atmosphere pulling Santa’s sleigh, the increase in blood flow in the nose will help keep the [nose’s] surface warm,” Dr. John Cullen of the University of Rochester

The scientists used high-tech instruments like hand-held intravital video microscopes to analyze and then compare the blood vessels of two reindeer (Rangifer tarandus) with those of human volunteers – five were healthy and one had nasal polyps. They found reindeer have 25 percent more capillaries carrying blood to their nasal area. Reindeer, like most mammal, don’t sweat and in turn have to rely on other methods to regulate their internal body heat, like through their noses. When put to run on a treadmill, thermographic imagery revealed hot spots in the reindeer’s nose. Also, the researchers found glandlike structures in the nasal mucous membrane of reindeer, which were surrounded by capillaries.  The scientists at  Erasmus Medical Center in Rotterdam, the Netherlands, and the University of Rochester in New York write in their paper:

“The exceptional physical burden of flying with a sleigh with Santa Claus as a heavy load could have caused cerebral and bodily hyperthermia, resulting in an overworked nasal cooling mechanism that resembles an overheated cooling radiator in a car: Rudolph suffered from hyperemia of the nasal mucosa (a red nose) under more extreme heat loads during flight with a sleigh.”

Curiously enough, one  of the humans was examined after inhaling 0.0035 ounces (100 milligrams) of cocaine (for the sake of science), “a drug routinely used in ear, nose, and throat medicine as a local anaesthetic and vasoconstrictor.”

“We’re kind of glad they didn’t do the same thing with the reindeer, because the last thing we would want is reindeer on cocaine, pulling Santa around the sky,” said Cullen.


Mucous cells on the stomach lining

The war against bacteria: mucus to the rescue

Mucous cells on the stomach lining

Mucous cells on the stomach lining

Bacteria biofilms, when formed, pose a significant health risk in industrial applications, like food processing, and medical settings. Researchers at MIT suggest a new weapon for fighting bacterial formations in the form of nature’s own line of defense – mucus.

Mucus lines most of the wet surfaces of the body, including the respiratory and digestive tracts, and acts as a barrier against infection. However, scientists did not know until recently how exactly does it manages this.

“Mucus is a material that has developed over millions of years of evolution to manage our interactions with the microbial world. I’m sure we can find inspiration from it for new strategies to help prevent infections and bacterial colonization,” says Katharina Ribbeck, the Eugene Bell Career Development Assistant Professor of Biological Engineering and senior author of the paper

Ribbeck and her colleagues found that mucus contains proteins that prevents bacteria from adhering to surfaces, like tissue. These findings were made after the scientists studied the behavior of Pseudomonas aeruginosa bacteria in a growth medium that contained soluble purified mucins — long proteins with many sugar molecules attached.

For the bacteria to effectively penetrate the mucus layer and reach tissue where it can wreak havoc, it needs to bind and form bacterial clusters. Clumps of bacteria are much more difficult for the immune system to clear, because immune cells are specialized to attack individual bacterial cells.

“In general, you want to have bacteria around, you just don’t want them to team up,” Ribbeck says. “You want to them to be mixed with many other bacteria that are good for you. You don’t want a single species to take over, because then they may overgrow the system.”

The mucus was found to stop bacteria from adhering and thus prevent cluster formations, instead it leaves individual bacteria suspended in a gooey mix. What important is that mucus does not kill bacteria, but simply blocks it from reach its target. This ensures that bacteria is less likely to develop tolerance to mucins, as they do under antibiotics that kill them.

In aging, dehydrated or diseased bodies, mucus formation doesn’t regenerate as well as it should, and thus bacteria clusters sometimes manage to form, causing infections in the process.

The researchers are now investigating exactly how mucins prevent bacteria from losing their motility, and also how they block infection by nonmotile bacteria. Still, their study proves that mucus isn’t a simple slimy substances that blocks just about anything. The researchers plan on developing mucin coatings that may help prevent biofilm formation on medical devices and that could also find applications in personal hygiene: incorporating them into products such as toothpaste or mouthwash may supplement the body’s own defenses, especially in people whose natural mucus has been depleted, Ribbeck says.

Findings appear in the journal Current Biology.