Mucins Attacking and Regulating Biofilms

In a recent study published in Nature magazine, a group of scientists researched and developed a hypothesis that the body’s production of mucins helps with the regulation and diffusion of Pseudomonas aeruginosa based biofilms. A biofilm, very simply defined, is a group of cells clustered together that have adhered to a surface. Biofilms can and do exist in the human body on many different surfaces (such as in the lungs or the intestines), forming a community of bacteria that can consist of one type of bacteria or many different genus and species co-existing in symbiosis. When the human body becomes exposed to a toxic element or becomes immunocompromised, biofilms can become unregulated and cause or further the side effects of disease. So what method of attack does the human body utilize for the regulation of biofilms to keep from essentially waging biological warfare and harming their host?

In a paper titled “Mucins trigger dispersal of Pseudomonas aeruginosa,” Julia Co et al. developed a study that supported the hypothesis that the body’s production of a material called mucin is one way the human body is able to accomplish such a task. Mucus is vital to the many of the body’s functions, such as keeping the surface of the lungs clear of pathogens, and mucins are a structural part of mucus. Mucins are the parts of mucus that resemble “bottle-like structures with dense O-linked glycosylation” (1) and this structure of the mucins is what compromises the “gel-forming polymers” (1) of mucus. Basically, mucins are what give mucus its consistency.

There exist many studies that focus on the clearance of biofilms, but the team of the aforementioned study wanted to study the effects of clearing biofilms in a more natural mucus environment, one that consisted of mucus and therefore mucins. The team focused on P. aeruginosa biofilms and established their biofilms by growing P. aeruginosa in an environment that closely resembled one that would be found naturally in the human body, with the use of a flow-cell system that allowed mucins to flow freely across the surface of the biofilms much like would be found in vivo. The team subjected their established biofilms to two different types of mucins, MUC5AC and MUC2, in different concentrations in the flow-cell systems, as well as other mucus consistent films as controls. The results were consistent with their hypothesis, in that the flow of mucins across the biofilms in a concentration of 0.5% or higher would cause the biofilms to not only disassemble but also kept the small number of cells remaining on the attached biofilm surface under check. Interestingly, the study also showed evidence that the mucins however did not have a lethal effect on the biofilms, just a regulatory one. If the mucins were removed or the concentration altered to below the working threshold, the small concentration of remaining biofilm would not only reestablish itself into its original biofilm size but some of them would grow up to three times their initial size. The size of the reestablished biofilm was dependent on how long each of them were subject to the effect of the mucins: the longer the exposer to the mucins in a concentration of 0.5% or higher, the slower the biofilms returned to their original size.

While biofilms exist naturally in the human body and many other manmade structures, their deregulation can have detrimental effects and even cause disease, such as cystic fibrosis of the lungs or infection in the human intestine. Studies such as the one referenced above conducted by these amazing scientists are an important step to regulating these terrible diseases and to finding ultimately a cure of method of keeping disease symptoms under control.