If you’re obsessed with mucus, you might be a microbiologist. Trying to think of a human pathogen that won’t come into contact with a mucosa at some point is pretty difficult and is probably limited to organisms that grow exclusively on the skin. In a review published yesterday in NPJ Biofilms and Microbiomes, Cassie Bakshani explains the likely evolutionary history of our human mucosa as well as some exciting prospects for its future study.
It is thought that mucus first evolved as a feeding mechanism in corals in a primitive version of our beloved mucociliary escalator. However, the fact that it provided some kind of a barrier to microbes gave rise to some surprising evolutionary effects which can be seen in modern day sea creatures. Those creatures that don’t produce mucus, tend to be inundated with bacteria and are forced to produce strong antimicrobials to survive. Those that produce a mucus layer such as jelly fish, keep microbes to the outside which allows them to develop more specialised and intricate structures on the inside. The implication here is that the arrival of mucus on the evolutionary scene helped our ancestors to develop more complex and specialised tissues.
Of course, the mucus layer is not a strict microbial barrier in the sense that some microbes are able to pass through. On the whole, the mucus layer serves to keep commensal organisms in and pathogens out. Until, it doesn’t. A good pathogen will have a way of dealing with mucus which is also covered by the review. Probably the most famous example is H. pylori tunnelling its way to safety through the mucus layer in the acidic conditions of the stomach.
The review also thought provokingly compares the biofilm matrix to mucosal layer and claims that they have similar compositions and perform much the same task. The authors also discuss ways in which mucus could be exploited in biotechnology by making coatings using its physical properties but also by mining mucus layers from different creatures for new antimicrobials.
And did I say something about coral milking? Well, I didn’t know it existed before I read this review but I can tell you that I’m against it. It’s just not natural. Seriously though, coral milking is a bit unnatural and it's kind of a problem. You have to dehydrate corals in order to get them to over produce mucus that you can use for your favourite mucus related experiment. The problem is that mucus produced in this way has different physical properties than natural mucus. Now you know.
Evolutionary conservation of the antimicrobial function of mucus: a first defence against infection
Cassie R Bakshani, Ana L Morales-Garcia, Mike Althaus, Matthew D Wilcox, Jeffrey P Pearson, John C Bythell & J Grant Burgess
npj Biofilms and Microbiomes volume 4, Article number: 14 (2018)