Biofilms are the bane of hospitals' existence, because they consist of large colonies of bacteria living in slimy layers that can be very difficult to eradicate. Mucus protein can help. It makes a lot of sense when you think about it: Mucus is a defensive mechanism, protecting our noses, mouths, eyes and other membranes from would-be invaders. The thing is that no one has been sure just how this infection barrier works, according to MIT News. Former MIT postdoc Marina Caldara and current grad student Ronn Friedlander published a paper last week in Current Biology that observed the behavior of a bacterium in response to mucus proteins.