Friendly Viruses Protect Us Against Bacteria
One of our most important lines of defense against bacterial invaders is mucus. The slimy substance coats the inside of the mouth, nose, eyelids, and digestive tract, to name just a few places, creating a barrier to the outside world. Mucus is also home to phages, viruses that infect and kill bacteria. They can be found wherever bacteria reside, but Jeremy Barr and his colleagues noticed that there were even more phages in mucus than in mucus-free areas just millimeters away. The saliva surrounding human gums, for example, had about five phages to every bacterial cell, while the ratio at the mucosal surface of the gum itself was closer to 40 to 1. The researchers found that the phages are studded with antibody-like molecules that grab onto the sugar chains in mucins. This keeps the phages in the mucus, where they have access to bacteria, and suggests that the viruses and the mucus-producing tissue have adapted to be compatible with each other.