When people think of bacteria, they often imagine harmful little organisms that are out to get us and cause our body havoc. A new study is now showing that bacteria can actually help our bodies fight invading microbes. Until now, mucus has been the most vital part of our bodies defense system. Mucus lines the inside of our mouths, nose, eyelids, digestive tract, and many other places in order to form a barrier to external threats. Mucus also harbors phages, which are viruses that infect and kill harmful bacteria. Phages are found wherever there is bacteria, however are abundant in areas with more mucus. Mucus does not only protect humans. Fish, worms, and corals have the benefit of having their whole external body covered in mucus, further protecting them from bacteria. For this study, researchers selected the phages and bacterium, but speculate that it’s a possibility that hosts select which specific phage controls a specific type of bacteria by fitting mucins with certain sugars that those phages will be able to recognize. The hope is that in the future these findings will be able to lead to the designing of mucus compatible phages that could fight infections as well as alter the body’s microbial balance.