ananyo writes: Researchers have discovered that animal mucus â" whether from humans, fish or corals â" is loaded with bacteria-killing viruses called phages. These protect their hosts from infection by destroying incoming bacteria. In return, the phages are exposed to a steady torrent of microbes in which to reproduce. Mucus mainly consists of huge molecular complexes called mucins, which are made up of thousands of glycan sugars attached to a central protein backbone. The team showed that phages stick to these sugars, reducing the number of bacteria that can attach to mucus by more than 10,000 times.