Bacteriophages found in the mucus of a variety of organisms appear to be helping to fend off bacterial invasions of the host, a new study in the Proceedings of the National Academy of Sciences reports. Researchers led by Forest Rohwer at San Diego State University examined how phages adhere to the mucus and infect bacteria there.
The phage-to-bacteria ratio is increased near mucosal surface — in organisms ranging from cnidarians to humans — and cell culture studies indicate that increased numbers of phage in the mucus protects the underlying epithelium from infection, the researchers write. Further, metagenomic analysis, they add, found a number of phage Ig-like protein domains that bind glycan residues of the mucin portion of mucus.
From this, Rohwer and his colleagues suggest a model in which the phage and mucodsal surface have coevolved to promote phage adherence.
This relationship, The Economist notes, "helps the phages, because their bacterial prey also accumulate in mucus, which is thus a rich hunting ground. And it helps the animal host, be that host sea anemone, fish or human being, by stopping any particular bacterial species running out of control."