Sticky bacteriophage protect animal cells

For decades, biologists have discussed and experimented with bacterial viruses, called phage, as a means of treating bacterial infections (1, 2). Remarkably, our own evolution may have beaten us to it. In PNAS, Barr et al. present a compelling and unique hypothesis that animal cells use phage as weapons against bacterial pathogens (3). Animal cells ranging from cnidarian (coral) to human excrete mucus to protect themselves from their external environment. Barr et al. propose a unique function for mucus, to trap phage to intersect and destroy invading bacteria before they reach the mucus-encapsulated tissue. This hypothesis (termed BAM for bacteriophage adhering to mucus) suggests a unique component of the animal immune system governed by a cross-kingdom animal-phage mutualism.

The BAM model proposed by Barr et al. (3) is as follows: (i) Animal epithelial cells secrete mucus that is rich with mucin glycoproteins, which work like Velcro. These proteins have a unique structure that incorporates hundreds of negatively charged glycan chains, which extend nanometers into the surrounding environment (4). (ii) The other side of the Velcro is the bacteriophage capsid, which has an Ig-like protein domain that interacts with the glycoproteins. The …

↵¹E-mail: justin.raymond.meyer{at}gmail.com.