Coming of Phage
Everything you’ve been taught about phage is wrong. Well, maybe not everything. Heck, maybe you’ve never been taught anything about phage in the first place! But if you’ve ever encountered a story about this family of bacteria-infecting viruses, I’m willing to bet it included a picture much like this:
That geometric lunar lander is the standard illustration of phage such as T7. It looks exotic and alien, a freakish example of biological symmetry, but it’s pretty true to the actual biology: The icosahedral protein head, the protruding neck that it uses to pierce the membrane of its victim so that it can inject its genetic material … and the legs.
Wait a sec, those legs need revising. Some really cool new research by Ian Molineux (who taught my graduate school molecular bio class, btw) says that all those “legs-out”, moon lander drawings of phage probably aren’t right.
In the video above you see that, according to the electron imagery they report in their Science paper, those legs stay tucked up next to the body for most of the free-floating life of the phage. It sort of drags one or two along, waiting to hook onto an appropriate bacterium that it can infect, at which point it extends the rest of the legs to go into full infection mode. To give you an idea of how hard this was to observe, a single phage is only around 20-30 nanometers wide, which means you could fit about 4,000 of them across the width of a single human hair!
It might seem like a small, ho-hum tidbit of research at first, since who really cares about a virus that infects bacteria? But phage are incredibly important. Phage have driven a great deal of the evolution of life on Earth. They are vehicles of gene swapping that have allowed genomes to expand and become more complex. They are veterans of 70+ years of biology research, from back when we first identified DNA as a genetic material to today’s exotic synthetic biology applications. A great deal of what we know about molecular genetics is because of these little guys, and we’re still making the most basic discoveries as to how they function.
Never let anyone tell you that there’s nothing left to discover! We have scarcely begun to fill in the colors, even for the most basic parts of biology’s palette.