For billions of years, virus and bacteria were locked in an endless arms race, and this evolved a predator “a monster of a tail”.
The unique devourer of bacteria virusor bacteriophage, is officially named P74-26, although it is more colloquially known as “Rapunzel” virus.
Like the absurdly long curls of the fairytale princess, the pathogen’s “ponytail” stands out in a crowd of her peers.
At nearly a micrometer long, the appendix is 10 times longer than most other bacteriophages.
In fact, he has the longest tail of any known virus and, curiously, the most stable too.
According to new research, this impressive appendage is likely what allows Rapunzel virus to find and break through one of the toughest bacteria on Earth and in one of the most inhospitable environments.
In bubbling hot springs that reach temperatures well over 77°C (170°F), Rapunzel virus lives by infecting bacteria Thermus thermophilus and use the machinery of the other cell to reproduce and multiply.
Assembling many images from the virus‘s tail at various points in its construction, scientists have been able to unravel its unique structure. Computer simulations explained in more detail the “highly intertwined web of interactions” that coordinate to build this impressively long probe.
“We used a technique called cryo-electron microscopy, which is a huge microscope that allows us to take thousands of images and short films at very high magnification,” explain microbiologist Emily Agnello of the University of Massachusetts Chan Medical School (UMass).
“By taking many pictures of the phage’s tail tubes and stacking them together, we were able to figure out exactly how the building blocks fit together.”
Bacteriophage tails come in a variety of lengths and styles: some long, some elastic, some short, and some stiff. These molecular “machines” have evolved to recognize specific bacterial host cells before penetrating them and then delivering their genome to the cytoplasm for replication.
Given the locked-in nature of this attack, there is a great diversity of tails among bacteriophages, found in virtually every habitat on Earth. But exactly how do these tails differ?
To date, scientists have characterized very few phage-host interactions, and now that antibiotic resistance is a growing threat to human health, experts are turn to phages for ideas on how to defeat superbugs.
For example, Rapunzel virusThe tail of seems to be such a threat to bacteria because of the way its building blocks interlock and stack together.
Despite its size, the virusThe tail relies on half the number of building blocks as other bacteriophages, say the researchers, and that seems to make all the difference.
“We think what happened is that some former virus merged its building blocks into a single protein,” said UMass biochemist Brian Kelch.
“Imagine two small Lego bricks being fused together into one large brick with no seams. This long tail is constructed with larger, sturdier building blocks. We believe this could stabilize the tail at high temperatures.”
These heavy-duty subunits stack with a “ball and socket” type mechanism similar to Lego bricks, which have one side studded and the other pocketed.
In viruses, each of these building blocks is a kind of ring shape, which means that the whole tail forms a hollow tube when completed. It is the channel along which virus sends its genome once it has entered a bacterial cell.
“Our research reveals that these building blocks can change shape, or conformation, as they come together,” said Agello.
“This shape-shifting behavior is important to allow the building blocks to fit together and form the correct tail tube structure.”
Rapunzel virus the tail is exceptionally long, which seems to give it extra power to latch on and penetrate bacteria. At the same time, however, this length means there is a higher chance of the tail assembly going bad.
The researchers think there must be internal mechanisms that keep the developing tail on track, and these mechanisms are likely shared with other phages.
Understanding how they work could one day help scientists create better treatments in the fight against deadly bacteria.
“I believe that studying unique and interesting things can lead to discoveries and applications that we can’t even imagine yet.” said Agello.
Now that they know how virus‘ tail shape, researchers are considering genetically modifying its length to see how this might alter its interactions with bacteria.
No matter the outcome, these experiments will certainly teach us something new.
The study was published in the Review of Biological Chemistry.