2023-11-18 12:00:00
This is the first time this viral behavior has been observed. Rory Morrow Meteored United Kingdom 18/11/2023 13:00 4 min
For the first time, scientists have observed unusual behavior in some viruses, where one attaches itself to anotherlike a vampire, in order to replicate itself.
These viral relationships, in which one virus (the satellite) depends on a second virus (the helper) to complete its life cycle, have been known for some time. But so far, no one had ever seen a satellite virus physically attach itself to its unwitting partner.
This behavior was observed in a type of bacteriophage – a virus that infects bacteria – that systematically attaches itself to another bacteriophage at its “neck,” where the main body of the virus attaches to the tail. The researchers detail their results in a new study published in the Journal of Microbial Ecology.
“When I saw it, I said to myself: I can’t believe it” said Tagide deCarvalho, lead author of the study and researcher at the University of Maryland, Baltimore County (UMBC). “No one has ever seen one bacteriophage – or any other virus – attach itself to another virus.”
Satellite bites
These “vampire viruses”, as they have of course been nicknamed, have been discovered quite by chance in a student’s bacteriophage sample sent to the University of Pittsburgh sequencing laboratory.
In addition to containing a large genetic sequence of the expected bacteriophage, the sample also contained something smaller, which didn’t match anything the researchers knew. It wasn’t until the team brought in deCarvalho and a transmission electron microscope that they realized what was happening.
Most satellite viruses have a special gene that allows them to integrate into the DNA of the host cells they enter – bacterial cells, for example. They still need a helper virusbut they only need it to be elsewhere in the same cell, the study authors explain.
Satellite bacteriophage (left) attached to the larger helper bacteriophage (right). Photo credit: Tagide deCarvalho/UMBC.
But the satellite virus discovered during their research does not have this gene. As it cannot therefore integrate into the DNA of the host cell, it must be close to its assistant when it enters the cell to survive.
“Attachment now made perfect sense,” said Ivan Erill, co-author and professor of biological sciences at UMBC, “because how else are you going to guarantee that you get into the cell at the same time?”
A timeless relationship
Researchers found 80% of assistants had satellites attached to their necksand those that did not often showed evidence of previous attachments in the form of remaining tendrils, which Erill described as resembling bite marks.
Furthermore, they discovered that these two viruses co-evolved over a long period of nearly 100 million years. This suggests that there may well be many more such cases yet to be discovered. The team hopes to explore this in future research, while also studying how exactly the satellite virus attaches itself to its helper.
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