2023-11-23 18:19:02
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Researcher in a laboratory looks into the microscope (symbolic image). © Matej Kastelic/Imago
A small virus holds on to the “neck” of a larger virus – and thus compensates for an ability that it itself has lost. Researchers are surprised.
In March 2020, Tagide deCarvalho saw something truly strange – something she says no other scientist has ever seen before: a virus with another, smaller virus clinging to its “neck.” The backstory of this viral attachment is like a master class in how wild and strange biology can be.
The two microbes are bacteriophages, viruses that infect bacteria, and were recovered from a clod of soil in Poolesville, Md. Bacteriophages, also simply called phages, are among the most common organisms on Earth. Millions of them can occur in one gram of soil.
But with a special microscope that uses an electron beam to capture images, deCarvalho witnessed a truly bizarre moment – much like a wildlife photographer capturing animal behavior no one expected.
“I might see that literally hundreds of them had this little guy on their necks, and that was clearly not a coincidence,” said deCarvalho, who directs the Keith R. Porter Imaging Facility at the University of Maryland in Baltimore County. “We know that viruses can do some amazing, interesting things. But this is just another new thing that no one might have predicted.”
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In a recent Journal of the International Society for Microbial Ecology published study deCarvalho and his colleagues explain how the strange pair of viruses probably came regarding. The small virus, called MiniFlayer, has lost the ability to make copies of itself inside cells, as is common when viruses reproduce. So evolution came up with a clever, parasitic solution. MiniFlayer takes advantage of another virus, called MindFlayer, by clinging to its neck, and when they enter cells together, MiniFlayer uses its partner’s genetic machinery to reproduce.
Is it a hug? A chokehold? DeCarvalho compares the relationship to viral hitching. Her colleague Ivan Erill, a computational biologist at UMBC, compares it to a vampire sinking its teeth into its prey. It’s not a perfect analogy, but he notes that sometimes when they find MindFlayer alone, they find “bite marks” where MiniFlayer’s tendrils were attached.
“Viruses are capable of anything. They are nature’s most creative force,” says Erill. “If something is possible, they will find a way to do it. But no one expected them to do something like this.”
The strange universe of viruses
The discovery began with a lecture designed to teach students basic laboratory techniques by asking them to isolate phages from soil samples and study them using genetics. DeCarvalho has been working with the program for seven years and says that for many students, seeing the phages is an exciting moment, similar to when expectant parents see an ultrasound image of a fetus for the first time.
Bacteriophages (symbolic image). © Westend61/Imago
In this case, students Jenell Lewis and Hira Ahmed isolated and named their phage MindFlayer in 2019. However, genome sequencing revealed puzzling results that suggested some type of contamination. When deCarvalho looked at the phage under the microscope, she noticed not one, but two phages.
The “virosphere,” as scientists call the strange universe of viruses, is known to contain elements called “satellites” that have lost their ability to replicate in cells. Normally, the satellites overcome this deficiency by integrating into the genome of the cells they infect. There they lurk until another virus, a “helper” that has the missing components, accidentally penetrates the cell. The satellites then take the opportunity to make copies of themselves.
MiniFlayer is a satellite, but unlike the typical version, it does not have the ability to hide in cells. This presents him with a puzzle: How can he ensure that he ends up in the cell at the same time as his helper?
“This virus said: Okay, I will attach myself to my helper, hang on his neck – and travel with my helper until we find a new cell,” says Erill.
In microbiology, molecular piracy and hijacking have been refined
This is common practice in microbiology, where tactics like molecular piracy and hijacking have been refined over millions of years of evolution. Bacteria are vastly outnumbered by their viral enemies, so they are in a constant evolutionary arms race. Bacteria develop defense mechanisms and viral phages develop counter-defense strategies. Phages parasitize other phages.
Researchers are interested in using phages, the natural predators of bacteria, as medicine. Phage therapy can be used to fight harmful infections – an approach that might become more important as antibiotic-resistant bacteria have become a growing threat.
Terje Dokland, a professor of microbiology at the University of Alabama at Birmingham who was not involved in the study, called the observation of the two phages sticking together “intriguing” but called for more images and studies to draw more precise conclusions regarding the interaction and find out whether the two viruses actually infect cells together.
The authors hope to collaborate with groups that use another form of electron microscopy to better understand what’s going on. Unlike a vampire, deCarvalho says, the MiniFlayer doesn’t suck anything out of the MindFlayer.
“We don’t know whether the satellite injects its DNA into the helper or whether it just goes along for the ride and then falls off, like a tick,” said deCarvalho. “Hopefully someone else will take up this work and clarify this really interesting question.”
About the author
Carolyn Johnson is a science reporter. She previously covered health care and health care affordability for consumers.
We are currently testing machine translations. This article was automatically translated from English into German.
This article was first published in English on November 14, 2023 at the “Washingtonpost.com“ was published – as part of a cooperation, it is now also available in translation to readers of the IPPEN.MEDIA portals.
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