Further to questions around animal, plant, and bacterial communication:
Sorek and his colleagues had found phages actively discussing their choices. They realized that as a phage infects a cell, it releases a tiny protein — a peptide just six amino acids long — that serves as a message to its brethren: “I’ve taken a victim”. As the phages infect more cells, the message gets louder, signalling that uninfected hosts are becoming scarce. Phages then put a halt to lysis — the process of replicating and breaking out of their hosts — instead staying hidden in a sluggish state called lysogeny1.
The viruses, it turns out, did not depend on bacterial cues to make their decisions. They controlled their own destiny. “This finding was a big, important, revolutionary concept in virology,” says Wei Cheng, a structural microbiologist at Sichuan University in Chengdu, China.
Sorek named this viral peptide ‘arbitrium’, after the Latin word for decision. It seemed to work much like the communication system used by bacteria — quorum sensing — to share information about cell density and adjust the population accordingly. Yet it was the first time anyone had demonstrated molecular messaging of this kind in viruses. And it fitted into an emerging picture of viruses as much more sophisticated social agents than scientists had given them credit for.Elie Dolgin, “The secret social lives of viruses” at Nature
Do viruses think? Not in the human sense. As with plants, these communications are signals, not abstractions.
But the signals raise an important question: If viruses seek to remain in an organized state, why are they not “alive”? If they are not “alive,” what are they?
See also: Life forms have a story but rocks don’t. Talbott: An animal’s end-directed activity may, of course, be very far from what we humans know as conscious aiming at a goal. But all such activity nevertheless displays certain common features distinguishing it from inanimate proceedings
Can plants be as smart as animals?
Before you go: One way viruses get spread “never should have evolved”
Reset! Different segs of virus genome can exist in different cells but work together
Viruses devolve. (PaV)
Virus expert highlights the conflict over whether viruses are alive In short, it is an open question. The question relates to the role viruses can play in evolution, among other things. Are they precursors of life, detritus of life, or something in between? Or all three? Keep the file open.
Viruses invent their own genes? Then what is left of Darwinism?
Why viruses are not considered to be alive
Another stab at whether viruses are alive
Phil Sci journal: Special section on understanding viruses
Should NASA look for viruses in space? Actually, it’s not clear that RNA came first. Nor is it clear that viruses precede life. A good case can doubtless be made for viruses being part of the scrap heap of existing life. But no matter. If you think you can find viruses in space, boldly go.
Why “evolution” is changing? Consider viruses
The Scientist asks, Should giant viruses be the fourth domain of life? Eukaryotes, prokaryotes, archaea… and viruses?
Are viruses nature’s perfect machine? Or alive?
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