Discussing quorum sensing does nothing to help us understand what constitutes living, which is what this thread is about.
Thank you James for your patience. I understand your concern and I respect your observation.
Let me assure you that my posts are made in good faith and a sincere desire to contribute to a discussion about life and living things, and at what point an organism may qualify for the title "living thing".
Allow me to explain the possible importance of "quorum sensing" in the "life" of a virus.
After mulling this over, it seems that we can restrict the question of "life and non-life" to single celled, very small (nano-scale) size, bio-chemical patterns. (this realization actually prompted my spontaneous segue)
Bacteria are extremely versatile in their adaptive abilities and feeding range. Bacteria hunt and talk to themselves. Bateria are "alive".
Communication seems to be qualifier for a living organism.
A social bacterium with versatile habits
Many living systems share a fundamental capacity for cooperation. Plants and animals are made up of billions of cells that communicate with one another, carry out specific tasks and share their resources. Many single-celled microorganisms cooperate in similarly versatile ways: they form communities and exchange useful genes and resources among one other.
https://www.sciencedaily.com/releases/2019/03/190322105725.htm
OTOH,
Viruses are very limited in what they can do, due to their, because the are unable to self-replicate and always need a host. Yet they are extremely versatile in their ability to control the host's homeostasis and immunological defenses.
My reference to
quorum sensing was only as it applies to viruses (not bacteria).
The secret social lives of viruses .
Scientists are listening in on the ways viruses communicate and cooperate. Decoding what the microbes are saying could be a boon to human health.
Geneticist Rotem Sorek could see that his bacteria were sick — so far, so good. He had deliberately infected them with a virus to test whether each ailing microbe soldiered on alone or communicated with its allies to fight the attack.
But when he and his team at the Weizmann Institute of Science in Rehovot, Israel, looked into the contents of their flasks, they saw something completely unexpected: the bacteria were silent, and it was the viruses that were chattering away, passing notes to each other in a molecular language only they could understand. They were deciding together when to lie low in the host cell and when to replicate and burst out, in search of new victims.
It was an accidental discovery that would fundamentally change scientists’ understanding of how viruses behave.
Viruses that infect bacteria — spiky lollipop-like creatures known as bacteriophages (or phages) — have surveillance mechanisms that bring them intel on whether to stay dormant or attack, depending on the availability of fresh victims. But researchers long thought these processes were passive; the phages seemed to just sit back and listen in, waiting for bacterial distress signals to reach fever pitch before taking action.
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 lysogeny.
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.
https://www.nature.com/articles/d41586-019-01880-6 (PDF version)
Seems like
bacteriophages (or phages) practise "horticulture" and exert "communal" control over the host cell's mitotic machinery.
Did the discovery of viruses' functional behaviors shift the definition of "life" any ? Should we consider ability to communicate as part of the general definition of a 'living organism?
By that modified standard a virus would be a "living" organism, no?
And that brings my argument full cycle.
p.s. I'll refrain from any further posts in this thread lest I interfere with different perspectives from other posters.