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Title: Microbe With Bizarrely Tiny Genome May Be Evolving Into a Virus

Link: https://science.slashdot.org/story/25/06/17/0...

sciencehabit shares a report from Science.org: The newly discovered microbe
provisionally known as Sukunaarchaeum isn't a virus. But like viruses, it
seemingly has one purpose: to make more of itself. As far as scientists can
tell from its genome -- the only evidence of its existence so far -- it's a
parasite that provides nothing to the single-celled creature it calls home.
Most of Sukunaarchaeum's mere 189 protein-coding genes are focused on
replicating its own genome; it must steal everything else it needs from its
host Citharistes regius, a dinoflagellate that lives in ocean waters all over
the world. Adding to the mystery of the microbe, some of its sequences
identify it as archaeon, a lineage of simple cellular organisms more closely
related to complex organisms like us than to bacteria like Escherichia coli.
The discovery of Sukunaarchaeum's bizarrely viruslike way of living, reported
last month in a bioRxiv preprint, "challenges the boundaries between cellular
life and viruses," says Kate Adamala, a synthetic biologist at the University
of Minnesota Twin Cities who was not involved in the work. "This organism
might be a fascinating living fossil -- an evolutionary waypoint that managed
to hang on." Adamala adds that if Sukunaarchaeum really does represent a
microbe on its way to becoming a virus, it could teach scientists about how
viruses evolved in the first place. "Most of the greatest transitions in
evolution didn't leave a fossil record, making it very difficult to figure
out what were the exact steps," she says. "We can poke at existing
biochemistry to try to reconstitute the ancestral forms -- or sometimes we
get a gift from nature, in the form of a surviving evolutionary
intermediate." What's already clear: Sukunaarchaeum is not alone. When team
leader Takuro Nakayama, an evolutionary microbiologist at Tsukuba, and his
colleagues sifted through publicly available DNA sequences extracted from
seawater all over the world, they found many sequences similar to those of
Sukunaarchaeum. "That's when we realized that we had not just found a single
strange organism, but had uncovered the first complete genome of a large,
previously unknown archaeal lineage," Nakayama says.

Read more of this story at Slashdot.

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