Bush of life: giant virus DNA hiding in Algae (Introduction)

by David Turell , Wednesday, April 10, 2024, 16:17 (20 days ago) @ David Turell

A new discovery:

https://www.science.org/content/article/giant-viruses-played-key-role-early-life-study-...

"The seething, microbe-rich hot springs of Yellowstone National Park are a model of the conditions in which life emerged on early Earth, many researchers think. Now, a study of one Yellowstone hot spring suggests so-called “giant viruses” played a key role in those primordial ecosystems and may have helped drive early steps in evolution.

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"Giant viruses have amazed biologists since their discovery in 2003. They can be larger than some bacteria, their genomes are many times bigger than those of most viruses, and they have some characteristics of bacteria and other cellular forms of life. Biologists have found giant viruses in the deep sea and hiding in the genomes of red algae. They also inhabit hot springs—places Andreas Weber, a biochemist at Heinrich Heine University Düsseldorf, calls “time capsules that provide a window into early eukaryotic life.”

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"From that harvest, postdoc Felipe Benites culled all known sequences from archaea, algae, and bacteria. That left him with DNA from about 3700 potential viruses; surprisingly, almost two-thirds of them were giant viruses. Using further computer analysis, Benite and his colleagues were able to piece together most of the genomes of about 25 different types of viruses. They think these reproduce by infecting the red algae.

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"Because hot springs come and go over geological time, the researchers assumed none of the giant viruses would be very old; they thought new viruses moved in from cooler environments and adapted to high temperatures every time a hot spring appeared somewhere. But their biomolecules told a different story. “The connections between the viruses and [their hosts] are ancient,” Bhattacharya says.

"For one, viral proteins bore the hallmarks of a longtime hot spring dweller: They tended to have shorter loops and be more tightly packed than proteins adapted to milder conditions. Moreover, their DNA was “biased” to have the same three-base codes that other hot spring inhabitants have. And when the researchers reconstructed a viral family tree based on the newly sequenced viruses and other viral genes, they concluded that the hot spring viruses branched off very early in viral history. Their association with red algae likely dates back 1.5 billion years, the team reports.

“'This work supports the concept that viruses are present wherever cellular life exists, that viruses have existed at least as long as cellular life,” says Mark Young, an environmental virologist emeritus at Montana State University who was not involved with the work.

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"Bhattacharya suspects the viruses may have been important in another way: As they infected algal cells, they caused them to break apart, making their contents available for other cells to grow in an environment where nutrients were scarce.

"The researchers made another surprising discovery: The viral communities on the algal mat, in the soil, and between the rocks were surprisingly different. “I would have thought that there would be more exchange between neighboring sites that are sometimes only a few centimeters apart,” Weber says. How and why these communities stay so isolated is another mystery, Young says—which “points out how little we really know about the diversity and role of viruses in microbial communities.'”

Comment: from my view of purpose acting in evolution, all forms of life that are here play a necessary role.