Tag: virus

Virus Social Evolution

Another aspect of social evolution of viruses that Sanjuán is investigating is why multiple viral particles sometimes gather and infect a cell together. The trade-off is that, if the viral particles assemble, there are fewer units to infect different cells. So “in principle, this is costly because it limits diffusion capability”. But his team found that the aggregated viruses grow faster and produce more progeny. This result was dependent on cell type: In tumor cells that have no innate immunity, being aggregated was costly. But in normal cells, which do mount an innate immune response, being aggregated was beneficial for the viruses because it allows the viruses to overwhelm the innate immune response

1918 Flu

The Spanish flu strain killed its victims with a swiftness never seen before. In the United States stories abounded of people waking up sick and dying on their way to work. The symptoms were gruesome: Sufferers would develop a fever and become short of breath. Lack of oxygen meant their faces appeared tinged with blue. Hemorrhages filled the lungs with blood and caused catastrophic vomiting and nosebleeds, with victims drowning in their own fluids. Unlike so many strains of influenza before it, Spanish flu attacked not only the very young and the very old, but also healthy adults between the ages of 20 and 40.

2020-03-01:

In most disasters, people come together, help each other, as we saw recently with Hurricanes Harvey and Irma. But in 1918, without leadership, without the truth, trust evaporated. And people looked after only themselves.

When the Next Plague Hits

Despite advances in antibiotics and vaccines, and the successful eradication of smallpox, Homo sapiens is still locked in the same epic battle with viruses and other pathogens that we’ve been fighting since the beginning of our history. When cities first arose, diseases laid them low, a process repeated over and over for millennia. When Europeans colonized the Americas, smallpox followed. When soldiers fought in the first global war, influenza hitched a ride, and found new opportunities in the unprecedented scale of the conflict. Down through the centuries, diseases have always excelled at exploiting flux.

Thawing Diseases

In August 2016, in a remote corner of Siberian tundra called the Yamal Peninsula in the Arctic Circle, a 12-year-old boy died and at least 20 people were hospitalized after being infected by anthrax. The theory is that, over 75 years ago, a reindeer infected with anthrax died and it’s frozen carcass became trapped under a layer of frozen soil, known as permafrost. There it stayed until a heatwave in the summer of 2016, when the permafrost thawed.

Eukaryogenesis

Genetic analysis places Loki squarely within the single-celled archaea. But it possesses an intriguing collection of genes that look as though they would be more at home in eukaryotes, rather like modern words dotting a medieval manuscript. In fact, Loki’s genetic machinery suggests that the organism might be able to engulf other cells, the first step in the creation of mitochondria. Even if Loki doesn’t solve the mystery of our ancient origins, its discovery shows just how much biological diversity remains to be unearthed. Perhaps the next discovery will be a eukaryote with no history of possessing mitochondria. Or perhaps it will be an archaeon with signs of a symbiotic bacterium living within.

2020-11-25: Viral nucleus origin?

A trove of giant viruses was recently sequenced from the very same deep-sea sediments where Lokiarchaeota were discovered. He hopes someone will test whether any of these viruses can infect archaea and, if so, whether they build viral factories similar to those made by the NCLDVs that infect eukaryotes. Demonstrating that would be “game over.”

2022-11-12: Syntropic eukaryogenesis

Today, at the microbial mats in the Atacama Desert and other sites throughout the world, scientists are investigating what the earliest eukaryotic cells may have looked like, the partnerships they may have struck up with other organisms, and how their molecular machinery might have functioned and evolved. Already, the discovery of the Asgards has solidified certain aspects of eukaryogenesis while raising new questions about others. “I think this is the most exciting development in biology right now. So much is being discovered and so many predictions are being met. Eukaryogenesis is arguably one of the most important events in the history of life, after the origin of life itself.” Many scientists have rallied behind the idea that the first eukaryotes evolved out of a syntrophy between an archaeal host and bacteria that somehow found their way inside to become the organelles, such as nuclei and mitochondria, that distinguish eukaryotes. The details of these relationships remain murky, but mitochondria provide the most tantalizing clues to their origin story. “There’s DNA in mitochondria that we can somewhat clearly connect or trace back to alphaproteobacteria”. There are contrasting hypotheses as to how the alphaproteobacterium would have gotten inside an archaeal host, however. In the eukaryogenesis version of the chicken-and-egg conundrum, scientists go back and forth on whether mitochondria would have been necessary to power the energetically expensive process of phagocytosis, or whether phagocytosis would have had to arise first as the means of ingesting the symbiotic partner. When it comes to the nucleus, the picture is much less clear. Hypotheses of its origin run the gamut from a bacterial endosymbiont within an amoeboid host to the remnants of a giant virus.


2023-06-19: Lokiarchaeota aren’t the the origin of eukaryotes, but are closely related.

Eukaryotes are placed as a well-nested clade within Asgard archaea and as a sister lineage to Hodarchaeales, a newly proposed order within Heimdallarchaeia, consistent with the 2 domain tree of life scenario. Using sophisticated gene tree and species tree reconciliation approaches, we show that analogous to the evolution of eukaryotic genomes, genome evolution in Asgard archaea involved significantly more gene duplication and fewer gene loss events compared with other archaea. Finally, we infer that the last common ancestor of Asgard archaea was probably a thermophilic chemolithotroph and that the lineage from which eukaryotes evolved adapted to mesophilic conditions and acquired the genetic potential to support a heterotrophic lifestyle.

Viruses may be alive

Less than 4900 viruses have been identified and sequenced so far, even though scientists estimate there are more than 1M viral species. viruses originated from multiple ancient cells and co-existed with the ancestors of modern cells. not long after modern cellular life emerged, most viruses gained the ability to encapsulate themselves in protein coats that protected their genetic payloads, enabling them to spend part of their lifecycle outside of host cells and spread

Human Virome

a new method that uses this phage mixture to test blood samples for over 200 species and 1000 strains of virus at a time. The team speculates that their technique, named VirScan (VEERscan), could one day become a near-universal test for viral infections using just one drop of a patient’s blood, replacing one-off tests for specific types of virus. Very common infections, like rhinoviruses and herpesviruses, come up regularly in VirScan, while more exotic viruses are found rarely if at all. “Sure enough, for many common viral infections we’re detecting them at pretty high levels. And for some viruses like CMV [one of the herpesviruses], which is known to infect 50% of the population, that is in fact what we saw.” VirScan could be brought into a number of research areas where virome-wide sequencing, or targeted viral tests, have not given us the full picture. Wylie, for instance, is curious what antibodies would be found in a large study of children, a major focus of her own research on the virome. “You’re actually developing your immune repertoire at that time. It would be interesting to see that history of what children had been exposed to, and what might be missing from the common pathogens in a child… We have to realize we’re a bit changed after these exposures, and this is one method of looking broadly at that.” Kula hopes that VirScan can shine a light on mysterious diseases like chronic fatigue syndrome and Kawasaki disease. Some experts suspect these illnesses are caused or exacerbated by viruses, but those suspicions are hard to confirm when no one knows which virus to look for. With VirScan, this is no obstacle.