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  • Humans have mapped nearly all of the land on earth,

  • explored the deepest oceans,

  • stepped foot on the moon,

  • and sent probes to the planets and beyond.

  • But there's a whole world that is left largely unexplored...

  • the microbial world.

  • There's an enormous amount of unidentified microorganisms living

  • within animals, plants, and even our own bodies.

  • Take the human gut for example: only about 50% of the microbes are identifiable.

  • The other 50% don't match to anything that we know about and I would go so far as to

  • say a substantial fraction of that is what we callviral dark matter”.

  • Viral dark matter is the genetic material from viruses that is so different than the

  • sequences of viruses that we know about, that it can't be detected with most conventional methods.

  • In astronomy, dark matter is attributed to certain gravitational observations in the

  • cosmos, like the formation of galaxies.

  • But so far, it can't be detected.

  • And that's a pretty good analogy for what we're studying here right?

  • We can't detect it with any of our reference viruses but we know it exists.

  • We can see it.

  • It has features that are vaguely like a virus.

  • Under a microscope, it looks like a virus, but a closer look at the DNA sequence reveals

  • that it doesn't match anything ever seen before and so scientists can't confirm what

  • it is or what it does.

  • And a lot of it is thought to be yet unidentified viral information.

  • Hundreds of thousands of unknown viruses probably are covering our bodies, in our intestine,

  • on our skin, in our mouth and everywhere else.

  • In fact, viruses are the most abundant biological entity on earth.

  • More than all other organisms combined.

  • But most of them are harmless.

  • Some, called bacteriophages or phages for short, infect bacteria that live in us and

  • can actually be good for your health.

  • In the same way that fluctuating bacterial populations are important for our health and well-being,

  • the viruses that infect those bacteria are of importance as well.

  • And so viruses are undoubtedly essential for life as we know it on the planet and probably

  • for the persistence of human populations.

  • But there are challenges with identifying and even categorizing some of them as viruses.

  • They're so genetically diverse that two similar looking viruses from the same family,

  • might actually have almost nothing in common.

  • There's an interesting term called polyphyletic, which means, for example, children might want

  • to put whales and say fish into the same category.

  • But from the perspective of evolution, it's very clear that say fish and whales represent

  • distinct forms of life that have come to look similar to each other through various sorts of forces.

  • It may very well be that some of these different viral forms of life are not related to each

  • other, in which case even using the word virus to link them all together might in some ways

  • be misclassification.

  • But identifying and classifying this stuff could help us understand the cause of certain

  • cancers, infections, and even prevent a pandemic.

  • We have learned, for example, that a range of cancers are caused by previously unknown

  • transmissible agents, whether it be cervical cancer, the vast majority of which is caused

  • by human human papilloma virus, HPV.

  • It's also the case for certain gastric cancers, stomach cancers.

  • As we start to uncover the diversity of living things that have the potential to infect us,

  • or perhaps even more likely the sort of bacteria that are so profoundly important in our microbiome,

  • we have the capacity of identifying agents that perhaps cause chronic diseases.

  • And that's exactly what researchers at the National Cancer Institute have done.

  • They were able to catalogue thousands of new viruses in hopes of aiding human health.

  • At first, the team sampled humans and animals in hopes of understanding two specific families

  • of viruses that are associated with cancer.

  • But as they isolated these viruses, they uncovered many more DNA sequences that hadn't been

  • recorded beforeviral dark matter.

  • This is kind of where all labs are at this point.

  • We go fishing for the things that we like.

  • And then we get this giant pile of other things.

  • And it's not possible for one person to hand curate 5000 entities.

  • Instead of just ignoring these new DNA sequences, they developed software that makes sharing

  • new viral DNA information easier.

  • Called Cenote-Taker, which is freely available online for others to use, it can automatically

  • annotate virus DNA in a way that's compliant with public databases, making understanding

  • data and sharing findings easier than ever.

  • And now that our tool's available, they can easily take their virus genomes, curate

  • them and annotate them and share them easily with all the other researchers.

  • And so then, God forbid there is another outbreak or pandemic, it's gonna be easy for researchers

  • to find that sequence in humans to know exactly where it was previously... in which animals.

  • We're hoping that basically by rendering the dark matter visible, it just makes it so that

  • if there's a disease association, somebody is going to see it rather than just ignoring it.

  • Although these additional viruses are a small fraction of the millions of unknown viruses

  • that are thought to exist, adding to databases that virologists share is a small step towards

  • preventing and treating health issues.

  • I think it's quite exciting that there is so much that is unknown.

  • Understanding these things has a deep capacity to help us understand our origins, the nature

  • of what life is, the diversity of forms that life can exist in, and to help place us in

  • the broader context of what it means to be alive and what our place in living world

  • really means.

Humans have mapped nearly all of the land on earth,

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あなたの体の中のバイラルダークマター (The Viral Dark Matter Inside Your Body)

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    林宜悉 に公開 2021 年 01 月 14 日
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