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This week, scientists turned to an unlikely source to try to solve the problem of antibiotic resistance, and got a peek at the lifestyle of some of the very first mammals... by studying their teeth.

Hosted by: Michael Aranda

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Sources:
Nobels:
https://www.nobelprize.org/prizes/physics/2020/press-release/
https://www.nobelprize.org/prizes/chemistry/2020/press-release/
https://www.nobelprize.org/prizes/medicine/2020/summary/

Wasps:
https://www.pnas.org/content/early/2020/10/07/2012379117
https://www.eurekalert.org/emb_releases/2020-10/uops-pms100920.php
https://www.who.int/news-room/fact-sheets/detail/antibiotic-resistance

Mammals:
http://dx.doi.org/10.1038/s41467-020-18898-4
https://www.eurekalert.org/emb_releases/2020-10/uob-att100820.php
https://www.britannica.com/science/cementum
https://www.britannica.com/animal/Morganucodon
https://www.britannica.com/animal/reptile/Growth-and-longevity

Image Sources:
https://commons.wikimedia.org/wiki/File:HCV_EM_picture_2.png
https://commons.wikimedia.org/wiki/File:Vespula_flaviceps.jpg
https://www.nature.com/articles/s41467-020-18898-4#rightslink
https://commons.wikimedia.org/wiki/File:Human_tooth_diagram-en.svg
https://commons.wikimedia.org/wiki/File:Morganucodon.jpg
[♪ INTRO].

Last week was Nobel Prize week in the world of science. The prize in physics was awarded for pioneering work on the existence of black holes and the discovery of a supermassive black hole at the center of the Milky Way.

Check out our Space channel today for more on that one. The chemistry prize was given for the invention of CRISPR, a gene-editing technique that’s already revolutionizing medicine and basic science research. And the prize in medicine was awarded for the discovery of the viral infection Hepatitis-C.

But plenty of coverage has been devoted to those already, so let’s turn to this week’s science news. Like, say, getting yourself injected with essence of wasp venom. On purpose, even.

This scary-sounding treatment is the aim of work published this week in the Proceedings of the National Academy of Sciences. The researchers were looking for a solution to one of the thorniest problems in modern medicine: antibiotic resistance. Our use—and sometimes overuse—of antibiotics has led to an alarming increase in the number of bacteria that can survive treatment with drugs that previously would have eliminated them.

In the US alone, as many as 35,000 people die each year after getting infected by these strains. Scientists are now on the lookout for new methods to kill these bacteria, which brings us to wasp venom. In particular, a certain protein found in the venom of the.

Korean yellow-jacket wasp, called mastoparan-L, or mast-L for short. Mast-L has two closely related properties: it’s reasonably good at killing bacteria, just like some antibiotics. But it’s also pretty toxic to humans, which is why it’s no fun getting stung.

In a small dose the size of a wasp sting, mast-L isn’t usually life-threatening. But if you were to administer enough of it to treat a bacterial infection, that could be a problem for a patient. So the researchers did a bit of cut-and-paste with the sequence of mast-L.

Searching a database of known antimicrobial protein sequences, they identified a short sequence that seemed especially good at targeting bacteria. Then they imported that sequence into mast-L, pasting it right into the sequence thought to be most toxic to humans. The end result is a new protein, called mast-MO, with enhanced bacteria-fighting properties and less of the stuff that’s bad for humans.

To test out their new antibacterial protein, the team infected mice with bacteria known to cause sepsis, an intense infection thought to be responsible for as much as 20% of all deaths on Earth. Hours later, they injected one batch of mice with the new, improved mast-MO and another with vanilla mast-L. Overall, across a few different trials, more of the mice treated with mast-MO survived than those treated with mast-L.

The unmodified mast-L subjects also suffered from serious toxicity-related side effects that the mast-MO mice did not. So how does mast-MO work? It seems to poke holes in the cell membranes of bacteria -- which is bad for them.

It also means that, if you inject a regular antibiotic at the same time, more of it can get inside each cell -- enhancing its effect. Mast-MO also seems to attract more white blood cells to fight the infection, without causing a reaction so large that it creates other dangerous side effects. The end result was an overall health benefit similar to the kinds of traditional antibiotics doctors are now needing to supplement.

Will this work in humans? Only clinical trials can tell us. But these results are promising enough that the team is already looking at other venoms that might have similar properties.

So… thank you, wasps! Seriously. That wasn’t the only news in the world of biology this week.

We also got a peek at the lifestyle of some of the very first mammals -- ones that lived among the dinosaurs 200 million years ago. In a study published in the journal Nature Communications, researchers propose that two early mammalian species probably behaved a lot more like modern reptiles than the rodents we know today. Basically, they lived slow and died old.

These conclusions were based on an unlikely source: the animals’ teeth. Specifically, tiny layers deposited at the tooth’s base. Teeth are held in place within the mouth by a bone-like substance called cementum.

Unlike the rest of the tooth, which remains basically unchanged, cementum is deposited throughout a creature’s life. The rate ebbs and flows for various reasons throughout the animal’s life, including the changing of the seasons. That means that, just like the rings of a tree, layers of cementum can be counted to determine an animal’s approximate age at death.

To get at the layers in fossilized teeth the size of a pinhead, the team basically x-rayed them using some of the world’s most powerful x-ray emitters. After x-raying 200 teeth and counting the rings within each, they estimated the lifespans of two early rodent-sized mammals. One species lived on average 14 years, while the other lived around nine.

Compare that to an average of one or two years for modern mice and shrews. What’s more, when they looked at the thigh bones belonging to one of the species, they found evidence that the creatures had very narrow blood vessels. Without a lot of blood flow, these first mammals probably couldn’t sustain the all-day activity that’s characteristic of their modern cousins.

Taken together, these low rates of activity—and relatively long lives—are more reminiscent of today’s reptiles than modern rodents. And it kind of makes sense: in a world dominated by dinosaurs, hanging out under a rock might’ve been the only path available to living a nice, long life. Thanks for watching this episode of SciShow News, which was supported by our patrons.

Not only do our patrons help us bring free science content to everyone. They’re also the coolest people in any room they walk into. We’re sure of it.

If you’d like to get involved, check out patreon.com/scishow. [♪ OUTRO].