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  • Back in 1862, soldiers fighting in the American Civil War noticed something odd:

  • Some of the injured had wounds that glowed blue -- and those who did, seemed to be more

  • likely to survive.

  • They called this weird light the Angel's Glow, and figured that it must be a sign of

  • supernatural protection.

  • And for more than a hundred years, nobody knew what caused it -- until a pair of high

  • school scientists figured it out:

  • The soldiers with glowing wounds were being protected by bacteria.

  • The American Civil War was a pretty rough place to be.

  • New developments in weaponry made the battles especially bloody and brutal, resulting in

  • extremely high numbers of casualties on both sides of the conflict.

  • The Battle of Shiloh was a particularly awful place to be -- when the battlefields cleared

  • after two days of fighting, more than 23,000 people had been injured or killed, making

  • it the bloodiest battle in American history until that point.

  • The medics on both sides weren't prepared to deal with so many injuries, so many wounded

  • soldiers had to wait for days before they received medical attention.

  • And as night fell on the first evening, some soldiers were surprised to discover that their

  • wounds were glowing with a soft blue light.

  • It turned out that those soldiers whose wounds had glowed in the dark were more likely to

  • survive, and their injuries healed more cleanly than those who didn't -- almost as if the

  • blue light were protecting the soldiers who had it.

  • In 2001, a 17-year-old named Bill Martin learned about the Angel's Glow and immediately thought

  • of his mother's research on glowing bacteria for the US Department of Agriculture.

  • Phyllis Martin was studying a type of bioluminescent bacteria known as Photorhabdus luminescens,

  • which is found in soil and glows a pale blue.

  • So Bill, along with his friend John Curtis, decided to see if the blue glow of the soldier's

  • wounds could be related to the blue glow of the bacteria.

  • They knew that P. luminescens has a mutualistic relationship -- in other words, one that benefits

  • both species -- with a roundworm, or nematode.

  • But the worms have another important relationship in their lives -- they're parasites of some

  • insects.

  • When these roundworms infect an insect, they spit up any P. luminescens that the insect

  • happens to have in its guts.

  • Then, the bacteria release toxins that kill the insect and enzymes that break down tissue.

  • So both the worm and the bacteria get a tasty dinner.

  • The duo took their project to the lab, where they examined strains of the bacteria under

  • different environmental conditions to figure out what suited them best.

  • When they compared those results to the conditions described in historical records of the Battle

  • of Shiloh, they found that the soil would have been a great place for both the bacteria

  • and the worms to thrive.

  • And if the bacteria were living in soldiers' wounds, that would explain the Angel's Glow

  • -- and why the soldiers who had it were more likely to survive.

  • So here's what they figured happened after the Battle of Shiloh:

  • There would probably have been insects on or near the soldiers' wounds, because they

  • were outdoors in a battlefield.

  • When nematodes infected those insects, P. luminescens would have released the toxins

  • that normally help kill the insects.

  • But in this case, those compounds would also have helped kill off other, more dangerous

  • bacteria, protecting the soldiers from infection.

  • Then, the worms would have moved on in search of their next meal.

  • And that whole time, the P. luminescens would be glowing, giving off a faint, ghostly blue

  • light.

  • So, it seemed like Martin and Curtis had solved the mystery.

  • But there was one more wrinkle to iron out:

  • Normal human body temperatures are too hot for P. luminescens.

  • So how could the bacteria be living in the soldiers' wounds?

  • After some more thinking, though, the pair came up with an answer.

  • The battle occurred in early April in Tennessee, where it would have pretty chilly at night.

  • The wounded soldiers would have been sitting on the cold, damp ground, waiting for medical

  • care.

  • Under those conditions, it wouldn't take long for hypothermia to set in -- and the

  • soldiers' lowered body temperature would have been just cool enough for P. luminescens

  • to do their thing.

  • Then, once the soldiers were found and brought indoors for care, their bodies would warm

  • back up again, killing off the P. luminescens before they could spread far enough to become

  • dangerous.

  • These experiments and conclusions earned Bill Martin and John Curtis the top prize in the

  • 2001 Intel International Science and Engineering Fair.

  • By combining their knowledge of history and microbiology, and trying a few experiments

  • of their own, they solved the 139-year-old mystery of the Angel's Glow.

  • Thanks for watching this episode of SciShow, which was brought to you by our patrons on

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Back in 1862, soldiers fighting in the American Civil War noticed something odd:


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B2 中高級 美國腔

拯救生命的奇怪的蓝色光芒(The Strange Blue Glow That Saved Lives)

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    joey joey 發佈於 2021 年 05 月 19 日