The Battle of Shiloh was a devastating Civil War battle in which both sides suffered heavy losses. It’s also known for the strange phenomenon known as Angel’s Glow, where some soldiers’ wounds glowed. The explanation for Angel’s Glow wasn’t discovered until almost 140 years later.

The Battle of Shiloh was an early major battle of the American Civil War that occurred in April 1862. It all began when the Confederate forces launched a surprise attack on the Union forces in southwestern Tennessee. The cost of this battle was high — more than 20 percent of the soldiers on both sides were killed, wounded, captured or missing. That’s when things get strange.

After the battle was over, many wounded soldiers lay in a muddy field waiting for help. As night fell, some of them noticed that their wounds began to glow greenish-blue. Doctors couldn’t explain the phenomenon, but they did notice that the men whose wounds glowed had a better chance for survival than those whose wounds didn’t glow. They experienced lower rates of infections and healed faster. The soldiers called the light that helped save their lives the “Angel’s Glow.”

In 2001, a high school student named Bill Martin became interested in the Angel’s Glow after touring the Battle of Shiloh site. As part of a high school science project, Bill and his friend Jonathan Curtis decided to figure out what caused the Angel’s Glow with the help of Bill’s mother Phyllis, a microbiologist. They began by identifying bacteria that were bioluminescent, which means that they glow in the dark. They then examined historical records to determine which ones could’ve been present at Shiloh.

One candidate was the bacterium known as Photorhabdus lumicescens, which lives inside nematodes. A handful of soil contains thousands of these microscopic worms, many of which are parasites of plants, insects or animals. P. lumicescens has a symbiotic relationship with a soil nematode called Heterorhabditidae, which infects insects. A symbiotic relationship is a relationship between two different organisms. In this case, the light emitted by the bacteria may attract insects for the nematodes to infect.

Inside an insect, the nematodes regurgitate the bacteria into the blood of the insect. The bacteria release toxins to kill the insect and other microbes, and enzymes to digest it all, releasing nutrients for both the nematodes and the bacteria. Under these conditions, the bacteria glow.

That’s where P. lumicescens comes into the Angel’s Glow story. Wounded soldiers in the muddy field on a cool April night would have had a lower body temperature than normal, making them a better host for bacteria. The bacteria in the soil contaminated the soldiers’ open wounds, released toxins to kill other microbes and used some of the wounded flesh for nutrients. This bacterial infection would have caused the Angel’s Glow, while helping to heal the wound and preventing infections by other bacteria.

We will never know for sure that P. lumicescens was the cause of Angel’s Glow, but it’s the best explanation we have. A fascinating mystery of history seemingly solved by high school students. You go guys!

Medical Discovery News is hosted by professors Norbert Herzog at Quinnipiac University, and David Niesel of the University of Texas Medical Branch. Learn more at

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