The Battle of Shiloh, which took place on April 6 and 7, 1862 during the American Civil War, left nearly 23,746 people dead. A tragic figure for a place whose name means “place of peace” in Hebrew. At the end of the fighting, more than 16,000 wounded soldiers still lay in the woods and ravines, often unable to move, exposed to the rain and the cold.
When the doctors finally reached the battlefield, they were confronted with a disturbing scene. In the darkness, some wounds seemed to emit a strange blue glow, Popular Mechanics reports. Even more surprising, soldiers whose wounds glowed had, against all odds, a better chance of survival than others. This mysterious phenomenon was quickly nicknamed “Angel’s Glow” (the glow of angels) and some saw it as a sign of divine intervention.
For more than a century and a half, the origin of this glow remained unexplained and it was only in 2001 that two American high school students, Bill Martin and Jon Curtis, decided to study the phenomenon after discovering it in history class. With the help of the mother of one of them, a microbiologist, they carried out a scientific investigation at the Shiloh site.
Their research revealed that the mysterious light actually came from a bioluminescent bacteria called Photorhabdus luminescens. Unlike many bacteria present in wounds, this one is not pathogenic for humans. It lives in symbiosis with nematodes present in the soil, which usually infect insects.
An extremely rare phenomenon
The mechanism is remarkable. Nematodes carry the bacteria into their body and introduce it into their prey. Once inside, P. luminescens releases toxins that are deadly to the insect and produces enzymes that break down tissue, allowing both organisms to feed on each other. It also secretes antibacterial substances that prevent other microbes from colonizing the carcass.
It is precisely this property that is said to have saved many soldiers in Shiloh. The bacteria’s secretions would have prevented serious infections, such as gangrene, which were responsible for a large number of deaths at the time. Bioluminescence itself is due to a set of genes called an “operon”, which allows the production of light, although the exact purpose of this light emission is still debated.
However, a question remained: why is this phenomenon so rare in humans and has only been seen once, in Shiloh? The experiments carried out by the two students provided part of the answer. The bacteria does not normally survive human body temperature. However, the weather conditions in Shiloh—heavy rain, cold nights, and persistent humidity—likely lowered the temperatures of the injured, allowing the bacteria to grow temporarily.
Thus, what seemed supernatural is today explained by a combination of biological and environmental circumstances. Insects attracted by blood would have carried these bacteria into open wounds, where they played an unexpected role as a natural disinfectant.
The study by Bill Martin and Jon Curtis, rewarded in an international scientific competition, has definitively shed light on this historical mystery. Behind the poetic image of “Angel’s glow” In reality, a fascinating and extremely rare microbiological phenomenon was hidden.
