A long time ago, in April of 1862, a Union force called the Army of Tennessee led by Major General Ulysses S. Grant camped at Pittsburgh Landing, Tennessee. On April 6, the Confederate Army of Mississippi led by General Albert Sidney Johnston launched a surprise attack on them on the west side of the Tennessee River. The battle raged for two days and the Confederate Army retreated at the end. The fighting left over 16,000 wounded and 3,000 dead, and neither of the armies was medically prepared for that scale. Though several of the wounded died due to infections, something else also happened after the battle which unexpectedly saved many of them.
Two days after the Battle of Shiloh, which occurred on April 6-7, 1862, the medics who arrived at the battleground noticed that the wounds of many soldiers had a faint, greenish-blue glow at night. Mysteriously, the wounds that glowed healed faster and scarred less than those that did not glow giving it the name “Angel’s Glow.”
Unfortunately, after the battle, the wounded soldiers did not receive immediate help as the armies did not foresee that there would be such large-scale slaughter. Help arrived two days later, and until then the soldiers had to lie in the mud and under the rain. When the medics finally arrived, they noticed that some of the wounds had a faint glow and that they had fewer infections, healed faster, and left less scar tissue. The glow soon earned itself the nickname “Angel’s Glow” among the soldiers, and many who heard of it dismissed it as folklore or exaggeration until last decade when two teenagers finally solved the mystery.
Almost 140 years after the battle, the phenomenon was finally explained by two students Bill Martin and Jon Curtis, seventeen and eighteen years old respectively, during a science fair in 2001. Martin got the idea when his mother, a microbiologist, was working on luminescent bacteria that live in soil.
Bill Martin once went on a visit to the battlegrounds of Shiloh and when he heard about the glowing wounds of the soldiers he asked his mother, Phyllis Martin, a microbiologist at USDA Agricultural Research Service in Beltsville, Maryland, if the P. luminescens bacteria she was working on could be responsible for the phenomenon. When she told him to experiment and find out, he partnered with his friend Jim Curtis to start their research.
However, during their experiments, they discovered that the P. luminescens cannot survive at normal human body temperatures. Then they found that since the soldiers were wounded and left on the battlefield they would have experienced hypothermia due to wet conditions in which they had to wait, and that would have helped the bacteria.
The Photorhabdus luminescens bacteria live inside parasitic worms called nematodes that reside in the blood vessels of larvae and eat them inside out.
The P. luminescens bacteria and the nematodes have a simple symbiotic relationship. After the nematodes burrow into the insect larvae they spew out the bacteria inside their gut. The bacteria then produces chemicals that suppress and kill all other microorganisms along with their host larva. Then, the nematodes and the bacteria feed on the larva growing and multiplying without facing any resistance. When the host is hollowed out, the nematodes swallow the bacteria back and let them recolonize inside their gut. Soon, their bioluminescence attracts other insects providing them a further food source.
As the P. luminiscens bacteria release chemicals that kill all other bacteria, basically acting as very effective antibiotics, the glowing wounds healed faster increasing the soldiers’ chances of survival.
The wounds of the soldiers which glowed blue could easily have been infected by the bacteria as they get exposed to the dirt, debris, or shrapnel which are contaminated. Along with that, the temperatures during the nights in early April were relatively cool due to rains which lowered the body temperature of the soldiers giving perfect conditions for the P. luminiscens bacteria to thrive. What’s even more fortunate is that neither the bacteria nor the nematodes are infectious to humans, so the soldiers were never harmed by either of them.
For their study, Bill Martin and Jon Curtis earned first prize in the 2001 Intel International Science and Engineering Fair. Whether benevolent angels truly exist or not, the soldiers who survived definitely had P. luminiscens bacteria to thank for their lives.
[sources: wikipedia, Mentalfloss, americancivilhistory]