When I was living in Japan, I got the chance to see an amazing sight. I went to the beach at night and was amazed to see a large swath of water ebbing and flowing – and glowing with a bright blue light.
It turns out that the water was full of what the Japanese call “Yakouchuu” – a bioluminescent bacteria.
Today we’ll learn about these fascinating creatures.
There Are a Couple Types
Noctiluca scintillans, usually called “sea sparkle”, is one such species. However, it is not a bacterium. It is a single-celled protist (specifically, it’s a dinoflagellate, meaning it is a single-celled organism that has two flagella).
It lives in salt water, although there are some varieties that live in fresh water.
Its light-emitting bioluminescence is created when the enzyme luciferase oxidizes the luciferin compound inside a special organelle called a scintillon.
Photorhabdus luminescens is a group of bioluminescent bacteria that lives in the gut of parasitic nematode worms. These worms live in the soil.
Angel’s Glow – How Civil War Soldiers Glowed
On April 6, 1862 during the American Civil War, Union Major General Ulysses S. Grant led a battle in Tennessee called the Battle of Shiloh.
That battle left over 16,000 soldiers wounded, and it killed more than 3,000. The wounded soldiers were stuck laying in moist mud for days, and for some of them, their wounds started to glow. This was known as “Angel’s Glow”. Theorists who have studied the phenomenon believe that the soldiers were infected by the Phtorhabdus luminscens bacteria from the soil.
Normally, Photorhabdus sp. cannot live in humans because the body temperature is too high. However, for the soldiers laying on the battlefield in the spring in Tennessee, it has been determined that they probably suffered from a bit of hypothermia from the cold nights and the wet conditions.
So, the theory that they were infected by the bioluminescent bacteria from the soil seems to be a valid one.
The interesting thing that happened, however, was that those soldiers who had glowing wounds survived more often than those who didn’t. And we know now that Photorhabdus luminescens secretes chemicals that kill competing organisms, kind of acting like an antibiotic. So getting infected by that bacteria was a bonus to many of the wounded soldiers.
An Awesome Sight to See
Watching glowing water is a sight everyone should experience once in their lifetime. People flock to areas that are known to have these bacteria, such as Puerto Rico’s Vieques Island, to witness the magic. In 2005, a glowing area roughly the size of Connecticut was first observed from space in the Indian Ocean.
They are found throughout the world, though, so chances are you can find a place to see them not too far from where you live. You don’t have to fly to Japan or China or New Zealand to see them.
Science Is Beginning to Use It
Scientists are starting to study and use bioluminescence in a lot of unique ways.
It's being used for:
- genetic research, to tag genes
- for medical purposes (to detect Alzheimer's disease or cancer, for example)
- in dentistry, to determine the risk of dental decay
- in warfare, to detect and track vessels in the water
- in studying drug-resistant pathogens
- in the development of nanomaterials
- to understand ocean ecology by measuring the distribution of bioluminescent organisms
- to evaluate toxicity and develop new screening assays
- and more!
Here's a TED Talk by a microbiologist about the exciting potential uses of bioluminescent bacteria in science and medicine: