Nights on Earth are dark. True, we have our moon, and even on a moonless night the stars in their thousands provide beauty, and some light. But it’s definitely nothing like nights on Pandora, the fictional world where the Avatar movies are set. There, nature has taken bioluminescence — light emitted by living things through chemical reactions in their bodies — to a whole new level. Many people were gripped by the cinematic masterpiece of the Pandoran landscape, and the night scenes were some of the most striking and beautiful. So why aren’t our nights so brightly lit? 

Glowing Nature Here on Earth

We do actually have a lot of glowing animals, fungi, and microbes here on Earth, though often more subdued and less ubiquitous than on Pandora. Oddly enough, there are no known bioluminescent plants, either on land or in the oceans. One of the most mysterious phenomenon, caused by bioluminescent bacteria Vibrio harveyi, is called milky seas. It was reported by sailors for centuries, including Charles Darwin, who on his famous Beagle voyage encountered it, writing that, “The sea was luminous in specks and in the wake of the vessel, of a uniform slightly milky colour. When the water was put into a bottle, it gave out sparks…” Despite this history, milky seas were only recently photographed via satellite images. A more common sight is that of sea sparkle, caused by the dinoflagellate (plankton) Noctiluca scintillans, and seen as a glowing wake sometimes left by ships, or shining blue waves crashing onto a beach.

Elsewhere in the ocean, many deep-sea creatures use light, both to attract mates or prey, for communication, camouflage (counterillumination), or for escaping predators. For example, while surface dwelling squid release ink to blind and confuse an attacker, this strategy is useless at depths where light doesn’t penetrate. Instead, the vampire squid distracts a would be predator (or occasional deep-sea researcher) by ejecting a bioluminescent mucus. Effective, if a little gross. The firefly squid of Japan creates a beautiful light show each spring in Toyama Bay, Japan, when they come closer to the surface to mate. It’s quite the event apparently, complete with boat tours and a dedicated museum. And of course, most everyone has seen pictures of gargoyle-esque anglerfish, which use a glowing lure to attract a potential meal, then seizing it with massive jaws full of razor-sharp teeth.

While the majority of bioluminescent organisms are found in the ocean, glowing life on land is no less diverse and amazing. Probably the most commonly seen are fireflies, which live throughout the temperate and tropical regions of the world. Each species produces a different pattern of light, allowing amorous adults to find each other at night and mate. Interestingly, not all adult fireflies glow, though the larva (known as glowworms) of all 2000+ species do. One of the most spectacular sights of bioluminescence on land can be seen in some New Zealand caves — produced by the larva of certain fungus gnats which make their home there, and glow in order to attract prey. Confusingly, they’re also called (New Zealand) glowworms, though they belong to an entirely separate family of insects than fireflies. It’s quite something apparently, and an entire tourist industry has been built up around it. 

Not to be outdone, some of the brightest instances of glowing life are fungi. Foxfire, or fairy fire, is the name given to light produced by about 70 species of bioluminescent fungi. Observed since the time of the ancient Greeks and Romans and used by some cultures in the past as dim torches, most glow quite faintly, but some are reportedly bright enough to read by.

How Does It Work?

The cause of all this glowing is a class of molecules known as luciferins. There are numerous types of luciferin found across the domains and kingdoms of life, indicating that they developed independently, and that bioluminescence can be a useful biological trait. This diversity also accounts for the variations of color that we see in bioluminescent organisms. These luciferins usually undergo a reaction with oxygen catalysed by an enzyme known as luciferase — but some luciferin reactions take a different approach, skipping luciferase and instead using other compounds called photoproteins. These produce light by combining with oxygen and luciferin, along with something else, usually a metal ion.

Science and Medical Applications

The point of explaining how photoproteins work is that one of them, “green fluorescent protein,” or GFP, from the crystal jelly(fish) is actually quite important to us. It is used extensively in medical research, allowing scientists to shed light on previous hidden biological processes. It works by illuminating gene expression. The gene coding for GFP is first attached to any gene of interest. Then, if the gene being studied is expressed, the GFP gene is as well, allowing researchers to literally see that it’s active, and thereby figure out what it does in the body. This technique was so revolutionary that it won the 2008 Nobel Prize in chemistry. 

It’s fascinating how quickly something can go from cutting edge to “simple” and well understood. Around the time this research won the Nobel Prize, it was already so common that I used it in a second-year biology class at university. We took a bacteriophage (virus that attacks bacteria) and used it to transfer the GFP gene plus another gene for antibiotic resistance into non-pathenogenic E. coli bacteria. Then we doused the bacteria with the antibiotic, flipped on a blacklight, and were able to see the green glow of bacterial colonies in a petri dish that had successfully incorporated both genes (bacteria that didn’t have the genes were killed by the antibiotic). I’m pretty sure now they do this sort of experiment in high school biology classes, and that kits are widely available online.

The Future Is Bright

The future for bioluminescence could be big. There are two sides to it — the useful side, and the fun side. Practical applications might include crops, which could be engineered to luminesce when they need water, nutrients, or if they’re suffering a stressor like disease or attacks by insects. It could even be color coded so that farmers know what the exact problem is (RED = PLAUGE OF LOCUSTS!!!). Bioluminescent trees could help light our streets at night, potentially reducing the need for electricity while making suburban neighborhoods look sci-fi cool.

Earlier I said that there are no known glowing plants here on Earth. I should have said that there are no naturally occurring glowing plants. That sad lack is being remedied as we speak, with multiple companies currently working on creating and commercializing bioluminescent house plants for our enjoyment. I hope one day we all have the option of reading a good book by the light of a glowing tree. It isn’t just plants though, animals too are being engineered to glow. For more than a decade, animals from fish to cats to sheep to monkeys have been given the GFP gene, allowing them to glow green when exposed to ultraviolet light. But what you really want is animals that express luciferin and luciferase, letting them light up just like a firefly. This has actually been done, so I think sooner or later we’ll see this technology make its way into other animal species, and out into our lives and homes.

Glow in the dark plant prototypes by Glowleaf | Image: Glowleaf.bio

Could we perhaps create a Pandora-like ecosystem some day? That’s the standard we can aim for, and measure our progress against. Dreaming big, maybe we could one day terraform a world around another star, and populate it with these glowing life forms we’ve created. Make our own version of Pandora.

-Owen Lewis