The Secret History of Bioluminescence
Illuminating maps during war, guiding planes to safety, making genes and proteins visible—organisms get their glow on to help humans.
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In the late 1990s, marine biologist Steven Haddock paid a visit to fellow scientist Osamu Shimomura at his laboratory in Woods Hole, Massachusetts. The two researchers shared an obsession with bioluminescence: light produced by chemical reactions in the bodies of living things—most famously the firefly, but also in fungi and a multitude of ocean creatures. At one point during their meeting, Haddock recalls, Shimomura poured what appeared to be large sesame seeds out of a jar and into his hand, dribbled some water onto them, and crushed them into a paste in his fist. Then he shut off the lights. His palm glowed a transfixing blue, as though it held a fairy.
The sesame seeds were in fact the dried bodies of tiny crustaceans known as ostracods. Shimomura explained that during the Second World War, the Japanese army harvested huge numbers of the creatures from the ocean. The cold blue light of umihotaru (sea fireflies) was bright enough for soldiers to read maps and correspondence, but too dim to give away their position to nearby enemies. “It was an easy, simple source of light,” says Shimomura, who is 87. “You just add water. Very convenient. You don’t need any batteries.” By the time Haddock visited Shimomura, the desiccated plankton were many decades old, yet they still retained their power to shine.
Haddock was so enchanted by this tale that he asked Shimomura if he could take a small portion of the ostracods back to his own laboratory at the Monterey Bay Aquarium Research Institute in California. He keeps them in a container no larger than a spice jar, which he rarely opens. “I’ve only tested it five or six times,” he says. But if you’re lucky, and the mood strikes, he just might take his little genie lamp off the shelf and conjure that ethereal glow.
What is it about bioluminescence that we find so mesmerizing? Light, after all, is abundant. Each morning, an immense bowl of light lifts itself above the trees and rooftops, higher than birds and mountains, and spills its golden contents. Sunlight washes over the continents and oceans, dripping down forest canopies and pooling in valleys and deserts; it splashes silently across farms and cities; it slips into our bedrooms, seeps beneath our skin, and tunnels through our eyes to illuminate the theater of the mind. Yet we can’t seem to get enough light, or feel close enough to it. Throughout history, many cultures have told stories of people and beings wreathed with halos or imbued with an irrepressible brilliance: gods, angels, fairies, saints, and jinns. To be infused with light is to be divine or supernatural, precisely because it is an impossibility for us.
Failing to summon light from within, we found other ways to generate and control it, to keep it nearby even in the Sun’s absence: we tamed fire and channeled electricity; we learned to fling bombs of color against the veil of night and line our roofs with gleaming drops of rainbow; we devised powerful beacons that could be summoned at the flip of a switch and erected shining pillars along our streets. Today, some people are even willing to sew LEDs beneath their skin in order to backlight tattoos, or simply for sheer novelty. But it is all pretense. Despite our slick technology, we have never truly matched the ostracod or firefly. We cannot equal their intuitive mastery of illumination. Light is woven into their very biology in a way we have never known. “For an organism to make light, especially to have a big display of light, seems to us like a superpower,” Haddock says.
It’s a power we could not resist exploiting. For millennia, people have devised ingenious applications for bioluminescence, many of which are little known today. Roman naturalist and philosopher Pliny the Elder wrote that one could rub the slime of a certain luminous jellyfish, possibly Pelagia noctiluca, onto a walking stick to make it double as a torch. In the late 17th century, the physician Georg Eberhard Rumphius described indigenous peoples of Indonesia using bioluminescent fungi as flashlights in the forest. And before the 19th century, coal miners filled jars with fireflies, as well as dried fish skin crawling with bioluminescent bacteria, to serve as lanterns; the safety lamp had not yet been invented and carrying an open flame into a cave risked igniting explosive gas.
It took much longer for people to find uses for ostracods and other tiny gleaming sea creatures because, for most of human history, no one knew they existed. Early explorers puzzled over ribbons and specks of light around boats and oars, as well as radiant waves and regions of shining water sometimes known as “milky seas.” Initial attempts to explain such phenomena were often closer to poetry than science. For many, light was akin to fire, even if it was in water. Hai Nei Shih Chou Chi, a fourth- or fifth-century-BCE Chinese text detailing nautical adventures, states that, “one may see fiery sparks when the water is stirred.” Likewise, in the 17th century, French philosopher René Descartes likened the light seen in agitated seawater to sparks struck off flint. During a cruise to Siam in 1688, Jesuit missionary and mathematician Guy Tachard wrote that the Sun had ostensibly “impregnated and filled the sea during the day with an infinity of fiery and luminous spirits.”
In 1753, Benjamin Franklin surmised that some sort of “extremely small animalcule” in water “may yet give a visible light.” Around the same time, naturalists such as Godeheu de Riville, equipped with early microscopes, confirmed that Franklin’s hunch was correct: the ocean’s glints and glows emanated from living things, from tiny “marine insects” we now call plankton. By the early 20th century, bioluminescent plankton were far from unknown entities—they were under intense scrutiny by some of the world’s most powerful military forces, literally caught in the crossfire of human warfare.
When ships and other vessels pass through large groups of bioluminescent plankton, ripples and clouds of green and blue light often form at their sides and in their wake. Those unwanted spotlights have proven problematic for the navy, especially when stealth is required. In 1918, during the First World War, a British ship sunk a German U-boat off the coast of Spain after spying its glowing nimbus. By the Second World War and the Cold War, navies were studying how to track subs and torpedoes with bioluminescence. The United States Navy continues such research today, attempting to develop an aquatic robot that can measure bioluminescence as a way to both detect enemies and prevent an accidental reveal.
In 1954, ocean bioluminescence saved one military man’s life. At the time, future Apollo 13 astronaut James Lovell was a fighter pilot. He was on a training mission off the coast of Japan in stormy weather, when the instrument panel in his cockpit suddenly short-circuited. All the lights and dials went dark. He could no longer rely on technology to point him back to the aircraft carrier. Looking into the blackness, he noticed a shimmering green streak in the sea, which he realized was the ship’s bioluminescent wake. He used that trail of living light as a lodestar and managed to land safely.
The following year, Shimomura began his own affair with bioluminescence—one that would eventually revolutionize the field of biology. In 1955, Shimomura joined the lab of Yoshimasa Hirata at Nagoya University, where he was tasked with extracting the organic compound luciferin from ostracods and determining its precise molecular structure. Today, scientists know that in many bioluminescent organisms, an enzyme named luciferase catalyzes a chemical reaction between luciferin and oxygen, which produces light. But back then, “we didn’t fully understand how it happened,” Shimomura says. “It was a mystery.” After 10 months of labor in the lab, Shimomura became the first person to crystallize luciferin, an essential step in studying its structure.
In the 1960s, he continued his research at Princeton University, where he also started to investigate the luminous jellyfish Aequorea victoria. Shimomura and his colleagues collected numerous A. victoria specimens and strained them like cider apples to obtain a small amount of pure glowing “squeezate.” Within the shining liquid they discovered a protein they named aequorin, which releases blue light when it reacts with calcium, even in the absence of oxygen. Another protein in the jellyfish, green fluorescent protein (GFP), sometimes absorbs that blue light, and releases green light in response.
By 1978, after collecting nearly a million jellyfish, Shimomura had thoroughly elucidated the structure of aequorin and the nature of A. victoria’s unique light-generating reactions. Both aequorin and GFP—as well as the gene coding for the latter—became indispensable tools in biology and medicine. Scientists could now tag and observe the intricate dances of previously invisible genes and proteins in living cells. In 2008, along with Martin Chalfie of Columbia University and Roger Tsien of the University of California, San Diego, Shimomura received the Nobel Prize in Chemistry for his work on GFP.
More recently, bioluminescence has evolved from laboratory tool to commercial plaything. The Kickstarter-funded, San Francisco-based Glowing Plant Project offers customers DIY kits they can use to genetically engineer a luminous Arabidopsis plant at home. And Carlsbad, California-based BioPop has released what is essentially an illuminated version of that long beloved novelty pet for kids, Sea-Monkeys (which are not in fact tiny aquatic primates, but rather brine shrimp). They call it Dino Pet: a small, vaguely Apatosaurus-shaped aquarium filled with bioluminescent plankton known as dinoflagellates. During the day, the plankton photosynthesize; at night, if you shut off the lights and give the aquarium a good shake, the dinoflagellates light up turquoise, much like the “fiery sparks” Chinese sailors observed in churning seawater so long ago. But the glow is only good for about three shakes a night, and if you’re too rough, you could damage or kill the plankton.
It’s easy to pity those tiny swimming stars trapped in a plastic bubble. Each night, some titan’s hand engulfs their ocean and churns it into a maelstrom for a few moments of selfish delight. Then the monster puts away their entire universe, easy as shutting the lid on a music box. They are kept alive solely for the purpose of this bedside magic trick.
Perhaps, though, we are the more pathetic members of this relationship—the gods bewitched by a gnat. Bottling bioluminescence gives us a sense of ownership over a presumably rare and otherworldly phenomenon; the reality of the situation is quite different. Bioluminescence is so commonplace on our planet—particularly in the oceans—that scientists estimate the thousands of glowing species they have catalogued so far are just a fraction of the sum. It may well be that the vast majority of deep-sea creatures, which live beyond the Sun’s reach, generate their own light (sometimes with the assistance of microbes). They use these innate glows primarily to communicate: to warn and frighten, hide and hunt, lure and beguile. Bioluminescence is one of the oldest and most prevalent languages on Earth—and one that is largely alien to us. Despite our fantasies and mythologies, the truth is that there’s nothing supernatural about living light; it has been a part of nature for eons. It’s just that we were denied this particular gift.
So, with perhaps too little gratitude, we adapted the incomparable talents of glowing creatures for our own purposes. We borrowed their light and it revealed things about our own biology we might never have discovered otherwise. But that is all we can do—borrow. We cannot be them, so we seek them out, and draw them near us—every bit as mesmerized as when we thought the Sun had impregnated the sea. To this day, we cup them in our hands, collect them in jars, and place them on our nightstand, forever trying to satisfy our Promethean hunger.