Fig. 1 Bioluminescent plankton along a beach in the Maldives (Source: Flickr)
You might have come across photos of beaches whose waters look more like a million fairies or the night sky than the normal waves rushing ashore. If you are really lucky, you might have visited one of the locations where such a glorious ecosystem exists, like the beaches of Puerto Rico and the Maldives. What is this beautiful phenomenon that appears nothing short of magical? Bioluminescent plankton.
Bioluminescent plankton are a group of marine organisms that produce light. This group is made up of a variety of organisms including bacteria such as Vibrio fischeri and Photobacterium leiognathi. The term “bioluminescent” says it all – “bio” meaning life, and “luminescence” meaning light, together: light produced by a living organism.
Fig. 2 Bioluminescent plankton in Belgium (Source: Wikipedia
Bioluminescent organisms are found in a handful of ecosystems and include life forms that are quite different from each other - animals, bacteria, and protists. As you can probably imagine, for a tiny living cell, producing light is quite a bit more work than simply screwing in a lightbulb. Since it is a very energy intensive process, and one cell alone doesn’t really produce any noticeable light, there is no point in investing energy in producing light if you don’t have a bunch of friends around you doing the same thing. That is why when the bioluminescent organisms in question are bacteria, bioluminescence is considered a density dependent trait. Density dependence means that Individual cells only produce light if there are other cells around them that are able to do the same thing. Think of it as bacterial peer pressure. But how do bacteria know if there are enough bioluminescent friends around them? Thanks to something called “quorum sensing,” bacteria (as well as some insects) can communicate in order to act in sync as a group. Quorum sensing is used by bacteria for many processes in addition to light production, such as antibiotic production and causing disease. Here’s how quorum sensing works: bacterial cells sharing the same environment release a specific molecule such that when the concentration of the molecule reaches a certain value in the environment, all the cells realize there are plenty of friends around them, getting ready to produce the goal molecule in question. In this case, they would each receive the memo: “let’s all produce light!”. Next, the genes in all of the cells present are switched on for the production of an enzyme called luciferase in order to make light, but more on that in a bit. 
This all sounds like a bit of a hassle, doesn’t it? And for what – just so that us humans can admire this special shimmering scene? Researchers have several ideas as to why marine bacteria go to all this trouble to produce light. A common hypothesis is that light production is a way for cells to lure in hungry fish and other marine animals. Once the bacteria are eaten, they can set up shop in the animal’s nutrient rich gastrointestinal tract, where they can live like kings! The bacteria get a pretty much endless food supply, and the animal is able to use the light produced by the bacteria to its own advantage. Some animals even have organs with transparent tissues that have evolved to showcase the light produced by their new little tenants. This presentation can be used to evade predators or even to attract prey (just like in that terrifying Finding Nemo scene), but either way it’s a win-win! 
The bacterial bioluminescence system is very similar to other bioluminescent animals such as fireflies and jellyfish. This natural strategy is so impressive that we actually borrow this “technology” for research applications. Turns out we can still learn a thing or two from nature. Bioluminescence is used in labs in order to visualize and analyze different biological systems. Light is produced with the help of the previously mentioned enzyme luciferase, which acts on a protein called luciferin. Through a set of chemical reactions, luciferin reaches an excited state, and when luciferin goes back to its grounded state, it releases a photon of visible light. .
Fig. 3 Bioluminescence in fireflies is produced in a similar manner as marine microbes (Source: Flickr)
When I was a little girl I was absolutely certain that I had seen fairies in the trees one night. Years later, the unfortunate realization dawned on me that those fairies might have actually been fireflies. While it can be fun to believe in magic and to think of natural phenomena as sorcery, there is also something quite enchanting about understanding the science of the world around us and how it works. Whether in the context of fireflies in the woods or illuminated ocean waves, the fact that these organisms have been able to develop such a brilliant and beautiful mechanism is in itself, quite magical.
Fig. 4 Fairies in the woods or luciferin produced in fireflies releasing photons? (Source: Flickr)
Dunn, Anne K. “2 Vibrio fischeri Metabolism: Symbiosis and Beyond.” Advances in microbial physiology 61 (2012): 37.
Kiyama, Masahiro, R. Saito, S. Iwano, R. Obata, H. Niwa, and S. A. Maki. “Multicolor bioluminescence obtained using firefly luciferin.” Current topics in medicinal chemistry (2016).
Hastings, J. Woodland. “Chemistries and colors of bioluminescent reactions: a review.” Gene 173, no. 1 (1996): 5-11.
More From Thats Life [Science]
- Biology Superpowers: X-Ray Vision
- How to Expand Your Senses by Reading a Blog Post
- What's up with bat echolocation?
- Seeing is Believing - How Can We Visualize Tiny Colorless Bacteria?
- Saving water is no longer a matter of how short our showers are · Water balance in a man-made world
- Double Digestion in Rabbits · Why Does Mopsy Eat Her Own Poop?
- Should I say sex or gender? Pt. 2
- Should I say sex or gender? Pt. 1
- How To Catch Hard-to-Catch Fish?
- Finding the Perfect Partner
- Is your gut trying to kill your resolve? · Mind over microbe
- Why Do Mothers Mother?
- GMO! The Places You'll Go!
- New-Fangled Paleontology · Really Old Fossils, Really Strong Predators, and Cool New Tech
- A Brief History of Evolutionary Thought, part III
- Saving face: transplanting our most distinctive features
- A Brief History of Evolutionary Thought, part II
- DNA as a solution for data storage · DNA - Nature’s Hard Drive
- A Crash Course in the Coolness of Mitochondria · Mitochondria: The Underrated Organelles
- A Pollinator’s Job Description and Why We Should All Care About Them · Pollination 101
- You May Say I’m Biased, But I’m Not the Only One
- The evolution of one of the greatest medical discoveries in history. · The Path of Least Resistance: Our Relationship with Antibiotics
- Mother Nature’s History Book · Estimating the Age of Life Long-Gone
- Proprioception as a vital sense · Know Your Limb-its
- Man’s Best Artificially-Selected Friend · Your Dog is a GMO Wolf
- Better Safe Than Sorry: The Pesticide Industry is Getting a Revamp
- Sometimes scientists have to get creative in order to effectively do science – especially on a budget. · The Bizarre Shopping List of a Determined Scientist
- Insects Get Sick Too: The Study of Insect Pathology
- Our teeny tiny friends and their huge potential · Employee of the Month - Hire a Microbe to Do Your Work
- A Brief History of Evolutionary Thought - Part I
- The Effects of Custom Build Paradise · Artificial Islands
- To B(PA) Or To Not B(PA): Regulating Endocrine Disruptors
- Bioluminescence truly looks like it is nothing short of sorcery, and although this naturally occurring phenomenon is well studied and explained, that does not take away from its beauty. · Fireflies of the Ocean: Lighting up the Dark with Science
- Part II - Cases of altruism in the animal kingdom · Charity cases in nature - when are animals more likely to be altruistic?
- Part I - Why true altruism is a rare behavior in the animal kingdom · Being selfish means staying alive
- Penguins and other strange things we study from space
- Pseudoreplication and the Art of Biological Statistics
- What is wrong with my tomatoes?...And other plant disease questions · Why did orange prices increase?
- How fecal microbiota transplants can improve lives and possibly save them · The Wonders of Fecal Transplants
- The scientific facts behind the safety and efficacy of childhood vaccines · Calling the Shots - Discussing Vaccines
- 3D Printing for Fun and Science
- What is wrong with my tomatoes?...And other plant disease questions · What is Phytopathology?
- Medical Mysteries Still Surrounding Zika Virus
- More ›