Bioluminescence: Light from an unexpected source

Imagine drifting through the deep sea, where total darkness surrounds you. Suddenly, a bluish-green glow appears. Not from a lamp, nor a ray of sunlight—but from a living being producing its own light. This marvel is called bioluminescence, and yes: even microbes can glow.

What is bioluminescence?

Bioluminescence is the ability of an organism to produce its own light. This happens through a chemical reaction inside the body, where the substance luciferin is transformed with the help of the enzyme luciferase. The result? A visible glow—usually blue, green or violet.

What’s truly special is that this light doesn’t emit heat. That’s why it’s often referred to as “cold light.

Glowing microbes: tiny, but spectacular

When you think of bioluminescence, perhaps a jellyfish or a deep-sea fish comes to mind. But did you know that microbes can glow too?

Certain bacteria, like Vibrio fischeri, live inside marine animals such as squid. They help their host light up in the dark, sometimes to lure prey, other times to confuse predators. In return, the bacteria receive a safe place to live. It’s a brilliant example of cooperation between species.

Other microbes, like Noctiluca scintillans, also known as “sea sparkle”, form large colonies in ocean water, making entire coastlines glow at night. It’s a phenomenon so striking that it can even be seen from space.

Why do microbes produce light?

Microbes don’t emit light just for fun—there’s always a reason. In some cases, they use bioluminescence to communicate. By flashing signals, they can send messages to other microbes nearby. Bioluminescence can also serve as a form of defence—startling or confusing predators. And in many cases, microbes enter into partnerships with larger animals. Some bacteria live inside deep-sea creatures, like squid, helping them glow to attract prey or hide themselves. In return, the bacteria get food and shelter. Remarkably, scientists believe that certain glowing bacteria can even ‘talk’ to each other through light—a process known as quorum sensing, where microbes coordinate their behaviour based on the size of their group.