Bioluminescent Microbes

Headlines warning about “flesh-eating bacteria” or “deadly superbugs” inevitably attract more attention than a story about a glowing bacterium living peacefully inside a little-known squid. Yet, despite the spotlight on harmful microbes, most interactions between animals and microbes are actually mutually beneficial. Bioluminescent bacteria are a striking example: they colonize fish and squid, exchanging their light for food and shelter. At first glance, it may seem paradoxical that a microbe would spend so much energy producing light. What possible advantage could glowing offer to a tiny cell adrift in the ocean? In fact, some single-celled dinoflagellates can reach immense population densities in warm, nutrient-rich waters, creating visible “blooms.” These blooms, fueled by pollution and climate change, showcase how microbes use collective bioluminescence to confuse predators and survive.