Bacteria Use Chemical Signals to Communicate

3d image of purple and blue bacteria against dark blue background

Biological Strategy

Bacteria

AskNature Team

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Sense Chemicals (Odor, Taste, etc.) From the Environment

Chemicals are important for signaling and communication among living systems, either intentionally (such as when two living systems try to find one another) or unintentionally (such as when a plant emits a chemical signal that an herbivore can use to find a tasty bite). They are also important for other uses, such as navigating or finding sources for minerals. But chemical signals are often relatively weak and disperse when moving through water or gases. Therefore, detecting them requires specialized abilities, including a way to determine where they are coming from. A well known example of sensing chemicals can be seen in ants following a pheromone trail laid down by others in their colony to locate a quality and abundant food source.

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Bacteria

Domain Bacteria (“small staff”): L. acidophilus, Staphylococcus

From inside of our own bodies to the deepest parts of the ocean, bacteria have adapted to almost every possible environment. All bacteria are unicellular, microscopic, and lack a membrane-bound nucleus and organelles, and come in three basic shapes: spherical (cocci), rod (bacilli), and spiral (spirilla). Some strains can be deadly, like Staphylococcus aureus (MRSA) while others, like Lactobacillus acidophilus, found in our intestinal microbiome, keep us healthy. Cyanobacteria, also known as blue green algae, caused the Great Oxidation Event 2.4 billion years ago, producing Earth’s first oxygenated atmosphere.

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Bacteria sense each other using chemicals to determine local density.

You can’t play tic-tac-toe alone; jumping rope requires at least 3 people; and in a professional soccer match each team needs 11 players. A minimum number of individuals are required in order to do certain things.

It’s the same for bacteria. These tiny organisms, which live unseen on almost every possible surface, including in the air and water, often live as independent cells. However, sometimes bacteria need to form larger groups in order to do new things, like protect themselves or produce new chemicals. When a minimum number of bacteria are in a certain area, they can suddenly change what they’re capable of doing, such as forming colonies with different physical abilities, producing different chemicals, and behaving in ways that can make them harder to get rid of. How do bacteria know when they have enough individuals to make the switch?

Bacteria use chemicals to communicate with each other. They can communicate about lots of things, including keeping track of the overall number of bacterial cells in a certain area. Bacteria pass ‘messages’ to each other by releasing different chemicals. Bacteria have sensors on the outside of their cells that allow them to pick up these chemical signals from other bacteria. When a lot of bacteria are in a certain area, there are lots of signals being picked up by the sensor. When the communication chemicals reach a certain threshold, this triggers to the other bacteria that there are enough of them to make the switch to start behaving as a colony.

Having systems for knowing when conditions are right to take action is something bacteria have mastered, and it’s a skill people often could use as well. Timing a policy change, introducing a new idea at a meeting, or altering one’s own behavior can perhaps all be done better by attending to cues around us.

To learn more about quorum sensing in bacteria, check out this iBiology video lecture entitled, “Bacterial Communication via Quorum Sensing“