Name: quorum sensing in bacteria
Uploaded: 2026-08-26T08:19:12.529Z
Duration: 1 min 50 s
Channel: JoVE

Similar to eukaryotic cells, some bacterial cells also use chemical signaling to communicate.Quorum sensing is a form of cell-cell communication. As bacterial population density increases, bacteria coordinate their behavior by turning quorum sensing on.These bacteria release small signaling molecules called autoinducers.As the bacterial population grows, the concentration of autoinducers in the surrounding environment increases.When autoinducers accumulate and reach a threshold concentration, they bind to specific receptors in or on bacterial cells. This triggers intracellular signaling pathways.This signaling can activate intracellular second messengers, such as cyclic di-GMP. These messengers regulate the expression of specific genes involved in biofilm formation, virulence, and antibiotic tolerance.Quorum sensing enables some bacterial species to coordinate collective behaviors.For example, in certain bioluminescent bacteria, quorum sensing activates light production only when the bacterial population reaches a sufficient density.Quorum sensing also plays an important role in biofilm formation. Biofilms are communities of bacterial cells attached to surfaces, where they can get

bacterial signaling

Bacterial Signaling

Bacterial signaling can occur within bacteria (intracellular) or between bacteria (intercellular). At times, a group of bacteria behaves like a community. To achieve this, they engage in quorum sensing, the perception of higher cell density that causes changes in gene expression. Quorum sensing involves both extracellular and intracellular signaling. The signaling cascade starts with a molecule called an autoinducer (AI). Individual bacteria produce AIs that move out of the bacterial cell membrane into the extracellular space. AIs can move passively along a concentration gradient out of the cell or be actively transported across the bacterial membrane.The Extracellular Concentration of AIs Gives Signals to BacteriaWhen cell density in the bacterial populations is low, the AIs diffuse away from the bacteria, keeping the environmental concentration of AIs low. As bacteria reproduce and continue to secrete AIs, the concentration of AIs increases, eventually reaching a threshold concentration. This threshold permits AIs to bind membrane receptors on the bacteria, triggering changes in gene expression across the whole bacterial community. Examples of phenotypes induced by quorum sensing include bioluminescence, motility, formation of biofilms, and expression of virulence factors.Signaling in Bacteria That Produces LightBioluminescent bacteria, such as Photorhabdus luminescens, produce light as a result of a complex signaling process. These bacteria use quorum sensing, which allows them to coordinate the production of bioluminescence. For example, P. luminescens produces autoinducer 2 (AI-2) as a quorum sensing signal and as an intracellular signal. The bacteria release AI-2 into the environment. When AI-2 reaches threshold levels outside the bacterial cells, AI-2 binds to an ATP-binding cassette (ABC) transporter on the bacterial membrane and it is re-internalized by the ABC transporter. Then, an intracellular kinase, LsrK, phosphorylates AI-2 itself. Once activated in this way, AI-2 participates in an intracellular signaling pathway that activates genes encoding the enzyme luciferase. Luciferase produces light after catalyzing specific reactions. As a result, bioluminescence is observed only when the P. luminescens population reaches a critical density.Quorum Signaling and Bacterial Infections of Implanted Medical DevicesThe spread of bacteria across the surface of medical implants occurs through quorum signaling and can cause life-threatening infections. There is a lot of current research into stopping the formation of bacterial biofilms in medical settings. Much of this research focuses on developing new materials that inhibit bacterial growth.

Bacterial signaling can occur within bacteria (intracellular) or between bacteria (intercellular). At times, a group of bacteria behaves like a community. ...

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quorum sensing in bacteria

Quorum sensing lets bacteria coordinate behavior by sensing how many cells are nearby. Bacteria can signal inside the cell or between cells. When many bacteria act together, they can behave like a community and change gene expression as a group.

This signaling starts with autoinducers, or AIs. Individual bacteria make AIs and release them across the cell membrane into the surrounding space. Some AIs diffuse out passively along a concentration gradient, while others are moved out by active transport.

When bacterial density is low, the AIs spread away and stay at a low environmental level. As the bacteria keep dividing and releasing AIs, the concentration rises. Once it reaches a threshold, the AIs can bind membrane receptors and trigger changes in gene expression across the community.

Quorum sensing can lead to several bacterial traits. These include bioluminescence, motility, biofilm formation, and the expression of virulence factors. One example is the light-producing bacterium Photorhabdus luminescens, which uses quorum sensing to turn on bioluminescence only at high cell density.

In P. luminescens, AI-2 serves as both a quorum sensing signal and an intracellular signal. The bacteria release AI-2 into the environment. When the outside concentration reaches a threshold, AI-2 binds an ATP-binding cassette, or ABC, transporter on the membrane and is brought back into the cell.

Inside the cell, the kinase LsrK phosphorylates AI-2. In this activated form, AI-2 can act as a transcription factor and turn on genes that encode luciferase. Luciferase catalyzes the reactions that produce light, so bioluminescence appears only when the bacterial population becomes large enough.

Quorum signaling also matters in medical settings. Bacteria can spread across the surface of implanted medical devices through this kind of signaling, and the result can be serious, life-threatening infection. Current research aims to stop biofilm formation on these devices, including work on new materials that limit bacterial growth.

Quorum Sensing in Bacteria

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Quorum sensing lets bacteria coordinate behavior by sensing how many cells are nearby. Bacteria can signal inside the cell or between cells. When many bacteria act together, they can behave like a community and change gene expression as a group. This signaling starts with autoinducers, or AIs. Individual bacteria make AIs and release them across the cell membrane into the surrounding space. Some AIs diffuse out passively along a concentration gradient, while others are moved out by active...

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key terms and concepts

Explore how bacteria use autoinducers and quorum sensing to switch genes on as a group, produce light, and form biofilms on medical devices.

Quorum Sensing in Bacteria | JoVE K12

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Quorum Sensing in Bacteria

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