Did you know that microbes communicate? The way they do this is called quorum sensing. Let’s explore talking microbes.
This 2009 TED Talk by Dr. Bonnie Bassler gives a quick introduction to quorum sensing. I chose Dr. Bassler because she does a great job of explaining this very complicated subject.
Quorum Sensing: The Chemical Language of Microbial Communities
In the late 1960s, scientists studying microbes’ bioluminescence discovered quorum sensing. They first called it “autoinduction.” This eventually became known as quorum sensing. (iBiology, 2023) Microorganisms can use secreted signaling molecules to talk to each other and plan their group behaviors. This is called "quorum sensing." This chemical "language" allows bacteria, fungi, and other microbes to detect their population density and regulate gene expression accordingly.
Widespread, But Not Universal
While quorum sensing appears widespread in the microbial world, it is not a universal capability. Researchers estimate that around 70–80% of bacteria utilize quorum sensing systems. Gram-negative bacteria often use acyl-homoserine lactones as autoinducers. “Acyl homoserine lactones (acyl-HSLs) are important molecules that bacteria use to send signals between cells and track how many of them there are. This is called quorum sensing control of gene expression. Members of the LuxI family of proteins synthesize these signals.” (Parsek et al., 1999). Yeasts, fungi, and archaea have been seen to use quorum sensing, but it is not as well understood as it is in gram-positive bacteria. Not all microorganisms possess this cell-to-cell communication, but it provides a selective advantage to those who do.
Regulating Diverse Behaviors
By sensing their own population density, microbes can coordinate and synchronize activities that are only effective when undertaken in unison by the group. These cooperative behaviors include bioluminescence, virulence factor secretion, antibiotic production, biofilm formation, sporulation, and more. When a certain amount of autoinducer is present, the behaviors get stronger, meaning there is enough quorum to proceed.
During infection, the responsibility of QS control is believed to postpone the production of “public goods” until the bacteria have grown to growth-limiting densities, at which point the QS-controlled products can be produced at sufficient concentrations. (Otto et al., 2023)
Clinical Significance
In pathogens, quorum sensing controls the expression of virulence factors. Blocking quorum sensing is becoming popular as a way to fight infections. (This is discussed in Dr. Bassler’s Ted Talk in 2017:
Biofilm formation also uses quorum-sensing signals. This is being looked into to stop infections that come from devices. Understanding microbial communication through quorum sensing provides insights into community dynamics and survival strategies.
Conclusion
Quorum sensing exemplifies the complex, coordinated social lives of microorganisms. Researchers are still finding new autoinducers, behaviors controlled by cell-density cues, and differences in how organisms sense quorums. Mastering the chemical languages of microbes promises progress in medicine, agriculture, and environmental science. This is yet another reminder that microbes, though tiny, have evolved sophisticated means of thriving.
Sources
Bassler, B. Ph.D., How Bacteria “Talk.” Youtube.com. 2009.
Bassler, B., Ph.D., Quorum Sensing: Bacteria Talks. YouTube.com. 2014.
IBiology.org. Autoinduction: The Discovery of Quorum Sensing in Bacteria. 2023. https://www.ibiology.org/microbiology/autoinduction-discovery-quorum-sensing-bacteria/
Otto, M., Dickey, S. W., & Wolz, C. (2023). Editorial: Quorum-sensing in Gram-positive pathogens – mechanisms, role in infection, and potential as a therapeutic target. Frontiers in Cellular and Infection Microbiology, 13, 1236705. https://doi.org/10.3389/fcimb.2023.1236705
Parsek, M. R., Val, D. L., Hanzelka, B. L., & Greenberg, E. P. (1999). Acyl homoserine-lactone quorum-sensing signal generation. Proceedings of the National Academy of Sciences of the United States of America, 96(8), 4360–4365. https://doi.org/10.1073/pnas.96.8.4360