Sophisticated built-in systems in bacteria release simple chemical compounds to communicate local population density thresholds.

It's taken mankind until the 21st century to create communication systems that enable many individuals to assemble into a large, coordinated group in a relatively short timespan. But take away our mobile phones, Internet connections, and power sources, and we're back to square one. Human beings might look to single-celled organisms for a better way. Bacteria have sophisticated built-in systems that release a relatively simple chemical compound targeted at its brethren. Once enough individuals have gathered, a critical mass of the signaling compound triggers a cascade of chemical processes within each member that results in any one of a number of outcomes such as the formation of disease-causing or corrosive biofilms or bioluminescence.

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

Video content © 2015 - 2006 iBiology · CC BY-NC-ND 3.0 license


"Bacteria are capable of 'communicating' their local population densities via a process termed quorum sensing (QS). Once bacteria reach a sufficiently high population density, they can undergo a lifestyle switch from that of a solitary cell to that of a multicellular group. As a group, bacteria alter gene expression levels and initiate processes that benefit the growing colony. These group behaviours are remarkable in their diversity, and can have significant impacts on their eukaryotic hosts. Examples include the production of virulence factors, swarming, biofilm formation, antibiotic production, bioluminescence, root nodulation, sporulation, and conjugation. Many of these QS-controlled outcomes have widespread and often devastating effects on human health, agriculture, and the environment...Although originally thought to be limited to a small sub-set of bacterial species, it has become clear that QS is a fundamental process of the microbial world. Population dependent, cell–cell communication pathways can be found in both Gram-positive and Gram-negative bacteria, and in fungi." (Geske et al. 2008:1432)

"N-Acylated L-homoserine lactones (AHLs), are the most common signal used by Gram-negative bacteria for cell–cell communication...the basic paradigm for Gram-negative QS: a signal is produced, binding of this signal to a receptor occurs at a threshold concentration, and this receptor complex then regulates (most commonly via activation) the transcription of genes that are involved in bacterial group processes...Over 50 species of Gram-negative bacteria have been shown to use AHLs in their QS signalling networks." (Geske et al. 2008:1434)

Journal article
Expanding dialogues: from natural autoinducers to non-natural analogues that modulate quorum sensing in Gram-negative bacteriaChemical Society ReviewsFebruary 6, 2008
Grant D. Geske, Jennifer C. O’Neill, Helen E. Blackwell

Journal article
Small Molecules That Modulate Quorum Sensing and Control Virulence in Pseudomonas aeruginosaThe Journal of Organic ChemistryFebruary 21, 2017
Margrith E. Mattmann, Helen E. Blackwell