From making vitamins to digesting our food to inflicting us with debilitating diseases, bacteria are busy. How do these single-celled microbes pull it off? The answer lies in part with quorum sensing – a molecular communication system that Bonnie Bassler studies in her lab. Bacterial cells use quorum sensing to count themselves, determine when they have reached an optimal density, and adjust their behavior synchronously for tasks that require many cells working together. For example, when virulent bacteria invade a host organism, they wait until their numbers exceed a critical mass before secreting toxins. Timing is key. If bacteria release these toxins too soon, they risk getting wiped out by the host immune system.
Although she first observed quorum sensing in a bioluminescent marine bacterium called Vibrio harveyi, Bassler has since shown that the communication system is used widely among diverse bacterial species. Species-specific and genera-specific molecules called autoinducers transmit the bacterial messages, and Bassler and her team have identified small RNAs and other molecules that help cells respond. The researchers also discovered that a molecule named AI-2 allows cross-species conversations, and that hundreds of bacterial species use the AI-2 molecule to communicate, suggesting the existence of a universal bacterial language.
Hoping to inspire development of new microbial therapies, Bassler’s team has designed anti-quorum-sensing molecules to stymie the signals of pathogenic bacteria, as well as pro-quorum-sensing molecules to enhance communication by beneficial bugs. And, since bacteria are among the oldest organisms on Earth, studying their communication strategies could also help researchers understand fundamental mechanisms of signal transduction and information processing at the level of multicellular organisms and populations.
This work is supported in part by the National Institutes of Health and the National Science Foundation.