Bacteria are social organisms - they communicate in a process called "quorum sensing" to orchestrate group behaviors. Quorum sensing relies on the production, detection, and response to the extracellular accumulation of signaling molecules called autoinducers. Often, bacteria use multiple autoinducers to obtain information about the local cell density, and use this information to regulate gene expression. A striking feature of the quorum-sensing network in the bacterium V. harveyi is the large number of feedbacks loops. To learn what these feedbacks are doing, we used single-cell microscopy to quantify the autoinducer input-output relation for a variety of feedback mutants. Feedbacks extend the input dynamic range, compress the output dynamic range, and allow cells to "focus" on different autoinducers at different levels of signaling. We speculate that the use of multiple autoinducers and feedbacks allows a growing population of cells to synchronize gene expression during a series of distinct developmental stages.

Getting together: What can enzyme clustering do for metabolism?