In ancient times, persons suffering from a dreaded disease believed to be contagious, such as leprosy, were given a bell to ring and thus noisily announce their presence. Healthy people could then move away and try to avoid contact.  Amazingly, bacteria use an analogous strategy. A recent Journal of Bacteriology paper from Siryaporn’s lab at the University of California at Irvine and others discloses that when Pseudomonas aeruginosa is exposed to phages or an antibiotic, it emits a signal that stops unaffected cells from moving and potentially entering a danger zone where they would be exposed to unamicable conditions.
The signal is obviously not the sound of a bell but a secreted chemical that is detected by the neighboring unaffected bacteria. The chemical is a compound called PQS (for

Credit: Janice Haney Carr CDC

Quinolone Signal, or 2-heptyl-3-hydroxy-4-quinolone), and therein lies the tale.

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