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. Author manuscript; available in PMC: 2012 Nov 9.
Published in final edited form as: Mol Microbiol. 2012 Jan 9;83(3):599–611. doi: 10.1111/j.1365-2958.2011.07959.x

Figure 1. Model for Qrr sRNA regulation of aphA, luxR/hapR, and luxO.

Figure 1

At low cell density, phospho-LuxO activates expression of the qrr genes encoding the Qrr sRNAs. The Qrr sRNAs promote translation of the low cell density master regulator AphA and inhibit translation of the high cell density master regulator LuxR/HapR. At high cell density, Qrr sRNA production ceases because dephosphorylated LuxO is inactive. AphA translation stops and LuxR/HapR translation occurs. LuxO production is repressed by the Qrr sRNAs in a negative feedback loop. AphA and LuxR repress each other at transcriptional level.