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. Author manuscript; available in PMC: 2017 Feb 11.
Published in final edited form as: Nat Rev Microbiol. 2016 Aug 11;14(9):576–588. doi: 10.1038/nrmicro.2016.89

Figure 5. Feedback loops control Vibrio harveyi quorum sensing dynamics.

Figure 5

Six different feedback loops are embedded in the Vibrio harveyi quorum sensing circuit. a | LuxO autorepresses its own transcription. b | The quorum regulatory small RNAs (Qrr sRNAs) inhibit luxO translation by mRNA target sequestration. c | LuxR activates qrr transcription. The Qrr sRNAs, in turn, inhibit the production of LuxR by catalytic degradation of the luxR mRNA. d | LuxR represses its own transcription. e | AphA and LuxR reciprocally repress each other’s transcription. f | Base pairing of the Qrr sRNAs with the luxMN mRNA facilitates degradation of the RNA duplex (coupled degradation). The arrows denote activation. Inhibitory arrows denote repression. Grey arrows indicate post-transcriptional regulation. All of these feedback loops except the Qrr-to-luxMN loop also exist in Vibrio cholerae. In V. cholerae, LuxR is known as HapR. HAI-1, 3OH-C4-homoserine lactone; RNAP, RNA polymerase.