TY - JOUR

T1 - A negative feedback loop involving small RNAs accelerates Vibrio cholerae'stransition out of quorum-sensing mode

AU - Svenningsen, Sine Lo

PY - 2008

Y1 - 2008

N2 - Quorum sensing is a cell-to-cell communication process that allows bacteria tomeasure their population numbers and to synchronously alter gene expression inresponse to changes in cell population density. At the core of the Vibriocholerae quorum-sensing signal transduction pathway lie four redundant small RNAs(sRNAs), named the Quorum Regulatory RNAs (Qrr1-4). Expression of qrr1-4 is cell population density-dependent due to a requirement for the quorum-sensingcontrolled phosphorylated response regulator LuxO-P, which is abundant only atlow cell population density. When expressed, Qrr1-4 repress translation of HapR, the "master" quorum-sensing transcription factor. Here we show a negativefeedback loop in which HapR activates transcription of the qrr genes, whichindirectly leads to hapR repression. Efficient feedback activation of the qrrgenes requires the simultaneous presence of LuxO-P (present only at low cellpopulation density) and HapR (present only at high cell population density). For this reason, the feedback loop does not influence quorum sensing at steady-state low or high cell population density. However, LuxO-P and HapR are simultaneously present immediately following the switch from high to low cell densityconditions. In this state, the HapR feedback loop dramatically accelerates V.cholerae's transition from the high to the low cell density mode.

AB - Quorum sensing is a cell-to-cell communication process that allows bacteria tomeasure their population numbers and to synchronously alter gene expression inresponse to changes in cell population density. At the core of the Vibriocholerae quorum-sensing signal transduction pathway lie four redundant small RNAs(sRNAs), named the Quorum Regulatory RNAs (Qrr1-4). Expression of qrr1-4 is cell population density-dependent due to a requirement for the quorum-sensingcontrolled phosphorylated response regulator LuxO-P, which is abundant only atlow cell population density. When expressed, Qrr1-4 repress translation of HapR, the "master" quorum-sensing transcription factor. Here we show a negativefeedback loop in which HapR activates transcription of the qrr genes, whichindirectly leads to hapR repression. Efficient feedback activation of the qrrgenes requires the simultaneous presence of LuxO-P (present only at low cellpopulation density) and HapR (present only at high cell population density). For this reason, the feedback loop does not influence quorum sensing at steady-state low or high cell population density. However, LuxO-P and HapR are simultaneously present immediately following the switch from high to low cell densityconditions. In this state, the HapR feedback loop dramatically accelerates V.cholerae's transition from the high to the low cell density mode.

M3 - Journal article

VL - 22

SP - 226

EP - 238

JO - Genes & Development

JF - Genes & Development

SN - 0890-9369

IS - 2

ER -