Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA.
Genes Dev. 2011 Feb 15;25(4):397-408. doi: 10.1101/gad.2015011.
Bacteria cycle between periods when they perform individual behaviors and periods when they perform group behaviors. These transitions are controlled by a cell-cell communication process called quorum sensing, in which extracellular signal molecules, called autoinducers (AIs), are released, accumulate, and are synchronously detected by a group of bacteria. AI detection results in community-wide changes in gene expression, enabling bacteria to collectively execute behaviors such as bioluminescence, biofilm formation, and virulence factor production. In this study, we show that the transcription factor AphA is a master regulator of quorum sensing that operates at low cell density (LCD) in Vibrio harveyi and Vibrio cholerae. In contrast, LuxR (V. harveyi)/HapR (V. cholerae) is the master regulator that operates at high cell density (HCD). At LCD, redundant small noncoding RNAs (sRNAs) activate production of AphA, and AphA and the sRNAs repress production of LuxR/HapR. Conversely, at HCD, LuxR/HapR represses aphA. This network architecture ensures maximal AphA production at LCD and maximal LuxR/HapR production at HCD. Microarray analyses reveal that 300 genes are regulated by AphA at LCD in V. harveyi, a subset of which is also controlled by LuxR. We propose that reciprocal gradients of AphA and LuxR/HapR establish the quorum-sensing LCD and HCD gene expression patterns, respectively.
细菌在执行个体行为和群体行为的时期之间循环。这些转变由一种称为群体感应的细胞间通讯过程控制，其中细胞外信号分子，称为自诱导物（AIs），被释放、积累并被一群细菌同步检测。AI 检测导致全社区基因表达的变化，使细菌能够集体执行生物发光、生物膜形成和毒力因子产生等行为。在这项研究中，我们表明转录因子 AphA 是 Vibrio harveyi 和 Vibrio cholerae 中低细胞密度（LCD）下群体感应的主要调节剂。相比之下，LuxR（V. harveyi）/HapR（V. cholerae）是在高细胞密度（HCD）下运作的主要调节剂。在 LCD 时，冗余的小非编码 RNA（sRNA）激活 AphA 的产生，AphA 和 sRNA 抑制 LuxR/HapR 的产生。相反，在 HCD 时，LuxR/HapR 抑制 aphA。这种网络架构确保了在 LCD 时最大程度地产生 AphA，在 HCD 时最大程度地产生 LuxR/HapR。微阵列分析显示，在 V. harveyi 中，有 300 个基因在 AphA 在 LCD 下被调控，其中一部分也受到 LuxR 的控制。我们提出，AphA 和 LuxR/HapR 的相互梯度分别建立了群体感应的 LCD 和 HCD 基因表达模式。
