Bacterial cell-cell signalling, or quorum sensing, is characterized by the secretion and groupwide detection of small diffusible signal molecules called autoinducers. This mechanism allows cells to coordinate their behaviour in a density-dependent manner. A quorum-sensing cell may directly respond to the autoinducers it produces in a cell-autonomous and quorum-independent manner, but the strength of this self-sensing effect and its impact on bacterial physiology are unclear. Here, we explore the existence and impact of self-sensing in the Bacillus subtilis ComQXP and Rap-Phr quorum-sensing systems. By comparing the quorum-sensing response of autoinducer-secreting and non-secreting cells in co-culture, we find that secreting cells consistently show a stronger response than non-secreting cells. Combining genetic and quantitative analyses, we demonstrate this effect to be a direct result of self-sensing and rule out an indirect regulatory effect of the autoinducer production genes on response sensitivity. In addition, self-sensing in the ComQXP system affects persistence to antibiotic treatment. Together, these findings indicate the existence of self-sensing in the two most common designs of quorum-sensing systems of Gram-positive bacteria.

中文翻译：

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枯草芽孢杆菌群体感应系统中的自我感应。

细菌细胞间信号传递或群体感应的特征在于分泌并在全组范围内检测称为自动诱导剂的小扩散信号分子。该机制允许细胞以依赖于密度的方式协调其行为。群体感应细胞可能以细胞自主和群体独立的方式直接响应其产生的自诱导物，但这种自我感应作用的强度及其对细菌生理的影响尚不清楚。在这里，我们探讨了枯草芽孢杆菌ComQXP和Rap-Phr群体感应系统中自我感应的存在和影响。通过比较共培养中自动分泌型和非分泌型细胞的群体感应反应，我们发现分泌型细胞始终比非分泌型细胞显示出更强的响应。结合遗传和定量分析，我们证明这种作用是自我感觉的直接结果，并排除了自动诱导物生产基因对响应敏感性的间接调节作用。此外，ComQXP系统中的自我感应会影响对抗生素治疗的持久性。总之，这些发现表明在革兰氏阳性菌群体感应系统的两个最常见设计中都存在自我感应。