Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of Washingtongrid.34477.33, Seattle, Washington, USA.
Department of Microbiology, University of Washingtongrid.34477.33, Seattle, Washington, USA.
mSystems. 2022 Apr 26;7(2):e0011322. doi: 10.1128/msystems.00113-22. Epub 2022 Apr 11.
In people with the genetic disease cystic fibrosis (CF), bacterial infections involving the opportunistic pathogen Pseudomonas aeruginosa are a significant cause of morbidity and mortality. P. aeruginosa uses a cell-cell signaling mechanism called quorum sensing (QS) to regulate many virulence functions. One type of QS consists of acyl-homoserine lactone (AHL) signals produced by LuxI-type signal synthases, which bind a cognate LuxR-type transcription factor. In laboratory strains and conditions, P. aeruginosa employs two AHL synthase/receptor pairs arranged in a hierarchy, with the LasI/R system controlling the RhlI/R system and many downstream virulence factors. However, P. aeruginosa isolates with inactivating mutations in are frequently isolated from chronic CF infections. We and others have shown that these isolates frequently use RhlR as the primary QS regulator. RhlR is rarely mutated in CF and environmental settings. We were interested in determining whether there were reproducible genetic characteristics of these isolates and whether there was a central group of genes regulated by RhlR in all isolates. We examined five isolates and found signatures of adaptation common to CF isolates. We did not identify a common genetic mechanism to explain the switch from Las- to Rhl-dominated QS. We describe a core RhlR regulon encompassing 20 genes encoding 7 products. These results suggest a key group of QS-regulated factors important for pathogenesis of chronic infections and position RhlR as a target for anti-QS therapeutics. Our work underscores the need to sample a diversity of isolates to understand QS beyond what has been described in laboratory strains. The bacterial pathogen Pseudomonas aeruginosa can cause chronic infections that are resistant to treatment in immunocompromised individuals. Over the course of these infections, the original infecting organism adapts to the host environment. P. aeruginosa uses a cell-cell signaling mechanism termed quorum sensing (QS) to regulate virulence factors and cooperative behaviors. The key QS regulator in laboratory strains, LasR, is frequently mutated in infection-adapted isolates, leaving another transcription factor, RhlR, in control of QS gene regulation. Such isolates provide an opportunity to understand Rhl-QS regulation without the confounding effects of LasR, as well as the scope of QS in the context of within-host evolution. We show that a core group of virulence genes is regulated by RhlR in a variety of infection-adapted LasR-null isolates. Our results reveal commonalities in infection-adapted QS gene regulation and key QS factors that may serve as therapeutic targets in the future.
在患有囊性纤维化（CF）这种遗传性疾病的人群中，机会性病原体铜绿假单胞菌（P. aeruginosa）引起的细菌感染是发病率和死亡率的重要原因。铜绿假单胞菌利用一种称为群体感应（QS）的细胞间信号机制来调节许多毒力功能。QS 由酰基高丝氨酸内酯（AHL）信号组成，由 LuxI 型信号合成酶产生，与同源 LuxR 型转录因子结合。在实验室菌株和条件下，铜绿假单胞菌采用由两个 AHL 合成酶/受体对组成的层次结构，LasI/R 系统控制 RhlI/R 系统和许多下游毒力因子。然而，经常从慢性 CF 感染中分离出携带 基因失活突变的铜绿假单胞菌分离株。我们和其他人已经表明，这些分离株经常使用 RhlR 作为主要的 QS 调节剂。在 CF 和环境环境中，RhlR 很少发生突变。我们有兴趣确定这些分离株是否具有可重复的遗传特征，以及是否所有分离株中都存在由 RhlR 调节的核心基因群。我们检查了五个分离株，发现了与 CF 分离株常见的适应特征。我们没有发现解释从 Las 到 Rhl 主导的 QS 转变的常见遗传机制。我们描述了一个核心的 RhlR 调控组，包含 20 个基因，编码 7 种产物。这些结果表明，一组重要的 QS 调节因子与慢性感染的发病机制有关，并将 RhlR 作为抗 QS 治疗的靶标。我们的工作强调需要对多样性的分离株进行采样，以了解实验室菌株之外的 QS。铜绿假单胞菌是一种细菌病原体，可导致免疫功能低下个体的慢性感染，且治疗效果不佳。在这些感染过程中，最初的感染病原体适应宿主环境。铜绿假单胞菌使用一种称为群体感应（QS）的细胞间信号机制来调节毒力因子和合作行为。实验室菌株中的关键 QS 调节剂 LasR 在感染适应分离株中经常发生突变，使另一个转录因子 RhlR 控制 QS 基因调控。这种分离株提供了一个在不受到 LasR 干扰的情况下理解 Rhl-QS 调节的机会，以及在宿主内进化背景下 QS 的范围。我们表明，一组核心毒力基因在各种感染适应的 LasR 缺失分离株中受 RhlR 调节。我们的结果揭示了感染适应的 QS 基因调控和关键 QS 因子的共同性，这些因子可能成为未来的治疗靶点。
