A non-canonical quorum sensing regulator of virulence in Burkholderia pseudomallei

假马利氏伯克氏菌引起类鼻疽感染，目前是泰国东北部第三大死亡原因。由于对抗生素的内在耐药性，类鼻疽病特别难以治疗。尽管类鼻疽病普遍存在，但目前对假假芽孢杆菌的发病机制了解有限。本研究的重点是假芽孢杆菌的毒力调节因子BpsR4。BpsR4是LuxR转录调控家族的一员，参与一种称为群体感应的细菌交流。典型的LuxR蛋白在响应酰基-高丝氨酸内酯（AHL）群体感应信号时诱导靶基因表达。然而，BpsR4诱导毒力基因转录的方式与ahl无关。有趣的是，BpsR4被抗生素（甲氧苄啶和哌拉西林）激活，这些抗生素在转录水平上调节BpsR4。据我们所知，BpsR4是第一个不依赖于ahl的luxr家族保守蛋白，抗生素在激活BpsR4或其他luxr家族蛋白中的作用是完全未知的。虽然BpsR4对秀丽隐杆线虫模型宿主的毒力很重要，但在宿主感染过程中，BpsR4是否诱导毒力基因转录尚不清楚。我们的长期目标是了解luxr家族蛋白如何促进细菌在不同环境下的生存，包括宿主。本应用程序的目的是确定抗生素如何诱导BpsR4转录，以及BpsR4在调节宿主毒力基因表达中的重要性。我们的中心假设是抗生素通过未知的抗生素应答转录调控因子激活BpsR4，并且BpsR4在秀丽隐杆线虫感染期间诱导毒力基因表达。该提案旨在i)鉴定抗生素反应性BpsR4调节因子和ii)评估BpsR4在宿主感染期间诱导毒力基因的作用。由于BpsR4是LuxR家族蛋白的一个新类别，这些研究有望扩展目前LuxR家族的观点。该实验还将为我们提供关键的实验数据，以建立抗生素如何调节BpsR4表达以及BpsR4如何在感染期间促进毒力。这是很重要的，因为这些结果有望增加目前有限的对假假芽孢杆菌如何引起疾病的理解，并可能最终导致控制和治疗类鼻疽病的新策略。

Burkholderia pseudomallei causes melioidosis infections and is currently the third leading cause of death in Northeast Thailand. Melioidosis is particularly difficult to treat due to intrinsic resistance to antibiotics. Despite the prevalence of melioidosis there is currently a limited understanding of B. pseudomallei pathogenesis. This research program is focused on a virulence regulator in B. pseudomallei, BpsR4. BpsR4 is a member of the LuxR family of transcriptional regulators that are involved in a type of bacterial communication called quorum sensing. Typically LuxR proteins induce target gene expression in response to acyl-homoserine lactone (AHL) quorum-sensing signals. However, BpsR4 induces transcription of virulence genes in a manner that is AHL-independent. Interestingly, BpsR4 is activated by antibiotics (trimeothoprim and piperacillin) that regulate BpsR4 at the transcriptional level. To our knowledge BpsR4 is the first conserved LuxR-family protein that is AHL-independent, and the role of antibiotics in activating BpsR4 or other LuxR-family proteins is totally unknown. Although BpsR4 is important for virulence in a C. elegans model host, it is also unknown if BpsR4 induces virulence gene transcription during host infections. Our long-term goal is to understand how LuxR-family proteins promote bacterial survival in different environments, including the host. The objective of this application is to determine how antibiotics induce BpsR4 transcription and the importance of BpsR4 in regulating virulence gene expression in the host. Our central hypothesis is that antibiotics activate BpsR4 through unknown antibiotic-responsive transcriptional regulator(s) and that BpsR4 induces virulence gene expression during C. elegans infection. This proposal aims to i) identify antibiotic-responsive BpsR4 regulators and ii) evaluate BpsR4 induction of virulence genes during host infections. Because BpsR4 is a new class of LuxR-family proteins the studies proposed are expected to expand the current view of the LuxR family. The proposed experiments will also provide us with experimental data critical for building a picture of how antibiotics regulate BpsR4 expression and how BpsR4 promotes virulence during infection. This is significant because the results are expected to increase the currently limited understanding of how B. pseudomallei causes disease, and may ultimately lead to new strategies to control and treat melioidosis.