Streptococcal secretion of pyruvate - a novel antioxidant strategy in the oral biofilm

项目摘要 共生链球菌在口腔生物膜内环境稳定中起重要作用。生物膜扰动 稳态导致生态失调，并最终导致疾病发展，包括龋齿和 牙周病几种口腔链球菌产生大量的H2 O2， 抑制与疾病发展有关的易感致病菌。然而，H2 O2的产生 并不总是与生产者的拮抗能力相关。我们组最近 确定了这一观察结果背后的机制：口腔链球菌分泌中心代谢物 丙酮酸作为有效的H2 O2清除剂。丙酮酸分泌作为氧化应激的机制 已经报道了真核细胞的应答，但尚未在原核生物中进行研究， 通常对原核丙酮酸转运知之甚少。我们的观察发现 关于口腔链球菌作用的生态学问题：为什么一些 链球菌H2 O2生产者分泌保护量的丙酮酸和其他不？是什么 这种能力的基因基础对口腔健康有什么影响？以下具体 目的是确定和表征丙酮酸分泌机制及其遗传 口腔链球菌对照： 目的一：明确丙酮酸的分泌机制及其特异性调控。我们将确定 通过组合转座子诱变丙酮酸分泌所需的遗传组分 进行基因筛查这些基因的调控将被比较 物种之间。目的研究不同的链球菌如何调节H2 O2/丙酮酸 平衡是口腔微生物生态学的关键。 目的II：表征决定H2 O2/丙酮酸平衡的调控网络。我们 将在低和高丙酮酸分泌条件下进行ChIP-seq（CCR+/-）以识别 这条通路的关键调控成分。这也将作为一种独立的方法， 确定丙酮酸分泌机制。 进一步了解链球菌群落如何调节其H2 O2/丙酮酸 平衡将有助于确定疾病发展的分子决定因素， 疾病预防的新目标。

Project Summary Commensal streptococci play an important role in oral biofilm homeostasis. Disturbance of biofilm homeostasis leads to dysbiosis and eventually disease development, including caries and periodontal disease. Several oral streptococci are producing significant amounts of H2O2 able to inhibit susceptible pathobionts involved in disease development. However, the production of H2O2 does not always correlate with the antagonistic ability of the producer. Our group recently identified the mechanism behind this observation: oral streptococci secrete the central metabolite pyruvate as potent H2O2 scavenger. The mechanism of pyruvate secretion as oxidative stress response has been reported for eukaryotic cells, but has not been investigated in prokaryotes and little is known about prokaryotic pyruvate transport in general. Our observation raises key ecological questions about the role of commensal streptococci in the oral cavity: why do some streptococcal H2O2 producers secrete protective amounts of pyruvate and others do not? What is the genetic basis for this ability? What are the implications for oral health? The following specific aims are proposed to identify and characterize the pyruvate secretion mechanism and its genetic control in oral streptococci: Aim I: Identify the pyruvate secretion mechanism and its specific regulation. We will identify the genetic components required for pyruvate secretion by combining transposon mutagenesis with an established genetic screening protocol. The regulation of these genes will be compared between species. Aim I will determine how different streptococci modulate the H2O2/pyruvate balance that is critical for oral microbial ecology. Aim II: Characterize the regulatory network that determines the H2O2/pyruvate balance. We will perform ChIP-seq (CCR+/-) under conditions of low and high pyruvate secretion to identify the key regulatory components of this pathway. This will also serve as independent approach to identify the pyruvate secretion mechanism. An improved understanding of how the streptococcal community regulates its H2O2/pyruvate balance will help to define the molecular determinates of disease development and provide a novel target for disease prevention.