Probing Respiration and Metabolism of a Periodontal Pathogen

项目摘要 牙周炎是一种高度流行的疾病，影响着近一半的美国成年人，如果不治疗，会导致 到骨丢失和组织损伤[1]。多种微生物与这种疾病有关[2，3]，并通过 化学介导的相互作用在牙周缝隙内形成复杂的物种间群落。由于 由于这些化学作用的复杂性，牙周炎仍然是一种难以治疗的疾病。努力 使用多种微生物群落[4，5]和动物模型[5，6]探索了可能的化学相互作用 极大地促进了我们对牙周炎过程中发生的化学相互作用的理解。在 我们使用了一个由戈登链球菌(Sg)为代表的两种群模型系统 革兰氏阳性链球菌，能够消耗糖和产酸，如L-乳酸 产生过氧化氢(H_2O_2)和革兰氏阴性放线菌(AA) 与侵袭性牙周炎有关的口腔病原体。此前，我们已经证明，当在联合培养中生长时， 在培养过程中，Sg与AA交叉喂养其首选的碳源L-乳酸，同时额外提供社交线索H_2O_2 从而增强了AA[7-9]的适应度。通过交叉喂养L-乳酸，生长缓慢的AA能够更好地 在多菌环境中竞争。此外，过氧化氢通过刺激产生起到了提示的作用。 保护AA免受补体杀死的补体因子Apia的作用[4]，并诱导产生 蛋白质分散素B允许AA控制其空间定位[9]。除了这些健身好处外，我们还 基于先前数据的假设，Sg产生的过氧化氢也是AA的O2的直接来源 通过过氧化氢酶介导的解毒作用[8]。而L-乳酸和过氧化氢已被证明提供了重要的 氨基酸的代谢线索，最近的基因组研究表明，可能存在额外的化学相互作用 在共同感染期间这些细菌之间发生[8，10]。我们的假设是AA显示定义了 对Sg的响应对于在微米尺度上建立精确的空间结构生物膜至关重要。 该项目的第一个目标是测试AA可以利用过氧化氢解毒产生的O2作为 AA与Sg共培养时呼吸作用的变化以及H_2O_2如何影响空间 结构。在第二个目标中，我们将使用质谱学来全面了解 Aa和Sg之间发生的化学作用。这些研究的结果将提供直接的见解 通过过氧化氢解毒，AA获得的额外好处的潜在过程。通过识别 Aa和Sg之间未知的化学相互作用，可以更好地理解复杂的物种间 与牙周炎有关的相互作用。

Project Summary Periodontitis is a highly prevalent disease affecting nearly half of all American adults, and if left untreated leads to bone loss and tissue damage [1]. Multiple microbes are associated with this disease [2, 3] and through chemically-mediated interactions form complex interspecies communities within the periodontal crevice. Due to the complexity of these chemically-mediated interactions, periodontitis remains a difficult disease to treat. Efforts using polymicrobial communities [4, 5] and animal models [5, 6] have explored possible chemical interactions and have greatly advanced our understanding of the chemical interactions occurring during periodontitis. In the Whiteley lab we use a two-species model system composed of Streptococci gordonii (Sg), a representative Gram-positive streptococcal species capable of consuming sugars and producing acids such as L-lactate as well as producing hydrogen peroxide (H2O2), and Aggregatibacter actinomycetemcommitans (Aa), a Gram-negative oral pathogen associated with aggressive periodontitis. Previously, we have shown that when grown in co- culture, Sg cross-feeds Aa its preferred carbon source, L-lactate, while additionally providing the social cue H2O2 thereby enhancing the fitness of Aa [7-9]. By being cross-fed L-lactate, the slow-growing Aa is able to better compete within a polymicrobial environment. Furthermore, H2O2 serves as a cue by stimulating the production of the complement factor ApiA that protects Aa from complement killing [4], and induces the production of the protein Dispersin B that allows Aa to control its spatial localization [9]. In addition to these fitness benefits, we also hypothesize based on previous data that Sg-produced H2O2 also serves as a direct source of O2 for Aa through catalase mediated detoxification [8]. While L-lactate and H2O2 have been shown to provide important metabolic cues for Aa, recent genomic work indicates that there are likely additional chemical interactions occurring between these bacteria during co-infection [8, 10]. Our hypothesis is that Aa displays defined responses to Sg that are critical to establishing precise spatially structured biofilms at the micron scale. The first objective of the project is to test the hypothesis that Aa can use O2 derived from H2O2 detoxification as evidenced by a shift in respiration when Aa is grown in co-culture with Sg, and how H2O2 impacts spatial structure. In the second objective we will use mass spectrometry to develop a comprehensive understanding of the chemical interactions occurring between Aa and Sg. The results from these studies will provide direct insight into the processes underlying the additional benefits Aa receives through H2O2 detoxification. By identifying the unknown chemical interactions between Aa and Sg, we can better understand the complex interspecies interactions involved in periodontitis.