Veillonellae:Keystone species in biofilm development

描述（由申请人提供）：这项R21资助申请旨在了解引发牙龈炎症所需的最早事件，最终目标是了解牙周炎发展的完整过程。牙周病，尤其是牙周炎，影响着大多数65岁及以上的人，是这一人群牙齿脱落的主要原因。牙周炎的发展涉及从健康牙龈到牙龈炎（牙龈炎症）再到牙周炎（进行性牙周组织破坏和牙槽骨丢失）的一系列转变。已经确定牙周炎是由牙龈下微生物群和宿主之间的生态失调相互作用引起的。已发现具核假单胞菌（Fn）与牙龈炎有关，而牙龈假单胞菌（Pg）被认为是牙周炎的“关键病原体”，因为它已被证明会引发功能失调的宿主反应，并影响牙龈下微生物群的群落生态。虽然我们对牙周炎的发病机制有充分的了解，但我们对发生在龈上菌斑上的最早事件一无所知，而这些事件为疾病的未来发展奠定了基础。根据体外和体内研究的结果，我们假设细孔菌（Va）通过允许牙周病病原体的定植和生长，在早期生物膜（龈上斑块）发育中充当关键物种，并通过这样做使生物膜生态向疾病倾斜。我们使用了一个3种模型，其中具核梭菌（Fn）代表牙龈炎病原体，Pg代表牙周病原体，可转化菌株V. atypica OK5代表Va。在Aim 1中，我们将检验Va产生维生素K和血红素的假设，这是Fn和Pg的两种必需营养素。通过与Fn和Pg共聚集，维生素K和血红素生物合成基因的表达被诱导或上调。在Aim 2中，我们将确定Va与Fn和Pg共聚集的机制。通过我们最近在细孔菌中开发的第一个也是唯一一个可处理的转化系统，完成这些目标成为可能。

DESCRIPTION (provided by applicant): This R21 grant application aims to understand the earliest events required to initiate gingival inflammation, with an ultimate goal of understanding the complete process of periodontitis development. Periodontal diseases especially periodontitis affect the majority of people 65 years and older, and is the major cause of tooth loss in this population. Development of periodontitis involves a serial transition from healthy gum to gingivitis (gum inflammation) to periodontitis (progressive periodontal tissue destruction and alveolar bone loss). It has been well established that periodontitis results from dysbiotic interaction between the subgingival microbiota and the host. F. nucleatum (Fn) has been found to be associated with gingivitis, while P. gingivalis (Pg) is considered a "keystone pathogen" in periodontitis as it has been shown to trigger dysfunctional host response as well as to influence community ecology of the subgingival microbiota. Although we have ample knowledge about the pathogenesis mechanisms of periodontitis, we know nothing about the earliest events happening in the supragingival plaque that set the stage for future development of disease. Based on findings from both in vitro and in vivo studies, we hypothesize that Veillonella (Va) serves as keystone species in early biofilm (supragingival plaque) development by allowing colonization and growth of periodontopathogens, and that by doing so skews biofilm ecology towards disease. A 3-species model is used, with F. nucleatum (Fn) representing gingivitis pathogen, Pg representing periodontal pathogen, and the transformable strain V. atypica OK5 representing Va. In Aim 1 we will test the hypothesis that Va produces vitamin K and heme, two essential nutrients for Fn and Pg, and that expression of the vitamin K and heme biosynthesis genes is induced or upregulated by coaggregation with Fn and Pg. In Aim 2 we will determine the mechanism of coaggregation between Va and Fn and Pg. Completion of these aims is made possible by our recent development of the first and only tractable transformation system in Veillonella.