Metabolite sensing in an oral polymicrobial community

描述(申请人提供)：病原体在人体内的生存已被严格研究了一个多世纪。由于一系列的能力，细菌能够在体内定居、持久和茁壮成长。大多数细菌发病机制的研究都集中在单一培养感染上；然而，很明显，许多细菌感染并不是单一物种定居的简单结果，而是多个物种定居的结果。多菌感染中的微生物通常表现出协同作用，导致感染部位的定植和持久性增强，而控制这些协同作用的分子过程还没有很好的定义。我们的实验室利用两物种模型系统来研究多菌种的协同作用。该系统由条件革兰氏阴性病原菌Aggregatibacter放线菌(Aa)和革兰氏阳性菌戈登链球菌(Sg)组成。使用这一模型系统，我们正在测试压倒一切的假设，即多菌感染中的细菌对微生物群落其他成员产生的主要代谢物表现出明确的反应，而这些反应对确定多菌感染至关重要。我们主要集中在阐明AA对L产生的两种主要代谢物-乳酸和H_2O_2的分子反应。这些研究发现了新的AA反应，这些反应不仅影响这种细菌与Sg的相互作用，也影响它与宿主的相互作用。这项研究计划的总体目标是1)从机械的角度检查口腔细菌之间的多微生物相互作用如何影响群落发展、对宿主天然免疫的抵抗力和体内持久性，以及2)开发新的技术来探索多微生物相互作用。为此，我们提出了以下实验：(1)阐明AA-L偏爱乳酸的分子机制并评估其在体内的重要性；(2)阐明AA在共培养过程中保护天然免疫的机制并评估其在体内的重要性；(3)表征H_2O_2和共培养对生物膜分散的影响。 与公共卫生相关：大多数细菌在自然界中不是作为单一培养物存在的，而是作为复杂的群落存在的，在这些群落中，细菌物种之间的相互作用影响着个人和群落的命运。该项目的目标是研究人类口腔的两种机会性病原体之间的相互作用，并确定这些相互作用如何增强这些细菌对免疫系统杀死的抵抗力。这项研究对疾病有直接影响，因为多个微生物相互作用对病原体在人体内生存的重要性尚未进行深入调查。

DESCRIPTION (provided by applicant): The survival of pathogens in the human body has been rigorously studied for well over a century. Bacteria are able to colonize, persist and thrive in vivo due to an array of capabilities. Most bacterial pathogenesis studies have focused on mono-culture infections; however, it is clear that many bacterial infections are not simply the result of colonization with a single species, but are instead a result of colonization with several. Microbes within polymicrobial infections often display synergistic interactions that result in enhanced colonization and persistence in the infection site, and the molecular processes controlling these synergistic interactions are not well defined. Our lab utilizes a two-species model system to study polymicrobial synergy. The system is composed of the opportunistic Gram-negative pathogen Aggregatibacter actinomycetemcomitans (Aa) and the Gram-positive bacterium Streptococcus gordonii (Sg). Using this model system, we are testing the overriding hypothesis that bacteria within polymicrobial infections display defined responses to the primary metabolites produced by other members of the microbial community, and these responses are critical for establishing polymicrobial infections. We have primarily focused on elucidating the molecular responses of Aa to two primary metabolites produced by Sg, L-lactate and H2O2. These studies have uncovered novel Aa responses that not only affect how this bacterium interacts with Sg but also how it interacts with the host. The overall goals of this research plan are to 1) examine from a mechanistic standpoint, how polymicrobial interactions between oral bacteria impact community development, resistance to host innate immunity, and in vivo persistence, and 2) develop novel technologies for probing polymicrobial interactions. To this end, we have proposed experiments to (i) elucidate the molecular mechanism of Aa L-lactate preference and assess its importance in vivo, (ii) elucidate the mechanism of Aa protection from innate immunity during co-culture and assess its importance in vivo, (iii) characterize the impact of H2O2 and co-culture on biofilm dispersion. PUBLIC HEALTH RELEVANCE: Most bacteria do not exist in nature as monocultures, but instead as complex communities in which interactions between bacterial species affect the fate of the individual as well as the community. The goal of this project is to examine interactions between two opportunistic pathogens of the human mouth and define how these interactions enhance resistance of these bacteria to killing by the immune system. This research has direct consequences for disease as the importance of polymicrobial interactions for pathogen survival in the human body has not been investigated in depth.