Molecular Regulation of Choanoflagellate-Bacteria Signaling Interactions

描述（由申请人提供）：动物生活和进化在一个充满微生物的世界；因此，动物与细菌的联系，从致病的到互惠的，是古老而普遍的。由于缺乏实验可处理和系统发育相关的研究模型，对真核生物细菌信号传导机制和进化的理解进展受到限制。我们的实验室已经发现，长鞭毛虫Salpingoeca rosetta的多细胞菌落的发育是由一种来自细菌Algoriphagus sp的化学信号调节的。阐明这种信号相互作用的分子机制有望为细菌共生体和动物之间的发育信号提供重要的见解，因为(1)长鞭毛虫是动物的近亲；(2)拟杆菌门细菌；海藻菌是其中的一员，在动物肠道的微生物群中占主导地位，在那里它们对发育、健康和疾病产生影响。我们提出了三个目的来确定食藻菌分子信号传导的机制及其对鞭藻群落发育的调控。首先，我们将与Clardy实验室（哈佛医学院）合作，从不同的细菌中分离出菌落诱导化合物，确定它们的结构，并结合有机化学和生物合成基因的经典遗传操作来进行结构/功能分析。其次，我们将通过标记细菌诱导剂和可视化信号传递动力学来定义细菌和鞭毛藻之间的信号接口。第三，我们将使用生化和候选基因方法鉴定细菌信号分子的鞭藻受体。这项研究有可能揭示涉及王国间信号传导的实际机制，这将使我们能够研究现代宿主-细菌相互作用的演变。

DESCRIPTION (provided by applicant): Animals live and evolved in a world teeming with microbes; as a result, animal- bacterial associations, ranging from pathogenic to mutualistic, are ancient and ubiquitous. Progress toward understanding mechanisms and evolution of bacterial signaling with eukaryotes has been limited by the paucity of experimentally tractable and phylogenetically relevant research models. Our lab has discovered that the development of multicelled colonies in the choanoflagellate Salpingoeca rosetta is regulated by a chemical signal from the bacterium Algoriphagus sp. Elucidating the molecular mechanisms underlying this signaling interaction promises to provide important insights into developmental signaling between bacterial symbionts and animals because (1) choanoflagellates are the closest living relatives of animals and (2) Bacteroidetes bacteria, of which Algoriphagus is a member, predominate the microbiomes of animal intestines, where they exert influences on development, health, and disease. We propose three aims to determine the mechanisms underlying molecular signaling by Algoriphagus bacteria and its regulation of choanoflagellate colony development. First, in collaboration with the Clardy lab (Harvard Medical School) we will isolate colony-inducing compounds from diverse bacteria, determine their structures and use a combination of organic chemistry and classical genetic manipulations of biosynthetic genes to perform structure/function analyses. Second, we will define the signaling interface between bacteria and choanoflagellates by tagging the bacterial inducer and visualizing dynamics of signal delivery. Third, we will identify the choanoflagellate receptor(s) for bacterial signaling molecules using biochemical and candidate gene approaches. This research has the potential to uncover the actual mechanisms involved in inter-kingdom signaling which will allow us to examine the evolution of modern host- bacterial interactions.