Investigations of an invertebrate secreted immune effector that influences microbial communities of the gut

动物的肠道被各种各样的微生物定殖，最近的研究表明，肠道的微生物群落影响宿主的各种生理过程，从脑功能到发育和肥胖。 因此，了解肠道微生物群落与宿主的相互作用非常重要。 研究人员将使用Ciona robusta（Ciona robusta A型），一种海洋滤食性生物，来研究动物如何使用其免疫系统的元素来调节与喜欢生活在肠道中的微生物的健康相互作用。 由于玻璃海鞘是透明的，它代表了一种独特的模式生物，其中肠道微生物群落可以直接可视化。 Ciona也是一个伟大的教学工具，为学生在课堂上和公众宣传的PI季节性节目，如彼得堡科学节或海洋学营的女孩。 研究人员将利用在受控条件下在实验室饲养的动物，帮助学生了解不同的微生物如何在肠道中定植，并说明动物使用的自然机制，以影响这些微生物在肠道内的位置和方式。Ciona robusta（Ciona robusta A型）是一种无脊椎动物滤食性原脊索动物，将用于研究宿主如何利用先天免疫元素来谈判与肠道微生物组的相互作用。 该提案的重点是可变免疫球蛋白样几丁质结合蛋白（VCBPs）。 VCBP是双功能的; N-末端IG结构域识别细菌，C-末端结构域结合几丁质。 VCBPs是理解肠道微生物组中细菌、真菌和病毒之间复杂对话的关键。 这些蛋白质由玻璃海鞘中的肠上皮以高丰度表达和分泌，并且表现出类似于脊椎动物伊加的功能，包括调节细菌粘附和在粘膜表面上形成生物膜。 初步数据显示，当VCBP-C与一些溶原细胞结合时，观察到原噬菌体的诱导，这是一个塑造生物膜形成结果的过程，并可能影响可能被新释放的噬菌体靶向的其他细菌的生长。 各种细菌和真菌分离物，来自玻璃海鞘的肠道，已经培养，现在将在体外和体内利用无菌动物进行研究。 该项目通过体外和体内实验的结合，将研究VCBP-C和肠道培养分离株（细菌和真菌）之间的相互作用;然后，我们将研究体外（细菌）生物膜形成和无菌动物定植的转录组，以帮助表征定植的遗传学。 作为多功能蛋白质，VCBP可能在微生物组的细菌和真菌群落之间建立相互作用的桥梁;并且由于VCBP影响原噬菌体的诱导，在初步观察中已显示具有广泛的宿主范围，因此这些病毒的激活可能会重新塑造微生物组的组成。 Ciona模型提供了一个独特的机会来研究先天免疫如何不仅保护免受病原体的侵害，而且还调节微生物生态以实现和维持稳态。 Ciona将继续作为一个平台，进一步探索免疫进化不仅是为了“防御”，而且是为了“调节肠道微生物生态”的假设。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The gut of animals is colonized by a rich assortment of microbes and recent research has demonstrated that microbial communities of the gut influence all kinds of physiological processes of the host, from brain function, to development, and obesity. Hence, understanding the interplay of microbial gut communities and the host is highly important. The investigators will use Ciona robusta (Ciona intestinalis type A), a marine filter-feeding organism, to investigate how animals use elements of their immune system to regulate healthy interactions with microbes that like to live in the gut. As Ciona is transparent, it represents a unique model organism in which gut microbial communities can be visualized directly. Ciona also is a great teaching tool for students in the classroom and for public outreach in the PIs seasonal programs like the St. Petersburg Science Festival or the Oceanography Camp for Girls. The investigators will utilize animals reared in the lab under controlled conditions to help students understand how distinct microbes colonize the gut, and illustrate natural mechanisms used by animals to influence where and how these microbes settle within the gut. Ciona robusta (Ciona intestinalis type A), an invertebrate filter-feeding protochordate, will be used to investigate how the host utilizes elements of innate immunity to negotiate interactions with the gut microbiome. The proposal focuses on variable immunoglobulin-like chitin-binding proteins (VCBPs). VCBPs are bifunctional; the N-terminal Ig domains recognize bacteria and the C-terminal domain binds chitin. VCBPs are a key to understanding complex dialogues between bacteria, fungi and viruses of the gut microbiome. These proteins are expressed and secreted in high abundance by the gut epithelium in Ciona, and exhibit functions that resemble vertebrate IgA, including the modulation of bacterial adherence and formation of biofilms on mucosal surfaces. Preliminary data reveal that when VCBP-C binds to some lysogens, induction of prophages is observed, a process that shapes the outcome of biofilm formation and may impact the growth of other bacteria that may be targeted by the newly released phages. Various bacterial and fungal isolates, derived from the gut of Ciona, have been cultured and will now be studied both in vitro and in vivo utilizing germ-free animals. This project, via a combination of in vitro and in vivo experiments, will examine the interaction between VCBP-C and cultured isolates (bacterial and fungal) of the gut; we will then examine transcriptomes of in vitro (bacterial) biofilm formation and colonization of germ-free animals to help characterize the genetics of colonization. As multi-functional proteins, the VCBPs likely bridge interactions between bacterial and fungal communities of the microbiome; and because VCBPs influence the induction of prophages, which in preliminary observations have been shown to possess broad host ranges, it is likely that activation of these viruses can re-shape the composition of the microbiome. The Ciona model presents a unique opportunity to study how innate immunity not only protects against pathogens but also modulates microbial ecology to achieve and maintain homeostasis. Ciona will continue to serve as a platform to further explore the hypothesis that immunity evolved not just to "defend" but to "modulate microbial ecology" of the gut lumen.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.