Dissertation Research: Associations between Symbiotic Bacterial Communities and Infection by an Emerging Fungal Pathogen: Distinguishing Cause from Correlation

项目概述：共生菌群（生活在多细胞生物表面或体内的微生物群落）是多细胞生物健康的重要参与者。居住在人体内的微生物种类的变化与从肥胖到沙门氏菌病等疾病的易感性差异有关。相比之下，人们对非人类动物或植物的微生物群知之甚少。本研究评估了共生菌群如何影响山黄腿蛙（Rana sierrae）的抗病能力。先前的研究结果表明，在这些青蛙的皮肤上发现的微生物群落的差异与壶菌病的严重程度的变化有关，壶菌病是一种由真菌病原体水蛭壶菌感染引起的皮肤疾病。目前的研究通过实验操纵生活在sierra r.s rae皮肤上的微生物群落，随后将青蛙暴露于B. dendroatidis，并测量由此产生的疾病进展，来调查这些模式的原因。该实验解决了三个问题：(1)哪些因素控制构成正常微生物群的微生物的特性？(2)微生物群落种类组成的差异是否会影响蛙类抵抗树突线虫感染的能力？(3)当树突双歧杆菌感染时，是否会扰乱共生微生物群落，导致构成正常菌群的微生物种类发生变化？结果将促进对形成共生微生物群落的因素及其在健康和疾病中的重要性的基本理解。更广泛的影响：全世界的两栖动物正在经历大规模的减少和灭绝，壶菌病是对这些动物最大的威胁之一。本研究对壶菌病的防治和两栖动物的保护具有重要意义。目前正在进行实验室和实地试验，以测试使用益生菌来保护两栖动物免受疾病的侵害，但关于在受威胁的两栖动物身上自然存在的共生群落及其在抗病方面的功能的基本知识有限。这些知识将通过本研究得到完善。此外，该项目为研究生和本科生助理提供了一个重要的培训机会，他们将通过全面参与研究获得研究经验。

Project Summary: Symbiotic microflora (communities of microbes living on or in multicellular organisms) are important players in the health of multicellular organisms. Variation in the microbial species inhabiting the human body has been linked to differences in susceptibility to diseases from obesity to salmonellosis. In contrast, little is known about the microflora of non-human animals or plants. This study assesses how symbiotic microflora affect disease resistance in the mountain yellow-legged frog (Rana sierrae). Previous results show that differences in the microbial communities found on the skin of these frogs are linked to variation in the severity of chytridiomycosis, a disease of the skin that results from infection by the fungal pathogen, Batrachochytrium dendrobatidis. The current study investigates the causes responsible for these patterns by experimentally manipulating the microbial communities living on the skin of R. sierrae, subsequently exposing frogs to B. dendrobatidis, and measuring resulting disease progression. This experiment addresses three questions: (1) Which factors control the identity of microbes that make up the normal microflora? (2) Do differences in the species composition of the microflora affect the ability of the frogs to resist infection by B. dendrobatidis? (3) When infection by B. dendrobatidis does occur, does it disturb the symbiotic microbial community, leading to changes in the microbial species that make up the normal microflora? Results will advance fundamental understanding of the factors shaping symbiotic microbial communities and their importance in health and disease. Broader impacts: Amphibians worldwide are undergoing mass declines and extinctions, and chytridiomycosis is one of the greatest threats to these animals. This study is relevant to the management of chytridiomycosis and the conservation of amphibians. Laboratory and field trials are currently underway to test the use of probiotic bacteria to protect amphibians from the disease, yet basic knowledge about the symbiotic communities naturally occurring on threatened amphibians and their function in disease resistance is limited. Such knowledge will be improved by this study. In addition, this project provides a critical training opportunity for the graduate student and for an undergraduate assistant who will gain research experience through integral participation in the study.