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

项目摘要：共生菌群（生活在多细胞生物体上或多细胞生物体中的微生物群落）是多细胞生物体健康的重要参与者。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的疾病易感性的差异有关。相比之下，对非人类动物或植物的微生物区系知之甚少。本研究评估了共生菌群如何影响山地黄腿蛙的抗病性。 先前的研究结果表明，这些青蛙皮肤上发现的微生物群落的差异与壶菌病严重程度的变化有关，壶菌病是一种皮肤疾病，由真菌病原体Batrachochytrium dendrobatim感染引起。 目前的研究调查的原因，负责这些模式的实验操纵微生物群落生活在皮肤上的R。随后将青蛙暴露于B。dendrobaetin，并测量所产生的疾病进展。 这个实验解决了三个问题：（1）哪些因素控制着构成正常微生物群落的微生物的身份？ (2)微生物区系物种组成的差异是否影响青蛙抵抗B感染的能力？树枝虫？(3)当被B.如果真的发生了树枝状芽孢杆菌病，它是否会扰乱共生的微生物群落，导致构成正常微生物群落的微生物物种发生变化？ 研究结果将促进对共生微生物群落形成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：世界范围内的两栖动物正在经历大规模的减少和灭绝，壶菌病是这些动物的最大威胁之一。 本研究对壶菌病的防治和两栖动物的保护具有一定的参考价值。目前正在进行实验室和现场试验，以测试使用益生菌来保护两栖动物免受疾病的影响，但有关受威胁两栖动物自然存在的共生群落及其抗病功能的基本知识有限。这些知识将通过本研究得到提高。 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.