Collaborative Research: Defining the role of skin microbiomes in defense against chytridiomycosis in frogs with seasonal infections

微生物群是所有生态系统中无处不在的一部分，包括皮肤。尽管“好的”微生物可以抵御病原体的想法被广泛接受，但微生物群落如何在不同的气候条件下为宿主提供好处仍不清楚。这项研究将检查对一种致命的皮肤真菌的防御机制，这种真菌与全球两栖动物的减少有关。这些研究将调查自然皮肤微生物和青蛙免疫之间的联系，以了解疾病结果的季节性变化，使用的是一种可以死于感染但可以在最佳环境条件下生存的青蛙。这个项目解决了疾病易感性和免疫力之间的相互作用，这些物种没有自由生活的蝌蚪阶段，而是直接发育的青蛙。考虑到目前天气模式的变化，季节性预计会随着时间的推移而变化，给宿主-病原体关系增加更多的不稳定性。为了解决皮肤中的微生物如何与对这种病原体的免疫反应相互作用，研究人员将研究自然种群中的青蛙，并进行受控的实验室实验。这一结果将使人们能够更好地预测季节性变化对物种相互作用的影响，这些相互作用可能会影响对新出现疾病的防御。研究人员将开发和传播大学水平的疾病生态学课程的课程材料，该课程整合了从生态学和进化论以及从分子水平到生态系统影响的基本概念。此外，研究人员将与佛罗里达自然历史博物馆合作，开发针对中学生的关于两栖动物疾病生态和微生物群的外展旅游展览。两栖动物在全球范围内受到由树枝状巴氏杆菌引起的一种真菌疾病--合胞菌病的威胁，宿主通常生活在低致病风险和高致病风险的动态循环中。这项提案将把重点放在直接发育的青蛙Eleutherodactylus coqui上，这是一种在野外持续存在的物种，感染受到非生物因素和微生物群落的调节。研究人员将测试宿主免疫防御系统是否通过调节某些细菌成员的存在/不存在来与皮肤微生物群相互作用，进而影响对真菌感染的敏感性。研究人员将组装一组微生物联合体(即具有不同群落结构的假定共生体的分组)，以量化宿主免疫防御，包括野外和实验室中的结构性免疫和适应性反应。该建议包括三个研究目标：1)表征种群水平的皮肤细菌季节性联合体、皮肤分泌物中的免疫防御及其相互作用，2)测试细菌多样性对比背景下宿主防御的重新分布，以及3)测量假定的共生体、宿主皮肤防御和由此产生的病原体负担的生活期变异性。该项目将利用来自宿主防御和微生物分析、微生物组扩增子测序和功能基因组学的个体水平数据来评估反应的时间和大小。通过宿主皮肤防御系统的透镜在不同环境条件下观察到的皮肤微生物群的综合研究将阐明环境、免疫和微生物群在对疾病的抵抗力和耐受性中的作用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Microbiomes are a ubiquitous part of all ecosystems including the skin. Although the idea that “good” microbes can defend against pathogens is widely accepted, it is still unclear how microbial communities provide benefits to the host under variable climates. This research will examine the defense mechanisms against a lethal skin fungus that has been associated with global amphibian declines. The studies will investigate the links between natural skin microbes and frog immunity to understand seasonal changes in disease outcomes using a species of frog that can die of infection but can survive under optimal environmental conditions. This project addresses the interplay between disease susceptibility and immunity for species that do not have a free-living tadpole stage but instead are direct-developing frogs. Considering the current changes in weather patterns, seasonality is expected to shift over time, adding more instability to host-pathogen relationships. To address how microbiomes in skin interact with the immunological response to this pathogen, the researchers will study frogs in natural populations and perform controlled laboratory experiments. The results will allow better predictions about the impact of seasonal variations on species interactions that can influence defense against emerging diseases. The researchers will develop and disseminate course materials for a college-level Disease Ecology course that integrates fundamental concepts from ecology and evolution and from the molecular level to ecosystem impacts. In addition, the researchers will work with the Florida Museum of Natural History to develop outreach travel exhibitions targeted to middle schoolers about amphibian disease ecology and microbiomes. Amphibians are globally threatened by chytridiomycosis, a fungal disease caused by Batrachochytrium dendrobatidis, and hosts often live under dynamic cycles of low and high pathogen risk. This proposal will focus on the direct-developing frog, Eleutherodactylus coqui, a species that persists in the wild with infections modulated by abiotic factors and microbial communities. The researchers will test if host immune defenses interact with skin microbiome by regulating the presence/absence of certain bacterial members, in turn influencing susceptibility to fungal infection. The researchers will assemble sets of microbial consortia (i.e., groupings of putative symbionts with different community structures) to quantify host immune defenses including constitutive immunity and adaptive responses in the field and in the lab. The proposal includes three research objectives: 1) characterize population-level seasonal consortia of skin bacteria, immune defenses in the skin secretions, and their interactions, 2) test for the redistribution of host defenses under contrasting backgrounds of bacterial diversity, and 3) measure life-stage variability in putative symbionts, host skin defenses, and resulting pathogen burden. The project will leverage individual-level data from host defenses and microbiological assays, microbiome amplicon sequencing, and functional genomics to evaluate the timing and magnitude of responses. Integrated studies of skin microbiomes seen through the lens of host skin defenses under different environmental conditions will shed light on the role of the environment, immunity, and microbiome in resistance and tolerance to disease.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.