Coral-microbial interactions as determinants of disease dynamics

许多动物和植物宿主的健康取决于其微生物组的组成。虽然宿主的健康往往与有利于致病微生物生长的环境因素有关，但动物和植物微生物组的多样性表明，竞争在决定疾病爆发的频率和严重程度方面起着重要作用。该项目使用濒临灭绝的加勒比鹿角珊瑚作为模型系统，以了解环境和微生物相互作用如何控制白带病（WBD）的传播。白带病是一种细菌性疾病，已导致近95%的加勒比鹿角珊瑚种群死亡。将结合操作实验、实地调查和数学模型来确定水温、珊瑚宿主之间的微生物运动和微生物竞争如何影响WBD的发病率。通过确定WBD的环境和微生物驱动因素，该项目将使管理人员能够(i)预测WBD在空间和时间上的脆弱性热点，以及（ii）确定恢复这些曾经是加勒比珊瑚礁群落重要成员的最佳策略。这项研究将通过交叉训练研究生在珊瑚生物学、微生物遗传学、生物信息学、数学建模、计算机编程和统计学方面的重要社会需求。该项目的成果将整合到遗传学，生态建模和生物统计学的本科课程中，以强调定量和跨学科STEM培训对解决生物学中的重要问题的重要性。最后，将创建一系列互动网络模块，将该项目的成果传播到学术界之外，包括东北大学海洋科学中心K-12外展项目和史密森尼热带研究所在巴拿马的外展项目。越来越多的人认识到，构建微生物群落的过程可能会扩大规模，以解释其宿主的疾病爆发。尽管微生物群落很复杂，但迄今为止大多数研究都集中在解决环境、病原微生物的发生和疾病发病率之间的直接关系上。然而，微生物物种相互作用和扩散对宿主疾病出现的影响在很大程度上仍然未知。该项目将结合微生物遗传学和数学建模，以了解环境、物种相互作用和扩散对微生物群落结构和珊瑚宿主疾病动态的相对影响。本研究以濒临灭绝的加勒比鹿角珊瑚（Acropora cervicornis）和白带病（WBD）为模型宿主-病原体系统。这种曾经占主导地位的造礁珊瑚被世界野生生物保护区大量摧毁，促使其被列为濒危物种。最近对该系统的研究表明：(1)细菌是WBD的病因，(2)生活在宿主体内的微生物群落可以产生抑制致病菌的抗生素化合物，(3)温度升高促进感染并减少抗生素化合物的产生。这些发现表明，环境和宿主相关微生物物种之间的相互作用决定了微生物群落的结构和珊瑚宿主的健康。为了解开这些过程，将进行多因素传播实验，以了解温度、病原体暴露和微生物群落复杂性对疾病动态的直接和间接影响。为了确定这些结果如何扩展到自然珊瑚礁，将对野外调查数据进行空间珊瑚微生物模型的拟合。该拟合模型将阐明季节性温度变化和微生物扩散如何在空间尺度上共同影响珊瑚疾病暴发和珊瑚微生物群落结构。建议的研究将把研究与本科学生的教学和训练结合起来。

The health of numerous animal and plant hosts depends on the composition of their microbiome. Although the health of hosts is often linked to environmental factors that favor the growth of pathogenic microbes, the diversity of animal and plant microbiomes suggests that competition plays an important role in determining the frequency and severity of disease outbreaks. This project uses the endangered Caribbean staghorn coral as a model system to understand how the environment and microbial interactions controls the spread of White Band Disease (WBD), a bacterial disease that has decimated nearly 95% of Caribbean staghorn coral populations. A combination of manipulative experiments, field surveys and mathematical modeling will be used to determine how water temperature, microbial movement between- and microbial competition within coral hosts influence WBD incidence. By identifying the environmental and microbial drivers of WBD, this project will allow managers to (i) predict hotspots of vulnerability to WBD in space and time, and (ii) identify optimal strategies for restoring these once prominent members of Caribbean coral reef communities. This research will address important societal needs by cross-training graduate students in coral biology, microbial genetics, bioinformatics, mathematical modeling, computer programming and statistics. Results of this project will be integrated into undergraduate courses in genetics, ecological modeling and biostatistics in order to emphasize the importance of quantitative and interdisciplinary STEM training for addressing important questions in biology. Finally, a series of interactive web modules will be created to disseminate the results of this project beyond academic circles, including to Northeastern University's Marine Science Center K-12 outreach programs and the Smithsonian Tropical Research Institute's outreach programs in Panama.There is growing recognition that the processes that structure microbial communities may scale up to explain disease outbreaks in their hosts. Despite the complexity of microbial communities, most studies to date have focused on resolving the direct relationship between the environment, the occurrence of pathogenic microbes, and the incidence of disease. However, the effects of microbial species interactions and dispersal on the emergence of host diseases remain largely unknown. This project will combine microbial genetics and mathematical modeling to understand the relative influence of the environment, species interactions and dispersal on the structure of microbial communities and the dynamics of disease in their coral hosts. This research uses the endangered Caribbean staghorn coral (Acropora cervicornis) and White Band Disease (WBD) as a model host-pathogen system. This once dominant, reef-building coral was decimated by WBD, prompting its listing as an endangered species. Recent work in this system suggests that (i) bacteria are the cause of WBD, (ii) the microbial community living within the host can produce antibiotic compounds that suppress pathogenic bacteria, and (iii) temperature increase promotes infection and reduces the production of antibiotic compounds. These findings suggest that the interplay between the environment and host-associated microbial species determines the structure of the microbial community and the health of the coral host. To disentangle these processes, a multi-factorial transmission experiment will be conducted to understand the direct and indirect effects of temperature, pathogen exposure, and microbial community complexity on disease dynamics. To determine how these results scale up to natural coral reefs, a spatial coral-microbial model will be fitted to field survey data. This fitted model will elucidate how seasonal temperature variation and microbial dispersal jointly influence coral disease outbreaks and the structure of coral-microbial communities across spatial scales. The proposed research will integrate research with teaching and training of undergraduate students.