Collaborative Research: Host-environment-pathogen interactions in a model coral disease system

海洋生物疾病已成为导致全世界珊瑚礁资源减少的一个严重问题。珊瑚礁栖息地的丧失具有社会和经济影响，特别是在夏威夷等依赖珊瑚礁提供食物、海岸线保护和旅游业的岛国。由于缺乏对哪些环境变量影响疾病、宿主防御机制以及许多已描述的珊瑚疾病的病因的了解，我们管理珊瑚疾病的能力受到了阻碍。这个项目的PI发现了一个珊瑚疾病系统，可以作为一个模型来探索疾病病因的宿主-环境-病原体三角的许多组成部分。白色单孢子虫综合征(MWS)是一种传染性疾病，导致头状单孢子虫群体进行性组织丢失，已在夏威夷群岛的珊瑚礁上发现。它在瓦胡岛的卡内奥赫湾特别流行，那里的水质长期下降，这种次优的环境为宿主和病原体的相互作用奠定了基础。在卡尼奥赫湾，头藻是一种主要的造礁物种，有两种颜色的变种(红色和橙色)，它们含有不同的虫黄藻分支。在初步调查中，PI发现了种内差异对颜色变体之间的MWS的响应。虽然红色在调查样带中占主导地位(80%的菌落)，但橙色的菌落受到MWS的不成比例的影响(70%的受影响的菌落)。微生物研究发现，受MWS影响的和健康的头根结线虫上的细菌群落发生了变化，从而能够识别潜在的病原体。对大量的细菌菌株进行了培养和致病性筛选，其中3株产生病斑的菌株被鉴定为潜在的病原菌。两种可能的病原体(Vibrio spp.)产生弥漫组织，而另一株细菌(假交替单胞菌sp.)造成了严重的组织丢失。在现场，PI还观察到了头根结线虫的两种组织丢失模式：一种缓慢、慢性的组织丢失模式，他们通过标记的菌落(慢性MWS)来跟踪这种模式，但也观察到了快速发生的急性组织丢失(ALICAL MWS)。因此，他们发现了一种传染性珊瑚疾病，这种疾病会导致显著的珊瑚死亡，而这种疾病的独特成分是不同颜色的珊瑚之间疾病易感性的差异。PIS确定了三种潜在的细菌病原体，将用于调查影响珊瑚-环境-病原体三重致病因素的潜在因素。夏威夷海洋生物研究所(HIMB)位于卡内奥赫湾，全年都可以进入珊瑚礁进行白色蒙蒂孢菌综合症的研究。本项目的目的是研究白色单孢菌综合征的寄主-环境-病原体三角致病因素。这项研究的目的是：1)研究红色(较不敏感)和橙色(较敏感)的头状根结线虫的不同抗病机制。PIS将比较两种颜色形态的头状结核的全息菌、粘液和粘液相关细菌的抗菌活性，并将比较两种颜色形态之间的自然珊瑚相关微生物群；2)使用操纵性水族馆研究来确定环境胁迫(高温、营养胁迫)是否对红色与橙色形态的头状结核MWS的进展或传播效率产生不同的影响；3)使用挑战性实验来确认细菌病原体作为MWS的病原体的作用；以及确定红色与橙色形态的头状结核对三种可能的病原体的反应。该项目将包括一个多学科小组，以提供对珊瑚疾病过程的更广泛的视角。这将是第一次在夏威夷进行的关于珊瑚疾病的综合研究。更广泛的影响和研究/教育的整合将包括夏威夷大学和密西西比大学的研究生和本科生的多学科实践研究经验。这两所大学都有不同的学生群体和大量的少数民族学生。这位密歇根大学的研究生还将有机会为夏威夷的实地考察工作做出贡献。来自该项目的信息将被纳入西瓦胡岛大学的普通生物学课程和加州大学马诺阿分校的微生物学课程，这两门课程都是为夏威夷原住民和太平洋岛民服务的。该项目将为来自太平洋岛屿的本科生提供机会，通过由威斯康星大学赞助的本科生研究指导(URM)计划体验研究。K-12教育将包括将这些成果整合到参加每年夏天通过HIMB协调的高中生PACE/B-WEAM夏季环境科学计划的高中生的班级中。它还将用于通过针对高危青年的环境科学项目--河额纳鲁--对学生进行培训。在密西西比州，公众将通过墨西哥湾中央海洋科学教育卓越中心(COSEE)和J.L.斯科特海洋教育中心获得信息。

Diseases of marine organisms have emerged as a serious problem contributing to the decline of coral reef resources worldwide. Loss of coral reef habitats carry social and economic implications especially in island states, such as Hawaii, which depend on reefs for food, shoreline protection and tourism. Our ability to manage coral diseases is hampered by a lack of knowledge of which environmental variables affect disease, mechanisms of host defense, and the etiology of most of the numerous described coral diseases. The PIs of this project discovered a coral disease system that can be used as a model to explore many components of the host-environment-pathogen triangle of disease causation. Montipora white syndrome (MWS) is an infectious disease that results in progressive tissue loss on colonies of Montipora capitata, and has been found on reefs throughout the Hawaiian archipelago. It is particularly prevalent in Kaneohe Bay, Oahu, which has a long history of reduced water quality, and this suboptimal environment sets the stage where host-pathogen interactions occur. In Kaneohe Bay, M. capitata is a major reef-building species, and is found in two color morphs (red and orange) that harbor different clades of zooxanthellae. During preliminary surveys, the PIs discovered intraspecific variability in response to MWS between color morphs. Although the red morph was dominant within survey transects (80% of the colonies), the orange morph was disproportionately affected by MWS (70% of the affected colonies). Microbial studies found a shift in bacterial communities on MWS-affected and healthy M. capitata and allowed identification of potential pathogens. Numerous bacterial strains were cultured and screened for pathogenicity and three strains, which produced lesions, were identified as potential pathogens. Two of the putative pathogens (Vibrio spp.) produced diffuse tissue whereas the other bacterial strain (Pseudoalteromonas sp.) produced acute tissue loss. In the field, the PIs also observed two patterns of tissue loss on M. capitata; a slow, chronic pattern of tissue loss, which they followed through time with tagged colonies (chronic MWS), but also a rapid onset of acute tissue loss (acute MWS). Thus they discovered an infectious coral disease that results in significant coral mortality that has the unique component of differences in disease susceptibility among color morphs. The PIs identified three potential bacterial pathogens that will be used to investigate underlying factors affecting the coral-environment-pathogen triad of disease causation. The Hawaii Institute of Marine Biology (HIMB) is located within Kaneohe Bay allowing year-round access to reefs for research on Montipora white syndrome. The goal of this project is to investigate the host- environment-pathogen triangle of disease causation for Montipora white syndrome. The objectives of this research will be to: 1) investigate mechanisms contributing to differential disease resistance in red (less susceptible) vs. orange (more susceptible) morphs of M. capitata. The PIs will compare antimicrobial activity in the holobiont, mucus and mucus-associated bacteria of the two color morphs of M. capitata, and will compare the natural coral-associated microbial flora between the two color morphs; 2) use manipulative aquarium studies to determine whether environmental stressors (elevated temperature, nutrient stress) differentially affect the progression or transmission efficiency of MWS in red vs. orange morphs of M. capitata; 3) use challenge experiments to confirm the role of bacterial pathogens as causative agents of MWS, and to determine the response of red vs. orange morphs of M. capitata to three putative pathogens. This project will involve a multidisciplinary team to provide a broader perspective of coral disease processes. This will be the first comprehensive study conducted on a coral disease in Hawaii.Broader impacts and integration of research/education will consist of multidisciplinary, hands-on research experiences for graduate and undergraduate students from the University of Hawaii and the University of Mississippi. Both universities have diverse student bodies and large complements of minority students. The UM graduate student will also have the opportunity to contribute to the fieldwork in Hawaii. Information from this project will be integrated into general biology classes at UH West Oahu and microbiology classes at UH Manoa, both of which serve native Hawaiians and Pacific Islanders. This project will provide opportunities for undergraduate students from Pacific Islands to experience research through the Undergraduate Research Mentoring (URM) program sponsored at UH. K-12 education will include integration of these results into classes for high school students participating in the PaCES/B-WET Summer Environmental Science Program for high school students coordinated through HIMB each summer. It will also be used for training students through the He'e Nalu, an environmental science program for at-risk youth. In Mississippi, the public will be informed through the Central Gulf of Mexico Center for Ocean Sciences Education Excellence (COSEE) and J.L. Scott Marine Education Center.