Auburn University, Department of Biological Sciences, Auburn, Alabama, USA.
Appl Environ Microbiol. 2012 Sep;78(18):6438-49. doi: 10.1128/AEM.01162-12. Epub 2012 Jul 6.
Scleractinian corals harbor microorganisms that form dynamic associations with the coral host and exhibit substantial genetic and ecological diversity. Microbial associates may provide defense against pathogens and serve as bioindicators of changing environmental conditions. Here we describe the bacterial assemblages associated with two of the most common and phylogenetically divergent reef-building corals in the Caribbean, Montastraea faveolata and Porites astreoides. Contrasting life history strategies and disease susceptibilities indicate potential differences in their microbiota and immune function that may in part drive changes in the composition of coral reef communities. The ribotype structure and diversity of coral-associated bacteria within the surface mucosal layer (SML) of healthy corals were assessed using denaturing gradient gel electrophoresis (DGGE) fingerprinting and 454 bar-coded pyrosequencing. Corals were sampled at disparate Caribbean locations representing various levels of anthropogenic impact. We demonstrate here that M. faveolata and P. astreoides harbor distinct, host-specific bacteria but that specificity varies by species and site. P. astreoides generally hosts a bacterial assemblage of low diversity that is largely dominated by one bacterial genus, Endozoicomonas, within the order Oceanospirillales. The bacterial assemblages associated with M. faveolata are significantly more diverse and exhibit higher specificity at the family level than P. astreoides assemblages. Both corals have more bacterial diversity and higher abundances of disease-related bacteria at sites closer to the mainland than at those furthest away. The most diverse bacterial taxa and highest relative abundance of disease-associated bacteria were seen for corals near St. Thomas, U.S. Virgin Islands (USVI) (2.5 km from shore), and the least diverse taxa and lowest relative abundance were seen for corals near our most pristine site in Belize (20 km from shore). We conclude that the two coral species studied harbor distinct bacterial assemblages within the SML, but the degree to which each species maintains specific microbial associations varies both within each site and across large spatial scales. The taxonomic scale (i.e., phylum versus genus) at which scientists examine coral-microbe associations, in addition to host-elicited factors and environmental fluctuations, must be considered carefully in future studies of the coral holobiont.
石珊瑚体内栖息着与珊瑚宿主形成动态联系的微生物，具有丰富的遗传和生态多样性。微生物共生体可能为珊瑚提供防御机制，并作为环境变化的生物指标。本研究描述了加勒比地区两种最常见且系统发育差异最大的造礁石珊瑚——牡蛎珊瑚（Montastraea faveolata）和星盘珊瑚（Porites astreoides）体内的细菌组合。对比其不同的生活史策略和疾病易感性，表明它们的微生物组和免疫功能可能存在差异，而这可能部分导致珊瑚礁群落组成的变化。采用变性梯度凝胶电泳（DGGE）指纹图谱和 454 焦磷酸测序技术，评估了健康珊瑚表面黏膜层（SML）中珊瑚相关细菌的核糖体结构和多样性。在代表不同人为影响水平的加勒比不同地点对珊瑚进行了采样。本研究表明，牡蛎珊瑚和星盘珊瑚体内存在独特的、宿主特异性的细菌，但这种特异性因物种和地点而异。星盘珊瑚体内的细菌多样性较低，主要由海洋螺旋菌目（Oceanospirillales）中的一个细菌属——内共生单胞菌属（Endozoicomonas）主导。与牡蛎珊瑚相关的细菌组合在科水平上的多样性和特异性明显高于星盘珊瑚。与离大陆较远的地点相比，靠近大陆的地点的珊瑚具有更多的细菌多样性和更高的疾病相关细菌丰度。在美属维尔京群岛（U.S. Virgin Islands，USVI）圣托马斯附近（离海岸 2.5 公里）的珊瑚中，发现了最多样的细菌类群和最高相对丰度的疾病相关细菌，而在伯利兹最原始的地点（离海岸 20 公里）附近的珊瑚中，发现了最少样的细菌类群和最低相对丰度的疾病相关细菌。综上所述，本研究中研究的两种珊瑚在 SML 内都有独特的细菌组合，但每种珊瑚维持特定微生物共生体的程度在每个地点和大的空间尺度上都有所不同。在未来对珊瑚整体生物群的研究中，必须仔细考虑科学家检查珊瑚-微生物共生关系的分类学尺度（即门与属），以及宿主诱发因素和环境波动。
