Godoy-Vitorino Filipa, Ruiz-Diaz Claudia P, Rivera-Seda Abigail, Ramírez-Lugo Juan S, Toledo-Hernández Carlos
Department of Natural Sciences, Microbial Ecology and Genomics Lab, Inter American University of Puerto Rico, San Juan, PR, USA.
Department of Environmental Sciences, University of Puerto Rico Rio Piedras Campus, San Juan, PR, USA.
PeerJ. 2017 Aug 29;5:e3717. doi: 10.7717/peerj.3717. eCollection 2017.
Coral reefs are the most biodiverse ecosystems in the marine realm, and they not only contribute a plethora of ecosystem services to other marine organisms, but they also are beneficial to humankind via, for instance, their role as nurseries for commercially important fish species. Corals are considered holobionts (host + symbionts) since they are composed not only of coral polyps, but also algae, other microbial eukaryotes and prokaryotes. In recent years, Caribbean reef corals, including the once-common scleractinian coral , have suffered unprecedented mortality due to climate change-related stressors. Unfortunately, our basic knowledge of the molecular ecophysiology of reef corals, particularly with respect to their complex bacterial microbiota, is currently too poor to project how climate change will affect this species. For instance, we do not know how light influences microbial communities of , arguably the most endangered of all Caribbean coral species. To this end, we characterized the microbiota of inhabiting water depths with different light regimes.
Six fragments from different individuals were collected at two different depths (three at 1.5 m and three at 11 m) from a reef 3.2 km off the northeastern coast of Puerto Rico. We characterized the microbial communities by sequencing the 16S rRNA gene region V4 with the Illumina platform.
A total of 173,137 good-quality sequences were binned into 803 OTUs with a 97% similarity. We uncovered eight bacterial phyla at both depths with a dominance of 725 Rickettsiales OTUs (Proteobacteria). A fewer number (38) of low dominance OTUs varied by depth and taxa enriched in shallow water corals included Proteobacteria (e.g. and ) and Firmicutes (). Those enriched in deeper water corals featured different Proteobacterial taxa (Campylobacterales and Bradyrhizobium) and Firmicutes ().
Our results confirm that the microbiota of inhabiting the northeastern region of Puerto Rico is dominated by a Rickettsiales-like bacterium and that there are significant changes in less dominant taxa at different water depths. These changes in less dominant taxa may potentially impact the coral's physiology, particularly with respect to its ability to respond to future increases in temperature and CO2.
珊瑚礁是海洋领域中生物多样性最为丰富的生态系统，它们不仅为其他海洋生物提供了大量的生态系统服务，还通过例如作为具有商业重要性的鱼类物种的育苗场等作用，对人类有益。珊瑚被视为共生体（宿主+共生体），因为它们不仅由珊瑚虫组成，还包括藻类、其他微生物真核生物和原核生物。近年来，包括曾经常见的石珊瑚在内的加勒比珊瑚礁，由于与气候变化相关的压力因素，遭受了前所未有的死亡率。不幸的是，我们目前对珊瑚礁珊瑚分子生态生理学的基本知识，特别是关于其复杂的细菌微生物群的知识，非常匮乏，以至于无法预测气候变化将如何影响该物种。例如，我们不知道光照如何影响，这可以说是所有加勒比珊瑚物种中最濒危的物种的微生物群落。为此，我们对栖息在不同光照条件下不同水深的的微生物群进行了特征描述。
从波多黎各东北海岸3.2公里外的一个珊瑚礁，在两个不同深度（1.5米处三个，11米处三个）收集了来自不同个体的六个片段。我们通过使用Illumina平台对16S rRNA基因区域V4进行测序来表征微生物群落。
总共173,137个高质量序列被分类为803个操作分类单元，相似度为97%。我们在两个深度都发现了八个细菌门，其中以725个立克次氏体目操作分类单元（变形菌门）占主导。数量较少（38个）的低丰度操作分类单元因深度而异，浅水区珊瑚中富集的分类群包括变形菌门（例如和）和厚壁菌门（）。深水区珊瑚中富集的分类群具有不同的变形菌门分类单元（弯曲菌目和慢生根瘤菌属）和厚壁菌门（）。
我们的结果证实，栖息在波多黎各东北部地区的的微生物群以一种类似立克次氏体的细菌为主导，并且在不同水深的低丰度分类群中存在显著变化。这些低丰度分类群的变化可能会潜在地影响珊瑚的生理机能，特别是其应对未来温度和二氧化碳升高的能力。
