The Black Sea is the largest brackish water body in the world, although it is connected to the Mediterranean Sea and presents an upper water layer similar to some regions of the former, albeit with lower salinity and temperature. Despite its well-known hydrology and physicochemical features, this enormous water mass remains poorly studied at the microbial genomics level. We have sampled its different water masses and analyzed the microbiome by shotgun and genome-resolved metagenomics, generating a large number of metagenome-assembled genomes (MAGs) from them. We found various similarities with previously described Black Sea metagenomic datasets, that show remarkable stability in its microbiome. Our datasets are also comparable to other marine anoxic water columns like the Cariaco Basin. The oxic zone resembles to standard marine (e.g. Mediterranean) photic zones, with Cyanobacteria (Synechococcus but a conspicuously absent Prochlorococcus), and photoheterotrophs domination (largely again with marine relatives). The chemocline presents very different characteristics from the oxic surface with many examples of chemolithotrophic metabolism (Thioglobus) and facultatively anaerobic microbes. The euxinic anaerobic zone presents, as expected, features in common with the bottom of meromictic lakes with a massive dominance of sulfate reduction as energy-generating metabolism, a few (but detectable) methanogenesis marker genes, and a large number of “dark matter” streamlined genomes of largely unpredictable ecology. The Black Sea oxic zone presents many similarities to the global ocean while the redoxcline and euxinic water masses have similarities to other similar aquatic environments of marine (Cariaco Basin or other Black Sea regions) or freshwater (meromictic monimolimnion strata) origin. The MAG collection represents very well the different types of metabolisms expected in this kind of environment. We are adding critical information about this unique and important ecosystem and its microbiome.

中文翻译：

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用shot弹枪和以基因组为中心的宏基因组学分析了黑海水柱的微生物组

尽管黑海与地中海相连，但黑海是世界上最大的微咸水域，尽管其盐度和温度较低，但黑海的上部水层与前者的某些区域相似。尽管其众所周知的水文学和理化特征，但在微生物基因组学水平上仍无法对这种巨大的水团进行研究。我们已经采样了其不同的水团，并通过shot弹枪和基因组解析的宏基因组学对微生物组进行了分析，从而从中生成了大量由元基因组组装的基因组（MAGs）。我们发现了与先前描述的黑海宏基因组数据集的各种相似之处，这些相似之处显示了其微生物组的显着稳定性。我们的数据集也可与其他海洋缺氧水柱（如Cariaco盆地）相媲美。含氧区类似于标准海洋（例如 地中海）光合带，蓝藻（Synechococcus，但明显不存在Prochlorococcus）和光异养类（主要是海洋亲属）。化学趋化因子的表现形式与有氧表面非常不同，其中有许多化学趋化性代谢（硫球菌）和兼性厌氧微生物的例子。如预期的那样，常氧厌氧区呈现出与淡紫色湖泊底部相同的特征，其中大量硫酸盐还原占主导地位，产生能量代谢，少数（但可检测）产甲烷标记基因，以及大量“暗物质”简化了很大程度上不可预测的生态的基因组。黑海含氧区与全球海洋有许多相似之处，而氧化还原线和安息性水团与海洋（Cariaco盆地或其他黑海地区）或淡水（Meromictic monimolimnion地层）起源的其他类似水生环境具有相似之处。MAG集合很好地代表了这种环境中预期的不同类型的新陈代谢。我们正在添加有关这个独特而重要的生态系统及其微生物组的重要信息。