Kashtan Nadav, Roggensack Sara E, Berta-Thompson Jessie W, Grinberg Maor, Stepanauskas Ramunas, Chisholm Sallie W
Department of Plant Pathology and Microbiology, The Hebrew University of Jerusalem, Rehovot, Israel.
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
ISME J. 2017 Sep;11(9):1997-2011. doi: 10.1038/ismej.2017.64. Epub 2017 May 19.
The Atlantic and Pacific Oceans represent different biogeochemical regimes in which the abundant marine cyanobacterium Prochlorococcus thrives. We have shown that Prochlorococcus populations in the Atlantic are composed of hundreds of genomically, and likely ecologically, distinct coexisting subpopulations with distinct genomic backbones. Here we ask if differences in the ecology and selection pressures between the Atlantic and Pacific are reflected in the diversity and genomic composition of their indigenous Prochlorococcus populations. We applied large-scale single-cell genomics and compared the cell-by-cell genomic composition of wild populations of co-occurring cells from samples from Station ALOHA off Hawaii, and from Bermuda Atlantic Time Series Station off Bermuda. We reveal fundamental differences in diversity and genomic structure of populations between the sites. The Pacific populations are more diverse than those in the Atlantic, composed of significantly more coexisting subpopulations and lacking dominant subpopulations. Prochlorococcus from the two sites seem to be composed of mostly non-overlapping distinct sets of subpopulations with different genomic backbones-likely reflecting different sets of ocean-specific micro-niches. Furthermore, phylogenetically closely related strains carry ocean-associated nutrient acquisition genes likely reflecting differences in major selection pressures between the oceans. This differential selection, along with geographic separation, clearly has a significant role in shaping these populations.
大西洋和太平洋代表着不同的生物地球化学区域，丰富的海洋蓝细菌原绿球藻在其中蓬勃生长。我们已经表明，大西洋中的原绿球藻群体由数百个在基因组上可能在生态上也不同的共存亚群体组成，这些亚群体具有不同的基因组主干。在这里，我们要问的是，大西洋和太平洋之间生态和选择压力的差异是否反映在其本土原绿球藻群体的多样性和基因组组成上。我们应用大规模单细胞基因组学，比较了来自夏威夷附近的阿洛哈站（Station ALOHA）以及百慕大附近的百慕大大西洋时间序列站（Bermuda Atlantic Time Series Station）样本中同时出现的细胞野生群体的逐个细胞基因组组成。我们揭示了不同地点群体在多样性和基因组结构上的根本差异。太平洋群体比大西洋群体更多样化，由更多共存亚群体组成且缺乏优势亚群体。来自这两个地点的原绿球藻似乎主要由具有不同基因组主干的不重叠的不同亚群体集合组成，这可能反映了不同的海洋特定微生态位集合。此外，系统发育上密切相关的菌株携带与海洋相关的养分获取基因，这可能反映了不同海洋之间主要选择压力的差异。这种差异选择，连同地理隔离，显然在塑造这些群体方面发挥了重要作用。
