Marine Synechococcus isolates representing globally abundant genomic lineages demonstrate a unique evolutionary path of genome reduction without a decrease in GC content
Marine Synechococcus isolates representing globally abundant genomic lineages demonstrate a unique evolutionary path of genome reduction without a decrease in GC content
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DOI：
10.1111/1462-2920.14552
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发表时间：
2019-05-01
影响因子：
5.1
通讯作者：
Webb, Eric A.
中科院分区：
文献类型：
--
作者：
Lee, Michael D.;Ahlgren, Nathan A.;Webb, Eric A.
聚囊球菌是一种单细胞蓝藻属，遍布全球海洋表面，是地球碳循环的主要驱动力。更好地了解其多样性和分布是生物海洋学的一项持续努力。在这里，我们引入了12个新的海洋聚囊球菌分离物的基因组草案，跨越5个分支，并利用类似的100个环境宏基因组，主要来自TARA海洋项目，以评估它们和其他参考基因组所代表的基因组谱系的全球分布。我们发现五个新提供的枝型ii分离株是迄今为止恢复的原位种群中最具代表性的（最“丰富”），并且具有与以前可用的枝型ii参考文献不同的生物地理分布。此外，这些分离物形成了一个亚枝，拥有该属中已知的最小基因组（2.14 +/- 0.05Mbps；平均+/- 1SD），同时拥有一些最高的GC含量（60.67 +/- 0.16%）。这与聚珠球菌最近的亲戚原绿球藻的模式直接相反，原绿球藻基因组大小的减少与GC含量的强烈减少是一致的，这表明这个新的聚珠球菌亚枝相对于该属的其他部分似乎已经收敛地经历了基因组的减少，但沿着一个根本不同的进化轨迹。
Synechococcus, a genus of unicellular cyanobacteria found throughout the global surface ocean, is a large driver of Earth's carbon cycle. Developing a better understanding of its diversity and distributions is an ongoing effort in biological oceanography. Here, we introduce 12 new draft genomes of marine Synechococcus isolates spanning five clades and utilize similar to 100 environmental metagenomes largely sourced from the TARA Oceans project to assess the global distributions of the genomic lineages they and other reference genomes represent. We show that five newly provided clade-II isolates are by far the most representative of the recovered in situ populations (most 'abundant') and have biogeographic distributions distinct from previously available clade-II references. Additionally, these isolates form a subclade possessing the smallest genomes yet identified of the genus (2.14 +/- 0.05Mbps; mean +/- 1SD) while concurrently hosting some of the highest GC contents (60.67 +/- 0.16%). This is in direct opposition to the pattern in Synechococcus's nearest relative, Prochlorococcus - wherein decreasing genome size has coincided with a strong decrease in GC content - suggesting this new subclade of Synechococcus appears to have convergently undergone genomic reduction relative to the rest of the genus, but along a fundamentally different evolutionary trajectory.