Geographical structure of endosymbiotic bacteria hosted by Bathymodiolus mussels at eastern Pacific hydrothermal vents.
Geographical structure of endosymbiotic bacteria hosted by Bathymodiolus mussels at eastern Pacific hydrothermal vents.
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DOI：
10.1186/s12862-017-0966-3
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发表时间：
2017-05-30
影响因子：
3.4
通讯作者：
Won YJ
中科院分区：
文献类型：
--
作者：
Ho PT;Park E;Hong SG;Kim EH;Kim K;Jang SJ;Vrijenhoek RC;Won YJ
化学自养初级生产在深海热液喷口和碳氢化合物渗漏处维持密集的无脊椎动物群落。氧化溶解的硫、甲烷和氢气的共生细菌滋养着在世界各地这些环境中茁壮成长的深海变种贻贝。贻贝的共生体是在每一代中通过自由生活的形式感染而获得的。这项研究考察了生活在东太平洋热液喷口的贝类寄主的硫营养型内共生体的地理细分。从东太平洋海隆、加拉帕戈斯裂谷和太平洋-南极海脊的9个喷口采集了共生体16S核糖体RNA编码基因和6个蛋白质编码基因片段的高通量测序数据。这两个毗邻的姐妹种，嗜热杆菌和南极杆菌，都拥有相同的数量优势型的硫代嗜热伽马蛋白细菌。然而，来自六个蛋白质编码基因的序列显示出高度不同的共生体谱系，分布在复活节微板的北部和南部，由这两个贝类贻贝寄生。同一地点采集的寄主个体之间共生体单倍型的高度异质性表明，随着共生体在寄主个体内的增殖，与初始感染相关的随机性被放大。目前，贻贝物种彼此接触，并沿着复活节微板进行杂交，但北部和南部的共生体似乎完全孤立。与250万-530万年前复活节微盘地区造山作用有关的更替可能导致了共生体和宿主种群的分离。这项研究中检测的编码蛋白质的细菌基因的同义替换率估计为0.77-1.62%/核苷酸/百万年。我们的研究报告了迄今为止基于高通量遗传数据和广泛的地理采样对化学合成内共生细菌进行的最全面的种群遗传分析，并证明了地理特征、复活节微板和地理距离在该细菌物种沿东太平洋中脊轴线的种内差异中所起的作用。总之，我们的结果提供了对东太平洋热液喷口中化学合成共生伙伴扩散和演化的外在和内在因素的洞察。本文的在线版本(doi：10.1186/s12862-0170966-3)包含补充材料，授权用户可以使用。
Chemolithoautotrophic primary production sustains dense invertebrate communities at deep-sea hydrothermal vents and hydrocarbon seeps. Symbiotic bacteria that oxidize dissolved sulfur, methane, and hydrogen gases nourish bathymodiolin mussels that thrive in these environments worldwide. The mussel symbionts are newly acquired in each generation via infection by free-living forms. This study examined geographical subdivision of the thiotrophic endosymbionts hosted by Bathymodiolus mussels living along the eastern Pacific hydrothermal vents. High-throughput sequencing data of 16S ribosomal RNA encoding gene and fragments of six protein-coding genes of symbionts were examined in the samples collected from nine vent localities at the East Pacific Rise, Galápagos Rift, and Pacific-Antarctic Ridge. Both of the parapatric sister-species, B. thermophilus and B. antarcticus, hosted the same numerically dominant phylotype of thiotrophic Gammaproteobacteria. However, sequences from six protein-coding genes revealed highly divergent symbiont lineages living north and south of the Easter Microplate and hosted by these two Bathymodiolus mussel species. High heterogeneity of symbiont haplotypes among host individuals sampled from the same location suggested that stochasticity associated with initial infections was amplified as symbionts proliferated within the host individuals. The mussel species presently contact one another and hybridize along the Easter Microplate, but the northern and southern symbionts appear to be completely isolated. Vicariance associated with orogeny of the Easter Microplate region, 2.5–5.3 million years ago, may have initiated isolation of the symbiont and host populations. Estimates of synonymous substitution rates for the protein-coding bacterial genes examined in this study were 0.77–1.62%/nucleotide/million years. Our present study reports the most comprehensive population genetic analyses of the chemosynthetic endosymbiotic bacteria based on high-throughput genetic data and extensive geographical sampling to date, and demonstrates the role of the geographical features, the Easter Microplate and geographical distance, in the intraspecific divergence of this bacterial species along the mid-ocean ridge axes in the eastern Pacific. Altogether, our results provide insights into extrinsic and intrinsic factors affecting the dispersal and evolution of chemosynthetic symbiotic partners in the hydrothermal vents along the eastern Pacific Ocean. The online version of this article (doi:10.1186/s12862-017-0966-3) contains supplementary material, which is available to authorized users.