Evolution of divergent life history strategies in marine alphaproteobacteria.
Evolution of divergent life history strategies in marine alphaproteobacteria.
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DOI：
10.1128/mbio.00373-13
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发表时间：
2013-07-09
期刊：
影响因子：
6.4
通讯作者：
Moran MA
中科院分区：
文献类型：
--
作者：
Luo H;Csuros M;Hughes AL;Moran MA
玫瑰杆菌和SAR11谱系的海洋细菌成功地利用了海洋栖息地，占地表水细菌的约40%，但它们的生活史不同，体现了斑块适应与自由生活的生态角色。在这里，我们使用一个系统发育的出生和死亡模型来理解支持不同生活史策略的基因组内容是如何在这些相关的α变形菌类群中进化的，结果表明，自由生活的SAR11的流线型基因组是从一个比现存成员略大的共同祖先基因组（约2000个基因）逐渐缩小的，而玫瑰杆菌的更大和可变大小的基因组是从一个相当大的共同祖先（约8000个基因）沿着动态途径进化的。SAR11谱系的基因组变化在大约8亿年的时间里逐渐发生，而玫瑰杆菌的基因组经历了更实质性的修改，包括2.6亿年的主要扩张时期。玫瑰杆菌第一次基因组扩增的时间与预测的现代海洋真核浮游植物的辐射一致，这些植物的大小足以产生营养丰富的微区，并且与这些微生物群之间的当今生态关联一致。我们认为，红系浮游植物的多样化是当今海洋中占主导地位的异养细菌浮游生物类群之间不同生活史策略的重要驱动因素。全球一半的初级生产发生在海洋，其中一半以上是由异养浮游细菌通过海洋微生物食物网加工的。由于细菌与海水有机物相互作用的位置和机制影响微生物的生长速率、代谢途径和生长效率，而这些反过来又影响碳矿化到大气和固存到深海的速率，因此，表征不同浮游细菌分类群的生活史策略的多样性是一个重要的课题。了解作为细菌与海洋系统生物化学相互作用基础的生态策略的进化起源，并扩大影响全球重要的生物地球化学过程，将提高对微生物多样性如何维持的理解，并使对未来海洋微生物反应的有用预测成为可能。
Marine bacteria in the Roseobacter and SAR11 lineages successfully exploit the ocean habitat, together accounting for ~40% of bacteria in surface waters, yet have divergent life histories that exemplify patch-adapted versus free-living ecological roles. Here, we use a phylogenetic birth-and-death model to understand how genome content supporting different life history strategies evolved in these related alphaproteobacterial taxa, showing that the streamlined genomes of free-living SAR11 were gradually downsized from a common ancestral genome only slightly larger than the extant members (~2,000 genes), while the larger and variably sized genomes of roseobacters evolved along dynamic pathways from a sizeable common ancestor (~8,000 genes). Genome changes in the SAR11 lineage occurred gradually over ~800 million years, whereas Roseobacter genomes underwent more substantial modifications, including major periods of expansion, over ~260 million years. The timing of the first Roseobacter genome expansion was coincident with the predicted radiation of modern marine eukaryotic phytoplankton of sufficient size to create nutrient-enriched microzones and is consistent with present-day ecological associations between these microbial groups. We suggest that diversification of red-lineage phytoplankton is an important driver of divergent life history strategies among the heterotrophic bacterioplankton taxa that dominate the present-day ocean. One-half of global primary production occurs in the oceans, and more than half of this is processed by heterotrophic bacterioplankton through the marine microbial food web. The diversity of life history strategies that characterize different bacterioplankton taxa is an important subject, since the locations and mechanisms whereby bacteria interact with seawater organic matter has effects on microbial growth rates, metabolic pathways, and growth efficiencies, and these in turn affect rates of carbon mineralization to the atmosphere and sequestration into the deep sea. Understanding the evolutionary origins of the ecological strategies that underlie biochemical interactions of bacteria with the ocean system, and which scale up to affect globally important biogeochemical processes, will improve understanding of how microbial diversity is maintained and enable useful predictions about microbial response in the future ocean.