Bacterial Population Structure: Evaluating Gene Flow in the Symbionts of Deep-Sea Mussels \(Genus Bathymodiolus\)

细菌种群结构：评估深海贻贝（Bathymodiolus属）共生体中的基因流

• 批准号: 0453901
• 负责人: Colleen Cavanaugh
• 金额: --
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0453901&HistoricalAwards=false
• 关键词: Bacterial; Population; Structure; Evaluating; Gene

Recent evidence suggests that microbial populations in spatially and chemically fragmented habitats are not distributed ubiquitously, but rather exhibit geographic structure. Heterogeneous environments restrict gene flow among populations, which promotes genetic differentiation, local adaptation, and speciation. Hydrothermal vents are distributed in a patchy array due to topographic features, deep ocean currents, and variations in vent fluid chemistry. Though associations between chemosynthetic bacteria and their invertebrate hosts provide the basis for macrofaunal production at deep-sea hydrothermal vents, almost nothing is known about the distribution of genetic variation in the symbionts and how population structure of bacteria affects ecological interactions and the evolution of symbioses at vents. This research project will test models of gene flow for populations of thioautotrophic and methanotrophic endosymbionts of mussels inhabiting fast-, slow-, and discontinuous spreading centers by examining genetic structure along the East Pacific Rise (EPR), Mid-Atlantic Ridge (MAR) and within the Lau Back-arc Basin (Lau), respectively. Bathymodiolus mussels are found at nearly all hydrothermal vent sites and most likely acquire their symbionts from the environment in each generation, making them model systems for evaluating geographic structure of bacterial endosymbionts. Symbionts from 3 ridges, 5 vent fields per ridge, and mussels from 2-4 sites per vent field will be studied. For both types of symbiont, 4 DNA markers (16s rRNA, ITS, ftsZ, and either pmoA or soxY for the methanotroph and thioautotroph, respectively) will be sequenced from 20-30 mussel individuals per site. Population genetic, coalescent, and phylogeographic approaches will be employed in the data analyses. Mechanisms that affect the population structure of bacterial endosymbionts have important implications for microbial biogeography, diversity, and the origin, evolution, and ecology of life at deep-sea hydrothermal vents. This research will yield the first high-resolution examination of gene flow among environmentally transmitted endosymbiont populations. Comparisons between hydrothermal vent fields will provide valuable information on the historical biogeography and barriers to dispersal for bacterial species. These findings will allow broader inferences regarding how deep ocean currents influence dispersal and the evolution of chemoautotrophic communities. Further, because hydrothermal vents serve as analogs to early Earth as well as extraterrestrial environments, results from this research will have implications for the origin of eukaryotic cell organelles and the ecology and evolution of microbes in extreme biomes. Annotated gene sequences will be deposited in GenBank and made publicly accessible through a website (www.endosymbiont.org) that the investigators use to present information on endosymbiosis to the scientific and public community. The investigators also give seminars designed for the general public on scientific topics, including microbial symbiosis and diversity, chemosynthesis and life on this planet and others. Undergraduates, graduate students, and postdoctoral fellows will have ample opportunity to participate in analyses of these gene sequences, both through their research and through inclusion in university courses.

最近的证据表明，空间上和化学上分散的生境中的微生物种群并不是无处不在的，而是表现出地理结构。异质环境限制了种群间的基因流动，从而促进了遗传分化、局部适应和物种形成。由于地形地貌、深海洋流和喷口流体化学的变化，热液喷口呈斑块状分布。尽管化学合成细菌与其无脊椎动物宿主之间的联系为深海热液喷口的大型动物生产提供了基础，但对共生体中遗传变异的分布以及细菌的种群结构如何影响生态相互作用和喷口共生生物的进化几乎一无所知。本研究项目将通过分别研究东太平洋海隆(EPR)、中大西洋海脊(MAR)和刘弧后盆地(LAU)的遗传结构，测试居住在快速、缓慢和不连续扩散中心的贻贝硫代自养和甲烷营养内共生菌种群的基因流动模型。贝类在几乎所有的热液喷口都有发现，很可能每一代都从环境中获得共生体，这使它们成为评估细菌内共生体地理结构的模型系统。将对来自3个山脊、每个山脊5个喷口的共生体和每个喷口2-4个地点的贻贝进行研究。对于这两种共生体，4个DNA标记(16S rRNA、ITS、FtsZ，以及甲烷自养和硫代自养的pmoA或soxy)将从每个地点的20-30个贻贝个体中测序。在数据分析中将采用种群遗传学、聚集性和系统地理学方法。影响细菌内共生菌种群结构的机制对微生物地理学、多样性以及深海热液喷口生命的起源、进化和生态具有重要的意义。这项研究将首次对环境传播的内共生菌种群中的基因流动进行高分辨率检查。热液喷口区域的对比将提供有关细菌物种历史生物地理和扩散障碍的有价值的信息。这些发现将使人们能够更广泛地推断深海洋流如何影响化学自养群落的扩散和演化。此外，由于热液喷口类似于早期地球和地外环境，这项研究的结果将对真核细胞细胞器的起源以及极端生物群中微生物的生态和进化产生影响。注解的基因序列将保存在GenBank中，并通过一个网站(www.endosymbiont.org)向公众公布，研究人员利用该网站向科学界和公众展示有关内生共生的信息。研究人员还为公众设计了关于科学主题的研讨会，包括微生物共生和多样性、化学合成和地球上的生命等。本科生、研究生和博士后研究员将有充分的机会参与这些基因序列的分析，既通过他们的研究，也通过纳入大学课程。