Big River Microbiology: Bacterioplankton Diversity and Community Dynamics of the Six Largest Rivers in the Arctic Ocean Watershed

分子微生物生态学领域正在进入第二个时代，超越了对多样性的简单调查，并揭示了与曾经被认为只适用于“宏观”生物的生态概念一致的有组织的多样性模式。最近发现的独立微生物群落之间的同步，类群-区域关系和细菌特有性要求在具有可比微生物群落的系统中进行有凝聚力的，大规模的微生物多样性研究。淡水浮游细菌对这一目的特别有用，因为它们的多样性相对有限，而且分布在全球。这些生物在生态上是重要的，催化关键的生物地球化学反应，并作为水生微生物食物网的核心成员。主要在湖泊中进行的多样性研究表明，浮游细菌群落是动态的，响应时空环境梯度，并随着优势种型的变化而变化。在河流中，由于停留时间短，这种变化可能迅速而极端。这种敏感性使河流浮游细菌成为确定微生物群落组成的环境控制的理想选择。不幸的是，人们对河流浮游细菌的多样性和动态知之甚少。这项工作将通过描述和比较北冰洋流域六条最大河流的浮游细菌多样性来测试细菌多样性的半球尺度模式，包括世界上最大的五条河流（Ob', Yenisey, Lena, Mackenzie，育空和Kolyma河），并通过将这些模式与广泛的物理，化学和生物测量的补充数据库联系起来来解释这些模式。在与PARTNERS小组（泛北极河流营养物质、有机物和悬浮沉积物运输）的合作下，在PI新任命的教员的“启动”基金的部分资助下，PI从2003年开始的4年时间里从这六条河流的河口收集了高质量的DNA样本。合作伙伴项目的总体目标是利用河水化学作为工具，研究流入北冰洋的大陆径流的起源和命运。淡水浮游细菌可能作为河流特定的遗传示踪剂有用，因为北冰洋的淡水很容易用分子技术将它们与海洋浮游细菌区分开来。首席研究员建议调查北极河流中丰富的、持久的、河流特异性的细菌种类，设计针对这些生物的PCR引物，并测试这些引物是否可以检测到北冰洋中高度稀释的淡水细菌。更广泛的影响。通过与合作伙伴的合作，该项目是一个多国努力（美国，加拿大和俄罗斯），将加强国际交流。它还将促进对全球微生物多样性的了解，为气候变化对北极的长期影响的研究做出贡献，并探索在海洋系统中使用遗传示踪剂。一名研究生将接受最先进的分子技术和生物信息学方面的培训。新的发现将被纳入研究生水平的课程“水生微生物生态学”。数据、发现和DNA序列将公布在“伙伴”项目网站上，供科学界下载。

The field of molecular microbial ecology is entering a second age, going beyond simple surveys of diversity and revealing organized patterns of diversity consistent with ecological concepts that were once thought only applicable to 'macroscopic' organisms. Recent discoveries of synchrony among independent microbial communities, taxa-area relationships, and bacterial endemism call for cohesive, large-scale studies of microbial diversity in systems hosting comparable microbial communities. Freshwater bacterioplankton are particularly useful for this purpose because of their relatively restricted diversity and their global distribution. These organisms are ecologically important, catalyzing critical biogeochemical reactions and serving as central members of aquatic microbial food webs. Diversity studies, conducted mainly in lakes, indicate bacterioplankton communities are dynamic, responding to spatial and temporal environmental gradients with shifts in dominant phylotypes. In rivers, such shifts can be rapid and extreme because of short water residence time. This sensitivity makes river bacterioplankton ideal for identifying environmental controls on the composition of microbial communities. Unfortunately, very little is known about the diversity and dynamics of river bacterioplankton. This work will test for hemisphere-scale patterns of bacterial diversity by characterizing and comparing the bacterioplankton diversity of the six largest rivers in the Arctic Ocean watershed, including five of the world's largest rivers (Ob', Yenisey, Lena, Mackenzie, Yukon, and Kolyma rivers), and interpreting these patterns by relating them to an extensive complementary database of physical, chemical and biological measurements. In collaboration with the PARTNERS group (Pan-Arctic River Transport of Nutrients, Organic Matter and Suspended Sediments), and partially funded with "start-up" funds associated with the PI's new faculty appointment, the PI has collected high quality DNA samples from the mouths of these six rivers over a 4 years period beginning in 2003. The overall goal of the PARTNERS project is to use river water chemistry as a tool to study the origins and fates of continental runoff to the Arctic Ocean. Freshwater bacterioplankton may be useful as river-specific genetic tracers freshwater in the Arctic Ocean as they are easily distinguishable from marine bacterioplankton using molecular techniques. The principal investigator proposes to survey Arctic Rivers for abundant, persistent, river-specific bacterial phylotypes, design PCR primers targeting these organisms, and test whether these primers can detect highly dilute freshwater bacteria in the Arctic Ocean. Broader Impacts. Through collaboration with PARTNERS, this project is a multi-national endeavor (USA, Canada, & Russia) that will strengthen international communication. It will also further the knowledge of global microbial diversity, contribute to research on the long-term impacts of climate change on the Arctic, and explore the use of genetic tracers in marine systems. One graduate student will be trained in state-of-the-art molecular techniques and bioinformatics. New discoveries will be incorporated into a graduate-level course entitled Aquatic Microbial Ecology. Data, discoveries and DNA sequences will be posted on the PARTNERS project website and made available for download by the scientific community.