MIP: Symbiotic Niche Invasion by Beta-Rhizobia in North America

MIP：北美洲β-根瘤菌的共生生态位入侵

• 批准号: 0640246
• 负责人: Matthew Parker
• 金额: $ 21.11万
• 依托单位: SUNY at Binghamton
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0640246&HistoricalAwards=false
• 关键词: MIP; Symbiotic; Niche; Invasion; Beta

The symbiosis between legume plants and root-nodule bacteria is important to human welfare and to natural ecosystems, because it provides nitrogen compounds that are often a key limiting resource. Despite more than a century of intensive study of the phenomenon, biologists did not discover until recently that certain legume symbionts belong to a group known as the beta-Proteobacteria. Curiously, these symbionts are not related to any previously known nodule bacteria. At least two separate lineages in the beta-Proteobacteria have evolved to become legume symbionts (including strains of the genera Burkholderia and Cupriavidus). However, this trait is restricted to only a few of the species in these genera, and is highly atypical in the beta-Proteobacteria as a whole. Thus, the evolution of symbiotic ability is a recent innovation in this group, and was likely due to acquisition of symbiotic genes from distantly related bacteria. Such cases of naturally occurring lateral gene transfer between distantly related organisms have the potential to greatly affect the ecological relationships and evolution of bacteria in natural environments. However, biologists have only a limited understanding of these processes. The aim of this project is to analyze DNA sequence variation of both symbiotic beta-Proteobacteria and their legume hosts to reconstruct the biogeography and history of this relationship. The research will focus on symbiotic bacteria from all species of Mimosa plants native to the continental United States in order to determine whether beta-Proteobacterial symbionts have spread out of tropical biomes into temperate regions of North America, and whether the evolution of new legume species in this group has been associated with parallel evolution of new types of bacterial symbionts. Inoculation experiments will also be performed to test whether lateral transfer of symbiosis-related genes from older lineages of nodule bacteria has influenced the amount of specialization exhibited by beta-Proteobacteria toward various plant hosts. The scientific value of this research will be to provide a broader understanding of the evolutionary mechanisms, including lateral gene transfer, that contribute to diversification of microbial symbioses. In addition, species related to both Burkholderia and Cupriavidus nodule symbionts are important human or plant pathogens, and some of the legume species that host beta-Proteobacterial symbionts are invasive weeds of global concern. Therefore, this research will also help to provide a better understanding of the basic ecology of these bacteria and the frequency of major ecological transitions (e.g., from parasitism to mutualism), in order to better evaluate their impact on the environment and on human health. The project will also foster integration of research and science education by holding workshops for middle school and high school life science teachers to improve teaching practices concerning how scientists analyze organism relationships and phylogenetic history.

豆类植物与根结节细菌之间的共生对人类福利和自然生态系统很重要，因为它提供了通常是关键限制资源的氮化合物。 尽管对该现象进行了一个多世纪的深入研究，但直到最近，生物学家才发现某些豆类共生体属于一个被称为β-蛋白质的群体。 奇怪的是，这些共生体与任何先前已知的结节细菌无关。 在β-蛋白细菌中，至少有两个单独的谱系发展成为豆类共生体（包括Burkholderia属和Cupriavidus属的菌株）。 但是，这种特征仅限于这些属中的一些物种，并且在整个β-蛋白菌中是高度非典型的。 因此，共生能力的演变是该组的最新创新，并且很可能是由于从遥远相关的细菌中获取共生基因。 这种自然存在的横向基因转移的情况之间有可能极大地影响自然环境中细菌的生态关系和进化。 但是，生物学家对这些过程只有有限的理解。 该项目的目的是分析共生β-蛋白细菌及其豆科植物宿主的DNA序列变化，以重建这种关系的生物地理学和历史。 这项研究将重点关注来自美国大陆的所有含羞草植物的共生细菌，以确定是否从热带生物群体中扩散到北美温带地区的β-蛋白蛋白细菌共生体，以及该组中新豆类物种的进化是否与新型分类菌群的平行进化相关联。 还将进行接种实验，以测试来自结节细菌较旧谱系的共生基因的横向转移是否影响了β-蛋白杆菌对各种植物宿主的专业量。这项研究的科学价值将是对包括横向基因转移在内的进化机制有更广泛的了解，这有助于微生物共生的多样化。 此外，与Burkholderia和Cupriavidus Nodule Symbionts有关的物种是重要的人类或植物病原体，并且某些携带β-细菌菌群共生体的豆类物种是全球关注的侵入性杂草。 因此，这项研究还将有助于更好地理解这些细菌的基本生态以及主要生态转变的频率（例如，从寄生虫到互惠主义），以便更好地评估它们对环境和人类健康的影响。 该项目还将通过举办中学和高中生活科学教师的研讨会来促进研究和科学教育的整合，以改善有关科学家如何分析生物关系和系统发育史的教学实践。