Distinguishing the Evolutionary Mechanisms Shaping Endosymbiont Genomes

DEB-0089455J。马萨诸塞州伍兹霍尔海洋生物实验室的詹妮弗·沃纳格林博士获得了一笔赠款，用于研究永久生活在某些昆虫组织中的细菌基因组的独特特征。 细菌物种在其基因组中的DNA序列进化的速率和模式方面表现出很大的差异，但很少有比较研究探索产生这种差异的机制。不同的分子进化模式可能是由与栖息地、基因组中存在的基因和/或其他自然遗传过程的变化相关的机制引起的。 这个项目的目标是区分这些不同的机制如何有助于基因组如何以及为什么以它们的方式进化。该项目的重点是木蚁的细菌共生体，以及蚜虫的细菌共生体Buchnera，作为探索这种不寻常生活方式的分子进化后果的模型系统。 这些专性细菌共生体与自由生活的细菌物种如大肠杆菌密切相关。 Wernegreen的实验室小组将对来自多个不同谱系的Escheridatus，Buchnera和E.大肠杆菌中比较各组的分子进化模式。这将使他们能够测试不同的现象，这些现象可能是造成美洲龙和布赫内拉基因组进化变化的原因。 分析将包括对比共生体和E。大肠杆菌的蛋白质和DNA序列进化的速率和模式。 该项目的结果将提供一个框架，以了解细菌基因组进化速率，组成和结构的巨大多样性。

DEB-0089455J. Wernegreen Dr. Jennifer Wernegreen of the Marine Biological Laboratory at Woods Hole, MA, has been awarded a grant to study unique features of the genomes of bacteria that live permanently in the tissues of certain insects. Bacterial species show a wide variation in rates and patterns of DNA sequence evolution in their genomes, but few comparative studies have explored the mechanisms that produce this variation. Distinct patterns of molecular evolution may result from mechanisms related to changes in habitat, genes present in the genome, and/or other natural genetic processes. The objective of this project is to distinguish how these different mechanisms contribute to how and why genomes evolve in the ways that they do. This project focuses on Candidatus, a bacterial symbiont of carpenter ants, and Buchnera, a bacterial symbiont of aphids, as model systems to explore the molecular evolutionary consequences of this unusual lifestyle. These obligate bacterial symbionts are closely related to free-living bacterial species such as Escherichia coli. Wernegreen's lab group will sequence several protein coding genes from multiple, diverse lineages of Candidatus, Buchnera, and E. coli to compare patterns of molecular evolution in each group. This will permit them to test for different phenomena that might be responsible for evolutionary changes in the genomes of Candidatus and Buchnera. Analyses will include contrasting the symbionts and E. coli with regard to rates and patterns of protein and DNA sequence evolution. The results of this project will provide a framework to understand the vast diversity of evolutionary rates, compositions and architectures of bacterial genomes.