Comprehensive analysis of evolutionary mutations in a highly social bacterium

项目描述（由申请人提供）：本项目主要的长期目标是全面识别和分析5种模式社会细菌黏液球菌（Myxococcus xanthus）实验进化菌株中积累的所有进化突变。每个菌株都进化出了一种新的社会行为形式，这将是研究的重点，即强制性欺骗，重新进化的多细胞子实体发育，重新进化的社会群体，适应性欺骗抑制和十倍增强的掠夺性搜索。在对这些菌株的基因组测序达到高覆盖水平后，所有积累的突变将通过基因组序列、PCR和插入元件分析进行鉴定。突变出现的历史和随后的频率将定义来自进化中间冷冻种群的克隆的每个谱系（特定目标1）。将确定导致主要感兴趣表型的突变，并分析每个突变对进化适应性和社会表型的影响。序列突变之间的上位相互作用程度也将被量化。这些目标将通过跨基因组背景的突变转移和相应的种群水平表现分析来实现（具体目标2）。这些社会适应的分子途径和机制将通过结合全球方法（例如转录组和蛋白质组分析）和基于黄顶草社会遗传学现有知识的重点机制假设的测试来表征（具体目标3）。这个项目是非常重要的，因为它代表了一个突破性的，基于DNA序列的方法来理解细菌的社会进化在多个层次的生物组织。本研究探讨了进化生物学中的几个重要主题，这些主题也与人类病原体的进化有关，这些病原体依赖于类似于黄原分枝杆菌的社会特征来获得进化成功。

DESCRIPTION (provided by applicant): The major long-term goal of this project is to comprehensively identify and analyze all evolutionary mutations that accumulated in five experimentally-evolved strains of the model social bacterium Myxococcus xanthus. Each strain evolved a novel form of social behavior that will be the focus of study, namely obligate cheating, re-evolved multicellular fruiting body development, re-evolved social swarming, adaptive cheater suppression and ten-fold enhanced predatory searching. Having sequenced the genomes of these strains to a high coverage level, all accumulated mutations will be identified by genome sequence, PCR and insertion element analyses. The history of mutation appearances and subsequent frequencies will be defined for each lineage among clones from evolutionary intermediate frozen populations (Specific Aim 1). The mutations that cause the phenotypes of primary interest will be identified, and each mutation will be analyzed for its effects on evolutionary fitness and social phenotypes. The degree of epistatic interaction among sequentially incurred mutations will also be quantified. These goals will be accomplished by transfer of mutations across genomic backgrounds and corresponding population-level performance assays (Specific Aim 2). The molecular pathways and mechanisms that underlie these social adaptations will be characterized by a combination of global approaches (e.g. transcriptome and proteome analysis) and testing of focused mechanistic hypotheses based on existing knowledge of M. xanthus social genetics (Specific Aim 3). This project is highly significant because it represents a ground-breaking, DNA sequence based approach to understanding bacterial social evolution at multiple levels of biological organization. This research investigates several important themes in evolutionary biology that are also relevant to the evolution of human pathogens that rely on social traits analogous to those of M. xanthus for evolutionary success.