Comprehensive analysis of evolutionary mutations in a highly social bacterium

描述(申请人提供)：该项目的主要长期目标是全面识别和分析在五个实验进化的模式社会细菌黄色粘球菌菌株中积累的所有进化突变。每个品系进化出一种新的社会行为形式，这将是研究的重点，即专职作弊、重新进化的多细胞子实体发育、重新进化的社会群体、适应性的欺骗者抑制和十倍增强的捕食性搜索。在对这些菌株的基因组进行高覆盖水平测序后，所有累积的突变都将通过基因组序列、聚合酶链式反应和插入元件分析来鉴定。将为来自进化中间冷冻种群的克隆人中的每个谱系定义突变出现的历史和随后的频率(具体目标1)。将确定导致主要感兴趣的表型的突变，并分析每个突变对进化适应度和社会表型的影响。顺序产生的突变之间的上位性相互作用的程度也将被量化。这些目标将通过跨基因组背景的突变转移和相应的群体水平表现分析(具体目标2)来实现。构成这些社会适应的分子途径和机制的特征将是全球方法(例如转录组和蛋白质组分析)和基于现有的黄曲霉社会遗传学知识(具体目标3)的重点机械假说的测试相结合。这个项目具有非常重要的意义，因为它代表了一种开创性的、基于DNA序列的方法来理解细菌在生物组织的多个水平上的社会进化。这项研究调查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相关，这些病原体依赖与黄色微囊藻相似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.