Phylogenetic niche conservatism as a driver of microbial diversification and biogeography

链霉菌属的细菌在土壤中广泛而常见。它们在碳循环中起着重要作用，是发现抗生素和其他天然产物的主要来源。超过一半的临床抗生素是在这个属中首次发现的，但这个属仍然缺乏一个健全的分类框架。更令人吃惊的是，关于链霉菌的生物多样性和生物地理学的信息几乎完全缺失。抗生素耐药性的演变是一个严重的问题，也是一个日益严重的危机。解决这一危机既需要努力确定新型抗生素，也需要努力遏制耐药菌株的演变。了解链霉菌的进化历史将最终为抗生素生产和耐药性的进化动力学提供见解。虽然具有重要的社会价值，但对链霉菌等非致病性土壤生物的生物地理学和进化史的研究还不够充分。了解链霉菌的生物地理学和促进其进化多样化的机制，将有助于从自然种群中发现新的遗传多样性和新的生物活性化合物。该项目将研究链霉菌属土壤细菌的微生物生物地理模式的生态和进化力量。主要的假设是，链霉菌的多样性表现出纬度梯度，这是由于冰期后北纬地区的范围扩大和系统发育生态位保守性导致的扩散限制造成的。这一假设将通过(1)使用高通量测序方法和计算分析来表征北美链霉菌的生物地理特征，(2)对来自纬度定义的姐妹分类群的菌株进行基因组和生理分析来验证。这个项目具有变革性，因为它为理解生物地理学和陆地微生物的多样化提供了一个新的范例。此外，通过研究姐妹分类群及其最近共同祖先的微生物基因组动态，作为其进化史，地理和栖息地的功能，该项目将揭示选择和水平基因转移在基因和生物系统发育中的作用的基本原理。

Bacteria in the genus Streptomyces are widespread and common in soils. They have important roles in the carbon cycle, and they are a major source for the discovery of antibiotics and other natural products. More than half of clinical antibiotics were first discovered within this genus, yet the genus still lacks a robust taxonomic framework. Even more striking, there is nearly a complete absence of information about Streptomyces biodiversity and biogeography. The evolution of antibiotic resistance is a critical concern and a growing crisis. Addressing this crisis requires both efforts to identify novel antibiotics and efforts to combat the evolution of resistant strains. Understanding the evolutionary history of Streptomyces will ultimately provide insight on the evolutionary dynamics of antibiotic production and resistance. While of critical societal value, research on the biogeography and evolutionary history of non-pathogenic soil organisms such as Streptomyces is understudied. An understanding of the biogeography of Streptomyces and mechanisms that promote their evolutionary diversification should stimulate discovery of novel genetic diversity and new bioactive compounds from natural populations. This project will examine the ecological and evolutionary forces that underlie patterns of microbial biogeography for soil bacteria in the genus Streptomyces. The main hypothesis is that Streptomyces exhibit a latitudinal gradient of diversity caused by post-glacial range expansion in northern latitudes coupled with dispersal limitation due to phylogenetic niche conservatism. This hypothesis will be tested by (1) using a high-throughput sequencing approach and computational analyses to characterize Streptomyces biogeography in North America and (2) performing genomic and physiological analysis of strains from latitudinally defined sister-taxa. This project is transformational in that it examines a new paradigm for understanding the biogeography and diversification of terrestrial microorganisms. Furthermore, by examining microbial genome dynamics in stains of sister-taxa and their most recent common ancestors as a function of their evolutionary history, geography, and habitat, this project will reveal fundamental principles on the role of selection and horizontal gene transfer on gene and organismal phylogenies.