Phylogenetic niche conservatism as a driver of microbial diversification and biogeography

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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.