Untangling the complex geographic and evolutionary patterns of microbes

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The tiny size of microorganisms belies their extraordinary complexity. In spite of their size, most microbes have several thousand genes that encode a wide range of metabolic and cellular functions, some acquired from distant relatives through the process of lateral gene transfer (LGT). The spread of antibiotic resistance and adaptation to challenging environments such as polluted sites are particularly compelling examples of the impact of microbial LGT on society. One consequence of LGT is that building a Tree of Life to understand the evolution of microorganisms may be impossible or a meaningless exercise, since so much genetic information has been shared between distant lineages. The first part of my proposed research will address this question, by using new criteria to assemble trees that are more resistant to the effects of LGT, and by developing phylogenetic network approaches that can effectively show both vertical (parent-to-offspring) and lateral connections. A key objective of this work will be to replace the canonical Tree of Life with a network that is understandable in spite of its increased complexity.