CAREER: Integrating microbiology and population genetics through experimentation with the origins of a microbial mutualism

University Of Washington, Seattle WA

Investigators

Abstract

This research will study the evolution of two mutually-beneficial microorganisms. Humankind has long been captivated by species that seem to help each other out, such as interactions between pollinators and flowering plants or our bodies and the microorganisms that inhabit them. Because such species affect each other's ability to flourish, we expect to see some coordination of evolution across species as each adapts to the changes imposed by the other. Some mutations should only be beneficial in the presence of the coevolving partner. However, we do not know how often these reciprocal changes occur because we often cannot observe them as they happen and in many species it is difficult to determine which changes were a response to a partner species and which were adaptations to other features of their environment. This research will answer these questions by observing these interactions evolve in a microbial system. The research will also result in the development of an active-learning module on microbial evolution to be used in general undergraduate microbiology courses and the development of two inquiry-based courses for undergraduates. In these courses undergraduates will test the effects of mutations that occurred during evolution on the ability of populations to flourish with or without mutualism, allowing them to learn fundamental concepts of evolution and microbial ecology and genetics in an integrated manner. The experiment will consist of a two-species community of the bacteria Desulfovibrio vulgaris Hildenborough and the archaeon Methanococcus maripaludis, along with single-species control populations. Replicate communities will evolve over 3000 generations. The population genetics of this coevoling mutualism will be determined by sequencing the genomes of each species at several time intervals. The level of adaptation of populations to the biotic environment will be determined by comparing the fitness of populations with past and future mutualists, by moving mutations of interest into ancestoral strains, and by reconstructing all intermediates along the main line of descent and testing their fitness with and without a mutualist partner.