Experimental Evolutionary Studies of Temperate Adaptation: The Evolution of Bioenergetic and Growth Rate Responses of a Mesophilic Bacterium

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9507416 Changes in temperature have significant effects on the rates of biochemical reactions. We know how short term changes in temperature affect the growth rate, respiration and growth efficiency of microbes, but we know relatively little about how these factors change during evolutionary adaptation to change in temperature. This research will contrast the effects of temperature on energetics and growth of ancestral strains of the bacterium Escherichia coli with changes that occur during evolutionary adaptation of the bacteria. Multiple lines of bacteria derived from a common stock will be cultured in new thermal environments, including high, low, and variable temperature. For each line, growth rate, respiration rate, and the efficiency with which the bacteria convert food into new bacterial tissue will be determined. The research will determine how adaptation to a particular thermal regime alters the ability of the bacteria to grow and compete in other thermal environments. Replication of selection experiments with multiple lines of bacteria will reveal the range of variation in genetic responses to new thermal environments. This research will increase our ability to predict the long term response of bacteria to environmental variation, which is important because microbes are important energy consumers and nutrient recyclers in natural ecosystems. It will identify traits that confer adaptive advantages at different temperatures, and demonstrate the impact of those adaptations on bioenergetics. The identification of traits that increase growth efficiency at different temperatures will be of potential value in commercial culture operations.