Testing Membrane Adaptation Models in Laboratory-selected E. coli

University Of Arizona, Tucson AZ

Investigators

Abstract

Cell membranes serve as barriers between cells and their environments, and between compartments within cells. Maintenance of membrane function is essential for life, but many environmental variables significantly perturb membrane properties. Physiologists and biophysicists interested in membranes have proposed several competing hypotheses regarding which aspects of membrane structure must be conserved for proper membrane function, but comparative and biophysical experiments have not been able to distinguish between competing models in a consistent manner. This study will use FTIR and fluorescence spectroscopy to investigate which properties of membranes are functionally important in the bacterium, Escherichia coli. Lines that have been subjected to laboratory evolution at different temperatures for ~2000 generations will be compared with respect to membrane properties and composition, and new selection lines will be initiated to test specific membrane hypotheses. The predicted responses of E. coli membranes to selection differ among models, so these studies will provide a strong test of competing hypotheses for membrane adaptation. In addition to testing membrane models, this research will provide testable hypotheses for membrane adaptation in natural environments. If temperature has been as important a factor in membrane function and evolution as is believed, the membrane changes observed in E. coli may also be found in other organisms adapted to different thermal environments. This work will also have implications for understanding how rapidly organisms can adapt to environmental changes. Many models for climate change predict both higher average global temperatures and increased variability. If 2000 generations is not long enough for membranes to adapt to a constant, well-defined habitat, then many species will not be able to keep pace with the rate of climate change. Alternatively, these studies may reveal that organisms can rapidly evolve improved acclimatory ability, which would allow them to better survive variable conditions.