P37: Experimental evolution of a thermophile from a mesophilic ancestor

The economic viability of many industrial processes is often limited by microbial thermal growth boundaries that are incompatible with process optimization. Consequently, there is significant interest in producing microbes whose thermal growth parameters match those needed for particular industrial applications. While various genetic engineering tricks can be employed for this purpose, these methods are limited by the fact that they cannot simultaneously select for a particular phenotype as well as optimize growth for that phenotype. Thus, engineered strains are often phenotypically competent but growth-attenuated and, therefore, less interesting from a practical perspective.  Here we demonstrate the production of a strain of Escherichia coli capable of robust growth at thermophilic temperatures obtained using experimental evolution via long-term culture. Simultaneous selection and optimization for such a complex phenotype was made possible through the use of a newly described long-term culture apparatus called the Evolugator™. Whole genome sequencing was then used to characterize the evolutionary history of the resultant genotype, identifying 31 genetic alterations that may contribute to thermotolerance. We have initiated studies to determine which of these mutations may contribute to the thermotolerant phenotype. This study demonstrates the power of experimental evolution for the alteration of complex phenotypes.