TESTING POPULATION GENETIC STATISTIC FU’S FS AS AN APPROACH TO UNDERSTANDING CLONAL BACTERIAL POPULATION EXPANSIONS

Abstract

In this project, I identify genes under positive selection in Escherichia coli ST131, a rapidly expanding clone associated with antibiotic resistance. The population genetic statistic Fu's Fs was calculated for each gene in the study, as well as the position and identity of all mutations. Within the expanding C2 subclade of ST131, the TetR-family repressor acrR was identified by Fu’s Fs alongside other genes of interest.

E.coli ST131-C acrR is enriched for rare alleles, mostly attributed to frameshift and nonsense mutations. This phenomena is not clonal in nature, suggesting general selection for loss of function.

This project has verified that Fu’s Fs can identify genes that appear to be under selection, or evolving in a manner consistent with driving a population expansion. It may be useful as a complementary and easily generalizable method to prioritize specific genes, particularly in the case of emerging phenotypes like virulence, for further experimental validation.