Propagation of hypermutators in experimental evolution populations under different stress types

In this experiment, Escherichia coli populations, started with a hypermutator-prone genotype, were experimentally evolved in presence of three concentrations of NaCl (twelve populations for each concentration), three concentrations of gentamicin (twelve populations for each concentration) and in the absence of stress (24 control populations). These populations were passaged every day for 150 days with a 1/100 dilution, resulting in around 1000 generations. Evolved populations were sequenced at the population level. The goal was to identify the genetic basis for adaptation to both stress and to evaluate the potential impact of the size of the genetic basis on the selective advantage of hypermutators and on their propagation.