Sequencing of E. coli lab populations or isolates from lab populations evolved in sub-lethal concentrations of kanamycin. Escherichia coli str. K-12 substr. MG1655

We are looking at emergence of intrinsic/ de novo resistance upon exposure to sublethal concentration of kanamycin using E. coli MG1655 as a model. The trade-off between growth and tolerance of tolerant mutants at sublethal antibiotic concentrations is poorly understood. To understand this trade-off we performed in vitro evolution at sublethal concentrations of kanamycin over short time duration. We see that at a gross phenotypic level, earlier fixation of the fit kanamycin tolerant mutants was favoured in populations growing at lower rather than higher sublethal concentrations. Deep sequencing of these evolving populations or their isolates revealed the genetic composition of the two types of kanamycin tolerant mutations: the fit mutants comprised of point mutations in the gene encoding the translational elongation factor EF-G, while the costly mutants comprised of deletions in genes encoding subunits of the ATP synthase machinery.