A reproducible set of Tf1 integration tags showed improved growth in CoCl₂. (A) Cells with Tf1 integration tags were passaged for 80 generations in CoCl₂. Changes in clonal populations were monitored by sequencing the tags at T = 0 and T = 80 generations. (B) Number of generations observed per 24-h passage. (C–E) Proportions of cells in the cultures containing a Tf1 integration tag at each of the insertion sites at the beginning (T = 0; x-axis) versus the end (T = 80; y-axis) of the passages without CoCl₂ (C) or in the presence of 0.2 mM (D) or 1.2 mM (E) CoCl₂. Insertion site tags that changed twofold or more in all three replicated experiments are considered to have expanded (red) or diminished (green).