Single Tf1 insertions were sufficient for resistance to CoCl₂ by regulating expression of adjacent genes. (A) The genomic context of enriched Tf1 integration tags reconstructed by homologous recombination. (B) Competition in 0.0 mM (left), 0.2 or 1.2 mM (right) CoCl₂ between cells lacking Tf1 and cells containing genomic integrations 5, 6, or 7. (C) Relative level of expression of genes adjacent to Tf1 integration sites. (ON) Overnight exposure to stress.