Sequencing of E. coli barcodes in laboratory evolution experiment under increasing antibiotic concentrations

We have a library of E. coli where each cell is labeled with a 15 bp random barcode in a specific location on its chromosome. There are approximately 450,000 unique barcodes in the library. We evolved three replicates of this library in each of five environmental conditions: "low" chloramphenicol (1 ug/mL), "ultra-low" chloramphenicol (0.1 ug/mL), "low" trimethoprim (0.1 ug/mL), "ultra-low" trimethoprim (0.01 ug/mL), and no drug. These concentrations gradually increase to maintain approximately constant selection pressures. We sequenced the barcoded locus at 16 time points for each of these 15 populations.