Figure 1.

Optimization of tetA for dual selection. (a) Workflow for tetA TIR randomization and screening of DNA sequence library variants. (b) Growth of the selected tetA^OPT TIR variant (red lines) in M9 medium supplemented with tetracycline and NiCl₂. The parental strain SIJ19 (E. coli K12 MG1655)⁴⁷ (-tetA, gray lines) was included as a control. Data represent the mean of biological triplicates or duplicates with standard deviations, for -tetA and tetA^OPT, respectively. See Figure S1 for growth analysis of the initial TIR library variants.