FIG. 3.

Growth (expressed as the optical density at 600 nm [OD₆₀₀]) of wild-type (WT) strains LMD-9 and LMG18311 and their respective His⁻ and His⁺ derivatives. (A and B) Growth in CDM (A) and CDM lacking histidine (B) of the LMD-9 WT, LMD-9 His⁻ (ster_1198-ster_1207::lox72) (3 clones), the LMG18311 WT, and LMG18311 His⁺ PCR (3 clones). (C and D) Growth in CDM (C) and CDM lacking histidine (D) of the LMD-9 WT, the LMG18311 WT, and LMG18311 His⁺ Ch (3 clones). Growth was monitored at 10-min intervals with the Varioskan Flash multimode reader (Thermo Fisher Scientific, Zellic, Belgium) as described previously (8). Mean values calculated from triplicates are presented for WT strains.