Fig. 7

Co²⁺, Zn²⁺, Cd²⁺, Ni²⁺ tolerance analysis of Xoo PXO99^A and the derivative strain in NB medium. ▲, wild-type strain Xoo PXO99^A; ∆, strain Xoo PXO99^A harboring pXOCgx01::Tn5. a CoCl₂ tolerance analysis; b ZnSO₄ tolerance analysis; c CdSO₄ tolerance analysis; d NiCl₂ tolerance analysis. Strains were inoculated into 10 mL NB medium with a final concentration of OD₆₀₀ = 0.01, and incubated at 28 °C with shaking at 200 rpm. Bacterial growth was determined by measuring OD₆₀₀ 22 h after inoculation. Relative cell density means the percentage of each strain’s cell density at different heavy metal concentrations versus the cell density when no heavy metal added. Data presented are from a representative experiment; similar results were obtained in other two independent experiments