Mgso4

All chemicals used in the study were purchased from Sigma-Aldrich unless stated otherwise. LB medium: 10 g l⁻¹ tryptone, 5 g l⁻¹ yeast extract, and 10 g l⁻¹ NaCl. For agar plates, 15 g l⁻¹ agar was added. M9 medium: 6.8 g l⁻¹ Na₂HPO₄, 3 g l⁻¹ KH₂PO₄, 0.5 g l⁻¹ NaCl, 1 g l⁻¹ NH4Cl), 0.34 g l⁻¹ thiamine, 0.2% casamino acids (BD Biosciences), 0.4% glucose, 2 mM MgSO₄, and 100 μM CaCl₂. Antibiotic concentrations: where appropriate, the media contained ampicillin at a final concentration of 100 μg ml⁻¹ from a 100 mg ml⁻¹ aqueous stock solution and chloramphenicol at a final concentration of 25 μg ml⁻¹ from a 34 mg ml⁻¹ stock solution in absolute ethanol; for pOSIP-KO-mediated chromosomal integration, 50 μg mL⁻¹ kanamycin-sulfate was used. The indicated concentrations of antibiotics were used for both LB and M9 media. Inducer concentration: an isopropyl-d-1-thiogalactopyranoside gradient was prepared at 0, 1, 5, 10, 20, 30, 50, 70, 100, 200, and 500 μM final concentrations, diluted from a stock in DMSO. Phosphate-buffered saline (PBS): 8 g l⁻¹ NaCl, 0.2 g l⁻¹ KCl, 1.44 g l⁻¹ Na₂HPO₄, and 0.24 g l⁻¹ KH₂PO₄. Kanamycin (2 mg ml⁻¹) was added to the PBS before sampling in order to terminate protein expression.

Klebsiella strains were purchased from Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures and from Public Health England National Collection of Type Cultures (NCTC) and are described in Supplementary Information (Suppl. Table S4). Unless otherwise stated, Klebsiella strains were prepared by culturing in Lysogeny Broth (LB) medium (Roth) or Casamino Acids (CAA) (0.5% Bacto^TM Casamino acids, 5.2 mM K₂HPO₄, 1 mM MgSO₄) medium (BD Biosciences) at 28 °C, 30 °C or 37 °C (as indicated in Suppl. Table 1) with shaking (200 rpm); overnight cultures were prepared by inoculation from frozen stocks. Clinical Klebsiella strains used for agar overlay assay have been isolated in Lithuanian University of Health Sciences, Kaunas clinics, and are described in Suppl. Table S2.