L 1 tryptone

All experiments were performed with Salmonella enterica subsp. enterica serovar Typhimurium str. LT2 (designated S. enterica) and derivatives thereof. Mutations were transferred between strains through generalized transduction with phage P22 HT 105/1 int-201 (Schmieger, 1972 (link)). All growth was done in LB [5 g L^–1 yeast extract (Oxoid), 10 g L^–1 Tryptone (Oxoid), 10 g L^–1 NaCl, and 1 mM NaOH] or LA (LB solidified with 15 g L^–1 agar). To simplify preparation of competent cells for electroporation, NaCl was omitted from the LB medium. When needed, antibiotics were added to the following concentrations: chloramphenicol (cam); 12.5 mg L^–1, ampicillin (amp); 50 or 100 mg L^–1, kanamycin (kan); 50 mg L^–1, and tetracycline (tet); 7.5 mg L^–1. To select for loss of the cat-sacB cassette, we used sucrose selection plates (LA without NaCl, supplemented with 50 g L^–1 sucrose). When growing cells to exponential phase to prepare samples for LC-MS/MS, FACS analysis or mRNA extractions for RT-PCR, LB was supplemented with 2 g L^–1 glucose in order to allow for exponential growth at higher cell density. All growth (except during λ red recombineering) was at 37°C.

The batch reactors and agar plates contained Luria–Bertani (LB) broth consisting of 1 g L ${}^{-1}$ NaCl (Glassworld, South Africa), 20 g L ${}^{-1}$ tryptone (Oxoid, UK) and 10 g L ${}^{-1}$ yeast extract (Oxoid, UK), with 5 g L ${}^{-1}$ agar (Sigma Life Science, Spain) added to the agar plates solution only. The stock solution of 10,000 mg L ${}^{-1}$ Pb(NO ${}_3$ ) ${}_2$ consisted of 1.6 mg Pb(NO ${}_3$ ) ${}_2$ (Glassworld, South Africa) in 100 mL distilled water. Metabolic activity was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) (Sigma, Aldrich, MO, USA). The nitrate concentration was determined using a nitrate test (Supelco, Germany). Ethylenedinitrilotetraacetic acid disodium salt (EDTA) (Supelco, Germany) was used in the determination of the extracellular and intracellular Pb(II) concentration.