Sodium tetrathionate

Bis-1-anilino-8-naphthalene sulfonate (bis-ANS), thioflavin T (ThT), sodium tetrathionate, sodium sulfide, cyanogen bromide, and other chemicals were purchased from Sigma. Standard insulin and goat anti-rabbit IgG peroxidase were purchased from Sigma-Aldrich Company. The dialysis tube (2 kDa cut-off) was purchased from Spectrum Scientific Company. Anti αB-Cry antibody was a generous gift of Professor Samuel Zigler (Johns Hopkins School of Medicine). Gel filtration media and Ni-NTA matrix were from GE Healthcare and Qiagen, respectively.

Growth assays were performed in No-carbon-E (NCE) medium [19 (link)] supplemented with trace metals (0.3 μM CaCl₂, 0.1 μM ZnSO₄, 0.045 μM FeSO₄, 0.2 μM Na₂Se₂O₃, 0.2 μM Na₂MoO₄, 2 μM MnSO₄, 0.1 μM CuSO₄, 3 μM CoCl₂, 0.1 μM NiSO₄) and 5 mM 1,2-propanediol (Sigma-Aldrich) as the sole carbon source. For anaerobic growth, cultures were incubated inside an anaerobe chamber with one of the following electron acceptors added to the medium: 40 mM sodium tetrathionate, 40 mM sodium nitrate, 40 mM dimethyl sulfoxide (DMSO) or 40 mM trimethylamine N-oxide (TMAO) (all purchased from Sigma-Aldrich). For microaerobic growth cultures were incubated inside a hypoxia chamber set at 0.8% oxygen. To enhance initial growth, media were inoculated with a single strain or with an equal mixture of indicated S. Typhimurium strains resuspended in LB and incubated at 37°C for 24 hours, which was based on a similar protocol [38 (link)]. Bacterial numbers were determined by plating serial ten-fold dilutions onto LB agar containing the appropriate antibiotics. The ratios of recovered wild-type and mutant bacteria after 24 hours were normalized to the ratio at 0 hours to calculate the competitive index.