Figure 2. Differential expression of S. Typhimurium island-encoded sRNAs during growth under various stress conditions determined by northern blot analysis³² or RT-PCR.⁵⁷ Expression levels are shown as high, medium, low and no expression.³² Cultures of S. Typhimurium were grown under different conditions (described from left-hand side): Cells grown in LB to an OD₆₀₀ of 0.3, 1 and 4.5; Oxygen limitation overnight growth without agitation in 50 mL Falcon tubes to an OD₆₀₀ of 0.9; Osmotic stress—cells grown in LB containing elevated (0.5 M) NaCl levels for 30 min; Oxidative stress using 0.2 mM paraquat (PQ) and 1 mM hydrogen peroxide (H₂O₂); Iron limiting conditions—addition of 0.2 mM 2,2’ dipyridyl; pH stress – LB at pH 4.9 (adjusted with HCl) and LBK media at pH 8.4; N min low Mg and N min high Mg – N minimal media with 10 µM MgCl₂ (low magnesium) and 10 mM MgCl₂ (high magnesium); Cold shock at 15°C and heat shock at 42°C; Intra-macrophage 1h and 8h – within activated J774.A1 macrophage cells assayed using gentamycin protection assay;³² In vitro conditions resembling the gastrointestinal tract.⁵⁷