Protein display in 2D gels of Y. pestis KIM6+ cytoplasmic fractions in the pI range 4-7 (-Fe vs. +Fe conditions). Proteins were derived from cell growth in the presence of 10 μM FeCl3 at 26°C (top) or the absence of FeCl3 at 26°C (bottom). Gels (20 × 25 cm) were stained with CBB, with four gel replicates representing each group, and subjected to differential display analysis using the software Proteomweaver v.4.0. Protein assignment to a spot required validation by MS data from at least two representative gels. The denoted spot numbers are equivalent to those listed in Table 3 with their '-Fe vs. +Fe' protein abundance ratios and other data.