2D PAGE of S. aureus RF122 and N305 protein extracts. Supernatants (A and B) and total proteomes (C and D) were harvested during the stationary phase. Supernatant proteins were precipitated with 10% trichlororacetic acid and washed with high-grade ethanol. Samples were purified using the 2D Clean Up kit (GE Healthcare) then separated by isoelectrofocalization on pH4-7 strips (total proteome) or pH3-11NL strips (supernatant) for the first dimension, and by 12% polyacrylamide gels for the second dimension. The gels were stained with Biosafe (Biorad) Coomassie blue, according to the manufacturer’s instructions. Arrows indicate spots that were over-expressed.