Proteins derived from the insoluble fraction of a strain Sd1617 cell lysate separated in 2D gels in the pH range 4–7. Cells were isolated from the large bowel of infected piglet #1. The insoluble fraction was extracted with 2.5 M NaBr (hs-MBR fraction, left), followed by solubilization with 8 M urea, 2 M thiourea and 1% amidosulfobetaine-14 (usb-MBR fraction, right). Experimental conditions for 2D gel electrophoresis and staining are described in the Methods. Several proteins are listed in Table 1 with further descriptions. Integral OM proteins (e.g. OmpA and OmpX) were enriched in the usb-MBR fraction. Proteins responding to various stresses (e.g. AdiA, GadB, GroEL, DnaK, HtpG and ClpB) were relatively abundant in both fractions.