Updated project metadata. We work with the bacterium Yersinia enterocolitica, a gastrointestinal pathogen. In this study we characterized a bacterial mutant strain called SOR17. We compared the protein extracts of SOR17 with that of the parental strain JB580v. Bacteria were grown in triplicate for 5 h at 37°C, and following bacterial disruption by French press, proteins were fractionated into soluble or membrane proteins. We also compared total protein extracts of bacteria grown for 16 h at 27°C. Two-dimensional electrophoresis were performed and proteins were stained with Coomassie brilliant blue. Spots whose abundance changed more than 2 fold were excised and sent to mass spectrometry for identification by either MALDI-TOF PMF or LC-MS/MS.