In the present study, the proteome of a strain of S. enterica serovar Enteritidis PT4, grown either as biofilm on stainless steel surface or as free-floating (planktonic) in Brain Heart (BH) broth, was investigated in order to detect the strong differences in whole-cell protein expression patterns between the two growth styles. The proteins extracted from both types of cells were subjected to 2-D PAGE, followed by in-gel tryptic digestion, extraction, subsequent MALDI-TOF mass spectrometry (MS) analysis and finally database searches for protein identification. Using this approach, 30 proteins were identified as differentially expressed between the two growth modes on an “on-off” basis, that is, proteins that were detected in one case but not in the other. In particular, 20 and 10 proteins were identified in biofilm and planktonic-grown cells, respectively. The group of proteins whose expression was visible only during biofilm growth included proteins involved in global regulation and stress response (ArcA, BtuE, Dps, OsmY, SspA, TrxA, YbbN and YhbO), nutrient transport (Crr, DppA, Fur and SufC), degradation and energy metabolism (GcvT, GpmA, RibB), detoxification (SseA and YibF), DNA metabolism (SSB), curli production (CsgF), and murein synthesis (MipA). To summarize, this study demonstrates that biofilm growth of S. Enteritidis causes distinct changes in protein expression and offers valuable new data regarding some of the proteins presumably involved in this process. The putative role of these proteins in the maintenance of a biofilm community in Salmonella and other bacteria is discussed.
