The proteome of Salmonella Typhimurium grown under in vivo-mimicking conditions

To successfully infect a host, it is a prerequisite for enteric pathogens such as Salmonella enterica serovar Typhimurium to adapt to their environment, in casu the gastrointestinal tract. The adoption of an appropriate lifestyle is triggered by environmental signals such as the low oxygen availability and high osmolarity prevalent in the grit. In order to gain more insight in the changes that are induced when S. Typhimurium is adapting to these particular conditions, we used 2-D DICE technology to investigate the combined effect of low oxygen tension and high osmolarity on the proteome of S. Typhimurium SL1344 compared to standard laboratory conditions. As a validation of the 2-D DICE technique, preferential protein labeling by the Cy-dyes was assessed and proved to be negligible. The differentially expressed proteins identified reflect very well the applied culture conditions. Furthermore, reported transcriptional changes and observed changes at the translational level show overlap. Among the metabolic processes that are upregulated under in vivo-mimicking conditions are anaerobic fumarate respiration and the utilization of 1,2-propanediol. We also provide evidence that S. Typhimurium expresses an arginine deiminase pathway for the catabolism of L-arginine. The increased activity of this pathway was biochemically validated. Finally, also proteins involved in quorum sensing and virulence are differentially expressed under in vivo-mimicking conditions. These conditions offer possibilities as a simplified model system for the host environment given the high overlap of identifications in our study and reported genuine in vivo studies, respectively.