Growth temperature associated protein expression and membrane fatty acid composition profiles of Salmonella enterica serovar Typhimurium

Abstract

Total cellular proteins and fatty acid composition profiles of mid-log phase cells of Salmonella enterica serovar Typhimurium grown at 8, 25, 37 or 42 °C were separated by 2D-PAGE and FAME analysis. Growth temperature associated protein expression can be grouped into 3 thermal classes which include proteins whose expression is: I) optimal at 37 °C, meaning their expression peaked at 37 °C; II) up-regulated with an increase in growth temperature; III) down-regulated with increase in growth temperature; meaning their expression peaked at 8 °C. At higher growth temperatures, proteins belonging to the functional groups of amino acid transport and metabolism, nucleotide metabolism, energy metabolism and post-translation modifications (chaperones) are present in substantially higher amounts. This increase in abundance is regulated in a temperature dependent manner. It is important to point out that proteins involved in energy metabolism observed in higher amounts at higher growth temperatures all belong to the glycolysis pathway, while at 8 °C they belonged to the TCA cycle. Increase in growth temperatures results in a decrease in membrane fatty acid unsaturation and an increase in saturated and cyclic fatty acids. These results provide an insight into the dynamic molecular and physiological responses of Salmonella Typhimurium during growth at different temperatures.