Effects of high hydrostatic pressure on membrane proteins of Salmonella typhimurium

Salmonella typhimurium is a leading cause of foodborne diseases. Today high hydrostatic pressure treatments are considered as alternative methods of p reservation. To select optimal conditions of treatment, we have to characte rize the cell targets of pressure. In this study the action of pressure on the bacterial membrane proteins is analysed. The total membrane extract is obtained by lysis of cells separated by equilibrium density gradient centri fugation. Protein content is analysed by electrophoresis SDS-PAGE and visua lised by silver stain. Electrophoretic profiles reveal the presence of thre e major outer membrane proteins and 12 minor proteins in control bacteria o uter membranes. Outer membrane protein content is drastically modified afte r treatments. In some cases, except for the major proteins OmpA and LamB, o ther outer membrane proteins seem to totally disappear. LamB is more resist ant to hyperbaric exposure when the pH of the media is acidic. This behavio ur could be explained by a different conformation adopted by the LamB prote in depending on the extracellular pH. This work allows us to define membran e proteins as a target of high hydrostatic pressure treatments. Knowledge o f the behaviour of these bacterial membrane proteins subjected to pressure under different conditions (pH, temperature, a(w)...) could allow an increa se in the efficiency of treatments. (C) 2000 Elsevier Science B.V. All righ ts reserved.