Differential expression of proteins in listeria monocytogenes under thermotolerance-inducing, heat shock, and prolonged heat shock conditions

Listeria monocytogenes is a foodborne pathogen capable of employing stress adaptive responses to evade a variety of stressors including temperature stress. We employed two-dimensional gel electrophoresis coupled with matrix-assisted laser desorption/ionization-time of flight analysis to study the differential expression of L. monocytogenes (ATCC 43256) soluble proteins at heat shock (60°C) conditions, prolonged heat shock (60°C for 9 minutes) conditions, and thermotolerance-inducing (48°C for 30 minutes followed by 60°C for 9 minutes) conditions. We compared the proteome of L. monocytogenes under these conditions to the proteome at 37°C. Eighteen proteins were differentially expressed at 60°C (6 up-regulated and 12 down-regulated), 21 proteins were differentially expressed (12 up-regulated and 9 down-regulated) when the cells were exposed to 60°C for 9 minutes, and 20 proteins were differentially expressed (10 up-regulated and 10 down-regulated) when cells were initially exposed to 48°C for 30 minutes before 60°C for 9 minutes. There was one unidentifiable protein with observed molecular weight of 50?kDa which was differentially expressed across the three temperature treatments. Thermotolerance-inducing conditions caused the up-regulation of a protein by as much as 12-fold. DnaN, a previously identified stress protein, was up-regulated almost threefold at 60°C. TcsA, a lipoprotein (CD4 T cell-stimulating antigen), and Gap (glyceraldehyde-3-phosphate-dehydrogenase) were selectively expressed under prolonged heat shock conditions suggesting their potential as candidate marker proteins targets for identifying temperature-stressed L. monocytogenes cells.