Genes That are Affected in High Hydrostatic Pressure Treatments in a Listeria monocytogenes Scott A ctsR Deletion Mutant

Introduction: Listeria monocytogenes is a foodborne pathogen of significant threat to public health. High hydrostatic pressure (HHP) treatment can be used to control L. monocytogenes in food. The CtsR (class three stress gene repressor) protein negatively regulates the expression of class III heat shock genes. In a previous study, a spontaneous ctsR L. monocytogenes deletion mutant 2-1 that was able to survive under HHP treatment was identified; however, there is only limited information about the mechanisms of survival and adaptation of this mutant in response to high pressure.

Purpose: To investigate which genes are affected with high hydrostatic pressure treatment in the ctsR deletion mutant 2-1.

Methods: Microarray technology was used to monitor the gene expression profiles of the ctsR mutant 2-1 under pressure treatment (450 Mpa, 3min). Gene expression changes determined by microarray analyses were confirmed by real-time RT-PCR assays.

Results: Compared to the non-pressure-treated ctsR mutant 2-1, 14 genes were induced (> 2-fold increase) in the ctsR deletion mutant whereas 219 genes were inhibited (< -2-fold decrease) by pressure treatment. The induced genes included genes encoding proteins involved in synthesis of purines, pyrimidines, nucleosides, and nucleotides, transport and binding, transcription, cell membrane, DNA and energy metabolism, protein synthesis, and unknown functions. The inhibited genes included genes encoding proteins for transport and binding, cell envelope, transcription, amino acid biosynthesis, regulatory functions, cellular processes and central intermediary metabolism.

Significance: The information concerning L. monocytogenes survival under HHP at the molecular level may contribute to improved HHP treatments for food processing.