Capillary Electrophoresis Separation of Protein Composition of γ-Irradiated Food Pathogens Listeria monocytogenes and Staphylococcus aureus

Background: A capillary electrophoresis method using UV detection was developed to analyse protein composition of the lysates of two foodborne pathogens, Listeria monocytogenes and Staphylococcus aureus which were previously treated at different irradiation doses. Methodology and Principal Findings: Bacterial samples were gamma-irradiated at different doses to produce damage cells, to kill cells and to provoke viable but non culturable cells (VBNC) in order to evaluate the respective expression of stress proteins. In Listeria monocytogenes, two proteins (MW of 70.2 and 85.4 kDa) were significantly changed (P <= 0.05) at different doses of irradiation. In Staphyloccocus aureus, one protein (50 S ribosomal protein) with the MW of 16.3 kDa was significantly decreased at a low dose of irradiation treatment and the other protein (transcriptional regulator CtsR) with the MW of 17.7 kDa was increased significantly (P <= 0.05) at all doses of irradiation treatment compared to control. Conclusion: Expression of two proteins from the acyltransferase family in Listeria monocytogenes was statistically changed during irradiation treatment (P <= 0.05). In Staphylococcus aureus, expression of the 50 S ribosomal protein decreased and the transcriptional regulator CtsR espression increased significantly (P <= 0.05) following irradiation treatment. These expressed proteins do not belong to the well-known heat shock proteins family of Listeria monocytogenes and Staphylococcus aureus. The research further confirmed that capillary electrophoresis is a useful method to separate and analyse proteins expression which may be related to the resistance or sensitivity of food pathogens to gamma-irradiation.