Growth and virulence response of Salmonella typhimurium to soluble Maillard reaction products
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In order to determine the effects that Maillard Reaction Products (MRP) have on Salmonella Typhimurium, growth rates and virulence expression, in the presence of Maillard reaction products, were observed, using the β−galactosidase Miller Assay and Reverse Transcription Polymerase Chain Reaction (RT-PCR). The presence of MRP compounds in liquid media caused no negative effect on the growth rate of Salmonella cells. However, the addition of MRP compounds at a 1% level in the media caused a significant increase in hilA expression in Salmonella Typhimurium, and the highest induction levels were observed in media supplemented with arginine and histidine-MRP compounds. There was no effect on the induction of hilA with the 0.5% addition of the MRP compounds in the amended media as shown by the Miller Assay. However, there was an effect seen when using the Real Time RT-PCR assay that resulted in the same levels of significance seen at 1.0% additions of MRPs being seen at the 0.5% level as well. Since rsmC was shown to be a constitutive gene that had continuous levels of expression in Salmonella based on cell number, Real-Time PCR was then used to assess the hilA expression of Salmonella Typhimurium under different oxygen, pH levels, and osmolarity conditions. The results under low oxygen indicate that the combination of low osmolarity and high pH have the highest inducing effect on hilA expression. The hilA response under the same media conditions and a high oxygen environment showed the same pattern of expression as those bacteria grown under a non-aerobic environment. The media with a pH of 8 and low osmolarity conditions had the greatest effect on the induction of hilA with none of the other media showing any significant effect. The relative expression of hilA did decrease for those bacteria grown under aerobic conditions versus those grown under low oxygen conditions.
Kundinger, Megan Mary (2003). Growth and virulence response of Salmonella typhimurium to soluble Maillard reaction products. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from