Salmonella is a growi ng concern in low-moisture foods. The objective of this project is to further unlock the mechanism for Salmonella... Show moreSalmonella is a growi ng concern in low-moisture foods. The objective of this project is to further unlock the mechanism for Salmonella desiccation survival. Salmonella Tennessee and Typhimurium LT2 were used in this study, each demonstrating a strong and weak resistance to desiccation , respectively. Exponential phase cells were desiccated (RH= II %) for 5 days on steri le paper discs and were reduce d by 4 and 7-logs CFU/mL, respectively. This study examined the role of rod/cocci conversion in Salmonella stress res istance using an SEM. The typical rod-shape of Salmonella was altered upon a 5-day desiccation treatment (aw=O. l l), produ cing a cocci shape and significantly more so in the case of S. Tennessee. S. Tennessee fresh and desiccated cell lengths were 1.32 ± 0.12 and 1.14 ± 0.07 urn, respectively, compared to S. LT2 fresh and desiccated that were 1.55 ± 0. 19 and 1.42 ± 0.14 urn, respectively. Scatter plot analysis showed that the convers ion from rod shape to cocci occurred at greate r extent in S. Tennessee than S. Typhimurium LT2 responding to the 5-day desiccation treatment Cytoskeletal genes involved in cell elongation (rodA, rodZ, mrdB, mreB, mrdA, mrcA, and mrcB) were anal yzed for expression using qRT-PCR. The gene expression profile for the two strain s significantly differed with S. Tennessee virtually having no change in expression after 24-hour desiccation while S. LT2 exp ression ranged from 38 to 91-fold up-regulated . This thesis provided additiona l understanding of Salmonella desiccation resistant strategy; however, to fully understand the expression change of those genes, study of gene expression at different time point is needed in future. M.S. in Food Safety and Technology, July 2013 Show less
Enabled Filters
(-) = NCFST / National Center for Food Safety and Technology