Theses and Dissertations at Montana State University (MSU)
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Item Validating Salmonella typhimurium virulence modulation by ecto-5'-nucleotidase (CD73) in intestinal epithelial cells(Montana State University - Bozeman, College of Letters & Science, 2017) Schneider, Stephanie Lorain; Chairperson, Graduate Committee: Douglas KominskyExtracellular ATP is a pro-inflammatory molecule released during intestinal insult and must be converted to adenosine by ecto-5'-nucleotidase (CD73) for the resolution of intestinal inflammation [1]. Along with its anti-inflammatory role in the intestinal mucosa, CD73-generated adenosine contributes to host-microbe interactions at the mucosal surface by modulating pathogen replication and virulence, including that of Salmonella enterica serovar Typhimurium (S. Typhimurium) [2], [3]. It has been shown, in the absence of intestinal epithelial cell-specific CD73, S. Typhimurium virulence is attenuated in vivo and in vitro, implicating the intestinal epithelium as an underappreciated source for the development of novel antimicrobial therapies. Since direct modulation of extracellular adenosine leads to pleiotropic effects, the aim of this research was to determine the mechanism(s) of S. Typhimurium virulence modulation by CD73 in intestinal epithelial cells to identify specific molecular targets that modulate pathogenesis [4], [5]Item Secretory immunity in Balb/c mice against Salmonella typhimurium(Montana State University - Bozeman, College of Agriculture, 1990) Shope, Steven RichardItem The genetic basic of flagellar structure in Escherichia coli(Montana State University - Bozeman, College of Agriculture, 1960) Markusen, Aletha S.Item Characterization of aquatic injury in Escherichia coli and Salmonella typhimurium(Montana State University - Bozeman, College of Agriculture, 1978) Zaske, Susan KayItem Changes in the virulence of chlorine-injured Yersinia enterocolitica(Montana State University - Bozeman, College of Agriculture, 1985) LeChevallier, Mark WilliamItem Keys to unlocking the biofilm phenotype of virulent environmental isolate of Salmonella(Montana State University - Bozeman, College of Letters & Science, 2008) Clark, Stewart James; Chairperson, Graduate Committee: Anne CamperThe aim of this research was to elucidate the phenotypic adaptation of an environmental isolate of Salmonella enterica grown in a single species biofilm using transcriptomic analysis. This environmental isolate was obtained from an outbreak in Gideon, MO, and was classified as Salmonella enterica serotype Missouri. Gene expression profiles obtained from this environmental isolate were compared with profiles of the ATCC type strain Salmonella enterica serotype Typhimurium LT2 grown under the same conditions. It was shown that there were distinct transcriptional differences in both of the strains between the biofilm and planktonic phenotypes. Both strains exhibited the strong up-regulation of several gene pathways that were unique to the biofilm phenotype. These included genes responsible for the cobalamin-dependent anaerobic utilization of 1,2-propanediol (cob-cbi-pdu), type III secretion system apparatus and effector proteins located on Salmonella Pathogenicity Island 2 (SPI-2) and the well characterized csg operon largely responsible for biofilm formation in Salmonella. A significant proportion of the genes present on the virulence plasmid PSLT were shown to be exclusively up-regulated in the biofilm phenotype of Salmonella Typhimurium LT2, illustrating the tendency of this pathogen to exhibit a promiscuous lifestyle whilst in the non-host environment. It was further demonstrated that the environmental isolate exhibited a more tenacious biofilm-forming tendency and overall greater survivability than the type strain in a low nutrient, non-host environment. It appeared from the transcriptional profile of Salmonella Typhimurium LT2 during planktonic growth that the organism struggled to adapt and survive under low nutrient conditions as evidenced by the increased expression of ribosomal subunit operons rps and rpl and several stress-related genes including dnaK and htp. The conclusion may be drawn that Salmonella Missouri has developed several key systems differentiating the biofilm and planktonic phenotypes and affording it a competitive advantage. While some of these traits have previously been studied exclusively in the context of host pathogenicity, this research indicates that perhaps these so-called virulence strategies may afford the pathogen enhanced survival in non-host environments as well. Therefore, these findings suggest that the use of excessively sub-cultured laboratory strains may be inappropriate surrogates for studying the behavior of real-world pathogens.