Fernández Alarcón, Claudia Lissette2011-07-122011-07-122011-05https://hdl.handle.net/11299/109076University of Minnesota M.S. thesis. May 2011. Major: Comparative and molecular biosciences. Advisors: Dr. Timothy Johnson, Dr. Richard Isaacson. 1 computer file (PDF); x, 85 pages.Incompatibility group A/C (IncA/C) plasmids have received recent attention for their broad host range and ability to confer resistance to multiple antimicrobial agents.Due to the potential spread of multidrug resistance (MDR) phenotypes from foodborne pathogens to human pathogens, the dissemination of these plasmids represents a public health risk. In this study, four animal-source IncA/C plasmids isolated from Escherichia coli were sequenced and analyzed, including isolates from commercial dairy cows, pigs and turkeys in the U.S. and Chile. These plasmids were initially selected because they either contained the floR andtetA genes encoding for florfenicol and tetracycline resistance, respectively, and/or the blaCMY-2gene encoding for extended spectrum β-lactamase resistance. Overall, sequence analysis revealed that each of the four plasmids retained a remarkably stable and conserved backbone sequence, with differences observed primarily within their accessory regions, which presumably have evolved via horizontal gene transfer events. Comparison of these plasmids with other available IncA/C plasmid sequences shed further light on the core and accessory elements of these plasmids in bacteria originating from commercial animal production environments.Specifically, our results suggest that the blaCMY-2 plasmid lineage appears to have derived from an ancestral IncA/C plasmid type harboring floR-tetAR-strAB and Tn21-like accessory modules. Evidence is mounting that IncA/C plasmids are widespread among enteric bacteria of production animals and these emergent plasmids have flexibility in their acquisition of MDR-encoding modules, necessitating further study to understand the evolutionary mechanisms involved in their dissemination and stability in bacterial populations. 2)Incompatibility group A/C (IncA/C) plasmids have received recent attention for their broad host range and ability to confer resistance to multiple antimicrobial agents.Due to the potential spread of multidrug resistance phenotypes from foodborne pathogens to human pathogens, the dissemination of these plasmids represents a public health risk. In this study, transcriptome analysis of the Escherichia coli chromosome was performed in response to acquisition of the IncA/C plasmid pAR060302 using RNA-Seq. In total, 109 genes were identified as being differentially expressed at least 2-fold or greater; 65 of which were significantly up-regulated (p < 0.05) and 44 of which were significantly down-regulated. The marRAB genes of the multiple antimicrobial resistance (mar) locus were among the most strongly up-regulated genes together with genes such as garPLRK-rnpB. Further analysis of the expression of the mar genes in response to pAR060302 acquisition was performed in several wild type strains, confirming that pAR060302 up-regulates the mar genes in natural E. coli hosts. Overall, this work confirms that acquisition of the IncA/C plasmid by a plasmidless host modulates a number of E. coli chromosomal genes. The most over-represented biological process that were related to the differentially expressed genes are mainly involved in function related to carbohydrate catabolic process, cell wall and membrane, transporter activity, and structural constituent of ribosome and succinate dehydrogenase activity. The phenotypic extent of such modulations is yet to be determined, but these modulations may contribute to the overall success of this emergent plasmid type among enteric bacterial populations.en-USComparative and molecular biosciencesThesis or Dissertation