Date

2020-9

Author

Eran, Zeynep

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In this study 14 different genes (fimA, fimD, fimF, fimH, stjB, stjC, csgA, csgD, ompC, sthB, sthE, rmbA, fliZ ve yaiC) thought to be related to marT gene at Salmonella enterica serotype Typhimurium 14028 and each involved in the biofilm formation and besides this, MZ1627, a derivative of the same strain that is disrupted in terms of marT gene was examined according to its regulation characteristics with marT. For the comparative analysis of the target genes, each of the gene was mutated through antibiotic gene cassette insertion separately, as repeating the same process to test the autoregulation function of marT gene, 15 different mutant genes in total were obtained. Then, each of these strain's expression level was determined in the presence and absence of the marT induction by transforming recombinant plasmid (pBAD24+marT) into these strains where marT gene's expression is controlled by cloning it into the arabinose-induced BAD promoter. According to QRT-PCR results, marT gene has an important role in terms of regulation of the examined 14 genes. Again these results indicated that, the protein encoded by marT gene is at the same time an autoregulator which organize its own promoter positively, also in general, it suggested that, MarT protein not only regulates the expression of the misL gene encoding an autotransporter protein, but also acts as a global regulator in Salmonella. In this study, strains carrying mutant genes subjected to MarT regulation, compared to parental strain 14028, have also been investigated for their biofilm-forming capacity on polystyrene surfaces. As a result of 24 and 48 hours of incubation, it was observed that there was a statistically significant (p <0.05) decrease in the biofilm formation capacities of each mutant strain. It has been found that fliZ, ompC, rmbA, stjB and stjC genes are directly related to biofilm formation in Salmonella and that there is a serious decrease in biofilm formation in their absence. In the next step, the attachment properties of the mutant strains to the cell surface compared to the parental strain were examined and Caco-2 and HEp-2 cells were used for this. According to the results, single gene mutations are not sufficient for an effective attachment. One of the most important findings of this study is that the global regulator MarT also controls csgD expression, which is the main regulatory gene for biofilm formation. In our "post antibiotics" era caused by the increasing antibiotic resistance crisis, it is thought that the development of chemical inhibitors specific to MarT will play a pioneering role in finding new solutions targeting biofilm formation in Salmonella Typhimurium infections.

Subject Keywords

Adhesion, Biofilm Formation, Regulation, marT, Salmonella Typhimurium

URI

https://hdl.handle.net/11511/69052

Collections

Graduate School of Natural and Applied Sciences, Thesis