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살모넬라 타이피뮤리움에서 세포 외막 소포체와 YcfR에 의한 병원성 및 저항성 조절 기전 규명
- Author(s)
- 김슬이
- Advisor
- 윤현진
- Department
- 일반대학원 분자과학기술학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2020-02
- Language
- eng
- Alternative Abstract
- Salmonella enterica serovar Typhimurium is one of major foodborne pathogens worldwide. Pathogenesis of S. Typhimurium is accomplished by a complex regulatory hierarchy involving a myriad of virulence determinants such as Salmonella pathogenicity island 1 (SPI-1) and 2 (SPI-2) which encode a distinct type III secretion system (T3SS1 or T3SS2) and multiple effector proteins. In this study, it was found that T3SS1 virulence effectors could be secreted and translocated to host cells using outer membrane vesicles (OMVs). T3SS1 effectors translocated by OMVs triggered actin rearrangement in the host cell and facilitated bacterial invasion into host cells. Taken together, T3SS1 effectors delivered by OMVs could exert their intrinsic activities inside host cells. OMV-mediated secretion of T3SS1 effectors might shed light on a new virulence strategy in Salmonella infection. Although Salmonella virulence has been studied in animal hosts, Salmonella can cause food poisoning outbreak by contaminated fruit and vegetable. To understand the life style of Salmonella in contact with plant, RNA-Seq was performed in Salmonella exposed to plants. As a result of transcriptomic analysis, the expression of ycfR was increased upon contact with plants. The lack of YcfR significantly increased biofilm-like behavior on the surfaces of glass (abiotic) and plants (biotic) and stimulated the product of curli fimbriae and cellulose. Interestingly, despite biofilm-like formation in the ΔycfR mutant strain, the lack of YcfR impaired bacterial resistance against various antimicrobial stresses. Besides, the ΔycfR strain showed significant bacterial envelope alteration including the outer membrane protein and lipopolysaccharides LPS. Interestingly, despite biofilm-like formation in the ΔycfR mutant strain, the lack of YcfR impaired bacterial resistance against antimicrobial stress. Taken together, these results suggest that YcfR might be an important factor for maintaining the integrity of the outer membrane. Considering the multifaceted structural and physiological alterations by the lack of YcfR, the roles of YcfR in Salmonella virulence was further deciphered. Salmonella lacking YcfR not only was attenuated in survival inside macrophages but also SPI-2 genes were also down-regulated. RpoS as a global transcription regulator responding to envelop stressors was increased in the ΔycfR mutant strain. Deletion of ycfR caused decreases in ssrAB transcription, however, an additional deletion of rpoS abolished the down-regulation of ssrAB in the ΔycfR mutant strain. Again, overexpression of RpoS in trans in the ΔycfRΔrpoS strain repressed ssrAB transcription. Chromatin immunoprecipitation assay revealed the interaction between RpoS and DNA sequences of upstream of ssrA. Taken together, these findings provide insight into a new role of RpoS in virulence regulation of Salmonella. Finally, understanding the virulence regulation mechanisms of S. Typhimurium would be helpful for the development of a new strategy to control for preventing Salmonella-associated outbreak in future
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- Appears in Collections:
- Graduate School of Ajou University > Department of Molecular Science and Technology > 4. Theses(Ph.D)
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