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Jihoon Lim (Molecular and Cell Biology Major)
“Role of the dsb system in the antimicrobial resistance of Salmonella”
Sponsor: Professor Sangwei Lu, Public Health
Project Description
Salmonella typhimurium (S. typhimurium) is one of the leading causes of foodborne illnesses and mortalities. A major factor behind its virulence is its ability to survive well in the presence of hydrogen peroxide generated by macrophages through respiratory burst. Previous research has shown dsbD mutants of S. typhimurium to be more susceptible to hydrogen peroxide. DsbD works in conjunction with dsbA, B, and C in maintaining periplasmic disulfide bonds. More specifically, dsbD catalyzes the isomerase activity of dsbC by reducing it. DsbA and B help form disulfide bonds by oxidizing thiols. Jihoon will further investigate the role of dsbA, B, and C, and how it confers more resistance of S. typhimurium to hydrogen peroxide. From this research, he hopes to conduct quality senior honors research that will ultimately decrease the number of foodborne illnesses caused by S. typhimurium.
Scholar's Photo
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Jihoon working at the Lu Lab
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Scholar's Journal
I had a blast working in the lab over summer, although MCATs added some stress to my busy schedule. But given that I did not need to worry about classes, I was able to devote a lot more time to research. The retreat was the perfect way to start out my summer and really pumped me up to begin researching. I met a lot of cool people and got some great tips on how to become a better researcher. In the beginning of summer I truly felt that getting data was going to be a breeze.
But as is always is the case in research, a lot of unexpected obstacles visited me throughout summer. Most notably was the plasmid prep I did, that ended up taking most of the summer to complete. In the end, it turned out one of the buffers was of the wrong pH. Potassium acetate was supposed to have a pH of around 5, but mine was at 8. So no matter how many times and how carefully I followed the protocol, I was kind of doomed. Ouch!
Further to boot, my mutants have been acting real strangely as of late. The results I have gotten so far have been quite inconsistent with my hypothesis. The dsb system is supposed to help the bacteria survive when exposed to reactive oxygen species such as hydrogen peroxide. So if I knock one of the genes out via electroporation, I should make the bacteria more susceptible to hydrogen peroxide. But strangely, mutating some of the dsb genes have made the bacteria more resistant to hydrogen peroxide.
But through all these obstacles, I have gained skills and experiences in the lab that can only be gained through hard work and determination. I know a lot more methods that I can use in lab and my ability to think critically has improved as well. As of now, I am still working on the dsb system and will use immunoprecipitation to look for other genes that may be regulated by the dsbD gene. In addition I am reading a lot more research papers in order to have a better understanding of my research.
Overall, my research experience has been fun and exciting while challenging. Thanks to the Haas Scholars Program for funding my research and hopefully my plan B works out!
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