Branched Chain Amino Acids in the Regulation of Listeria monocytogenes Toxin Production
Listeria monocytogenes is a human pathogen with many virulence genes that contribute to infections. The expression of these genes is highly coordinated in response to different environmental signals. For example, the transcription factor CodY plays an important regulatory role in virulence gene expression in response to branched chain amino acids (BCAAs), including leucine, isoleucine, and valine. In addition to BCAAs, propionate is also a key environmental signal that can influence L. monocytogenes virulence gene expression. In fact, anaerobic exposure to propionate resulted in an increase in the production of the toxin listeriolysin O (LLO). We hypothesized that CodY was involved in mediating the upregulation of LLO production in response to anaerobic propionate exposure. To test this hypothesis, hemolytic assays were performed to measure and compare LLO activities in wildtype L. monocytogenes and a CodY-deficient mutant (ΔcodY) grown under various conditions. After testing different media types and using different data analysis methods, our results showed that CodY was not required for the upregulation of LLO production by anaerobic propionate exposure. However, CodY may be involved in the upregulation of LLO production by anaerobic exposure to propionate and isoleucine. In conclusion, the role of CodY in L. monocytogenes response to propionate might be more complicated than anticipated. There are likely other mechanisms that are involved in association with the CodY/BCAA regulatory pathway in mediating the regulation of virulence genes in L. monocytogenes.
Course Project 202310 BIO 421 P2
Primary Advisor's Department
Stander Symposium, College of Arts and Sciences
"Branched Chain Amino Acids in the Regulation of Listeria monocytogenes Toxin Production" (2023). Stander Symposium Projects. 2960.