The Effect of Oxygen on Bile Resistance in Listeria monocytogenes
Listeria monocytogenes is a Gram-positive facultative anaerobe that is the causative agent of the disease listeriosis. The infectious ability of this bacterium is dependent upon resistance to stressors encountered within the gastrointestinal tract, including bile. Previous studies have indicated bile salt hydrolase activity increases under anaerobic conditions, suggesting anaerobic conditions influence stress responses. Therefore, the goal of this study was to determine if reduced oxygen availability increased bile resistance of L. monocytogenes. Four strains representing three serovars were evaluated for changes in viability and proteome expression following exposure to bile in aerobic or anaerobic conditions. Viability for F2365 (serovar 4b), EGD-e (serovar 1/2a), and 10403S (serovar 1/2a) increased following exposure to 10% porcine bile under anaerobic conditions (P < 0.05). However, HCC23 (serovar 4a) exhibited no difference (P > 0.05) in bile resistance between aerobic and anaerobic conditions, indicating that oxygen availability does not influence resistance in this strain. The proteomic analysis indicated F2365 and EGD-e had an increased expression of proteins associated with cell envelope and membrane bioenergetics under anaerobic conditions, including thioredoxin-disulfide reductase and cell division proteins. Interestingly, HCC23 had an increase in several dehydrogenases following exposure to bile under aerobic conditions, suggesting that the NADH:NAD+ is altered and may impact bile resistance. Variations were observed in the expression of the cell shape proteins between strains, which corresponded to morphological differences observed by scanning electron microscopy. These data indicate that oxygen availability influences bile resistance. Further research is needed to decipher how these changes in metabolism impact pathogenicity in vivo and also the impact that this has on susceptibility of a host to listeriosis.
Identifying active deubiquitinases and kinases in chicken
Our long-term goal is to provide tools and resources for the identification of regulatory networks in chicken relevant to growth or disease. The specific objective of this proposal is to annotate chicken deubiquitinating enzymes (DUBs) and kinases at a genome-scale by using chemical proteomics. Our overall hypothesis is that chicken genome encodes for multiple DUBs and kinases, which have unique distribution in tissues. The rationale for our study is that the chemical probes that react with catalytically active enzymes can be utilized to determine tissue-specific expression and activity of DUBs and kinases, improving the existing annotation of chicken genome for future research. Experimental annotation of DUBs and kinases, based on their activity will be complementary to the existing computational predictions, which are likely to be incomplete or incorrect.
Host-pathogen interactions in Salmonella andYersinia infection
There is a fundamental knowledge gap in understanding the essential protein-protein interactions in salmonellosis and yersiniosis – which are some of the leading bacterial foodborne diseases. While they can be treated with antibiotics, the high incidence of the multidrug-resistant strains means that development of new treatments is essential. Our long-term goal is to understand the relevance of ubiquitin proteasome system in Salmonella and Yersinia infections to identify novel targets for therapeutic interventions. The overall objective is to identify the protein substrates and elucidate mechanisms of bacterial and human deubiquiitnating enzymes (DUBs) in these infections. The central hypothesis is that human and bacterial DUBs determine the disease outcome via deubiquitination of proteins in specific signaling pathways, such as inflammation. The rationale for this research is that the identification of DUB functions in infection can provide a better understanding of mechanisms of these foodborne diseases.
Depending on interest, a student can do literature search, bioinformatics analysis or laboratory work (protein extraction, proteomics). A person who can design a website would also be beneficial.
Teaching responsibilities include:
MCB 4403 – Prokaryotic Cell Structure and Function