Microbiology Commons^™

An Investigation On The Impact Of Intestinal Oxygen Availability On Survival And Regulation Of Virulence In Listeria Monocytogenes, Damayanti Chakravarty

Dissertations

The deadly foodborne pathogen Listeria monocytogenes is a gram positive facultative anaerobic bacterium. It is the third leading cause of death from food-borne illnesses. Once ingested, it encounters various stressors in the gastrointestinal (GI) tract, including acidic pH, bile, and alterations in oxygen availability. Various studies have been done regarding the pathogen’s survival mechanism against acid and bile. Since the lower parts of the GI tract are anaerobic, it is imperative to investigate how physiologically relevant anaerobic conditions impact L. monocytogenes’s survival. Transcriptomic analysis of L. monocytogenes under conditions mimicking the GI tract was performed. A large number of genes …

The Role Of The Msaabcr Operon In Cell Wall Integrity And Programmed Cell Death During Biofilm Development, Bibek G C

Dissertations

Staphylococcus aureus is an important human pathogen in both community and health care settings. Biggest challenges with S. aureus as a pathogen is its ability to acquire antibiotic resistance and produce robust biofilms. In this work, we investigated the nature of the cell wall defect in the msaABCR operon mutant in the Mu50 (VISA) and USA300 LAC methicillin-resistant Staphylococcus aureus (MRSA) strains. Results showed that msaABCR-mutant cells had decreased cell wall thickness and cell wall crosslinking in both strains. These defects are most likely due to increased murein hydrolase activity and/or nonspecific processing of murein hydrolases mediated by increased …

Stress Response Mechanisms Of Listeria Monocytogenes, Oindrila Paul

Dissertations

Listeria monocytogenes is a Gram-positive, facultative intracellular food-borne pathogen that causes the disease listeriosis. In order to establish an infection, L. monocytogenes must survive multiple stressors encountered within the gastrointestinal tract, including alterations in pH, bile, salt, and oxygen availability. This dissertation focused on understanding the stress response of L. monocytogenes to bile. Bile acts as a bactericidal agent by disrupting the membrane integrity and causing instability to macromolecules like DNA. Thus, a bacterium must be able to maintain its membrane architecture, composition and integrity.

Often times, bacteria will modulate their fatty acid composition in the membrane to cope with …