The Impact of Oxygen on the Intracellular Survival of \u3ci\u3eListeria monocytogenes\u3c/i\u3e

Listeria monocytogenes is an intracellular pathogen that is responsible for the foodborne disease listeriosis. In order to invade host cells and establish an infection, this pathogen must travel through the gastrointestinal tract where it is exposed to a variety of stressors, including low pH, bile, and variations in oxygen concentrations. These stressors necessitate this organism’s ability to sense and respond to its environment. Previous research has shown that bacteria use two-component systems to sense and regulate genes needed for improved survival in stressful environmental conditions. The goal of this study was to determine if the expression of the putative oxygen sensors, pdeD, resD, and fnr correlates with the invasion ability of Listeria. To do so, the expression of these genes was determined under microaerophilic and aerobic conditions using RT-qPCR for the strains 2011L-2626, F2365, 10403s, HCC23, 15313, and EGDe. The ability of these strains to invade and survive within intestinal epithelial cells was determined over a course of 5 hours. This study found that under low oxygen conditions, L. monocytogenes increased intracellular survival. This change in invasion and intracellular growth was in a strain dependent manner, however. The RT-qPCR indicated that the genes pdeD, fnr, and resD did not show a biologically significant expression change in response to lower oxygen concentrations. Further research is needed to determine which genes are involved in the regulation of invasion genes under microaerophilic conditions