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GRK 1482 Jahrbuch 2011-2014

JUNIOR PRINCIPAL INVESTIGATORS GRK Annual Report 2011-2014 | Page 31 Education / Degrees 1999 - 2005 Biology, Julius-Maximilians-University, Würzburg, Germany 2005 Diploma in Biology 2005 - 2009 Ph.D. (Dr. rer. nat.) at the Chair of Microbiology, Julius-Maximilians-University, Würzburg, Germany Since 2009 Postdoctoral fellow and group leader at the Chair of Micro- bial Ecology and ZIEL, Department of Microbiology, Technische Universität München, Germany Research Interests and Achievements Food borne pathogens like the Gram positive bacterium Listeria monocy- togenes and the Gram negative bacterium Salmonella Typhimurium are encountered by various stresses, either in the environment, in food or in their host. We examine the adaptation of these pathogens to different envi- ronmental conditions. 1. L. monocytogenes is a facultative anaerobic bacterium. Although L. mo- nocytogenes encounters anaerobic niches both in the environment and during the colonization process in the intestine, the aerobic growth is still better described than the anaerobic growth [1]. We further characterized the adaptation of L. monocytogenes to anaero- bic conditions by investigating global transcriptional changes that de- pend on the oxygen availability. Furthermore we identified genes that are essential for anaerobic growth of L. monocytogenes. 2. Nitrite is used as food additive during raw sausage ripening. Besides contributing to color and flavor formation nitrite is also supposed to inhi- bit the proliferation of pathogenic bacteria. During the ripening process nitrite is chemically converted to reactive nitrogen species like nitric oxide (NO), which might be the antibacterial agent [2, 3]. We investigated the adaptive response of L. monocytogenes and S. Typhimurium to nitrite stress with DNA microarray analysis and next generation sequencing. Both organism show massive transcriptional changes during nitrite stress. In L. monocytogenes a broad general stress response can be ob- served, whereas in S. Typhimurium especially genes encoding for already well characterized NO detoxification systems [4] are amongst the stron- gest induced genes. The identification of new NO-detoxification systems is a major goal of this project as such a system could also contribute to survival of NO-stress during the colonization process. Dr. Stefanie Müller-Herbst Technische Universität München Microbial Ecology Weihenstephaner Berg 3, D-85350 Freising-Weihenstephan Selected Publications [1] Lungu B, Ricke SC, Johnson MG. Growth, sur- vival, proliferation and pathogenesis of Listeria monocytogenes under low oxygen or anaero bicconditions:areview.Anaerobe.2009,15(1-2): 7-17. [2] Cammack R, Joannou CL, Cui XY, Torres Martinez C, Maraj SR, Hughes MN. Nitrite and nitrosyl compounds in food preservation. Biochim. Biophys. Acta. 1999, 1411(2-3):475– 488. [3] Honikel KO. The use and control of nitrate and nitrite for the processing of meat products. Meat Sci. 2008, 78(1-2):68–76. [4] Prior K, Hautefort I, Hinton JC, Richardson DJ, Rowley G. All stressed out. Salmonella patho- genesis and reactive nitrogen species. Adv. Microb. Physiol. 2009, 56:1-28. Research Goals Characterize the adaptation of pathogens to different stresses relevant for survival of the pathogens in foods or during the coloni- zation process and understand the regu- latory mechanisms behind these adaptation processes Identify genes that are essential for the adaptation to the applied stress conditions in vitro Investigate the contribution of the respec- tive genes to the colonization process in vivo