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GRK 1482 Jahrbuch 2011-2014

Abstract To investigate the contribution of the adaptation to hypoxia to survival of L. monocytogenes in the intestine, we compare the aerobic/anae- robic growth and the transcriptional adaptation in the non-pathogenic novel species L. weihenstephanensis and in different L. monocytoge- nes strains. In an upstream experiment we determine the genome se- quence of L. weihenstephanensis. First growth analysis revealed that fumarate supports anaerobic growth of some, but not all L. monocy- togenes strains, indicating indeed further strains specific differences in the adaptation to anaerobiosis. Introduction Listeria monocytogenes is a facultative anaerobic, osmotolerant and pathogenic Gram positive bacte- rium. It can be isolated from natural environments and its ability to grow at a broad temperature (0.4°C45°C) and pH- (5.29) range is a constant challenge for food preservation [1]. L. mo- nocytogenes is the causative agent of listeriosis. Listeria is taken up via contaminated food. During infection, the bacteria colonize different cell types, including epithelial cells, fibroblasts, hepatocytes and macrophages, which are readily infected. Once inside the host cell, L. monocytogenes rapidly lyses the phagosomal membrane in order to escape into the host cell cytoplasm, where intensive intracellu- lar multiplication and movement occur. Direct cell to cell spread allows the bacteria to enter neigh- bouring cells without an extracellular phase. This strategy enables the microorganism to cross three significant barriers in humans, namely the intestinal barrier, the blood–brain barrier and the fetoplacen- tal barrier [2]. The infection affects primarily preg- nant women, newborns and adults with weakened immune systems. Sepsis and meningitis are the two main clinical manifestations and the mortality rate is about 30%. L. monocytogenes strains display both genetic and serotypic diversity. Serotypic diversity results in thirteen recognized serotypes within the species, distributed between three different lineages. >90% of human listeriosis cases are attributed to an in- fection with serotypes 1/2a, 1/2b, and 4b. L. monocytogenes, in order to transiently colonize the host gastro intestinal (GI) tract, must survive acidic conditions within the stomach as well as elevated osmolarity and the presence of bile salts within the small intestine [3]. The capacity of L. mo- nocytogenes to adapt to different levels of oxygen is another key prerequisite for the successful infec- tion of its vertebrate host via the GI tract. Strain specific adaptations to anaerobiosis have been described previously [4]. In this study we want to identify additional, not yet characterized diffe- rences. Furthermore, we want to investigate if such specific adaptations can be linked to different sero- types and contribute to virulence. PhD FELLOWS Page 42 | GRK Progress Report 2011-2014 Elena Ferrari (M.Sc.) Microbial Ecology PhD 6/2 Impact of the adaptation of Listeria monocytogenes to anaerobic niches on the colonization of the intestine