Project description:Adaptation of Listeria weihenstephanensis to anaerobiosis. Trascriptional profiling at two different temperatures of L. weihenstephanensis
Project description:Investigation of whole genome gene expression level changes in Listeria monocytogenes EGD-e during incubation (0, 15 min, 30 min) in two types of soil extracts (TA, DA).
Project description:Listeria monocytogenes is an opportunistic food-borne bacterium that is capable of infecting humans with high rates of hospitalisation and mortality. Natural populations are genotypically and phenotypically variable, with some lineages being responsible for most human infections. The success of L. monocytogenes is linked to its capacity to persist on food and in the environment. Biofilms are an important feature that allow these bacteria to persist and infect humans, therefore, understanding the genetic basis of biofilm formation is key to understanding transmission. We sought to investigate the biofilm forming ability of L. monocytogenes by identifying genetic variation that underlies biofilm formation in natural populations using genome-wide association studies. Changes in gene expression of specific strains during biofilm formation were then investigated using RNAseq. Genetic variation associated with enhanced biofilm formation was identified in 273 genes by GWAS and differential expression in 220 genes by RNAseq. Statistical analyses show that number of overlapping genes flagged by either type of experiment is less than expected by random sampling. This is consistent with an evolutionary scenario where rapid adaptation is driven by variation in gene expression of pioneer genes, and this is followed by slower adaptation driven by nucleotide changes within the core genome.
Project description:Secreted antimicrobial peptides (AMPs) are an important part of the human innate immune system and prevent local and systemic infections by inhibiting bacterial growth in a concentration dependent manner. In the respiratory tract, the cationic peptide LL-37 is one of the most abundant AMPs and capable of building pore complexes in usually negatively charged bacterial membranes, leading to destruction of bacteria. However, adaptation mechanisms of several pathogens to LL-37 are already described and are known to weaken the antimicrobial effect of the AMP, for instance, by repulsion, export or degradation of the peptide. This study examines proteome wide changes in Streptococcus pneumoniae D39, the leading cause of bacterial pneumonia, in response to physiological concentrations of LL-37 by high resolution mass spectrometry. Our data indicate that pneumococci may use some of the known adaptation mechanisms to reduce the effect of LL-37 on their physiology, too. Additionally, several proteins seem to be involved in resistance to AMPs which have not been related to this process before, such as the teichoic acid flippase TacF (SPD_1128). Understanding colonization and infection relevant adaptations of the pneumococcus to AMPs, especially LL-37, could finally uncover new drug targets to weaken the burden of this widespread pathogen.
Project description:ISG15 is primarily documented as an interferon-stimulated, ubiquitin-like protein (ubl), which has anti-viral activity. Although ISG15 was the founding member of the ubl protein family, very little is known about its function. We have found that ISG15 expression in non-phagocytic cells is dramatically induced upon Listeria infection and that surprisingly this induction can be Type I Interferon independent. Listeria-mediated ISG15 induction depends on the cytosolic surveillance pathway, which senses bacterial DNA and signals through STING, TBK1, IRF3 and IRF7. Most importantly, we observed that ISG15 expression restricts Listeria infection both in vitro and in vivo. We then made use of Stable Isotope Labeling in tissue culture (SILAC) to identify the ISGylated proteins that could be responsible for the ISG15-mediated protective effect. Our SILAC analysis revealed that overexpression of ISG15 leads to a striking ISGylation of integral membrane proteins of the endoplasmic reticulum and Golgi apparatus, which correlates with increased canonical secretion of cytokines. Taken together, our data reveal a previously uncharacterized signaling pathway that restricts Listeria infection and acts via ISGylation, reinforcing the view that ISG15 is a key component of the innate immune arsenal of the mammalian host.
Project description:Listeria monocytogenes is a foodborne intracellular bacterial pathogen leading to human listeriosis. Despite a high mortality rate and increasing antibiotic resistance no clinically approved vaccine against Listeria is available. To identify antigens for this bacterial pathogen that can be encoded in mRNA vaccine formulations, we screened for Listeria epitopes presented on the surface of infected human cell lines by mass spectrometry-based immunopeptidomics. In between more than 15,000 human self-peptides, we detected 68 Listeria epitopes from 42 different bacterial proteins, including several known antigens. Peptide epitopes presented on different cell lines were often derived from the same bacterial surface proteins, classifying these antigens as potential vaccine candidates. Encoding these highly presented antigens in lipid nanoparticle mRNA vaccine formulations resulted in high levels of protection in vaccination challenge experiments in mice. Our results pave the way for the development of a clinical mRNA vaccine against Listeria and demonstrate the power of immunopeptidomics for next-generation bacterial vaccine development.
Project description:Alkali stress is an important means of inactivating undesirable pathogens in a wide range of situations, ranging from environmental cleaning of food processing environments, to the phagolysosomal killing of cells engulfed by mammalian phagocytes. Unfortunately, L. monocytogenes can launch an alkaline tolerance response (AlTR), significantly increasing persistence of the pathogen in such environments. This study compared the transcriptome patterns of alkali stressed and non alkali stressed L. monocytogenes 10403S cells, to elucidate the mechanisms by which this important pathogen adapts and/or grows during short or long-term alkali stress. Transcription profiles associated with alkali shock (AS) responses were obtained by DNA microarray analysis of mid-exponential cells suspended in pH 9 media for 15, 30 or 60 min. Transcription profiles associated with alkali adaptation (AA) were obtained by DNA microarray analysis of cells grown to mid-exponential phase in pH 9 media . Comparison of AS and AA transcription profiles with profiles from control (pH 7.0) cells identified over 2,000 genes that were differentially expressed under alkaline conditions. Rapid (15min) changes in expression included upregulation of genes encoding for multiple metabolic pathways, (including those associated with Na+/H+ antiporters), ABC transporters of functional compatible solutes such as carnitine, motility and virulence-associated genes as well as the σB controlled stress resistance network. Slower (30min and more) responses to AS and adaptation during growth in alkaline conditions (AA), included modest changes in mRNA concentrations, and genes involved in proton export. Keywords: Time course study of gene expression response to alkaline shock and adaptation