Project description:Full title: Probing the pan genome of a foodborne bacterial pathogen Listeria monocytogenes: Implications for its niche adaptation, pathogenesis, and evolution Listeria monocytogenes is a foodborne bacterial pathogen well known for adaptability to diverse environmental and host niches, and a high fatality rate among infected, immuno-compromised individuals. Three genetic lineages have been identified within this species. Strains of genetic lineages I and II account for more than ninety percent of foodborne disease outbreaks worldwide, whereas strains from genetic lineage III are rarely implicated in human infectious for unknown, yet intriguing, reasons. Here we have probed the genomic diversity of 26 L. monocytogenes strains using both whole-genome sequences and a novel 385,000 probe pan-genome microarray, fully tiling the genomes of 20 representative strains. Using these methods to identify genes highly conserved in lineages I and II but rare in lineage III, we have identified 86 genes and 8 small RNAs that play roles in bacterial stress resistance, pathogenicity, and niche, potentially explaining the predominance of L. monocytogenes lineages I and II in foodborne disease outbreaks. Extending gene content analysis to all lineages revealed a L. monocytogenes core genome of approximately 2,350 genes (80% of each individual genome) and a pan-genomic reservoir of >4,000 unique genes. Combined gene content data from both sequences and arrays was used to reconstruct an informative phylogeny for the L. monocytogenes species that confirms three distinct lineages and describes the relationship of 9 new lineage III genomes. Comparative analysis of 18 fully sequenced L. monocytogenes lineage I and II genomes shows a high level of genomic conservation and synteny, indicative of a closed pan-genome, with moderate domain shuffling and sequence drift associated with bacteriophages is present in all lineages. In contrast with lineages I and II, notable genomic diversity and characteristics of an open pan-genome were observed in the lineage III genomes, including many strain-specific genes and a more complex conservation pattern. This indicates that the L. monocytogenes pan-genome has not yet been fully sampled by genome sequencing, and additional sequencing of lineage III genomes is necessary to survey the full diversity of this intriguing species and reveal its mechanisms for adaptability and virulence. This is a Listeria monocytogenes pan-genome tilling array designed using PanArray algorithm. 9 experimental strains (F2-569, M1-002, F2-208, J2-071, J1-208, W1-111, W1-110, F2-524, F2-501) vs reference (EGD-e) strain.
Project description:The foodborne pathogen Listeria monocytogenes uses a number of transcriptional regulators, including the negative regulator CtsR, to control gene expression under different environmental conditions and in response to stress. Gene expression patterns of DctsR log phase cells were compared to both wt and ictsR-mcsA log phase cells grown with 0.5mM IPTG to identify CtsR-dependent genes.We identified 62 CtsR-dependent genes that showed significant expression ratios (adj. P < 0.05), with ≥ 1.5-fold differential expression either between ΔctsR and wt or between ΔctsR and ictsR-mcsA. Keywords: Listeria monocytogenes, CtsR regulon, log phase
Project description:The foodborne pathogen Listeria monocytogenes uses a number of transcriptional regulators, including the negative regulator HrcA, to control gene expression under different environmental conditions and in response to stress. Gene expression patterns of DhrcA stationary phase cells were compared to wt to identify hrcA-dependent genes. We identified 61 HrcA-dependent genes that showed significant expression ratios (adj. P < 0.05), with ≥ 1.5-fold differential expression between ΔhrcA and wt. Combined with microarray analysis, Hidden Markov Model searches show HrcA directly repress at least 8 genes. Keywords: Listeria monocytogenes, HrcA regulon, stationary phase
Project description:Listeria monocytogenes strain 10403S has been studied extensively for stress response activity toward multiple stressors (acid, osmotic, cold, high temperature, etc.) as well as multiple stress regulons (SigB, CtsR, HrcA, etc.). Here we aimed to determine the transcriptional response of Listeria monocytogenes in early log phase towards the strong oxidative stress imposed by ClO2. The elucidation of such a response allows for further a more completel understanding of the mechanism of inactivation by sanitizers, specifically ClO2.
Project description:Several Toll-like receptors are activated by Listeria monocytogenes infection, resulting in the activation of MyD88 dependent signaling pathway. However, the negative role of MyD88 in gene expresson is unclear. To address this, we performed microarray analysis of mRNAs from WT or MyD88-/- peritoneal macrophages infected with Listeria monocytogenes.
Project description:Listeria monocytogenes cells (strain LI0521) were digested with trypsin for the identification of surface proteins. The supernatant was filter-sterilized and subjected to identification by LC-MS/MS. Concurrently secreted or shed proteins were identified by isolating filter-sterilized supernatants following incubation of L. monocytogenes cells in buffer without trypsin. This was followed by trypsin digest of the sterilized supernatant and identification by LC-MS/MS.
Project description:These studies were designed to examine the transcription of Listeria monocytogenes strains 10403S and LO28 during intracellular replication in mammalian macrophages.