Project description:To characterize regulons of alternative sigma factor SigH, SigL, and SigC in Listeria monocytogenes, in-frame mutant strains were created in the 10403S background. Regulons controlled by these 3 alternative sigma factors were characterized by whole-genome microarrays. The L. monocytogenes 10403S wild type and sigma factor null mutation strains were grown at 37 °C to stationary phase (defined in this study as growth to OD600 = 1.0, followed by incubation for an additional 3 h) prior to RNA isolation. Transcriptional profiles of 10403S wild type were compared to those of null mutation strain. In addition to stationary phase condition, SigC regulon was further characterized using heat stress (cultures grown to log phase at OD600 = 0.4, 37 °C and then exposed to heat at 55 °C for 10 min) and a condition with IPTG-inducible expression of sigC (sigC gene is placed under Pspac promoter using pLIV2 vector in wild type 10403S background). Under these conditions, expression profiles were compared between (i) wild type and sigC null mutant for heat stress and (ii) IPTG-inducible sigC strain and sigC null mutant, respectively. Using adjusted P < 0.05 and ≥ 1.5 fold change as cutoff values, microarray analyses identified 169 SigH-dependent, 51 SigL-dependent, and 3 SigC-dependent genes. Keywords: Listeria monocytogenes, alternative sigma factor, SigH, SigL, SigC
Project description:Information regarding the Alkaline Tolerance Response (AlTR) in Listeria monocytogenes is very limited. In this study, L. monocytogenes was shown to exhibit a significant adaptive alkaline tolerance response (AlTR) following a 1-h exposure to mild alkaline (pH 9.5), which is capable of protecting cells from subsequent lethal alkali stress (pH 12.0). Treatment of adapted cells with protein synthesis inhibitor chloramphenicol has revealed that AlTR is at least partially protein-dependent. In order to gain a more comprehensive perspective on the physiology and regulation of AlTR, we compared differential gene expression and protein content at pH 9.5 using microarray and two-dimensional (2D) gel electrophoresis, (combined with mass spectrometry) respectively. By interfacing the results of both approaches this study showed strong evidence that alkali tolerance response in L. monocytogenes functions as to minimize excess alkalisation and energy expenditures while mobilizing available carbon sources. Adaptive intracellular gene expression involved genes that are associated with virulence, the general stress response, cell division, and changes in cell wall structure and included many genes with unknown functions. The variability observed between results of cDNA arrays and 2D may account for posttranslational modifications. Interestingly, several alkali induced genes/proteins can provide a cross protective overlap to other types of stresses. Alkaline pH provides therefore L. monocytogenes with nonspecific multiple-stress resistance that may be vital for survival in the human gastrointestinal tract as well as within food processing systems where similar alkaline conditions as the ones used in this study prevail. Keywords: Transcriptomic and Proteomic Comparison Study
Project description:Comparisons of gene expression profiles PMH infected or not by the bacterium Listeria monocytogenes (strain 10403S) for 72 hours and analysed by RNA-seq
Project description:These studies were designed to examine the transcription of Listeria monocytogenes strains 10403S and LO28 during intracellular replication in mammalian macrophages. Duplicate WT Listeria monocytogenes (strains 10403S and LO28) were used to infect mouse bone marrow-derived macrophages (BMMs). Bacterial RNA was harvested at 4 hours post-infection.
Project description:These studies were designed to examine the transcription of Listeria monocytogenes strains 10403S and LO28 during intracellular replication in mammalian macrophages.
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
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.