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. Independent RNA isolations were performed for strain 10403S with and without exposure to ClO2 from cells grown to early log phase. Four biological replicates were used in competitive whole-genome microarray experiments. For each set of hybridizations, RNA from a control sample of Listeria monocytogenes was hybridized with RNA from a culture of L. monocytogenes following exposure to ClO2. Dye swapping was performed for the four replicates to mitigate any concerns of dye bias.
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 fresh produce outbreaks have been associated with Listeria monocytogenes contamination during postharvest. Sanitation practices are among the most critical measures for controlling and minimizing bacterial growth. The aim of this research was to evaluate the transcriptomic response of a cocktail of four L. monocytogenes strains associated with the 2011 cantaloupe and 2014 caramel apple listeriosis outbreaks. Differentially expressed genes (DEGs) were evaluated after exposure to sublethal concentrations of four sanitizer treatments including chlorine (Cl) and peracetic acid (PAA) at 5 ppm, lactic acid 0.2% (LA), and 50% silver dihydrogen citrate (SDC) during 70 s exposure via RNA-sequencing (n=4). SDC exposure resulted in the greatest number of DEGs (total: 127; up: 57, down: 70), followed by LA (total: 32; up: 8, down: 24), Cl (total: 16; up: 8, down: 8), and PAA (total: 1; up: 1). Non-coding RNAs including small, long, transfer and Listeria-specific regulatory RNAs (Rli) ranked among the most significantly DEGs across treatments. From those, one unique gene lmos88, associated with S-Adenosyl Methionine (SAM) synthesis, was significantly upregulated across all sanitizers, suggesting a fundamental role on L. monocytogenes response. Among Rlis- rli30, rli47 and rli55 were upregulated in response to Cl and SDC treatments, respectively. Both SDC and LA had significant overlap in gene response. Only Cl treatment caused significant downregulated pathways including tRNA charging (Q=0.00263), aminoacyl-tRNA biosynthesis (Q=0.00328), and other related metabolic clusters (Q=0.00355). Upregulated gene ontology (GO) terms were observed only after SDC application and were related to membrane-associated functions (Q=0.00034). These findings underscore how commercially available sanitizers affect L. monocytogenes transcriptomic profile, and the key role non-coding RNA genes play on response to sanitizers.
Project description:The SOS response is a conserved pathway that is activated under certain stress conditions and is regulated by the repressor LexA and the activator RecA. The food-borne pathogen Listeria monocytogenes contains RecA and LexA homologs, but their roles in Listeria have not been established. In this study, we identified the SOS regulon in L. monocytogenes by comparing the transcription profiles of the wild-type strain and the ΔrecA mutant strain after exposure to the DNA damaging agent mitomycinC (MMC). The SOS response is an inducible pathway involved in DNA repair, restart of stalled replication forks, and in induction of genetic variation in stressed and stationary phase cells. It is regulated by LexA and RecA. LexA is an autoregulatory repressor which binds to a consensus sequence in the promoter region of the SOS response genes, thereby repressing transcription. A consensus LexA binding motif for L. monocytogenes has not been identified thus far. Generally, the SOS response is induced under circumstances in which single stranded DNA accumulates in the cell. This results in activation of RecA, which in turn stimulates cleavage of LexA, and ultimately in the induction of the SOS response. Keywords: stress response, loop design, SOS response, mitomycin c, listeria monocytogenes, RecA, LexA
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.