RNAseq of uropathogenic E. coli strain EO399, grown in conditions resembling passage through the gut; coli was grown in the presence or absence of 1 of 3 organic acids (acetic, butyric or propionic) at pH5.5 or pH7 and in aerobic or anaerobic conditions
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ABSTRACT:
INSTRUMENT(S): Illumina HiSeq 2500
ORGANISM(S): Escherichia coli
SUBMITTER: John Herbert
PROVIDER: E-MTAB-9762 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Enterohemorrhagic Escherichia coli (EHEC), including serotype O157:H7, cause severe food-borne illness. On route to the human colon, they encounter and resist, numerous anti-microbial ingestion stresses. We hypothesize that these stresses cue EHEC to alter virulence properties. This study investigated the impact of bile salts on virulence properties and examined the genetic basis of the phenotypes. Established assays were used to examine adhesion to human epithelial cells, motility, verotoxin (VT) production and antimicrobial resistance with/without bile salt stress. Bacteria treated for 90 minute in DMEM plus 0.15% (w/v) bile salt mix demonstrated significantly enhanced adhesion to epithelial cells and resistance to several antibiotics but did not increase motility or VT production. To determine the genetic basis of these phenotypes a microarray experiment was conducted. EHEC strain 86-24, in mid-log phase of growth, were grown in DMEM pH 7.4 (control), or DMEM plus bile salt mix (0.15% w/v), for 90 minutes, statically at 37˚C, 5% CO2 prior to harvesting RNA for the microarray study. Four biological replicates were produced for each treatment. Microarray and gene expression analysis (semi-quantitative RT-PCR and beta-galactosidase reporter assays) of bile salt-treated EHEC revealed significant up-regulation of genes for lipid A modification, fimbriae, an efflux pump, and a two-component regulatory system relative to the bacteria grown in DMEM alone. This work points to several mechanisms that EHEC employs to resist the stresses of the human small intestine, notably efflux, antimicrobial resistance, and outer membrane alterations. Bile salts enhanced the virulence-related properties of increased adhesion and resistance to antimicrobials but not VT production or motility. This research contributes to our understanding of how EHEC senses and responds to host environmental signals and the mechanisms this pathogen uses to successfully colonize and infect the human host. Bacteria were grown in LB broth overnight with shaking, then subcultured into DMEM and grown statically at 37˚C, 5%CO2 to mid-log phase. Bacteria were then subjected to one of two 90 minute treatments: 1) Control: DMEM pH 7.4, or 2) Bile Salt Stress: DMEM pH 7.4 plus 0.15%, grown statically at 37˚C, 5%CO2.
2011-09-05 | E-GEOD-22060 | biostudies-arrayexpress
Project description:Aims: Coagulase negative Staphylococcus xylosus strains are used as starter organisms for sausage fermentation. As those strains have to cope with low pH-values during fermentation, the aim of this study was to identify the acid adaptation mechanisms of S. xylosus TMW 2.1523 previously isolated from salami. Methods and Results: A comparative proteomic study between two different acid tolerant mutants was performed. Therefore, both S. xylosus mutants were grown pH-static under acid stress (pH 5.1) and reference conditions (pH 7.0). Proteomic data were supported by metabolite and cell membrane lipids analyses. S. xylosus acid stress adaptation is mainly characterized by a metabolic change towards neutral metabolites, enhanced urease activity, reduced ATP consumption, an increase in membrane fluidity and changes of the membrane thickness. Conclusion: This study corroborates mechanisms as previously described for other Gram-positive bacteria. Additionally, the adjustment of membrane structure and composition in S. xylosus TMW 2.1523 play a prominent role in its acid adaptation. Significance and Impact of the Study: This study demonstrates for the first time changes of the membrane lipid composition due to acid stress adaptation in staphylococci.
2019-02-22 | PXD012823 | Pride
Project description:The human pathogen, Mycobacterium tuberculosis, develops a dormant infection, in which organisms survive within the body. We established a unique in vitro dormancy model based on the characterization of drug-resistance to INH and rifampin. M. tuberculosis cells were maintained in controlled and defined multiple stress conditions with low oxygen (5% dissolved oxygen tension), acid (pH 5.) along with glycerol-deprived medium conditions. To monitor gene expression changes in M. tuberculosis in response to the multiple stresses, we performed microarray analysis at the time point of 1, 2, 3, 6, and 12days after treatment. M. tuberculosis adapting to multiple stresses displayed characteristics associated with persistence in vivo, including entry into a non-replicative state and the repression of genes involved in energy regeneration. Under in vitro multiple-stresses, M. tuberculosis significantly modulated gene expression mainly in response to the starvation stresses. Cells exposed to these multiple stress conditions shows significant drug-resistance. Comparison with other in vivo expression profiles demonstrates induction of several common genes for in vitro dormancy conditions. Keywords: Stress response in time course. Samples under multiple stress condition were taken at day 1, 2, 3, 6, and 12 for microarray hybridization. More than two technical replicates per biological samples with Cy3/5 dye-swaps.
2008-05-01 | E-GEOD-10391 | biostudies-arrayexpress
Project description:Metals at high concentrations can exert toxic effects on microorganisms. It has been widely reported that lowering environmental pH reduces effects of cadmium toxicity in bacteria. Understanding the effects of pH-mediated cadmium toxicity on bacteria would be useful for minimizing cadmium toxicity in the environment and gaining insight into the interactions between organic and inorganic components of life. Growth curve analysis confirmed that cadmium was less toxic to Escherichia coli at pH 5 than at pH 7 in M9 minimal salts medium. To better understand the cellular mechanisms by which lowering pH decreases cadmium toxicity, we used DNA microarrays to characterize global gene expression patterns in E. coli in response to cadmium exposure at moderately acidic (5) and neutral (7) values of pH. Higher expression of several stress response genes including hdeA, otsA, and yjbJ at pH 5 after only 5 minutes was observed and may suggest that acidic pH more rapidly induces genes that confer cadmium resistance. Genes involved in transport were more highly expressed at pH 7 than at pH 5 in the presence of cadmium. Of the genes that showed an interaction between pH and cadmium effects, 46% encoded hypothetical proteins, which may have novel functions involved in mitigating cadmium toxicity. GROWTH CONDITIONS FOR MICROARRAY EXPERIMENTS: Two overnight cultures of E. coli K-12 were started in M9 medium. A 250 mL Erlenmeyer flask containing 100 mL of M9 medium was inoculated with 0.5 mL for each of the two overnight cultures, each of which was considered a biological replicate. The cultures were grown on a rotary shaker (200 rpm) at 37 °C until the contents of the flask reached an OD600 of 0.3 (mid-log phase of growth). Each culture was divided into four 25 mL aliquots, transferred to 50 mL conical tubes (Corning), and centrifuged at 2540 x g for 12 minutes. The supernatant was decanted, and the cells were resuspended in 25 mL of M9 medium at pH 7 or pH 5 in the presence or absence (two cultures of each) of 5.4 µM (1 µg/mL) total cadmium, added as CdCl2. The cultures were incubated at 25 °C for either 5 or 15 minutes with manual rotation of the flasks once per minute. After the appropriate amount of time, 15 mL of RNAProtect Bacteria Reagent (Qiagen) was added to each culture to immediately halt all metabolic processes. The solutions were vortexed, incubated at 25 °C for 5 minutes, and centrifuged for 12 minutes at 3750 x g. RNA was extracted from the cell pellets immediately following centrifugation. RNA EXTRACTION AND HYBRIDIZATION PROCEDURES: RNA was extracted and purified using a Masterpure RNA purification kit (Epicentre Technologies). The quantity and quality of the RNA samples were determined spectrophotometrically. Preparation of the cDNA, labeling with Cy3 and Cy5, and successive hybridizations were accomplished using a 3DNA Array 900MPX kit following the manufacturer’s protocols (Genisphere) with the following modifications. 3DNA reverse transcriptase enzyme (Genisphere # RT300320) rather than SuperScript II was added to 1 µg of RNA and 2 µL of a random primer (1 µg/µL). The final cDNA hybridization mix contained 29 µL 2X enhanced cDNA hybridization buffer rather than 2X SDS-based hybridization buffer or 2X formamide-based hybridization buffer. The cDNA mix was hybridized to a cDNA microarray printed by the Microarray and Proteomics Facility at the University of Alberta (Operon version 1.0 oligonucleotides). The arrays were scanned with a Versarray ChipReader (BioRad) with laser power at 75%, photomultiplier tube (PMT) sensitivity at 800 V, and detector gain at 1. DATA ANALYSIS: Each array directly compared transcription at pH 5 and pH 7 for a given cadmium treatment (0 or 5.4 µM cadmium) and exposure time. Dye swaps were performed for each biological replicate for each of the following treatments (8 total arrays): 5 minutes with cadmium exposure, 5 minutes without cadmium exposure, 15 minutes with cadmium exposure, and 15 minutes without cadmium exposure. The 0-minute exposure to cadmium treatment was obtained from the 5-minute microarray without cadmium exposure. Spot intensities and locations were determined using TIGR Spotfinder, Version 3.1.1. All subsequent analyses were performed using the ma-anova package in the open-source statistical software package, R (www.r-project.org), Version 2.4.1. The data were normalized using the regional lowess method. Following normalization the median expression values of genes represented in triplicate on each array were determined for each gene. A mixed model two-way ANOVA for the main fixed effects of pH, cadmium, and their interaction (array and spot were the random effects) were performed (using Type III F-tests) separately for each time point to identify genes for which pH and cadmium interacted to significantly affect expression (FDR-adjusted p ? 0.05).
2008-08-21 | E-GEOD-12373 | biostudies-arrayexpress
Project description:Here we present molecular mechanisms of Korean red ginseng (KRG) on immobilization stresses Keywords: stress response Mice were divided into three groups (3 mice / group): control, stress + no treat, and stress + Korean Red Ginseng (KRG, 100 mg). Stress + KRG group were given KRG 100 mg orally for 7 days and then exposed to immobilization stress for 45 min. stress + no treat group were administrated with phosphate buffer saline (d-PBS, pH 7.4) together with IMO stress for 45 min.
2010-05-15 | E-GEOD-12656 | biostudies-arrayexpress
Project description:Escherichia coli O157:H7 has caused serious outbreaks of foodborne illness via transmission in a variety of food vehicles, including unpasteurized apple juice, dried salami, and spinach. To understand how this pathogen responds to the multiple stresses of the food environment, we compared global transcription patterns after exposure to apple juice. Transcriptomes of mid-exponential and stationary phase cells were evaluated after 10 minutes in model apple juice (pH3.5) using microarrays probing 4,886 ORFs. Significant changes in gene expression were determined using R/MAANOVA and the Fs test. A total of 331 ORFs were significantly induced upon exposure of cells to model apple juice and included genes involved in the acid and osmotic stress responses as well as the oxidative stress response and envelope stress. Genes involved in the acid and osmotic stress responses, including asr, osmC, osmB, and osmY were significantly induced in response to model apple juice. Genes involved in the envelope stress response, known to be controlled by CpxR (cpxP, degP, and htpX), were significantly induced 2 to 15 fold upon exposure to apple juice, independent of growth phase. Inactivation of CpxRA resulted in a significant decrease in survival of O157:H7 in model apple juice compared to the isogenic parent strain. Of the 331 ORFs induced in model apple juice, 104 are O157-specific ORFs, including those encoding type three secretion effectors espJ, espB, espM2, espL3 and espZ. By elucidating the response of O157:H7 to acidic foods, we hope to gain insights into how this pathogen is able to survive in food matrices and how exposure to foods affects subsequent transmission and virulence. Keywords: stress The results are based on O157:H7 Sakai exponential and stationary phase cultures grown in MOPS minimal medium and then exposed to model apple juice (pH 3.5, 37C) for 10 minutes. Differences in transcript levels were determined using a mixed model ANOVA in R/MAANOVA which tested for significant differences due to growth phase (exponential or stationary), treatment (MOPS or MAJ) and the interaction of these two factors using the following linear model: array+dye+sample (biological replicate)+ phase+treatment+phase*treatment. We incorporated the dye-swaps among the biological replicates.
2010-05-25 | E-GEOD-11052 | biostudies-arrayexpress
Project description:While significant advances have been made in EHEC pathogenesis, we still do not fully understand the impact of environmental stress on EHEC virulence. During the course of infection, EHEC must evade or overcome several biological barriers, the first of which is the gastric acidity encountered during passage through the stomach. EHEC is remarkable in its ability to tolerate this acidity. There are four different acid resistance systems that provide E. coli O157:H7 protection against exposure to low pH (2-2.5). Interestingly, EHEC uses these acid resistance systems differentially for survival in foods versus the bovine intestinal tract. The glutamate-dependent acid-resistance system is thought to offer the best protection below pH 3. Since the infectious dose of EHEC is so low (50-100 organisms), acid resistance becomes an important virulence trait. Studies of EHEC response to acid stress have focused primarily on levels of acid tolerance and the molecular basis of tolerance. However, the impact of acid stress on EHEC virulence is less well understood. In the related pathogen, EPEC, the plasmid-encoded regulator, Per, that regulates expression of many EPEC virulence factors, is regulated negatively at pH 5.5 and positively at pH 8.0, suggesting that virulence gene expression is repressed during mild acid stress and enhanced in alkaline pH typical of the small intestine. Expression of EPEC type III secreted factors involved in A/E lesion formation has been shown to be influenced by factors including culture media, iron and calcium levels. Protein secretion was inhibited at pH 6 and 8. In a third study, a gadE (encoding acid resistance regulator) mutation resulted in increased adhesion of E.coli O157:H7 to colonic epithelial cells, suggesting negative regulation of one or more adhesins. Other studies have reported that shiga toxin production is sensitive to culture conditions including pH. However, there are no studies of EHEC virulence changes after more severe acid stress nor studies linking stressed EHEC virulence phenotype with transcriptional changes. The goal of this study was to determine how acid stress affects EHEC virulence properties and through microarray analysis, define the genetic basis for these changes. Understanding how acid stress modulates the virulence potential of this pathogen is essential for delineating the pathogenesis of disease caused by EHEC infection and may offer novel approaches to prevent and treat EHEC infections. Bacteria were grown in LB broth overnight, then subcultured into DMEM and grown at 37C, 5%Co2. Bacteria were then subjected to one of three acid stress protocols: 1) UA30: growth in DMEM pH 7.4 followed by growth in DMEM pH 3.0 for 30 minutes; 2) AA30: growth in DMEM pH 5.0 (adaptation) followed by growth in DMEM pH 3.0; 3) UA15: growth in DMEM pH 7.4 followed by growth in DMEM pH 3.0 for 15 minutes. DMEM was supplemented with 25 mM MES (pH 5.0) and in the case of the control (unadapted, unshocked) 25 mM MOPS (pH 7.4) and the adaptation step was again carried out at 37C and 5% CO2. Acid shocking was done at pH 3.0 (unbuffered) at room temperature for all treatments
2010-05-16 | E-GEOD-14069 | biostudies-arrayexpress
Project description:While in transit within and between hosts, uropathogenic E. coli (UPEC) encounter multiple stresses, including substantial levels of nitric oxide and reactive nitrogen intermediates. Strains of UPEC become conditioned to high concentrations of acidified sodium nitrite (ASN), a model system used to generate nitrosative stress. We used microarrays to define the expression profile of UPEC that have been conditioned for growth in ASN. Experiment Overall Design: Separate colonies of the UPEC isolate UTI89 grown on LB agar plates from a -80°C freezer stock were used to start overnight shaking cultures in MES-buffered LB broth (MES-LB, pH 5.0). Each culture was then diluted 1:100 into 7 ml MES-LB with or without 3 mM ASN in loosely capped 20-by-150-mm borosilicate glass tubes and grown with shaking at 37°C. Growth was monitored by optical density until OD600 = 1.5, at which point cultures were spun down, and pellets frozen at -80°C for at least 12 h. RNA was extracted with hot phenol-chloroform and purified by CsCl centrifugation. cDNA was synthesized, fragmented, and labeled for hybridization to Affymetrix GeneChip® E. coli Genome 2.0 Arrays.
2009-03-28 | E-GEOD-15319 | biostudies-arrayexpress
Project description:Reg1 is a regulatory subunit of Glc7, the type 1 Ser/Thr protein phosphatase in the yeast Saccharomyces cerevisiae. The Reg1/Glc7 complex is responsible for the dephosphorylation and inactivation of the Snf1 protein kinase, thus controlling Snf1 functions (i.e. expression of glucose-repressed genes). Snf1 is also involved in the response to certain stresses, such as alkaline pH. Surprisingly, both snf1 and reg1 mutants are hypersensitive to high pH. We show here that this phenotype in the reg1 strain is unrelated to the role of Reg1 in regulating Snf1, but depends on the ability of Reg1 to interact with Glc7. Transcriptomic profiling of reg1 cells in the absence or the presence of high pH stress and biochemical analyses suggest that lack of Reg1 impedes the normal downregulation of Pma1 in response to high pH stress. Our results highlight a role of Reg1/Glc7 in the regulation of Pma1 function and hence in the overall cellular cation homeostatic mechanisms. We identified the transcription pattern of reg1 cells (2 chips). We also identified the changes in the expression profiles caused by alkalinization of the medium (pH8 vs. pH5.5 for 10 min) in the reg1 strain (2chips) Total: 4 chips Changes in the transcriptomic profile in WT cells cause by alkalinization of the medium are included in Series GSE25697 (GSM631186, GSM631187, GSM631188 and GSM631189)
2014-10-31 | E-GEOD-36251 | biostudies-arrayexpress
Project description:Exposure of Saccharomyces cerevisiae to alkaline pH represents a stress condition that generates a compensatory reaction. Here we examine a possible role of the protein kinase-A (PKA) pathway in this response. The phenotypic analysis reveals that mutations that activate the PKA pathway (ira1 ira2, bcy1) tend to cause sensitivity to alkaline pH, whereas its deactivation develops tolerance to this stress. We observe that alkalinization causes a transient decrease in cAMP, the main regulator of the pathway. Alkaline pH causes rapid nuclear localization of the PKA-regulated Msn2 transcription factor which, together with Msn4, mediates a general stress response by binding to STRE sequences in many promoters. Consequently, a synthetic STRE-LacZ reporter shows a rapid induction in response to alkaline stress. An msn2 msn4 mutant is sensitive to alkaline pH, and transcriptomic analysis reveals that after 10 minutes of alkaline stress, the expression of many induced genes (47%) depends, at least in part, on the presence of Msn2 and Msn4. Taken together, these results demonstrate that inhibition of the PKA pathway by alkaline pH represents a substantial part of the adaptive response to this kind of stress and that this response involves Msn2/Msn4-mediated gene remodeling. However, the relevance of attenuation of PKA in high pH tolerance is not restricted to regulation of Msn2 function. Eight samples were analyzed: WT and the MCY5278 mutant strain, lacking both Msn2 and Msn4, in the presence of 20 mM KOH (pH 8) and in the presence of 20 mM KCl (non-induced conditions) for 10 and 30 min of stress. 2 biological replicates were analyzed for each condition, and dye-swapping was carried out for each comparison of samples. We compared the expression profiles of: 1) WT +KOH vs. WT +KCl after 10 min 2) msn2 msn4 mutant +KOH vs. msn2 msn4 +KCl after 10 min 3)WT +KOH vs. WT +KCl after 30 min 4) msn2 msn4 mutant +KOH vs. msn2 msn4 +KCl after 30 min Total number of chips analyzed: 16.
2011-07-15 | E-GEOD-27925 | biostudies-arrayexpress