Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Response and adaptation to growth with low glucose concentration

ABSTRACT: The faecal indicator bacterium Escherichia coli K12 was used to study the cellular events that take place at the transcription level using the microarray technology during short-term (physiological) and long-term (genetic) adaptation to slow growth under limited nutrient supply. Short-term and long-term adaptation were assessed by comparing the mRNA levels isolated after 40 or 500 hours of glucose-limited continuous culture at a dilution rate of 0.3 h-1 with those from batch culture with glucose excess. Wild-type Escherichia coli K12 MG 1655 (ATCC 700926) was grown at 37 Â°C in mineral medium. Growth was followed by measuring OD546 in regular intervals to confirm that cells were growing at ï?max (0.63 Â± 0.02 h-1). A sample for transcriptome analysis was taken from the batch exponential phase at an OD546 of ï?¾ 0.4, and immediately after sampling the medium flow was started for continuous cultivation with a dilution rate of 0.3 h-1. Steady-state with respect to biomass and residual glucose concentrations was reached approximately 15 hours after this manipulation. 40 and 500 hours after switching to the glucose-limited continuous culture mode 800 ml of culture liquid was withdrawn from the chemostat, immediately cooled down on crushed ice and cells were collected by centrifugation at 4 Â°C. Total RNA from E. coli cells was isolated as described earlier (Sambrook et al., 1989). RNA in samples was quantified spectrophotometrically by measuring extinction at 260 nm and purity (free from DNA) was checked by gel electrophoresis. Synthesis of cDNA from RNA was performed with the CyScribe First-Strand cDNA Labelling Kit (Amersham Bioscience, Little Chalfont, England). The purified cDNA was concentrated to 5 Î¼l and was mixed with 120 Î¼l of hybridization buffer (MWG-Biotech AG), heated to 95 Â°C for 3 min and cooled down on ice for 3 min. The hybridization mixture was then added to the microarray slide and covered with a coverslip. The hybridisation slide was incubated over night at 42 Â°C. After the hybridization step the slide was washed three times, the first time for 5 min in 2x (times concentrated) SSC - 0.1 % SDS, the second time for 5 min in 1x SSC, and finally for 5 min in 0.1x SSC. SSC buffer was prepared as 20x solution containing 0.3M Na-citrate and 3M NaCl at pH 7.0. The slides were dried by centrifugation at room temperature for 2 min at 500g. Microarray slides were scanned using the Affymetrix 428TM Array Scanner (High Wycombe, UK). Spot intensities and corresponding background signals were quantified with the Affymetrix JaguarTM software version 2.0. Further data analysis was performed with the program GeneSpring from Silicon Genetics (Redwood City, USA). Induction factors were calculated from the Cy3 and Cy5 signal intensities of the spot. Spots with signal intensity below a value of 50 were excluded from the analysis and the minimal induction factor was set to 0.01. The normalization was performed with the 50th percentile distribution of remaining spots after background correction. The mean value of the induction factors of a specific gene was calculated from three replicates. Biological experiments were carried out three times, which provided three biological repeats. Data from the independent experiments were combined, genes that were differentially regulated â?¥ 2 and â?¤ 0.5 (t-test, p â?¤ 0.05) were defined as being statistically significant.

ORGANISM(S): Escherichia coli

SUBMITTER: Alessandro Franchini

PROVIDER: E-GEOD-4706 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Global gene expression in Escherichia coli K-12 during short-term and long-term adaptation to glucose-limited continuous culture conditions.

Franchini Alessandro G AG Egli Thomas T

Microbiology (Reading, England) 20060701 Pt 7

Microarray technology was used to study the cellular events that take place at the transcription level during short-term (physiological) and long-term (genetic) adaptation of the faecal indicator bacterium Escherichia coli K-12 to slow growth under limited nutrient supply. Short-term and long-term adaptation were assessed by comparing the mRNA levels isolated after 40 or 500 h of glucose-limited continuous culture at a dilution rate of 0.3 h(-1) with those from batch culture with glucose excess. ...[more]

PMID: 16804185

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Project description:The faecal indicator bacterium Escherichia coli K12 was used to study the effects of the global regulators RpoS and cAMP at the transcription level using microarray technology during short-term (physiological) adaptation to slow growth under limited nutrient supply. Effects due to the absence of one global regulator were assessed by comparing the mRNA levels isolated from rpoS or cya mutants under glucose-limited continuous culture at a dilution rate of 0.3 h-1 for the rpoS mutant or 0.16 h-1 for the cya mutant with those from wt E. coli grown under the same conditions. Wild-type Escherichia coli K12 MG1655 (ATCC 700926), E. coli delta-rpoS (MG1655 delta-rpoS::Tn10; Wick et al. (2002)) and AMS2 (MG1655 delta-cya-854; Schultz et al. (1988)) were grown at 37°C in mineral medium. Steady-state with respect to optical density was reached approximately 20 hours after switching on the medium feed. Samples for catabolic pathway assays and transcriptome analysis were taken 40 hours after switching to the continuous culture mode, and each experiment was done in triplicate. 800 ml of culture liquid was withdrawn from the chemostat, immediately cooled down on crushed ice and cells were collected by centrifugation at 4°C. Total RNA from E. coli cells was isolated (Sambrook et al., 1989). RNA in samples was quantified spectrophotometrically by measuring extinction at 260 nm, and purity (free from DNA) was checked by gel electrophoresis. Synthesis of cDNA from RNA was performed with the CyScribe First-Strand cDNA Labelling Kit (Amersham Bioscience, Little Chalfont, England). The purified cDNA was concentrated to 5 ul and was mixed with 120 ul of hybridization buffer (MWG-Biotech AG), heated to 95°C for 3 min and cooled down on ice for 3 min. The hybridization mixture was then added to the microarray slide and covered with a coverslip. The hybridization slide was incubated overnight at 42°C. After the hybridization step, the slide was washed three times, the first time for 5 min in 2x (times concentrated) SSC - 0.1 % SDS, the second time for 5 min in 1x SSC, and finally for 5 min in 0.1x SSC. SSC buffer was prepared as 20x solution containing 0.3M Na-citrate and 3M NaCl at pH 7.0. The slides were dried by centrifugation at room temperature for 2 min at 500g. Microarray slides were scanned using the Affymetrix 428TM Array Scanner (High Wycombe, UK). Spot intensities and corresponding background signals were quantified with the Affymetrix JaguarTM software version 2.0. Further data analysis was performed with the program GeneSpring from Silicon Genetics (Redwood City, USA). Induction factors were calculated from the Cy3 and Cy5 signal intensities of the spot. Spots with signal intensity below a value of 50 were excluded from the analysis and the minimal induction factor was set to 0.01. The normalization was performed with the 50th percentile distribution of remaining spots after background correction. The mean value of the induction factors of a specific gene was calculated from three replicates. Biological experiments were carried out three times, which provided three biological repeats. Data from the independent experiment were combined, genes that were differently regulated ?3 and ?-3 (t-test, p ? 0.2) were defined as being statistically significant.

Project description:A time series of whole-genome transcription profiling of E. coli K-12 W3110 was performed to study the dynamic physiological response of E. coli K-12 W3110 to limited carbon conditions. cDNA from eight time intervals after glucose limitation, representing different stages of glucose depletion, along with cDNA of an unrestricted growth were hybridized to whole-genome microarrays of E. coli K-12. Glucose concentrations were gradually reduced in a fed-batch cultivation process with constant feeding rate in a bioreactor. Major focus was put on the dynamic changes in the transcription level of genes involved in the central carbon metabolism (glycolysis, pentose phosphate pathway, TCA cycle and glyoxylate shunt), high-affinity glucose transport systems, movement, growth, and stress response. In total, 40 microarrays were hybridized. The data were statistically analysed using the software R (R, 2005) and the Limma package included (Smyth, 2005). The data were normalized â??print-tip-loessâ??. â??Multiple hypothesis testingâ?? correction was performed with the method of Benjamini and Hochberg (Benjamini and Hochberg, 1995), which controls the â??false discovery rateâ?? (fdr). Genes were regarded as differentially expressed when the â??adjusted p valuesâ?? were < 0.05, therefore nominally controlling the expected fdr to less than 0.05. The reproducibility of dye swap experiments as well as biological replicates was estimated by calculating â??Pearsonâ??s correlation coefficientsâ??. A high correlation was observed for the dye swap pairs (with averaged Pearsonâ??s correlation coefficients of 0.89 Â± 0.06 for the reference samples and of 0.87 Â± 0.08 for the different points of time) as well as for biological replicates (with averaged Pearsonâ??s correlation coefficients of 0.86 Â± 0.04 for the red channel (Cy5) and 0.80 Â± 0.09 for the green channel (Cy3)). Benjamini, Y., and Hochberg, Y. (1995). Controlling the false discovery rate: A practical and powerful approach to multiple testing. J R Stat Soc B 57, 289-300. Smyth, G.K. (2005). Limma: Linear models for microarray data. In Bioinformatics and Computational Biology Solutions using R and Bioconductor, R. Gentleman, Carrey, V., Dudoit, S., Irizzary, I., Huber, W., ed. (New York, Springer), pp. 397-420. R (2005). R: A language and environment for statistical computing. (R Development Core Team). Supplementary files: Data_table_A: TabelleA_Signifikante.txt Description: Data table with coefficients of the linear model for every gene which was differentially expressed for at least one point in time according to the reference sample. The statistical analysis was performed as described in Series section (GSE10307) based on the normalized log2(test/ref) ratios in the Sample records' VALUE columns. Data_table_B1: Tabelle_B1; /E. coli/, unlimited growth via glucose limitation (glucose concentration < 0.05 gL-1) Data_table_B2: Tabelle_B2; /E. coli/, unlimited growth via glucose limitation, acetate concentration = 0.35 gL-1 Data_table_B3: Tabelle_B3; /E. coli/, unlimited growth via glucose limitation, 30 min after depletion of extracellular acetate Data_table_B4: Tabelle_B4; /E. coli/, unlimited growth via glucose limitation, 50 min after depletion of extracellular acetate Data_table_B5: Tabelle_B5; /E. coli/, unlimited growth via glucose limitation, 110 min after depletion of extracellular acetate Data_table_B6: Tabelle_B6; /E. coli/, unlimited growth via glucose limitation, 170 min after depletion of extracellular acetate Data_table_B7: Tabelle_B7; /E. coli/, unlimited growth via glucose limitation, 230 min after depletion of extracellular acetate Data_table_B8: Tabelle_B8; /E. coli/, unlimited growth via glucose limitation, 350 min after depletion of extracellular acetate Description: Data_tables_B1-B8 report statistical values (A: average intensity value (1/2log2(test*ref)); M: average expression value (log2(test/ref)), t and P.value ('adjusted P.value')) for every point in time (studied conditions are described above for the corresponding table). Every differentially expressed gene of the corresponding point in time according to the reference sample is listed. Genes were regarded as differentially expressed when their 'adjusted P.values' were < 0.05, therefore nominally controlling the expected fdr to less than 0.05. The data are based on maximal three biological replicates (three independent fed-batch cultivations). RT-PCR_results_7genes.txt and RT-PCR_protocol.PDF Keywords: Time course, stress response Hybridization involved the hybridization of a common reference (unlimited growth, batch phase) on all arrays together with each sample of interest. This allowed the direct comparison of the transcripts of a time series taken during fed-batch cultivation with the unlimited reference sample. All samples were taken in duplicates and the experiments were performed as dye swap experiments. The first four samples of the time series (T1 - T4) were taken from three individual fed-batch cultivations (three biological replicates), the subsequent four samples (T5 - T8) were taken only from two individual fed-batch cultivations. On each array, the genes were spotted in duplicates. Therefore, twelve replicates (duplicates on dye swaps for three cultivations) were analyzed for T1 â?? T4 and eight replicates (duplicates on dye swaps for two cultivations) were analyzed for T5 â?? T8.

Project description:Escherichia coli strain MG1655 was grown to mid-log phase in defined anaerobic media. One sample was treated with 100 ÂµM CORM-3, the other sample was a control. The volume (175 ml), temperature (37oC) and stirring (200 rpm) were constant. After 15 min of exposure to CO-RM, samples were taken from treated and control cells, harvested into ice cold phenol ethanol (187 Âµl phenol, 3.56 ml ethanol) to stabilize RNA, and total RNA was purified using Qiagenâs RNeasy Mini kit as recommended by suppliers. RNA was quantified using a BioPhotometer (Eppendorf). Biological experiments were carried out four times, and a dye swap performed for each experiment, providing two technical repeats for each of the four biological repeats. Cells were grown in defined minimal medium (anaerobic). Final concentrations are: glycerol (54 mM), K2HPO4 (23 mM), KH2HPO4 (7.3 mM), NH4Cl (18.7 mM), CaCl2 (69 ÂµM), K2SO4 (15 mM), sodium fumarate (50 mM), Luria Broth (5%) and can amino acids (0.1%). Trace elements were added at 10 ml per l; final concentrations are: 134 ÂµM EDTA, 31 ÂµM FeCl3, 6.15 ÂµM ZnO, CuCl2 0.57 ÂµM, CoNo3 0.34 ÂµM, 1.6 ÂµM H3BO3, 1 ÂµM ammonium molybdenate and 1 ÂµM sodium selenite. MgCl2 was added at 1 ml per l. All chemicals were of AnalaR grade of purity or higher. E. coli strain MG1655 was grown in mini fermenter vessels in 175 ml of the above defined minimal media (anaerobic). The vessel was continually sparged with N2 to ensure anaerobiosis. CORM-3 was added at a final concentration of 100 ÂµM, chosen because it causes only a slight reduction in the growth rate. Cells were grown to mid-log (OD600 of 0.4) before addition of CO-RM. For RNA extraction, 30 ml was harvested into ice cold phenol ethanol (187 Âµl phenol, 3.56 ml ethanol) to stabilize RNA, and total RNA was purified using Qiagenâs RNeasy Mini kit as recommended by suppliers. RNA was quantified using a BioPhotometer (Eppendorf). Biological experiments were carried out four times, and a dye swap performed for each experiment, providing two technical repeats for each of the four biological repeats. Equal quantities of RNA from control and CO-RM-treated cells were labelled by using nucleotide analogues of dCTP containing either Cy3 or Cy5 fluorescent dyes (Perkin Elmer). For each microarray slide, one sample was labelled with Cy3-dCTP, while the other sample was labelled with Cy5-dCTP. RNA (approximately 9 micrograms) was annealed to 4.5 micrograms pd(N)6 random hexamers (Amersham Biosciences) by heating at 65 oC for 10 min, followed by 10 min at 22 oC and cooling on ice for 2 min. This was supplemented with 6 microlitres of 5Ã First-strand buffer (Invitrogen), 2.5 microlitres dNTP mixture (5 mM each dATP, dTTP, dGTP and 2 mM dCTP), 3 microlitres 0.1 M DTT, 2 microlitres 1 mM Cy3 or Cy5 (Perkin Elmer) and 1.5 microlitre Superscript III reverse transcriptase (200 U) (Invitrogen). This was incubated at 42 oC for 3 hours. The reaction was terminated by the addition of NaOH (7.5 microlitres of 1M) and HCl (7.5 microlitres of 1M) before the addition of TE buffer (300 microlitres). Labelled cDNA was purified using a Qiaquick PCR purification kit (Qiagen). The Cy3-dCTP-labelled sample was mixed with the Cy5-dCTP-labelled sample, vacuum dried and re-suspended in 120 microlitres salt-based hybridisation buffer (supplied with the microarray slides). This was heated at 95 oC for 3 min then cooled on ice for 3 min. The mixture was pipetted onto a microarray slide, sealed with a GeneFrame and coverslip in a hybridization chamber and incubated for 18 h at 42 Â°C. Following hybridization, microarray slides (minus GeneFrame and coverslip) were washed in a series of pre-warmed (37 Â°C) SSC buffers for 5 min each at 37oC: 2Ã SSC/0.1 % SDS, 1Ã SSC, 0.2Ã SSC and 0.01Ã SSC. Microarray slides were dried by centrifugation at 1500 Ã g for 2 min before scanning. Slides were scanned on an Affymetrix 428 scanner. The average signal intensity and local background correction were obtained using a commercially available software package from Biodiscovery, Inc (Imagene, version 4.0 and GeneSight, version 3.5). Spots automatically flagged as bad, negative or poor in the Imagene software were removed before the statistical analysis was carried out in GeneSight. The mean values from each channel were log2 transformed and normalised using the Lowess method to remove intensity-dependent effects in the log2(ratios) values. The Cy3/Cy5 fluorescent ratios were calculated from the normalized values. Biological experiments (i.e. a comparison of control and plus CO-RM cells) were carried out four times, and a dye swap performed for each experiment, providing two technical repeats for each of the four biological repeats. Data from the independent experiments were combined. Genes that were differentially expressed â¥ twofold and displayed and P value of < 0.05 (as determined by a t test) were defined as being statistically significantly differentially transcribed.

Project description:Escherichia coli strain MG1655 was grown to mid-log phase in defined aerobic media. One sample was treated with 30 ÂµM CORM-3, the other sample was a control. The volume (30 ml), temperature (37oC) and shaking (200 rpm) were constant. After 15 min of exposure to CO-RM, samples were taken from treated and control cells, harvested into ice cold phenol ethanol (187 Âµl phenol, 3.56 ml ethanol) to stabilize RNA, and total RNA was purified using Qiagenâs RNeasy Mini kit as recommended by suppliers. RNA was quantified using a BioPhotometer (Eppendorf). Biological experiments were carried out four times, and a dye swap performed for each experiment, providing two technical repeats for each of the four biological repeats. Cells were grown in defined minimal medium (aerobic). Final concentrations are: glycerol (54 mM), K2HPO4 (23 mM), KH2HPO4 (7.3 mM), NH4Cl (18.7 mM), CaCl2 (69 ÂµM), and K2SO4 (15 mM). Trace elements were added at 10 ml per l; final concentrations are: 134 ÂµM EDTA, 31 ÂµM FeCl3, 6.15 ÂµM ZnO, CuCl2 0.57 ÂµM, CoNo3 0.34 ÂµM, 1.6 ÂµM H3BO3, 1 ÂµM ammonium molybdenate and 1 ÂµM sodium selenite. MgCl2 was added at 1 ml per l. All chemicals were of AnalaR grade of purity or higher. E. coli strain MG1655 was grown in 250 ml side arm flasks in 30 ml of the above defined minimal media (aerobic). CORM-3 was added at a final concentration of 30 ÂµM, chosen because it causes only a slight reduction in the growth rate. Cells were grown to mid-log (Klett values of 30-40) before addition of CO-RM. The total 30 ml volume was harvested into ice cold phenol ethanol (187 Âµl phenol, 3.56 ml ethanol) to stabilize RNA, and total RNA was purified using Qiagenâs RNeasy Mini kit as recommended by suppliers. RNA was quantified using a BioPhotometer (Eppendorf). Biological experiments were carried out four times, and a dye swap performed for each experiment, providing two technical repeats for each of the four biological repeats. Equal quantities of RNA from control and CO-RM-treated cells were labelled by using nucleotide analogues of dCTP containing either Cy3 or Cy5 fluorescent dyes (Perkin Elmer). For each microarray slide, one sample was labelled with Cy3-dCTP, while the other sample was labelled with Cy5-dCTP. RNA (approximately 9 micrograms) was annealed to 4.5 micrograms pd(N)6 random hexamers (Amersham Biosciences) by heating at 65 oC for 10 min, followed by 10 min at 22 oC and cooling on ice for 2 min. This was supplemented with 6 microlitres of 5Ã First-strand buffer (Invitrogen), 2.5 microlitres dNTP mixture (5 mM each dATP, dTTP, dGTP and 2 mM dCTP), 3 microlitres 0.1 M DTT, 2 microlitres 1 mM Cy3 or Cy5 (Perkin Elmer) and 1.5 microlitre Superscript III reverse transcriptase (200 U) (Invitrogen). This was incubated at 42 oC for 3 hours. The reaction was terminated by the addition of NaOH (7.5 microlitres of 1M) and HCl (7.5 microlitres of 1M) before the addition of TE buffer (300 microlitres). Labelled cDNA was purified using a Qiaquick PCR purification kit (Qiagen). The Cy3-dCTP-labelled sample was mixed with the Cy5-dCTP-labelled sample, vacuum dried and re-suspended in 120 microlitres salt-based hybridisation buffer (supplied with the microarray slides). This was heated at 95 oC for 3 min then cooled on ice for 3 min. The mixture was pipetted onto a microarray slide, sealed with a GeneFrame and coverslip in a hybridization chamber and incubated for 18 h at 42 Â°C. Following hybridization, microarray slides (minus GeneFrame and coverslip) were washed in a series of pre-warmed (37 Â°C) SSC buffers for 5 min each at 37oC: 2Ã SSC/0.1 % SDS, 1Ã SSC, 0.2Ã SSC and 0.01Ã SSC. Microarray slides were dried by centrifugation at 1500 Ã g for 2 min before scanning. Slides were scanned on an Affymetrix 428 scanner. The average signal intensity and local background correction were obtained using a commercially available software package from Biodiscovery, Inc (Imagene, version 4.0 and GeneSight, version 3.5). Spots automatically flagged as bad, negative or poor in the Imagene software were removed before the statistical analysis was carried out in GeneSight. The mean values from each channel were log2 transformed and normalised using the Lowess method to remove intensity-dependent effects in the log2(ratios) values. The Cy3/Cy5 fluorescent ratios were calculated from the normalized values. Biological experiments (i.e. a comparison of control and plus CO-RM cells) were carried out four times, and a dye swap performed for each experiment, providing two technical repeats for each of the four biological repeats. Data from the independent experiments were combined. Genes that were differentially expressed â¥ twofold and displayed and P value of < 0.05 (as determined by a t test) were defined as being statistically significantly differentially transcribed.

Project description:The widespread use of electricity raises the question of whether or not 50 Hz (power line frequency in Europe) magnetic fields (MFs) affect organisms. We investigated the transcription of Escherichia coli K-12 MG1655 in response to extremely low-frequency (ELF) MFs. Fields generated by three signal types (sinusoidal continuous, sinusoidal intermittent, and power line intermittent; all at 50 Hz, 1 mT), were applied and gene expression was monitored at the transcript level using an Affymetrix whole-genome microarray. Bacterial cells were grown continuously in a chemostat (dilution rate D = 0.4 h-1) fed with glucose-limited minimal medium and exposed to 50 Hz MFs with a homogenous flux density of 1 mT. For all three types of MFs investigated, neither bacterial growth (determined using optical density) nor culturable counts were affected. Likewise, no statistically significant change (fold-change > 2, P ≤ 0.01) in the expression of 4,358 genes and 714 intergenic regions represented on the gene chip was detected after MF exposure for 2.5 h (1.4 generations) or 15 h (8.7 generations). Moreover, short-term exposure (8 min) to the sinusoidal continuous and power line intermittent signal neither affected bacterial growth nor showed evidence for reliable changes in transcription. In conclusion, our experiments did not indicate that the different tested MFs (50 Hz, 1 mT) affected the transcription of E. coli. A total of 60 chips are included in this study. Each comparison (treated vs. sham-treated cultures; untreated negative control cultures) consists of three replicates. The three magnetic field test conditions include sinusoidal continous, sinusoidal intermittent (2 min on, 4 min off) and power line intermittent (2 min on, 4 min off). Exposure periods were 8 min, 2.5 h, or 15 h. The response control consists of E. coli cells treated for 10 min with 1 mM H2O2 or the equivalent water volume. The negative control comprises samples taken from cultures grown with the exposure chambers swiched off.

Dataset Information

Response and adaptation to growth with low glucose concentration

Publications

Global gene expression in Escherichia coli K-12 during short-term and long-term adaptation to glucose-limited continuous culture conditions.

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