Unknown,Transcriptomics,Genomics,Proteomics

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Polyamines induce the glutamate decarboxylase acid response system by increasing the level of the σ38 subunit (RpoS) of Escherichia coli RNA polymerase via gadE regulon

ABSTRACT: To study the physiological roles of polyamines, we have carried out a global microarray analysis on the effect of adding polyamines to an Escherichia coli mutant that lacks polyamines because of deletions in the genes in the polyamine biosynthetic pathway. Previously, we have reported that the earliest response to the polyamine addition is the increased expression of the genes for the glutamate dependent acid resistance system (GDAR). We also presented preliminary evidence for the involvement of rpoS and gadE regulators. In the current study further confirmation of the regulatory roles of rpoS and gadE is shown by a comparison of genome-wide expression profiling data from a series of microarrays comparing the genes induced by polyamine addition to polyamine-free rpoS+/gadE+ cells with genes induced by polyamine addition to polyamine-free ∆rpoS and ∆gadE cells. The results indicate that most of the genes in the E. coli GDAR system that are induced by polyamines require rpoS and gadE. Our data also show that, gadE is the main regulator of GDAR and other acid-fitness-island genes. Both polyamines and rpoS are necessary for the expression of gadE genes from the three promoters of gadE (P1, P2 and P3). The most important effect of polyamine addition is the very rapid post-transcriptional increase in the level of RpoS sigma factor. Our current hypothesis is that polyamines increase the level of RpoS protein, and that this increased RpoS level is responsible for the stimulation of gadE expression, which in turn induces the GDAR system in E. coli. Three replications for E. coli strains HT874, HT873, HT875, HT873 treated with or no polyamines(PA)

ORGANISM(S): Escherichia coli

SUBMITTER: WeiPing Chen

PROVIDER: E-GEOD-67119 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Polyamines Stimulate the Level of the σ38 Subunit (RpoS) of Escherichia coli RNA Polymerase, Resulting in the Induction of the Glutamate Decarboxylase-dependent Acid Response System via the gadE Regulon.

Chattopadhyay Manas K MK Keembiyehetty Chithra N CN Chen Weiping W Tabor Herbert H

The Journal of biological chemistry 20150529 29

To study the physiological roles of polyamines, we carried out a global microarray analysis on the effect of adding polyamines to an Escherichia coli mutant that lacks polyamines because of deletions in the genes in the polyamine biosynthetic pathway. Previously, we have reported that the earliest response to polyamine addition is the increased expression of the genes for the glutamate-dependent acid resistance system (GDAR). We also presented preliminary evidence for the involvement of rpoS and ...[more]

PMID: 26025365

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Project description:There is increasing evidence to support a role for sigma factor 54 (RpoN) in the regulation of stress resistance factors and protein secretion systems important to bacterial transmission and pathogenesis. In enterohemorrhagic E. coli O157:H7, acid resistance and type III secretion are essential determinants of gastric passage and colonization. This study thus described the transcriptome of an rpoN null strain of E. coli O157:H7 (EcJR-8) to determine the influence of RpoN on virulence and stress resistance gene regulation, and further explored its contribution to glutamate-dependent acid resistance (GDAR). Inactivation of rpoN resulted in the growth phase-dependent, differential expression of 104 genes. This included type III secretion structural and regulatory genes encoded on the locus of enterocyte effacement (LEE), as well as GDAR genes gadA, gadBC and gadE. Upregulation of gad transcript levels in EcJR-8 during logarithmic growth correlated with increased GDAR and survival in a model stomach. Acid susceptibility was reconstituted in EcJR-8 complemented in trans with wild-type rpoN. Acid resistance in EcJR-8 was dependent on exogenous glutamate, gadE and rpoS, but was independent of hns. Results also suggest that GDAR may be controlled by RpoN at multiple regulatory levels. This study supports the hypothesis that RpoN is an important regulator of virulence and stress resistance factors in E. coli O157:H7, and is the first to examine the mechanism by which it represses GDAR. Hybridizations measured transcriptional differences between an rpoN null and wild-type (WT) strain of E. coli O157:H7 Sakai at logarithmic and transition phase. Image files (TIFF) of hybridized microarray slides were generated using an Axon 4000B scanner (Molecular Devices), and analyzed using GenePix Pro software (Molecular Devices, ver. 6.0). The resulting microarray intensity data was log2-transformed, and normalized using the LOWESS algorithm in MAANOVA ver. 0.98-8 (R ver. 2.2.1).

Dataset Information

Polyamines induce the glutamate decarboxylase acid response system by increasing the level of the σ38 subunit (RpoS) of Escherichia coli RNA polymerase via gadE regulon

Publications

Polyamines Stimulate the Level of the σ38 Subunit (RpoS) of Escherichia coli RNA Polymerase, Resulting in the Induction of the Glutamate Decarboxylase-dependent Acid Response System via the gadE Regulon.

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