scholarly journals A Caulobacter crescentus Extracytoplasmic Function Sigma Factor Mediating the Response to Oxidative Stress in Stationary Phase

2006 ◽  
Vol 188 (5) ◽  
pp. 1835-1846 ◽  
Author(s):  
Cristina E. Alvarez-Martinez ◽  
Regina L. Baldini ◽  
Suely L. Gomes
Keyword(s):  
Oxidative Stress ◽  
Stationary Phase ◽  
Stress Responses ◽  
Sigma Factor ◽  
Caulobacter Crescentus ◽  
Mrna Levels ◽  
Posttranscriptional Control ◽  
Hydrogen Peroxide Treatment ◽  
Extracytoplasmic Function Sigma Factor ◽  
Null Strain

ABSTRACT Alternative sigma factors of the extracytoplasmic function (ECF) subfamily are important regulators of stress responses in bacteria and have been implicated in the control of homeostasis of the extracytoplasmic compartment of the cell. This work describes the characterization of sigF, encoding 1 of the 13 members of this subfamily identified in Caulobacter crescentus. A sigF-null strain was obtained and shown to be severely impaired in resistance to oxidative stress, caused by hydrogen peroxide treatment, exclusively during the stationary phase. Although sigF mRNA levels decrease in stationary-phase cells, the amount of σF protein is greatly increased at this stage, indicating a posttranscriptional control. Data obtained indicate that the FtsH protease is either directly or indirectly involved in the control of σF levels, as cells lacking this enzyme present larger amounts of the sigma factor. Increased stability of σF protein in stationary-phase cells of the parental strain and in exponential-phase cells of the ftsH-null strain is also demonstrated. Transcriptome analysis of the sigF-null strain led to the identification of eight genes regulated by σF during the stationary phase, including sodA and msrA, which are known to be involved in oxidative stress response.

The ECF sigma factor σTis involved in osmotic and oxidative stress responses in Caulobacter crescentus

2007 ◽  
Vol 66 (5) ◽  
pp. 1240-1255 ◽  
Author(s):  
Cristina E. Alvarez-Martinez ◽  
Rogério F. Lourenço ◽  
Regina L. Baldini ◽  
Michael T. Laub ◽  
Suely L. Gomes
Keyword(s):  
Oxidative Stress ◽  
Stress Responses ◽  
Sigma Factor ◽  
Caulobacter Crescentus ◽  
Ecf Sigma Factor ◽  
Oxidative Stress Responses ◽  
And Oxidative Stress

scholarly journals Environmental Conditions Modulate the Transcriptomic Response of Both Caulobacter crescentus Morphotypes to Cu Stress

2021 ◽  
Vol 9 (6) ◽  
pp. 1116
Author(s):  
Laurens Maertens ◽  
Pauline Cherry ◽  
Françoise Tilquin ◽  
Rob Van Houdt ◽  
Jean-Yves Matroule
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Stress Responses ◽  
Caulobacter Crescentus ◽  
Oxidative Stress Response ◽  
Transport Systems ◽  
Transcriptomic Response ◽  
Swarmer Cell ◽  
Cu Stress ◽  
Cellular Environment

Bacteria encounter elevated copper (Cu) concentrations in multiple environments, varying from mining wastes to antimicrobial applications of copper. As the role of the environment in the bacterial response to Cu ion exposure remains elusive, we used a tagRNA-seq approach to elucidate the disparate responses of two morphotypes of Caulobacter crescentus NA1000 to moderate Cu stress in a complex rich (PYE) medium and a defined poor (M2G) medium. The transcriptome was more responsive in M2G, where we observed an extensive oxidative stress response and reconfiguration of the proteome, as well as the induction of metal resistance clusters. In PYE, little evidence was found for an oxidative stress response, but several transport systems were differentially expressed, and an increased need for histidine was apparent. These results show that the Cu stress response is strongly dependent on the cellular environment. In addition, induction of the extracytoplasmic function sigma factor SigF and its regulon was shared by the Cu stress responses in both media, and its central role was confirmed by the phenotypic screening of a sigF::Tn5 mutant. In both media, stalked cells were more responsive to Cu stress than swarmer cells, and a stronger basal expression of several cell protection systems was noted, indicating that the swarmer cell is inherently more Cu resistant. Our approach also allowed for detecting several new transcription start sites, putatively indicating small regulatory RNAs, and additional levels of Cu-responsive regulation.

scholarly journals Carbon Storage Regulator A Contributes to the Virulence of Haemophilus ducreyi in Humans by Multiple Mechanisms

2012 ◽  
Vol 81 (2) ◽  
pp. 608-617 ◽  
Author(s):  
Dharanesh Gangaiah ◽  
Wei Li ◽  
Kate R. Fortney ◽  
Diane M. Janowicz ◽  
Sheila Ellinger ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stationary Phase ◽  
Carbon Storage ◽  
Stress Responses ◽  
Haemophilus Ducreyi ◽  
Content Type ◽  
Enhanced Sensitivity ◽  
Significant Survival ◽  
Carbon Storage Regulator ◽  
Mutant Phenotypes

ABSTRACTThe carbon storage regulator A (CsrA) controls a wide variety of bacterial processes, including metabolism, adherence, stress responses, and virulence.Haemophilus ducreyi, the causative agent of chancroid, harbors a homolog ofcsrA. Here, we generated an unmarked, in-frame deletion mutant ofcsrAto assess its contribution toH. ducreyipathogenesis. In human inoculation experiments, thecsrAmutant was partially attenuated for pustule formation compared to its parent. Deletion ofcsrAresulted in decreased adherence ofH. ducreyito human foreskin fibroblasts (HFF); Flp1 and Flp2, the determinants ofH. ducreyiadherence to HFF cells, were downregulated in thecsrAmutant. Compared to its parent, thecsrAmutant had a significantly reduced ability to tolerate oxidative stress and heat shock. The enhanced sensitivity of the mutant to oxidative stress was more pronounced in bacteria grown to stationary phase compared to that in bacteria grown to mid-log phase. ThecsrAmutant also had a significant survival defect within human macrophages when the bacteria were grown to stationary phase but not to mid-log phase. Complementation intranspartially or fully restored the mutant phenotypes. These data suggest that CsrA contributes to virulence by multiple mechanisms and that these contributions may be more profound in bacterial cell populations that are not rapidly dividing in the human host.

scholarly journals The Mycobacterium tuberculosis Extracytoplasmic-Function Sigma Factor SigL Regulates Polyketide Synthases and Secreted or Membrane Proteins and Is Required for Virulence

2005 ◽  
Vol 187 (20) ◽  
pp. 7062-7071 ◽  
Author(s):  
Mi-Young Hahn ◽  
Sahadevan Raman ◽  
Mauricio Anaya ◽  
Robert N. Husson
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Stress Responses ◽  
Sigma Factor ◽  
Sigma Factors ◽  
Infection Model ◽  
Transcription Start Sites ◽  
Promoter Sequences ◽  
Extracytoplasmic Function Sigma Factor

ABSTRACT Mycobacterium tuberculosis sigL encodes an extracytoplasmic function (ECF) sigma factor and is adjacent to a gene for a membrane protein (Rv0736) that contains a conserved HXXXCXXC sequence. This motif is found in anti-sigma factors that regulate several ECF sigma factors, including those that control oxidative stress responses. In this work, SigL and Rv0736 were found to be cotranscribed, and the intracellular domain of Rv0736 was shown to interact specifically with SigL, suggesting that Rv0736 may encode an anti-sigma factor of SigL. An M. tuberculosis sigL mutant was not more susceptible than the parental strain to several oxidative and nitrosative stresses, and sigL expression was not increased in response to these stresses. In vivo, sigL is expressed from a weak SigL-independent promoter and also from a second SigL-dependent promoter. To identify SigL-regulated genes, sigL was overexpressed and microarray analysis of global transcription was performed. Four small operons, sigL (Rv0735)-Rv0736, mpt53 (Rv2878c)-Rv2877c, pks10 (Rv1660)-pks7 (Rv1661), and Rv1139c-Rv1138c, were among the most highly upregulated genes in the sigL-overexpressing strain. SigL-dependent transcription start sites of these operons were mapped, and the consensus promoter sequences TGAACC in the −35 region and CGTgtc in the −10 region were identified. In vitro, purified SigL specifically initiated transcription from the promoters of sigL, mpt53, and pks10. Additional genes, including four PE_PGRS genes, appear to be regulated indirectly by SigL. In an in vivo murine infection model, the sigL mutant strain showed marked attenuation, indicating that the sigL regulon is important in M. tuberculosis pathogenesis.

Further investigation of the mechanism of Vitreoscilla hemoglobin (VHb) protection from oxidative stress in Escherichia coli

Biologia ◽  
2011 ◽  
Vol 66 (5) ◽  
Author(s):  
Meltem Akbas ◽  
Tugrul Doruk ◽  
Serhat Ozdemir ◽  
Benjamin Stark
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Superoxide Dismutase ◽  
Stationary Phase ◽  
Exponential Phase ◽  
Vitreoscilla Hemoglobin ◽  
Sod Activity ◽  
E Coli ◽  
Hydrogen Peroxide Treatment

AbstractIn Escherichia coli, Vitreoscilla hemoglobin (VHb) protects against oxidative stress, perhaps, in part, by oxidizing OxyR. Here this protection, specifically VHb-associated effects on superoxide dismutase (SOD) and catalase levels, was examined. Exponential or stationary phase cultures of SOD+ or SOD− E. coli strains with or without VHb and oxyR antisense were treated with 2 mM hydrogen peroxide without sublethal peroxide induction, and compared to untreated control cultures. The hydrogen peroxide treatment was toxic to both SOD+ and SOD− cells, but much more to SOD− cells; expression of VHb in SOD+ strains enhanced this toxicity. In contrast, the presence of VHb was generally associated in the SOD+ background with a modest increase in SOD activity that was not greatly affected by oxyR antisense or peroxide treatment. In both SOD+ and SOD− backgrounds, VHb was associated with higher catalase activity both in the presence and absence of peroxide. Contrary to its stimulatory effects in stationary phase, in exponential phase oxyR antisense generally decreased VHb levels.

scholarly journals The genome-wide transcriptional response to varying RpoS levels inEscherichia coliK-12

2016 ◽  
Author(s):  
Garrett T. Wong ◽  
Richard P. Bonocora ◽  
Alicia N. Schep ◽  
Suzannah M. Beeler ◽  
Anna J. Lee Fong ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Stress Responses ◽  
Sigma Factor ◽  
Core Promoter ◽  
Transcriptional Response ◽  
Transcriptional Responses ◽  
Cellular Processes ◽  
Functional Classes ◽  
Sigma Factor Rpos

AbstractThe alternative sigma factor RpoS is a central regulator of a many stress responses inEscherichia coli.The level of functional RpoS differs depending on the stress. The effect of these differing concentrations of RpoS on global transcriptional responses remains unclear. We investigated the effect of RpoS concentration on the transcriptome during stationary phase in rich media. We show that 23% of genes in theE. coligenome are regulated by RpoS level, and we identify many RpoS-transcribed genes and promoters. We observe three distinct classes of response to RpoS by genes in the regulon: genes whose expression changes linearly with increasing RpoS level, genes whose expression changes dramatically with the production of only a little RpoS (“sensitive” genes), and genes whose expression changes very little with the production of a little RpoS (“insensitive”). We show that sequences outside the core promoter region determine whether a RpoS-regulated gene in sensitive or insensitive. Moreover, we show that sensitive and insensitive genes are enriched for specific functional classes, and that the sensitivity of a gene to RpoS corresponds to the timing of induction as cells enter stationary phase. Thus, promoter sensitivity to RpoS is a mechanism to coordinate specific cellular processes with growth phase, and may also contribute to the diversity of stress responses directed by RpoS.ImportanceThe sigma factor RpoS is a global regulator that controls the response to many stresses inEscherichia coli.Different stresses result in different levels of RpoS production, but the consequences of this variation are unknown. We describe how changing the level of RpoS does not influence all RpoS-regulated genes equally. The cause of this variation is likely the action of transcription factors that bind the promoters of the genes. We show that the sensitivity of a gene to RpoS levels explains the timing of expression as cells enter stationary phase, and that genes with different RpoS sensitivities are enriched for specific functional groups. Thus, promoter sensitivity to RpoS is a mechanism to coordinate specific cellular processes in response to stresses.

scholarly journals Genome-Wide Transcriptional Response to Varying RpoS Levels in Escherichia coli K-12

2017 ◽  
Vol 199 (7) ◽  
Author(s):  
Garrett T. Wong ◽  
Richard P. Bonocora ◽  
Alicia N. Schep ◽  
Suzannah M. Beeler ◽  
Anna J. Lee Fong ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Stress Responses ◽  
Sigma Factor ◽  
Core Promoter ◽  
Transcriptional Responses ◽  
Content Type ◽  
Cellular Processes ◽  
K 12 ◽  
Sigma Factor Rpos

ABSTRACT The alternative sigma factor RpoS is a central regulator of many stress responses in Escherichia coli. The level of functional RpoS differs depending on the stress. The effect of these differing concentrations of RpoS on global transcriptional responses remains unclear. We investigated the effect of RpoS concentration on the transcriptome during stationary phase in rich media. We found that 23% of genes in the E. coli genome are regulated by RpoS, and we identified many RpoS-transcribed genes and promoters. We observed three distinct classes of response to RpoS by genes in the regulon: genes whose expression changes linearly with increasing RpoS level, genes whose expression changes dramatically with the production of only a little RpoS (“sensitive” genes), and genes whose expression changes very little with the production of a little RpoS (“insensitive”). We show that sequences outside the core promoter region determine whether an RpoS-regulated gene is sensitive or insensitive. Moreover, we show that sensitive and insensitive genes are enriched for specific functional classes and that the sensitivity of a gene to RpoS corresponds to the timing of induction as cells enter stationary phase. Thus, promoter sensitivity to RpoS is a mechanism to coordinate specific cellular processes with growth phase and may also contribute to the diversity of stress responses directed by RpoS. IMPORTANCE The sigma factor RpoS is a global regulator that controls the response to many stresses in Escherichia coli. Different stresses result in different levels of RpoS production, but the consequences of this variation are unknown. We describe how changing the level of RpoS does not influence all RpoS-regulated genes equally. The cause of this variation is likely the action of transcription factors that bind the promoters of the genes. We show that the sensitivity of a gene to RpoS levels explains the timing of expression as cells enter stationary phase and that genes with different RpoS sensitivities are enriched for specific functional groups. Thus, promoter sensitivity to RpoS is a mechanism that coordinates specific cellular processes in response to stresses.

scholarly journals AlgU Controls Expression of Virulence Genes in Pseudomonas syringae pv. tomato DC3000

2016 ◽  
Vol 198 (17) ◽  
pp. 2330-2344 ◽  
Author(s):  
Eric Markel ◽  
Paul Stodghill ◽  
Zhongmeng Bao ◽  
Christopher R. Myers ◽  
Bryan Swingle
Keyword(s):  
Oxidative Stress ◽  
Pseudomonas Syringae ◽  
Stress Responses ◽  
Sigma Factor ◽  
Pathogenic Bacteria ◽  
Promoter Sequence ◽  
Tomato Dc3000 ◽  
Content Type ◽  
Plant Pathogenic Bacteria ◽  
And Oxidative Stress

ABSTRACTPlant-pathogenic bacteria are able to integrate information about their environment and adjust gene expression to provide adaptive functions. AlgU, an extracytoplasmic function (ECF) sigma factor encoded byPseudomonas syringae, controls expression of genes for alginate biosynthesis and genes involved with resisting osmotic and oxidative stress. AlgU is active while these bacteria are associated with plants, where its presence supports bacterial growth and disease symptoms. We found that AlgU is an important virulence factor forP. syringaepv. tomato DC3000 but that alginate production is dispensable for disease in host plants. This implies that AlgU regulates additional genes that facilitate bacterial pathogenesis. We used transcriptome sequencing (RNA-seq) to characterize the AlgU regulon and chromatin immunoprecipitation sequencing (ChIP-seq) to identify AlgU-regulated promoters associated with genes directly controlled by this sigma factor. We found that in addition to genes involved with alginate and osmotic and oxidative stress responses, AlgU regulates genes with known virulence functions, including components of the Hrp type III secretion system, virulence effectors, and thehrpLandhrpRStranscription regulators. These data suggest thatP. syringaepv. tomato DC3000 has adapted to use signals that activate AlgU to induce expression of important virulence functions that facilitate survival and disease in plants.IMPORTANCEPlant immune systems produce antimicrobial and bacteriostatic conditions in response to bacterial infection. Plant-pathogenic bacteria are adapted to suppress and/or tolerate these conditions; however, the mechanisms controlling these bacterial systems are largely uncharacterized. The work presented here provides a mechanistic explanation for howP. syringaepv. tomato DC3000 coordinates expression of multiple genetic systems, including those dedicated to pathogenicity, in response to environmental conditions. This work demonstrates the scope of AlgU regulation inP. syringaepv. tomato DC3000 and characterizes the promoter sequence regulated by AlgU in these bacteria.

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