scholarly journals σB Activation under Environmental and Energy Stress Conditions in Listeria monocytogenes

2006 ◽  
Vol 72 (8) ◽  
pp. 5197-5203 ◽  
Author(s):  
Soraya Chaturongakul ◽  
Kathryn J. Boor
Keyword(s):  
Listeria Monocytogenes ◽  
Cumene Hydroperoxide ◽  
Stress Conditions ◽  
Wild Type ◽  
Regulation Of Expression ◽  
Transcript Levels ◽  
Energy Stress ◽  
Expression Studies ◽  
Genes Encoding ◽  
Gene Expression Studies

ABSTRACT To measure σB activation in Listeria monocytogenes under environmental or energy stress conditions, quantitative reverse transcriptase PCR (TaqMan) was used to determine the levels of transcripts for the σB-dependent opuCA and clpC genes in strains having null mutations in genes encoding regulator of sigma B proteins (rsbT and rsbV) and sigma B (sigB) and in the L. monocytogenes wild-type 10403S strain under different stress conditions. The ΔsigB, ΔrsbT, and ΔrsbV strains previously exhibited increased hemolytic activities compared to the hemolytic activity of the wild-type strain; therefore, transcript levels for hly were also determined. RsbT, RsbV, and σB were all required for opuCA expression during growth under carbon-limiting conditions or following exposure to pH 4.5, salt, ethanol, or the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP). Expression of clpC was RsbT, RsbV, and σB dependent in the presence of CCCP but not under the other conditions. hly expression was not RsbT, RsbV, or σB dependent in the presence of either CCCP or salt. opuCA transcript levels did not increase in the presence of rapidly lethal stresses (i.e., pH 2.5 or 13 mM cumene hydroperoxide) despite the enhanced survival of the wild type compared with the survival of the mutant strains under these conditions. These findings highlight the importance of complementing phenotypic characterizations with gene expression studies to identify direct and indirect effects of null mutations in regulatory genes, such as sigB. Overall, our data show that while σB activation occurs through a single pathway under both environmental and energy stress conditions, regulation of expression of some stress response and virulence genes in the σB regulon (e.g., clpC) appears to require networks involving multiple transcriptional regulators.

scholarly journals RsbT and RsbV Contribute to σB-Dependent Survival under Environmental, Energy, and Intracellular Stress Conditions in Listeria monocytogenes

2004 ◽  
Vol 70 (9) ◽  
pp. 5349-5356 ◽  
Author(s):  
Soraya Chaturongakul ◽  
Kathryn J. Boor
Keyword(s):  
Tissue Culture ◽  
Listeria Monocytogenes ◽  
Cumene Hydroperoxide ◽  
Signal Transduction Pathway ◽  
Brain Heart Infusion ◽  
Mouse Fibroblast ◽  
Stress Conditions ◽  
Phenotypic Characterization ◽  
Energy Stress ◽  
Sigma B

ABSTRACT Sigma B (σB) is a stress-responsive alternative sigma factor that has been identified in various gram-positive bacteria. Seven different regulators of sigma B (Rsbs) are located in the sigB operons of both Bacillus subtilis and Listeria monocytogenes. In B. subtilis, these proteins contribute to regulation of σB activity by conveying environmental and energy stress signals through two well-established branches of a signal transduction pathway. RsbT contributes to regulation of σB activity in response to environmental stresses, while RsbV contributes to σB activation under both environmental and energy stresses in B. subtilis. To probe L. monocytogenes Rsb roles in σB-mediated responses to various stresses, in-frame deletions were created in rsbT and rsbV. Phenotypic characterization of the L. monocytogenes rsbT and rsbV null mutants revealed that both mutants were similar to the ΔsigB strain in their abilities to survive under environmental stress conditions (exposure to synthetic gastric fluid, pH 2.5, acidified brain heart infusion broth [BHI], or oxidative stress [13 mM cumene hydroperoxide]). Under energy stress conditions (carbon starvation in defined media, entry into stationary phase, or reduced intracellular ATP), both ΔrsbT and ΔrsbV showed survival reductions similar to that of the ΔsigB strain. These observations suggest that the pathways for Rsb-dependent regulation of σB activity differ between L. monocytogenes and B. subtilis. As σB also activates transcription of the L. monocytogenes prfAP2 promoter, we evaluated virulence-associated characteristics of ΔprfAP1rsbT and ΔprfAP1rsbV double mutants in hemolysis and tissue culture assays. Both double mutants showed identical phenotypes to ΔprfAP1P2 and ΔprfAP1sigB double mutants, i.e., reduced hemolysis activity and reduced plaque size in mouse fibroblast cells. These findings indicate that RsbT and RsbV both contribute to σB activation in L. monocytogenes during exposure to environmental and energy stresses as well as during tissue culture infection.

scholarly journals Microarray-Based Characterization of the Listeria monocytogenes Cold Regulon in Log- and Stationary-Phase Cells

2007 ◽  
Vol 73 (20) ◽  
pp. 6484-6498 ◽  
Author(s):  
Yvonne C. Chan ◽  
Sarita Raengpradub ◽  
Kathryn J. Boor ◽  
Martin Wiedmann
Keyword(s):  
Listeria Monocytogenes ◽  
Heat Shock ◽  
Stationary Phase ◽  
Response Regulator ◽  
Differentially Expressed ◽  
Cold Shock Protein ◽  
Rna Helicases ◽  
Transcript Levels ◽  
Number Of Genes ◽  
Genes Encoding

ABSTRACT Whole-genome microarray experiments were performed to define the Listeria monocytogenes cold growth regulon and to identify genes differentially expressed during growth at 4 and 37°C. Microarray analysis using a stringent cutoff (adjusted P < 0.001; ≥2.0-fold change) revealed 105 and 170 genes that showed higher transcript levels in logarithmic- and stationary-phase cells, respectively, at 4°C than in cells grown at 37°C. A total of 74 and 102 genes showed lower transcript levels in logarithmic- and stationary-phase cells, respectively, grown at 4°C. Genes with higher transcript levels at 4°C in both stationary- and log-phase cells included genes encoding a two-component response regulator (lmo0287), a cold shock protein (cspL), and two RNA helicases (lmo0866 and lmo1722), whereas a number of genes encoding virulence factors and heat shock proteins showed lower transcript levels at 4°C. Selected genes that showed higher transcript levels at 4°C during both stationary and log phases were confirmed by quantitative reverse transcriptase PCR. Our data show that (i) a large number of L. monocytogenes genes are differentially expressed at 4 and 37°C, with more genes showing higher transcript levels than lower transcript levels at 4°C, (ii) L. monocytogenes genes with higher transcript levels at 4°C include a number of genes and operons with previously reported or plausible roles in cold adaptation, and (iii) L. monocytogenes genes with lower transcript levels at 4°C include a number of virulence and virulence-associated genes as well as some heat shock genes.

The chinless mutation and neural crest cell interactions in zebrafish jaw development

Development ◽  
1996 ◽  
Vol 122 (5) ◽  
pp. 1417-1426 ◽  
Author(s):  
T.F. Schilling ◽  
C. Walker ◽  
C.B. Kimmel
Keyword(s):  
Neural Crest ◽  
Neural Crest Cell ◽  
Neural Crest Cells ◽  
Paraxial Mesoderm ◽  
Wild Type ◽  
Host Genotype ◽  
Pharyngeal Arches ◽  
Expression Studies ◽  
Gene Expression Studies ◽  
Cranial Neural Crest Cells

During vertebrate development, neural crest cells are thought to pattern many aspects of head organization, including the segmented skeleton and musculature of the jaw and gills. Here we describe mutations at the gene chinless, chn, that disrupt the skeletal fates of neural crest cells in the head of the zebrafish and their interactions with muscle precursors. chn mutants lack neural-crest-derived cartilage and mesoderm-derived muscles in all seven pharyngeal arches. Fate mapping and gene expression studies demonstrate the presence of both undifferentiated cartilage and muscle precursors in mutants. However, chn blocks differentiation directly in neural crest, and not in mesoderm, as revealed by mosaic analyses. Neural crest cells taken from wild-type donor embryos can form cartilage when transplanted into chn mutant hosts and rescue some of the patterning defects of mutant pharyngeal arches. In these cases, cartilage only forms if neural crest is transplanted at least one hour before its migration, suggesting that interactions occur transiently in early jaw precursors. In contrast, transplanted cells in paraxial mesoderm behave according to the host genotype; mutant cells form jaw muscles in a wild-type environment. These results suggest that chn is required for the development of pharyngeal cartilages from cranial neural crest cells and subsequent crest signals that pattern mesodermally derived myocytes.

scholarly journals Transcriptional activation of the Azotobacter vinelandii polyhydroxybutyrate biosynthetic genes phbBAC by PhbR and RpoS

Microbiology ◽  
2011 ◽  
Vol 157 (11) ◽  
pp. 3014-3023 ◽  
Author(s):  
Alberto Hernandez-Eligio ◽  
Mildred Castellanos ◽  
Soledad Moreno ◽  
Guadalupe Espín
Keyword(s):  
Stationary Phase ◽  
Transcriptional Activation ◽  
Azotobacter Vinelandii ◽  
Transcriptional Regulator ◽  
Gene Fusions ◽  
Wild Type ◽  
Rt Pcr ◽  
Regulation Of Expression ◽  
Expression Studies ◽  
Mutant Strains

We previously showed that in Azotobacter vinelandii, accumulation of polyhydroxybutyrate (PHB) occurs mainly during the stationary phase, and that a mutation in phbR, encoding a transcriptional regulator of the AraC family, reduces PHB accumulation. In this study, we characterized the roles of PhbR and RpoS, a central regulator during stationary phase in bacteria, in the regulation of expression of the PHB biosynthetic operon phbBAC and phbR. We showed that inactivation of rpoS reduced PHB accumulation, similar to the phbR mutation, and inactivation of both rpoS and phbR resulted in an inability to produce PHB. We carried out expression studies with the wild-type, and the rpoS, phbR and double rpoS-phbR mutant strains, using quantitative RT-PCR, as well as phbB : : gusA and phbR : : gusA gene fusions. These studies showed that both PhbR and RpoS act as activators of phbB and phbR, and revealed a role for PhbR as an autoactivator. We also demonstrated that PhbR binds specifically to two almost identical 18 bp sites, TGTCACCAA-N4-CACTA and TGTCACCAA-N4-CAGTA, present in the phbB promoter region. The activation of phbB and phbR transcription by RpoS reported here is in agreement with the observation that accumulation of PHB in A. vinelandii occurs mainly during the stationary phase.

scholarly journals Comparative Analysis of the σB-Dependent Stress Responses in Listeria monocytogenes and Listeria innocua Strains Exposed to Selected Stress Conditions

2007 ◽  
Vol 74 (1) ◽  
pp. 158-171 ◽  
Author(s):  
Sarita Raengpradub ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Response ◽  
Stationary Phase ◽  
Stress Responses ◽  
Bacterial Species ◽  
Acid Stress ◽  
Listeria Innocua ◽  
Transcript Levels ◽  
Genes Encoding ◽  
Flagellar Proteins

ABSTRACT The alternative sigma factor σB contributes to transcription of stress response and virulence genes in diverse gram-positive bacterial species. The composition and functions of the Listeria monocytogenes and Listeria innocua σB regulons were hypothesized to differ due to virulence differences between these closely related species. Transcript levels in stationary-phase cells and in cells exposed to salt stress were characterized by microarray analyses for both species. In L. monocytogenes, 168 genes were positively regulated by σB; 145 of these genes were preceded by a putative σB consensus promoter. In L. innocua, 64 genes were positively regulated by σB. σB contributed to acid stress survival in log-phase cells for both species but to survival in stationary-phase cells only for L. monocytogenes. In summary, (i) the L. monocytogenes σB regulon includes >140 genes that are both directly and positively regulated by σB, including genes encoding proteins with importance in stress response, virulence, transcriptional regulation, carbohydrate metabolism, and transport; (ii) a number of L. monocytogenes genes encoding flagellar proteins show higher transcript levels in the ΔsigB mutant, and both L. monocytogenes and L. innocua ΔsigB null mutants have increased motility compared to the respective isogenic parent strains, suggesting that σB affects motility and chemotaxis; and (iii) although L. monocytogenes and L. innocua differ in σB-dependent acid stress resistance and have species-specific σB-dependent genes, the L. monocytogenes and L. innocua σB regulons show considerable conservation, with a common set of at least 49 genes that are σB dependent in both species.

scholarly journals MmpS5-MmpL5 Transporters Provide Mycobacterium smegmatis Resistance to imidazo[1,2-b][1,2,4,5]tetrazines

Pathogens ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 166 ◽  
Author(s):  
Dmitry A. Maslov ◽  
Kirill V. Shur ◽  
Aleksey A. Vatlin ◽  
Valery N. Danilenko
Keyword(s):  
Gene Expression ◽  
Mycobacterium Smegmatis ◽  
Drug Resistant ◽  
Wild Type ◽  
Efflux System ◽  
Mechanisms Of Resistance ◽  
Expression Studies ◽  
Gene Expression Studies ◽  
Mutant Genes

The emergence and spread of drug-resistant Mycobacterium tuberculosis strains (including MDR, XDR, and TDR) force scientists worldwide to search for new anti-tuberculosis drugs. We have previously reported a number of imidazo[1,2-b][1,2,4,5]tetrazines – putative inhibitors of mycobacterial eukaryotic-type serine-threonine protein-kinases, active against M. tuberculosis. Whole genomic sequences of spontaneous drug-resistant M. smegmatis mutants revealed four genes possibly involved in imidazo[1,2-b][1,2,4,5]tetrazines resistance; however, the exact mechanism of resistance remain unknown. We used different approaches (construction of targeted mutants, overexpression of the wild-type (w.t.) and mutant genes, and gene-expression studies) to assess the role of the previously identified mutations. We show that mutations in MSMEG_1380 gene lead to overexpression of the mmpS5-mmpL5 operon in M. smegmatis, thus providing resistance to imidazo[1,2-b][1,2,4,5]tetrazines by increased efflux through the MmpS5-MmpL5 system, similarly to the mechanisms of resistance described for M. tuberculosis and M. abscessus. Mycobacterial MmpS5-MmpL5 transporters should be considered as an MDR-efflux system and they should be taken into account at early stages of anti-tuberculosis drug development.

scholarly journals Arabidopsis ERF4 and MYB52 Transcription Factors Play Antagonistic Roles in Regulating Homogalacturonan De-methylesterification in Seed Coat Mucilage

2020 ◽  
Author(s):  
Anming Ding ◽  
Xianfeng Tang ◽  
Linhe Han ◽  
Jianlu Sun ◽  
Angyan Ren ◽  
...  
Keyword(s):  
Cell Wall ◽  
Transcription Factors ◽  
Seed Coat ◽  
Pectin Methylesterase ◽  
Wild Type ◽  
Expression Studies ◽  
Gene Expression Studies ◽  
Transcriptional Complex ◽  
Seed Coat Mucilage ◽  
Seed Mucilage

ABSTRACTThe Arabidopsis (Arabidopsis thaliana) seed coat mucilage is a specialized cell wall with pectin as its major component. Pectin is synthesized in the Golgi apparatus with homogalacturonan fully methylesterified, but it must undergo de-methylesterification by pectin methylesterase (PME) after being secreted into the cell wall. This reaction is critical for pectin maturation, but the mechanisms of its transcriptional regulation remain largely unknown. Here, we show that the Arabidopsis ERF4 transcription factor positively regulates pectin de-methylesterification during seed development and directly suppresses the expression of PME INHIBITOR13 (PMEI13), 14, 15 and SUBTILISIN-LIKE SERINE PROTEASE 1.7 (SBT1.7). The erf4 mutant seeds showed repartitioning of mucilage between soluble and adherent layers as a result of decreased PME activity and increased degree of pectin methylesterification. ERF4 physically associates with and antagonizes MYB52 in activating PMEI6, 14 and SBT1.7 and MYB52 also antagonizes ERF4 activity in the regulation of downstream targets. Gene expression studies revealed that ERF4 and MYB52 have opposite effects on pectin de-methylesterification. Genetic analysis indicated that the erf4-2 myb52 double mutant seeds show mucilage phenotype similar to wild-type. Taken together, this study demonstrates that ERF4 and MYB52 antagonize each other’s activity to maintain the appropriate degree of pectin methylesterification, expanding our understanding of how pectin de-methylesterification is fine-tuned by the ERF4-MYB52 transcriptional complex in the seed mucilage.One-sentence summaryArabidopsis ERF4 and MYB52 transcription factors interact and play antagonistic roles in regulating homogalacturonan de-methylesterification related genes in the seed coat mucilage.

scholarly journals Comparative Analysis of Listeria monocytogenes Plasmids and Expression Levels of Plasmid-Encoded Genes during Growth under Salt and Acid Stress Conditions

Toxins ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 426 ◽  
Author(s):  
Patricia Hingston ◽  
Thomas Brenner ◽  
Lisbeth Truelstrup Hansen ◽  
Siyun Wang
Keyword(s):  
Listeria Monocytogenes ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Stress Conditions ◽  
Chaperone Protein ◽  
Nadh Peroxidase ◽  
Genes Encoding ◽  
Fold Induction ◽  
N 93 ◽  
Unique Plasmid

Listeria monocytogenes strains are known to harbour plasmids that confer resistance to sanitizers, heavy metals, and antibiotics; however, very little research has been conducted into how plasmids may influence L. monocytogenes’ ability to tolerate food-related stresses. To investigate this, a library (n = 93) of L. monocytogenes plasmid sequences were compared. Plasmid sequences were divided into two groups (G1 and G2) based on a repA phylogeny. Twenty-six unique plasmid types were observed, with 13 belonging to each of the two repA-based groups. G1 plasmids were significantly (p < 0.05) smaller than G2 plasmids but contained a larger diversity of genes. The most prevalent G1 plasmid (57,083 bp) was observed in 26 strains from both Switzerland and Canada and a variety of serotypes. Quantitative PCR (qPCR) revealed a >2-fold induction of plasmid-contained genes encoding an NADH peroxidase, cadmium ATPase, multicopper oxidase, and a ClpL chaperone protein during growth under salt (6% NaCl) and acid conditions (pH 5) and ProW, an osmolyte transporter, under salt stress conditions. No differences in salt and acid tolerance were observed between plasmid-cured and wildtype strains. This work highlights the abundance of specific plasmid types among food-related L. monocytogenes strains, the unique characteristics of G1 and G2 plasmids, and the possible contributions of plasmids to L. monocytogenes tolerance to food-related stresses.

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