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 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.

scholarly journals Contributions of Listeria monocytogenes σ B and PrfA to expression of virulence and stress response genes during extra- and intracellular growth

Microbiology ◽  
2006 ◽  
Vol 152 (6) ◽  
pp. 1827-1838 ◽  
Author(s):  
Mark J. Kazmierczak ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Response ◽  
Stationary Phase ◽  
Virulence Gene ◽  
Exponential Phase ◽  
Promoter Regions ◽  
Transcript Levels ◽  
Virulence Gene Expression ◽  
Qrt Pcr ◽  
Relative Contribution

Listeria monocytogenes σ B and PrfA are pleiotropic regulators of stress response and virulence gene expression. Quantitative RT-PCR (qRT-PCR) was used to measure transcript levels of σ B- and PrfA-dependent genes in exponential-phase L. monocytogenes wild-type and ΔsigB strains as well as in bacteria exposed to environmental stresses (0.3 M NaCl or growth to stationary phase) or present in the vacuole or cytosol of human intestinal epithelial cells. Stationary-phase or NaCl-exposed L. monocytogenes showed σ B-dependent increases in opuCA (10- and 17-fold higher, respectively) and gadA transcript levels (77- and 14-fold higher, respectively) as compared to non-stressed, exponential-phase bacteria. While PrfA activity, as reflected by plcA transcript levels, was up to 95-fold higher in intracellular L. monocytogenes as compared to non-stressed bacteria, σ B activity was only slightly higher in intracellular than in non-stressed bacteria. Increased plcA transcript levels, which were similar in both host cell vacuole and cytosol, were associated with increases in both prfA expression and PrfA activity. qRT-PCR assays were designed to measure expression of prfA from each of its three promoter regions. Under all conditions, readthrough transcription from the upstream plcA promoter was very low. The relative contribution to total prfA transcription from the σ A-dependent P1prfA promoter ranged from ∼17 % to 30 %, while the contribution of the P2prfA region, which appears to be transcribed by both σ A and σ B, ranged from ∼70 % to 82 % of total prfA transcript levels. In summary (i) σ B is primarily activated during environmental stress and does not contribute to PrfA activation in intracellular L. monocytogenes and (ii) the partially σ B-dependent P2prfA promoter region contributes the majority of prfA transcripts in both intra- and extracellular bacteria.

Comparison of the Stress Response of Listeria monocytogenes Strains with Sprout Colonization

2008 ◽  
Vol 71 (8) ◽  
pp. 1556-1562 ◽  
Author(s):  
LISA GORSKI ◽  
DENISE FLAHERTY ◽  
JESSICA M. DUHÉ
Keyword(s):  
Oxidative Stress ◽  
Statistical Analysis ◽  
Listeria Monocytogenes ◽  
Stress Response ◽  
Foodborne Pathogen ◽  
Acid Stress ◽  
Broccoli Sprouts ◽  
Alfalfa Sprouts ◽  
Different Strains ◽  
And Oxidative Stress

Twenty-nine strains of the foodborne pathogen Listeria monocytogenes were tested for their ability to colonize alfalfa, radish, and broccoli sprouts and their capacity to withstand acid and oxidative stress, two stresses common to the sprouting environment. Wide variation in the ability of different strains to colonize alfalfa sprouts were confirmed, but the variations among radish and broccoli sprouts were not as large. With a few exceptions, strains that were poor colonizers of alfalfa tended to be among the poorer colonizers of radish and broccoli and vice versa. The strains also were variable in their resistance to both acid and oxidative stress. Statistical analysis revealed no correlation between acid stress and sprout colonization, but there was a positive correlation between resistance to oxidative stress and colonization of all three sprout types. Although the response to oxidative stress is important for L. monocytogenes virulence, it also may be important for life outside of a host.

Acid Stress Responses in Listeria monocytogenes

2008 ◽  
pp. 67-91 ◽  
Author(s):  
Sheila Ryan ◽  
Colin Hill ◽  
Cormac G.M. Gahan
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Responses ◽  
Acid Stress

Inhibition of Listeria in Buffer, Broth, and Milk by Enterocin 1146, a Bacteriocin Produced by Enterococcus faecium

1992 ◽  
Vol 55 (7) ◽  
pp. 503-508 ◽  
Author(s):  
EUGENIO PARENTE ◽  
COLIN HILL
Keyword(s):  
Listeria Monocytogenes ◽  
Stationary Phase ◽  
Enterococcus Faecium ◽  
Bactericidal Effect ◽  
Listeria Innocua ◽  
Lag Phase ◽  
Inoculum Level ◽  
Slow Decrease ◽  
Logarithmic Relationship

Enterocin 1146, a bacteriocin produced by Enterococcus faecium. DPC1146, has a rapid bactericidal effect on Listeria in buffer systems, broth, and milk. In trypticase soy broth, increasing the bacteriocin dose and/or decreasing the pH extended the lag phase of Listeria innocua. A logarithmic relationship was found between response (as proportion of survivors or growth compared to a control) and dose. Increasing the inoculum level of the indicator reduced the effectiveness of enterocin 1146. Log-phase cells of L. innocua were more resistant than stationary-phase cells in both broth and buffer systems. In milk treated with 250 arbitrary units of enterocin 1146/ml and inoculated with 103 or 105 CFU/ml of Listeria monocytogenes Scott A, populations reached only 5–14% of the control after 24 h at 30°C, with numbers exceeding 107, while at 6°C a slow decrease in population was found.

scholarly journals Phenotypic and Transcriptomic Analyses Demonstrate Interactions between the Transcriptional Regulators CtsR and Sigma B in Listeria monocytogenes

2007 ◽  
Vol 73 (24) ◽  
pp. 7967-7980 ◽  
Author(s):  
Yuewei Hu ◽  
Sarita Raengpradub ◽  
Ute Schwab ◽  
Chris Loss ◽  
Renato H. Orsi ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Response ◽  
Heat Resistance ◽  
Parent Strain ◽  
Inducible Promoter ◽  
Heat Sensitivity ◽  
Intestinal Epithelial ◽  
Class Iii ◽  
Stress Response Genes ◽  
Genes Encoding

ABSTRACT Listeria monocytogenes σB positively regulates the transcription of class II stress response genes; CtsR negatively regulates class III stress response genes. To identify interactions between these two stress response systems, we constructed L. monocytogenes ΔctsR and ΔctsR ΔsigB strains, as well as a ΔctsR strain expressing ctsR in trans under the control of an IPTG (isopropyl-β-d-thiogalactopyranoside)-inducible promoter. These strains, along with a parent and a ΔsigB strain, were assayed for motility, heat resistance, and invasion of human intestinal epithelial cells, as well as by whole-genome transcriptomic and quantitative real-time PCR analyses. Both ΔctsR and ΔctsR ΔsigB strains had significantly higher thermotolerances than the parent strain; however, full heat sensitivity was restored to the ΔctsR strain when ctsR was expressed in trans. Although log-phase ΔctsR was not reduced in its ability to infect human intestinal cells, the ΔctsR ΔsigB strain showed significantly lower invasion efficiency than either the parent strain or the ΔsigB strain, indicating that interactions between CtsR and σB contribute to invasiveness. Statistical analyses also confirmed interactions between the ctsR and the sigB null mutations in both heat resistance and invasion phenotypes. Microarray transcriptomic analyses and promoter searches identified (i) 42 CtsR-repressed genes, (ii) 22 genes with lower transcript levels in the ΔctsR strain, and (iii) at least 40 genes coregulated by both CtsR and σB, including genes encoding proteins with confirmed or plausible roles in virulence and stress response. Our data demonstrate that interactions between CtsR and σB play an important role in L. monocytogenes stress resistance and virulence.

scholarly journals Transcriptomic Analysis of Listeria monocytogenes in Response to Bile Under Aerobic and Anaerobic Conditions

2021 ◽  
Vol 12 ◽  
Author(s):  
Damayanti Chakravarty ◽  
Gyan Sahukhal ◽  
Mark Arick ◽  
Morgan L. Davis ◽  
Janet R. Donaldson
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Responses ◽  
Listeriolysin O ◽  
Gi Tract ◽  
Anaerobic Conditions ◽  
Transcript Levels ◽  
Comprehensive Information ◽  
Associated Proteins ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

Listeria monocytogenes is a gram-positive facultative anaerobic bacterium that causes the foodborne illness listeriosis. The pathogenesis of this bacterium depends on its survival in anaerobic, acidic, and bile conditions encountered throughout the gastrointestinal (GI) tract. This transcriptomics study was conducted to analyze the differences in transcript levels produced under conditions mimicking the GI tract. Changes in transcript levels were analyzed using RNA isolated from L. monocytogenes strain F2365 at both aerobic and anaerobic conditions, upon exposure to 0 and 1% bile at acidic and neutral pH. Transcripts corresponding to genes responsible for pathogenesis, cell wall associated proteins, DNA repair, transcription factors, and stress responses had variations in levels under the conditions tested. Upon exposure to anaerobiosis in acidic conditions, there were variations in the transcript levels for the virulence factors internalins, listeriolysin O, etc., as well as many histidine sensory kinases. These data indicate that the response to anaerobiosis differentially influences the transcription of several genes related to the survival of L. monocytogenes under acidic and bile conditions. Though further research is needed to decipher the role of oxygen in pathogenesis of L. monocytogenes, these data provide comprehensive information on how this pathogen responds to the GI tract.

σ B-dependent gene induction and expression in Listeria monocytogenes during osmotic and acid stress conditions simulating the intestinal environment

Microbiology ◽  
2004 ◽  
Vol 150 (11) ◽  
pp. 3843-3855 ◽  
Author(s):  
David Sue ◽  
Daniel Fink ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Response ◽  
Virulence Genes ◽  
Acid Stress ◽  
Exponential Phase ◽  
Wild Type ◽  
Transcript Accumulation ◽  
Gastrointestinal Infections ◽  
Stress Response Genes ◽  
Foodborne Infections

Listeria monocytogenes must overcome a variety of stress conditions in the host digestive tract to cause foodborne infections. The alternative sigma factor σ B, encoded by sigB, is responsible for regulating transcription of several L. monocytogenes virulence and stress-response genes, including genes that contribute to establishment of gastrointestinal infections. A quantitative RT-PCR assay was used to measure mRNA transcript accumulation for the virulence genes inlA and bsh, the stress-response genes opuCA and lmo0669 (encoding a carnitine transporter and an oxidoreductase, respectively) and the housekeeping gene rpoB. Assays were conducted on mid-exponential phase L. monocytogenes cells exposed to conditions reflecting osmotic (0·3 M NaCl) or acid (pH 4·5) conditions typical for the human intestinal lumen. In exponential-phase cells, as well as under osmotic and acid stress, inlA, opuCA and bsh showed significantly lower absolute expression levels in a L. monocytogenes ΔsigB null mutant compared to wild-type. A statistical model that normalized target gene expression relative to rpoB showed that accumulation of inlA, opuCA and bsh transcripts was significantly increased in the wild-type strain within 5 min of acid and osmotic stress exposure; lmo0669 transcript accumulation increased significantly only after acid exposure. It was concluded that σ B is essential for rapid induction of the tested stress-response and virulence genes under conditions typically encountered during gastrointestinal passage. As inlA, bsh and opuCA are critical for gastrointestinal infections in animal models, the data also suggest that σ B contributes to the ability of L. monocytogenes to cause foodborne infections.

scholarly journals DksA and ppGpp Regulate the σS Stress Response by Activating Promoters for the Small RNA DsrA and the Anti-Adapter Protein IraP

2017 ◽  
Vol 200 (2) ◽  
Author(s):  
Mary E. Girard ◽  
Saumya Gopalkrishnan ◽  
Elicia D. Grace ◽  
Jennifer A. Halliday ◽  
Richard L. Gourse ◽  
...  
Keyword(s):  
Stress Response ◽  
Rna Polymerase ◽  
Stationary Phase ◽  
Sigma Factor ◽  
Bacterial Species ◽  
Adaptor Protein ◽  
Large Family ◽  
Alternative Sigma Factor ◽  
Term Survival ◽  
Content Type

ABSTRACT σS is an alternative sigma factor, encoded by the rpoS gene, that redirects cellular transcription to a large family of genes in response to stressful environmental signals. This so-called σS general stress response is necessary for survival in many bacterial species and is controlled by a complex, multifactorial pathway that regulates σS levels transcriptionally, translationally, and posttranslationally in Escherichia coli. It was shown previously that the transcription factor DksA and its cofactor, ppGpp, are among the many factors governing σS synthesis, thus playing an important role in activation of the σS stress response. However, the mechanisms responsible for the effects of DksA and ppGpp have not been elucidated fully. We describe here how DksA and ppGpp directly activate the promoters for the anti-adaptor protein IraP and the small regulatory RNA DsrA, thereby indirectly influencing σS levels. In addition, based on effects of DksAN88I, a previously identified DksA variant with increased affinity for RNA polymerase (RNAP), we show that DksA can increase σS activity by another indirect mechanism. We propose that by reducing rRNA transcription, DksA and ppGpp increase the availability of core RNAP for binding to σS and also increase transcription from other promoters, including PdsrA and PiraP. By improving the translation and stabilization of σS, as well as the ability of other promoters to compete for RNAP, DksA and ppGpp contribute to the switch in the transcription program needed for stress adaptation. IMPORTANCE Bacteria spend relatively little time in log phase outside the optimized environment found in a laboratory. They have evolved to make the most of alternating feast and famine conditions by seamlessly transitioning between rapid growth and stationary phase, a lower metabolic mode that is crucial for long-term survival. One of the key regulators of the switch in gene expression that characterizes stationary phase is the alternative sigma factor σS. Understanding the factors governing σS activity is central to unraveling the complexities of growth, adaptation to stress, and pathogenesis. Here, we describe three mechanisms by which the RNA polymerase binding factor DksA and the second messenger ppGpp regulate σS levels.

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