scholarly journals CsrRS Regulates Group B Streptococcus Virulence Gene Expression in Response to Environmental pH: a New Perspective on Vaccine Development

2009 ◽  
Vol 191 (17) ◽  
pp. 5387-5397 ◽  
Author(s):  
Isabella Santi ◽  
Renata Grifantini ◽  
Sheng-Mei Jiang ◽  
Cecilia Brettoni ◽  
Guido Grandi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Virulence Factors ◽  
Vaccine Development ◽  
Ph Regulation ◽  
Protective Efficacy ◽  
Virulence Gene ◽  
Ph Sensing ◽  
Group B Streptococci ◽  
Virulence Gene Expression ◽  
Group B

ABSTRACT To identify factors involved in the response of group B streptococci (GBS) to environmental pH, we performed a comparative global gene expression analysis of GBS at acidic and neutral pHs. We found that the transcription of 317 genes was increased at pH 5.5 relative to that at pH 7.0, while 61 genes were downregulated. The global response to acid stress included the differential expression of genes involved in transport, metabolism, stress response, and virulence. Known vaccine candidates, such as BibA and pilus components, were also regulated by pH. We observed that many of the genes involved in the GBS response to pH are known to be controlled by the CsrRS two-component system. Comparison of the regulon of wild-type strain 2603 V/R with that of a csrRS deletion mutant strain revealed that the pH-dependent regulation of 90% of the downregulated genes and 59.3% of the up-regulated genes in strain 2603 V/R was CsrRS dependent and that many virulence factors were overexpressed at high pH. Beta-hemolysin regulation was abrogated by selective inactivation of csrS, suggesting the implication of the CsrS protein in pH sensing. These results imply that the translocation of GBS from the acidic milieu of the vagina to the neutral pH of the neonatal lung signals the up-regulation of GBS virulence factors and conversion from a colonizing to an invasive phenotype. In addition, the fact that increased exposure of BibA on the bacterial surface at pH 7.0 induced opsonophagocytic killing of GBS in immune serum highlights the importance of pH regulation in the protective efficacy of specific antibodies to surface-exposed GBS proteins.

scholarly journals Nutritional Regulation of the Sae Two-Component System by CodY inStaphylococcus aureus

2018 ◽  
Vol 200 (8) ◽  
Author(s):  
Kevin D. Mlynek ◽  
William E. Sause ◽  
Derek E. Moormeier ◽  
Marat R. Sadykov ◽  
Kurt R. Hill ◽  
...  
Keyword(s):  
Gene Expression ◽  
Virulence Factors ◽  
Virulence Gene ◽  
Nutrient Depletion ◽  
Global Regulator ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Two Component

ABSTRACTStaphylococcus aureussubverts innate defenses during infection in part by killing host immune cells to exacerbate disease. This human pathogen intercepts host cues and activates a transcriptional response via theS. aureusexoprotein expression (SaeR/SaeS [SaeR/S]) two-component system to secrete virulence factors critical for pathogenesis. We recently showed that the transcriptional repressor CodY adjusts nuclease (nuc) gene expression via SaeR/S, but the mechanism remained unknown. Here, we identified two CodY binding motifs upstream of thesaeP1 promoter, which suggested direct regulation by this global regulator. We show that CodY shares a binding site with the positive activator SaeR and that alleviating direct CodY repression at this site is sufficient to abrogate stochastic expression, suggesting that CodY repressessaeexpression by blocking SaeR binding. Epistasis experiments support a model that CodY also controlssaeindirectly through Agr and Rot-mediated repression of thesaeP1 promoter. We also demonstrate that CodY repression ofsaerestrains production of secreted cytotoxins that kill human neutrophils. We conclude that CodY plays a previously unrecognized role in controlling virulence gene expression via SaeR/S and suggest a mechanism by which CodY acts as a master regulator of pathogenesis by tying nutrient availability to virulence gene expression.IMPORTANCEBacterial mechanisms that mediate the switch from a commensal to pathogenic lifestyle are among the biggest unanswered questions in infectious disease research. Since the expression of most virulence genes is often correlated with nutrient depletion, this implies that virulence is a response to the lack of nourishment in host tissues and that pathogens likeS. aureusproduce virulence factors in order to gain access to nutrients in the host. Here, we show that specific nutrient depletion signals appear to be funneled to the SaeR/S system through the global regulator CodY. Our findings reveal a strategy by whichS. aureusdelays the production of immune evasion and immune-cell-killing proteins until key nutrients are depleted.

scholarly journals Role of the Histone-Like Nucleoid Structuring Protein in Colonization, Motility, and Bile-Dependent Repression of Virulence Gene Expression in Vibrio cholerae

2006 ◽  
Vol 74 (5) ◽  
pp. 3060-3064 ◽  
Author(s):  
Amalendu Ghosh ◽  
Kalidas Paul ◽  
Rukhsana Chowdhury
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Factors ◽  
Virulence Gene ◽  
Virulence Gene Expression

ABSTRACT Bile-mediated repression of virulence gene expression is relieved in a Vibrio cholerae hns mutant. The mutant also exhibited reduced motility due to lower flrA expression, higher in vivo production of the virulence factors, and lower colonization efficiency. The colonization defect of the mutant was due to low FlrA production.

scholarly journals The Abi-domain Protein Abx1 Interacts with the CovS Histidine Kinase to Control Virulence Gene Expression in Group B Streptococcus

2013 ◽  
Vol 9 (2) ◽  
pp. e1003179 ◽  
Author(s):  
Arnaud Firon ◽  
Asmaa Tazi ◽  
Violette Da Cunha ◽  
Sophie Brinster ◽  
Elisabeth Sauvage ◽  
...  
Keyword(s):  
Gene Expression ◽  
Histidine Kinase ◽  
Group B Streptococcus ◽  
Virulence Gene ◽  
Virulence Gene Expression ◽  
Domain Protein ◽  
Group B

scholarly journals Modulation of Expression of the ToxR Regulon in Vibrio cholerae by a Member of the Two-Component Family of Response Regulators

1998 ◽  
Vol 66 (12) ◽  
pp. 5854-5861 ◽  
Author(s):  
Sandy M. Wong ◽  
Patricia A. Carroll ◽  
Laurence G. Rahme ◽  
Frederick M. Ausubel ◽  
Stephen B. Calderwood
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Factors ◽  
Bacterial Species ◽  
Virulence Gene ◽  
Response Regulators ◽  
Key Factors ◽  
Virulence Gene Expression ◽  
The Family ◽  
Two Component

ABSTRACT The ToxRS system in Vibrio cholerae plays a central role in the modulation of virulence gene expression in response to environmental stimuli. An integration of multiple signalling inputs mediated by ToxR, -S, and -T controls virulence gene expression leading to cholera toxin (CT) production. Recently, we identified a new virulence locus, varA (virulence associated regulator), in classical V. cholerae O1 that positively controls transcription of tcpA, the major subunit of the toxin-coregulated pilus (TCP) and the production of CT, two key factors in cholera pathogenesis. The varA locus is a homolog ofgacA (originally described for the soil organismPseudomonas fluorescens), which encodes a conserved global regulator belonging to the family of two-component signal transducing molecules. GacA homologs in a number of diverse gram-negative pathogenic bacterial species have been implicated in controlling the production of diverse virulence factors.varA mutants showed reduced levels of tcpAmessage and TcpA protein, lacked visible signs of autoagglutination (a phenotype associated with functional TCP), produced decreased levels of CT, and were attenuated in colonizing infant mice. Transcription ofvarA appears to be independent of ToxR, and overexpression of the regulators tcpPH and toxT from plasmids in the varA mutant restored wild-type levels of CT production and the ability to autoagglutinate. varArepresents an additional modulating factor in the coordinate expression of virulence factors in V. cholerae.

scholarly journals NAD+ pool depletion as a signal for the Rex regulon involved in Streptococcus agalactiae virulence

2021 ◽  
Vol 17 (8) ◽  
pp. e1009791
Author(s):  
Thierry Franza ◽  
Annika Rogstam ◽  
Saravanamuthu Thiyagarajan ◽  
Matthew J. Sullivan ◽  
Aurelie Derré-Bobillot ◽  
...  
Keyword(s):  
Gene Expression ◽  
Streptococcus Agalactiae ◽  
Group B Streptococcus ◽  
Virulence Gene ◽  
Opportunistic Pathogen ◽  
Virulence Gene Expression ◽  
Gram Positive Bacteria ◽  
Virulence Factor Gene ◽  
Group B

In many Gram-positive bacteria, the redox-sensing transcriptional repressor Rex controls central carbon and energy metabolism by sensing the intra cellular balance between the reduced and oxidized forms of nicotinamide adenine dinucleotide; the NADH/NAD+ ratio. Here, we report high-resolution crystal structures and characterization of a Rex ortholog (Gbs1167) in the opportunistic pathogen, Streptococcus agalactiae, also known as group B streptococcus (GBS). We present structures of Rex bound to NAD+ and to a DNA operator which are the first structures of a Rex-family member from a pathogenic bacterium. The structures reveal the molecular basis of DNA binding and the conformation alterations between the free NAD+ complex and DNA-bound form of Rex. Transcriptomic analysis revealed that GBS Rex controls not only central metabolism, but also expression of the monocistronic rex gene as well as virulence gene expression. Rex enhances GBS virulence after disseminated infection in mice. Mechanistically, NAD+ stabilizes Rex as a repressor in the absence of NADH. However, GBS Rex is unique compared to Rex regulators previously characterized because of its sensing mechanism: we show that it primarily responds to NAD+ levels (or growth rate) rather than to the NADH/NAD+ ratio. These results indicate that Rex plays a key role in GBS pathogenicity by modulating virulence factor gene expression and carbon metabolism to harvest nutrients from the host.

scholarly journals Association and Virulence Gene Expression Vary among Serotype III Group B Streptococcus Isolates following Exposure to Decidual and Lung Epithelial Cells

2014 ◽  
Vol 82 (11) ◽  
pp. 4587-4595 ◽  
Author(s):  
Michelle L. Korir ◽  
David Knupp ◽  
Kathryn LeMerise ◽  
Erica Boldenow ◽  
Rita Loch-Caruso ◽  
...  
Keyword(s):  
Gene Expression ◽  
Epithelial Cells ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Lung Epithelial Cells ◽  
Host Cells ◽  
Virulence Gene Expression ◽  
Decidual Cells ◽  
Lung Epithelial ◽  
Group B

ABSTRACTGroup BStreptococcus(GBS) causes severe disease in neonates, the elderly, and immunocompromised individuals. GBS species are highly diverse and can be classified by serotype and multilocus sequence typing. Sequence type 17 (ST-17) strains cause invasive neonatal disease more frequently than strains of other STs. Attachment and invasion of host cells are key steps in GBS pathogenesis. We investigated whether four serotype III strains representing ST-17 (two strains), ST-19, and ST-23 differ in their abilities to attach to and invade both decidual cells and lung epithelial cells. Virulence gene expression following host cell association and exposure to amnion cells was also tested. The ST-17 strains differed in their abilities to attach to and invade decidual cells, whereas there were no differences with lung epithelial cells. The ST-19 and ST-23 strains, however, attached to and invaded decidual cells less than both ST-17 strains. Although the ST-23 strain attached to lung epithelial cells better than ST-17 and -19 strains, none of the strains effectively invaded the lung epithelial cells. Notably, the association with host cells resulted in the differential expression of several virulence genes relative to basal expression levels. Similar expression patterns of some genes were observed regardless of cell type used. Collectively, these results show that GBS strains differ in their abilities to attach to distinct host cell types and express key virulence genes that are relevant to the disease process. Enhancing our understanding of pathogenic mechanisms could aid in the identification of novel therapeutic targets or vaccine candidates that could potentially decrease morbidity and mortality associated with neonatal infections.

scholarly journals Inhibition of Rho Activity Increases Expression of SaeRS-Dependent Virulence Factor Genes inStaphylococcus aureus, Showing a Link between Transcription Termination, Antibiotic Action, and Virulence

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Anna Nagel ◽  
Stephan Michalik ◽  
Michel Debarbouille ◽  
Tobias Hertlein ◽  
Manuela Gesell Salazar ◽  
...  
Keyword(s):  
Gene Expression ◽  
Staphylococcus Aureus ◽  
Virulence Factors ◽  
Transcription Termination ◽  
Virulence Gene ◽  
Antisense Transcription ◽  
Termination Factor ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Transcription Termination Factor

ABSTRACTStaphylococcus aureuscauses various diseases ranging from skin and soft tissue infections to life-threatening infections. Adaptation to the different host niches is controlled by a complex network of transcriptional regulators. Global profiling of condition-dependent transcription revealed adaptation ofS. aureusHG001 at the levels of transcription initiation and termination. In particular, deletion of the gene encoding the Rho transcription termination factor triggered a remarkable overall increase in antisense transcription and gene expression changes attributable to indirect regulatory effects. The goal of the present study was a detailed comparative analysis ofS. aureusHG001 and its isogenicrhodeletion mutant. Proteome analysis revealed significant differences in cellular and extracellular protein profiles, most notably increased amounts of the proteins belonging to the SaeR regulon in the Rho-deficient strain. The SaeRS two-component system acts as a major regulator of virulence gene expression in staphylococci. Higher levels of SaeRS-dependent virulence factors such as adhesins, toxins, and immune evasion proteins in therhomutant resulted in higher virulence in a murine bacteremia model, which was alleviated in arhocomplemented strain. Inhibition of Rho activity by bicyclomycin, a specific inhibitor of Rho activity, also induced the expression of SaeRS-dependent genes, at both the mRNA and protein levels, to the same extent as observed in therhomutant. Taken together, these findings indicate that activation of the Sae system in the absence of Rho is directly linked to Rho’s transcription termination activity and establish a new link between antibiotic action and virulence gene expression inS. aureus.IMPORTANCEThe major human pathogenStaphylococcus aureusis a widespread commensal bacterium but also the most common cause of nosocomial infections. It adapts to the different host niches through a complex gene regulatory network. We show here that the Rho transcription termination factor, which represses pervasive antisense transcription in various bacteria, includingS. aureus, plays a role in controlling SaeRS-dependent virulence gene expression. A Rho-deficient strain produces larger amounts of secreted virulence factorsin vitroand shows increased virulence in mice. We also show that treatment ofS. aureuswith the antibiotic bicyclomycin, which inhibits Rho activity and is effective against Gram-negative bacteria, induces the same changes in the proteome as observed in the Rho-deficient strain. Our results reveal for the first time a link between transcription termination and virulence regulation inS. aureus, which implies a novel mechanism by which an antibiotic can modulate the expression of virulence factors.

scholarly journals Analysis of RogB-Controlled Virulence Mechanisms and Gene Expression in Streptococcus agalactiae

2003 ◽  
Vol 71 (9) ◽  
pp. 5056-5064 ◽  
Author(s):  
Heike Gutekunst ◽  
Bernhard J. Eikmanns ◽  
Dieter J. Reinscheid
Keyword(s):  
Gene Expression ◽  
Reporter Gene ◽  
Virulence Factors ◽  
Streptococcus Agalactiae ◽  
Virulence Gene ◽  
Pcr Analysis ◽  
Significant Similarity ◽  
Virulence Gene Expression ◽  
Fibrinogen Receptor ◽  
Wide Range

ABSTRACT Streptococcus agalactiae is the leading cause of bacterial sepsis and meningitis in neonates and also the causative agent of different serious infections in immunocompromised adults. The wide range of diseases that are caused by S. agalactiae suggests regulatory mechanisms that control the formation of specific virulence factors in these bacteria. The present study describes a gene from S. agalactiae, designated rogB, encoding a protein with significant similarity to members of the RofA-like protein (RALP) family of transcriptional regulators. Disruption of the rogB gene in the genome of S. agalactiae resulted in mutant strain RGB1, which was impaired in its ability to bind to fibrinogen and fibronectin. Mutant RGB1 also exhibited a reduced adherence to human epithelial cells but did not show an altered invasion of eukaryotic cells. By real-time PCR analysis, mutant RGB1 revealed an increased expression of the cpsA gene, encoding a regulator of capsule gene expression. However, strain RGB1 exhibited a reduced expression of the rogB gene and of two adjacent genes, encoding putative virulence factors in S. agalactiae. Furthermore, mutant RGB1 was impaired in the expression of the fbsA gene, coding for a fibrinogen receptor from S. agalactiae. The altered gene expression in mutant RGB1 could be restored by plasmid-mediated expression of rogB, confirming a RogB deficiency as the cause for the observed changes in virulence gene expression in S. agalactiae. Reporter gene studies with a promotorless luciferase gene fused to fbsA allowed a growth-dependent analysis of fbsA expression in S. agalactiae. These reporter gene studies also suggest that RogB exerts a positive effect on fbsA expression in S. agalactiae.

Vibrio harveyi virulence gene expression in vitro and in vivo during infection in black tiger shrimp Penaeus monodon

2020 ◽  
Vol 139 ◽  
pp. 153-160
Author(s):  
S Peeralil ◽  
TC Joseph ◽  
V Murugadas ◽  
PG Akhilnath ◽  
VN Sreejith ◽  
...  
Keyword(s):  
Gene Expression ◽  
Virulence Genes ◽  
Vibrio Harveyi ◽  
Penaeus Monodon ◽  
Challenge Test ◽  
Virulence Gene ◽  
Economic Losses ◽  
Virulence Gene Expression

Luminescent Vibrio harveyi is common in sea and estuarine waters. It produces several virulence factors and negatively affects larval penaeid shrimp in hatcheries, resulting in severe economic losses to shrimp aquaculture. Although V. harveyi is an important pathogen of shrimp, its pathogenicity mechanisms have yet to be completely elucidated. In the present study, isolates of V. harveyi were isolated and characterized from diseased Penaeus monodon postlarvae from hatcheries in Kerala, India, from September to December 2016. All 23 tested isolates were positive for lipase, phospholipase, caseinase, gelatinase and chitinase activity, and 3 of the isolates (MFB32, MFB71 and MFB68) showed potential for significant biofilm formation. Based on the presence of virulence genes, the isolates of V. harveyi were grouped into 6 genotypes, predominated by vhpA+ flaB+ ser+ vhh1- luxR+ vopD- vcrD+ vscN-. One isolate from each genotype was randomly selected for in vivo virulence experiments, and the LD50 ranged from 1.7 ± 0.5 × 103 to 4.1 ± 0.1 × 105 CFU ml-1. The expression of genes during the infection in postlarvae was high in 2 of the isolates (MFB12 and MFB32), consistent with the result of the challenge test. However, in MFB19, even though all genes tested were present, their expression level was very low and likely contributed to its lack of virulence. Because of the significant variation in gene expression, the presence of virulence genes alone cannot be used as a marker for pathogenicity of V. harveyi.

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