scholarly journals Relevance of Peptide Uptake Systems to the Physiology and Virulence of Streptococcus agalactiae

2004 ◽  
Vol 186 (5) ◽  
pp. 1398-1408 ◽  
Author(s):  
Ulrike Samen ◽  
Birgit Gottschalk ◽  
Bernhard J. Eikmanns ◽  
Dieter J. Reinscheid
Keyword(s):  
Abc Transporter ◽  
Streptococcus Agalactiae ◽  
Virulence Gene ◽  
Pcr Analysis ◽  
Amniotic Cavity ◽  
Virulence Gene Expression ◽  
Reverse Transcription Pcr ◽  
Virulence Traits ◽  
Oligopeptide Permease ◽  
Peptide Uptake

ABSTRACT Streptococcus agalactiae is a major cause of invasive infections in human newborns. To satisfy its growth requirements, S. agalactiae takes up 9 of the 20 proteinogenic amino acids from the environment. Defined S. agalactiae mutants in one or several of four putative peptide permease systems were constructed and tested for peptide uptake, growth in various media, and expression of virulence traits. Oligopeptide uptake by S. agalactiae was shown to be mediated by the ABC transporter OppA1-F, which possesses two substrate-binding proteins (OppA1 and OppA2) with overlapping substrate specificities. Dipeptides were found to be taken up in parallel by the oligopeptide permease OppA1-F, by the dipeptide ABC transporter DppA-E, and by the dipeptide symporter DpsA. Reverse transcription-PCR analysis revealed a polycistronic organization of the genes oppA1-F and dppA-E and a monocistronic organization of dpsA in S. agalactiae. The results of quantitative real-time PCR revealed a medium-dependent expression of the operons dppA-E and oppA1-F in S. agalactiae. Growth of S. agalactiae in human amniotic fluid was shown to require an intact dpsA gene, indicating an important role of DpsA during the infection of the amniotic cavity by S. agalactiae. Deletion of the oppB gene reduced the adherence of S. agalactiae to epithelial cells by 26%, impaired its adherence to fibrinogen and fibronectin by 42 and 33%, respectively, and caused a 35% reduction in expression of the fbsA gene, which encodes a fibrinogen-binding protein in S. agalactiae. These data indicate that the oligopeptide permease is involved in modulating virulence traits and virulence gene expression in S. agalactiae.

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.

Glucose Decreases Virulence Gene Expression of Escherichia coli O157:H7

2012 ◽  
Vol 75 (4) ◽  
pp. 748-752 ◽  
Author(s):  
V. DELCENSERIE ◽  
G. LaPOINTE ◽  
T. CHARASLERTRANGSI ◽  
A. RABALSKI ◽  
M. W. GRIFFITHS
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Quorum Sensing ◽  
Shiga Toxin ◽  
Virulence Gene ◽  
Escherichia Coli O157 ◽  
Virulence Gene Expression ◽  
E Coli ◽  
Reverse Transcription Pcr ◽  
Enterocyte Effacement

Escherichia coli O157:H7 is responsible for a human toxico-infection that can lead to severe complications such as hemolytic uremic syndrome. Inside the intestine, E. coli O157:H7 forms typical attaching-effacing lesions and produces Shiga toxins. The genes that are responsible for these lesions are located in a pathogenicity island called the locus of enterocyte effacement (LEE). LEE gene expression is influenced by quorum sensing through the luxS system. In this study, the effect of glucose on the expression of several genes from LEE, on the expression of Shiga toxin genes, and on the expression of luxS was assessed with real-time, reverse transcription PCR. All concentrations of glucose (from 0.1 to 1%) were able to down-regulate genes from the LEE operon. A slight down-regulation of genes implicated in Shiga toxin expression was also observed but was significant for low doses of glucose (0.1 to 0.5%) only. A slight but significant increase in luxS expression was observed with 1% glucose. This confirms that in addition to quorum sensing, the presence or absence of nutrients such as glucose has an impact on the down- or upregulation of LEE-encoded virulence genes by the bacterium. The influence of glucose on the virulence of E. coli O157:H7 has received little attention, and these results suggest that glucose can have an important effect on the virulence of E. coli O157:H7.

scholarly journals Role of Staphylococcus aureus Global Regulators sae and σB in Virulence Gene Expression during Device-Related Infection

2005 ◽  
Vol 73 (6) ◽  
pp. 3415-3421 ◽  
Author(s):  
Christiane Goerke ◽  
Ursula Fluckiger ◽  
Andrea Steinhuber ◽  
Vittoria Bisanzio ◽  
Martina Ulrich ◽  
...  
Keyword(s):  
Gene Expression ◽  
Staphylococcus Aureus ◽  
Virulence Gene ◽  
Northern Analysis ◽  
Virulence Gene Expression ◽  
Global Regulators ◽  
Reverse Transcription Pcr ◽  
Direct Cross

ABSTRACT The ability of Staphylococcus aureus to adapt to different environments is due to a regulatory network comprising several loci. Here we present a detailed study of the interaction between the two global regulators sae and σB of S. aureus and their influence on virulence gene expression in vitro, as well as during device-related infection. The expression of sae, asp23, hla, clfA, coa, and fnbA was determined in strain Newman and its isogenic saeS/R and sigB mutants by Northern analysis and LightCycler reverse transcription-PCR. There was no indication of direct cross talk between the two regulators. sae had a dominant effect on target gene expression during device-related infection. σB seemed to be less active throughout the infection than under induced conditions in vitro.

scholarly journals Use of a Continuous-Flow Anaerobic Culture To Characterize Enteric Virulence Gene Expression

2004 ◽  
Vol 72 (7) ◽  
pp. 3793-3802 ◽  
Author(s):  
Fernando Ruiz-Perez ◽  
Jalaluddin Sheikh ◽  
Suzanne Davis ◽  
Edgar C. Boedeker ◽  
James P. Nataro
Keyword(s):  
Continuous Flow ◽  
Test Organism ◽  
Virulence Gene ◽  
Culture Method ◽  
Commensal Bacteria ◽  
Anaerobic Culture ◽  
Virulence Gene Expression ◽  
Reverse Transcription Pcr ◽  
Eaec Strain

ABSTRACT We developed an in vitro culture method to characterize the expression of bacterial genes under conditions mimicking the colonic environment. Our culture system (the intestinal simulator) comprised a continuous-flow anaerobic culture which was inoculated with fecal samples from healthy volunteers. As a test organism, we employed enteroaggregative Escherichia coli (EAEC), an emerging diarrheal pathogen that is thought to cause infection in both the small and large intestines. After the simulator culture achieved equilibrium conditions, we inoculated the system with prototype EAEC strain 042 and assessed the expression of three EAEC virulence-related genes. We focused particularly on expression of aggR, which encodes a global transcriptional regulator of EAEC virulence factors, and two AggR-regulated genes. By using real-time quantitative reverse transcription-PCR, we showed that aggR expression in the simulator is increased 3- to 10-fold when 042 is grown under low-pH (5.5 to 6.0) conditions, compared with results with neutral pH (7.0). Interestingly, however, this effect was seen only when the strain was grown in the presence of commensal bacteria. We also found that expression of aggR is 10- to 20-fold higher at low NaCl concentrations, and this effect was also observed only in the presence of commensal bacteria. Using coculture and conditioned-media experiments, we identified specific strains of Enterococcus and Clostridium that upregulated aggR expression; in contrast, strains of Lactobacillus and Veillonella downregulated aggR expression. Our data provide new insights into regulation of virulence genes in EAEC and suggest the utility of intestinal simulation cultures in characterizing enteric gene regulation.

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 Culture of Campylobacter jejuni with Sodium Deoxycholate Induces Virulence Gene Expression

2008 ◽  
Vol 190 (7) ◽  
pp. 2286-2297 ◽  
Author(s):  
Preeti Malik-Kale ◽  
Craig T. Parker ◽  
Michael E. Konkel
Keyword(s):  
Campylobacter Jejuni ◽  
Cell Invasion ◽  
Virulence Gene ◽  
Sodium Deoxycholate ◽  
Culture Conditions ◽  
Metabolic Labeling ◽  
Virulence Gene Expression ◽  
Reverse Transcription Pcr ◽  
Virulence Potential

ABSTRACT Campylobacter jejuni, a spiral-shaped gram-negative bacterium, is a leading bacterial cause of human food-borne illness. Acute disease is associated with C. jejuni invasion of the intestinal epithelium. Further, maximal host cell invasion requires the secretion of proteins termed Campylobacter invasion antigens (Cia). As bile acids are known to alter the pathogenic behavior of other gastrointestinal pathogens, we hypothesized that the virulence potential of Campylobacter may be triggered by the bile acid deoxycholate (DOC). In support of this hypothesis, culturing C. jejuni with a physiologically relevant concentration of DOC significantly altered the kinetics of cell invasion, as shown by gentamicin protection assays. In contrast to C. jejuni harvested from Mueller-Hinton (MH) agar plates, C. jejuni harvested from MH agar plates supplemented with DOC secreted the Cia proteins, as judged by metabolic labeling experiments. DOC was also found to induce the expression of the ciaB gene, as determined by β-galactosidase reporter, real-time reverse transcription-PCR, and microarray analyses. Microarray analysis further revealed that DOC induced the expression of virulence genes (ciaB, cmeABC, dccR, and tlyA). In summary, we demonstrated that it is possible to enhance the pathogenic behavior of C. jejuni by modifying the culture conditions. These results provide a foundation for identifying genes expressed by C. jejuni in response to in vivo-like culture conditions.

scholarly journals Intergeneric Communication in Dental Plaque Biofilms

2000 ◽  
Vol 182 (24) ◽  
pp. 7067-7069 ◽  
Author(s):  
Hua Xie ◽  
Guy S. Cook ◽  
J. William Costerton ◽  
Greg Bruce ◽  
Timothy M. Rose ◽  
...  
Keyword(s):  
Gene Expression ◽  
Information Flow ◽  
Dental Plaque ◽  
Virulence Gene ◽  
Surface Protein ◽  
Reporter Construct ◽  
Gram Negative ◽  
Virulence Gene Expression ◽  
Reverse Transcription Pcr ◽  
Signaling Activity

ABSTRACT Dental plaque is a complex biofilm that accretes in a series of discrete steps proceeding from a gram-positive streptococcus-rich biofilm to a structure rich in gram-negative anaerobes. This study investigated information flow between two unrelated plaque bacteria,Streptococcus cristatus and Porphyromonas gingivalis. A surface protein of S. cristatus caused repression of the P. gingivalisfimbrial gene (fimA), as determined by a chromosomalfimA promoter-lacZ reporter construct and by reverse transcription-PCR. Signaling activity was associated with a 59-kDa surface protein of S. cristatus and showed specificity for the fimA gene. Furthermore, P. gingivalis was unable to form biofilm microcolonies with S. cristatus. Thus, S. cristatus is capable of modulating virulence gene expression in P. gingivalis, consequently influencing the development of pathogenic plaque.

scholarly journals Induction of Virulence Gene Expression in Staphylococcus aureus by Pulmonary Surfactant

2014 ◽  
Vol 82 (4) ◽  
pp. 1500-1510 ◽  
Author(s):  
Kenichi Ishii ◽  
Tatsuo Adachi ◽  
Jyunichiro Yasukawa ◽  
Yutaka Suzuki ◽  
Hiroshi Hamamoto ◽  
...  
Keyword(s):  
Gene Expression ◽  
Staphylococcus Aureus ◽  
Stress Responses ◽  
Pulmonary Surfactant ◽  
Virulence Gene ◽  
Pcr Analysis ◽  
Host Animal ◽  
Content Type ◽  
Disruption Mutant ◽  
Virulence Gene Expression

ABSTRACTWe performed a genomewide analysis using a next-generation sequencer to investigate the effect of pulmonary surfactant on gene expression inStaphylococcus aureus, a clinically important opportunistic pathogen. RNA sequence (RNA-seq) analysis of bacterial transcripts at late log phase revealed 142 genes that were upregulated >2-fold following the addition of pulmonary surfactant to the culture medium. Among these genes, we confirmed by quantitative reverse transcription-PCR analysis that mRNA amounts for genes encoding ESAT-6 secretion system C (EssC), an unknown hypothetical protein (NWMN_0246; also called pulmonary surfactant-inducible factor A [PsiA] in this study), and hemolysin gamma subunit B (HlgB) were increased 3- to 10-fold by the surfactant treatment. Among the major constituents of pulmonary surfactant, i.e., phospholipids and palmitate, only palmitate, which is the most abundant fatty acid in the pulmonary surfactant and a known antibacterial substance, stimulated the expression of these three genes. Moreover, these genes were also induced by supplementing the culture with detergents. The induction of gene expression by surfactant or palmitate was not observed in a disruption mutant of thesigBgene, which encodes an alternative sigma factor involved in bacterial stress responses. Furthermore, each disruption mutant of theessC,psiA, andhlgBgenes showed attenuation of both survival in the lung and host-killing ability in a murine pneumonia model. These findings suggest thatS. aureusresists membrane stress caused by free fatty acids present in the pulmonary surfactant through the regulation of virulence gene expression, which contributes to its pathogenesis within the lungs of the host animal.

scholarly journals Effect of Heat Shock and Mutations in ClpL and ClpP on Virulence Gene Expression in Streptococcus pneumoniae

2003 ◽  
Vol 71 (7) ◽  
pp. 3757-3765 ◽  
Author(s):  
Hyog-Young Kwon ◽  
Seung-Whan Kim ◽  
Moo-Hyun Choi ◽  
A. David Ogunniyi ◽  
James C. Paton ◽  
...  
Keyword(s):  
Gene Expression ◽  
Streptococcus Pneumoniae ◽  
Heat Shock ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Immunoblot Analysis ◽  
Pcr Analysis ◽  
Infection Model ◽  
Dependent Manner ◽  
Virulence Gene Expression

ABSTRACT Spread of Streptococcus pneumoniae from the nasopharynx to other host tissues would require the organism to adapt to a variety of environmental conditions. Since heat shock proteins are induced by environmental stresses, we investigated the effect of heat shock on ClpL and ClpP synthesis and the effect of clpL and clpP mutations on the expression of key pneumococcal virulence genes. Pulse labeling with [35S]methionine and chase experiments as well as immunoblot analysis demonstrated that ClpL, DnaK, and GroEL were stable. Purified recombinant ClpL refolded urea-denatured rhodanese in a dose-dependent manner, demonstrating ClpL's chaperone activity. Although growth of the clpL mutant was not affected at 30 or 37°C, growth of the clpP mutant was severely affected at these temperatures. However, both clpL and clpP mutants were sensitive to 43°C. Although it was further induced by heat shock, the level of expression of ClpL in the clpP mutant was high at 30°C, suggesting that ClpP represses expression of ClpL. Furthermore, the clpP mutation significantly attenuated the virulence of S. pneumoniae in a murine intraperitoneal infection model, whereas the clpL mutation did not. Interestingly, immunoblot and real-time reverse transcription-PCR analysis demonstrated that pneumolysin and pneumococcal surface antigen A were induced by heat shock in wild-type S. pneumoniae. Other virulence genes were also affected by heat shock and clpL and clpP mutations. Virulence gene expression seems to be modulated not only by heat shock but also by the ClpL and ClpP proteases.

Tannin-Rich Pomegranate Rind Extracts Reduce Adhesion to and Invasion of Caco-2 Cells by Listeria monocytogenes and Decrease Its Expression of Virulence Genes

2015 ◽  
Vol 78 (1) ◽  
pp. 128-133 ◽  
Author(s):  
YUNFENG XU ◽  
GUANGHUI LI ◽  
BAIGANG ZHANG ◽  
QIAN WU ◽  
XIN WANG ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Epithelial Cells ◽  
Virulence Genes ◽  
Growth Curves ◽  
Virulence Gene ◽  
Antimicrobial Activities ◽  
Pcr Analysis ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Virulence Gene Expression

Pomegranate rind is rich in tannins that have remarkable antimicrobial activities. This study aimed to evaluate the effects of a tannin-rich fraction from pomegranate rind (TFPR) on Listeria monocytogenes virulence gene expression and on the pathogen's interaction with human epithelial cells. Growth curves were monitored to determine the effect of TFPR on L. monocytogenes growth. The 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide and fluorescence staining assays were used to examine the cytotoxicity of TFPR. The effects of TFPR on L. monocytogenes adhesion to and invasion of epithelial cells were investigated using Caco-2 cells. Real-time quantitative PCR analysis was conducted to quantify mRNA levels of three virulence genes in L. monocytogenes. Results showed that a MIC of TFPR against L. monocytogenes was 5 mg/ml in this study. TFPR exhibited cytotoxicity against Caco-2 cells when the concentration was 2.5 mg/ml. Subinhibitory concentrations of TFPR significantly reduced, in a dose-dependent manner, adhesion to and invasion of Caco-2 cells by L. monocytogenes. When L. monocytogenes was grown in the presence of 2.5 mg/ml TFPR, the transcriptional levels of prfA, inlA, and hly decreased by 17-, 34-, and 28-fold, respectively.

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