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

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.

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

Journal of Bacteriology ◽

10.1128/jb.00012-18 ◽

2018 ◽

Vol 200 (8) ◽

Cited By ~ 14

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.

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

Journal of Bacteriology ◽

10.1128/jb.00370-09 ◽

2009 ◽

Vol 191 (17) ◽

pp. 5387-5397 ◽

Cited By ~ 56

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.

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

Infection and Immunity ◽

10.1128/iai.74.5.3060-3064.2006 ◽

2006 ◽

Vol 74 (5) ◽

pp. 3060-3064 ◽

Cited By ~ 30

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.

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

Infection and Immunity ◽

10.1128/iai.66.12.5854-5861.1998 ◽

1998 ◽

Vol 66 (12) ◽

pp. 5854-5861 ◽

Cited By ~ 53

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.

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

PLoS Pathogens ◽

10.1371/journal.ppat.1009791 ◽

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.

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Induction of Virulence Gene Expression in Staphylococcus aureus by Pulmonary Surfactant

Infection and Immunity ◽

10.1128/iai.01635-13 ◽

2014 ◽

Vol 82 (4) ◽

pp. 1500-1510 ◽

Cited By ~ 23

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.

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

Infection and Immunity ◽

10.1128/iai.71.7.3757-3765.2003 ◽

2003 ◽

Vol 71 (7) ◽

pp. 3757-3765 ◽

Cited By ~ 77

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.

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The Tzs Protein and Exogenous Cytokinin Affect Virulence Gene Expression and Bacterial Growth of Agrobacterium tumefaciens

Phytopathology ◽

10.1094/phyto-01-13-0020-r ◽

2013 ◽

Vol 103 (9) ◽

pp. 888-899 ◽

Cited By ~ 16

Author(s):

Hau-Hsuan Hwang ◽

Fong-Jhih Yang ◽

Tun-Fang Cheng ◽

Yi-Chun Chen ◽

Ying-Ling Lee ◽

...

Keyword(s):

Gene Expression ◽

Agrobacterium Tumefaciens ◽

Bacterial Growth ◽

Deletion Mutant ◽

Virulence Gene ◽

Protein Accumulation ◽

Virulence Gene Expression ◽

Crown Gall Disease ◽

Wide Range ◽

Exogenous Cytokinin

The soil phytopathogen Agrobacterium tumefaciens causes crown gall disease in a wide range of plant species. The neoplastic growth at the infection sites is caused by transferring, integrating, and expressing transfer DNA (T-DNA) from A. tumefaciens into plant cells. A trans-zeatin synthesizing (tzs) gene is located in the nopaline-type tumor-inducing plasmid and causes trans-zeatin production in A. tumefaciens. Similar to known virulence (Vir) proteins that are induced by the vir gene inducer acetosyringone (AS) at acidic pH 5.5, Tzs protein is highly induced by AS under this growth condition but also constitutively expressed and moderately upregulated by AS at neutral pH 7.0. We found that the promoter activities and protein levels of several AS-induced vir genes increased in the tzs deletion mutant, a mutant with decreased tumorigenesis and transient transformation efficiencies, in Arabidopsis roots. During AS induction and infection of Arabidopsis roots, the tzs deletion mutant conferred impaired growth, which could be rescued by genetic complementation and supplementing exogenous cytokinin. Exogenous cytokinin also repressed vir promoter activities and Vir protein accumulation in both the wild-type and tzs mutant bacteria with AS induction. Thus, the tzs gene or its product, cytokinin, may be involved in regulating AS-induced vir gene expression and, therefore, affect bacterial growth and virulence during A. tumefaciens infection.

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Characterization of the roles of activated charcoal and Chelex in the induction of PrfA regulon expression in complex medium

PLoS ONE ◽

10.1371/journal.pone.0250989 ◽

2021 ◽

Vol 16 (4) ◽

pp. e0250989

Author(s):

Ahmed Gaballa ◽

Sriya Sunil ◽

Etienne Doll ◽

Sarah I. Murphy ◽

Tyler Bechtel ◽

...

Keyword(s):

Gene Expression ◽

Activated Charcoal ◽

Metal Ion ◽

Expression Patterns ◽

Brain Heart Infusion ◽

Virulence Gene ◽

Listeriolysin O ◽

Virulence Gene Expression ◽

Wide Range ◽

Regulated Gene Expression

The foodborne pathogen Listeria monocytogenes is able to survive across a wide range of intra- and extra-host environments by appropriately modulating gene expression patterns in response to different stimuli. Positive Regulatory Factor A (PrfA) is the major transcriptional regulator of virulence gene expression in L. monocytogenes. It has long been known that activated charcoal is required to induce the expression of PrfA-regulated genes in complex media, such as Brain Heart Infusion (BHI), but not in chemically defined media. In this study, we show that the expression of the PrfA-regulated hly, which encodes listeriolysin O, is induced 5- and 8-fold in L. monocytogenes cells grown in Chelex-treated BHI (Ch-BHI) and in the presence of activated charcoal (AC-BHI), respectively, relative to cells grown in BHI medium. Specifically, we show that metal ions present in BHI broth plays a role in the reduced expression of the PrfA regulon. In addition, we show that expression of hly is induced when the levels of bioavailable extra- or intercellular iron are reduced. L. monocytogenes cells grown Ch-BHI and AC-BHI media showed similar levels of resistance to the iron-activated antibiotic, streptonigrin, indicating that activated charcoal reduces the intracellular labile iron pool. Metal depletion and exogenously added glutathione contributed synergistically to PrfA-regulated gene expression since glutathione further increased hly expression in metal-depleted BHI but not in BHI medium. Analyses of transcriptional reporter fusion expression patterns revealed that genes in the PrfA regulon are differentially expressed in response to metal depletion, metal excess and exogenous glutathione. Our results suggest that metal ion abundance plays a role in modulating expression of PrfA-regulated virulence genes in L. monocytogenes.

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Morphological Alterations and Virulence Gene Expression of Listeria Monocytogenes Cells in Response to Gamma Irradiation Treatments

Nutrition and Food Processing ◽

10.31579/2637-8914/055 ◽

2021 ◽

Vol 04 (5) ◽

pp. 01-09

Author(s):

Hamouda Elabed

Keyword(s):

Gene Expression ◽

Fatty Acid ◽

Listeria Monocytogenes ◽

Gamma Irradiation ◽

Membrane Lipids ◽

Virulence Gene ◽

Morphological Alteration ◽

Morphological Alterations ◽

Virulence Gene Expression ◽

Wide Range

Gamma irradiation is one of the most popular ray treatments in food industry. It's used to control micro-organisms proliferation in a wide range of products however the response of bacteria to low doses is still unknown. In this study we mainly focus on morphological alteration and virulence gene expression in Listeria monocytogenes after gamma irradiation treatments. The atomic force micrographs (AFM) showed that 0.5 kGy dose has no effect on the membrane morphology of L. monocytogenes. However, after 0.7 kGy treatment, the cells lost their typical shape and smooth membrane and 1 kGy dose was totally destructive. Moreover, membrane fatty acid composition was analyzed by the chromatographic method after different gamma doses. Significant modifications on fatty acids composition were detected in the irradiated strain showing a novo synthesis of membrane lipids: C12:0; C14:0; C15:0; C16:0 and C18:0. In addition, we reported an increase of the saturated fatty acid, essential for membrane adaptation under stress conditions. The expression levels of three virulence genes (hlyA, fri and prfA) were studied in the same conditions using real-time PCR technique. The analysis revealed that both prfA and fri genes were up-regulated after gamma treatment. The induction of prfA, which is a regulator gene, may affect the expression other genes controlling the adaptive form in the treated strain. This study open prospects for further researches to explain the regulatory mechanisms of the adaptive response in Listeria monocytogenes when exposed to sublethal irradiation-stress.

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