Ethanolamine Controls Expression of Genes Encoding Components Involved in Interkingdom Signaling and Virulence in Enterohemorrhagic Escherichia coli O157:H7

ABSTRACTBacterial pathogens must be able to both recognize suitable niches within the host for colonization and successfully compete with commensal flora for nutrients in order to establish infection. Ethanolamine (EA) is a major component of mammalian and bacterial membranes and is used by pathogens as a carbon and/or nitrogen source in the gastrointestinal tract. The deadly human pathogen enterohemorrhagicEscherichia coliO157:H7 (EHEC) uses EA in the intestine as a nitrogen source as a competitive advantage for colonization over the microbial flora. Here we show that EA is not only important for nitrogen metabolism but that it is also used as a signaling molecule in cell-to-cell signaling to activate virulence gene expression in EHEC. EA in concentrations that cannot promote growth as a nitrogen source can activate expression of EHEC’s repertoire of virulence genes. The EutR transcription factor, known to be the receptor of EA, is only partially responsible for this regulation, suggesting that yet another EA receptor exists. This important link of EA with metabolism, cell-to-cell signaling, and pathogenesis, highlights the fact that a fundamental means of communication within microbial communities relies on energy production and processing of metabolites. Here we show for the first time that bacterial pathogens not only exploit EA as a metabolite but also coopt EA as a signaling molecule to recognize the gastrointestinal environment and promote virulence expression.IMPORTANCEIn order to successfully cause disease, a pathogen must be able to sense a host environment and modulate expression of its virulence genes as well as compete with the indigenous microbiota for nutrients. Ethanolamine (EA) is present in the large intestine due to the turnover of intestinal cells. Here, we show that the human pathogenEscherichia coliO157:H7, which causes bloody diarrhea and hemolytic-uremic syndrome, regulates virulence gene expression through EA metabolism and by responding to EA as a signal. These findings provide the first information directly linking EA with bacterial pathogenesis.

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Pathovar Transcriptomes

mSystems ◽

10.1128/msystems.00049-17 ◽

2017 ◽

Vol 2 (4) ◽

Cited By ~ 1

Author(s):

Amy Platenkamp ◽

Jay L. Mellies

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Regulatory Networks ◽

Virulence Gene ◽

Model System ◽

Genomic Sequences ◽

Bacterial Strains ◽

Content Type ◽

Virulence Gene Expression ◽

Link Type

ABSTRACT Archetypal pathogenic bacterial strains are often used to elucidate regulatory networks of an entire pathovar, which encompasses multiple lineages and phylogroups. With enteropathogenic Escherichia coli (EPEC) as a model system, Hazen and colleagues (mSystems 6:e00024-17, 2017, https://doi.org/10.1128/mSystems.00024-17 ) used 9 isolates representing 8 lineages and 3 phylogroups to find that isolates with similar genomic sequences exhibit similarities in global transcriptomes under conditions of growth in medium that induces virulence gene expression, and they found variation among individual isolates. Archetypal pathogenic bacterial strains are often used to elucidate regulatory networks of an entire pathovar, which encompasses multiple lineages and phylogroups. With enteropathogenic Escherichia coli (EPEC) as a model system, Hazen and colleagues (mSystems 6:e00024-17, 2017, https://doi.org/10.1128/mSystems.00024-17 ) used 9 isolates representing 8 lineages and 3 phylogroups to find that isolates with similar genomic sequences exhibit similarities in global transcriptomes under conditions of growth in medium that induces virulence gene expression. They also found variation among individual isolates. Their work illustrates the importance of moving beyond observing regulatory phenomena of a limited number of regulons in a few archetypal strains, with the possibility of correlating clinical symptoms to key transcriptional pathways across lineages and phylogroups.

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Indole Signaling at the Host-Microbiota-Pathogen Interface

mBio ◽

10.1128/mbio.01031-19 ◽

2019 ◽

Vol 10 (3) ◽

Cited By ~ 29

Author(s):

Aman Kumar ◽

Vanessa Sperandio

Keyword(s):

Gene Expression ◽

Virulence Genes ◽

Virulence Gene ◽

Enteric Pathogens ◽

Bacterial Membrane ◽

Gi Tract ◽

Intestinal Tissue ◽

Content Type ◽

Virulence Gene Expression ◽

Membrane Bound

ABSTRACTMicrobial establishment within the gastrointestinal (GI) tract requires surveillance of the gut biogeography. The gut microbiota coordinates behaviors by sensing host- or microbiota-derived signals. Here we show for the first time that microbiota-derived indole is highly prevalent in the lumen compared to the intestinal tissue. This difference in indole concentration plays a key role in modulating virulence gene expression of the enteric pathogens enterohemorrhagicEscherichia coli(EHEC) andCitrobacter rodentium. Indole decreases expression of genes within the locus of enterocyte effacement (LEE) pathogenicity island, which is essential for these pathogens to form attaching and effacing (AE) lesions on enterocytes. We synthetically altered the concentration of indole in the GI tracts of mice by employing mice treated with antibiotics to deplete the microbiota and reconstituted with indole-producing commensalBacteroides thetaiotaomicron(B. theta) or aB. thetaΔtnaAmutant (does not produce indole) or by engineering an indole-producingC. rodentiumstrain. This allowed us to assess the role of self-produced versus microbiota-produced indole, and the results show that decreased indole concentrations promote bacterial pathogenesis, while increased levels of indole decrease bacterial virulence gene expression. Moreover, we identified the bacterial membrane-bound histidine sensor kinase (HK) CpxA as an indole sensor. Enteric pathogens sense a gradient of indole concentrations in the gut to probe different niches and successfully establish an infection.IMPORTANCEPathogens sense and respond to several small molecules within the GI tract to modulate expression of their virulence repertoire. Indole is a signaling molecule produced by the gut microbiota. Here we show that indole concentrations are higher in the lumen, where the microbiota is present, than in the intestinal tissue. The enteric pathogens EHEC andC. rodentiumsense indole to downregulate expression of their virulence genes, as a read-out of the luminal compartment. We also identified the bacterial membrane-bound HK CpxA as an indole sensor. This regulation ensures that EHEC andC. rodentiumexpress their virulence genes only at the epithelial lining, which is the niche they colonize.

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Reconstitution of Acetosyringone-Mediated Agrobacterium tumefaciens Virulence Gene Expression in the Heterologous Host Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.183.12.3704-3711.2001 ◽

2001 ◽

Vol 183 (12) ◽

pp. 3704-3711 ◽

Cited By ~ 23

Author(s):

Scott M. Lohrke ◽

Hongjiang Yang ◽

Shouguang Jin

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Agrobacterium Tumefaciens ◽

Virulence Genes ◽

Virulence Gene ◽

Dependent Manner ◽

Gene Encoding ◽

Virulence Gene Expression ◽

E Coli ◽

Glucose Binding

ABSTRACT The ability to utilize Escherichia coli as a heterologous system in which to study the regulation ofAgrobacterium tumefaciens virulence genes and the mechanism of transfer DNA (T-DNA) transfer would provide an important tool to our understanding and manipulation of these processes. We have previously reported that the rpoA gene encoding the alpha subunit of RNA polymerase is required for the expression of lacZ gene under the control of virB promoter (virBp::lacZ) in E. colicontaining a constitutively active virG gene [virG(Con)]. Here we show that an RpoA hybrid containing the N-terminal 247 residues from E. coli and the C-terminal 89 residues from A. tumefaciens was able to significantly express virBp::lacZ in E. coli in a VirG(Con)-dependent manner. Utilization oflac promoter-driven virA and virGin combination with the A. tumefaciens rpoA construct resulted in significant inducer-mediated expression of thevirBp::lacZ fusion, and the level ofvirBp::lacZ expression was positively correlated to the copy number of the rpoA construct. This expression was dependent on VirA, VirG, temperature, and, to a lesser extent, pH, which is similar to what is observed in A. tumefaciens. Furthermore, the effect of sugars on virgene expression was observed only in the presence of thechvE gene, suggesting that the glucose-binding protein ofE. coli, a homologue of ChvE, does not interact with the VirA molecule. We also evaluated other phenolic compounds in induction assays and observed significant expression with syringealdehyde, a low level of expression with acetovanillone, and no expression with hydroxyacetophenone, similar to what occurs in A. tumefaciens strain A348 from which the virA clone was derived. These data support the notion that VirA directly senses the phenolic inducer. However, the overall level of expression of thevir genes in E. coli is less than what is observed in A. tumefaciens, suggesting that additional gene(s) from A. tumefaciens may be required for the full expression of virulence genes in E. coli.

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Influence of Sublethal Concentrations of Common Disinfectants on Expression of Virulence Genes in Listeria monocytogenes

Applied and Environmental Microbiology ◽

10.1128/aem.00925-09 ◽

2009 ◽

Vol 76 (1) ◽

pp. 303-309 ◽

Cited By ~ 37

Author(s):

Vicky G. Kastbjerg ◽

Marianne Halberg Larsen ◽

Lone Gram ◽

Hanne Ingmer

Keyword(s):

Gene Expression ◽

Listeria Monocytogenes ◽

Northern Blot ◽

Food Industry ◽

Virulence Genes ◽

Virulence Gene ◽

Human Pathogen ◽

Active Components ◽

Virulence Gene Expression ◽

Sublethal Concentrations

ABSTRACT Listeria monocytogenes is a food-borne human pathogen that causes listeriosis, a relatively rare infection with a high fatality rate. The regulation of virulence gene expression is influenced by several environmental factors, and the aim of the present study was to determine how disinfectants used routinely in the food industry affect the expression of different virulence genes in L. monocytogenes when added at sublethal concentrations. An agar-based assay was developed to screen the effect of disinfectants on virulence gene promoter expression and was validated at the transcriptional level by Northern blot analysis. Eleven disinfectants representing four different groups of active components were evaluated in this study. Disinfectants with the same active ingredients had a similar effect on gene expression. Peroxy and chlorine compounds reduced the expression of the virulence genes, and quaternary ammonium compounds (QAC) induced the expression of the virulence genes. In general, a disinfectant had similar effects on the expression of all four virulence genes examined. Northern blot analyses confirmed the downregulation of prfA and inlA expression by Incimaxx DES (a peroxy compound) and their upregulation by Triquart Super (a QAC) in L. monocytogenes EGD. Hence, sublethal concentrations of disinfectants routinely used in the food industry affect virulence gene expression in the human pathogen L. monocytogenes, and the effect depends on the active components of the disinfectant. From a practical perspective, the study underlines that disinfectants should be used at the lethal concentrations recommended by the manufacturers. Further studies are needed to elucidate whether the changes in virulence gene expression induced by the disinfectants have impact on virulence or other biological properties, such as antibiotic resistance.

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Method for Screening Compounds That Influence Virulence Gene Expression in Staphylococcus aureus

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00940-09 ◽

2009 ◽

Vol 54 (1) ◽

pp. 509-512 ◽

Cited By ~ 26

Author(s):

Anita Nielsen ◽

Kristian F. Nielsen ◽

Dorte Frees ◽

Thomas O. Larsen ◽

Hanne Ingmer

Keyword(s):

Gene Expression ◽

Staphylococcus Aureus ◽

Virulence Genes ◽

Color Change ◽

Virulence Gene ◽

Human Pathogen ◽

Virulence Gene Expression ◽

Transcriptional Reporter ◽

Reporter Strains ◽

Different Sources

ABSTRACT We present a simple assay to examine effects of compounds on virulence gene expression in the human pathogen Staphylococcus aureus. The assay employs transcriptional reporter strains carrying lacZ fused to central virulence genes. Compounds affecting virulence gene expression and activity of the agr locus are scored based on color change in the presence of a chromogenic β-galactosidase substrate. The assay can be used to screen for novel antivirulence compounds from many different sources, such as fungi, as demonstrated here.

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Effect of Rubusoside, a Natural Sucrose Substitute, on Streptococcus mutans Biofilm Cariogenic Potential and Virulence Gene Expression In Vitro

Applied and Environmental Microbiology ◽

10.1128/aem.01012-20 ◽

2020 ◽

Vol 86 (16) ◽

Author(s):

Chunru Guan ◽

Faai Che ◽

Huoxiang Zhou ◽

Yiwei Li ◽

Yaru Li ◽

...

Keyword(s):

Gene Expression ◽

Dental Caries ◽

Streptococcus Mutans ◽

Virulence Genes ◽

Virulence Gene ◽

Extracellular Polysaccharides ◽

Bacterial Viability ◽

Content Type ◽

Virulence Gene Expression ◽

The Impact

ABSTRACT Dental caries is a biofilm-mediated disease in which Streptococcus mutans is the main pathogenic microorganism, and its incidence is closely related to sucrose. Rubusoside is a natural nonnutritive sweetener isolated from Rubus suavissimus S. Lee. This study was designed to determine the effect of this sucrose substitute on the cariogenic properties and virulence gene expression of S. mutans biofilms. S. mutans was exposed to brain heart infusion (BHI) medium (as a control), 1% sucrose-supplemented medium, 1% rubusoside-supplemented medium, and 1% xylitol-supplemented medium. The growth curve of the biofilm was monitored by crystal violet staining, and the pH was measured every 24 h. After 5 days, the biofilms formed on the glass coverslips were recovered to determine the biomass (dry weight and total amount of soluble proteins), numbers of CFU, and amounts of intra- and extracellular polysaccharides. Biofilm structural imaging was performed using a scanning electron microscope (SEM). Virulence gene expression (gtfB, gtfC, gtfD, ftf, spaP, gbpB, ldh, atpF, vicR, and comD) was determined by reverse transcription-quantitative PCR. Growth in rubusoside resulted in lower levels of acid production than observed during growth in sucrose, xylitol, and the control, while it also reduced the level of biofilm accumulation and bacterial viability and even reduced the level of production of extracellular polysaccharides. By SEM, the levels of biofilm formation and extracellular matrix during growth in rubusoside were lower than these levels during growth in sucrose and xylitol. From the perspective of virulence genes, growth in rubusoside and xylitol significantly inhibited the expression of virulence genes compared with their levels of expression after growth in sucrose. Among these genes, gtfB, gtfC, gbpB, ldh, and comD downregulation was found with growth in rubusoside compared with their expression with growth in xylitol. Therefore, rubusoside appears to be less potentially cariogenic than sucrose and xylitol and may become an effective sucrose substitute for caries prevention. Further studies are needed to deepen these findings. IMPORTANCE Dental caries is a major public health challenge and places heavy biological, social, and financial burdens on individuals and health care systems. To palliate the deleterious effect of sucrose on the virulence factors of S. mutans, massive commercial efforts have been oriented toward developing products that may act as sucrose substitutes. Rubusoside, a natural sucrose substitute, is a plant extract with a high level of sweetness. Although some studies have shown that rubusoside does not produce acids or inhibit the growth of S. mutans, little attention has been paid to its effect on dental biofilm and the underlying mechanisms. Our study focuses on the effect of rubusoside on the formation and structure of biofilms and the expression of virulence genes. The results confirm that rubusoside can inhibit accumulation, bacterial viability, polysaccharide production by the biofilm, and related gene expression. These results provide further insight into the cariogenicity of S. mutans biofilms and demonstrate a new perspective for studying the impact of sucrose substitutes on caries.

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Polyphosphate Kinase Antagonizes Virulence Gene Expression inFrancisella tularensis

Journal of Bacteriology ◽

10.1128/jb.00460-17 ◽

2017 ◽

Vol 200 (3) ◽

Cited By ~ 1

Author(s):

Amy E. Rohlfing ◽

Kathryn M. Ramsey ◽

Simon L. Dove

Keyword(s):

Gene Expression ◽

Rna Polymerase ◽

Virulence Genes ◽

Virulence Gene ◽

Dna Binding Protein ◽

Polyphosphate Kinase ◽

Prior Work ◽

Content Type ◽

Virulence Gene Expression ◽

Regulatory Effects

ABSTRACTThe alarmone ppGpp is a critical regulator of virulence gene expression inFrancisella tularensis. In this intracellular pathogen, ppGpp is thought to work in concert with the putative DNA-binding protein PigR and the SspA protein family members MglA and SspA to control a common set of genes. MglA and SspA form a complex that interacts with RNA polymerase (RNAP), and PigR functions by interacting with the RNAP-associated MglA-SspA complex. Prior work suggested that ppGpp indirectly exerts its regulatory effects inF. tularensisby promoting the accumulation of polyphosphate in the cell, which in turn was required for formation of the MglA-SspA complex. Here we show that inEscherichia coli, neither polyphosphate nor ppGpp is required for formation of the MglA-SspA complex but that ppGpp promotes the interaction between PigR and the MglA-SspA complex. Moreover, we show that polyphosphate kinase, the enzyme responsible for the synthesis of polyphosphate, antagonizes virulence gene expression inF. tularensis, a finding that is inconsistent with the notion that polyphosphate accumulation promotes virulence gene expression in this organism. Our findings identify polyphosphate kinase as a novel negative regulator of virulence gene expression inF. tularensisand support a model in which ppGpp exerts its positive regulatory effects by promoting the interaction between PigR and the MglA-SspA complex.IMPORTANCEInFrancisella tularensis, MglA and SspA form a complex that associates with RNA polymerase to positively control the expression of key virulence genes. The MglA-SspA complex works together with the putative DNA-binding protein PigR and the alarmone ppGpp. PigR functions by interacting directly with the MglA-SspA complex, but how ppGpp exerts its effects was unclear. Prior work indicated that ppGpp acts by promoting the accumulation of polyphosphate, which is required for MglA and SspA to interact. Here we show that formation of the MglA-SspA complex does not require polyphosphate. Furthermore, we find that polyphosphate antagonizes the expression of virulence genes inF. tularensis. Thus, ppGpp does not promote virulence gene expression in this organism through an effect on polyphosphate.

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The Norepinephrine Metabolite 3,4-Dihydroxymandelic Acid Is Produced by the Commensal Microbiota and Promotes Chemotaxis and Virulence Gene Expression in Enterohemorrhagic Escherichia coli

Infection and Immunity ◽

10.1128/iai.00431-17 ◽

2017 ◽

Vol 85 (10) ◽

Cited By ~ 10

Author(s):

Nitesh Sule ◽

Sasi Pasupuleti ◽

Nandita Kohli ◽

Rani Menon ◽

Lawrence J. Dangott ◽

...

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Virulence Gene ◽

The United States ◽

Enterohemorrhagic Escherichia Coli ◽

Dependent Manner ◽

Content Type ◽

Virulence Gene Expression ◽

E Coli ◽

Commensal Microbiota

ABSTRACT Enterohemorrhagic Escherichia coli (EHEC) is a commonly occurring foodborne pathogen responsible for numerous multistate outbreaks in the United States. It is known to infect the host gastrointestinal tract, specifically, in locations associated with lymphoid tissue. These niches serve as sources of enteric neurotransmitters, such as epinephrine and norepinephrine, that are known to increase virulence in several pathogens, including enterohemorrhagic E. coli. The mechanisms that allow pathogens to target these niches are poorly understood. We previously reported that 3,4-dihydroxymandelic acid (DHMA), a metabolite of norepinephrine produced by E. coli, is a chemoattractant for the nonpathogenic E. coli RP437 strain. Here we report that DHMA is also a chemoattractant for EHEC. In addition, DHMA induces the expression of EHEC virulence genes and increases attachment to intestinal epithelial cells in vitro in a QseC-dependent manner. We also show that DHMA is present in murine gut fecal contents and that its production requires the presence of the commensal microbiota. On the basis of its ability to both attract and induce virulence gene expression in EHEC, we propose that DHMA acts as a molecular beacon to target pathogens to their preferred sites of infection in vivo.

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

Diseases of Aquatic Organisms ◽

10.3354/dao03475 ◽

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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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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