Photo sensing and quorum sensing are integrated to control bacterial group behaviors

ABSTRACTPseudomonas aeruginosa transitions between the free-swimming state and the sessile biofilm mode during its pathogenic lifestyle. We show that quorum sensing represses P. aeruginosa biofilm formation and virulence by activating expression of genes encoding the KinB-AlgB two-component system. Phospho-AlgB represses biofilm and virulence genes, while KinB dephosphorylates, and thereby, inactivates AlgB. We discover that the photoreceptor BphP is the kinase that, in response to light, phosphorylates and activates AlgB. Indeed, exposing P. aeruginosa to light represses biofilm formation and virulence gene expression. To our knowledge, P. aeruginosa was not previously known to detect light. The KinB-AlgB-BphP module is present in all Pseudomonads, and we demonstrate that AlgB is the cognate response regulator for BphP in diverse bacterial phyla. We propose that KinB-AlgB-BphP constitutes a “three-component” system and AlgB is the node at which varied sensory information is integrated. This study sets the stage for light-mediated control of P. aeruginosa infectivity.

Download Full-text

Integration of Cyclic di-GMP and Quorum Sensing in the Control ofvpsTandaphAin Vibrio cholerae

Journal of Bacteriology ◽

10.1128/jb.05167-11 ◽

2011 ◽

Vol 193 (22) ◽

pp. 6331-6341 ◽

Cited By ~ 103

Author(s):

Disha Srivastava ◽

Rebecca C. Harris ◽

Christopher M. Waters

Keyword(s):

Quorum Sensing ◽

Binding Site ◽

Vibrio Cholerae ◽

Biofilm Formation ◽

Virulence Gene ◽

Transcriptional Activator ◽

Transcriptional Regulators ◽

Content Type ◽

Virulence Gene Expression ◽

Signaling Systems

Vibrio choleraetransitions between aquatic environmental reservoirs and infection in the gastrointestinal tracts of human hosts. The second-messenger molecule cyclic di-GMP (c-di-GMP) and quorum sensing (QS) are important signaling systems that enableV. choleraeto alternate between these distinct environments by controlling biofilm formation and virulence factor expression. Here we identify a conserved regulatory mechanism inV. choleraethat integrates c-di-GMP and QS to control the expression of two transcriptional regulators:aphA, an activator of virulence gene expression and an important regulator of the quorum-sensing pathway, andvpsT, a transcriptional activator that induces biofilm formation. Surprisingly,aphAexpression was induced by c-di-GMP. Activation of bothaphAandvpsTby c-di-GMP requires the transcriptional activator VpsR, which binds to c-di-GMP. The VpsR binding site at each of these promoters overlaps with the binding site of HapR, the master QS regulator at high cell densities. Our results suggest thatV. choleraecombines information conveyed by QS and c-di-GMP to appropriately respond and adapt to divergent environments by modulating the expression of key transcriptional regulators.

Download Full-text

sarZ, a sarA Family Gene, Is Transcriptionally Activated by MgrA and Is Involved in the Regulation of Genes Encoding Exoproteins in Staphylococcus aureus

Journal of Bacteriology ◽

10.1128/jb.01555-08 ◽

2008 ◽

Vol 191 (5) ◽

pp. 1656-1665 ◽

Cited By ~ 36

Author(s):

Anand Ballal ◽

Binata Ray ◽

Adhar C. Manna

Keyword(s):

Staphylococcus Aureus ◽

Target Genes ◽

Virulence Gene ◽

Promoter Regions ◽

Regulatory Relationship ◽

Virulence Gene Expression ◽

Regulatory Systems ◽

Expression Of Genes ◽

Genes Encoding ◽

Gel Shift

ABSTRACT The expression of genes involved in the pathogenesis of Staphylococcus aureus is controlled by global regulatory loci, including two-component regulatory systems and transcriptional regulators (e.g., sar family genes). Most members of the SarA family have been partially characterized and shown to regulate a large numbers of target genes. Here, we describe the characterization of sarZ, a sarA paralog from S. aureus, and its regulatory relationship with other members of its family. Expression of sarZ was growth phase dependent with maximal expression in the early exponential phase of growth. Transcription of sarZ was reduced in an mgrA mutant and returned to a normal level in a complemented mgrA mutant strain, which suggests that mgrA acts as an activator of sarZ transcription. Purified MgrA protein bound to the sarZ promoter region, as determined by gel shift assays. Among the sarA family of genes analyzed, inactivation of sarZ increased sarS transcription, while it decreased agr transcription. The expression of potential target genes involved in virulence was evaluated in single and double mutants of sarZ with mgrA, sarX, and agr. Northern and zymogram analyses indicated that the sarZ gene product played a role in regulating several virulence genes, particularly those encoding exoproteins. Gel shift assays demonstrated nonspecific binding of purified SarZ protein to the promoter regions of the sarZ-regulated target genes. These results demonstrate the important role played by SarZ in controlling regulatory and virulence gene expression in S. aureus.

Download Full-text

Cyclic di-GMP Is Integrated Into a Hierarchal Quorum Sensing Network Regulating Antimicrobial Production and Biofilm Formation in Roseobacter Clade Member Rhodobacterales Strain Y4I

Frontiers in Marine Science ◽

10.3389/fmars.2021.681551 ◽

2021 ◽

Vol 8 ◽

Author(s):

April C. Armes ◽

Alison Buchan

Keyword(s):

Quorum Sensing ◽

Biofilm Formation ◽

Homoserine Lactone ◽

Roseobacter Clade ◽

Partial Restoration ◽

Microbial Biofilms ◽

Expression Of Genes ◽

Genes Encoding ◽

Biofilm Development ◽

And Function

Microbial biofilms associated with marine particulate organic matter carry out transformations that influence local and regional biogeochemical cycles. Early microbial colonizers are often hypothesized to “set the stage” for biofilm structure, dynamics, and function via N-acyl homoserine lactone (AHL)-mediated quorum sensing (QS). Production of AHLs, as well as antimicrobials, contributes to the colonization success of members of the Roseobacter clade. One member of this group of abundant marine bacteria, Rhodobacterales sp. Y4I, possesses two QS systems, phaRI (QS1) and pgaRI (QS2). Here, we characterize mutants in both QS systems to provide genetic evidence that the two systems work in hierarchical fashion to coordinate production of the antimicrobial indigoidine as well as biofilm formation. A mutation in pgaR (QS2) results in decreased expression of genes encoding both QS systems as well as those governing the biosynthesis of indigoidine. In contrast, mutations in QS1 did not significantly influence gene expression of QS2. Addition of exogenous AHLs to QS1 and QS2 mutants led to partial restoration of indigoidine production (45–60% of WT) for QS1 but not QS2. Mutational disruptions of QS1 had a more pronounced effect on biofilm development than those in QS2. Finally, we demonstrate that c-di-GMP levels are altered in QS and indigoidine biosynthesis Y4I mutants. Together, these results indicate that pgaRI (QS2) is at the top of a regulatory hierarchy governing indigoidine biosynthesis and that the global regulatory metabolite, c-di-GMP, is likely integrated into the QS circuitry of this strain. These findings provide mechanistic understanding of physiological processes that are important in elucidating factors driving competitiveness of Roseobacters in nature.

Download Full-text

Crystal Structure of the Vibrio cholerae Quorum-Sensing Regulatory Protein HapR

Journal of Bacteriology ◽

10.1128/jb.01807-06 ◽

2007 ◽

Vol 189 (15) ◽

pp. 5683-5691 ◽

Cited By ~ 44

Author(s):

Rukman S. De Silva ◽

Gabriela Kovacikova ◽

Wei Lin ◽

Ronald K. Taylor ◽

Karen Skorupski ◽

...

Keyword(s):

Gene Expression ◽

Crystal Structure ◽

Dna Binding ◽

Quorum Sensing ◽

Vibrio Cholerae ◽

Biofilm Formation ◽

Regulatory Protein ◽

Virulence Gene ◽

Binding Motif ◽

Virulence Gene Expression

ABSTRACT Quorum sensing in Vibrio cholerae involves signaling between two-component sensor protein kinases and the response regulator LuxO to control the expression of the master regulator HapR. HapR, in turn, plays a central role in regulating a number of important processes, such as virulence gene expression and biofilm formation. We have determined the crystal structure of HapR to 2.2-Å resolution. Its structure reveals a dimeric, two-domain molecule with an all-helical structure that is strongly conserved with members of the TetR family of transcriptional regulators. The N-terminal DNA-binding domain contains a helix-turn-helix DNA-binding motif and alteration of certain residues in this domain completely abolishes the ability of HapR to bind to DNA, alleviating repression of both virulence gene expression and biofilm formation. The C-terminal dimerization domain contains a unique solvent accessible tunnel connected to an amphipathic cavity, which by analogy with other TetR regulators, may serve as a binding pocket for an as-yet-unidentified ligand.

Download Full-text

Drug-like Fragments Inhibit agr-Mediated Virulence Expression in Staphylococcus aureus

10.1101/538173 ◽

2019 ◽

Author(s):

Ian F. Bezar ◽

Ameya A. Mashruwala ◽

Jeffrey M. Boyd ◽

Ann M. Stock

Keyword(s):

Staphylococcus Aureus ◽

Biofilm Formation ◽

Pathogenic Bacteria ◽

Response Regulator ◽

Virulence Gene ◽

Drug Resistant ◽

Virulence Gene Expression ◽

Sensing System ◽

Compound Libraries ◽

Quorum Sensing System

In response to the increasingly problematic emergence of antibiotic resistance, novel strategies for combating pathogenic bacteria are being investigated. Targeting the agr quorum sensing system, which regulates expression of virulence in Staphylococcus aureus, is one potentially useful approach for combating drug-resistant pathogens that has not yet been fully explored. A previously published study of a fragment screen resulted in the identification of five compound fragments that interact with the DNA-binding domain of the response regulator AgrA from S. aureus. We have analyzed the ability of these compounds to affect agr-mediated virulence gene expression in S. aureus cells. Three of the compounds demonstrated the ability to reduce agr-driven transcription of at the P2 and P3 promoters of the agr operon and increase biofilm formation, and two of these compounds also showed the ability to reduce levels of secreted toxins. The finding that the compounds tested were able to reduce agr activity suggests that they could be useful tools for probing the effects of agr inhibition.Furthermore, the characteristics of compound fragments make them good starting materials for the development of compound libraries to iteratively improve the inhibitors.

Download Full-text

Aggregation ofVibrio choleraeby cationic polymers enhances quorum sensing but over-rides biofilm dissipation in response to autoinduction

10.1101/333823 ◽

2018 ◽

Author(s):

Nicolas Perez-Soto ◽

Oliver Creese ◽

Francisco Fernandez-Trillo ◽

Anne-Marie Krachler

Keyword(s):

Quorum Sensing ◽

Biofilm Formation ◽

Virulence Gene ◽

Cationic Polymers ◽

Structural Protein ◽

Virulence Gene Expression ◽

Life Styles ◽

Synthetic Materials ◽

Mechanistic Basis ◽

Cross Wire

AbstractVibrio choleraeis a Gram-negative bacterium found in aquatic environments and a human pathogen of global significance. Its transition between host-associated and environmental life styles involves the tight regulation of niche-specific phenotypes such as motility, biofilm formation and virulence.V. cholerae’s transition from the host to environmental dispersal usually involves suppression of virulence and dispersion of biofilm communities. In contrast to this naturally occurring transition, bacterial aggregation by cationic polymers triggers a unique response, which is to suppress virulence gene expression while also triggering biofilm formation byV. cholerae, an artificial combination of traits that is potentially very useful to bind and neutralize the pathogen from contaminated water. Here, we set out to uncover the mechanistic basis of this polymer-triggered bacterial behavior. We found that bacteria-polymer aggregates undergo rapid autoinduction and achieve quorum sensing at bacterial densities far below those required for autoinduction in the absence of polymers. We demonstrate this induction of quorum sensing is due both to a rapid formation of autoinducer gradients and local enhancement of autoinducer concentrations within bacterial clusters, as well as the stimulation of CAI-1 and AI-2 production by aggregated bacteria. We further found that polymers cause an induction of the biofilm specific regulator VpsR and the biofilm structural protein RbmA, bypassing the usual suppression of biofilm during autoinduction. Overall, this study highlights that synthetic materials can be used to cross-wire natural bacterial responses to achieve a combination of phenotypes with potentially useful applications.

Download Full-text

Functional characterization of the BvgAS two-component system of Bordetella holmesii

Microbiology ◽

10.1099/mic.0.27432-0 ◽

2004 ◽

Vol 150 (11) ◽

pp. 3715-3729 ◽

Cited By ~ 19

Author(s):

Gabriele Gerlach ◽

Simone Janzen ◽

Dagmar Beier ◽

Roy Gross

Keyword(s):

Response Regulator ◽

Functional Characterization ◽

Virulence Gene ◽

Two Component System ◽

Component System ◽

Virulence Gene Expression ◽

Signal Perception ◽

Promoter Recognition ◽

Two Component

The BvgAS two-component system is the master regulator of virulence gene expression in the mammalian pathogens Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica. This paper reports the partial cloning and characterization of the bvgAS loci of the ‘new’ Bordetella species Bordetella holmesii, Bordetella trematum and Bordetella hinzii, which are increasingly recognized as opportunistic pathogens in humans. It is demonstrated that the cytoplasmic signalling domains of the BvgS histidine kinases of B. pertussis and B. holmesii are functionally interchangeable, while signal perception by the two sensor proteins seems to be different. Furthermore, it is shown that, despite the high similarity of the BvgA proteins of B. pertussis and B. holmesii, promoter recognition by the response regulator proteins differs substantially in these organisms.

Download Full-text

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.

Download Full-text

RegA, an AraC-Like Protein, Is a Global Transcriptional Regulator That Controls Virulence Gene Expression in Citrobacter rodentium

Infection and Immunity ◽

10.1128/iai.00770-08 ◽

2008 ◽

Vol 76 (11) ◽

pp. 5247-5256 ◽

Cited By ~ 44

Author(s):

Emily Hart ◽

Ji Yang ◽

Marija Tauschek ◽

Michelle Kelly ◽

Matthew J. Wakefield ◽

...

Keyword(s):

Mammalian Cells ◽

Virulence Gene ◽

Virulence Determinants ◽

Intestinal Colonization ◽

Citrobacter Rodentium ◽

Promoter Regions ◽

Reading Frame ◽

Virulence Gene Expression ◽

Genes Encoding ◽

Colonization Factors

ABSTRACT Citrobacter rodentium is an attaching and effacing pathogen which causes transmissible colonic hyperplasia in mice. Infection with C. rodentium serves as a model for infection of humans with enteropathogenic and enterohemorrhagic Escherichia coli. To identify novel colonization factors of C. rodentium, we screened a signature-tagged mutant library of C. rodentium in mice. One noncolonizing mutant had a single transposon insertion in an open reading frame (ORF) which we designated regA because of its homology to genes encoding members of the AraC family of transcriptional regulators. Deletion of regA in C. rodentium resulted in markedly reduced colonization of the mouse intestine. Examination of lacZ transcriptional fusions using promoter regions of known and putative virulence-associated genes of C. rodentium revealed that RegA strongly stimulated transcription of two newly identified genes located close to regA, which we designated adcA and kfcC. The cloned adcA gene conferred autoaggregation and adherence to mammalian cells to E. coli strain DH5α, and a kfc mutation led to a reduction in the duration of intestinal colonization, but the kfc mutant was far less attenuated than the regA mutant. These results indicated that other genes of C. rodentium whose expression required activation by RegA were required for colonization. Microarray analysis revealed a number of RegA-regulated ORFs encoding proteins homologous to known colonization factors. Transcription of these putative virulence determinants was activated by RegA only in the presence of sodium bicarbonate. Taken together, these results show that RegA is a global regulator of virulence in C. rodentium which activates factors that are required for intestinal colonization.

Download Full-text