scholarly journals Competitive Growth Enhances Conditional Growth Mutant Sensitivity to Antibiotics and Exposes a Two-Component System as an Emerging Antibacterial Target in Burkholderia cenocepacia

2016 ◽  
Vol 61 (1) ◽  
Author(s):  
April S. Gislason ◽  
Matthew Choy ◽  
Ruhi A. M. Bloodworth ◽  
Wubin Qu ◽  
Maria S. Stietz ◽  
...  
Keyword(s):  
Mutational Analysis ◽  
Essential Gene ◽  
Burkholderia Cenocepacia ◽  
Competitive Growth ◽  
Bacterial Strains ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Antibacterial Target

ABSTRACT Chemogenetic approaches to profile an antibiotic mode of action are based on detecting differential sensitivities of engineered bacterial strains in which the antibacterial target (usually encoded by an essential gene) or an associated process is regulated. We previously developed an essential-gene knockdown mutant library in the multidrug-resistant Burkholderia cenocepacia by transposon delivery of a rhamnose-inducible promoter. In this work, we used Illumina sequencing of multiplex-PCR-amplified transposon junctions to track individual mutants during pooled growth in the presence of antibiotics. We found that competition from nontarget mutants magnified the hypersensitivity of a clone underexpressing gyrB to novobiocin by 8-fold compared with hypersensitivity measured during clonal growth. Additional profiling of various antibiotics against a pilot library representing most categories of essential genes revealed a two-component system with unknown function, which, upon depletion of the response regulator, sensitized B. cenocepacia to novobiocin, ciprofloxacin, tetracycline, chloramphenicol, kanamycin, meropenem, and carbonyl cyanide 3-chlorophenylhydrazone, but not to colistin, hydrogen peroxide, and dimethyl sulfoxide. We named the gene cluster esaSR for enhanced sensitivity to antibiotics sensor and response regulator. Mutational analysis and efflux activity assays revealed that while esaS is not essential and is involved in antibiotic-induced efflux, esaR is an essential gene and regulates efflux independently of antibiotic-mediated induction. Furthermore, microscopic analysis of cells stained with propidium iodide provided evidence that depletion of EsaR has a profound effect on the integrity of cell membranes. In summary, we unraveled a previously uncharacterized two-component system that can be targeted to reduce antibiotic resistance in B. cenocepacia.

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 The Staphylococcus aureus KdpDE Two-Component System Couples Extracellular K+Sensing and Agr Signaling to Infection Programming

2011 ◽  
Vol 79 (6) ◽  
pp. 2154-2167 ◽  
Author(s):  
Ting Xue ◽  
Yibo You ◽  
De Hong ◽  
Haipeng Sun ◽  
Baolin Sun
Keyword(s):  
Staphylococcus Aureus ◽  
Uptake System ◽  
Main Function ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Virulence Regulator ◽  
External K

ABSTRACTThe Kdp system is widely distributed among bacteria. InEscherichia coli, the Kdp-ATPase is a high-affinity K+uptake system and its expression is activated by the KdpDE two-component system in response to K+limitation or salt stress. However, information about the role of this system in many bacteria still remains obscure. Here we demonstrate that KdpFABC inStaphylococcus aureusis not a major K+transporter and that the main function of KdpDE is not associated with K+transport but that instead it regulates transcription for a series of virulence factors through sensing external K+concentrations, indicating that this bacterium might modulate its infectious status through sensing specific external K+stimuli in different environments. Our results further reveal thatS. aureusKdpDE is upregulated by the Agr/RNAIII system, which suggests that KdpDE may be an important virulence regulator coordinating the external K+sensing and Agr signaling during pathogenesis in this bacterium.

scholarly journals The CasKR Two-Component System Is Required for the Growth of Mesophilic and Psychrotolerant Bacillus cereus Strains at Low Temperatures

2014 ◽  
Vol 80 (8) ◽  
pp. 2493-2503 ◽  
Author(s):  
Sara Esther Diomandé ◽  
Stéphanie Chamot ◽  
Vera Antolinos ◽  
Florian Vasai ◽  
Marie-Hélène Guinebretière ◽  
...  
Keyword(s):  
Bacillus Cereus ◽  
Food Poisoning ◽  
Two Component System ◽  
Diverse Range ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Temperature Ranges ◽  
Different Strains

ABSTRACTThe different strains ofBacillus cereuscan grow at temperatures covering a very diverse range. SomeB. cereusstrains can grow in chilled food and consequently cause food poisoning. We have identified a new sensor/regulator mechanism involved in low-temperatureB. cereusgrowth. Construction of a mutant of this two-component system enabled us to show that this system, called CasKR, is required for growth at the minimal temperature (Tmin). CasKR was also involved in optimal cold growth aboveTminand in cell survival belowTmin. Microscopic observation showed that CasKR plays a key role in cell shape during cold growth. Introducing thecasKRgenes in a ΔcasKRmutant restored its ability to grow atTmin. Although it was first identified in the ATCC 14579 model strain, this mechanism has been conserved in most strains of theB. cereusgroup. We show that the role of CasKR in cold growth is similar in otherB. cereus sensu latostrains with different growth temperature ranges, including psychrotolerant strains.

scholarly journals Identification of a Second Two-Component Signal Transduction System That Controls Fosfomycin Tolerance and Glycerol-3-Phosphate Uptake

2014 ◽  
Vol 197 (5) ◽  
pp. 861-871 ◽  
Author(s):  
Kumiko Kurabayashi ◽  
Yuko Hirakawa ◽  
Koichi Tanimoto ◽  
Haruyoshi Tomita ◽  
Hidetada Hirakawa
Keyword(s):  
Phosphate Uptake ◽  
Response Regulator ◽  
Anaerobic Respiration ◽  
Regulatory System ◽  
Carbon Substrate ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Biological Cost

Particular interest in fosfomycin has resurfaced because it is a highly beneficial antibiotic for the treatment of refractory infectious diseases caused by pathogens that are resistant to other commonly used antibiotics. The biological cost to cells of resistance to fosfomycin because of chromosomal mutation is high. We previously found that a bacterial two-component system, CpxAR, induces fosfomycin tolerance in enterohemorrhagicEscherichia coli(EHEC) O157:H7. This mechanism does not rely on irreversible genetic modification and allows EHEC to relieve the fitness burden that results from fosfomycin resistance in the absence of fosfomycin. Here we show that another two-component system, TorSRT, which was originally characterized as a regulatory system for anaerobic respiration utilizing trimethylamine-N-oxide (TMAO), also induces fosfomycin tolerance. Activation of the Tor regulatory pathway by overexpression oftorR, which encodes the response regulator, or addition of TMAO increased fosfomycin tolerance in EHEC. We also show that phosphorylated TorR directly represses the expression ofglpT, a gene that encodes a symporter of fosfomycin and glycerol-3-phosphate, and activation of the TorR protein results in the reduced uptake of fosfomycin by cells. However, cells in which the Tor pathway was activated had an impaired growth phenotype when cultured with glycerol-3-phosphate as a carbon substrate. These observations suggest that the TorSRT pathway is the second two-component system to reversibly control fosfomycin tolerance and glycerol-3-phosphate uptake in EHEC, and this may be beneficial for bacteria by alleviating the biological cost. We expect that this mechanism could be a potential target to enhance the utility of fosfomycin as chemotherapy against multidrug-resistant pathogens.

scholarly journals The PedS2/PedR2 Two-Component System Is Crucial for the Rare Earth Element Switch inPseudomonas putidaKT2440

mSphere ◽  
2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Matthias Wehrmann ◽  
Charlotte Berthelot ◽  
Patrick Billard ◽  
Janosch Klebensberger
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Response Regulator ◽  
Regulatory Function ◽  
Methylotrophic Bacteria ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Type Response

ABSTRACTInPseudomonas putidaKT2440, two pyrroloquinoline quinone-dependent ethanol dehydrogenases (PQQ-EDHs) are responsible for the periplasmic oxidation of a broad variety of volatile organic compounds (VOCs). Depending on the availability of rare earth elements (REEs) of the lanthanide series (Ln3+), we have recently reported that the transcription of the genes encoding the Ca2+-utilizing enzyme PedE and the Ln3+-utilizing enzyme PedH are inversely regulated. With adaptive evolution experiments, site-specific mutations, transcriptional reporter fusions, and complementation approaches, we now demonstrate that the PedS2/PedR2 (PP_2671/PP_2672) two-component system (TCS) plays a central role in the observed REE-mediated switch of PQQ-EDHs inP. putida. We provide evidence that in the absence of lanthanum (La3+), the sensor histidine kinase PedS2 phosphorylates its cognate LuxR-type response regulator PedR2, which in turn not only activatespedEgene transcription but is also involved in repression ofpedH. Our data further suggest that the presence of La3+lowers kinase activity of PedS2, either by the direct binding of the metal ions to the periplasmic region of PedS2 or by an uncharacterized indirect interaction, leading to reduced levels of phosphorylated PedR2. Consequently, the decreasingpedEexpression and concomitant alleviation ofpedHrepression causes—in conjunction with the transcriptional activation of thepedHgene by a yet unknown regulatory module—the Ln3+-dependent transition from PedE- to PedH-catalyzed oxidation of alcoholic VOCs.IMPORTANCEThe function of lanthanides for methanotrophic and methylotrophic bacteria is gaining increasing attention, while knowledge about the role of rare earth elements (REEs) in nonmethylotrophic bacteria is still limited. The present study investigates the recently described differential expression of the two PQQ-EDHs ofP. putidain response to lanthanides. We demonstrate that a specific TCS is crucial for their inverse regulation and provide evidence for a dual regulatory function of the LuxR-type response regulator involved. Thus, our study represents the first detailed characterization of the molecular mechanism underlying the REE switch of PQQ-EDHs in a nonmethylotrophic bacterium and stimulates subsequent investigations for the identification of additional genes or phenotypic traits that might be coregulated during REE-dependent niche adaptation.

scholarly journals The CtrA Regulon of Rhodobacter sphaeroides Favors Adaptation to a Particular Lifestyle

2020 ◽  
Vol 202 (7) ◽  
Author(s):  
José Hernández-Valle ◽  
Alejandro Sanchez-Flores ◽  
Sebastian Poggio ◽  
Georges Dreyfus ◽  
Laura Camarena
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Stress Responses ◽  
Transcriptome Sequencing ◽  
Growth Conditions ◽  
Fine Tuning ◽  
Rna Seq ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Two Component

ABSTRACT Activation of the two-component system formed by CckA, ChpT, and CtrA (kinase, phosphotransferase, and response regulator, respectively) in Rhodobacter sphaeroides does not occur under the growth conditions commonly used in the laboratory. However, it is possible to isolate a gain-of-function mutant in CckA that turns the system on. Using massive parallel transcriptome sequencing (RNA-seq), we identified 321 genes that are differentially regulated by CtrA. From these genes, 239 were positively controlled and 82 were negatively regulated. Genes encoding the Fla2 polar flagella and gas vesicle proteins are strongly activated by CtrA. Genes involved in stress responses as well as several transcriptional factors are also positively controlled, whereas the photosynthetic and CO2 fixation genes are repressed. Potential CtrA-binding sites were bioinformatically identified, leading to the proposal that at least 81 genes comprise the direct regulon. Based on our results, we ponder that the transcriptional response orchestrated by CtrA enables a lifestyle in which R. sphaeroides will effectively populate the surface layer of a water body enabled by gas vesicles and will remain responsive to chemotactic stimuli using the chemosensoring system that controls the Fla2 flagellum. Simultaneously, fine-tuning of photosynthesis and stress responses will reduce the damage caused by heat and high light intensity in this water stratum. In summary, in this bacterium CtrA has evolved to control physiological responses that allow its adaptation to a particular lifestyle instead of controlling the cell cycle as occurs in other species. IMPORTANCE Cell motility in Alphaproteobacteria is frequently controlled by the CckA, ChpT, and CtrA two-component system. Under the growth conditions commonly used in the laboratory, ctrA is transcriptionally inactive in Rhodobacter sphaeroides, and motility depends on the Fla1 flagellar system that was acquired by a horizontal transfer event. Likely, the incorporation of this flagellar system released CtrA from the strong selective pressure of being the main motility regulator, allowing this two-component system to specialize and respond to some specific conditions. Identifying the genes that are directly regulated by CtrA could help us understand the conditions in which the products of this regulon are required. Massive parallel transcriptome sequencing (RNA-seq) revealed that CtrA orchestrates an adaptive response that contributes to the colonization of a particular environmental niche.

scholarly journals A Two-Component System That Modulates Cyclic di-GMP Metabolism PromotesLegionella pneumophilaDifferentiation and Viability in Low-Nutrient Conditions

2019 ◽  
Vol 201 (17) ◽  
Author(s):  
Elisa D. Hughes ◽  
Brenda G. Byrne ◽  
Michele S. Swanson
Keyword(s):  
Life Cycle ◽  
Lifestyle Changes ◽  
Negative Regulator ◽  
Broth Culture ◽  
Cell Type ◽  
Two Component System ◽  
Term Survival ◽  
Component System ◽  
Content Type ◽  
Two Component

ABSTRACTDuring its life cycle, the environmental pathogenLegionella pneumophilaalternates between a replicative and transmissive cell type when cultured in broth, macrophages, or amoebae. Within a protozoan host,L. pneumophilafurther differentiates into the hardy cell type known as the mature infectious form (MIF). The second messenger cyclic di-GMP coordinates lifestyle changes in many bacterial species, but its role in theL. pneumophilalife cycle is less understood. Using anin vitrobroth culture model that approximates the intracellular transition from the replicative to the transmissive form, here we investigate the contribution toL. pneumophiladifferentiation of a two-component system (TCS) that regulates cyclic di-GMP metabolism. The TCS is encoded bylpg0278-lpg0277and is cotranscribed withlpg0279, which encodes a protein upregulated in MIF cells. The promoter for this operon is RpoS dependent and induced in nutrient-limiting conditions that do not support replication, as demonstrated using agfpreporter and quantitative PCR (qPCR). The response regulator of the TCS (Lpg0277) is a bifunctional enzyme that both synthesizes and degrades cyclic di-GMP. Using a panel of site-directed point mutants, we show that cyclic di-GMP synthesis mediated by a conserved GGDEF domain promotes growth arrest of replicativeL. pneumophila, accumulation of pigment and poly-3-hydroxybutyrate storage granules, and viability in nutrient-limiting conditions. Genetic epistasis tests predict that the MIF protein Lpg0279 acts as a negative regulator of the TCS. Thus,L. pneumophilais equipped with a regulatory network in which cyclic di-GMP stimulates the switch from a replicative to a resilient state equipped to survive in low-nutrient environments.IMPORTANCEAlthough an intracellular pathogen,L. pneumophilahas developed mechanisms to ensure long-term survival in low-nutrient aqueous conditions. Eradication ofL. pneumophilafrom contaminated water supplies has proven challenging, as outbreaks have been traced to previously remediated systems. Understanding the genetic determinants that supportL. pneumophilapersistence in low-nutrient environments can inform design and assessment of remediation strategies. Here we characterize a genetic locus that encodes a two-component signaling system (lpg0278-lpg0277) and a putative regulator protein (lpg0279) that modulates the production of the messenger molecule cyclic di-GMP. We show that this locus promotes bothL. pneumophilacell differentiation and survival in nutrient-limiting conditions, thus advancing the understanding of the mechanisms that contribute toL. pneumophilaenvironmental resilience.

scholarly journals The Ferrous Iron-Responsive BqsRS Two-Component System Activates Genes That Promote Cationic Stress Tolerance

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Naomi N. Kreamer ◽  
Flavia Costa ◽  
Dianne K. Newman
Keyword(s):  
Ferrous Iron ◽  
Cellular Response ◽  
Antimicrobial Agents ◽  
Chronic Infections ◽  
Two Component System ◽  
Severe Problem ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Physiological Resistance

ABSTRACTThe physiological resistance of pathogens to antimicrobial treatment is a severe problem in the context of chronic infections. For example, the mucus-filled lungs of cystic fibrosis (CF) patients are readily colonized by diverse antibiotic-resistant microorganisms, includingPseudomonas aeruginosa. Previously, we showed that bioavailable ferrous iron [Fe(II)] is present in CF sputum at all stages of infection and constitutes a significant portion of the iron pool at advanced stages of lung function decline [R. C. Hunter et al., mBio 4(4):e00557-13, 2013].P. aeruginosa, a dominant CF pathogen, senses Fe(II) using a two-component signal transduction system, BqsRS, which is transcriptionally active in CF sputum [R. C. Hunter et al., mBio 4(4):e00557-13, 2013; N. N. Kreamer, J. C. Wilks, J. J. Marlow, M. L. Coleman, and D. K. Newman, J Bacteriol 194:1195–1204, 2012]. Here, we show that an RExxE motif in BqsS is required for BqsRS activation. Once Fe(II) is sensed, BqsR binds a tandem repeat DNA sequence, activating transcription. The BqsR regulon—defined through iterative bioinformatic predictions and experimental validation—includes several genes whose products are known to drive antibiotic resistance to aminoglycosides and polymyxins. Among them are genes encoding predicted determinants of polyamine transport and biosynthesis. Compared to the wild type,bqsSandbqsRdeletion mutants are sensitive to high levels of Fe(II), produce less spermidine in high Fe(II), and are more sensitive to tobramycin and polymyxin B but not arsenate, chromate, or cefsulodin. BqsRS thus mediates a physiological response to Fe(II) that guards the cell against positively charged molecules but not negatively charged stressors. These results suggest Fe(II) is an important environmental signal that, via BqsRS, bolsters tolerance of a variety of cationic stressors, including clinically important antimicrobial agents.IMPORTANCEClearing chronic infections is challenging due to the physiological resistance of opportunistic pathogens to antibiotics. Effective treatments are hindered by a lack of understanding of how these organisms survivein situ. Fe(II) is typically present at micromolar levels in soils and sedimentary habitats, as well as in CF sputum. All P. aeruginosa strains possess a two-component system, BqsRS, that specifically senses extracellular Fe(II) at low micromolar concentrations. Our work shows that BqsRS protects the cell against cationic perturbations to the cell envelope as well as low pH and reduction potential (Eh), conditions under which Fe2+is stable. Fe(II) can thus be understood as a proxy for a broader environmental state; the cellular response to its detection may help rationalize the resistance of P. aeruginosa to clinically important cationic antibiotics. This finding demonstrates the importance of considering environmental chemistry when exploring mechanisms of microbial survival in habitats that include the human body.

scholarly journals Disruption of Glycolysis by Nutritional Immunity Activates a Two-Component System That Coordinates a Metabolic and Antihost Response by Staphylococcus aureus

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Paola K. Párraga Solórzano ◽  
Jiangwei Yao ◽  
Charles O. Rock ◽  
Thomas E. Kehl-Fie
Keyword(s):  
Staphylococcus Aureus ◽  
Metabolic Flux ◽  
Bacterial Species ◽  
Critical Role ◽  
Dependent Manner ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Nutritional Immunity ◽  
Two Component

ABSTRACT During infection, bacteria use two-component signal transduction systems to sense and adapt to the dynamic host environment. Despite critically contributing to infection, the activating signals of most of these regulators remain unknown. This also applies to the Staphylococcus aureus ArlRS two-component system, which contributes to virulence by coordinating the production of toxins, adhesins, and a metabolic response that enables the bacterium to overcome host-imposed manganese starvation. Restricting the availability of essential transition metals, a strategy known as nutritional immunity, constitutes a critical defense against infection. In this work, expression analysis revealed that manganese starvation imposed by the immune effector calprotectin or by the absence of glycolytic substrates activates ArlRS. Manganese starvation imposed by calprotectin also activated the ArlRS system even when glycolytic substrates were present. A combination of metabolomics, mutational analysis, and metabolic feeding experiments revealed that ArlRS is activated by alterations in metabolic flux occurring in the latter half of the glycolytic pathway. Moreover, calprotectin was found to induce expression of staphylococcal leukocidins in an ArlRS-dependent manner. These studies indicated that ArlRS is a metabolic sensor that allows S. aureus to integrate multiple environmental stresses that alter glycolytic flux to coordinate an antihost response and to adapt to manganese starvation. They also established that the latter half of glycolysis represents a checkpoint to monitor metabolic state in S. aureus. Altogether, these findings contribute to understanding how invading pathogens, such as S. aureus, adapt to the host during infection and suggest the existence of similar mechanisms in other bacterial species. IMPORTANCE Two-component regulatory systems enable bacteria to adapt to changes in their environment during infection by altering gene expression and coordinating antihost responses. Despite the critical role of two-component systems in bacterial survival and pathogenesis, the activating signals for most of these regulators remain unidentified. This is exemplified by ArlRS, a Staphylococcus aureus global regulator that contributes to virulence and to resisting host-mediated restriction of essential nutrients, such as manganese. In this report, we demonstrate that manganese starvation and the absence of glycolytic substrates activate ArlRS. Further investigations revealed that ArlRS is activated when the latter half of glycolysis is disrupted, suggesting that S. aureus monitors flux through the second half of this pathway. Host-imposed manganese starvation also induced the expression of pore-forming toxins in an ArlRS-dependent manner. Cumulatively, this work reveals that ArlRS acts as a sensor that links nutritional status, cellular metabolism, and virulence regulation.

scholarly journals CrdS and CrdA Comprise a Two-Component System That Is Cooperatively Regulated by the Che3 Chemosensory System in Myxococcus xanthus

mBio ◽  
2011 ◽  
Vol 2 (4) ◽  
Author(s):  
Jonathan W. Willett ◽  
John R. Kirby
Keyword(s):  
Signal Transduction ◽  
Myxococcus Xanthus ◽  
Complex Signal ◽  
Central Processor ◽  
Two Component System ◽  
Component System ◽  
Chemosensory System ◽  
Content Type ◽  
Phosphorylation State ◽  
Two Component

ABSTRACTMyxococcus xanthusserves as a model organism for development and complex signal transduction. Regulation of developmental aggregation and sporulation is controlled, in part, by the Che3 chemosensory system. The Che3 pathway consists of homologs to two methyl-accepting chemotaxis proteins (MCPs), CheA, CheW, CheB, and CheR but not CheY. Instead, the output for Che3 is the NtrC homolog CrdA, which functions to regulate developmental gene expression. In this paper we have identified an additional kinase, CrdS, which directly regulates the phosphorylation state of CrdA. Both epistasis andin vitrophosphotransfer assays indicate that CrdS functions as part of the Che3 pathway and, in addition to CheA3, serves to regulate CrdA phosphorylation inM. xanthus. We provide kinetic data for CrdS autophosphorylation and demonstrate specificity for phosphotransfer from CrdS to CrdA. We further demonstrate that CheA3 destabilizes phosphorylated CrdA (CrdA~P), indicating that CheA3 likely acts as a phosphatase. Both CrdS and CheA3 control developmental progression by regulating the phosphorylation state of CrdA~P in the cell. These results support a model in which a classical two-component system and a chemosensory system act synergistically to control the activity of the response regulator CrdA.IMPORTANCEWhile phosphorylation-mediated signal transduction is well understood in prototypical chemotaxis and two-component systems (TCS), chemosensory regulation of alternative cellular functions (ACF) has not been clearly defined. The Che3 system inMyxococcus xanthusis a member of the ACF class of chemosensory systems and regulates development via the transcription factor CrdA (chemosensoryregulator ofdevelopment) (K. Wuichet and I. B. Zhulin, Sci. Signal. 3:ra50, 2010; J. R. Kirby and D. R. Zusman, Proc. Natl. Acad. Sci. U. S. A. 100:2008–2013, 2003). We have identified and characterized a homolog of NtrB, designated CrdS, capable of specifically phosphorylating the NtrC homolog CrdA inM. xanthus. Additionally, we demonstrate that the CrdSA two-component system is negatively regulated by CheA3, the central processor within the Che3 system ofM. xanthus. To our knowledge, this study provides the first example of an ACF chemosensory system regulating a prototypical two-component system and extends our understanding of complex regulation of developmental signaling pathways.

Sign in / Sign up

Export Citation Format

Share Document