scholarly journals Effects of Regulatory Network Organization and Environment on PmrD Connector Activity and Polymyxin Resistance in Klebsiella pneumoniae and Escherichia coli

2020 ◽  
Vol 65 (3) ◽  
Author(s):  
Annie I. Chen ◽  
Francisco Javier Albicoro ◽  
Jun Zhu ◽  
Mark Goulian
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Critical Role ◽  
Negative Regulator ◽  
Network Organization ◽  
Content Type ◽  
Resistance Pathway ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems

ABSTRACT Polymyxins are a class of cyclic peptides with antimicrobial activity against Gram-negative bacteria. In Enterobacteriaceae, the PhoQ/PhoP and PmrB/PmrA two-component systems regulate many genes that confer resistance to both polymyxins and host antimicrobial peptides. The activities of these two-component systems are modulated by additional proteins that are conserved across Enterobacteriaceae, such as MgrB, a negative regulator of PhoQ, and PmrD, a “connector” protein that activates PmrB/PmrA in response to PhoQ/PhoP stimulation. Despite the conservation of many protein components of the PhoQ/PhoP-PmrD-PmrB/PmrA network, the specific molecular interactions and regulatory mechanisms vary across different genera. Here, we explore the role of PmrD in modulating this signaling network in Klebsiella pneumoniae and Escherichia coli. We show that in K. pneumoniae, PmrD is not required for polymyxin resistance arising from mutation of mgrB—the most common cause of spontaneous polymyxin resistance in this bacterium—suggesting that direct activation of polymyxin resistance genes by PhoQ/PhoP plays a critical role in this resistance pathway. However, for conditions of low pH or intermediate iron concentrations, both of which stimulate PmrB/PmrA, we find that PmrD does contribute to resistance. We further show that in E. coli, PmrD functions as a connector between PhoQ/PhoP and PmrB/PmrA, in contrast with previous reports. In this case, activity also depends on PmrB/PmrA stimulation, or on very high activation of PhoQ/PhoP. Our results indicate that the importance of the PmrD connector in modulating the polymyxin resistance network depends on both the network organization and on the environmental conditions associated with PmrB stimulation.

scholarly journals Elucidation of Regulatory Modes for Five Two-Component Systems in Escherichia coli Reveals Novel Relationships

mSystems ◽  
2020 ◽  
Vol 5 (6) ◽  
Author(s):  
Kumari Sonal Choudhary ◽  
Julia A. Kleinmanns ◽  
Katherine Decker ◽  
Anand V. Sastry ◽  
Ye Gao ◽  
...  
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Target Gene ◽  
Target Genes ◽  
Rna Seq ◽  
Content Type ◽  
E Coli ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems

ABSTRACT Escherichia coli uses two-component systems (TCSs) to respond to environmental signals. TCSs affect gene expression and are parts of E. coli’s global transcriptional regulatory network (TRN). Here, we identified the regulons of five TCSs in E. coli MG1655: BaeSR and CpxAR, which were stimulated by ethanol stress; KdpDE and PhoRB, induced by limiting potassium and phosphate, respectively; and ZraSR, stimulated by zinc. We analyzed RNA-seq data using independent component analysis (ICA). ChIP-exo data were used to validate condition-specific target gene binding sites. Based on these data, we do the following: (i) identify the target genes for each TCS; (ii) show how the target genes are transcribed in response to stimulus; and (iii) reveal novel relationships between TCSs, which indicate noncognate inducers for various response regulators, such as BaeR to iron starvation, CpxR to phosphate limitation, and PhoB and ZraR to cell envelope stress. Our understanding of the TRN in E. coli is thus notably expanded. IMPORTANCE E. coli is a common commensal microbe found in the human gut microenvironment; however, some strains cause diseases like diarrhea, urinary tract infections, and meningitis. E. coli’s two-component systems (TCSs) modulate target gene expression, especially related to virulence, pathogenesis, and antimicrobial peptides, in response to environmental stimuli. Thus, it is of utmost importance to understand the transcriptional regulation of TCSs to infer bacterial environmental adaptation and disease pathogenicity. Utilizing a combinatorial approach integrating RNA sequencing (RNA-seq), independent component analysis, chromatin immunoprecipitation coupled with exonuclease treatment (ChIP-exo), and data mining, we suggest five different modes of TCS transcriptional regulation. Our data further highlight noncognate inducers of TCSs, which emphasizes the cross-regulatory nature of TCSs in E. coli and suggests that TCSs may have a role beyond their cognate functionalities. In summary, these results can lead to an understanding of the metabolic capabilities of bacteria and correctly predict complex phenotype under diverse conditions, especially when further incorporated with genome-scale metabolic models.

scholarly journals The Histidine Residue of QseC Is Required for Canonical Signaling between QseB and PmrB in Uropathogenic Escherichia coli

2017 ◽  
Vol 199 (18) ◽  
Author(s):  
Erin J. Breland ◽  
Ellisa W. Zhang ◽  
Tomas Bermudez ◽  
Charles R. Martinez ◽  
Maria Hadjifrangiskou
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Polymyxin B ◽  
Sensor Kinase ◽  
Histidine Residue ◽  
Content Type ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems ◽  
Tract Infections

ABSTRACT Two-component systems are prototypically comprised of a histidine kinase (sensor) and a response regulator (responder). The sensor kinases autophosphorylate at a conserved histidine residue, acting as a phosphodonor for subsequent phosphotransfer to and activation of a cognate response regulator. In rare cases, the histidine residue is also essential for response regulator dephosphorylation via a reverse-phosphotransfer reaction. In this work, we present an example of a kinase that relies on reverse phosphotransfer to catalyze the dephosphorylation of its cognate partner. The QseC sensor kinase is conserved across several Gram-negative pathogens; its interaction with its cognate partner QseB is critical for maintaining pathogenic potential. Here, we demonstrate that QseC-mediated dephosphorylation of QseB occurs via reverse phosphotransfer. In previous studies, we demonstrated that, in uropathogenic Escherichia coli, exposure to high concentrations of ferric iron (Fe3+) stimulates the PmrB sensor kinase. This stimulation, in turn, activates the cognate partner, PmrA, and noncognate QseB to enhance tolerance to polymyxin B. We demonstrate that in the absence of signal, kinase-inactive QseC variants, in which the H246 residue was changed to alanine (A) aspartate (D) or leucine (L), rescued a ΔqseC deletion mutant, suggesting that QseC can control QseB activation via a mechanism that is independent of reverse phosphotransfer. However, in the presence of Fe3+, the same QseC variants were unable to mediate a wild-type stimulus response, indicating that QseC-mediated dephosphorylation is required for maintaining proper QseB-PmrB-PmrA interactions. IMPORTANCE Two-component signaling networks constitute one of the predominant methods by which bacteria sense and respond to their changing environments. Two-component systems allow bacteria to thrive and survive in a number of different environments, including within a human host. Uropathogenic Escherichia coli, the causative agent of urinary tract infections, rely on two interacting two-component systems, QseBC and PmrAB, to induce intrinsic resistance to the colistin antibiotic polymyxin B, which is a last line of defense drug. The presence of one sensor kinase, QseC, is required to regulate the interaction between the other sensor kinase, PmrB and the response regulators from both systems, QseB and PmrA, effectively creating a “four-component” system required for virulence. Understanding the important role of the sensor kinase QseC will provide insight into additional ways to therapeutically target uropathogens that harbor these signaling systems.

scholarly journals B1500, a small membrane protein, connects the two-component systems EvgS/EvgA and PhoQ/PhoP in Escherichia coli

2007 ◽  
Vol 104 (47) ◽  
pp. 18712-18717 ◽  
Author(s):  
Y. Eguchi ◽  
J. Itou ◽  
M. Yamane ◽  
R. Demizu ◽  
F. Yamato ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Protein ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems

scholarly journals The ChrSA and HrrSA Two-Component Systems Are Required for Transcriptional Regulation of thehemAPromoter in Corynebacterium diphtheriae

2016 ◽  
Vol 198 (18) ◽  
pp. 2419-2430 ◽  
Author(s):  
Jonathan M. Burgos ◽  
Michael P. Schmitt
Keyword(s):  
Signal Transduction ◽  
Kinase Activity ◽  
Content Type ◽  
Component Systems ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Two Component Systems ◽  
Signal Transduction Systems

ABSTRACTCorynebacterium diphtheriaeutilizes heme and hemoglobin (Hb) as iron sources for growth in low-iron environments. InC. diphtheriae, the two-component signal transduction systems (TCSs) ChrSA and HrrSA are responsive to Hb levels and regulate the transcription of promoters forhmuO,hrtAB, andhemA. ChrSA and HrrSA activate transcription at thehmuOpromoter and repress transcription athemAin an Hb-dependent manner. In this study, we show that HrrSA is the predominant repressor athemAand that its activity results in transcriptional repression in the presence and absence of Hb, whereas repression ofhemAby ChrSA is primarily responsive to Hb. DNA binding studies showed that both ChrA and HrrA bind to thehemApromoter region at virtually identical sequences. ChrA binding was enhanced by phosphorylation, while binding to DNA by HrrA was independent of its phosphorylation state. ChrA and HrrA are phosphorylatedin vitroby the sensor kinase ChrS, whereas no kinase activity was observed with HrrSin vitro. Phosphorylated ChrA was not observedin vivo, even in the presence of Hb, which is likely due to the instability of the phosphate moiety on ChrA. However, phosphorylation of HrrA was observedin vivoregardless of the presence of the Hb inducer, and genetic analysis indicates that ChrS is responsible for most of the phosphorylation of HrrAin vivo. Phosphorylation studies strongly suggest that HrrS functions primarily as a phosphatase and has only minimal kinase activity. These findings collectively show a complex mechanism of regulation at thehemApromoter, where both two-component systems act in concert to optimize expression of heme biosynthetic enzymes.IMPORTANCEUnderstanding the mechanism by which two-component signal transduction systems function to respond to environmental stimuli is critical to the study of bacterial pathogenesis. The current study expands on the previous analyses of the ChrSA and HrrSA TCSs in the human pathogenC. diphtheriae. The findings here underscore the complex interactions between the ChrSA and HrrSA systems in the regulation of thehemApromoter and demonstrate how the two systems complement one another to refine and control transcription in the presence and absence of Hb.

Age replacement policies for two-component systems with stochastic dependence

2015 ◽  
Vol 21 (3) ◽  
pp. 346-357 ◽  
Author(s):  
Zouheir Malki ◽  
Daoud Ait-Kadi ◽  
Mohamed-Salah Ouali
Keyword(s):  
Random Variable ◽  
Replacement Policy ◽  
Replacement Cost ◽  
Stochastic Dependence ◽  
Content Type ◽  
Preventive Replacement ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems ◽  
Age Replacement

Purpose – The purpose of this paper is to investigate age replacement policies for two-component parallel system with stochastic dependence. The stochastic dependence considered, is modeled by a one-sided domino effect. The failure of component 1 at instant t may induce the failure of component 2 at instant t+τ with probability p 1→2. The time delay τ is a random variable with known probability density function h p 1→2 (.). The system is considered in a failed state when both components are failed. The proposed replacement policies suggest to replace the system upon failure or at age T whichever occurs first. Design/methodology/approach – In the first policy, costs and durations associated with maintenance activities are supposed to be constant. In the second replacement policy, the preventive replacement cost depends on the system’s state and age. The expected cost per unit of time over an infinite span is derived and numerical examples are presented. Findings – In this paper and especially in the second policy, the authors find that the authors can get a more economical policy if the authors consider that the preventive replacement cost is not constant but depends on T. Originality/value – In this paper, the authors take into account of the stochastic dependence between system components. This dependence affects the global reliability of the system and replacement’s periodicity. It can be used to measure the performance of the system et introduced into design phase of the system.

scholarly journals Menaquinone Analogs Inhibit Growth of Bacterial Pathogens

2013 ◽  
Vol 57 (11) ◽  
pp. 5432-5437 ◽  
Author(s):  
Patrick M. Schlievert ◽  
Joseph A. Merriman ◽  
Wilmara Salgado-Pabón ◽  
Elizabeth A. Mueller ◽  
Adam R. Spaulding ◽  
...  
Keyword(s):  
Plasma Membranes ◽  
Rabbit Model ◽  
Two Component System ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Component Systems ◽  
Two Component ◽  
Topical Antibacterial ◽  
Two Component Systems ◽  
Antibacterial Target

ABSTRACTGram-positive bacteria cause serious human illnesses through combinations of cell surface and secreted virulence factors. We initiated studies with four of these organisms to develop novel topical antibacterial agents that interfere with growth and exotoxin production, focusing on menaquinone analogs. Menadione, 1,4-naphthoquinone, and coenzymes Q1 to Q3 but not menaquinone, phylloquinone, or coenzyme Q10 inhibited the growth and to a greater extent exotoxin production ofStaphylococcus aureus,Bacillus anthracis,Streptococcus pyogenes, andStreptococcus agalactiaeat concentrations of 10 to 200 μg/ml. Coenzyme Q1 reduced the ability ofS. aureusto cause toxic shock syndrome in a rabbit model, inhibited the growth of four Gram-negative bacteria, and synergized with another antimicrobial agent, glycerol monolaurate, to inhibitS. aureusgrowth. The staphylococcal two-component system SrrA/B was shown to be an antibacterial target of coenzyme Q1. We hypothesize that menaquinone analogs both induce toxic reactive oxygen species and affect bacterial plasma membranes and biosynthetic machinery to interfere with two-component systems, respiration, and macromolecular synthesis. These compounds represent a novel class of potential topical therapeutic agents.

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