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Pi H, Burroughs OS, Carlin SM, Beavers WN, Hillebrand GH, Krystofiak ES, Stauff DL, Skaar EP. FapR regulates HssRS-mediated heme homeostasis in Bacillus anthracis. mBio 2025:e0205724. [PMID: 40407322 DOI: 10.1128/mbio.02057-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2024] [Accepted: 04/28/2025] [Indexed: 05/28/2025] Open
Abstract
Bacillus anthracis, a Gram-positive facultative anaerobe and the causative agent of anthrax, multiplies to extraordinarily high numbers in vertebrate blood, resulting in considerable heme exposure. Heme is an essential nutrient and the preferred iron source for bacteria during vertebrate colonization, but its high redox potential makes it toxic in excess. To regulate heme homeostasis, many Gram-positive bacteria, including B. anthracis, rely on the two-component signaling system HssRS. HssRS comprises the heme sensing histidine kinase HssS, which modulates the activity of the HssR transcription factor to enable bacteria to circumvent heme toxicity. However, the regulation of the HssRS system remains unclear. Here, we identify FapR, the transcriptional regulator of fatty acid biosynthesis, as a key factor in HssRS function. FapR plays an important role in maintaining membrane integrity and the localization of the histidine kinase HssS. Specifically, disruption of fapR leads to increased membrane rigidity, which hinders the penetration of HssRS inducers, resulting in the inactivation of HssRS. Furthermore, deletion of fapR affects the loading of HssS onto the cell membrane, compromising its heme sensing function and subsequently reducing endogenous heme biosynthesis. These findings shed light on the molecular mechanisms governing bacterial adaptation to heme stress and provide potential targets for antimicrobial intervention strategies. IMPORTANCE Understanding the mechanisms by which B. anthracis regulates heme homeostasis is crucial for developing new strategies to combat anthrax, a serious disease affecting both humans and animals. This study uncovers the role of the transcriptional regulator FapR in maintaining membrane integrity and facilitating the proper function of the HssRS two-component signaling system, which is essential for managing heme toxicity in B. anthracis, as well as other Gram-positive pathogens. By elucidating the connection between FapR and HssRS, our findings provide new insights into the molecular adaptation of bacteria to heme stress and expand our knowledge of bacterial physiology and pathogenicity. More importantly, targeting the regulatory pathways involved in heme sensing and homeostasis presents a promising approach for developing novel therapeutics against anthrax and potentially other bacterial infections that rely on similar mechanisms.
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Affiliation(s)
- Hualiang Pi
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, Tennessee, USA
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Owen S Burroughs
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, Tennessee, USA
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Sophia M Carlin
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, Tennessee, USA
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - William N Beavers
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, Tennessee, USA
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | | | - Evan S Krystofiak
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Devin L Stauff
- Department of Biology, Grove City College, Grove City, Pennsylvania, USA
| | - Eric P Skaar
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, Tennessee, USA
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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2
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Pi H, Carlin SM, Beavers WN, Hillebrand GH, Krystofiak ES, Stauff DL, Skaar EP. FapR regulates HssRS-mediated heme homeostasis in Bacillus anthracis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.08.602573. [PMID: 39026866 PMCID: PMC11257595 DOI: 10.1101/2024.07.08.602573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Bacillus anthracis, a Gram-positive facultative anaerobe and the causative agent of anthrax, multiplies to extraordinarily high numbers in vertebrate blood, resulting in considerable heme exposure. Heme is an essential nutrient and the preferred iron source for bacteria during vertebrate colonization, but its high redox potential makes it toxic in excess. To regulate heme homeostasis, many Gram-positive bacteria, including B. anthracis, rely on the two-component signaling system HssRS. HssRS comprises the heme sensing histidine kinase HssS, which modulates the activity of the HssR transcription factor to enable bacteria to circumvent heme toxicity. However, the regulation of the HssRS system remains unclear. Here we identify FapR, the transcriptional regulator of fatty acid biosynthesis, as a key factor in HssRS function. FapR plays an important role in maintaining membrane integrity and the localization of the histidine kinase HssS. Specifically, disruption of fapR leads to increased membrane rigidity, which hinders the penetration of HssRS inducers, resulting in the inactivation of HssRS. Furthermore, deletion of fapR affects the loading of HssS onto the cell membrane, compromising its heme sensing function and subsequently reducing endogenous heme biosynthesis. These findings shed light on the molecular mechanisms governing bacterial adaptation to heme stress and provide potential targets for antimicrobial intervention strategies.
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Affiliation(s)
- Hualiang Pi
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, TN
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, TN
- Current address: Department of Microbial Pathogenesis and Microbial Sciences Institute, Yale University School of Medicine, New Haven, CT
| | - Sophia M. Carlin
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, TN
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, TN
| | - William N. Beavers
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, TN
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, TN
| | | | - Evan S. Krystofiak
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN
| | | | - Eric P. Skaar
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University, Nashville, TN
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, TN
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3
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Ahator SD, Wenzl K, Hegstad K, Lentz CS, Johannessen M. Comprehensive virulence profiling and evolutionary analysis of specificity determinants in Staphylococcus aureus two-component systems. mSystems 2024; 9:e0013024. [PMID: 38470253 PMCID: PMC11019936 DOI: 10.1128/msystems.00130-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Accepted: 02/15/2024] [Indexed: 03/13/2024] Open
Abstract
In the Staphylococcus aureus genome, a set of highly conserved two-component systems (TCSs) composed of histidine kinases (HKs) and their cognate response regulators (RRs) sense and respond to environmental stimuli, which drive the adaptation of the bacteria. This study investigates the complex interplay between TCSs in S. aureus USA300, a predominant methicillin-resistant S. aureus strain, revealing shared and unique virulence regulatory pathways and genetic variations mediating signal specificity within TCSs. Using TCS-related mutants from the Nebraska Transposon Mutant Library, we analyzed the effects of inactivated TCS HKs and RRs on the production of various virulence factors, in vitro infection abilities, and adhesion assays. We found that the TCSs' influence on virulence determinants was not associated with their phylogenetic relationship, indicating divergent functional evolution. Using the co-crystallized structure of the DesK-DesR from Bacillus subtilis and the modeled structures of the four NarL TCSs in S. aureus, we identified interacting residues, revealing specificity determinants and conservation within the same TCS, even from different strain backgrounds. The interacting residues were highly conserved within strains but varied between species due to selection pressures and the coevolution of cognate pairs. This study unveils the complex interplay and divergent functional evolution of TCSs, highlighting their potential for future experimental exploration of phosphotransfer between cognate and non-cognate recombinant HK and RRs.IMPORTANCEGiven the widespread conservation of two-component systems (TCSs) in bacteria and their pivotal role in regulating metabolic and virulence pathways, they present a compelling target for anti-microbial agents, especially in the face of rising multi-drug-resistant infections. Harnessing TCSs therapeutically necessitates a profound understanding of their evolutionary trajectory in signal transduction, as this underlies their unique or shared virulence regulatory pathways. Such insights are critical for effectively targeting TCS components, ensuring an optimized impact on bacterial virulence, and mitigating the risk of resistance emergence via the evolution of alternative pathways. Our research offers an in-depth exploration of virulence determinants controlled by TCSs in S. aureus, shedding light on the evolving specificity determinants that orchestrate interactions between their cognate pairs.
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Affiliation(s)
- Stephen Dela Ahator
- Research Group for Host-Microbe Interactions, Centre for New Antibacterial Strategies (CANS), Department of Medical Biology, Faculty of Health Sciences, UiT- The Arctic University of Norway, Tromsø, Norway
| | - Karoline Wenzl
- Research Group for Host-Microbe Interactions, Centre for New Antibacterial Strategies (CANS), Department of Medical Biology, Faculty of Health Sciences, UiT- The Arctic University of Norway, Tromsø, Norway
| | - Kristin Hegstad
- Research Group for Host-Microbe Interactions, Centre for New Antibacterial Strategies (CANS), Department of Medical Biology, Faculty of Health Sciences, UiT- The Arctic University of Norway, Tromsø, Norway
- Norwegian National Advisory Unit on Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North Norway, Tromsø, Norway
| | - Christian S. Lentz
- Research Group for Host-Microbe Interactions, Centre for New Antibacterial Strategies (CANS), Department of Medical Biology, Faculty of Health Sciences, UiT- The Arctic University of Norway, Tromsø, Norway
| | - Mona Johannessen
- Research Group for Host-Microbe Interactions, Centre for New Antibacterial Strategies (CANS), Department of Medical Biology, Faculty of Health Sciences, UiT- The Arctic University of Norway, Tromsø, Norway
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Wang Z, Wang H, Bai J, Cai S, Qu D, Xie Y, Wu Y. The Staphylococcus aureus ArlS Kinase Inhibitor Tilmicosin Has Potent Anti-Biofilm Activity in Both Static and Flow Conditions. Microorganisms 2024; 12:256. [PMID: 38399660 PMCID: PMC10891534 DOI: 10.3390/microorganisms12020256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 01/17/2024] [Accepted: 01/24/2024] [Indexed: 02/25/2024] Open
Abstract
Staphylococcus aureus can form biofilms on biotic surfaces or implanted materials, leading to biofilm-associated diseases in humans and animals that are refractory to conventional antibiotic treatment. Recent studies indicate that the unique ArlRS regulatory system in S. aureus is a promising target for screening inhibitors that may eradicate formed biofilms, retard virulence and break antimicrobial resistance. In this study, by screening in the library of FDA-approved drugs, tilmicosin was found to inhibit ArlS histidine kinase activity (IC50 = 1.09 μM). By constructing a promoter-fluorescence reporter system, we found that tilmicosin at a concentration of 0.75 μM or 1.5 μM displayed strong inhibition on the expression of the ArlRS regulon genes spx and mgrA in the S. aureus USA300 strain. Microplate assay and confocal laser scanning microscopy showed that tilmicosin at a sub-minimal inhibitory concentration (MIC) had a potent inhibitory effect on biofilms formed by multiple S. aureus strains and a strong biofilm-forming strain of S. epidermidis. In addition, tilmicosin at three-fold of MIC disrupted USA300 mature biofilms and had a strong bactericidal effect on embedded bacteria. Furthermore, in a BioFlux flow biofilm assay, tilmicosin showed potent anti-biofilm activity and synergized with oxacillin against USA300.
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Affiliation(s)
| | | | | | | | | | - Youhua Xie
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China (S.C.)
| | - Yang Wu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China (S.C.)
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Kato F, Yamaguchi Y, Inouye K, Matsuo K, Ishida Y, Inouye M. A novel gyrase inhibitor from toxin-antitoxin system expressed by Staphylococcus aureus. FEBS J 2023; 290:1502-1518. [PMID: 36148483 DOI: 10.1111/febs.16634] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 09/12/2022] [Accepted: 09/22/2022] [Indexed: 11/30/2022]
Abstract
Toxin-antitoxin (TA) systems consist of a toxin inhibiting essential cellular functions (such as DNA, RNA and protein synthesis), and its cognate antitoxin neutralizing the toxicity. Recently, we identified a TA system termed TsbA/TsbT in the Staphylococcus aureus genome. The induction of the tsbT gene in Escherichia coli halted both DNA and RNA synthesis, reduced supercoiled plasmid and resulted in increasingly relaxed DNA. These results suggested that DNA gyrase was the target of TsbT. In addition, TsbT inhibited both E. coli and S. aureus DNA gyrase activity and induced linearization of plasmid DNA in vitro. Taken together, these results demonstrate that the TsbT toxin targets DNA gyrase in vivo. Site-directed mutagenesis experiments showed that the E27 and D37 residues in TsbT are critical for toxicity. Secondary structure prediction combining the analysis of vacuum-ultraviolet circular-dichroism spectroscopy and neural network method demonstrated that the 22nd-32nd residues of TsbT form an α-helix structure, and that the E27 residue is located around the centre of the α-helix segment. These findings give new insights not only into S. aureus TA systems, but also into bacterial toxins targeting DNA topoisomerases.
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Affiliation(s)
- Fuminori Kato
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan
| | - Yoshihiro Yamaguchi
- Department of Biology and Geosciences, Graduate School of Sciences, Osaka City University, Japan
| | - Keiko Inouye
- Department of Biochemistry and Molecular Biology, Center for Advanced Biotechnology and Medicine, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ, USA
| | - Koichi Matsuo
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Japan
| | - Yojiro Ishida
- Department of Biochemistry and Molecular Biology, Center for Advanced Biotechnology and Medicine, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ, USA
| | - Masayori Inouye
- Department of Biochemistry and Molecular Biology, Center for Advanced Biotechnology and Medicine, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ, USA
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Bleul L, Francois P, Wolz C. Two-Component Systems of S. aureus: Signaling and Sensing Mechanisms. Genes (Basel) 2021; 13:34. [PMID: 35052374 PMCID: PMC8774646 DOI: 10.3390/genes13010034] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 12/21/2021] [Accepted: 12/22/2021] [Indexed: 12/18/2022] Open
Abstract
Staphylococcus aureus encodes 16 two-component systems (TCSs) that enable the bacteria to sense and respond to changing environmental conditions. Considering the function of these TCSs in bacterial survival and their potential role as drug targets, it is important to understand the exact mechanisms underlying signal perception. The differences between the sensing of appropriate signals and the transcriptional activation of the TCS system are often not well described, and the signaling mechanisms are only partially understood. Here, we review present insights into which signals are sensed by histidine kinases in S. aureus to promote appropriate gene expression in response to diverse environmental challenges.
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Affiliation(s)
- Lisa Bleul
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tubingen, Germany;
- Cluster of Excellence EXC 2124 “Controlling Microbes to Fight Infections”, University of Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tubingen, Germany
| | - Patrice Francois
- Genomic Research Laboratory, Infectious Diseases Service, University Hospitals of Geneva University Medical Center, Michel Servet 1, CH-1211 Geneva, Switzerland;
| | - Christiane Wolz
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tubingen, Germany;
- Cluster of Excellence EXC 2124 “Controlling Microbes to Fight Infections”, University of Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tubingen, Germany
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7
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Global Chromosome Topology and the Two-Component Systems in Concerted Manner Regulate Transcription in Streptomyces. mSystems 2021; 6:e0114221. [PMID: 34783581 PMCID: PMC8594442 DOI: 10.1128/msystems.01142-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Bacterial gene expression is controlled at multiple levels, with chromosome supercoiling being one of the most global regulators. Global DNA supercoiling is maintained by the orchestrated action of topoisomerases. In Streptomyces, mycelial soil bacteria with a complex life cycle, topoisomerase I depletion led to elevated chromosome supercoiling, changed expression of a significant fraction of genes, delayed growth, and blocked sporulation. To identify supercoiling-induced sporulation regulators, we searched for Streptomyces coelicolor transposon mutants that were able to restore sporulation despite high chromosome supercoiling. We established that transposon insertion in genes encoding a novel two-component system named SatKR reversed the sporulation blockage resulting from topoisomerase I depletion. Transposition in satKR abolished the transcriptional induction of the genes within the so-called supercoiling-hypersensitive cluster (SHC). Moreover, we found that activated SatR also induced the same set of SHC genes under normal supercoiling conditions. We determined that the expression of genes in this region impacted S. coelicolor growth and sporulation. Interestingly, among the associated products is another two-component system (SitKR), indicating the potential for cascading regulatory effects driven by the SatKR and SitKR two-component systems. Thus, we demonstrated the concerted activity of chromosome supercoiling and a hierarchical two-component signaling system that impacts gene activity governing Streptomyces growth and sporulation. IMPORTANCEStreptomyces microbes, soil bacteria with complex life cycle, are the producers of a broad range of biologically active compounds (e.g., antibiotics). Streptomyces bacteria respond to various environmental signals using a complex transcriptional regulation mechanism. Understanding regulation of their gene expression is crucial for Streptomyces application as industrial organisms. Here, on the basis of the results of extensive transcriptomics analyses, we describe the concerted gene regulation by global DNA supercoiling and novel two-component system. Our data indicate that regulated genes encode growth and sporulation regulators. Thus, we demonstrate that Streptomyces bacteria link the global regulatory strategies to adjust life cycle to unfavorable conditions.
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8
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Pi H, Chu ML, Ivan SJ, Latario CJ, Toth AM, Carlin SM, Hillebrand GH, Lin HK, Reppart JD, Stauff DL, Skaar EP. Directed evolution reveals the mechanism of HitRS signaling transduction in Bacillus anthracis. PLoS Pathog 2020; 16:e1009148. [PMID: 33362282 PMCID: PMC7790381 DOI: 10.1371/journal.ppat.1009148] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 01/07/2021] [Accepted: 11/11/2020] [Indexed: 12/03/2022] Open
Abstract
Two component systems (TCSs) are a primary mechanism of signal sensing and response in bacteria. Systematic characterization of an entire TCS could provide a mechanistic understanding of these important signal transduction systems. Here, genetic selections were employed to dissect the molecular basis of signal transduction by the HitRS system that detects cell envelope stress in the pathogen Bacillus anthracis. Numerous point mutations were isolated within HitRS, 17 of which were in a 50-residue HAMP domain. Mutational analysis revealed the importance of hydrophobic interactions within the HAMP domain and highlighted its essentiality in TCS signaling. In addition, these data defined residues critical for activities intrinsic to HitRS, uncovered specific interactions among individual domains and between the two signaling proteins, and revealed that phosphotransfer is the rate-limiting step for signal transduction. Furthermore, this study establishes the use of unbiased genetic selections to study TCS signaling and provides a comprehensive mechanistic understanding of an entire TCS. Bacterial TCSs are a primary strategy for stress sensing and niche adaptation. Although individual domains and proteins of these systems have been extensively studied, systematic characterization of an entire TCS is rare. In this study, through unbiased genetic selections and rigorous biochemical analysis, we provide a detailed characterization and structure-function analysis of an entire TCS and extend our understanding of the molecular basis of signal transduction through TCSs. Moreover, this study provides a comprehensive map of point-mutations in these well-conserved signaling proteins, which will be broadly useful for studying other TCSs. The described genetic selection strategies are applicable to any TCS, providing a powerful tool for researchers interested in microbial signal transduction.
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Affiliation(s)
- Hualiang Pi
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Institute for Infection, Immunology, & Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Michelle L. Chu
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Samuel J. Ivan
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Casey J. Latario
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Allen M. Toth
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Sophia M. Carlin
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Gideon H. Hillebrand
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Hannah K. Lin
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Jared D. Reppart
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Devin L. Stauff
- Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America
| | - Eric P. Skaar
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Institute for Infection, Immunology, & Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- * E-mail:
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9
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Yan H, Wang Q, Teng M, Li X. The DNA-binding mechanism of the TCS response regulator ArlR from Staphylococcus aureus. J Struct Biol 2019; 208:107388. [PMID: 31520693 DOI: 10.1016/j.jsb.2019.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 09/05/2019] [Accepted: 09/10/2019] [Indexed: 10/26/2022]
Abstract
ArlRS is an essential two-component system in Staphylococcus aureus that regulates the transcription of virulence factors and participate in numerous pathogenic and symbiotic processes. In this work, we identified different DNA binding properties and oligomerization states among the DNA-binding domain of ArlR (ArlRDBD) and the phosphorylated and unphosphorylated full-length ArlR. Based on a 2.5-Å resolution crystal structure of ArlRDBD and subsequent mutagenesis experiments, we confirmed the DNA-binding site of ArlR and the preferred binding sequences in the agr promoter that enables the DNA recognition process. Finally, we propose a putative transcription regulation mechanism for ArlR. This work will facilitate our understanding of the DNA binding affinity regulatory mechanism between the phosphorylated and unphosphorylated response regulator in the two-component system.
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Affiliation(s)
- Hui Yan
- Hefei National Laboratory for Physical Sciences at Microscale, National Synchrotron Radiation Laboratory, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
| | - Qing Wang
- Hefei National Laboratory for Physical Sciences at Microscale, National Synchrotron Radiation Laboratory, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
| | - Maikun Teng
- Hefei National Laboratory for Physical Sciences at Microscale, National Synchrotron Radiation Laboratory, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China.
| | - Xu Li
- Hefei National Laboratory for Physical Sciences at Microscale, National Synchrotron Radiation Laboratory, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China.
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10
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Bai J, Zhu X, Zhao K, Yan Y, Xu T, Wang J, Zheng J, Huang W, Shi L, Shang Y, Lv Z, Wang X, Wu Y, Qu D. The role of ArlRS in regulating oxacillin susceptibility in methicillin-resistant Staphylococcus aureus indicates it is a potential target for antimicrobial resistance breakers. Emerg Microbes Infect 2019; 8:503-515. [PMID: 30924407 PMCID: PMC6455253 DOI: 10.1080/22221751.2019.1595984] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA), also known as oxacillin-resistant S. aureus, is a leading cause of community and hospital associated infections globally. In this work, we found that deletion of the arlRS two-component system genes in the USA300 and USA500 strains resulted in increased susceptibilities to oxacillin (8–16-fold decrease in minimal inhibitory concentrations). In USA300ΔarlRS, transcriptional levels of mecA or blaZ showed no obvious change, while mRNA levels of spx showed a 4-fold decrease at 4 h and a 6.3-fold decrease at 10 h. Overexpression of spx in ΔarlRS restored oxacillin resistance to a similar level in USA300. In addition, gel shift assay showed that the recombinant ArlR bound to spx promoter region. Furthermore, silencing of spx led to a significant increase of oxacillin susceptibility in multiple MRSA isolates. Our results indicate that ArlRS plays a strong role in regulating oxacillin resistance in MRSA strains, which involves direct modulation of spx expression. Moreover, oritavancin showed inhibition to ATPase activity of the recombinant histidine kinase ArlS (IC50 = 5.47 μM). Oritavancin had synergy effect on oxacillin activity against the MRSA strains in both planktonic and biofilm state. Our data suggest that ArlRS is an attractive target for breaking antimicrobial resistance of MRSA.
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Affiliation(s)
- Jinna Bai
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
| | - Xiaoyi Zhu
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
| | - Keqing Zhao
- b Department of Otorhinolaryngology-Head and Neck Surgery, Eye & ENT Hospital, Shanghai Key Clinical Disciplines of otorhinolaryngology , Fudan University , Shanghai , People's Republic of China
| | - Yingjie Yan
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
| | - Tao Xu
- c Key Laboratory of Medical Molecular Virology , Huashan Hospital, Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
| | - Jiaxue Wang
- d Department of Laboratory Medicine , Hangzhou Medical College , Hangzhou , Zhejiang , People's Republic of China
| | - Jinxing Zheng
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China.,e Department of Infectious Diseases and the Key Laboratory of Endogenous Infection , Shenzhen Nanshan People's Hospital of Shenzhen University , Shenzhen , People's Republic of China
| | - Wei Huang
- f Medical Clinic, Hangzhou Haiqin Sanatorium , Hangzhou , Zhejiang , People's Republic of China
| | - Le Shi
- b Department of Otorhinolaryngology-Head and Neck Surgery, Eye & ENT Hospital, Shanghai Key Clinical Disciplines of otorhinolaryngology , Fudan University , Shanghai , People's Republic of China
| | - Yongpeng Shang
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
| | - Zhihui Lv
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
| | - Xiaofei Wang
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
| | - Yang Wu
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
| | - Di Qu
- a Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai , People's Republic of China
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Martis B S, Forquet R, Reverchon S, Nasser W, Meyer S. DNA Supercoiling: an Ancestral Regulator of Gene Expression in Pathogenic Bacteria? Comput Struct Biotechnol J 2019; 17:1047-1055. [PMID: 31452857 PMCID: PMC6700405 DOI: 10.1016/j.csbj.2019.07.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/17/2019] [Accepted: 07/24/2019] [Indexed: 12/28/2022] Open
Abstract
DNA supercoiling acts as a global and ancestral regulator of bacterial gene expression. In this review, we advocate that it plays a pivotal role in host-pathogen interactions by transducing environmental signals to the bacterial chromosome and coordinating its transcriptional response. We present available evidence that DNA supercoiling is modulated by environmental stress conditions relevant to the infection process according to ancestral mechanisms, in zoopathogens as well as phytopathogens. We review the results of transcriptomics studies obtained in widely distant bacterial species, showing that such structural transitions of the chromosome are associated to a complex transcriptional response affecting a large fraction of the genome. Mechanisms and computational models of the transcriptional regulation by DNA supercoiling are then discussed, involving both basal interactions of RNA Polymerase with promoter DNA, and more specific interactions with regulatory proteins. A final part is specifically focused on the regulation of virulence genes within pathogenicity islands of several pathogenic bacterial species.
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Affiliation(s)
- Shiny Martis B
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
| | - Raphaël Forquet
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
| | - Sylvie Reverchon
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
| | - William Nasser
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
| | - Sam Meyer
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
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Landa SB, Korabliov PV, Semenova EV, Filatov MV. Peculiarities of the formation and subsequent removal of the circulating immune complexes from the bloodstream during the process of digestion. F1000Res 2018; 7:618. [PMID: 30079242 PMCID: PMC6058468 DOI: 10.12688/f1000research.14406.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/10/2018] [Indexed: 12/24/2022] Open
Abstract
Background: Large protein aggregates, known as circulating immune complexes (CICs), are formed in biological fluids as a result of the development of the body's immune response to various provoking factors. The kinetic characteristics of the formation and removal of immune complexes (ICs), their physical parameters, the isotypic composition of immunoglobulins (Igs) and the antigenic component of the CICs may reflect certain aspects of certain pathological and metabolic processes taking place in humans and animals. The aim of this study is to assess the kinetic characteristics of the formation and removal of the CICs that form in blood after eating. We also analyze the changes in the isotypic composition of Igs of ICs that accompany this biological process in rodents and humans. Methods: We identified the CICs, which differed in size and class of Igs, using dynamic light scattering. To remove ICs from the plasma, we used immune-affinity sedimentation. Monoclonal antibodies for the Igs of different isotypes were added to the plasma samples to determine the isotypic composition of the ICs. Results: A large number of ICs were formed in the blood of rats and humans after eating (food CICs). In rats, food ICs are almost immediately filtered in the liver, without circulating in the bloodstream through the body. In humans, the level of food ICs in the blood increases for 3.5 h after ingestion, then within 7-8 h their gradual removal takes place. It was found that in the process of digestion in humans, the isotypic composition of Igs in the CICs changes and becomes more diverse. Conclusions: The molecular-cellular mechanisms of the formation and utilization of food CICs in humans and rodents do not match completely.
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Affiliation(s)
- Sergej B. Landa
- Division of Molecular and Radiation Biophysics, National Research Center , Gatchina, 188300, Russian Federation
| | - Pavel V. Korabliov
- State Research Institute Center for Innovative Medicine, Vilnius, LT-01102, Lithuania
| | - Elena V. Semenova
- Division of Molecular and Radiation Biophysics, National Research Center , Gatchina, 188300, Russian Federation
| | - Michael V. Filatov
- Division of Molecular and Radiation Biophysics, National Research Center , Gatchina, 188300, Russian Federation
- Saint Petersburg State Research Institute of Phthisiopulmonology of the Ministry of Healthcare of the Russian Federation, Saint Petersburg, 191036, Russian Federation
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Balachandran M, Giannone RJ, Bemis DA, Kania SA. Molecular basis of surface anchored protein A deficiency in the Staphylococcus aureus strain Wood 46. PLoS One 2017; 12:e0183913. [PMID: 28859130 PMCID: PMC5578664 DOI: 10.1371/journal.pone.0183913] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 08/14/2017] [Indexed: 11/18/2022] Open
Abstract
Protein A in Staphylococcus aureus is encoded by the spa (staphylococcal protein A) gene and binds to immunoglobulin (Ig). The S. aureus strain Wood 46 has been variously reported as protein A-deficient and/or spa negative and used as a control in animal models of staphylococcal infections. The results of this study indicate that Wood 46 has normal spa expression but transcribes very low levels of the srtA gene which encodes the sortase A (SrtA) enzyme. This is consistent with unique mutations in the srtA promoter. In this study, a low level of sortase A explains deficient anchoring of proteins with an LPXTG motif, such as protein A, fibrinogen-binding protein and fibronectin-binding proteins A and B on to the peptidoglycan cell wall. The activity of secreted protein A is an important consideration for use of Wood 46 in functional experiments and animal models.
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Affiliation(s)
- Manasi Balachandran
- Department of Biomedical and Diagnostic Sciences, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Richard J. Giannone
- Chemical Sciences Division, Mass Spectrometry and Laser Spectrometry, Oakridge National Laboratories, Oakridge, Tennessee, United States of America
| | - David A. Bemis
- Department of Biomedical and Diagnostic Sciences, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Stephen A. Kania
- Department of Biomedical and Diagnostic Sciences, The University of Tennessee, Knoxville, Tennessee, United States of America
- * E-mail:
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Dorman CJ, Dorman MJ. DNA supercoiling is a fundamental regulatory principle in the control of bacterial gene expression. Biophys Rev 2016; 8:89-100. [PMID: 28510216 DOI: 10.1007/s12551-016-0238-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 06/01/2016] [Indexed: 11/28/2022] Open
Abstract
Although it has become routine to consider DNA in terms of its role as a carrier of genetic information, it is also an important contributor to the control of gene expression. This regulatory principle arises from its structural properties. DNA is maintained in an underwound state in most bacterial cells and this has important implications both for DNA storage in the nucleoid and for the expression of genetic information. Underwinding of the DNA through reduction in its linking number potentially imparts energy to the duplex that is available to drive DNA transactions, such as transcription, replication and recombination. The topological state of DNA also influences its affinity for some DNA binding proteins, especially in DNA sequences that have a high A + T base content. The underwinding of DNA by the ATP-dependent topoisomerase DNA gyrase creates a continuum between metabolic flux, DNA topology and gene expression that underpins the global response of the genome to changes in the intracellular and external environments. These connections describe a fundamental and generalised mechanism affecting global gene expression that underlies the specific control of transcription operating through conventional transcription factors. This mechanism also provides a basal level of control for genes acquired by horizontal DNA transfer, assisting microbial evolution, including the evolution of pathogenic bacteria.
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Affiliation(s)
- Charles J Dorman
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin 2, Ireland.
| | - Matthew J Dorman
- Department of Genetics, Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland.,Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
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DNA supercoiling is a fundamental regulatory principle in the control of bacterial gene expression. Biophys Rev 2016; 8:209-220. [PMID: 28510224 DOI: 10.1007/s12551-016-0205-y] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 06/01/2016] [Indexed: 12/27/2022] Open
Abstract
Although it has become routine to consider DNA in terms of its role as a carrier of genetic information, it is also an important contributor to the control of gene expression. This regulatory principle arises from its structural properties. DNA is maintained in an underwound state in most bacterial cells and this has important implications both for DNA storage in the nucleoid and for the expression of genetic information. Underwinding of the DNA through reduction in its linking number potentially imparts energy to the duplex that is available to drive DNA transactions, such as transcription, replication and recombination. The topological state of DNA also influences its affinity for some DNA binding proteins, especially in DNA sequences that have a high A + T base content. The underwinding of DNA by the ATP-dependent topoisomerase DNA gyrase creates a continuum between metabolic flux, DNA topology and gene expression that underpins the global response of the genome to changes in the intracellular and external environments. These connections describe a fundamental and generalised mechanism affecting global gene expression that underlies the specific control of transcription operating through conventional transcription factors. This mechanism also provides a basal level of control for genes acquired by horizontal DNA transfer, assisting microbial evolution, including the evolution of pathogenic bacteria.
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16
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The Role of Two-Component Signal Transduction Systems in Staphylococcus aureus Virulence Regulation. Curr Top Microbiol Immunol 2015; 409:145-198. [PMID: 26728068 DOI: 10.1007/82_2015_5019] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Staphylococcus aureus is a versatile, opportunistic human pathogen that can asymptomatically colonize a human host but can also cause a variety of cutaneous and systemic infections. The ability of S. aureus to adapt to such diverse environments is reflected in the presence of complex regulatory networks fine-tuning metabolic and virulence gene expression. One of the most widely distributed mechanisms is the two-component signal transduction system (TCS) which allows a pathogen to alter its gene expression profile in response to environmental stimuli. The simpler TCSs consist of only a transmembrane histidine kinase (HK) and a cytosolic response regulator. S. aureus encodes a total of 16 conserved pairs of TCSs that are involved in diverse signalling cascades ranging from global virulence gene regulation (e.g. quorum sensing by the Agr system), the bacterial response to antimicrobial agents, cell wall metabolism, respiration and nutrient sensing. These regulatory circuits are often interconnected and affect each other's expression, thus fine-tuning staphylococcal gene regulation. This manuscript gives an overview of the current knowledge of staphylococcal environmental sensing by TCS and its influence on virulence gene expression and virulence itself. Understanding bacterial gene regulation by TCS can give major insights into staphylococcal pathogenicity and has important implications for knowledge-based drug design and vaccine formulation.
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Wu Y, Liu J, Jiang J, Hu J, Xu T, Wang J, Qu D. Role of the two-component regulatory system arlRS in ica operon and aap positive but non-biofilm-forming Staphylococcus epidermidis isolates from hospitalized patients. Microb Pathog 2014; 76:89-98. [PMID: 25263000 DOI: 10.1016/j.micpath.2014.09.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 09/21/2014] [Accepted: 09/24/2014] [Indexed: 10/24/2022]
Abstract
The ica operon and aap gene are important factors for Staphylococcus epidermidis biofilm formation. However, we found 15 out of 101 S. epidermidis strains isolated from patients had both the ica operon and the aap gene in the genome but could not form biofilms (ica(+)aap(+)/BF(-) isolates). Compared with standard strain RP62A, the 15 ica(+)aap(+)/BF(-) isolates had similar growth curves and initial attachment abilities, but had much lower apparent transcription levels of the icaA gene and significantly less production of polysaccharide intercellular adhesion (PIA). Furthermore, the expression of accumulation-associated protein in ica(+)aap(+)/BF(-) isolates was much weaker than in RP62A. The mRNA levels of icaADBC transcription-related regulatory genes, including icaR, sarA, rsbU, srrA, arlRS and luxS, were measured in the 15 ica(+)aap(+)/BF(-) clinical isolates. The mRNA levels of arlR and rsbU in all of the ica(+)aap(+)/BF(-) isolates were lower than in RP62A at 4 h. At 10 h, 14/15 of the isolates showed lower mRNA levels of arlR and rsbU than shown by RP62A. However, expression of sarA, luxS, srrA and icaR varied in different ica(+)aap(+)/BF(-) isolates. To further investigate the role of arlRS in biofilm formation, we analyzed icaA, sarA and rsbU transcription, PIA synthesis, Aap expression and biofilm formation in an arlRS deletion mutant of S. epidermidis strain 1457 and all were much less than in the wild type strain. This is consistent with the hypothesis that ArlRS may play an important role in regulating biofilm formation by the ica(+)aap(+)/BF(-)S. epidermidis clinical isolates and operate via both ica-dependent and Aap-dependent pathways.
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Affiliation(s)
- Yang Wu
- Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China
| | - Jingran Liu
- Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China
| | - Juan Jiang
- Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China
| | - Jian Hu
- Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China
| | - Tao Xu
- Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China
| | - Jiaxue Wang
- Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China
| | - Di Qu
- Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China.
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19
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Schröder W, Bernhardt J, Marincola G, Klein-Hitpass L, Herbig A, Krupp G, Nieselt K, Wolz C. Altering gene expression by aminocoumarins: the role of DNA supercoiling in Staphylococcus aureus. BMC Genomics 2014; 15:291. [PMID: 24734910 PMCID: PMC4023603 DOI: 10.1186/1471-2164-15-291] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 03/17/2014] [Indexed: 11/29/2022] Open
Abstract
Background It has been shown previously that aminocoumarin antibiotics such as novobiocin lead to immediate downregulation of recA expression and thereby inhibit the SOS response, mutation frequency and recombination capacity in Staphylococcus aureus. Aminocoumarins function by inhibiting the ATPase activity of DNA gyrase subunit B with a severe impact on DNA supercoiling. Results Here, we have analysed the global impact of the DNA relaxing agent novobiocin on gene expression in S. aureus. Using a novobiocin-resistant mutant, it became evident that the change in recA expression is due to gyrase inhibition. Microarray analysis and northern blot hybridisation revealed that the expression levels of a distinct set of genes were increased (e.g., recF-gyrB-gyrA, the rib operon and the ure operon) or decreased (e.g., arlRS, recA, lukA, hlgC and fnbA) by novobiocin. The two-component ArlRS system was previously found to decrease the level of supercoiling in S. aureus. Thus, downregulation of arlRS might partially compensate for the relaxing effect of novobiocin. Global analysis and gene mapping of supercoiling-sensitive genes did not provide any indication that they are clustered in the genome. Promoter fusion assays confirmed that the responsiveness of a given gene is intrinsic to the promoter region but independent of the chromosomal location. Conclusions The results indicate that the molecular properties of a given promoter, rather than the chromosomal topology, dictate the responsiveness to changes in supercoiling in the pathogen Staphylococcus aureus.
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Affiliation(s)
| | | | | | | | | | | | | | - Christiane Wolz
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Elfriede-Aulhorn-Strasse 6, 72076 Tübingen, Germany.
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Schröder W, Goerke C, Wolz C. Opposing effects of aminocoumarins and fluoroquinolones on the SOS response and adaptability in Staphylococcus aureus. J Antimicrob Chemother 2012; 68:529-38. [PMID: 23169893 DOI: 10.1093/jac/dks456] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
OBJECTIVES RecA is the key enzyme involved in DNA repair, recombination and induction of the SOS response and is central to the development of antibiotic resistance. Here we assessed the interaction of two different gyrase inhibitors, ciprofloxacin (a fluoroquinolone) and novobiocin (an aminocoumarin), on RecA activity and the SOS response in Staphylococcus aureus. METHODS The influence of different gyrase inhibitors on the SOS response of S. aureus (including recA and lexA mutants) was analysed by northern blot analysis, real-time RT-PCR, western blot analysis and promoter activity assays. Recombination as well as mutation frequencies were determined for the different antibiotic combinations. RESULTS We verified that ciprofloxacin leads to RecA activation and therefore induction of the SOS response. In contrast, novobiocin treatment resulted in an inhibition of recA transcription independent of LexA. When novobiocin and ciprofloxacin were added simultaneously, recA was reduced to the same level as with novobiocin alone. In combination, novobiocin also partially reduces the ciprofloxacin-mediated induction of the LexA target gene umuC (error-prone polymerase). Apart from reducing recA and umuC expression, novobiocin also inhibited the frequency of recombination, mutation and the formation of non-haemolytic variants. CONCLUSION In summary, aminocoumarins inhibit recA expression in S. aureus and probably delay the process of developing antibiotic resistance and gene transfer. A clinical re-evaluation of these compounds as well as designing more applicable derivatives should be considered.
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Affiliation(s)
- Wiebke Schröder
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Elfriede-Aulhorn-Strasse-6, 72076 Tübingen, Germany
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Junecko JM, Zielinska AK, Mrak LN, Ryan DC, Graham JW, Smeltzer MS, Lee CY. Transcribing virulence in Staphylococcus aureus. World J Clin Infect Dis 2012; 2:63-76. [DOI: 10.5495/wjcid.v2.i4.63] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Staphylococcus aureus (S. aureus) is an important human pathogen capable of causing a diverse range of infections. Once regarded as an opportunistic pathogen causing primarily nosocomial infections, recent years have seen the emergence of S. aureus strains capable of causing serious infection even in otherwise healthy human hosts. There has been much debate about whether this transition is a function of unique genotypic characteristics or differences in the expression of conserved virulence factors, but irrespective of this debate it is clear that the ability of S. aureus to cause infection in all of its diverse forms is heavily influenced by its ability to modulate gene expression in response to changing conditions within the human host. Indeed, the S. aureus genome encodes more than 100 transcriptional regulators that modulate the production of virulence factors either directly via interactions with cis elements associated with genes encoding virulence factors or indirectly through their complex interactions with each other. The goal of this review is to summarize recent work describing these regulators and their contribution to defining S. aureus as a human pathogen.
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Agnello M, Wong-Beringer A. Differentiation in quinolone resistance by virulence genotype in Pseudomonas aeruginosa. PLoS One 2012; 7:e42973. [PMID: 22905192 PMCID: PMC3414457 DOI: 10.1371/journal.pone.0042973] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 07/16/2012] [Indexed: 11/19/2022] Open
Abstract
Pseudomonas aeruginosa is a leading pathogen that has become increasingly resistant to the fluoroquinolone antibiotics due to widespread prescribing. Adverse outcomes have been shown for patients infected with fluoroquinolone-resistant strains. The type III secretion system (TTSS) is a major virulence determinant during acute infections through the injection of effector toxins into host cells. Most strains exhibit a unique TTSS virulence genotype defined by the presence of either exoS or exoU gene encoding two of the effector toxins, ExoS and ExoU, respectively. Specific TTSS effector genotype has been shown previously to differentially impact virulence in pneumonia. In this study, we examined the relationship between TTSS effector genotype and fluoroquinolone resistance mechanisms in a collection of 270 respiratory isolates. We found that a higher proportion of exoU+ strains were fluoroquinolone-resistant compared to exoS+ strains (63% vs 49%, p = 0.03) despite its lower overall prevalence (38% exoU+ vs 56% exoS+). Results from sequencing the quinolone resistance determining regions (QRDRs) of the 4 target genes (gyrA, gyrB, parC, parE) indicated that strains containing the exoU gene were more likely to acquire ≥2 mutations than exoS+ strains at MICs ≤8 µg/ml (13% vs none) and twice as likely to have mutations in both gyrA and parC than exoS+ strains (48% vs 24% p = 0.0439). Our findings indicate that P. aeruginosa strains differentially develop resistance-conferring mutations that correlate with TTSS effector genotype and the more virulent exoU+ subpopulation. Differences in mutational processes by virulence genotype that were observed suggest co-evolution of resistance and virulence traits favoring a more virulent genotype in the quinolone-rich clinical environment.
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Affiliation(s)
- Melissa Agnello
- School of Pharmacy, University of Southern California, Los Angeles, California, United States of America
| | - Annie Wong-Beringer
- School of Pharmacy, University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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Miyazaki S, Matsumoto Y, Sekimizu K, Kaito C. Evaluation of Staphylococcus aureus virulence factors using a silkworm model. FEMS Microbiol Lett 2011; 326:116-24. [PMID: 22092964 DOI: 10.1111/j.1574-6968.2011.02439.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 08/29/2011] [Accepted: 10/17/2011] [Indexed: 02/04/2023] Open
Abstract
Previous studies have indicated that the silkworm model is useful for identifying virulence genes of Staphylococcus aureus, a human pathogenic bacterium. Here we examined the scope of S. aureus virulence factors that can be evaluated using the silkworm model. Gene-disrupted mutants of the agr locus, arlS gene and saeS gene, which regulate the expression of cell surface adhesins and hemolysins, exhibited attenuated virulence in silkworms. Mutants of the hla gene encoding α-hemolysin, the hlb gene encoding β-hemolysin, and the psmα and psmβ operons encoding cytolysins, however, showed virulence in silkworms indistinguishable from that of the parent strain. Thus, these S. aureus cytolysins are not required for virulence in silkworms. In contrast, the gene-disrupted mutants of clfB, fnbB and sdrC, which encode cell-wall-anchored proteins, attenuated S. aureus virulence in silkworms. In addition, the mutant of the srtA gene encoding sortase A, which anchors cell-wall proteins, showed attenuated virulence in silkworms. These findings suggest that the silkworm model can be used to evaluate S. aureus cell-wall proteins and regulatory proteins as virulence factors.
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Affiliation(s)
- Shinya Miyazaki
- Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Japan
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Abstract
Transcriptional regulation remains poorly understood in Mycoplasma genitalium, the smallest self-replicating cell and the causative agent of a spectrum of urogenital diseases. Previously, we reported that MG_149, a lipoprotein-encoding gene, was highly induced under physiological hyperosmolarity conditions. In this study we further analysed MG_149 transcription with a focus on the identification of promoter elements and regulatory mechanisms. We established MG_149 as a genuine osmoinducible gene that exhibited the highest transcript abundance compared with other lipoprotein genes. Using genetic approaches, we demonstrated that the -10 region of the MG_149 promoter was essential for osmoinduction. Moreover, we showed that MG_149 osmoinduction was regulated by DNA supercoiling, as the presence of novobiocin decreased MG_149 expression in a dose-dependent manner. Taken together, these results indicate that DNA supercoiling participates in controlling MG_149 expression during in vivo-like conditions.
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Affiliation(s)
- Wenbo Zhang
- Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA
| | - Joel B. Baseman
- Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA
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Transcriptional profiling of XdrA, a new regulator of spa transcription in Staphylococcus aureus. J Bacteriol 2010; 192:5151-64. [PMID: 20675497 DOI: 10.1128/jb.00491-10] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcription of spa, encoding the virulence factor protein A in Staphylococcus aureus, is tightly controlled by a complex regulatory network, ensuring its temporal expression over growth and at appropriate stages of the infection process. Transcriptomic profiling of XdrA, a DNA-binding protein that is conserved in all S. aureus genomes and shares similarity with the XRE family of helix-turn-helix, antitoxin-like proteins, revealed it to be a previously unidentified activator of spa transcription. To assess how XdrA fits into the complex web of spa regulation, a series of regulatory mutants were constructed; consisting of single, double, triple, and quadruple mutants lacking XdrA and/or the three key regulators previously shown to influence spa transcription directly (SarS, SarA, and RNAIII). A series of lacZ reporter gene fusions containing nested deletions of the spa promoter identified regions influenced by XdrA and the other three regulators. XdrA had almost as strong an activating effect on spa as SarS and acted on the same spa operator regions as SarS, or closely overlapping regions. All data from microarrays, Northern and Western blot analyses, and reporter gene fusion experiments indicated that XdrA is a major activator of spa expression that appears to act directly on the spa promoter and not through previously characterized regulators.
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Reduced vancomycin susceptibility in Staphylococcus aureus, including vancomycin-intermediate and heterogeneous vancomycin-intermediate strains: resistance mechanisms, laboratory detection, and clinical implications. Clin Microbiol Rev 2010; 23:99-139. [PMID: 20065327 DOI: 10.1128/cmr.00042-09] [Citation(s) in RCA: 685] [Impact Index Per Article: 45.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The emergence of vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) over the past decade has provided a challenge to diagnostic microbiologists to detect these strains, clinicians treating patients with infections due to these strains, and researchers attempting to understand the resistance mechanisms. Recent data show that these strains have been detected globally and in many cases are associated with glycopeptide treatment failure; however, more rigorous clinical studies are required to clearly define the contribution of hVISA to glycopeptide treatment outcomes. It is now becoming clear that sequential point mutations in key global regulatory genes contribute to the hVISA and VISA phenotypes, which are associated predominately with cell wall thickening and restricted vancomycin access to its site of activity in the division septum; however, the phenotypic features of these strains can vary because the mutations leading to resistance can vary. Interestingly, changes in the staphylococcal surface and expression of agr are likely to impact host-pathogen interactions in hVISA and VISA infections. Given the subtleties of vancomycin susceptibility testing against S. aureus, it is imperative that diagnostic laboratories use well-standardized methods and have a framework for detecting reduced vancomycin susceptibility in S. aureus.
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In the Staphylococcus aureus two-component system sae, the response regulator SaeR binds to a direct repeat sequence and DNA binding requires phosphorylation by the sensor kinase SaeS. J Bacteriol 2010; 192:2111-27. [PMID: 20172998 DOI: 10.1128/jb.01524-09] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Staphylococcus aureus uses the SaeRS two-component system to control the expression of many virulence factors such as alpha-hemolysin and coagulase; however, the molecular mechanism of this signaling has not yet been elucidated. Here, using the P1 promoter of the sae operon as a model target DNA, we demonstrated that the unphosphorylated response regulator SaeR does not bind to the P1 promoter DNA, while its C-terminal DNA binding domain alone does. The DNA binding activity of full-length SaeR could be restored by sensor kinase SaeS-induced phosphorylation. Phosphorylated SaeR is more resistant to digestion by trypsin, suggesting conformational changes. DNase I footprinting assays revealed that the SaeR protection region in the P1 promoter contains a direct repeat sequence (GTTAAN(6)GTTAA [where N is any nucleotide]). This sequence is critical to the binding of phosphorylated SaeR. Mutational changes in the repeat sequence greatly reduced both the in vitro binding of SaeR and the in vivo function of the P1 promoter. From these results, we concluded that SaeR recognizes the direct repeat sequence as a binding site and that binding requires phosphorylation by SaeS.
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Abstract
The Gram-negative bacterium Escherichia coli and its close relative Salmonella enterica have made important contributions historically to our understanding of how bacteria control DNA supercoiling and of how supercoiling influences gene expression and vice versa. Now they are contributing again by providing examples where changes in DNA supercoiling affect the expression of virulence traits that are important for infectious disease. Available examples encompass both the earliest stages of pathogen–host interactions and the more intimate relationships in which the bacteria invade and proliferate within host cells. A key insight concerns the link between the physiological state of the bacterium and the activity of DNA gyrase, with downstream effects on the expression of genes with promoters that sense changes in DNA supercoiling. Thus the expression of virulence traits by a pathogen can be interpreted partly as a response to its own changing physiology. Knowledge of the molecular connections between physiology, DNA topology and gene expression offers new opportunities to fight infection.
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Affiliation(s)
- Charles J Dorman
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College, Dublin 2, Ireland.
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Salomo M, Keyser UF, Struhalla M, Kremer F. Optical tweezers to study single Protein A/Immunoglobulin G interactions at varying conditions. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 37:927-34. [DOI: 10.1007/s00249-008-0310-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Revised: 03/05/2008] [Accepted: 03/10/2008] [Indexed: 10/22/2022]
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Chen Z, Luong TT, Lee CY. The sbcDC locus mediates repression of type 5 capsule production as part of the SOS response in Staphylococcus aureus. J Bacteriol 2007; 189:7343-50. [PMID: 17704228 PMCID: PMC2168426 DOI: 10.1128/jb.01079-07] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Most strains of Staphylococcus aureus produce one type of capsular polysaccharide that belongs to either type 5 or type 8. The production of these capsules has been shown to be regulated by various regulators. Here we report that the sbcD and sbcC genes are involved in the repression of type 5 capsule production. Chromosomal deletions in the sbcDC genes resulted in increased capsule promoter activity, capsule gene transcripts, and capsule production. The survival rates of the sbcDC deletion mutant were reduced upon UV irradiation compared to those for the wild-type strain Newman, suggesting that the genes are involved in DNA repair in S. aureus. The two genes were organized as an operon and were expressed very early in the exponential growth phase. A subinhibitory concentration of ciprofloxacin or mitomycin C induced sbcDC transcription but repressed the capsule promoter activity, suggesting that the sbcDC genes and the capsule genes are part of the SOS regulon. By reporter gene fusion and Northern blotting, we found that sbcDC regulated capsule by downregulating arl and mgr. Further genetic studies indicate that sbcDC functions upstream of arl and mgr in capsule regulation. Collectively, our results indicate that sbcDC, upon the SOS response, represses type 5 capsule production through an arl-mgr pathway. To our knowledge, this is the first demonstration that an SbcDC homolog was involved in transcriptional regulation.
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Affiliation(s)
- Zhongyi Chen
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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Morikawa K, Ohniwa RL, Kim J, Takeshita SL, Maruyama A, Inose Y, Takeyasu K, Ohta T. Biochemical, molecular genetic, and structural analyses of the staphylococcal nucleoid. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2007; 13:30-5. [PMID: 17234034 DOI: 10.1017/s1431927607070080] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Accepted: 09/18/2006] [Indexed: 05/13/2023]
Abstract
The nucleoid structure of an important human pathogen, Staphylococcus aureus, was dissected by atomic force microscopy (AFM). The nucleoids dispersed on a cover glass consisted of fibrous units with two different widths of 40 and 80 nm, a feature shared with those of Escherichia coli. On the other hand, cells exposed to an oxidative stress exhibited clogged nucleoids. A knock-out of mrgA (metallo regulated genes A) encoding a staphylococcal homolog of the nucleoid compaction factor (E. coli Dps) eliminated the compaction response to the oxidative stress and reduced the susceptibilities to H2O2 and UV irradiation. We also observed that the negative supercoiling of plasmids is increased by the oxidative stress. A possible interrelation between the helical density and the nucleoid compaction is discussed in relation to the oxidative stress response.
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Affiliation(s)
- Kazuya Morikawa
- Institute of Basic Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tennoh-dai, Tsukuba 305-8575, Japan.
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O Cróinín T, Carroll RK, Kelly A, Dorman CJ. Roles for DNA supercoiling and the Fis protein in modulating expression of virulence genes during intracellular growth of Salmonella enterica serovar Typhimurium. Mol Microbiol 2006; 62:869-82. [PMID: 16999831 DOI: 10.1111/j.1365-2958.2006.05416.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Adaptation of bacterial pathogens to an intracellular environment requires resetting of the expression levels of a wide range of both virulence and housekeeping genes. We investigated the possibility that changes in DNA supercoiling could modulate the expression of genes known to be important in the intracellular growth of the pathogen Salmonella enterica serovar Typhimurium. Our data show that DNA becomes relaxed when Salmonella grows in murine macrophage but not in epithelial cells, indicating that DNA supercoiling plays a role in discrimination between two types of intracellular environment. The ssrA regulatory gene within the SPI-2 pathogenicity island that is required for survival in macrophage was found to be upregulated by DNA relaxation. This enhancement of expression also required the Fis nucleoid-associated protein. Manipulating the level of the Fis protein modulated both the level of DNA supercoiling and ssrA transcription. We discuss a model of bacterial intracellular adaptation in which Fis and DNA supercoiling collaborate to fine-tune virulence gene expression.
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Affiliation(s)
- Tadhg O Cróinín
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Ireland
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Koprivnjak T, Mlakar V, Swanson L, Fournier B, Peschel A, Weiss JP. Cation-induced transcriptional regulation of the dlt operon of Staphylococcus aureus. J Bacteriol 2006; 188:3622-30. [PMID: 16672616 PMCID: PMC1482844 DOI: 10.1128/jb.188.10.3622-3630.2006] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoteichoic and wall teichoic acids (TA) are highly anionic cell envelope-associated polymers containing repeating polyglycerol/ribitol phosphate moieties. Substitution of TA with D-alanine is important for modulation of many cell envelope-dependent processes, such as activity of autolytic enzymes, binding of divalent cations, and susceptibility to innate host defenses. D-Alanylation of TA is diminished when bacteria are grown in medium containing increased NaCl concentrations, but the effects of increased salt concentration on expression of the dlt operon encoding proteins mediating D-alanylation of TA are unknown. We demonstrate that Staphylococcus aureus transcriptionally represses dlt expression in response to high concentrations of Na(+) and moderate concentrations of Mg(2+) and Ca(2+) but not sucrose. Changes in dlt mRNA are induced within 15 min and sustained for several generations of growth. Mg(2+)-induced dlt repression depends on the ArlSR two-component system. Northern blotting, reverse transcription-PCR, and SMART-RACE analyses suggest that the dlt transcript begins 250 bp upstream of the dltA start codon and includes an open reading frame immediately upstream of dltA. Chloramphenicol transacetylase transcriptional fusions indicate that a region encompassing the 171 to 325 bp upstream of dltA is required for expression and Mg(2+)-induced repression of the dlt operon in S. aureus.
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Affiliation(s)
- Tomaz Koprivnjak
- Inflammation Program, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, 52242, USA
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