1
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Podkowik M, Perault AI, Putzel G, Pountain A, Kim J, DuMont AL, Zwack EE, Ulrich RJ, Karagounis TK, Zhou C, Haag AF, Shenderovich J, Wasserman GA, Kwon J, Chen J, Richardson AR, Weiser JN, Nowosad CR, Lun DS, Parker D, Pironti A, Zhao X, Drlica K, Yanai I, Torres VJ, Shopsin B. Quorum-sensing agr system of Staphylococcus aureus primes gene expression for protection from lethal oxidative stress. eLife 2024; 12:RP89098. [PMID: 38687677 PMCID: PMC11060713 DOI: 10.7554/elife.89098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024] Open
Abstract
The agr quorum-sensing system links Staphylococcus aureus metabolism to virulence, in part by increasing bacterial survival during exposure to lethal concentrations of H2O2, a crucial host defense against S. aureus. We now report that protection by agr surprisingly extends beyond post-exponential growth to the exit from stationary phase when the agr system is no longer turned on. Thus, agr can be considered a constitutive protective factor. Deletion of agr resulted in decreased ATP levels and growth, despite increased rates of respiration or fermentation at appropriate oxygen tensions, suggesting that Δagr cells undergo a shift towards a hyperactive metabolic state in response to diminished metabolic efficiency. As expected from increased respiratory gene expression, reactive oxygen species (ROS) accumulated more in the agr mutant than in wild-type cells, thereby explaining elevated susceptibility of Δagr strains to lethal H2O2 doses. Increased survival of wild-type agr cells during H2O2 exposure required sodA, which detoxifies superoxide. Additionally, pretreatment of S. aureus with respiration-reducing menadione protected Δagr cells from killing by H2O2. Thus, genetic deletion and pharmacologic experiments indicate that agr helps control endogenous ROS, thereby providing resilience against exogenous ROS. The long-lived 'memory' of agr-mediated protection, which is uncoupled from agr activation kinetics, increased hematogenous dissemination to certain tissues during sepsis in ROS-producing, wild-type mice but not ROS-deficient (Cybb-/-) mice. These results demonstrate the importance of protection that anticipates impending ROS-mediated immune attack. The ubiquity of quorum sensing suggests that it protects many bacterial species from oxidative damage.
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Affiliation(s)
- Magdalena Podkowik
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
| | - Andrew I Perault
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Gregory Putzel
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
- Microbial Computational Genomic Core Lab, NYU Grossman School of MedicineNew YorkUnited States
| | - Andrew Pountain
- Institute for Systems Genetics; NYU Grossman School of MedicineNew YorkUnited States
| | - Jisun Kim
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical SchoolNewarkUnited States
| | - Ashley L DuMont
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
| | - Erin E Zwack
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Robert J Ulrich
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
| | - Theodora K Karagounis
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Ronald O. Perelman Department of Dermatology; NYU Grossman School of MedicineNew YorkUnited States
| | - Chunyi Zhou
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
| | - Andreas F Haag
- School of Medicine, University of St AndrewsSt AndrewsUnited Kingdom
| | - Julia Shenderovich
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Gregory A Wasserman
- Department of Surgery, Northwell Health Lenox Hill HospitalNew YorkUnited States
| | - Junbeom Kwon
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
| | - John Chen
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
| | - Anthony R Richardson
- Department of Microbiology and Molecular Genetics, University of PittsburghPittsburghUnited States
| | - Jeffrey N Weiser
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Carla R Nowosad
- Department of Pathology, NYU Grossman School of MedicineNew YorkUnited States
| | - Desmond S Lun
- Center for Computational and Integrative Biology and Department of Computer Science, Rutgers UniversityCamdenUnited States
| | - Dane Parker
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical SchoolNewarkUnited States
| | - Alejandro Pironti
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
- Microbial Computational Genomic Core Lab, NYU Grossman School of MedicineNew YorkUnited States
| | - Xilin Zhao
- State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen UniversityXiamenChina
| | - Karl Drlica
- Public Health Research Institute, New Jersey Medical School, Rutgers UniversityNew YprkUnited States
- Department of Microbiology, Biochemistry & Molecular Genetics, New Jersey Medical School, Rutgers UniversityNewarkUnited States
| | - Itai Yanai
- Institute for Systems Genetics; NYU Grossman School of MedicineNew YorkUnited States
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of MedicineNew YorkUnited States
| | - Victor J Torres
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Bo Shopsin
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
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2
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Podkowik M, Perault AI, Putzel G, Pountain A, Kim J, Dumont A, Zwack E, Ulrich RJ, Karagounis TK, Zhou C, Haag AF, Shenderovich J, Wasserman GA, Kwon J, Chen J, Richardson AR, Weiser JN, Nowosad CR, Lun DS, Parker D, Pironti A, Zhao X, Drlica K, Yanai I, Torres VJ, Shopsin B. Quorum-sensing agr system of Staphylococcus aureus primes gene expression for protection from lethal oxidative stress. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.08.544038. [PMID: 37333372 PMCID: PMC10274873 DOI: 10.1101/2023.06.08.544038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
The agr quorum-sensing system links Staphylococcus aureus metabolism to virulence, in part by increasing bacterial survival during exposure to lethal concentrations of H2O2, a crucial host defense against S. aureus. We now report that protection by agr surprisingly extends beyond post-exponential growth to the exit from stationary phase when the agr system is no longer turned on. Thus, agr can be considered a constitutive protective factor. Deletion of agr increased both respiration and fermentation but decreased ATP levels and growth, suggesting that Δagr cells assume a hyperactive metabolic state in response to reduced metabolic efficiency. As expected from increased respiratory gene expression, reactive oxygen species (ROS) accumulated more in the agr mutant than in wild-type cells, thereby explaining elevated susceptibility of Δagr strains to lethal H2O2 doses. Increased survival of wild-type agr cells during H2O2 exposure required sodA, which detoxifies superoxide. Additionally, pretreatment of S. aureus with respiration-reducing menadione protected Δagr cells from killing by H2O2. Thus, genetic deletion and pharmacologic experiments indicate that agr helps control endogenous ROS, thereby providing resilience against exogenous ROS. The long-lived "memory" of agr-mediated protection, which is uncoupled from agr activation kinetics, increased hematogenous dissemination to certain tissues during sepsis in ROS-producing, wild-type mice but not ROS-deficient (Nox2-/-) mice. These results demonstrate the importance of protection that anticipates impending ROS-mediated immune attack. The ubiquity of quorum sensing suggests that it protects many bacterial species from oxidative damage.
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Affiliation(s)
- Magdalena Podkowik
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
| | - Andrew I. Perault
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Gregory Putzel
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
- Microbial Computational Genomic Core Lab, NYU Grossman School of Medicine, New York, NY, USA
| | - Andrew Pountain
- Institute for Systems Genetics; NYU Grossman School of Medicine, New York, NY, USA
| | - Jisun Kim
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical School Cancer Center, Newark, NJ, USA
| | - Ashley Dumont
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Erin Zwack
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Robert J. Ulrich
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
| | - Theodora K. Karagounis
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Ronald O. Perelman Department of Dermatology; NYU Grossman School of Medicine, New York, NY, USA
| | - Chunyi Zhou
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
| | - Andreas F. Haag
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Julia Shenderovich
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | | | - Junbeom Kwon
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
| | - John Chen
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Anthony R. Richardson
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jeffrey N. Weiser
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Carla R. Nowosad
- Department of Pathology, NYU Grossman School of Medicine, New York, NY, USA
| | - Desmond S. Lun
- Center for Computational and Integrative Biology and Department of Computer Science, Rutgers University, Camden, NJ, USA
| | - Dane Parker
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical School Cancer Center, Newark, NJ, USA
| | - Alejandro Pironti
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
- Microbial Computational Genomic Core Lab, NYU Grossman School of Medicine, New York, NY, USA
| | - Xilin Zhao
- State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiamen, Fujian Province, China
| | - Karl Drlica
- Public Health Research Institute, New Jersey Medical School, Rutgers University, Newark, NJ, USA
- Department of Microbiology, Biochemistry & Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Itai Yanai
- Institute for Systems Genetics; NYU Grossman School of Medicine, New York, NY, USA
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA
| | - Victor J. Torres
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Bo Shopsin
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
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3
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Kuiack RC, Tuffs SW, Dufresne K, Flick R, McCormick JK, McGavin MJ. The fadXDEBA locus of Staphylococcus aureus is required for metabolism of exogenous palmitic acid and in vivo growth. Mol Microbiol 2023; 120:425-438. [PMID: 37501506 DOI: 10.1111/mmi.15131] [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: 01/20/2023] [Revised: 07/05/2023] [Accepted: 07/10/2023] [Indexed: 07/29/2023]
Abstract
In Staphylococcus aureus, genes that should confer the capacity to metabolize fatty acids by β-oxidation occur in the fadXDEBA locus, but their function has not been elucidated. Previously, incorporation into phospholipid through the fatty acid kinase FakA pathway was thought to be the only option available for S. aureus to metabolize exogenous saturated fatty acids. We now find that in S. aureus USA300, a fadX::lux reporter was repressed by glucose and induced by palmitic acid but not stearic acid, while in USA300ΔfakA basal expression was significantly elevated, and enhanced in response to both fatty acids. When cultures were supplemented with palmitic acid, palmitoyl-CoA representing the first metabolite in the β-oxidation pathway was detected in USA300, but not in a fadXDEBA deletion mutant USA300Δfad, which relative to USA300 exhibited increased incorporation of palmitic acid into phospholipid accompanied by a rapid loss of viability. USA300Δfad also exhibited significantly reduced viability in a murine tissue abscess infection model. Our data are consistent with FakA-mediated incorporation of fatty acids into phospholipid as a preferred pathway for metabolism of exogenous fatty acids, while the fad locus is critical for metabolism of palmitic acid, which is the most abundant free fatty acid in human plasma.
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Affiliation(s)
- Robert C Kuiack
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Stephen W Tuffs
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Karine Dufresne
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Robert Flick
- Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - John K McCormick
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
- Lawson Health Research Institute, London, Ontario, Canada
- Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Martin J McGavin
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
- Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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4
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Bonn CM, Rafiqullah IM, Crawford JA, Qian YM, Guthrie JL, Matuszewska M, Robinson DA, McGavin MJ. Repeated Emergence of Variant TetR Family Regulator, FarR, and Increased Resistance to Antimicrobial Unsaturated Fatty Acid among Clonal Complex 5 Methicillin-Resistant Staphylococcus aureus. Antimicrob Agents Chemother 2023; 67:e0074922. [PMID: 36744906 PMCID: PMC10019231 DOI: 10.1128/aac.00749-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Resistance-nodulation-division (RND) superfamily efflux pumps promote antibiotic resistance in Gram-negative pathogens, but their role in Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) is undocumented. However, recent in vitro selections for resistance of S. aureus to an antimicrobial fatty acid, linoleic acid, and an antibiotic, rhodomyrtone, identified H121Y and C116R substitution variants, respectively, in a TetR family regulator, FarR, promoting increased expression of the RND pump FarE. Hypothesizing that in vivo selection pressures have also promoted the emergence of FarR variants, we searched available genome data and found that strains with FarRH121Y from human and bovine hosts have emerged sporadically in clonal complexes (CCs) CC1, CC30, CC8, CC22, and CC97, whereas multiple FarR variants have occurred within CC5 hospital-associated (HA)-MRSA. Of these, FarRE160G and FarRE93EE were exclusive to CC5, while FarRC116Y, FarRP165L, and FarRG166D also occurred in nonrelated CCs, primarily from bovine hosts. Within CC5, FarRC116Y and FarRG166D strains were polyphyletic, each exhibiting two emergence events. FarRC116Y and FarRE160G were individually sufficient to confer increased expression of FarE and enhanced resistance to linoleic acid (LA). Isolates with FarRE93EE were most closely related to S. aureus N315 MRSA and exhibited increased resistance independently of FarRE93EE. Accumulation of pseudogenes and additional polymorphisms in FarRE93EE strains contributed to a multiresistance phenotype which included fosfomycin and fusidic acid resistance in addition to increased linoleic acid resistance. These findings underscore the remarkable adaptive capacity of CC5 MRSA, which includes the polyphyletic USA100 lineage of HA-MRSA that is endemic in the Western hemisphere and known for the acquisition of multiple resistance phenotypes.
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Affiliation(s)
- Camryn M. Bonn
- Department of Microbiology, University of Western Ontario, London, Ontario, Canada
| | - Iftekhar M. Rafiqullah
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - John A. Crawford
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Yi Meng Qian
- Department of Microbiology, University of Western Ontario, London, Ontario, Canada
| | - Jennifer L. Guthrie
- Department of Microbiology, University of Western Ontario, London, Ontario, Canada
- Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Marta Matuszewska
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - D. Ashley Robinson
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, Mississippi, USA
- Center for Immunology and Microbial Research, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Martin J. McGavin
- Department of Microbiology, University of Western Ontario, London, Ontario, Canada
- Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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5
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Satishkumar N, Alexander JAN, Poon R, Buggeln E, Argudín MA, Strynadka NCJ, Chatterjee SS. PBP4-mediated β-lactam resistance among clinical strains of Staphylococcus aureus. J Antimicrob Chemother 2021; 76:2268-2272. [PMID: 34151961 DOI: 10.1093/jac/dkab201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 05/24/2021] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND PBP4, a low-molecular-weight PBP in Staphylococcus aureus, is not considered to be a classical mediator of β-lactam resistance. Previous studies carried out by our group with laboratory strains of S. aureus demonstrated the ability of PBP4 to produce β-lactam resistance through mutations associated with the pbp4 promoter and/or gene. Recent studies of β-lactam-resistant clinical isolates of S. aureus have reported similar mutations associated with pbp4. OBJECTIVES To determine if pbp4-associated mutations reported among clinical strains of S. aureus mediate β-lactam resistance. METHODS The pbp4 promoters and genes bearing mutations from clinical isolates were cloned into a heterologous host. Reporter, growth and Bocillin assays were performed to assess their role in β-lactam resistance. X-ray crystallography was used to obtain acyl-enzyme intermediate structures of the WT and mutant PBP4 with nafcillin and cefoxitin. RESULTS Of the five strains that contained pbp4 promoter mutations, three strains exhibited enhanced expression of PBP4. The R200L mutation in pbp4 resulted in increased survival in the presence of the β-lactams nafcillin and cefoxitin. Further, introduction of either a promoter or a gene mutation into the genome of a WT host increased the ability of the strains to resist the action of β-lactams. The four high-resolution X-ray structures presented demonstrate the binding pose of the β-lactams tested and provide hints for further drug development. CONCLUSIONS Mutations associated with the pbp4 promoter and pbp4 gene altered protein activity and mediated β-lactam resistance among the clinically isolated strains that were studied.
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Affiliation(s)
- Nidhi Satishkumar
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, MD, USA.,Institute of Marine and Environmental Technology, Baltimore, MD, USA
| | - J Andrew N Alexander
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Raymond Poon
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, MD, USA.,Institute of Marine and Environmental Technology, Baltimore, MD, USA
| | - Emma Buggeln
- Division of HIV/AIDS, Infectious Diseases and Global Health, Department of Medicine, University of California, San Francisco, San Francisco General Hospital, San Francisco, CA, USA
| | - Maria A Argudín
- National Reference Centre for Staphylococcus aureus, Department of Microbiology, Laboratoire Hospitalier Universitaire de Bruxelles Universitair Laboratorium Brussel (LHUB-ULB), Université Libre de Bruxelles, Brussels, Belgium
| | - Natalie C J Strynadka
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Som S Chatterjee
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, MD, USA.,Institute of Marine and Environmental Technology, Baltimore, MD, USA
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6
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Abstract
Bacterial luciferase is a flavin-dependent monooxygenase which is remarkable for its distinctive feature in transforming chemical energy to photons of visible light. The bacterial luciferase catalyzes bioluminescent reaction using reduced flavin mononucleotide, long-chain aldehyde and oxygen to yield oxidized flavin, corresponding acid, water and light at λmax around 490nm. The enzyme comprises of two non-identical α and β subunits, where α subunit is a catalytic center and β subunit is crucially required for maintaining catalytic function of the α subunit. The crystal structure with FMN bound and mutagenesis studies have assigned a number of amino acid residues that are important in coordinating critical reactions and stabilizing intermediates to attain optimum reaction efficiency. The enzyme achieves monooxygenation by generating C4a-hydroperoxyflavin intermediate that later changes its protonation status to become C4a-peroxyflavin, which is necessary for the nucleophilic attacking with aldehyde substrate. The decomposing of C4a-peroxyhemiacetal produces excited C4a-hydroxyflavin and acid product. The chemical basis regrading bioluminophore generation in Lux reaction remains an inconclusive issue. However, current data can, at least, demonstrate the involvement of electron transfer to create radical molecules which is the key step in this mechanism. Lux is a self-sufficient bioluminescent system in which all substrates can be recycled and produced by a group of enzymes from the lux operon. This makes Lux distinctively advantageous over other luciferases for reporter enzyme application. The progression of understanding of Lux catalysis is beneficial to improve light emitting efficiency in order to expand the robustness of Lux application.
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7
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Yang Z, Cui Q, Zhang M, Li Z, Wang M, Xu H. A lux-based Staphylococcus aureus bioluminescence screening assay for the detection/identification of antibiotics and prediction of antibiotic mechanisms. J Antibiot (Tokyo) 2020; 73:828-836. [PMID: 32678336 DOI: 10.1038/s41429-020-0349-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Revised: 06/09/2020] [Accepted: 06/30/2020] [Indexed: 11/09/2022]
Abstract
The need for the discovery of new antibiotics and solving the antibiotic resistance problem requires rapid detection of antibiotics, identification of known antibiotics, and prediction of antibiotic mechanisms. The bacterial lux genes encode proteins that convert chemical energy into photonic energy and lead to bioluminescence. Exploiting this phenomenon, we constructed a lux-based bioluminescence system in Staphylococcus aureus by expressing lux genes under the control of stress-inducible chaperon promoters. When experiencing antibiotic stress, these constructed reporter strains showed clear bioluminescence response. Therefore, this bioluminescence screening system can be used for the detection of antibiotics in unknown chemical mixtures. Further analysis of bioluminescence response patterns showed that: (1) these bioluminescence response patterns are highly antibiotic specific and therefore can be used for rapid and cheap identification of antibiotics; and that (2) antibiotics having the same mechanism of action have similar bioluminescence patterns and therefore these patterns can be used for the prediction of mechanism for an unknown antibiotic with good sensitivity and specificity. With this bioluminescence screening assay, the discovery and analysis of new antibiotics can be promoted, which benefits in solving the antibiotic resistance problem.
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Affiliation(s)
- Zhongjun Yang
- State Key Laboratory of Microbial Technology, Qilu Hospital, Shandong University, Qingdao, 266237, Shandong, China
| | - Qingyu Cui
- State Key Laboratory of Microbial Technology, Qilu Hospital, Shandong University, Qingdao, 266237, Shandong, China
| | - Mengge Zhang
- State Key Laboratory of Microbial Technology, Qilu Hospital, Shandong University, Qingdao, 266237, Shandong, China
| | - Zhiqiang Li
- Center for Optics Research and Engineering, Shandong University, Qingdao, 266237, Shandong, China
| | - Mingyu Wang
- State Key Laboratory of Microbial Technology, Qilu Hospital, Shandong University, Qingdao, 266237, Shandong, China.
| | - Hai Xu
- State Key Laboratory of Microbial Technology, Qilu Hospital, Shandong University, Qingdao, 266237, Shandong, China.
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8
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Tuffs SW, Herfst CA, Baroja ML, Podskalniy VA, DeJong EN, Coleman CEM, McCormick JK. Regulation of toxic shock syndrome toxin‐1 by the accessory gene regulator inStaphylococcus aureusis mediated by the repressor of toxins. Mol Microbiol 2019; 112:1163-1177. [DOI: 10.1111/mmi.14353] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/15/2019] [Indexed: 12/13/2022]
Affiliation(s)
- Stephen W. Tuffs
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
| | - Christine A. Herfst
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
- Lawson Health Research Institute London Ontario Canada
| | - Miren L. Baroja
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
- Lawson Health Research Institute London Ontario Canada
| | - Vladyslav A. Podskalniy
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
| | - Erica N. DeJong
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
| | - Charlotte E. M. Coleman
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
| | - John K. McCormick
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
- Lawson Health Research Institute London Ontario Canada
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9
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DNA Binding and Sensor Specificity of FarR, a Novel TetR Family Regulator Required for Induction of the Fatty Acid Efflux Pump FarE in Staphylococcus aureus. J Bacteriol 2019; 201:JB.00602-18. [PMID: 30455282 DOI: 10.1128/jb.00602-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 11/12/2018] [Indexed: 12/18/2022] Open
Abstract
Divergent genes in Staphylococcus aureus USA300 encode the efflux pump FarE and TetR family regulator FarR, which confer resistance to antimicrobial unsaturated fatty acids. To study their regulation, we constructed USA300 ΔfarER, which exhibited a 2-fold reduction in MIC of linoleic acid. farE expressed from its native promoter on pLIfarE conferred increased resistance to USA300 but not USA300 ΔfarER Complementation of USA300 ΔfarER with pLIfarR also had no effect, whereas resistance was restored with pLIfarER or through ectopic expression of farE In electrophoretic mobility shift assays, FarR bound to three different oligonucleotide probes that each contained a TAGWTTA motif, occurring as (i) a singular motif overlapping the -10 element of the P farR promoter, (ii) in palindrome PAL1 immediately in the 3' direction of P farR , or (iii) within PAL2 upstream of the predicted P farE promoter. FarR autorepressed its expression through cooperative binding to PAL1 and the adjacent TAGWTTA motif in P farR Consistent with reports that S. aureus does not metabolize fatty acids through acyl coenzyme A (acyl-CoA) intermediates, DNA binding activity of FarR was not affected by linoleoyl-CoA. Conversely, induction of farE required fatty acid kinase FakA, which catalyzes the first metabolic step in the incorporation of unsaturated fatty acids into phospholipid. We conclude that FarR is needed to promote the expression of farE while strongly autorepressing its own expression, and our data are consistent with a model whereby FarR interacts with a FakA-dependent product of exogenous fatty acid metabolism to ensure that efflux only occurs when the metabolic capacity for incorporation of fatty acid into phospholipid is exceeded.IMPORTANCE Here, we describe the DNA binding and sensor specificity of FarR, a novel TetR family regulator (TFR) in Staphylococcus aureus Unlike the majority of TFRs that have been characterized, which function to repress a divergently transcribed gene, we find that FarR is needed to promote expression of the divergently transcribed farE gene, encoding a resistance-nodulation-division (RND) family efflux pump that is induced in response to antimicrobial unsaturated fatty acids. Induction of farE was dependent on the function of the fatty acid kinase FakA, which catalyzes the first metabolic step in the incorporation of exogenous unsaturated fatty acids into phospholipid. This represents a novel example of TFR function.
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10
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Staphylococcus aureus Uses the GraXRS Regulatory System To Sense and Adapt to the Acidified Phagolysosome in Macrophages. mBio 2018; 9:mBio.01143-18. [PMID: 30018109 PMCID: PMC6050959 DOI: 10.1128/mbio.01143-18] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Macrophages are critical to innate immunity due to their ability to phagocytose bacteria. The macrophage phagolysosome is a highly acidic organelle with potent antimicrobial properties, yet remarkably, ingested Staphylococcus aureus replicates within this niche. Herein we demonstrate that S. aureus requires the GraXRS regulatory system for growth within this niche, while the SaeRS and AgrAC two-component regulatory systems and the α-phenol soluble modulins are dispensable. Importantly, we find that it is exposure to acidic pH that is required for optimal growth of S. aureus inside fully acidified macrophage phagolysosomes. Exposure of S. aureus to acidic pH evokes GraS signaling, which in turn elicits an adaptive response that endows the bacteria with increased resistance to antimicrobial effectors, such as antimicrobial peptides, encountered inside macrophage phagolysosomes. Notably, pH-dependent induction of antimicrobial peptide resistance in S. aureus requires the GraS sensor kinase. GraS and MprF, a member of the GraS regulon, play an important role for bacterial survival in the acute stages of systemic infection, where in murine models of infection, S. aureus resides within liver-resident Kupffer cells. We conclude that GraXRS represents a vital regulatory system that functions to allow S. aureus to evade killing, prior to commencement of replication, within host antibacterial immune cells. S. aureus can infect any site of the body, including the microbicidal phagolysosome of the macrophage. The ability of S. aureus to infect diverse niches necessitates that the bacteria be highly adaptable. Here we show that S. aureus responds to phagolysosome acidification to evoke changes in gene expression that enable the bacteria to resist phagolysosomal killing and to promote replication. Toxin production is dispensable for this response; however, the bacteria require the sensor kinase GraS, which transduces signals in response to acidic pH. GraS is necessary for phagolysosomal replication and survival of S. aureus in the acute stage of systemic infection. Disruption of this S. aureus adaptation would render S. aureus susceptible to phagocyte restriction.
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11
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Tian XL, Salim H, Dong G, Parcells M, Li YH. The BceABRS four-component system that is essential for cell envelope stress response is involved in sensing and response to host defence peptides and is required for the biofilm formation and fitness of Streptococcus mutans. J Med Microbiol 2018; 67:874-883. [PMID: 29671721 DOI: 10.1099/jmm.0.000733] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Purpose. Streptococcus mutans is a primary cariogenic pathogen worldwide. In dental biofilms, S. mutans often faces life-threatening insults, such as killing by antimicrobial compounds from competing species and from the host. How such insults affect the physiology and virulence of S. mutans is poorly understood. In this study, we explored this question by investigating the responses of S. mutans strains to several host defence peptides and bacitracin.Methodology. S. mutans UA159 and its isogenic mutants, SmΔbceA, SmΔbceB, SmΔbceR and SmΔbceS, were examined for their antibiotic susceptibility and biofilm formation. The lux reporter strains were constructed to assay the responses of S. mutans to host defence peptides. In addition, the competitive fitness of these mutants against the parent in response to peptide antibiotics was determined in dual-strain mixed cultures.Results. S. mutans UA159 (WT) was generally insensitive to physiological concentrations of α-defensin-1, β-defensin-3, LL-37 and histatin-5, but all of the BceABRS mutants were sensitive to these peptide antibiotics. The response of S. mutans to these peptide antibiotics involved the transcriptional activation of the bceABRS operon itself. Bacitracin or β-defensin-3 at a sub-inhibitory concentration induced biofilm formation in the parent, but not in any of the BceABRS mutants. None of the mutants were able to compete with the parent for persistence in duel-strain cultures in the presence of bacitracin or β-defensin-3.Conclusion. The BceABRS four-component system in S. mutans is involved in sensing, response and resistance to host defence peptides, and is required for the biofilm formation and fitness of S. mutans.
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Affiliation(s)
- Xiao-Lin Tian
- Department of Applied Oral Sciences, Dalhousie University, Halifax, NS B3H 1W2, Canada
| | - Hasan Salim
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 1W2, Canada
| | - Gaofeng Dong
- Department of Applied Oral Sciences, Dalhousie University, Halifax, NS B3H 1W2, Canada
| | - Madison Parcells
- Department of Applied Oral Sciences, Dalhousie University, Halifax, NS B3H 1W2, Canada
| | - Yung-Hua Li
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 1W2, Canada.,Department of Applied Oral Sciences, Dalhousie University, Halifax, NS B3H 1W2, Canada
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12
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Johnston T, Van Tyne D, Chen RF, Fawzi NL, Kwon B, Kelso MJ, Gilmore MS, Mylonakis E. Propyl-5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-carbodithioate (HMPC): a new bacteriostatic agent against methicillin-resistant Staphylococcus aureus. Sci Rep 2018; 8:7062. [PMID: 29728636 PMCID: PMC5935714 DOI: 10.1038/s41598-018-25571-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 04/20/2018] [Indexed: 01/03/2023] Open
Abstract
The emergence of Staphylococcus aureus strains resistant to ‘last resort’ antibiotics compels the development of new antimicrobials against this important human pathogen. We found that propyl 5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-carbodithioate (HMPC) shows bacteriostatic activity against S. aureus (MIC = 4 μg/ml) and rescues Caenorhabditis elegans from S. aureus infection. Whole-genome sequencing of S. aureus mutants resistant to the compound, along with screening of a S. aureus promoter-lux reporter array, were used to explore possible mechanisms of action. All mutants resistant to HMPC acquired missense mutations at distinct codon positions in the global transcriptional regulator mgrA, followed by secondary mutations in the phosphatidylglycerol lysyltransferase fmtC/mprF. The S. aureus promoter-lux array treated with HMPC displayed a luminescence profile that was unique but showed similarity to DNA-damaging agents and/or DNA replication inhibitors. Overall, HMPC is a new anti-staphylococcal compound that appears to act via an unknown mechanism linked to the global transcriptional regulator MgrA.
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Affiliation(s)
- Tatiana Johnston
- Department of Infectious Disease, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Daria Van Tyne
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA.,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Roy F Chen
- Department of Infectious Disease, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Nicolas L Fawzi
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, Rhode Island, USA
| | - Bumsup Kwon
- Department of Neurology, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Michael J Kelso
- School of Chemistry and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Michael S Gilmore
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA.,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Eleftherios Mylonakis
- Department of Infectious Disease, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, USA.
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13
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Kaiser JC, King AN, Grigg JC, Sheldon JR, Edgell DR, Murphy MEP, Brinsmade SR, Heinrichs DE. Repression of branched-chain amino acid synthesis in Staphylococcus aureus is mediated by isoleucine via CodY, and by a leucine-rich attenuator peptide. PLoS Genet 2018; 14:e1007159. [PMID: 29357354 PMCID: PMC5794164 DOI: 10.1371/journal.pgen.1007159] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 02/01/2018] [Accepted: 12/18/2017] [Indexed: 01/06/2023] Open
Abstract
Staphylococcus aureus requires branched-chain amino acids (BCAAs; isoleucine, leucine, valine) for protein synthesis, branched-chain fatty acid synthesis, and environmental adaptation by responding to their availability via the global transcriptional regulator CodY. The importance of BCAAs for S. aureus physiology necessitates that it either synthesize them or scavenge them from the environment. Indeed S. aureus uses specialized transporters to scavenge BCAAs, however, its ability to synthesize them has remained conflicted by reports that it is auxotrophic for leucine and valine despite carrying an intact BCAA biosynthetic operon. In revisiting these findings, we have observed that S. aureus can engage in leucine and valine synthesis, but the level of BCAA synthesis is dependent on the BCAA it is deprived of, leading us to hypothesize that each BCAA differentially regulates the biosynthetic operon. Here we show that two mechanisms of transcriptional repression regulate the level of endogenous BCAA biosynthesis in response to specific BCAA availability. We identify a trans-acting mechanism involving isoleucine-dependent repression by the global transcriptional regulator CodY and a cis-acting leucine-responsive attenuator, uncovering how S. aureus regulates endogenous biosynthesis in response to exogenous BCAA availability. Moreover, given that isoleucine can dominate CodY-dependent regulation of BCAA biosynthesis, and that CodY is a global regulator of metabolism and virulence in S. aureus, we extend the importance of isoleucine availability for CodY-dependent regulation of other metabolic and virulence genes. These data resolve the previous conflicting observations regarding BCAA biosynthesis, and reveal the environmental signals that not only induce BCAA biosynthesis, but that could also have broader consequences on S. aureus environmental adaptation and virulence via CodY.
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Affiliation(s)
- Julienne C. Kaiser
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Alyssa N. King
- Department of Biology, Georgetown University, Washington, DC, United States of America
| | - Jason C. Grigg
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jessica R. Sheldon
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - David R. Edgell
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | - Michael E. P. Murphy
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Shaun R. Brinsmade
- Department of Biology, Georgetown University, Washington, DC, United States of America
- Department of Microbiology and Immunology, Georgetown University, Washington, DC, United States of America
| | - David E. Heinrichs
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
- * E-mail:
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14
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PBP4 Mediates β-Lactam Resistance by Altered Function. Antimicrob Agents Chemother 2017; 61:AAC.00932-17. [PMID: 28807923 DOI: 10.1128/aac.00932-17] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 08/08/2017] [Indexed: 11/20/2022] Open
Abstract
Penicillin binding protein 4 (PBP4) can provide high-level β-lactam resistance in Staphylococcus aureus A series of missense and promoter mutations associated with pbp4 were detected in strains that displayed high-level resistance. We show here that the missense mutations facilitate the β-lactam resistance mediated by PBP4 and the promoter mutations lead to overexpression of pbp4 Our results also suggest a cooperative interplay among PBPs for β-lactam resistance.
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15
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Scornec H, Bellanger X, Guilloteau H, Groshenry G, Merlin C. Inducibility of Tn916 conjugative transfer in Enterococcus faecalis by subinhibitory concentrations of ribosome-targeting antibiotics. J Antimicrob Chemother 2017; 72:2722-2728. [DOI: 10.1093/jac/dkx202] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 05/29/2017] [Indexed: 11/13/2022] Open
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16
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DNA Targeting as a Likely Mechanism Underlying the Antibacterial Activity of Synthetic Bis-Indole Antibiotics. Antimicrob Agents Chemother 2016; 60:7067-7076. [PMID: 27620482 DOI: 10.1128/aac.00309-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 09/04/2016] [Indexed: 02/07/2023] Open
Abstract
We previously reported the synthesis and biological activity of a series of cationic bis-indoles with potent, broad-spectrum antibacterial properties. Here, we describe mechanism of action studies to test the hypothesis that these compounds bind to DNA and that this target plays an important role in their antibacterial outcome. The results reported here indicate that the bis-indoles bind selectively to DNA at A/T-rich sites, which is correlated with the inhibition of DNA and RNA synthesis in representative Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) organisms. Further, exposure of E. coli and S. aureus to representative bis-indoles resulted in induction of the DNA damage-inducible SOS response. In addition, the bis-indoles were found to be potent inhibitors of cell wall biosynthesis; however, they do not induce the cell wall stress stimulon in S. aureus, suggesting that this pathway is inhibited by an indirect mechanism. In light of these findings, the most likely basis for the observed activities of these compounds is their ability to bind to the minor groove of DNA, resulting in the inhibition of DNA and RNA synthesis and other secondary effects.
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17
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Kaiser JC, Sen S, Sinha A, Wilkinson BJ, Heinrichs DE. The role of two branched-chain amino acid transporters in Staphylococcus aureus growth, membrane fatty acid composition and virulence. Mol Microbiol 2016; 102:850-864. [PMID: 27589208 DOI: 10.1111/mmi.13495] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/31/2016] [Indexed: 12/24/2022]
Abstract
The branched-chain amino acids (BCAAs) are vital to both growth and virulence of the human pathogen Staphylococcus aureus. In addition to supporting protein synthesis, the BCAAs serve as precursors for branched-chain fatty acids (BCFAs), which are predominant membrane fatty acids, and, in association with the global regulatory protein CodY, the BCAAs are key co-regulators of virulence factors. Despite these critical functions, S. aureus represses Leu and Val synthesis, instead preferring to acquire them from the extracellular milieu. We previously identified BrnQ1 as a BCAA transporter, yet a brnQ1 mutant remained capable of BCAA acquisition. Here, we describe BcaP as an additional BCAA transporter, and determine that it plays a secondary role to BrnQ1 during S. aureus growth in a chemically defined medium. Furthermore, membrane fatty acid composition analysis revealed that BrnQ1, and not BcaP, is required for transporting Leu and Val to be used for iso-BCFA synthesis. Despite a predominant role for BrnQ1 in vitro, both BrnQ1 and BcaP are required for S. aureus fitness in vivo in a hematogenous spread infection model and a nasal colonisation model. These data demonstrate the importance of BrnQ1 and BcaP for growth, environmental adaptation and virulence of S. aureus.
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Affiliation(s)
- Julienne C Kaiser
- Department of Microbiology and Immunology, University of Western Ontario, London, ON, Canada
| | - Suranjana Sen
- School of Biological Sciences, Illinois State University, Normal, IL, USA
| | - Anshul Sinha
- Department of Microbiology and Immunology, University of Western Ontario, London, ON, Canada
| | - Brian J Wilkinson
- School of Biological Sciences, Illinois State University, Normal, IL, USA
| | - David E Heinrichs
- Department of Microbiology and Immunology, University of Western Ontario, London, ON, Canada
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18
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The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus. J Bacteriol 2016; 198:2732-42. [PMID: 27457715 DOI: 10.1128/jb.00425-16] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 07/18/2016] [Indexed: 01/04/2023] Open
Abstract
UNLABELLED Toxic shock syndrome toxin 1 (TSST-1) is a Staphylococcus aureus superantigen that has been implicated in both menstrual and nonmenstrual toxic shock syndrome (TSS). Despite the important role of TSST-1 in severe human disease, a comprehensive understanding of staphylococcal regulatory factors that control TSST-1 expression remains incomplete. The S. aureus exotoxin expression (Sae) operon contains a well-characterized two-component system that regulates a number of important exotoxins in S. aureus, although regulation of TSST-1 by the Sae system has not been investigated. We generated a defined deletion mutant of the Sae histidine kinase sensor (saeS) in the prototypic menstrual TSS strain S. aureus MN8. Mutation of saeS resulted in a complete loss of TSST-1 expression. Using both luciferase reporter experiments and quantitative real-time PCR, we demonstrate that the Sae system is an important transcriptional activator of TSST-1 expression. Recombinant SaeR was able to bind directly to the tst promoter to a region containing two SaeR consensus binding sites. Although the stand-alone SarA transcriptional regulator has been shown to be both a positive and a negative regulator of TSST-1, deletion of sarA in S. aureus MN8 resulted in a dramatic overexpression of TSST-1. As expected, mutation of agr also reduced TSST-1 expression, but this phenotype appeared to be independent of Sae. A double mutation of saeS and sarA resulted in the loss of TSST-1 expression. This work indicates that the Sae system is a dominant and direct transcriptional activator that is required for expression of TSST-1. IMPORTANCE The TSST-1 superantigen is an exotoxin, produced by some strains of S. aureus, that has a clear role in both menstrual and nonmenstrual TSS. Although the well-characterized agr quorum sensing system is a known positive regulator of TSST-1, the molecular mechanisms that directly control TSST-1 expression are only partially understood. Our studies demonstrate that the Sae two-component regulatory system is a positive transcriptional regulator that binds directly to the TSST-1 promoter, and furthermore, our data suggest that Sae is required for expression of TSST-1. This work highlights how major regulatory circuits can converge to fine-tune exotoxin expression and suggests that the Sae regulatory system may be an important target for antivirulence strategies.
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19
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Bertram R. Complementation Plasmids, Inducible Gene-Expression Systems, and Reporters for Staphylococci. Methods Mol Biol 2016; 1373:25-32. [PMID: 25646605 DOI: 10.1007/7651_2014_181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
A cornucopia of methods and molecular tools is available for genetic modification of staphylococci, as shown for at least ten different species to date (Prax et al. Microbiology 159:421-435, 2013). This chapter reviews a number of frequently used vectors for complementation purposes that usually replicate in E. coli and staphylococci and differ in parameters including copy number, mode of replication, and sequence length. Systems for the artificial control of gene expression are described that are modulated by low-molecular-weight effectors such as metal cations, carbohydrates, and antibiotics. Finally, the usefulness of reporter proteins that exhibit enzymatic or autofluorescent characteristics in staphylococci is highlighted.
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Affiliation(s)
- Ralph Bertram
- Department of Microbial Genetics, Faculty of Science, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Waldhäuser Str. 70/8, 72076, Tübingen, Germany. .,, Ernst-Simon-Str. 2-4, 72072, Tübingen, Germany.
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20
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Wilde AD, Snyder DJ, Putnam NE, Valentino MD, Hammer ND, Lonergan ZR, Hinger SA, Aysanoa EE, Blanchard C, Dunman PM, Wasserman GA, Chen J, Shopsin B, Gilmore MS, Skaar EP, Cassat JE. Bacterial Hypoxic Responses Revealed as Critical Determinants of the Host-Pathogen Outcome by TnSeq Analysis of Staphylococcus aureus Invasive Infection. PLoS Pathog 2015; 11:e1005341. [PMID: 26684646 PMCID: PMC4684308 DOI: 10.1371/journal.ppat.1005341] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 11/23/2015] [Indexed: 12/11/2022] Open
Abstract
Staphylococcus aureus is capable of infecting nearly every organ in the human body. In order to infiltrate and thrive in such diverse host tissues, staphylococci must possess remarkable flexibility in both metabolic and virulence programs. To investigate the genetic requirements for bacterial survival during invasive infection, we performed a transposon sequencing (TnSeq) analysis of S. aureus during experimental osteomyelitis. TnSeq identified 65 genes essential for staphylococcal survival in infected bone and an additional 148 mutants with compromised fitness in vivo. Among the loci essential for in vivo survival was SrrAB, a staphylococcal two-component system previously reported to coordinate hypoxic and nitrosative stress responses in vitro. Healthy bone is intrinsically hypoxic, and intravital oxygen monitoring revealed further decreases in skeletal oxygen concentrations upon S. aureus infection. The fitness of an srrAB mutant during osteomyelitis was significantly increased by depletion of neutrophils, suggesting that neutrophils impose hypoxic and/or nitrosative stresses on invading bacteria. To more globally evaluate staphylococcal responses to changing oxygenation, we examined quorum sensing and virulence factor production in staphylococci grown under aerobic or hypoxic conditions. Hypoxic growth resulted in a profound increase in quorum sensing-dependent toxin production, and a concomitant increase in cytotoxicity toward mammalian cells. Moreover, aerobic growth limited quorum sensing and cytotoxicity in an SrrAB-dependent manner, suggesting a mechanism by which S. aureus modulates quorum sensing and toxin production in response to environmental oxygenation. Collectively, our results demonstrate that bacterial hypoxic responses are key determinants of the staphylococcal-host interaction.
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Affiliation(s)
- Aimee D. Wilde
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Daniel J. Snyder
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Nicole E. Putnam
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Michael D. Valentino
- Departments of Ophthalmology and Microbiology and Immunology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Neal D. Hammer
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Zachery R. Lonergan
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Scott A. Hinger
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Esar E. Aysanoa
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Catlyn Blanchard
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Paul M. Dunman
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Gregory A. Wasserman
- Departments of Medicine and Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - John Chen
- Skirball Institute Program in Molecular Pathogenesis, Departments of Microbiology and Medicine, New York University Medical Center, New York, New York, United States of America
| | - Bo Shopsin
- Departments of Medicine and Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - Michael S. Gilmore
- Departments of Ophthalmology and Microbiology and Immunology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Eric P. Skaar
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Veterans Affairs Tennessee Valley Healthcare Services, Nashville, Tennessee, United States of America
| | - James E. Cassat
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- * E-mail:
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21
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Laakso HA, Marolda CL, Pinter TB, Stillman MJ, Heinrichs DE. A Heme-responsive Regulator Controls Synthesis of Staphyloferrin B in Staphylococcus aureus. J Biol Chem 2015; 291:29-40. [PMID: 26534960 DOI: 10.1074/jbc.m115.696625] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Indexed: 11/06/2022] Open
Abstract
Staphylococcus aureus possesses a multitude of mechanisms by which it can obtain iron during growth under iron starvation conditions. It expresses an effective heme acquisition system (the iron-regulated surface determinant system), it produces two carboxylate-type siderophores staphyloferrin A and staphyloferrin B (SB), and it expresses transporters for many other siderophores that it does not synthesize. The ferric uptake regulator protein regulates expression of genes encoding all of these systems. Mechanisms of fine-tuning expression of iron-regulated genes, beyond simple iron regulation via ferric uptake regulator, have not been uncovered in this organism. Here, we identify the ninth gene of the sbn operon, sbnI, as encoding a ParB/Spo0J-like protein that is required for expression of genes in the sbn operon from sbnD onward. Expression of sbnD-I is drastically decreased in an sbnI mutant, and the mutant does not synthesize detectable SB during early phases of growth. Thus, SB-mediated iron acquisition is impaired in an sbnI mutant strain. We show that the protein forms dimers and tetramers in solution and binds to DNA within the sbnC coding region. Moreover, we show that SbnI binds heme and that heme-bound SbnI does not bind DNA. Finally, we show that providing exogenous heme to S. aureus growing in an iron-free medium results in delayed synthesis of SB. This is the first study in S. aureus that identifies a DNA-binding regulatory protein that senses heme to control gene expression for siderophore synthesis.
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Affiliation(s)
| | | | | | | | - David E Heinrichs
- From the Departments of Microbiology and Immunology and Centre for Human Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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Identification and characterization of SMU.244 encoding a putative undecaprenyl pyrophosphate phosphatase protein required for cell wall biosynthesis and bacitracin resistance in Streptococcus mutans. Microbiology (Reading) 2015. [DOI: 10.1099/mic.0.000142] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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23
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Abstract
Type I signal peptidase (SPase) is essential for viability in wild-type bacteria because the terminal step of the bacterial general secretory pathway requires its proteolytic activity to release proteins from their membrane-bound N-terminal leader sequences after translocation across the cytoplasmic membrane. Here, we identify the Staphylococcus aureus operon ayrRABC (SA0337 to SA0340) and show that once released from repression by AyrR, the protein products AyrABC together confer resistance to the SPase inhibitor arylomycin M131 by providing an alternate and novel method of releasing translocated proteins. Thus, the derepression of ayrRABC allows cells to bypass the essentiality of SPase. We demonstrate that AyrABC functionally complements SPase by mediating the processing of the normally secreted proteins, albeit in some cases with reduced efficiency and either without cleavage or via cleavage at a site N-terminal to the canonical SPase cleavage site. Thus, ayrRABC encodes a secretion stress-inducible alternate terminal step of the general secretory pathway. IMPORTANCE : Addressing proteins for proper localization within or outside a cell in both eukaryotes and prokaryotes is often accomplished with intrinsic signals which mediate membrane translocation and which ultimately must be removed. The canonical enzyme responsible for the removal of translocation signals is bacterial type I signal peptidase (SPase), which functions at the terminal step of the general secretory pathway and is thus essential in wild-type bacteria. Here, we identify a four-gene operon in S. aureus that encodes an alternate terminal step of the general secretory pathway and thus makes SPase nonessential. The results have important implications for protein secretion in bacteria and potentially for protein trafficking in prokaryotes and eukaryotes in general.
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Inducible Expression of a Resistance-Nodulation-Division-Type Efflux Pump in Staphylococcus aureus Provides Resistance to Linoleic and Arachidonic Acids. J Bacteriol 2015; 197:1893-905. [PMID: 25802299 DOI: 10.1128/jb.02607-14] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2014] [Accepted: 03/17/2015] [Indexed: 12/22/2022] Open
Abstract
UNLABELLED Although Staphylococcus aureus is exposed to antimicrobial fatty acids on the skin, in nasal secretions, and in abscesses, a specific mechanism of inducible resistance to this important facet of innate immunity has not been identified. Here, we have sequenced the genome of S. aureus USA300 variants selected for their ability to grow at an elevated concentration of linoleic acid. The fatty acid-resistant clone FAR7 had a single nucleotide polymorphism resulting in an H₁₂₁Y substitution in an uncharacterized transcriptional regulator belonging to the AcrR family, which was divergently transcribed from a gene encoding a member of the resistance-nodulation-division superfamily of multidrug efflux pumps. We named these genes farR and farE, for regulator and effector of fatty acid resistance, respectively. Several lines of evidence indicated that FarE promotes efflux of antimicrobial fatty acids and is regulated by FarR. First, expression of farE was strongly induced by arachidonic and linoleic acids in an farR-dependent manner. Second, an H₁₂₁Y substitution in FarR resulted in increased expression of farE and was alone sufficient to promote increased resistance of S. aureus to linoleic acid. Third, inactivation of farE resulted in a significant reduction in the inducible resistance of S. aureus to the bactericidal activity of 100 μM linoleic acid, increased accumulation of [(14)C]linoleic acid by growing cells, and severely impaired growth in the presence of nonbactericidal concentrations of linoleic acid. Cumulatively, these findings represent the first description of a specific mechanism of inducible resistance to antimicrobial fatty acids in a Gram-positive pathogen. IMPORTANCE Staphylococcus aureus colonizes approximately 25% of humans and is a leading cause of human infectious morbidity and mortality. To persist on human hosts, S. aureus must have intrinsic defense mechanisms to cope with antimicrobial fatty acids, which comprise an important component of human innate defense mechanisms. We have identified a novel pair of genes, farR and farE, that constitute a dedicated regulator and effector of S. aureus resistance to linoleic and arachidonic acids, which are major fatty acids in human membrane phospholipid. Expression of farE, which encodes an efflux pump, is induced in an farR-dependent mechanism, in response to these antimicrobial fatty acids that would be encountered in a tissue abscess.
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Involvement of major facilitator superfamily proteins SfaA and SbnD in staphyloferrin secretion in Staphylococcus aureus. FEBS Lett 2015; 589:730-7. [PMID: 25680529 DOI: 10.1016/j.febslet.2015.02.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 01/31/2015] [Accepted: 02/02/2015] [Indexed: 12/11/2022]
Abstract
A paucity of information exists concerning the mechanism(s) by which bacteria secrete siderophores into the extracellular compartment. We investigated the role of SfaA and SbnD, two major facilitator superfamily (MFS)-type efflux proteins, in the secretion of the Staphylococcus aureus siderophores staphyloferrin A (SA) and staphyloferrin B (SB), respectively. Deletion of sfaA resulted in a drastic reduction of SA secreted into the supernatant with a corresponding accumulation of SA in the cytoplasm and a significant growth defect in cells devoid of SB synthesis. In contrast, sbnD mutants showed transiently lowered levels of secreted SB, suggesting the involvement of additional efflux mechanisms.
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Quave CL, Horswill AR. Flipping the switch: tools for detecting small molecule inhibitors of staphylococcal virulence. Front Microbiol 2014; 5:706. [PMID: 25566220 PMCID: PMC4264471 DOI: 10.3389/fmicb.2014.00706] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 11/27/2014] [Indexed: 11/25/2022] Open
Abstract
Through the expression of the accessory gene regulator quorum sensing cascade, Staphylococcus aureus is able to produce an extensive array of enzymes, hemolysins and immunomodulators essential to its ability to spread through the host tissues and cause disease. Many have argued for the discovery and development of quorum sensing inhibitors (QSIs) to augment existing antibiotics as adjuvant therapies. Here, we discuss the state-of-the-art tools that can be used to conduct screens for the identification of such QSIs. Examples include fluorescent reporters, MS-detection of autoinducing peptide production, agar plate methods for detection of hemolysins and lipase, High performance liquid chromatography-detection of hemolysins from supernatants, and cell-toxicity assays for detecting damage (or relief thereof) against human keratinocyte cells. In addition to providing a description of these various approaches, we also discuss their amenability to low-, medium-, and high-throughput screening efforts for the identification of novel QSIs.
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Affiliation(s)
- Cassandra L Quave
- Department of Dermatology, Emory University School of Medicine Atlanta, GA, USA ; Center for the Study of Human Health, Emory University College of Arts and Sciences Atlanta, GA, USA
| | - Alexander R Horswill
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa Iowa City, IA, USA
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Dinjaski N, Suri S, Valle J, Lehman SM, Lasa I, Prieto MA, García AJ. Near-infrared fluorescence imaging as an alternative to bioluminescent bacteria to monitor biomaterial-associated infections. Acta Biomater 2014; 10:2935-44. [PMID: 24632360 DOI: 10.1016/j.actbio.2014.03.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 02/13/2014] [Accepted: 03/04/2014] [Indexed: 11/28/2022]
Abstract
Biomaterial-associated infection is one of the most common complications related to the implantation of any biomedical device. Several in vivo imaging platforms have emerged as powerful diagnostic tools to longitudinally monitor biomaterial-associated infections in small animal models. In this study, we directly compared two imaging approaches: bacteria engineered to produce luciferase to generate bioluminescence and reactive oxygen species (ROS) imaging of the inflammatory response associated with the infected implant. We performed longitudinal imaging of bioluminescence associated with bacteria strains expressing plasmid-integrated luciferase driven by different promoters or a strain with the luciferase gene integrated into the chromosome. These luminescent strains provided an adequate signal for acute (0-4 days) monitoring of the infection, but the bioluminescence signal decreased over time and leveled off at 7 days post-implantation. This loss in the bioluminescence signal was attributed to changes in the metabolic activity of the bacteria. In contrast, near-infrared fluorescence imaging of ROS associated with inflammation to the implant provided sensitive and dose-dependent signals of biomaterial-associated bacteria. ROS imaging exhibited higher sensitivity than the bioluminescence imaging and was independent of the bacteria strain. Near-infrared fluorescence imaging of inflammatory responses represents a powerful alternative to bioluminescence imaging for monitoring biomaterial-associated bacterial infections.
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Affiliation(s)
- Nina Dinjaski
- Centro de Investigaciones Biológicas, CSIC, Madrid 28040, Spain
| | - Shalu Suri
- Woodruff School of Mechanical Engineering and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA
| | - Jaione Valle
- Instituto de Agrobiotecnología, UPNA-CSIC-Gobierno de Navarra, 31006 Pamplona, Spain
| | - Susan M Lehman
- Woodruff School of Mechanical Engineering and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA
| | - Iñigo Lasa
- Instituto de Agrobiotecnología, UPNA-CSIC-Gobierno de Navarra, 31006 Pamplona, Spain
| | | | - Andrés J García
- Woodruff School of Mechanical Engineering and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA.
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Abstract
The ability to genetically manipulate bacteria is essential to understanding gene/protein function in these organisms. While basic cloning has become routine in molecular biology, many still view the ability to make directed mutations as a daunting or intimidating task. To aid the staphylococcal research community, the goal of this treatise is to describe the method of allelic exchange using temperature-sensitive plasmids that we have used to successfully produce a variety of mutations including single nucleotide changes in the Staphylococcus aureus chromosome. In addition, this chapter provides extensive summaries to aid in the construction of mutations, complementation plasmids, as well as transcription and translation reporters.
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Affiliation(s)
- Jeffrey L Bose
- Department of Pathology and Microbiology, Center for Staphylococcal Research, University of Nebraska Medical Center, Omaha, NE, USA
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Prax M, Lee CY, Bertram R. An update on the molecular genetics toolbox for staphylococci. MICROBIOLOGY-SGM 2013; 159:421-435. [PMID: 23378573 PMCID: PMC3709823 DOI: 10.1099/mic.0.061705-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Staphylococci are Gram-positive spherical bacteria of enormous clinical and biotechnological relevance. Staphylococcus aureus has been extensively studied as a model pathogen. A plethora of methods and molecular tools has been developed for genetic modification of at least ten different staphylococcal species to date. Here we review recent developments of various genetic tools and molecular methods for staphylococcal research, which include reporter systems and vectors for controllable gene expression, gene inactivation, gene essentiality testing, chromosomal integration and transposon delivery. It is furthermore illustrated how mutant strain construction by homologous or site-specific recombination benefits from sophisticated counterselection methods. The underlying genetic components have been shown to operate in wild-type staphylococci or modified chassis strains. Finally, possible future developments in the field of applied Staphylococcus genetics are highlighted.
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Affiliation(s)
- Marcel Prax
- Department of Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), Faculty of Science, University of Tübingen, Waldhäuser Str. 70/8, 72076 Tübingen, Germany
| | - Chia Y Lee
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Slot 511, Little Rock, AR 72205, USA
| | - Ralph Bertram
- Department of Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), Faculty of Science, University of Tübingen, Waldhäuser Str. 70/8, 72076 Tübingen, Germany
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Influence of the vaginal microbiota on toxic shock syndrome toxin 1 production by Staphylococcus aureus. Appl Environ Microbiol 2013; 79:1835-42. [PMID: 23315732 DOI: 10.1128/aem.02908-12] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Menstrual toxic shock syndrome (TSS) is a serious illness that afflicts women of premenopausal age worldwide and arises from vaginal infection by Staphylococcus aureus and concurrent production of toxic shock syndrome toxin-1 (TSST-1). Studies have illustrated the capacity of lactobacilli to reduce S. aureus virulence, including the capacity to suppress TSST-1. We hypothesized that an aberrant microbiota characteristic of pathogenic bacteria would induce the increased production of TSST-1 and that this might represent a risk factor for the development of TSS. A S. aureus TSST-1 reporter strain was grown in the presence of vaginal swab contents collected from women with a clinically healthy vaginal status, women with an intermediate status, and those diagnosed with bacterial vaginosis (BV). Bacterial supernatant challenge assays were also performed to test the effects of aerobic vaginitis (AV)-associated pathogens toward TSST-1 production. While clinical samples from healthy and BV women suppressed toxin production, in vitro studies demonstrated that Streptococcus agalactiae and Enterococcus spp. significantly induced TSST-1 production, while some Lactobacillus spp. suppressed it. The findings suggest that women colonized by S. aureus and with AV, but not BV, may be more susceptible to menstrual TSS and would most benefit from prophylactic treatment.
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Cronin M, Stanton RM, Francis KP, Tangney M. Bacterial vectors for imaging and cancer gene therapy: a review. Cancer Gene Ther 2012; 19:731-40. [PMID: 22996740 DOI: 10.1038/cgt.2012.59] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The significant burden of resistance to conventional anticancer treatments in patients with advanced disease has prompted the need to explore alternative therapeutic strategies. The challenge for oncology researchers is to identify a therapy which is selective for tumors with limited toxicity to normal tissue. Engineered bacteria have the unique potential to overcome traditional therapies' limitations by specifically targeting tumors. It has been shown that bacteria are naturally capable of homing to tumors when systemically administered resulting in high levels of replication locally, either external to (non-invasive species) or within tumor cells (pathogens). Pre-clinical and clinical investigations involving bacterial vectors require relevant means of monitoring vector trafficking and levels over time, and development of bacterial-specific real-time imaging modalities are key for successful development of clinical bacterial gene delivery. This review discusses the currently available imaging technologies and the progress to date exploiting these for monitoring of bacterial gene delivery in vivo.
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Affiliation(s)
- M Cronin
- Cork Cancer Research Centre, BioSciences Institute, University College Cork, Cork, Ireland
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Burian J, Ramón-García S, Sweet G, Gómez-Velasco A, Av-Gay Y, Thompson CJ. The mycobacterial transcriptional regulator whiB7 gene links redox homeostasis and intrinsic antibiotic resistance. J Biol Chem 2011; 287:299-310. [PMID: 22069311 DOI: 10.1074/jbc.m111.302588] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Intrinsic drug resistance in Mycobacterium tuberculosis limits therapeutic options for treating tuberculosis. The mycobacterial transcriptional regulator whiB7 contributes to intrinsic resistance by activating its own expression and many drug resistance genes in response to antibiotics. To investigate whiB7 activation, we constructed a GFP reporter to monitor its expression, and we used it to investigate the whiB7 promoter and to screen our custom library of almost 600 bioactive compounds, including the majority of clinical antibiotics. Results showed whiB7 was transcribed from a promoter that was conserved across mycobacteria and other actinomycetes, including an AT-rich sequence that was likely targeted by WhiB7. Expression was induced by compounds having diverse structures and targets, independent of the ability of whiB7 to mediate resistance, and was dependent on media composition. Pretreatment with whiB7 activators resulted in clinically relevant increases in intrinsic drug resistance. Antibiotic-induced transcription was synergistically increased by the reductant dithiothreitol, an effect mirrored by a whiB7-dependent shift to a highly reduced cytoplasm reflected by the ratio of reduced/oxidized mycothiol. These data provided evidence that intrinsic resistance resulting from whiB7 activation is linked to fundamental changes in cell metabolism.
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Affiliation(s)
- Ján Burian
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada; Centre for Tuberculosis Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Santiago Ramón-García
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada; Centre for Tuberculosis Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Gaye Sweet
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada; Centre for Tuberculosis Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Anaximandro Gómez-Velasco
- Centre for Tuberculosis Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada; Department of Medicine, Division of Infectious Diseases, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Yossef Av-Gay
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada; Centre for Tuberculosis Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada; Department of Medicine, Division of Infectious Diseases, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Charles J Thompson
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada; Centre for Tuberculosis Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
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Subrt N, Mesak LR, Davies J. Modulation of virulence gene expression by cell wall active antibiotics in Staphylococcus aureus. J Antimicrob Chemother 2011; 66:979-84. [PMID: 21393149 DOI: 10.1093/jac/dkr043] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES To investigate the effect of subinhibitory concentrations of cell wall active antibiotics on virulence gene expression and biofilm formation in Staphylococcus aureus Newman and in laboratory strains. METHODS Promoter regions of spa, lukE and agr RNAIII were cloned upstream of a modified luxABCDE reporter. Using disc diffusion assays, the effects of antibiotics were observed on gene expression and quantitative real-time PCR was employed to confirm the results. Assays were performed to measure biofilm formation in wild-type S. aureus and respective spa-deficient and small colony variant mutants in the presence of subinhibitory concentrations of antibiotics. RESULTS Expression of spa and lukE was stimulated by subinhibitory concentrations of penicillin and cefalotin, while agr RNAIII expression was not affected. Denser biofilms were formed by S. aureus Newman and its small colony variant in the presence of subinhibitory concentrations of cefalotin. CONCLUSIONS Subinhibitory concentrations of certain antibiotics have been shown to stimulate virulence gene expression in S. aureus; this may alter the progression of infection and thus render antimicrobial therapy unreliable. The use of appropriate combinations of antibiotics might be an approach to avoiding this situation. Promoter-lux reporters are sensitive tools for studying the modulation of transcription by antibiotic inhibitors, and could be used to predict novel therapeutic combinations for the treatment of infection.
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Affiliation(s)
- Natalia Subrt
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
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Lactobacillus reuteri-produced cyclic dipeptides quench agr-mediated expression of toxic shock syndrome toxin-1 in staphylococci. Proc Natl Acad Sci U S A 2011; 108:3360-5. [PMID: 21282650 DOI: 10.1073/pnas.1017431108] [Citation(s) in RCA: 152] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The production of the staphylococcal exotoxin toxic shock syndrome toxin-1 (TSST-1) by Staphylococcus aureus has been associated with essentially all cases of menstruation-associated toxic shock syndrome (TSS). In this work, we show that the human vaginal isolate Lactobacillus reuteri RC-14 produces small signaling molecules that are able to interfere with the staphylococcal quorum-sensing system agr, a key regulator of virulence genes, and repress the expression of TSST-1 in S. aureus MN8, a prototype of menstrual TSS S. aureus strains. Quantitative real-time PCR data showed that transcription from the Ptst promoter, as well as the P2 and P3 promoters of the agr system from all four agr subgroups of S. aureus, was strongly inhibited in response to growth with L. reuteri RC-14 cultural supernatant. Alterations in the transcriptional levels of two other virulence-associated regulators sarA and saeRS were also observed, indicating a potential overall influence of L. reuteri RC-14 signals on the production of virulence factors in S. aureus. S. aureus promoter-lux reporter strains were used to screen biochemically fractionated L. reuteri RC-14 supernatant, and the cyclic dipeptides cyclo(L-Phe-L-Pro) and cyclo(L-Tyr-L-Pro) were identified as the signaling molecules. The results from this work contribute to a better understanding of interspecies cell-to-cell communication between Lactobacillus and Staphylococcus, and provide a unique mechanism by which endogenous or probiotic strains may attenuate virulence factor production by bacterial pathogens.
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Abstract
According to World Health Organization estimates, infectious organisms are responsible for approximately one in four deaths worldwide. Animal models play an essential role in the development of vaccines and therapeutic agents but large numbers of animals are required to obtain quantitative microbiological data by tissue sampling. Biophotonic imaging (BPI) is a highly sensitive, nontoxic technique based on the detection of visible light, produced by luciferase-catalysed reactions (bioluminescence) or by excitation of fluorescent molecules, using sensitive photon detectors. The development of bioluminescent/fluorescent microorganisms therefore allows the real-time noninvasive detection of microorganisms within intact living animals. Multiple imaging of the same animal throughout an experiment allows disease progression to be followed with extreme accuracy, reducing the number of animals required to yield statistically meaningful data. In the study of infectious disease, the use of BPI is becoming widespread due to the novel insights it can provide into established models, as well as the impact of the technique on two of the guiding principles of using animals in research, namely reduction and refinement. Here, we review the technology of BPI, from the instrumentation through to the generation of a photonic signal, and illustrate how the technique is shedding light on infection dynamics in vivo.
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Affiliation(s)
- Nuria Andreu
- Department of Medicine, Imperial College London, London, UK
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Upgrading bioluminescent bacterial bioreporter performance by splitting the lux operon. Anal Bioanal Chem 2010; 400:1071-82. [DOI: 10.1007/s00216-010-4266-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 09/28/2010] [Accepted: 09/28/2010] [Indexed: 11/25/2022]
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Mesak LR, Davies J. Phenotypic changes in ciprofloxacin-resistant Staphylococcus aureus. Res Microbiol 2009; 160:785-91. [DOI: 10.1016/j.resmic.2009.09.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 09/17/2009] [Accepted: 09/23/2009] [Indexed: 01/25/2023]
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