51
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Sawyer EB, Grabowska AD, Cortes T. Translational regulation in mycobacteria and its implications for pathogenicity. Nucleic Acids Res 2019; 46:6950-6961. [PMID: 29947784 PMCID: PMC6101614 DOI: 10.1093/nar/gky574] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 06/14/2018] [Indexed: 01/13/2023] Open
Abstract
Protein synthesis is a fundamental requirement of all cells for survival and replication. To date, vast numbers of genetic and biochemical studies have been performed to address the mechanisms of translation and its regulation in Escherichia coli, but only a limited number of studies have investigated these processes in other bacteria, particularly in slow growing bacteria like Mycobacterium tuberculosis, the causative agent of human tuberculosis. In this Review, we highlight important differences in the translational machinery of M. tuberculosis compared with E. coli, specifically the presence of two additional proteins and subunit stabilizing elements such as the B9 bridge. We also consider the role of leaderless translation in the ability of M. tuberculosis to establish latent infection and look at the experimental evidence that translational regulatory mechanisms operate in mycobacteria during stress adaptation, particularly focussing on differences in toxin-antitoxin systems between E. coli and M. tuberculosis and on the role of tuneable translational fidelity in conferring phenotypic antibiotic resistance. Finally, we consider the implications of these differences in the context of the biological adaptation of M. tuberculosis and discuss how these regulatory mechanisms could aid in the development of novel therapeutics for tuberculosis.
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Affiliation(s)
- Elizabeth B Sawyer
- Pathogen Molecular Biology Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.,TB Centre, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Anna D Grabowska
- Pathogen Molecular Biology Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.,TB Centre, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Teresa Cortes
- Pathogen Molecular Biology Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.,TB Centre, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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52
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A ParDE-family toxin antitoxin system in major resistance plasmids of Enterobacteriaceae confers antibiotic and heat tolerance. Sci Rep 2019; 9:9872. [PMID: 31285520 PMCID: PMC6614396 DOI: 10.1038/s41598-019-46318-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 06/26/2019] [Indexed: 11/16/2022] Open
Abstract
Toxin-antitoxin (TA) systems were initially discovered as plasmid addiction systems on low-copy-number plasmids. Thousands of TA loci have since been identified on chromosomes, plasmids and mobile elements in bacteria and archaea with diverse roles in bacterial physiology and in maintenance of genetic elements. Here, we identified and characterised a plasmid mediated type II TA system in Enterobacteriaceae as a member of the ParDE super family. This system (hereafter, ParDEI) is distributed among IncI and IncF-type antibiotic resistance and virulence plasmids found in avian and human-source Escherichia coli and Salmonella. It is found that ParDEI is a plasmid stability and stress response module that increases tolerance of aminoglycoside, quinolone and β-lactam antibiotics in E. coli by ~100–1,000-fold, and thus to levels beyond those achievable in the course of antibiotic therapy for human infections. ParDEI also confers a clear survival advantage at 42 °C and expression of the ParEI toxin in trans induces the SOS response, inhibits cell division and promotes biofilm formation. This transmissible high-level antibiotic tolerance is likely to be an important factor in the success of the IncI and IncF plasmids which carry it and the important pathogens in which these are resident.
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53
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Paul P, Sahu BR, Suar M. Plausible role of bacterial toxin-antitoxin system in persister cell formation and elimination. Mol Oral Microbiol 2019; 34:97-107. [PMID: 30891951 DOI: 10.1111/omi.12258] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 02/22/2019] [Accepted: 03/16/2019] [Indexed: 12/11/2022]
Abstract
Although, a large proportion of pathogenic bacteria gets eliminated from hosts after antibiotic treatment, a fraction of population confronts against such effects and undergoes growth arrest to form persisters. Persistence in bacteria is a dormant physiological state where cells escape the effects of antimicrobials as well as other host immune defences without any genetic mutations. The state of dormancy is achieved through various complex phenomena and it is known that a gene pair named as toxin-antitoxin (TA) acts as a key player of persister cell formation where the toxin is activated either stochastically or after an environmental insult, thereby silencing the physiological processes. However, the controversial role of TA modules in persister cell formation has also been documented with reasonable clarity. Persisters may revert back from state of quiescence and regrow when conditions become favourable for their propagation. Therefore, the elimination of dormant bacteria is crucial, and currently, research interest is highly focussed on developing several antipersister strategies that may kill persister bacteria by targeting different molecules. It is worth examining these targets to develop appropriate therapeutic interventions against bacterial infections and it is believed that earmarking TA system can be a novel approach for resuscitation of persisters. In this review, we discussed the role of TA modules in mediating persistence with highlighting on the debatable issues regarding contribution of these modules in dormant bacteria formation. Furthermore, we discussed if these modules in bacteria can be targeted for successful elimination of dormant persister cells.
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Affiliation(s)
- Prajita Paul
- School of Biotechnology, KIIT (Deemed to be University), Bhubaneswar, India
| | - Bikash R Sahu
- School of Biotechnology, KIIT (Deemed to be University), Bhubaneswar, India
| | - Mrutyunjay Suar
- School of Biotechnology, KIIT (Deemed to be University), Bhubaneswar, India
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54
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Song S, Guo Y, Kim JS, Wang X, Wood TK. Phages Mediate Bacterial Self-Recognition. Cell Rep 2019; 27:737-749.e4. [DOI: 10.1016/j.celrep.2019.03.070] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/07/2019] [Accepted: 03/18/2019] [Indexed: 12/26/2022] Open
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55
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Talavera A, Tamman H, Ainelo A, Konijnenberg A, Hadži S, Sobott F, Garcia-Pino A, Hõrak R, Loris R. A dual role in regulation and toxicity for the disordered N-terminus of the toxin GraT. Nat Commun 2019; 10:972. [PMID: 30814507 PMCID: PMC6393540 DOI: 10.1038/s41467-019-08865-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 01/31/2019] [Indexed: 11/09/2022] Open
Abstract
Bacterial toxin-antitoxin (TA) modules are tightly regulated to maintain growth in favorable conditions or growth arrest during stress. A typical regulatory strategy involves the antitoxin binding and repressing its own promoter while the toxin often acts as a co-repressor. Here we show that Pseudomonas putida graTA-encoded antitoxin GraA and toxin GraT differ from other TA proteins in the sense that not the antitoxin but the toxin possesses a flexible region. GraA auto-represses the graTA promoter: two GraA dimers bind cooperatively at opposite sides of the operator sequence. Contrary to other TA modules, GraT is a de-repressor of the graTA promoter as its N-terminal disordered segment prevents the binding of the GraT2A2 complex to the operator. Removal of this region restores operator binding and abrogates Gr aT toxicity. GraTA represents a TA module where a flexible region in the toxin rather than in the antitoxin controls operon expression and toxin activity. The Pseudomonas putida toxin GraT and antitoxin GraA form a type II toxin-antoxin module. Here the authors present the crystal structures of the GraA dimer, GraTA and GraA-DNA complexes and show that GraT contains a functionally important N-terminal intrinsic disordered region that prevents the binding of the GraTA complex to the operator.
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Affiliation(s)
- Ariel Talavera
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, B-1050, Brussel, Belgium. .,Molecular Recognition Unit, Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, B-1050, Brussel, Belgium.
| | - Hedvig Tamman
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Andres Ainelo
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Albert Konijnenberg
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, B-1050, Brussel, Belgium.,Molecular Recognition Unit, Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, B-1050, Brussel, Belgium.,Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerpen, Belgium
| | - San Hadži
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, B-1050, Brussel, Belgium.,Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Frank Sobott
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerpen, Belgium.,Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.,School of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Abel Garcia-Pino
- Biologie Structurale et Biophysique, Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, B-6041, Gosselies, Belgium
| | - Rita Hõrak
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Remy Loris
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, B-1050, Brussel, Belgium. .,Molecular Recognition Unit, Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, B-1050, Brussel, Belgium.
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56
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Wood TK, Song S, Yamasaki R. Ribosome dependence of persister cell formation and resuscitation. J Microbiol 2019; 57:213-219. [PMID: 30806978 DOI: 10.1007/s12275-019-8629-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 12/13/2018] [Accepted: 12/26/2018] [Indexed: 01/05/2023]
Abstract
Since most bacterial cells are starving, they must enter a resting stage. Persister is the term used for metabolically-dormant cells that are not spores, and these cells arise from stress such as that from antibiotics as well as that from starvation. Because of their lack of metabolism, persister cells survive exposure to multiple stresses without undergoing genetic change; i.e., they have no inherited phenotype and behave as wild-type cells once the stress is removed and nutrients are presented. In contrast, mutations allow resistant bacteria to grow in the presence of antibiotics and slow growth allows tolerant cells to withstand higher concentrations of antibiotics; hence, there are three closely-related phenotypes: persistent, resistant, and tolerant. In addition, since dormancy is so prevalent, persister cells must have a means for resuscitating (since so many cells should obtain this resting state). In this review, we focus on what is known about the formation and resuscitation of persister cells.
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Affiliation(s)
- Thomas K Wood
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, USA.
| | - Sooyeon Song
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, USA
| | - Ryota Yamasaki
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, USA
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57
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Mandal S, Njikan S, Kumar A, Early JV, Parish T. The relevance of persisters in tuberculosis drug discovery. MICROBIOLOGY-SGM 2019; 165:492-499. [PMID: 30775961 DOI: 10.1099/mic.0.000760] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Bacterial persisters are a subpopulation of cells that exhibit phenotypic resistance during exposure to a lethal dose of antibiotics. They are difficult to target and thought to contribute to the long treatment duration required for tuberculosis. Understanding the molecular and cellular biology of persisters is critical to finding new tuberculosis drugs that shorten treatment. This review focuses on mycobacterial persisters and describes the challenges they pose in tuberculosis therapy, their characteristics and formation, how persistence leads to resistance, and the current approaches being used to target persisters within mycobacterial drug discovery.
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Affiliation(s)
- Soma Mandal
- TB Discovery Research, Infectious Disease Research Institute, 1616 Eastlake Ave. E, Suite 400, Seattle, WA 98102, USA
| | - Samuel Njikan
- TB Discovery Research, Infectious Disease Research Institute, 1616 Eastlake Ave. E, Suite 400, Seattle, WA 98102, USA
| | - Anuradha Kumar
- TB Discovery Research, Infectious Disease Research Institute, 1616 Eastlake Ave. E, Suite 400, Seattle, WA 98102, USA
| | - Julie V Early
- TB Discovery Research, Infectious Disease Research Institute, 1616 Eastlake Ave. E, Suite 400, Seattle, WA 98102, USA
| | - Tanya Parish
- TB Discovery Research, Infectious Disease Research Institute, 1616 Eastlake Ave. E, Suite 400, Seattle, WA 98102, USA
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58
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Shur KV, Bekker OB, Zaichikova MV, Maslov DA, Akimova NI, Zakharevich NV, Chekalina MS, Danilenko VN. Genetic Aspects of Drug Resistance and Virulence in Mycobacterium tuberculosis. RUSS J GENET+ 2018. [DOI: 10.1134/s1022795418120141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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59
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Increased Mortality in Mice following Immunoprophylaxis Therapy with High Dosage of Nicotinamide in Burkholderia Persistent Infections. Infect Immun 2018; 87:IAI.00592-18. [PMID: 30323029 PMCID: PMC6300628 DOI: 10.1128/iai.00592-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/09/2018] [Indexed: 12/27/2022] Open
Abstract
Bacterial persistence, known as noninherited antibacterial resistance, is a factor contributing to the establishment of long-lasting chronic bacterial infections. In this study, we examined the ability of nicotinamide (NA) to potentiate the activity of different classes of antibiotics against Burkholderia thailandensis persister cells. Bacterial persistence, known as noninherited antibacterial resistance, is a factor contributing to the establishment of long-lasting chronic bacterial infections. In this study, we examined the ability of nicotinamide (NA) to potentiate the activity of different classes of antibiotics against Burkholderia thailandensis persister cells. Here we demonstrate that addition of NA in in vitro models of B. thailandensis infection resulted in a significant depletion of the persister population in response to various classes of antibiotics. We applied microfluidic bioreactors with a continuous medium flow to study the effect of supplementation with an NA gradient on the recovery of B. thailandensis persister populations. A coculture of human neutrophils preactivated with 50 µM NA and B. thailandensis resulted in the most efficient reduction in the persister population. Applying single-cell RNA fluorescence in situ hybridization analysis and quantitative PCR, we found that NA inhibited gene expression of the stringent response regulator relA, implicated in the regulation of the persister metabolic state. We also demonstrate that a therapeutic dose of NA (250 mg/kg of body weight), previously applied as immunoprophylaxis against antibiotic-resistant bacterial species, produced adverse effects in an in vivo murine model of infection with the highly pathogenic bacterium Burkholderia pseudomallei, indicating that therapeutic dose and metabolite effects have to be carefully evaluated and tailored for every case of potential clinical application.
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60
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Abstract
In this issue of Molecular Cell, Gutierrez et al. (2017) unravel a bacterial survival strategy that they term "density-dependent persistence" or DDP. The authors demonstrate that the majority of isogenic cells in bacterial populations survive lethal antibiotic doses once bacteria consume nutrients and enter stationary growth phase.
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61
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Cardoso MH, de Almeida KC, Cândido ES, Fernandes GDR, Dias SC, de Alencar SA, Franco OL. Comparative transcriptome analyses of magainin I-susceptible and -resistant Escherichia coli strains. Microbiology (Reading) 2018; 164:1383-1393. [DOI: 10.1099/mic.0.000725] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Marlon H. Cardoso
- 3S-Inova Biotech, Pós-graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande-MS, Brazil
- 2Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Universidade de Brasília, Brasília-DF, Brazil
- 1Pós-Graduação em Ciências Genômicas e Biotecnologia, Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília- DF, Brazil
| | - Keyla C. de Almeida
- 1Pós-Graduação em Ciências Genômicas e Biotecnologia, Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília- DF, Brazil
- 2Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Universidade de Brasília, Brasília-DF, Brazil
| | - Elizabete S. Cândido
- 1Pós-Graduação em Ciências Genômicas e Biotecnologia, Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília- DF, Brazil
- 3S-Inova Biotech, Pós-graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande-MS, Brazil
| | - Gabriel da R. Fernandes
- 1Pós-Graduação em Ciências Genômicas e Biotecnologia, Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília- DF, Brazil
- 4Oswaldo Cruz Foundation, René Rachou Research Center, Belo Horizonte, MG, Brazil
| | - Simoni C. Dias
- 1Pós-Graduação em Ciências Genômicas e Biotecnologia, Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília- DF, Brazil
- 5Programa de Pós Graduação em Biologia Animal, Universidade de Brasília, Brasília, Brazil
| | - Sérgio A. de Alencar
- 1Pós-Graduação em Ciências Genômicas e Biotecnologia, Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília- DF, Brazil
| | - Octávio L. Franco
- 3S-Inova Biotech, Pós-graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande-MS, Brazil
- 1Pós-Graduação em Ciências Genômicas e Biotecnologia, Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília- DF, Brazil
- 2Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Universidade de Brasília, Brasília-DF, Brazil
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62
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Slayden RA, Dawson CC, Cummings JE. Toxin-antitoxin systems and regulatory mechanisms in Mycobacterium tuberculosis. Pathog Dis 2018; 76:4969681. [PMID: 29788125 DOI: 10.1093/femspd/fty039] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 05/01/2018] [Indexed: 11/14/2022] Open
Abstract
There has been a significant reduction in annual tuberculosis incidence since the World Health Organization declared tuberculosis a global health threat. However, treatment of M. tuberculosis infections requires lengthy multidrug therapeutic regimens to achieve a durable cure. The development of new drugs that are active against resistant strains and phenotypically diverse organisms continues to present the greatest challenge in the future. Numerous phylogenomic analyses have revealed that the Mtb genome encodes a significantly expanded repertoire of toxin-antitoxin (TA) loci that makes up the Mtb TA system. A TA loci is a two-gene operon encoding a 'toxin' protein that inhibits bacterial growth and an interacting 'antitoxin' partner that neutralizes the inhibitory activity of the toxin. The presence of multiple chromosomally encoded TA loci in Mtb raises important questions in regard to expansion, regulation and function. Thus, the functional roles of TA loci in Mtb pathogenesis have received considerable attention over the last decade. The cumulative results indicate that they are involved in regulating adaptive responses to stresses associated with the host environment and drug treatment. Here we review the TA families encoded in Mtb, discuss the duplication of TA loci in Mtb, regulatory mechanism of TA loci, and phenotypic heterogeneity and pathogenesis.
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Affiliation(s)
- Richard A Slayden
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523-0922, USA
| | - Clinton C Dawson
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523-0922, USA
| | - Jason E Cummings
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523-0922, USA
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63
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Phenotypic heterogeneity: a bacterial virulence strategy. Microbes Infect 2018; 20:570-577. [DOI: 10.1016/j.micinf.2018.01.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/15/2018] [Accepted: 01/17/2018] [Indexed: 11/21/2022]
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64
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Yadav M, Rathore JS. TAome analysis of type-II toxin-antitoxin system from Xenorhabdus nematophila. Comput Biol Chem 2018; 76:293-301. [DOI: 10.1016/j.compbiolchem.2018.07.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 05/23/2018] [Accepted: 07/07/2018] [Indexed: 12/23/2022]
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65
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66
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Walling LR, Butler JS. Toxins targeting transfer RNAs: Translation inhibition by bacterial toxin-antitoxin systems. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 10:e1506. [PMID: 30296016 DOI: 10.1002/wrna.1506] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 08/07/2018] [Accepted: 08/13/2018] [Indexed: 01/09/2023]
Abstract
Prokaryotic toxin-antitoxin (TA) systems are composed of a protein toxin and its cognate antitoxin. These systems are abundant in bacteria and archaea and play an important role in growth regulation. During favorable growth conditions, the antitoxin neutralizes the toxin's activity. However, during conditions of stress or starvation, the antitoxin is inactivated, freeing the toxin to inhibit growth and resulting in dormancy. One mechanism of growth inhibition used by several TA systems results from targeting transfer RNAs (tRNAs), either through preventing aminoacylation, acetylating the primary amino group, or endonucleolytic cleavage. All of these mechanisms inhibit translation and result in growth arrest. Many of these toxins only act on a specific tRNA or a specific subset of tRNAs; however, more work is necessary to understand the specificity determinants of these toxins. For the toxins whose specificity has been characterized, both sequence and structural components of the tRNA appear important for recognition by the toxin. Questions also remain regarding the mechanisms used by dormant bacteria to resume growth after toxin induction. Rescue of stalled ribosomes by transfer-messenger RNAs, removal of acetylated amino groups from tRNAs, or ligation of cleaved RNA fragments have all been implicated as mechanisms for reversing toxin-induced dormancy. However, the mechanisms of resuming growth after induction of the majority of tRNA targeting toxins are not yet understood. This article is categorized under: Translation > Translation Regulation RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition.
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Affiliation(s)
- Lauren R Walling
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York
| | - J Scott Butler
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York.,Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York.,Center for RNA Biology, University of Rochester Medical Center, Rochester, New York
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67
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Bhaskar A, De Piano C, Gelman E, McKinney JD, Dhar N. Elucidating the role of (p)ppGpp in mycobacterial persistence against antibiotics. IUBMB Life 2018; 70:836-844. [PMID: 30092117 DOI: 10.1002/iub.1888] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 05/23/2018] [Indexed: 01/05/2023]
Abstract
Bacterial persistence, the ability of bacteria to survive high concentrations of antibiotics for extended periods of time, is an important contributing factor to therapy failure and development of chronic and recurrent infections. Several recent studies have suggested that this persistence is mediated primarily by (p)ppGpp, through its interactions with toxin-antitoxin modules and polyphosphates. In this study, we address whether these key players play a role in mycobacterial persistence against antibiotics. We targeted these specific pathways in Mycobacterium smegmatis by constructing deletion strains of (p)ppGpp synthetase/hydrolase (relA), polyphosphate kinases (ppk1 and ppk2), exopolyphosphatases (ppx1 and ppx2), and the lon protease. None of these mutant strains exhibited altered levels of persisters against isoniazid and ciprofloxacin, when compared with wild-type strain. Even under conditions in which the stringent response usually gets activated, these strains displayed wild-type persister levels. Interestingly, we also found that unlike Escherichia coli, maintaining M. smegmatis in exponential phase by repeated passaging does not eliminate persisters suggesting that at least against the antibiotics tested, stationary-phase dependent persisters (type I) are not the major contributors. Thus, our data demonstrate that multiple mechanisms of antibiotic persistence exist and that these vary widely among different bacterial species. © 2018 IUBMB Life, 70(9):836-844, 2018.
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Affiliation(s)
- Ashima Bhaskar
- Laboratory of Microbiology and Microtechnology, School of Life Sciences, Swiss Federal Institute of Technology in Lausanne (EPFL), Lausanne, Switzerland
| | - Cyntia De Piano
- Laboratory of Microbiology and Microtechnology, School of Life Sciences, Swiss Federal Institute of Technology in Lausanne (EPFL), Lausanne, Switzerland
| | - Ekaterina Gelman
- Laboratory of Microbiology and Microtechnology, School of Life Sciences, Swiss Federal Institute of Technology in Lausanne (EPFL), Lausanne, Switzerland
| | - John D McKinney
- Laboratory of Microbiology and Microtechnology, School of Life Sciences, Swiss Federal Institute of Technology in Lausanne (EPFL), Lausanne, Switzerland
| | - Neeraj Dhar
- Laboratory of Microbiology and Microtechnology, School of Life Sciences, Swiss Federal Institute of Technology in Lausanne (EPFL), Lausanne, Switzerland
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68
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Folkvardsen DB, Norman A, Andersen ÅB, Rasmussen EM, Lillebaek T, Jelsbak L. A Major Mycobacterium tuberculosis outbreak caused by one specific genotype in a low-incidence country: Exploring gene profile virulence explanations. Sci Rep 2018; 8:11869. [PMID: 30089859 PMCID: PMC6082827 DOI: 10.1038/s41598-018-30363-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 07/10/2018] [Indexed: 12/30/2022] Open
Abstract
Denmark, a tuberculosis low burden country, still experiences significant active Mycobacterium tuberculosis (Mtb) transmission, especially with one specific genotype named Cluster 2/1112-15 (C2), the most prevalent lineage in Scandinavia. In addition to environmental factors, antibiotic resistance, and human genetics, there is increasing evidence that Mtb strain variation plays a role for the outcome of infection and disease. In this study, we explore the reasons for the success of the C2 genotype by analysing strain specific polymorphisms identified through whole genome sequencing of all C2 isolates identified in Denmark between 1992 and 2014 (n = 952), and the demographic distribution of C2. Of 234 non-synonymous (NS) monomorphic SNPs found in C2 in comparison with Mtb reference strain H37Rv, 23 were in genes previously reported to be involved in Mtb virulence. Of these 23 SNPs, three were specific for C2 including a NS mutation in a gene associated with hyper-virulence. We show that the genotype is readily transmitted to different ethnicities and is also found outside Denmark. Our data suggest that strain specific virulence factor variations are important for the success of the C2 genotype. These factors, likely in combination with poor TB control, seem to be the main drivers of C2 success.
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Affiliation(s)
- Dorte Bek Folkvardsen
- International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen, Denmark.
| | - Anders Norman
- International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen, Denmark
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Åse Bengård Andersen
- Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
- Research Unit for Infectious Diseases, Department of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Erik Michael Rasmussen
- International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen, Denmark
| | - Troels Lillebaek
- International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen, Denmark
| | - Lars Jelsbak
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kgs. Lyngby, Denmark
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69
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Mechanisms of Bacterial Tolerance and Persistence in the Gastrointestinal and Respiratory Environments. Clin Microbiol Rev 2018; 31:31/4/e00023-18. [PMID: 30068737 DOI: 10.1128/cmr.00023-18] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Pathogens that infect the gastrointestinal and respiratory tracts are subjected to intense pressure due to the environmental conditions of the surroundings. This pressure has led to the development of mechanisms of bacterial tolerance or persistence which enable microorganisms to survive in these locations. In this review, we analyze the general stress response (RpoS mediated), reactive oxygen species (ROS) tolerance, energy metabolism, drug efflux pumps, SOS response, quorum sensing (QS) bacterial communication, (p)ppGpp signaling, and toxin-antitoxin (TA) systems of pathogens, such as Escherichia coli, Salmonella spp., Vibrio spp., Helicobacter spp., Campylobacter jejuni, Enterococcus spp., Shigella spp., Yersinia spp., and Clostridium difficile, all of which inhabit the gastrointestinal tract. The following respiratory tract pathogens are also considered: Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Burkholderia cenocepacia, and Mycobacterium tuberculosis Knowledge of the molecular mechanisms regulating the bacterial tolerance and persistence phenotypes is essential in the fight against multiresistant pathogens, as it will enable the identification of new targets for developing innovative anti-infective treatments.
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70
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Gall AR, Hegarty AE, Datsenko KA, Westerman RP, SanMiguel P, Csonka LN. High-level, constitutive expression of the mgtC gene confers increased thermotolerance on Salmonella enterica serovar Typhimurium. Mol Microbiol 2018; 109:327-344. [PMID: 29802740 DOI: 10.1111/mmi.13988] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/15/2018] [Indexed: 01/21/2023]
Abstract
We found that mutations that increased the transcription of the mgtCBR (Mg2+ transport-related) operon conferred increased thermotolerance on this organism. The 5' leader of the mgtCBR mRNA contains two short open reading frames (ORFs), mgtM and mgtP, whose translation regulates the expression of the mgtCBR operon by a mechanism that is similar to attenuation in amino acid biosynthetic operons. We obtained two types of mutations that resulted in elevated transcription of the operon: defects in the mgtM ribosome-binding site, impairing the translation of this ORF and deletions encompassing the stop codon of mgtM that extend the translation of this ORF across a downstream Rho termination site. These mgtM mutations give further insights into the mechanism of the transcriptional control of the mgtCBR operon that we discuss in this work. We show that the increased thermotolerance requires elevated expression of the mgtC gene, but functional mgtB and mgtR, which respectively encode an Mg2+ transporter and a regulatory protein, are dispensable for this response. MgtC has been shown to have complex functions, including a requirement for virulence, flagella-independent motility and synthesis of cellulose and we now found that it has a role in the regulation of thermotolerance.
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Affiliation(s)
- Aaron R Gall
- Department of Biological Sciences, Purdue University
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71
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Khandekar S, Liebens V, Fauvart M, Tulkens PM, Michiels J, Van Bambeke F. The Putative De- N-acetylase DnpA Contributes to Intracellular and Biofilm-Associated Persistence of Pseudomonas aeruginosa Exposed to Fluoroquinolones. Front Microbiol 2018; 9:1455. [PMID: 30042739 PMCID: PMC6048251 DOI: 10.3389/fmicb.2018.01455] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Accepted: 06/12/2018] [Indexed: 11/30/2022] Open
Abstract
Persisters are the fraction of antibiotic-exposed bacteria transiently refractory to killing and are recognized as a cause of antibiotic treatment failure. The putative de-N-acetylase DnpA increases persister levels in Pseudomonas aeruginosa upon exposure to fluoroquinolones in broth. In this study the wild-type PAO1 and its dnpA insertion mutant (dnpA::Tn) were used in parallel and compared for their capacity to generate persisters in broth (surviving fraction after exposure to high antibiotic concentrations) and their susceptibility to antibiotics in models of intracellular infection of THP-1 monocytes and of biofilms grown in microtiter plates. Multiplication in monocytes was evaluated by fluorescence dilution of GFP (expressed under the control of an inducible promoter) using flow cytometry. Gene expression was measured by quantitative RT-PCR. When exposed to fluoroquinolones (ciprofloxacin or levofloxacin) but not to meropenem or amikacin, the dnpA::Tn mutant showed a 3- to 10-fold lower persister fraction in broth. In infected monocytes, fluoroquinolones (but not the other antibiotics) were more effective (difference in Emax: 1.5 log cfu) against the dnpA::Tn mutant than against the wild-type PAO1. Dividing intracellular bacteria were more frequently seen (1.5 to 1.9-fold) with the fluoroquinolone-exposed dnpA::Tn mutant than with its parental strain. Fluoroquinolones (but not the other antibiotics) were also 3-fold more potent to prevent biofilm formation by the dnpA::Tn mutant than by PAO1 as well as to act upon biofilms (1–3 days of maturity) formed by the mutant than by the parental strain. Fluoroquinolones induced the expression of gyrA (4.5–7 fold) and mexX (3.6–5.4 fold) in the parental strain but to a lower extent (3–4-fold for gyrA and 1.8–2.8-fold for mexX, respectively) in the dnpA::Tn mutant. Thus, our data show that a dnpA insertion mutant of P. aeruginosa is more receptive to fluoroquinolone antibacterial effects than its parental strain in infected monocytes or in biofilms. The mechanism of this higher responsiveness could involve a reduced overexpression of the fluoroquinolone target.
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Affiliation(s)
- Shaunak Khandekar
- Pharmacologie Cellulaire et Moléculaire, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium
| | - Veerle Liebens
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Maarten Fauvart
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium.,Center for Microbiology, Vlaams Instituut voor Biotechnologie, Leuven, Belgium.,imec, Leuven, Belgium
| | - Paul M Tulkens
- Pharmacologie Cellulaire et Moléculaire, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium
| | - Jan Michiels
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium.,Center for Microbiology, Vlaams Instituut voor Biotechnologie, Leuven, Belgium
| | - Françoise Van Bambeke
- Pharmacologie Cellulaire et Moléculaire, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium
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72
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Goswami C, Fox S, Holden M, Connor M, Leanord A, Evans TJ. Genetic analysis of invasive Escherichia coli in Scotland reveals determinants of healthcare-associated versus community-acquired infections. Microb Genom 2018; 4. [PMID: 29932391 PMCID: PMC6096937 DOI: 10.1099/mgen.0.000190] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacteraemia caused by Escherichia coli is a growing problem with a significant mortality. The factors that influence the acquisition and outcome of these infections are not clear. Here, we have linked detailed genetic data from the whole-genome sequencing of 162 bacteraemic isolates collected in Scotland, UK, in 2013–2015, with clinical data in order to delineate bacterial and host factors that influence the acquisition in hospital or the community, outcome and antibiotic resistance. We identified four major sequence types (STs) in these isolates: ST131, ST69, ST73 and ST95. Nearly 50 % of the bacteraemic isolates had a urinary origin. ST69 was genetically distinct from the other STs, with significantly less sharing of accessory genes and with a distinct plasmid population. Virulence genes were widespread and diversely distributed between the dominant STs. ST131 was significantly associated with hospital-associated infections (HAIs), and ST69 with those from the community. However, there was no association of ST with outcome, although patients with HAI had a higher immediate mortality compared to those with community-associated infections (CAIs). Genome-wide association studies revealed genes involved in antibiotic persistence as significantly associated with HAIs and those encoding elements of a type VI secretion system with CAIs. Antibiotic resistance was common, and there were networks of correlated resistance genes and phenotypic antibiotic resistance. This study has revealed the complex interactions between the genotype of E. coli and its ability to cause bacteraemia, and some of the determinants influencing hospital or community acquisition. In part, these are shaped by antibiotic usage, but strain-specific factors are also important.
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Affiliation(s)
- Cosmika Goswami
- 1Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
| | - Stephen Fox
- 1Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
| | | | | | - Alistair Leanord
- 1Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
| | - Thomas J Evans
- 1Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
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73
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Antonova AV, Gryadunov DA, Zimenkov DV. Molecular Mechanisms of Drug Tolerance in Mycobacterium tuberculosis. Mol Biol 2018. [DOI: 10.1134/s0026893318030020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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74
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Reassessing the Role of Type II Toxin-Antitoxin Systems in Formation of Escherichia coli Type II Persister Cells. mBio 2018; 9:mBio.00640-18. [PMID: 29895634 PMCID: PMC6016239 DOI: 10.1128/mbio.00640-18] [Citation(s) in RCA: 120] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Persistence is a reversible and low-frequency phenomenon allowing a subpopulation of a clonal bacterial population to survive antibiotic treatments. Upon removal of the antibiotic, persister cells resume growth and give rise to viable progeny. Type II toxin-antitoxin (TA) systems were assumed to play a key role in the formation of persister cells in Escherichia coli based on the observation that successive deletions of TA systems decreased persistence frequency. In addition, the model proposed that stochastic fluctuations of (p)ppGpp levels are the basis for triggering activation of TA systems. Cells in which TA systems are activated are thought to enter a dormancy state and therefore survive the antibiotic treatment. Using independently constructed strains and newly designed fluorescent reporters, we reassessed the roles of TA modules in persistence both at the population and single-cell levels. Our data confirm that the deletion of 10 TA systems does not affect persistence to ofloxacin or ampicillin. Moreover, microfluidic experiments performed with a strain reporting the induction of the yefM-yoeB TA system allowed the observation of a small number of type II persister cells that resume growth after removal of ampicillin. However, we were unable to establish a correlation between high fluorescence and persistence, since the fluorescence of persister cells was comparable to that of the bulk of the population and none of the cells showing high fluorescence were able to resume growth upon removal of the antibiotic. Altogether, these data show that there is no direct link between induction of TA systems and persistence to antibiotics.IMPORTANCE Within a growing bacterial population, a small subpopulation of cells is able to survive antibiotic treatment by entering a transient state of dormancy referred to as persistence. Persistence is thought to be the cause of relapsing bacterial infections and is a major public health concern. Type II toxin-antitoxin systems are small modules composed of a toxic protein and an antitoxin protein counteracting the toxin activity. These systems were thought to be pivotal players in persistence until recent developments in the field. Our results demonstrate that previous influential reports had technical flaws and that there is no direct link between induction of TA systems and persistence to antibiotics.
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75
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Culviner PH, Laub MT. Global Analysis of the E. coli Toxin MazF Reveals Widespread Cleavage of mRNA and the Inhibition of rRNA Maturation and Ribosome Biogenesis. Mol Cell 2018; 70:868-880.e10. [PMID: 29861158 DOI: 10.1016/j.molcel.2018.04.026] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 04/03/2018] [Accepted: 04/27/2018] [Indexed: 10/14/2022]
Abstract
Toxin-antitoxin systems are widely distributed genetic modules that regulate growth and persistence in bacteria. Many systems, including E. coli MazEF, include toxins that are endoribonucleases, but the full set of targets for these toxins remains poorly defined. Previous studies on a limited set of transcripts suggested that MazF creates a pool of leaderless mRNAs that are preferentially translated by specialized ribosomes created through MazF cleavage of mature 16S rRNA. Here, using paired-end RNA sequencing (RNA-seq) and ribosome profiling, we provide a comprehensive, global analysis of MazF cleavage specificity and its targets. We find that MazF cleaves most transcripts at multiple sites within their coding regions, with very few full-length, leaderless mRNAs created. Additionally, our results demonstrate that MazF does not create a large pool of specialized ribosomes but instead rapidly disrupts ribosome biogenesis by targeting both ribosomal protein transcripts and rRNA precursors, helping to inhibit cell growth.
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Affiliation(s)
- Peter H Culviner
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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76
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Martins PMM, Merfa MV, Takita MA, De Souza AA. Persistence in Phytopathogenic Bacteria: Do We Know Enough? Front Microbiol 2018; 9:1099. [PMID: 29887856 PMCID: PMC5981161 DOI: 10.3389/fmicb.2018.01099] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 05/08/2018] [Indexed: 01/05/2023] Open
Abstract
Phytopathogenic bacteria affect a wide range of crops worldwide and have a negative impact in agriculture due to their associated economic losses and environmental impacts. Together with other biotic and abiotic stress factors, they pose a threat to global food production. Therefore, understanding bacterial survival strategies is an essential step toward the development of new strategies to control plant diseases. One mechanism used by bacteria to survive under stress conditions is the formation of persister cells. Persisters are a small fraction of phenotypic variants within an isogenic population that exhibits multidrug tolerance without undergoing genetic changes. They are dormant cells that survive treatment with antimicrobials by inactivating the metabolic functions that are disrupted by these compounds. They are thus responsible for the recalcitrance of many human diseases, and in the same way, they are thought to contribute to the survival of bacterial phytopathogens under a range of stresses they face in the environment. It is believed that persister cells of bacterial phytopathogens may lead to the reoccurrence of disease by recovering growth and recolonizing the host plant after the end of stress. However, compared to human pathogens, little is known about persister cells in phytopathogens, especially about their genetic regulation. In this review, we describe the overall knowledge on persister cells and their regulation in bacterial phytopathogens, focusing on their ability to survive stress conditions, to recover from dormancy and to maintain virulence.
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Affiliation(s)
- Paula M. M. Martins
- Laboratório de Biotecnologia, Centro de Citricultura, Instituto Agronômico de Campinas, Cordeiropolis, Brazil
| | - Marcus V. Merfa
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States
| | - Marco A. Takita
- Laboratório de Biotecnologia, Centro de Citricultura, Instituto Agronômico de Campinas, Cordeiropolis, Brazil
| | - Alessandra A. De Souza
- Laboratório de Biotecnologia, Centro de Citricultura, Instituto Agronômico de Campinas, Cordeiropolis, Brazil
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77
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Qian H, Yao Q, Tai C, Deng Z, Gan J, Ou HY. Identification and characterization of acetyltransferase-type toxin-antitoxin locus in Klebsiella pneumoniae. Mol Microbiol 2018; 108:336-349. [PMID: 29461656 DOI: 10.1111/mmi.13934] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/15/2018] [Indexed: 01/09/2023]
Abstract
A type II toxin-antitoxin (TA) system, in which the toxin contains a Gcn5-related N-acetyltransferase (GNAT) domain, has been characterized recently. GNAT toxin acetylates aminoacyl-tRNA and blocks protein translation. It is abolished by the cognate antitoxin that contains the ribbon-helix-helix (RHH) domain. Here, we present an experimental demonstration of the interaction of the GNAT-RHH complex with TA promoter DNA. First, the GNAT-RHH TA locus kacAT was found in Klebsiella pneumoniae HS11286, a strain resistant to multiple antibiotics. Overexpression of KacT halted cell growth and resulted in persister cell formation. The crystal structure also indicated that KacT is a typical acetyltransferase toxin. Co-expression of KacA neutralized KacT toxicity. Expression of the bicistronic kacAT locus was up-regulated during antibiotic stress. Finally, KacT and KacA formed a heterohexamer that interacted with promoter DNA, resulting in negative autoregulation of kacAT transcription. The N-terminus region of KacA accounted for specific binding to the palindromic sequence on the operator DNA, whereas its C-terminus region was essential for the inactivation of the GNAT toxin. These results provide an important insight into the regulation of the GNAT-RHH family TA system.
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Affiliation(s)
- Hongliang Qian
- State Key Laboratory of Microbial Metabolism, Joint International Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Qingqing Yao
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, China
| | - Cui Tai
- State Key Laboratory of Microbial Metabolism, Joint International Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Zixin Deng
- State Key Laboratory of Microbial Metabolism, Joint International Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Jianhua Gan
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, China
| | - Hong-Yu Ou
- State Key Laboratory of Microbial Metabolism, Joint International Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, China
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78
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Fighting bacterial persistence: Current and emerging anti-persister strategies and therapeutics. Drug Resist Updat 2018; 38:12-26. [DOI: 10.1016/j.drup.2018.03.002] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 03/07/2018] [Accepted: 03/25/2018] [Indexed: 01/13/2023]
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79
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Kawai Y, Matsumoto S, Ling Y, Okuda S, Tsuneda S. AldB controls persister formation in Escherichia coli depending on environmental stress. Microbiol Immunol 2018; 62:299-309. [PMID: 29577369 DOI: 10.1111/1348-0421.12587] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 03/06/2018] [Accepted: 03/15/2018] [Indexed: 12/14/2022]
Abstract
Persisters are multidrug-tolerant cells that are present within antibiotic-sensitive populations. Persister formation is not induced by genetic mutations, but rather by changes in the degree of expression of some genes. High redundancy has been observed among the pathways that have been hypothesized to respond to specific stresses. In this study, we conducted RNA sequencing of Escherichia coli persisters under various stress conditions to identify common mechanisms. We induced stresses such as glucose or amino acid exhaustion, acid stress and anaerobic conditions, all of which are encountered during bacterial pathogenesis. We found that most genes are differentially expressed depending on the specific stress condition; however, some genes were commonly expressed in persisters in most stress conditions. Commonly expressed genes are expected to be promising therapeutic targets for combating persistent infections. We found that knockdown of aldehyde dehydrogenase (aldB), which was expressed in every condition except for acid stress, decreased persisters in the non-stressed condition. However, the same strain unexpectedly showed an increased number of persisters in the amino acid-limited condition. Because the increase in persister number is glycolytic metabolite-dependent, metabolic flow may play a crucial role in aldB-mediated persister formation. These data suggest that environmental stresses alter persister mechanisms. Identification of environmental influences on persister formation during pathogenesis is therefore necessary to enabling persister eradication.
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Affiliation(s)
- Yuto Kawai
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Shinya Matsumoto
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yiwei Ling
- Graduate School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan
| | - Shujiro Okuda
- Graduate School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan
| | - Satoshi Tsuneda
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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80
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Nikolic N, Bergmiller T, Vandervelde A, Albanese TG, Gelens L, Moll I. Autoregulation of mazEF expression underlies growth heterogeneity in bacterial populations. Nucleic Acids Res 2018; 46:2918-2931. [PMID: 29432616 PMCID: PMC5888573 DOI: 10.1093/nar/gky079] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 12/30/2017] [Accepted: 01/27/2018] [Indexed: 01/24/2023] Open
Abstract
The MazF toxin sequence-specifically cleaves single-stranded RNA upon various stressful conditions, and it is activated as a part of the mazEF toxin-antitoxin module in Escherichia coli. Although autoregulation of mazEF expression through the MazE antitoxin-dependent transcriptional repression has been biochemically characterized, less is known about post-transcriptional autoregulation, as well as how both of these autoregulatory features affect growth of single cells during conditions that promote MazF production. Here, we demonstrate post-transcriptional autoregulation of mazF expression dynamics by MazF cleaving its own transcript. Single-cell analyses of bacterial populations during ectopic MazF production indicated that two-level autoregulation of mazEF expression influences cell-to-cell growth rate heterogeneity. The increase in growth rate heterogeneity is governed by the MazE antitoxin, and tuned by the MazF-dependent mazF mRNA cleavage. Also, both autoregulatory features grant rapid exit from the stress caused by mazF overexpression. Time-lapse microscopy revealed that MazF-mediated cleavage of mazF mRNA leads to increased temporal variability in length of individual cells during ectopic mazF overexpression, as explained by a stochastic model indicating that mazEF mRNA cleavage underlies temporal fluctuations in MazF levels during stress.
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Affiliation(s)
- Nela Nikolic
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Tobias Bergmiller
- Institute of Science and Technology Austria (IST Austria), 3400 Klosterneuburg, Austria
| | - Alexandra Vandervelde
- Laboratory of Dynamics in Biological Systems, Department of Cellular and Molecular Medicine, University of Leuven, 3000 Leuven, Belgium
| | - Tanino G Albanese
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Lendert Gelens
- Laboratory of Dynamics in Biological Systems, Department of Cellular and Molecular Medicine, University of Leuven, 3000 Leuven, Belgium
| | - Isabella Moll
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna BioCenter (VBC), 1030 Vienna, Austria
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81
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Ghosh A, Baltekin Ö, Wäneskog M, Elkhalifa D, Hammarlöf DL, Elf J, Koskiniemi S. Contact-dependent growth inhibition induces high levels of antibiotic-tolerant persister cells in clonal bacterial populations. EMBO J 2018; 37:embj.201798026. [PMID: 29572241 DOI: 10.15252/embj.201798026] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 02/08/2018] [Accepted: 02/21/2018] [Indexed: 12/31/2022] Open
Abstract
Bacterial populations can use bet-hedging strategies to cope with rapidly changing environments. One example is non-growing cells in clonal bacterial populations that are able to persist antibiotic treatment. Previous studies suggest that persisters arise in bacterial populations either stochastically through variation in levels of global signalling molecules between individual cells, or in response to various stresses. Here, we show that toxins used in contact-dependent growth inhibition (CDI) create persisters upon direct contact with cells lacking sufficient levels of CdiI immunity protein, which would otherwise bind to and neutralize toxin activity. CDI-mediated persisters form through a feedforward cycle where the toxic activity of the CdiA toxin increases cellular (p)ppGpp levels, which results in Lon-mediated degradation of the immunity protein and more free toxin. Thus, CDI systems mediate a population density-dependent bet-hedging strategy, where the fraction of non-growing cells is increased only when there are many cells of the same genotype. This may be one of the mechanisms of how CDI systems increase the fitness of their hosts.
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Affiliation(s)
- Anirban Ghosh
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Özden Baltekin
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Marcus Wäneskog
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Dina Elkhalifa
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Disa L Hammarlöf
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Johan Elf
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Sanna Koskiniemi
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
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82
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Tkachenko AG. Stress Responses of Bacterial Cells as Mechanism of Development of Antibiotic Tolerance (Review). APPL BIOCHEM MICRO+ 2018. [DOI: 10.1134/s0003683818020114] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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83
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van Geelen L, Meier D, Rehberg N, Kalscheuer R. (Some) current concepts in antibacterial drug discovery. Appl Microbiol Biotechnol 2018; 102:2949-2963. [PMID: 29455386 DOI: 10.1007/s00253-018-8843-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 02/05/2018] [Accepted: 02/06/2018] [Indexed: 12/30/2022]
Abstract
The rise of multidrug resistance in bacteria rendering pathogens unresponsive to many clinical drugs is widely acknowledged and considered a critical global healthcare issue. There is broad consensus that novel antibacterial chemotherapeutic options are extremely urgently needed. However, the development pipeline of new antibacterial drug lead structures is poorly filled and not commensurate with the scale of the problem since the pharmaceutical industry has shown reduced interest in antibiotic development in the past decades due to high economic risks and low profit expectations. Therefore, academic research institutions have a special responsibility in finding novel treatment options for the future. In this mini review, we want to provide a broad overview of the different approaches and concepts that are currently pursued in this research field.
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Affiliation(s)
- Lasse van Geelen
- Institute of Pharmaceutical Biology and Biotechnology, Heinrich Heine University Düsseldorf, 40225, Dusseldorf, Germany
| | - Dieter Meier
- Institute of Pharmaceutical Biology and Biotechnology, Heinrich Heine University Düsseldorf, 40225, Dusseldorf, Germany
| | - Nidja Rehberg
- Institute of Pharmaceutical Biology and Biotechnology, Heinrich Heine University Düsseldorf, 40225, Dusseldorf, Germany
| | - Rainer Kalscheuer
- Institute of Pharmaceutical Biology and Biotechnology, Heinrich Heine University Düsseldorf, 40225, Dusseldorf, Germany.
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84
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Yamamoto N, Isshiki R, Kawai Y, Tanaka D, Sekiguchi T, Matsumoto S, Tsuneda S. Stochastic expression of lactate dehydrogenase A induces Escherichia coli persister formation. J Biosci Bioeng 2018; 126:30-37. [PMID: 29449156 DOI: 10.1016/j.jbiosc.2018.01.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 01/22/2018] [Accepted: 01/22/2018] [Indexed: 01/06/2023]
Abstract
Bacterial persisters are phenotypic variants that survive the treatment of lethal doses of growth-targeting antibiotics without mutations. Although the mechanism underlying persister formation has been studied for decades, how the persister phenotype is switched on and protects itself from antibiotics has been elusive. In this study, we focused on the lactate dehydrogenase gene (ldhA) that was upregulated in an Escherichia coli persister-enriched population. A survival rate assay using an ldhA-overexpressing strain showed that ldhA expression induced persister formation. To identify ldhA-mediated persister formation at the single-cell level, time-lapse microscopy with a microfluidic device was used. Stochastic ldhA expression was found to induce dormancy and tolerance against high-dose ampicillin treatment (500 μg/ml). To better understand the underlying mechanism, we investigated the relationship between ldhA-mediated persister formation and previously reported persister formation through aerobic metabolism repression. As a result, ldhA expression enhanced the proton motive force (PMF) and ATP synthesis. These findings suggest that ldhA-mediated persister formation pathway is different from previously reported persister formation via repression of aerobic metabolism.
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Affiliation(s)
- Naoki Yamamoto
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Rino Isshiki
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yuto Kawai
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Daiki Tanaka
- Research Organization for Nano and Life Innovation, Waseda University, 513 Waseda-tsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, Japan
| | - Tetsushi Sekiguchi
- Research Organization for Nano and Life Innovation, Waseda University, 513 Waseda-tsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, Japan
| | - Shinya Matsumoto
- Graduate School of Medicine, Nagoya University, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan
| | - Satoshi Tsuneda
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan; Research Organization for Nano and Life Innovation, Waseda University, 513 Waseda-tsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, Japan.
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85
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Harms A, Brodersen DE, Mitarai N, Gerdes K. Toxins, Targets, and Triggers: An Overview of Toxin-Antitoxin Biology. Mol Cell 2018; 70:768-784. [PMID: 29398446 DOI: 10.1016/j.molcel.2018.01.003] [Citation(s) in RCA: 398] [Impact Index Per Article: 66.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 11/06/2017] [Accepted: 01/02/2018] [Indexed: 12/01/2022]
Abstract
Bacterial toxin-antitoxin (TA) modules are abundant genetic elements that encode a toxin protein capable of inhibiting cell growth and an antitoxin that counteracts the toxin. The majority of toxins are enzymes that interfere with translation or DNA replication, but a wide variety of molecular activities and cellular targets have been described. Antitoxins are proteins or RNAs that often control their cognate toxins through direct interactions and, in conjunction with other signaling elements, through transcriptional and translational regulation of TA module expression. Three major biological functions of TA modules have been discovered, post-segregational killing ("plasmid addiction"), abortive infection (bacteriophage immunity through altruistic suicide), and persister formation (antibiotic tolerance through dormancy). In this review, we summarize the current state of the field and highlight how multiple levels of regulation shape the conditions of toxin activation to achieve the different biological functions of TA modules.
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Affiliation(s)
- Alexander Harms
- Centre for Bacterial Stress Response and Persistence, Department of Biology, University of Copenhagen, 2200 Copenhagen, Denmark.
| | - Ditlev Egeskov Brodersen
- Centre for Bacterial Stress Response and Persistence, Department of Biology, University of Copenhagen, 2200 Copenhagen, Denmark; Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
| | - Namiko Mitarai
- Centre for Bacterial Stress Response and Persistence, Department of Biology, University of Copenhagen, 2200 Copenhagen, Denmark; Niels Bohr Institute, Department of Physics, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Kenn Gerdes
- Centre for Bacterial Stress Response and Persistence, Department of Biology, University of Copenhagen, 2200 Copenhagen, Denmark.
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86
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Homologous VapC Toxins Inhibit Translation and Cell Growth by Sequence-Specific Cleavage of tRNA fMet. J Bacteriol 2018; 200:JB.00582-17. [PMID: 29109187 DOI: 10.1128/jb.00582-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 10/30/2017] [Indexed: 01/19/2023] Open
Abstract
Type II toxin-antitoxin (TA) systems play a critical role in the establishment and maintenance of bacterial dormancy. They are composed of a protein toxin and its cognate protein antitoxin. They function to regulate growth under conditions of stress, such as starvation or antibiotic treatment. As cellular proteases degrade the antitoxin, which normally binds and neutralizes the toxin, this frees the toxin to act on its cellular targets and arrest bacterial growth. TA systems are of particular concern in regard to pathogenic organisms, such as nontypeable Haemophilus influenzae (NTHi), as dormancy may lead to chronic infections and failure of antibiotic treatment. Many targets of VapC toxins have not been identified, to date, and this knowledge is crucial to understanding how toxins control the establishment and maintenance of bacterial dormancy. Accordingly, we characterized the target specificity of the VapC toxins from the two paralogous NTHi vapBC TA systems. RNA sequencing and Northern blot analysis revealed that VapC1 and VapC2 cleave tRNAfMet in the anticodon loop. Overexpression of tRNAfMet suppresses VapC toxicity, suggesting that translation inhibition results from the depletion of tRNAfMet These experiments also identified base pairs in the tRNAfMet anticodon stem that play a key role in VapC-specific cleavage of the tRNA. Together these findings suggest the potential for NTHi VapC1 and VapC2 to induce dormancy by sequence-specific cleavage of tRNAfMetIMPORTANCE Bacterial persistence is a significant concern in regard to pathogenic organisms, such as nontypeable Haemophilus influenzae, as it can result in recurrent and chronic infections. Toxin-antitoxin systems can lead to persistence by causing bacteria to enter a slow-growing state that renders them antibiotic tolerant. Type II toxin components affect a wide variety of bacterial targets in order to elicit dormancy, and for many toxin-antitoxin systems, these mechanisms are not well understood. Thus, in order to understand how vapBC toxin-antitoxin systems cause dormancy, it is crucial to investigate the substrate specificity of VapC toxins. This study identifies the target of the VapC1 and VapC2 toxins from NTHi and takes important steps toward understanding the specificity of these toxins for their tRNA target.
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87
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Duprilot M, Decre D, Genel N, Drieux L, Sougakoff W, Arlet G. Diversity and functionality of plasmid-borne VagCD toxin-antitoxin systems of Klebsiella pneumoniae. J Antimicrob Chemother 2018; 72:1320-1326. [PMID: 28119479 DOI: 10.1093/jac/dkw569] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 12/12/2016] [Indexed: 11/14/2022] Open
Abstract
Objectives To explore the VagCD toxin-antitoxin (TA) systems encoded on plasmids in multiresistant Klebsiella pneumoniae strains. Methods Previously sequenced K. pneumoniae plasmids were used for in silico analysis and a collection of 63 resistant K. pneumoniae strains was used for epidemiological study. Functional analysis was done after separate cloning of the toxin gene under the control of the arabinose-inducible promoter of pBAD43 and of the antitoxin gene under the control of the constitutive promoter of pUC19. Results In silico , two types of VagCD systems, VagCD1 and VagCD2, encoded on K. pneumoniae plasmids could be distinguished, 15% carrying one of these TA systems. Moreover, in a collection of antibiotic-resistant K. pneumoniae strains including ESBL or carbapenemase producers, 17.5% of isolates were found to harbour a VagCD TA system. VagCD1 and VagCD2 were proved functional TA systems, with VagD the toxin and VagC its antitoxin, not only in K. pneumoniae but also in Escherichia coli and other Enterobacteriaceae. Toxin expression was found to induce a significant decrease in a bacterial population resulting from both bactericidal and bacteriostatic effects. Conclusions The vagCD genes of K. pneumoniae encode a functional broad-spectrum TA system and are conserved on the large multiple antibiotic resistance-conferring plasmids in this species.
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Affiliation(s)
- Marion Duprilot
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, U1135, Centre d'Immunologie et des Maladies Infectieuses (CIMI-Paris), Paris, France
| | - Dominique Decre
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, U1135, Centre d'Immunologie et des Maladies Infectieuses (CIMI-Paris), Paris, France.,Laboratoire de Bactériologie, AP-HP, Groupe Hospitalier des Hôpitaux Universitaires de l'Est Parisien, AP-HP, Paris, France
| | - Nathalie Genel
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, U1135, Centre d'Immunologie et des Maladies Infectieuses (CIMI-Paris), Paris, France
| | - Laurence Drieux
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, U1135, Centre d'Immunologie et des Maladies Infectieuses (CIMI-Paris), Paris, France.,Laboratoire de Bactériologie, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, AP-HP, Paris, France
| | - Wladimir Sougakoff
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, U1135, Centre d'Immunologie et des Maladies Infectieuses (CIMI-Paris), Paris, France.,Laboratoire de Bactériologie, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, AP-HP, Paris, France
| | - Guillaume Arlet
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, U1135, Centre d'Immunologie et des Maladies Infectieuses (CIMI-Paris), Paris, France.,Laboratoire de Bactériologie, AP-HP, Groupe Hospitalier des Hôpitaux Universitaires de l'Est Parisien, AP-HP, Paris, France
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88
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Multifaceted remodeling by vitamin C boosts sensitivity of Mycobacterium tuberculosis subpopulations to combination treatment by anti-tubercular drugs. Redox Biol 2018; 15:452-466. [PMID: 29413958 PMCID: PMC5975079 DOI: 10.1016/j.redox.2017.12.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 12/28/2017] [Accepted: 12/30/2017] [Indexed: 12/03/2022] Open
Abstract
Bacterial dormancy is a major impediment to the eradication of tuberculosis (TB), because currently used drugs primarily target actively replicating bacteria. Therefore, decoding of the critical survival pathways in dormant tubercle bacilli is a research priority to formulate new approaches for killing these bacteria. Employing a network-based gene expression analysis approach, we demonstrate that redox active vitamin C (vit C) triggers a multifaceted and robust adaptation response in Mycobacterium tuberculosis (Mtb) involving ~ 67% of the genome. Vit C-adapted bacteria display well-described features of dormancy, including growth stasis and progression to a viable but non-culturable (VBNC) state, loss of acid-fastness and reduction in length, dissipation of reductive stress through triglyceride (TAG) accumulation, protective response to oxidative stress, and tolerance to first line TB drugs. VBNC bacteria are reactivatable upon removal of vit C and they recover drug susceptibility properties. Vit C synergizes with pyrazinamide, a unique TB drug with sterilizing activity, to kill dormant and replicating bacteria, negating any tolerance to rifampicin and isoniazid in combination treatment in both in-vitro and intracellular infection models. Finally, the vit C multi-stress redox models described here also offer a unique opportunity for concurrent screening of compounds/combinations active against heterogeneous subpopulations of Mtb. These findings suggest a novel strategy of vit C adjunctive therapy by modulating bacterial physiology for enhanced efficacy of combination chemotherapy with existing drugs, and also possible synergies to guide new therapeutic combinations towards accelerating TB treatment. Vitamin C induces dormancy and reversible VBNC state in M. tuberculosis. Dormancy is achieved through a well-coordinated multifaceted bacterial response. Vitamin C synergy with pyrazinamide negates bacterial tolerance to other TB drugs. Vitamin C adjunctive therapy is a potential strategy for shortening chemotherapy. Vitamin C-based models are novel screening platforms for new compounds/combinations.
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89
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Cole BK, Scott E, Ilikj M, Bard D, Akins DR, Dyer DW, Chavez-Bueno S. Route of infection alters virulence of neonatal septicemia Escherichia coli clinical isolates. PLoS One 2017; 12:e0189032. [PMID: 29236742 PMCID: PMC5728477 DOI: 10.1371/journal.pone.0189032] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 09/05/2017] [Indexed: 12/03/2022] Open
Abstract
Escherichia coli is the leading cause of Gram-negative neonatal septicemia in the United States. Invasion and passage across the neonatal gut after ingestion of maternal E. coli strains produce bacteremia. In this study, we compared the virulence properties of the neonatal E. coli bacteremia clinical isolate SCB34 with the archetypal neonatal E. coli meningitis strain RS218. Whole-genome sequencing data was used to compare the protein coding sequences among these clinical isolates and 33 other representative E. coli strains. Oral inoculation of newborn animals with either strain produced septicemia, whereas intraperitoneal injection caused septicemia only in pups infected with RS218 but not in those injected with SCB34. In addition to being virulent only through the oral route, SCB34 demonstrated significantly greater invasion and transcytosis of polarized intestinal epithelial cells in vitro as compared to RS218. Protein coding sequences comparisons highlighted the presence of known virulence factors that are shared among several of these isolates, and revealed the existence of proteins exclusively encoded in SCB34, many of which remain uncharacterized. Our study demonstrates that oral acquisition is crucial for the virulence properties of the neonatal bacteremia clinical isolate SCB34. This characteristic, along with its enhanced ability to invade and transcytose intestinal epithelium are likely determined by the specific virulence factors that predominate in this strain.
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Affiliation(s)
- Bryan K. Cole
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Edgar Scott
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Marko Ilikj
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - David Bard
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Darrin R. Akins
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - David W. Dyer
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Susana Chavez-Bueno
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- * E-mail:
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90
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Abstract
Bacterial persisters are phenotypic variants that survive antibiotic treatment in a dormant state and can be formed by multiple pathways. We recently proposed that the second messenger (p)ppGpp drives Escherichia coli persister formation through protease Lon and activation of toxin-antitoxin (TA) modules. This model found considerable support among researchers studying persisters but also generated controversy as part of recent debates in the field. In this study, we therefore used our previous work as a model to critically examine common experimental procedures to understand and overcome the inconsistencies often observed between results of different laboratories. Our results show that seemingly simple antibiotic killing assays are very sensitive to variations in culture conditions and bacterial growth phase. Additionally, we found that some assay conditions cause the killing of antibiotic-tolerant persisters via induction of cryptic prophages. Similarly, the inadvertent infection of mutant strains with bacteriophage ϕ80, a notorious laboratory contaminant, apparently caused several of the phenotypes that we reported in our previous studies. We therefore reconstructed all infected mutants and probed the validity of our model of persister formation in a refined assay setup that uses robust culture conditions and unravels the dynamics of persister cells through all bacterial growth stages. Our results confirm the importance of (p)ppGpp and Lon but no longer support a role of TA modules in E. coli persister formation under unstressed conditions. We anticipate that the results and approaches reported in our study will lay the ground for future work in the field.IMPORTANCE The recalcitrance of antibiotic-tolerant persister cells is thought to cause relapsing infections and antibiotic treatment failure in various clinical setups. Previous studies identified multiple genetic pathways involved in persister formation but also revealed reproducibility problems that sparked controversies about adequate tools to study persister cells. In this study, we unraveled how typical antibiotic killing assays often fail to capture the biology of persisters and instead give widely differing results based on poorly controlled experimental parameters and artifacts caused by cryptic as well as contaminant prophages. We therefore established a new, robust assay that enabled us to follow the dynamics of persister cells through all growth stages of bacterial cultures without distortions by bacteriophages. This system also favored adequate comparisons of mutant strains with aberrant growth phenotypes. We anticipate that our results will contribute to a robust, common basis for future studies on the formation and eradication of antibiotic-tolerant persisters.
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91
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Bleuven C, Landry CR. Molecular and cellular bases of adaptation to a changing environment in microorganisms. Proc Biol Sci 2017; 283:rspb.2016.1458. [PMID: 27798299 DOI: 10.1098/rspb.2016.1458] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 10/04/2016] [Indexed: 12/27/2022] Open
Abstract
Environmental heterogeneity constitutes an evolutionary challenge for organisms. While evolutionary dynamics under variable conditions has been explored for decades, we still know relatively little about the cellular and molecular mechanisms involved. It is of paramount importance to examine these molecular bases because they may play an important role in shaping the course of evolution. In this review, we examine the diversity of adaptive mechanisms in the face of environmental changes. We exploit the recent literature on microbial systems because those have benefited the most from the recent emergence of genetic engineering and experimental evolution followed by genome sequencing. We identify four emerging trends: (i) an adaptive molecular change in a pathway often results in fitness trade-off in alternative environments but the effects are dependent on a mutation's genetic background; (ii) adaptive changes often modify transcriptional and signalling pathways; (iii) several adaptive changes may occur within the same molecular pathway but be associated with pleiotropy of different signs across environments; (iv) because of their large associated costs, macromolecular changes such as gene amplification and aneuploidy may be a rapid mechanism of adaptation in the short-term only. The course of adaptation in a variable environment, therefore, depends on the complexity of the environment but also on the molecular relationships among the genes involved and between the genes and the phenotypes under selection.
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Affiliation(s)
- Clara Bleuven
- Département de Biologie, Université Laval, Québec, Québec, Canada .,Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Québec, Canada.,PROTEO, The Quebec Network for Research on Protein Function, Engineering, and Applications, Québec, Québec, Canada
| | - Christian R Landry
- Département de Biologie, Université Laval, Québec, Québec, Canada.,Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Québec, Canada.,Big Data Research Center, Université Laval, Québec, Québec, Canada.,PROTEO, The Quebec Network for Research on Protein Function, Engineering, and Applications, Québec, Québec, Canada
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92
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Gerdes K. Hypothesis: type I toxin-antitoxin genes enter the persistence field-a feedback mechanism explaining membrane homoeostasis. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2016.0189. [PMID: 27672159 DOI: 10.1098/rstb.2016.0189] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/19/2016] [Indexed: 11/12/2022] Open
Abstract
Bacteria form persisters, cells that are tolerant to multiple antibiotics and other types of environmental stress. Persister formation can be induced either stochastically in single cells of a growing bacterial ensemble, or by environmental stresses, such as nutrient starvation, in a subpopulation of cells. In many cases, the molecular mechanisms underlying persistence are still unknown. However, there is growing evidence that, in enterobacteria, both stochastically and environmentally induced persistence are controlled by the second messenger (p)ppGpp. For example, the 'alarmone' (p)ppGpp activates Lon, which, in turn, activates type II toxin-antitoxin (TA) modules to thereby induce persistence. Recently, it has been shown that a type I TA module, hokB/sokB, also can induce persistence. In this case, the underlying mechanism depends on the universally conserved GTPase Obg and, surprisingly, also (p)ppGpp. In the presence of (p)ppGpp, Obg stimulates hokB transcription and induces persistence. HokB toxin expression is under both negative and positive control: SokB antisense RNA inhibits hokB mRNA translation, while (p)ppGpp and Obg together stimulate hokB transcription. HokB is a small toxic membrane protein that, when produced in modest amounts, leads to membrane depolarization, cell stasis and persistence. By contrast, overexpression of HokB disrupts the membrane potential and kills the cell. These observations raise the question of how expression of HokB is regulated. Here, I propose a homoeostatic control mechanism that couples HokB expression to the membrane-bound RNase E that degrades and inactivates SokB antisense RNA.This article is part of the themed issue 'The new bacteriology'.
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Affiliation(s)
- Kenn Gerdes
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen N, Denmark
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93
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Impact of bacterial sRNAs in stress responses. Biochem Soc Trans 2017; 45:1203-1212. [PMID: 29101308 PMCID: PMC5730939 DOI: 10.1042/bst20160363] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 10/02/2017] [Accepted: 10/04/2017] [Indexed: 12/11/2022]
Abstract
Bacterial life is harsh and involves numerous environmental and internal challenges that are perceived as stresses. Consequently, adequate responses to survive, cope with, and counteract stress conditions have evolved. In the last few decades, a class of small, non-coding RNAs (sRNAs) has been shown to be involved as key players in stress responses. This review will discuss — primarily from an enterobacterial perspective — selected stress response pathways that involve antisense-type sRNAs. These include themes of how bacteria deal with severe envelope stress, threats of DNA damage, problems with poisoning due to toxic sugar intermediates, issues of iron homeostasis, and nutrient limitation/starvation. The examples discussed highlight how stress relief can be achieved, and how sRNAs act mechanistically in regulatory circuits. For some cases, we will propose scenarios that may suggest why contributions from post-transcriptional control by sRNAs, rather than transcriptional control alone, appear to be a beneficial and universally selected feature.
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94
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Lin H, Ye C, Chen S, Zhang S, Yu X. Viable but non-culturable E. coli induced by low level chlorination have higher persistence to antibiotics than their culturable counterparts. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 230:242-249. [PMID: 28662489 DOI: 10.1016/j.envpol.2017.06.047] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 06/09/2017] [Accepted: 06/13/2017] [Indexed: 05/22/2023]
Abstract
Disinfectant used in drinking water treatment and distribution system can induce culturable bacteria, including various kinds of pathogenic bacteria, into viable but non-culturable (VBNC) state. The loss of cultural state, resuscitation and environmental persistence of VBNC bacteria will severely damage drinking water microbiological safety and thus pose a risk to public health. The manner in which chlorination treatment induced a VBNC state in Escherichia coli and the antibiotic persistence of VBNC bacteria was investigated. It was found that low dosage of chlorine (0.5 mg L-1) disinfection effectively reduced the culturability of E. coli and induced a VBNC state, after which metabolic activity was reduced and persistence to 9 typical antibiotics was enhanced. Furthermore, RT-qPCR results showed that stress resistance genes (rpoS, marA, ygfA, relE) and ARGs, especially efflux genes were up-regulated compared with culturable cells. The intracellular concentration was tested and found to be lower in VBNC cells than in actively growing E. coli, which suggested a higher efflux rate. The data presented indicate that VBNC E. coli are more persistent than culturable counterparts to a wide variety of antibiotics. VBNC E. coli constitute a potential source of contamination and should be considered during monitoring of drinking water networks.
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Affiliation(s)
- Huirong Lin
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, People's Republic of China
| | - Chengsong Ye
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, People's Republic of China
| | - Sheng Chen
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, People's Republic of China
| | - Shenghua Zhang
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, People's Republic of China
| | - Xin Yu
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, People's Republic of China.
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95
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Deep A, Kaundal S, Agarwal S, Singh R, Thakur KG. Crystal structure of Mycobacterium tuberculosis
VapC20 toxin and its interactions with cognate antitoxin, VapB20, suggest a model for toxin-antitoxin assembly. FEBS J 2017; 284:4066-4082. [DOI: 10.1111/febs.14289] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Revised: 09/19/2017] [Accepted: 10/03/2017] [Indexed: 11/27/2022]
Affiliation(s)
- Amar Deep
- Structural Biology Laboratory; G. N. Ramachandran Protein Centre; Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH); Chandigarh India
| | - Soni Kaundal
- Structural Biology Laboratory; G. N. Ramachandran Protein Centre; Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH); Chandigarh India
| | - Sakshi Agarwal
- Vaccine and Infectious Disease Research Centre; Translational Health Science and Technology Institute; NCR-Biotech Science Cluster; Faridabad India
| | - Ramandeep Singh
- Vaccine and Infectious Disease Research Centre; Translational Health Science and Technology Institute; NCR-Biotech Science Cluster; Faridabad India
| | - Krishan Gopal Thakur
- Structural Biology Laboratory; G. N. Ramachandran Protein Centre; Council of Scientific and Industrial Research-Institute of Microbial Technology (CSIR-IMTECH); Chandigarh India
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Affiliation(s)
- Kim Lewis
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA 02115, USA.
| | - Yue Shan
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA 02115, USA
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97
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Nikolic N, Didara Z, Moll I. MazF activation promotes translational heterogeneity of the grcA mRNA in Escherichia coli populations. PeerJ 2017; 5:e3830. [PMID: 28948108 PMCID: PMC5610899 DOI: 10.7717/peerj.3830] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 08/29/2017] [Indexed: 12/04/2022] Open
Abstract
Bacteria adapt to adverse environmental conditions by altering gene expression patterns. Recently, a novel stress adaptation mechanism has been described that allows Escherichia coli to alter gene expression at the post-transcriptional level. The key player in this regulatory pathway is the endoribonuclease MazF, the toxin component of the toxin-antitoxin module mazEF that is triggered by various stressful conditions. In general, MazF degrades the majority of transcripts by cleaving at ACA sites, which results in the retardation of bacterial growth. Furthermore, MazF can process a small subset of mRNAs and render them leaderless by removing their ribosome binding site. MazF concomitantly modifies ribosomes, making them selective for the translation of leaderless mRNAs. In this study, we employed fluorescent reporter-systems to investigate mazEF expression during stressful conditions, and to infer consequences of the mRNA processing mediated by MazF on gene expression at the single-cell level. Our results suggest that mazEF transcription is maintained at low levels in single cells encountering adverse conditions, such as antibiotic stress or amino acid starvation. Moreover, using the grcA mRNA as a model for MazF-mediated mRNA processing, we found that MazF activation promotes heterogeneity in the grcA reporter expression, resulting in a subpopulation of cells with increased levels of GrcA reporter protein.
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Affiliation(s)
- Nela Nikolic
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Vienna Biocenter (VBC), University of Vienna, Vienna, Austria
- Current affiliation: Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | - Zrinka Didara
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Vienna Biocenter (VBC), University of Vienna, Vienna, Austria
- Current affiliation: Department of Life Sciences, IMC University of Applied Sciences Krems, Krems an der Donau, Austria
| | - Isabella Moll
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Vienna Biocenter (VBC), University of Vienna, Vienna, Austria
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98
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Jurėnas D, Garcia-Pino A, Van Melderen L. Novel toxins from type II toxin-antitoxin systems with acetyltransferase activity. Plasmid 2017; 93:30-35. [PMID: 28941941 DOI: 10.1016/j.plasmid.2017.08.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 08/24/2017] [Accepted: 08/28/2017] [Indexed: 12/21/2022]
Abstract
Type II toxin-antitoxin (TA) systems are widespread in bacterial and archeal genomes. These modules are very dynamic and participate in bacterial genome evolution through horizontal gene transfer. TA systems are commonly composed of a labile antitoxin and a stable toxin. Toxins appear to preferentially inhibit the protein synthesis process. Toxins use a variety of molecular mechanisms and target nearly every step of translation to achieve their inhibitory function. This review focuses on a recently identified TA family that includes acetyltransferase toxins. The AtaT and TacT toxins are the best-characterized to date in this family. AtaT and TacT both inhibit translation by acetylating the amino acid charged on tRNAs. However, the specificities of these 2 toxins are different as AtaT inhibits translation initiation by acetylation of the initiator tRNA whereas TacT acetylates elongator tRNAs. The molecular mechanisms of these toxins are discussed, as well as the functions and possible evolutionary origins of this diverse toxin family.
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Affiliation(s)
- Dukas Jurėnas
- Department of Biochemistry and Molecular Biology, Vilnius University Joint Life Sciences Center, Vilnius, Lithuania; Cellular and Molecular Microbiology (CM2), Faculté des Sciences, Université Libre de Bruxelles (ULB), Belgium
| | - Abel Garcia-Pino
- Cellular and Molecular Microbiology (CM2), Faculté des Sciences, Université Libre de Bruxelles (ULB), Belgium
| | - Laurence Van Melderen
- Cellular and Molecular Microbiology (CM2), Faculté des Sciences, Université Libre de Bruxelles (ULB), Belgium.
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99
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Enabling stop codon read-through translation in bacteria as a probe for amyloid aggregation. Sci Rep 2017; 7:11908. [PMID: 28928456 PMCID: PMC5605706 DOI: 10.1038/s41598-017-12174-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 09/05/2017] [Indexed: 11/23/2022] Open
Abstract
Amyloid aggregation of the eukaryotic translation terminator eRF3/Sup35p, the [PSI+] prion, empowers yeast ribosomes to read-through UGA stop codons. No similar functional prion, skipping a stop codon, has been found in Escherichia coli, a fact possibly due to the efficient back-up systems found in bacteria to rescue non-stop complexes. Here we report that engineering hydrophobic amyloidogenic repeats from a synthetic bacterial prion-like protein (RepA-WH1) into the E. coli releasing factor RF1 promotes its aggregation and enables ribosomes to continue with translation through a premature UAG stop codon located in a β-galactosidase reporter. To our knowledge, intended aggregation of a termination factor is a way to overcome the bacterial translation quality checkpoint that had not been reported so far. We also show the feasibility of using the amyloidogenic RF1 chimeras as a reliable, rapid and cost-effective system to screen for molecules inhibiting intracellular protein amyloidogenesis in vivo, by testing the effect on the chimeras of natural polyphenols with known anti-amyloidogenic properties. Resveratrol exhibits a clear amyloid-solubilizing effect in this assay, showing no toxicity to bacteria or interference with the enzymatic activity of β-galactosidase.
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100
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Klimina KM, Poluektova EU, Danilenko VN. Bacterial toxin–antitoxin systems: Properties, functional significance, and possibility of use (Review). APPL BIOCHEM MICRO+ 2017. [DOI: 10.1134/s0003683817050076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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