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Drlica K, Zhao X. Bacterial death from treatment with fluoroquinolones and other lethal stressors. Expert Rev Anti Infect Ther 2020; 19:601-618. [PMID: 33081547 DOI: 10.1080/14787210.2021.1840353] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Lethal stressors, including antimicrobials, kill bacteria in part through a metabolic response proposed to involve reactive oxygen species (ROS). The quinolone anti-bacterials have served as key experimental tools in developing this idea. AREAS COVERED Bacteriostatic and bactericidal action of quinolones are distinguished, with emphasis on the contribution of chromosome fragmentation and ROS accumulation to bacterial death. Action of non-quinolone antibacterials and non-antimicrobial stressors is described to provide a general framework for understanding stress-mediated, bacterial death. EXPERT OPINION Quinolones trap topoisomerases on DNA in reversible complexes that block DNA replication and bacterial growth. At elevated drug concentrations, DNA ends are released from topoisomerase-mediated constraint, leading to the idea that death arises from chromosome fragmentation. However, DNA ends also stimulate repair, which is energetically expensive. An incompletely understood metabolic shift occurs, and ROS accumulate. Even after quinolone removal, ROS continue to amplify, generating secondary and tertiary damage that overwhelms repair and causes death. Repair may also contribute to death directly via DNA breaks arising from incomplete base-excision repair of ROS-oxidized nucleotides. Remarkably, perturbations that interfere with ROS accumulation confer tolerance to many diverse lethal agents.
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Affiliation(s)
| | - Xilin Zhao
- Rutgers University, Newark, NJ, USA.,State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, South Xiang-An Road, Xiang-An District, Xiamen, Fujian Province, China
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Global mistranslation increases cell survival under stress in Escherichia coli. PLoS Genet 2020; 16:e1008654. [PMID: 32150542 PMCID: PMC7082066 DOI: 10.1371/journal.pgen.1008654] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 03/19/2020] [Accepted: 02/05/2020] [Indexed: 12/23/2022] Open
Abstract
Mistranslation is typically deleterious for cells, although specific mistranslated proteins can confer a short-term benefit in a particular environment. However, given its large overall cost, the prevalence of high global mistranslation rates remains puzzling. Altering basal mistranslation levels of Escherichia coli in several ways, we show that generalized mistranslation enhances early survival under DNA damage, by rapidly activating the SOS response. Mistranslating cells maintain larger populations after exposure to DNA damage, and thus have a higher probability of sampling critical beneficial mutations. Both basal and artificially increased mistranslation increase the number of cells that are phenotypically tolerant and genetically resistant under DNA damage; they also enhance survival at high temperature. In contrast, decreasing the normal basal mistranslation rate reduces cell survival. This wide-ranging stress resistance relies on Lon protease, which is revealed as a key effector that induces the SOS response in addition to alleviating proteotoxic stress. The new links between error-prone protein synthesis, DNA damage, and generalised stress resistance indicate surprising coordination between intracellular stress responses and suggest a novel hypothesis to explain high global mistranslation rates.
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Smirnova GV, Oktyabrsky ON. Relationship between Escherichia coli growth rate and bacterial susceptibility to ciprofloxacin. FEMS Microbiol Lett 2019; 365:4705891. [PMID: 29228224 DOI: 10.1093/femsle/fnx254] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 11/30/2017] [Indexed: 01/07/2023] Open
Abstract
The effect of Escherichia coli growth rate on its susceptibility to ciprofloxacin was investigated using bacteria grown on different carbon sources and harboring mutations in genes encoding tricarboxylic acid cycle enzymes. A 1-h treatment of the wild type (wt) grown on glucose, succinate, malate, α-ketoglutarate or acetate with 0.3 μg ml-1 ciprofloxacin decreased the number of surviving cells (CFU ml-1), 560, 110, 74, 62 and 5 times, respectively. Among the mutants tested, sucB strain, which grew 1.75 times slower than wt, was 7.4-fold more tolerant to 0.3 μg ml-1 of ciprofloxacin than wt. Strong inverse correlations between log(CFU ml-1) after 1-h exposure to 0.3 and 3.0 μg ml-1 ciprofloxacin and the specific growth rate prior to antibiotic treatment (r = - 0.93 and -0.96, respectively) were observed. Data from the current and previous studies on the inhibitory effect of ciprofloxacin on cultures exhibiting a wide range of growth rates (0.01-1.3 h-1) were collated. Statistical analysis revealed a significant inverse correlation between log(CFU ml-1) after exposure to 3.0 μg ml-1 of ciprofloxacin and the specific bacterial growth rate prior to antibiotic exposure (r = -0.92). These data may be used in a design of antibiotic treatment protocols.
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Affiliation(s)
- Galina V Smirnova
- Laboratory of Physiology and Genetics of Microorganisms, Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Perm 614081, Russia
| | - Oleg N Oktyabrsky
- Laboratory of Physiology and Genetics of Microorganisms, Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Perm 614081, Russia.,Department of Chemistry and Biotechnology, Perm National Research Polytechnic University, Perm 614990, Russia
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Prasetyoputri A, Jarrad AM, Cooper MA, Blaskovich MA. The Eagle Effect and Antibiotic-Induced Persistence: Two Sides of the Same Coin? Trends Microbiol 2019; 27:339-354. [DOI: 10.1016/j.tim.2018.10.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 09/21/2018] [Accepted: 10/18/2018] [Indexed: 12/21/2022]
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Suppression of Reactive Oxygen Species Accumulation Accounts for Paradoxical Bacterial Survival at High Quinolone Concentration. Antimicrob Agents Chemother 2018; 62:AAC.01622-17. [PMID: 29229642 DOI: 10.1128/aac.01622-17] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 12/01/2017] [Indexed: 11/20/2022] Open
Abstract
When bacterial cells are exposed to increasing concentrations of quinolone-class antibacterials, survival drops, reaches a minimum, and then recovers, sometimes to 100%. Despite decades of study, events underlying this paradoxical high-concentration survival remain obscure. Since reactive oxygen species (ROS) have been implicated in antimicrobial lethality, conditions generating paradoxical survival were examined for diminished ROS accumulation. Escherichia coli cultures were treated with various concentrations of nalidixic acid, followed by measurements of survival, rate of protein synthesis, and ROS accumulation. The last measurement used a dye (carboxy-H2DCFDA) that fluoresces in the presence of ROS; fluorescence was assessed by microscopy (individual cells) and flow cytometry (batch cultures). High, nonlethal concentrations of nalidixic acid induced lower levels of ROS than moderate, lethal concentrations. Sublethal doses of exogenous hydrogen peroxide became lethal and eliminated the nalidixic acid-associated paradoxical survival. Thus, quinolone-mediated lesions needed for ROS-executed killing persist at high, nonlethal quinolone concentrations, thereby implicating ROS as a key factor in cell death. Chloramphenicol suppressed nalidixic acid-induced ROS accumulation and blocked lethality, further supporting a role for ROS in killing. Nalidixic acid also inhibited protein synthesis, with extensive inhibition at high concentrations correlating with lower ROS accumulation and paradoxical survival. A catalase deficiency, which elevated ROS levels, overcame the inhibitory effect of chloramphenicol on nalidixic acid-mediated killing, emphasizing the importance of ROS. The data collectively indicate that ROS play a dominant role in the lethal action of narrow-spectrum quinolone-class compounds; a drop in ROS levels accounted for the quinolone tolerance observed at very high concentrations.
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Paytubi S, de La Cruz M, Tormo JR, Martín J, González I, González-Menendez V, Genilloud O, Reyes F, Vicente F, Madrid C, Balsalobre C. A High-Throughput Screening Platform of Microbial Natural Products for the Discovery of Molecules with Antibiofilm Properties against Salmonella. Front Microbiol 2017; 8:326. [PMID: 28303128 PMCID: PMC5332434 DOI: 10.3389/fmicb.2017.00326] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 02/16/2017] [Indexed: 01/07/2023] Open
Abstract
In this report, we describe a High-Throughput Screening (HTS) to identify compounds that inhibit biofilm formation or cause the disintegration of an already formed biofilm using the Salmonella Enteritidis 3934 strain. Initially, we developed a new methodology for growing Salmonella biofilms suitable for HTS platforms. The biomass associated with biofilm at the solid-liquid interface was quantified by staining both with resazurin and crystal violet, to detect living cells and total biofilm mass, respectively. For a pilot project, a subset of 1120 extracts from the Fundación MEDINA's collection was examined to identify molecules with antibiofilm activity. This is the first validated HTS assay of microbial natural product extracts which allows for the detection of four types of activities which are not mutually exclusive: inhibition of biofilm formation, detachment of the preformed biofilm and antimicrobial activity against planktonic cells or biofilm embedded cells. Currently, several extracts have been selected for further fractionation and purification of the active compounds. In one of the natural extracts patulin has been identified as a potent molecule with antimicrobial activity against both, planktonic cells and cells within the biofilm. These findings provide a proof of concept that the developed HTS can lead to the discovery of new natural compounds with antibiofilm activity against Salmonella and its possible use as an alternative to antimicrobial therapies and traditional disinfectants.
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Affiliation(s)
- Sonia Paytubi
- Department de Genètica, Microbiologia i Estadística, Facultat de Biologia, Universitat de BarcelonaBarcelona, Spain
| | | | - Jose R. Tormo
- Fundación MEDINA, Parque Tecnológico de Ciencias de la SaludGranada, Spain
| | - Jesús Martín
- Fundación MEDINA, Parque Tecnológico de Ciencias de la SaludGranada, Spain
| | - Ignacio González
- Fundación MEDINA, Parque Tecnológico de Ciencias de la SaludGranada, Spain
| | | | - Olga Genilloud
- Fundación MEDINA, Parque Tecnológico de Ciencias de la SaludGranada, Spain
| | - Fernando Reyes
- Fundación MEDINA, Parque Tecnológico de Ciencias de la SaludGranada, Spain
| | - Francisca Vicente
- Fundación MEDINA, Parque Tecnológico de Ciencias de la SaludGranada, Spain
| | - Cristina Madrid
- Department de Genètica, Microbiologia i Estadística, Facultat de Biologia, Universitat de BarcelonaBarcelona, Spain
| | - Carlos Balsalobre
- Department de Genètica, Microbiologia i Estadística, Facultat de Biologia, Universitat de BarcelonaBarcelona, Spain
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Smirnova GV, Tyulenev AV, Muzyka NG, Peters MA, Oktyabrsky ON. Ciprofloxacin provokes SOS-dependent changes in respiration and membrane potential and causes alterations in the redox status of Escherichia coli. Res Microbiol 2016; 168:64-73. [PMID: 27498196 DOI: 10.1016/j.resmic.2016.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/25/2016] [Accepted: 07/27/2016] [Indexed: 10/21/2022]
Abstract
An in-depth understanding of the physiological response of bacteria to antibiotic-induced stress is needed for development of new approaches to combatting microbial infections. Fluoroquinolone ciprofloxacin causes phase alterations in Escherichia coli respiration and membrane potential that strongly depend on its concentration. Concentrations lower than the optimal bactericidal concentration (OBC) do not inhibit respiration during the first phase. A dose higher than the OBC provokes immediate SOS-independent inhibition of respiration and growth that can contribute to a decreased SOS response and lowered susceptibility to high concentrations of ciprofloxacin. Cells retain their metabolic activity, membrane potential and accelerated K+ uptake and produce low levels of superoxide and H2O2 during the first phase. The time before initiation of the second phase is inversely correlated with the ciprofloxacin concentration. The second phase is SOS-dependent and characterized by respiratory inhibition, membrane depolarization, K+ and glutathione leakage and cessation of glucose consumption and may be considered as cell death. atpA, gshA and kefBkefC knockouts, which perturb fluxes of protons and K+, can modify the degree and duration of respiratory inhibition and potassium retention. Loss of K+ efflux channels KefB and KefC enhances the susceptibility of E. coli to ciprofloxacin.
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Affiliation(s)
- Galina V Smirnova
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Aleksey V Tyulenev
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Nadezda G Muzyka
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Mikhail A Peters
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Oleg N Oktyabrsky
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia; Department of Chemistry and Biotechnology, Perm National Research Polytechnic University, Komsomolsky pr., 29, Perm, 614990, Russia.
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Toxin-Antitoxin Modules Are Pliable Switches Activated by Multiple Protease Pathways. Toxins (Basel) 2016; 8:toxins8070214. [PMID: 27409636 PMCID: PMC4963847 DOI: 10.3390/toxins8070214] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Revised: 06/24/2016] [Accepted: 06/27/2016] [Indexed: 02/06/2023] Open
Abstract
Toxin-antitoxin (TA) modules are bacterial regulatory switches that facilitate conflicting outcomes for cells by promoting a pro-survival phenotypic adaptation and/or by directly mediating cell death, all through the toxin activity upon degradation of antitoxin. Intensive study has revealed specific details of TA module functions, but significant gaps remain about the molecular details of activation via antitoxin degradation used by different bacteria and in different environments. This review summarizes the current state of knowledge about the interaction of antitoxins with cellular proteases Lon and ClpP to mediate TA module activation. An understanding of these processes can answer long-standing questions regarding stochastic versus specific activation of TA modules and provide insight into the potential for manipulation of TA modules to alter bacterial growth.
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Eagle Effect in Nonreplicating Persister Mycobacteria. Antimicrob Agents Chemother 2015; 59:7786-9. [PMID: 26349831 PMCID: PMC4649170 DOI: 10.1128/aac.01476-15] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 09/03/2015] [Indexed: 11/25/2022] Open
Abstract
We determined the microbicidal activities of antibacterials against nonreplicating Mycobacterium smegmatis grown in a starvation-based Loebel model for persistence. Whereas most drugs lost their activity, fluoroquinolones retained lethal potency. Dose-response characterizations showed a paradoxical more-drug-kills-less Eagle effect. Pretreatment of cultures with chloramphenicol blocked the lethal action of the gyrase inhibitors. These results suggest that fluoroquinolones at low concentrations trigger a protein synthesis-dependent cell death pathway and shut off this suicide pathway at elevated concentrations.
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Mustaev A, Malik M, Zhao X, Kurepina N, Luan G, Oppegard LM, Hiasa H, Marks KR, Kerns RJ, Berger JM, Drlica K. Fluoroquinolone-gyrase-DNA complexes: two modes of drug binding. J Biol Chem 2014; 289:12300-12. [PMID: 24497635 DOI: 10.1074/jbc.m113.529164] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA gyrase and topoisomerase IV control bacterial DNA topology by breaking DNA, passing duplex DNA through the break, and then resealing the break. This process is subject to reversible corruption by fluoroquinolones, antibacterials that form drug-enzyme-DNA complexes in which the DNA is broken. The complexes, called cleaved complexes because of the presence of DNA breaks, have been crystallized and found to have the fluoroquinolone C-7 ring system facing the GyrB/ParE subunits. As expected from x-ray crystallography, a thiol-reactive, C-7-modified chloroacetyl derivative of ciprofloxacin (Cip-AcCl) formed cross-linked cleaved complexes with mutant GyrB-Cys(466) gyrase as evidenced by resistance to reversal by both EDTA and thermal treatments. Surprisingly, cross-linking was also readily seen with complexes formed by mutant GyrA-G81C gyrase, thereby revealing a novel drug-gyrase interaction not observed in crystal structures. The cross-link between fluoroquinolone and GyrA-G81C gyrase correlated with exceptional bacteriostatic activity for Cip-AcCl with a quinolone-resistant GyrA-G81C variant of Escherichia coli and its Mycobacterium smegmatis equivalent (GyrA-G89C). Cip-AcCl-mediated, irreversible inhibition of DNA replication provided further evidence for a GyrA-drug cross-link. Collectively these data establish the existence of interactions between the fluoroquinolone C-7 ring and both GyrA and GyrB. Because the GyrA-Gly(81) and GyrB-Glu(466) residues are far apart (17 Å) in the crystal structure of cleaved complexes, two modes of quinolone binding must exist. The presence of two binding modes raises the possibility that multiple quinolone-enzyme-DNA complexes can form, a discovery that opens new avenues for exploring and exploiting relationships between drug structure and activity with type II DNA topoisomerases.
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Affiliation(s)
- Arkady Mustaev
- From the Public Health Research Institute and Department of Microbiology and Molecular Genetics, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Newark, New Jersey 07103
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Cheng G, Hao H, Dai M, Liu Z, Yuan Z. Antibacterial action of quinolones: From target to network. Eur J Med Chem 2013; 66:555-62. [DOI: 10.1016/j.ejmech.2013.01.057] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2012] [Revised: 01/23/2013] [Accepted: 01/26/2013] [Indexed: 11/27/2022]
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Han X, Geng J, Zhang L, Lu T. The role of Escherichia coli YrbB in the lethal action of quinolones. J Antimicrob Chemother 2010; 66:323-31. [PMID: 21098540 DOI: 10.1093/jac/dkq427] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES To explore bacterial cellular factors that protect against the lethal effect of antimicrobial stress as potential targets of antimicrobial potentiators, the role of Escherichia coli YrbB in protecting cells from quinolone-mediated cell death was studied. METHODS A set of isogenic strains containing different mutations in stress response genes of E. coli was constructed by P1-mediated transduction. The susceptibility of these strains to the lethal action of quinolones was determined by measuring viable colony counts on agar plates after treatment with quinolones under various conditions. RESULTS A yrbB mutation rendered E. coli cells more susceptible to the lethal action of quinolones under conditions in which bacteriostatic susceptibility was unaffected. YrbB worked in both lethal pathways of quinolone action. Hydroxyl radical accumulation was required for nalidixic acid-mediated killing; however, in the absence of functional YrbB there was an additional mechanism through which nalidixic acid could kill cells independently of hydroxyl radical action. The E. coli chromosomal toxin-antitoxin system ChpB, but not the SOS system, was found to be involved in the hydroxyl radical-independent lethal mechanism. In addition, proteases ClpP and Lon were also involved in the action of YrbB. Besides quinolones, YrbB also played a protective role in cellular responses to other stressors, such as mitomycin C, ultraviolet light and hydrogen peroxide. CONCLUSIONS YrbB played a protective role in the lethal action of quinolones through a hydroxyl radical-independent and toxin-antitoxin-dependent mechanism, which makes it a potential target for antimicrobial enhancement.
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Affiliation(s)
- Xiulin Han
- Yunnan Institute of Microbiology, Yunnan University, 2 Cui Hu Bei Lu, Kunming, Yunnan 650091, China
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Han X, Dorsey-Oresto A, Malik M, Wang JY, Drlica K, Zhao X, Lu T. Escherichia coli genes that reduce the lethal effects of stress. BMC Microbiol 2010; 10:35. [PMID: 20128927 PMCID: PMC2824699 DOI: 10.1186/1471-2180-10-35] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 02/04/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The continuing emergence of antimicrobial resistance requires the development of new compounds and/or enhancers of existing compounds. Genes that protect against the lethal effects of antibiotic stress are potential targets of enhancers. To distinguish such genes from those involved in drug uptake and efflux, a new susceptibility screen is required. RESULTS Transposon (Tn5)-mediated mutagenesis was used to create a library of Escherichia coli mutants that was screened for hypersensitivity to the lethal action of quinolones and counter-screened to have wild-type bacteriostatic susceptibility. Mutants with this novel "hyperlethal" phenotype were found. The phenotype was transferable to other E. coli strains by P1-mediated transduction, and for a subset of the mutants the phenotype was complemented by the corresponding wild-type gene cloned into a plasmid. Thus, the inactivation of these genes was responsible for hyperlethality. Nucleotide sequence analysis identified 14 genes, mostly of unknown function, as potential factors protecting from lethal effects of stress. The 14 mutants were killed more readily than wild-type cells by mitomycin C and hydrogen peroxide; nine were also more readily killed by UV irradiation, and several exhibited increased susceptibility to killing by sodium dodecyl sulfate. No mutant was more readily killed by high temperature. CONCLUSIONS A new screening strategy identified a diverse set of E. coli genes involved in the response to lethal antimicrobial and environmental stress, with some genes being involved in the response to multiple stressors. The gene set, which differed from sets previously identified with bacteriostatic assays, provides an entry point for obtaining small-molecule enhancers that will affect multiple antimicrobial agents.
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Affiliation(s)
- Xiulin Han
- Yunnan Institute of Microbiology, Yunnan University, 52 Cui Hu Bei Lu, Kunming, Yunnan 650091, PR China
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Van Melderen L, Aertsen A. Regulation and quality control by Lon-dependent proteolysis. Res Microbiol 2009; 160:645-51. [PMID: 19772918 DOI: 10.1016/j.resmic.2009.08.021] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 08/19/2009] [Accepted: 08/20/2009] [Indexed: 11/17/2022]
Abstract
After their first discovery in Escherichia coli, Lon homologues were found to be widely distributed among prokaryotes to eukaryotes. The ATP-dependent Lon protease belongs to the AAA(+) (ATPases associated with a variety of cellular activities) superfamily, and is involved in both general quality control by degrading abnormal proteins and in the specific control of several regulatory proteins. As such, this enzyme has a pivotal role in quality control and cellular physiology. This review focuses on mechanisms of degradation both from the protease and substrate points of view, and discusses the role of Lon in global regulation, stress response and virulence.
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Affiliation(s)
- Laurence Van Melderen
- Génétique et Physiologie Bactérienne, Université Libre de Bruxelles, Faculté des Sciences, IBMM-DBM, 12 Rue des Professeurs Jeneer et Brachet, B-6041 Gosselies, Belgium.
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Drlica K, Hiasa H, Kerns R, Malik M, Mustaev A, Zhao X. Quinolones: action and resistance updated. Curr Top Med Chem 2009; 9:981-98. [PMID: 19747119 PMCID: PMC3182077 DOI: 10.2174/156802609789630947] [Citation(s) in RCA: 235] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 07/30/2009] [Indexed: 11/22/2022]
Abstract
The quinolones trap DNA gyrase and DNA topoisomerase IV on DNA as complexes in which the DNA is broken but constrained by protein. Early studies suggested that drug binding occurs largely along helix-4 of the GyrA (gyrase) and ParC (topoisomerase IV) proteins. However, recent X-ray crystallography shows drug intercalating between the -1 and +1 nucleotides of cut DNA, with only one end of the drug extending to helix-4. These two models may reflect distinct structural steps in complex formation. A consequence of drug-enzyme-DNA complex formation is reversible inhibition of DNA replication; cell death arises from subsequent events in which bacterial chromosomes are fragmented through two poorly understood pathways. In one pathway, chromosome fragmentation stimulates excessive accumulation of highly toxic reactive oxygen species that are responsible for cell death. Quinolone resistance arises stepwise through selective amplification of mutants when drug concentrations are above the MIC and below the MPC, as observed with static agar plate assays, dynamic in vitro systems, and experimental infection of rabbits. The gap between MIC and MPC can be narrowed by compound design that should restrict the emergence of resistance. Resistance is likely to become increasingly important, since three types of plasmid-borne resistance have been reported.
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Affiliation(s)
- Karl Drlica
- Public Health Research Institute, New Jersey Medical School, UMDNJ, 225 Warren Street, Newark, NJ 07103, USA.
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