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Ładziak M, Prochwicz E, Gut K, Gomza P, Jaworska K, Ścibek K, Młyńska-Witek M, Kadej-Zajączkowska K, Lillebaek EMS, Kallipolitis BH, Krawczyk-Balska A. Inactivation of lmo0946 ( sif) induces the SOS response and MGEs mobilization and silences the general stress response and virulence program in Listeria monocytogenes. Front Microbiol 2024; 14:1324062. [PMID: 38239729 PMCID: PMC10794523 DOI: 10.3389/fmicb.2023.1324062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 12/05/2023] [Indexed: 01/22/2024] Open
Abstract
Bacteria have evolved numerous regulatory pathways to survive in changing environments. The SOS response is an inducible DNA damage repair system that plays an indispensable role in bacterial adaptation and pathogenesis. Here we report a discovery of the previously uncharacterized protein Lmo0946 as an SOS response interfering factor (Sif) in the human pathogen Listeria monocytogenes. Functional genetic studies demonstrated that sif is indispensable for normal growth of L. monocytogenes in stress-free as well as multi-stress conditions, and sif contributes to susceptibility to β-lactam antibiotics, biofilm formation and virulence. Absence of Sif promoted the SOS response and elevated expression of mobilome genes accompanied by mobilization of the A118 prophage and ICELm-1 mobile genetic elements (MGEs). These changes were found to be associated with decreased expression of general stress response genes from the σB regulon as well as virulence genes, including the PrfA regulon. Together, this study uncovers an unexpected role of a previously uncharacterized factor, Sif, as an inhibitor of the SOS response in L. monocytogenes.
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Affiliation(s)
- Magdalena Ładziak
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Emilia Prochwicz
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Karina Gut
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Patrycja Gomza
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Karolina Jaworska
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Katarzyna Ścibek
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Marta Młyńska-Witek
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Katarzyna Kadej-Zajączkowska
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Eva M. S. Lillebaek
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Birgitte H. Kallipolitis
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Agata Krawczyk-Balska
- Department of Molecular Microbiology, Biological and Chemical Research Centre, Faculty of Biology, University of Warsaw, Warsaw, Poland
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2
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Memar MY, Yekani M, Celenza G, Poortahmasebi V, Naghili B, Bellio P, Baghi HB. The central role of the SOS DNA repair system in antibiotics resistance: A new target for a new infectious treatment strategy. Life Sci 2020; 262:118562. [PMID: 33038378 DOI: 10.1016/j.lfs.2020.118562] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 09/15/2020] [Accepted: 10/01/2020] [Indexed: 01/19/2023]
Abstract
Bacteria have a considerable ability and potential to acquire resistance against antimicrobial agents by acting diverse mechanisms such as target modification or overexpression, multidrug transporter systems, and acquisition of drug hydrolyzing enzymes. Studying the mechanisms of bacterial cell physiology is mandatory for the development of novel strategies to control the antimicrobial resistance phenomenon, as well as for the control of infections in clinics. The SOS response is a cellular DNA repair mechanism that has an essential role in the bacterial biologic process involved in resistance to antibiotics. The activation of the SOS network increases the resistance and tolerance of bacteria to stress and, as a consequence, to antimicrobial agents. Therefore, SOS can be an applicable target for the discovery of new antimicrobial drugs. In the present review, we focus on the central role of SOS response in bacterial resistance mechanisms and its potential as a new target for control of resistant pathogens.
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Affiliation(s)
- Mohammad Yousef Memar
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Students' Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mina Yekani
- Department of Microbiology, Faculty of Medicine, Kashan University of Medical Sciences, Kashan, Iran; Student Research Committee, Kashan University of Medical Sciences, Kashan, Iran
| | - Giuseppe Celenza
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy.
| | - Vahdat Poortahmasebi
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Research Center for Clinical Virology, Tehran University of Medical Sciences, Tehran, Iran
| | - Behrooz Naghili
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Pierangelo Bellio
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Hossein Bannazadeh Baghi
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
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3
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Roberto AA, Van Gray JB, Engohang-Ndong J, Leff LG. Distribution and co-occurrence of antibiotic and metal resistance genes in biofilms of an anthropogenically impacted stream. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 688:437-449. [PMID: 31247485 DOI: 10.1016/j.scitotenv.2019.06.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 05/17/2019] [Accepted: 06/03/2019] [Indexed: 05/06/2023]
Abstract
Urban stream biofilms are potential hotspots for resistomes and antibiotic resistance genes (ARGs). Biofilm communities that harbor resistance genes may be influenced by contaminant input (e.g., metals and antibiotics) from urban drainage (i.e., Wastewater Treatment Plant effluent and stormwater runoff); understanding the ecology of these communities and their resistome is needed. Given the potential importance of the co-occurrence of ARGs and metal resistance genes (MRGs), we investigated the spatial and temporal distribution of three ARGs (tetracycline [tetW] and sulfonamides [sulI and sulII]), four MRGs (lead [pbrT], copper [copA], and cadmium/cobalt/zinc [czcA and czcC]) via quantitative PCR and biofilm bacterial community composition via MiSeq 16S sequencing at four time points along an urbanization gradient (i.e., developed, agriculture, and forested sites) in a stream's watershed. Our results revealed that ARG and MRG abundances were significantly affected by land use-time interaction, with greater resistance abundances occurring in more urban locations during particular times of the year. It was also observed that changes in ARG and MRG profiles were influenced by differences in community composition among land use types, and that these differences were in response to changes in stream physicochemical parameters (pH, redox, temperature, nutrient availability, and metal concentration) that were driven by sub-watershed land use. Moreover, the dynamics between ARGs and MRGs within these communities correlated strongly and positively with one another. Taken altogether, our results demonstrate that changes in environmental properties due to human activity may drive the ARG-MRG profiles of biofilm communities by modulating community structure over time and space.
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Affiliation(s)
- Alescia A Roberto
- Department of Biological Sciences, Kent State University, Kent, OH 44242, United States of America.
| | - Jonathon B Van Gray
- Department of Biological Sciences, Kent State University, Kent, OH 44242, United States of America.
| | - Jean Engohang-Ndong
- Department of Biological Sciences, Kent State University at Tuscarawas, New Philadelphia, OH 44663, United States of America.
| | - Laura G Leff
- Department of Biological Sciences, Kent State University, Kent, OH 44242, United States of America.
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4
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Huang H, Zheng X, Yang S, Chen Y. More than sulfidation: Roles of biogenic sulfide in attenuating the impacts of CuO nanoparticle on antibiotic resistance genes during sludge anaerobic digestion. WATER RESEARCH 2019; 158:1-10. [PMID: 31004981 DOI: 10.1016/j.watres.2019.04.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 04/07/2019] [Accepted: 04/09/2019] [Indexed: 06/09/2023]
Abstract
Biogenic sulfide (BS) in anaerobic digesters was previously suggested to mitigate the potential impacts of metallic nanoparticles (M-NPs) on antibiotic resistance genes (ARGs) propagation by sulfidation of the M-NPs. In this study, a new role of BS in regulating ARGs responses to M-NPs is reported. It was observed that CuO NPs at environmentally relevant level had no significant effects on the spread of ARGs. However, higher dosage (50 mg/gTSS) contributed to the propagation of ARGs, whose abundances would be effectively reduced by 74-115% if BS production was stimulated. Instead, introduction of EDTA, a metal ion chelator, resulted in much lower attenuation efficiencies (12-40%), indicating that restriction of the bioavailability of CuO NPs might not be the only reason for the buffering of ARG responses in the presence of BS. Further investigation showed that the presence of BS together with activation of key enzymes (O-acetyl serine sulfhydrylase and γ-glutamylcysteine synthetase) supplied and favored the biosynthesis and transformation of cysteine, which mitigated the oxidative stress induced by CuO NPs. Moreover, the amounts of cysteine and its metabolite glutathione in sludge were associated with the abundances of ARGs negatively, implying that in situ generated cysteine was the important ARGs regulator. Exploration of possible mechanisms revealed that the biosynthesized cysteine might limit gene transfer potential via mobile genetic elements, as cysteine restricted the abundances of intI 1, Tn916/1545 and ISCR 1. In addition, the cysteine remarkably alleviated the copper stress and copper resistance, which in turn blocked possible co-selection between copper and antibiotic resistance. This work provides new insight into attenuation of the bio-effects of NPs in digesters.
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Affiliation(s)
- Haining Huang
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China
| | - Xiong Zheng
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China.
| | - Shouye Yang
- State Key Laboratory of Marine Geology, School of Ocean and Earth Science, Tongji University, 1239 Siping Road, Shanghai, 200092, China
| | - Yinguang Chen
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China.
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5
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Browning DF, Butala M, Busby SJW. Bacterial Transcription Factors: Regulation by Pick "N" Mix. J Mol Biol 2019; 431:4067-4077. [PMID: 30998934 DOI: 10.1016/j.jmb.2019.04.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 04/03/2019] [Accepted: 04/08/2019] [Indexed: 10/27/2022]
Abstract
Transcription in most bacteria is tightly regulated in order to facilitate bacterial adaptation to different environments, and transcription factors play a key role in this. Here we give a brief overview of the essential features of bacterial transcription factors and how they affect transcript initiation at target promoters. We focus on complex promoters that are regulated by combinations of activators and repressors, combinations of repressors only, or combinations of activators. At some promoters, transcript initiation is regulated by nucleoid-associated proteins, which often work together with transcription factors. We argue that the distinction between nucleoid-associated proteins and transcription factors is blurred and that they likely share common origins.
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Affiliation(s)
- Douglas F Browning
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Matej Butala
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia
| | - Stephen J W Busby
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK.
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6
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Bourges AC, Torres Montaguth OE, Ghosh A, Tadesse WM, Declerck N, Aertsen A, Royer CA. High pressure activation of the Mrr restriction endonuclease in Escherichia coli involves tetramer dissociation. Nucleic Acids Res 2017; 45:5323-5332. [PMID: 28369499 PMCID: PMC5435990 DOI: 10.1093/nar/gkx192] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 03/14/2017] [Indexed: 01/07/2023] Open
Abstract
A sub-lethal hydrostatic pressure (HP) shock of ∼100 MPa elicits a RecA-dependent DNA damage (SOS) response in Escherichia coli K-12, despite the fact that pressure cannot compromise the covalent integrity of DNA. Prior screens for HP resistance identified Mrr (Methylated adenine Recognition and Restriction), a Type IV restriction endonuclease (REase), as instigator for this enigmatic HP-induced SOS response. Type IV REases tend to target modified DNA sites, and E. coli Mrr activity was previously shown to be elicited by expression of the foreign M.HhaII Type II methytransferase (MTase), as well. Here we measured the concentration and stoichiometry of a functional GFP-Mrr fusion protein using in vivo fluorescence fluctuation microscopy. Our results demonstrate that Mrr is a tetramer in unstressed cells, but shifts to a dimer after HP shock or co-expression with M.HhaII. Based on the differences in reversibility of tetramer dissociation observed for wild-type GFP-Mrr and a catalytic mutant upon HP shock compared to M.HhaII expression, we propose a model by which (i) HP triggers Mrr activity by directly pushing inactive Mrr tetramers to dissociate into active Mrr dimers, while (ii) M.HhaII triggers Mrr activity by creating high affinity target sites on the chromosome, which pull the equilibrium from inactive tetrameric Mrr toward active dimer.
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Affiliation(s)
- Anaïs C Bourges
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.,Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Université Montpellier, 34000 Montpellier, France
| | - Oscar E Torres Montaguth
- Department of Microbial and Molecular Systems, Laboratory of Food Microbiology, KU Leuven, B-3001 Leuven, Belgium
| | - Anirban Ghosh
- Department of Microbial and Molecular Systems, Laboratory of Food Microbiology, KU Leuven, B-3001 Leuven, Belgium
| | - Wubishet M Tadesse
- Department of Microbial and Molecular Systems, Laboratory of Food Microbiology, KU Leuven, B-3001 Leuven, Belgium
| | - Nathalie Declerck
- Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Université Montpellier, 34000 Montpellier, France
| | - Abram Aertsen
- Department of Microbial and Molecular Systems, Laboratory of Food Microbiology, KU Leuven, B-3001 Leuven, Belgium
| | - Catherine A Royer
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
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7
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Miller J, Novak J, Knocke W, Pruden A. Elevation of antibiotic resistance genes at cold temperatures: implications for winter storage of sludge and biosolids. Lett Appl Microbiol 2014; 59:587-93. [DOI: 10.1111/lam.12325] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 08/06/2014] [Accepted: 08/23/2014] [Indexed: 11/30/2022]
Affiliation(s)
- J.H. Miller
- Charles E. Via, Jr. Department of Civil and Environmental Engineering; Virginia Tech; Blacksburg VA USA
| | - J.T. Novak
- Charles E. Via, Jr. Department of Civil and Environmental Engineering; Virginia Tech; Blacksburg VA USA
| | - W.R. Knocke
- Charles E. Via, Jr. Department of Civil and Environmental Engineering; Virginia Tech; Blacksburg VA USA
| | - A. Pruden
- Charles E. Via, Jr. Department of Civil and Environmental Engineering; Virginia Tech; Blacksburg VA USA
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8
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Roy Chowdhury P, McKinnon J, Wyrsch E, Hammond JM, Charles IG, Djordjevic SP. Genomic interplay in bacterial communities: implications for growth promoting practices in animal husbandry. Front Microbiol 2014; 5:394. [PMID: 25161648 PMCID: PMC4129626 DOI: 10.3389/fmicb.2014.00394] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 07/14/2014] [Indexed: 12/22/2022] Open
Abstract
The discovery of antibiotics heralded the start of a “Golden Age” in the history of medicine. Over the years, the use of antibiotics extended beyond medical practice into animal husbandry, aquaculture and agriculture. Now, however, we face the worldwide threat of diseases caused by pathogenic bacteria that are resistant to all existing major classes of antibiotic, reflecting the possibility of an end to the antibiotic era. The seriousness of the threat is underscored by the severely limited production of new classes of antibiotics. Evolution of bacteria resistant to multiple antibiotics results from the inherent genetic capability that bacteria have to adapt rapidly to changing environmental conditions. Consequently, under antibiotic selection pressures, bacteria have acquired resistance to all classes of antibiotics, sometimes very shortly after their introduction. Arguably, the evolution and rapid dissemination of multiple drug resistant genes en-masse across microbial pathogens is one of the most serious threats to human health. In this context, effective surveillance strategies to track the development of resistance to multiple antibiotics are vital to managing global infection control. These surveillance strategies are necessary for not only human health but also for animal health, aquaculture and plant production. Shortfalls in the present surveillance strategies need to be identified. Raising awareness of the genetic events that promote co-selection of resistance to multiple antimicrobials is an important prerequisite to the design and implementation of molecular surveillance strategies. In this review we will discuss how lateral gene transfer (LGT), driven by the use of low-dose antibiotics in animal husbandry, has likely played a significant role in the evolution of multiple drug resistance (MDR) in Gram-negative bacteria and has complicated molecular surveillance strategies adopted for predicting imminent resistance threats.
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Affiliation(s)
- Piklu Roy Chowdhury
- The ithree institute, University of Technology Sydney Sydney, NSW, Australia ; NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute Camden, NSW, Australia
| | - Jessica McKinnon
- The ithree institute, University of Technology Sydney Sydney, NSW, Australia
| | - Ethan Wyrsch
- The ithree institute, University of Technology Sydney Sydney, NSW, Australia
| | - Jeffrey M Hammond
- NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute Camden, NSW, Australia
| | - Ian G Charles
- The ithree institute, University of Technology Sydney Sydney, NSW, Australia
| | - Steven P Djordjevic
- The ithree institute, University of Technology Sydney Sydney, NSW, Australia
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9
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Ghosh A, Passaris I, Tesfazgi Mebrhatu M, Rocha S, Vanoirbeek K, Hofkens J, Aertsen A. Cellular localization and dynamics of the Mrr type IV restriction endonuclease of Escherichia coli. Nucleic Acids Res 2014; 42:3908-18. [PMID: 24423871 PMCID: PMC3973329 DOI: 10.1093/nar/gkt1370] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
In this study, we examined the intracellular whereabouts of Mrr, a cryptic type IV restriction endonuclease of Escherichia coli K12, in response to different conditions. In absence of stimuli triggering its activity, Mrr was found to be strongly associated with the nucleoid as a number of discrete foci, suggesting the presence of Mrr hotspots on the chromosome. Previously established elicitors of Mrr activity, such as exposure to high (hydrostatic) pressure (HP) or expression of the HhaII methyltransferase, both caused nucleoid condensation and an unexpected coalescence of Mrr foci. However, although the resulting Mrr/nucleoid complex was stable when triggered with HhaII, it tended to be only short-lived when elicited with HP. Moreover, HP-mediated activation of Mrr typically led to cellular blebbing, suggesting a link between chromosome and cellular integrity. Interestingly, Mrr variants could be isolated that were specifically compromised in either HhaII- or HP-dependent activation, underscoring a mechanistic difference in the way both triggers activate Mrr. In general, our results reveal that Mrr can take part in complex spatial distributions on the nucleoid and can be engaged in distinct modes of activity.
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Affiliation(s)
- Anirban Ghosh
- Department of Microbial and Molecular Systems (M2S), Laboratory of Food Microbiology, KU Leuven, B-3001 Leuven, Belgium and Department of Chemistry, KU Leuven, B-3001 Leuven, Belgium
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10
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Kreuzer KN. DNA damage responses in prokaryotes: regulating gene expression, modulating growth patterns, and manipulating replication forks. Cold Spring Harb Perspect Biol 2013; 5:a012674. [PMID: 24097899 DOI: 10.1101/cshperspect.a012674] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Recent advances in the area of bacterial DNA damage responses are reviewed here. The SOS pathway is still the major paradigm of bacterial DNA damage response, and recent studies have clarified the mechanisms of SOS induction and key physiological roles of SOS including a very major role in genetic exchange and variation. When considering diverse bacteria, it is clear that SOS is not a uniform pathway with one purpose, but rather a platform that has evolved for differing functions in different bacteria. Relating in part to the SOS response, the field has uncovered multiple apparent cell-cycle checkpoints that assist cell survival after DNA damage and remarkable pathways that induce programmed cell death in bacteria. Bacterial DNA damage responses are also much broader than SOS, and several important examples of LexA-independent regulation will be reviewed. Finally, some recent advances that relate to the replication and repair of damaged DNA will be summarized.
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Affiliation(s)
- Kenneth N Kreuzer
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
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11
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A replication-inhibited unsegregated nucleoid at mid-cell blocks Z-ring formation and cell division independently of SOS and the SlmA nucleoid occlusion protein in Escherichia coli. J Bacteriol 2013; 196:36-49. [PMID: 24142249 DOI: 10.1128/jb.01230-12] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chromosome replication and cell division of Escherichia coli are coordinated with growth such that wild-type cells divide once and only once after each replication cycle. To investigate the nature of this coordination, the effects of inhibiting replication on Z-ring formation and cell division were tested in both synchronized and exponentially growing cells with only one replicating chromosome. When replication elongation was blocked by hydroxyurea or nalidixic acid, arrested cells contained one partially replicated, compact nucleoid located mid-cell. Cell division was strongly inhibited at or before the level of Z-ring formation. DNA cross-linking by mitomycin C delayed segregation, and the accumulation of about two chromosome equivalents at mid-cell also blocked Z-ring formation and cell division. Z-ring inhibition occurred independently of SOS, SlmA-mediated nucleoid occlusion, and MinCDE proteins and did not result from a decreased FtsZ protein concentration. We propose that the presence of a compact, incompletely replicated nucleoid or unsegregated chromosome masses at the normal mid-cell division site inhibits Z-ring formation and that the SOS system, SlmA, and MinC are not required for this inhibition.
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12
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Fonseca LS, da Silva JB, Milanez JS, Monteiro-Vitorello CB, Momo L, de Morais ZM, Vasconcellos SA, Marques MV, Ho PL, da Costa RMA. Leptospira interrogans serovar copenhageni harbors two lexA genes involved in SOS response. PLoS One 2013; 8:e76419. [PMID: 24098496 PMCID: PMC3789691 DOI: 10.1371/journal.pone.0076419] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 08/28/2013] [Indexed: 11/24/2022] Open
Abstract
Bacteria activate a regulatory network in response to the challenges imposed by DNA damage to genetic material, known as the SOS response. This system is regulated by the RecA recombinase and by the transcriptional repressor lexA. Leptospira interrogans is a pathogen capable of surviving in the environment for weeks, being exposed to a great variety of stress agents and yet retaining its ability to infect the host. This study aims to investigate the behavior of L. interrogans serovar Copenhageni after the stress induced by DNA damage. We show that L. interrogans serovar Copenhageni genome contains two genes encoding putative LexA proteins (lexA1 and lexA2) one of them being potentially acquired by lateral gene transfer. Both genes are induced after DNA damage, but the steady state levels of both LexA proteins drop, probably due to auto-proteolytic activity triggered in this condition. In addition, seven other genes were up-regulated following UV-C irradiation, recA, recN, dinP, and four genes encoding hypothetical proteins. This set of genes is potentially regulated by LexA1, as it showed binding to their promoter regions. All these regions contain degenerated sequences in relation to the previously described SOS box, TTTGN 5CAAA. On the other hand, LexA2 was able to bind to the palindrome TTGTAN10TACAA, found in its own promoter region, but not in the others. Therefore, the L. interrogans serovar Copenhageni SOS regulon may be even more complex, as a result of LexA1 and LexA2 binding to divergent motifs. New possibilities for DNA damage response in Leptospira are expected, with potential influence in other biological responses such as virulence.
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Affiliation(s)
- Luciane S Fonseca
- Centro de Biotecnologia, Instituto Butantan, São Paulo, Brazil ; Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
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13
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Cellular Filamentation After Sublethal High-Pressure Shock in Escherichia coli K12 is Mrr Dependent. Curr Microbiol 2013; 67:522-4. [DOI: 10.1007/s00284-013-0449-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2013] [Accepted: 08/02/2013] [Indexed: 10/26/2022]
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14
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Bernier SP, Surette MG. Concentration-dependent activity of antibiotics in natural environments. Front Microbiol 2013; 4:20. [PMID: 23422936 PMCID: PMC3574975 DOI: 10.3389/fmicb.2013.00020] [Citation(s) in RCA: 145] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Accepted: 01/28/2013] [Indexed: 11/26/2022] Open
Abstract
Bacterial responses to antibiotics are concentration-dependent. At high concentrations, antibiotics exhibit antimicrobial activities on susceptible cells, while subinhibitory concentrations induce diverse biological responses in bacteria. At non-lethal concentrations, bacteria may sense antibiotics as extracellular chemicals to trigger different cellular responses, which may include an altered antibiotic resistance/tolerance profile. In natural settings, microbes are typically in polymicrobial communities and antibiotic-mediated interactions between species may play a significant role in bacterial community structure and function. However, these aspects have not yet fully been explored at the community level. Here we discuss the different types of interactions mediated by antibiotics and non-antibiotic metabolites as a function of their concentrations and speculate on how these may amplify the overall antibiotic resistance/tolerance and the spread of antibiotic resistance determinants in a context of polymicrobial community.
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Affiliation(s)
- Steve P Bernier
- Farncombe Family Digestive Health Research Institute, Department of Medicine, Faculty of Health Sciences, McMaster University Hamilton, ON, Canada
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15
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Gillings MR. Evolutionary consequences of antibiotic use for the resistome, mobilome and microbial pangenome. Front Microbiol 2013; 4:4. [PMID: 23386843 PMCID: PMC3560386 DOI: 10.3389/fmicb.2013.00004] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 01/03/2013] [Indexed: 12/16/2022] Open
Abstract
The widespread use and abuse of antibiotic therapy has evolutionary and ecological consequences, some of which are only just beginning to be examined. One well known consequence is the fixation of mutations and lateral gene transfer (LGT) events that confer antibiotic resistance. Sequential selection events, driven by different classes of antibiotics, have resulted in the assembly of diverse resistance determinants and mobile DNAs into novel genetic elements of ever-growing complexity and flexibility. These novel plasmids, integrons, and genomic islands have now become fixed at high frequency in diverse cell lineages by human antibiotic use. Consequently they can be regarded as xenogenetic pollutants, analogous to xenobiotic compounds, but with the critical distinction that they replicate rather than degrade when released to pollute natural environments. Antibiotics themselves must also be regarded as pollutants, since human production overwhelms natural synthesis, and a major proportion of ingested antibiotic is excreted unchanged into waste streams. Such antibiotic pollutants have non-target effects, raising the general rates of mutation, recombination, and LGT in all the microbiome, and simultaneously providing the selective force to fix such changes. This has the consequence of recruiting more genes into the resistome and mobilome, and of increasing the overlap between these two components of microbial genomes. Thus the human use and environmental release of antibiotics is having second order effects on the microbial world, because these small molecules act as drivers of bacterial evolution. Continued pollution with both xenogenetic elements and the selective agents that fix such elements in populations has potentially adverse consequences for human welfare.
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Affiliation(s)
- Michael R Gillings
- Department of Biological Sciences, Macquarie University Sydney, NSW, Australia
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16
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Crabbé A, Leroy B, Wattiez R, Aertsen A, Leys N, Cornelis P, Van Houdt R. Differential proteomics and physiology of Pseudomonas putida KT2440 under filament-inducing conditions. BMC Microbiol 2012. [PMID: 23186381 PMCID: PMC3538555 DOI: 10.1186/1471-2180-12-282] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Background Pseudomonas putida exerts a filamentous phenotype in response to environmental stress conditions that are encountered during its natural life cycle. This study assessed whether P. putida filamentation could confer survival advantages. Filamentation of P. putida was induced through culturing at low shaking speed and was compared to culturing in high shaking speed conditions, after which whole proteomic analysis and stress exposure assays were performed. Results P. putida grown in filament-inducing conditions showed increased resistance to heat and saline stressors compared to non-filamented cultures. Proteomic analysis showed a significant metabolic change and a pronounced induction of the heat shock protein IbpA and recombinase RecA in filament-inducing conditions. Our data further indicated that the associated heat shock resistance, but not filamentation, was dependent of RecA. Conclusions This study provides insights into the altered metabolism of P. putida in filament-inducing conditions, and indicates that the formation of filaments could potentially be utilized by P. putida as a survival strategy in its hostile, recurrently changing habitat.
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Affiliation(s)
- Aurélie Crabbé
- Unit of Microbiology, Expert Group Molecular and Cellular Biology, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium
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17
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Aminov RI. Horizontal gene exchange in environmental microbiota. Front Microbiol 2011; 2:158. [PMID: 21845185 PMCID: PMC3145257 DOI: 10.3389/fmicb.2011.00158] [Citation(s) in RCA: 354] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 07/11/2011] [Indexed: 01/21/2023] Open
Abstract
Horizontal gene transfer (HGT) plays an important role in the evolution of life on the Earth. This view is supported by numerous occasions of HGT that are recorded in the genomes of all three domains of living organisms. HGT-mediated rapid evolution is especially noticeable among the Bacteria, which demonstrate formidable adaptability in the face of recent environmental changes imposed by human activities, such as the use of antibiotics, industrial contamination, and intensive agriculture. At the heart of the HGT-driven bacterial evolution and adaptation are highly sophisticated natural genetic engineering tools in the form of a variety of mobile genetic elements (MGEs). The main aim of this review is to give a brief account of the occurrence and diversity of MGEs in natural ecosystems and of the environmental factors that may affect MGE-mediated HGT.
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Affiliation(s)
- Rustam I Aminov
- Rowett Institute of Nutrition and Health, University of Aberdeen Aberdeen, UK
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18
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Stokes HW, Gillings MR. Gene flow, mobile genetic elements and the recruitment of antibiotic resistance genes into Gram-negative pathogens. FEMS Microbiol Rev 2011; 35:790-819. [PMID: 21517914 DOI: 10.1111/j.1574-6976.2011.00273.x] [Citation(s) in RCA: 372] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Antibiotics were one of the great discoveries of the 20th century. However, resistance appeared even in the earliest years of the antibiotic era. Antibiotic resistance continues to become worse, despite the ever-increasing resources devoted to combat the problem. One of the most important factors in the development of resistance to antibiotics is the remarkable ability of bacteria to share genetic resources via Lateral Gene Transfer (LGT). LGT occurs on a global scale, such that in theory, any gene in any organism anywhere in the microbial biosphere might be mobilized and spread. With sufficiently strong selection, any gene may spread to a point where it establishes a global presence. From an antibiotic resistance perspective, this means that a resistance phenotype can appear in a diverse range of infections around the globe nearly simultaneously. We discuss the forces and agents that make this LGT possible and argue that the problem of resistance can ultimately only be managed by understanding the problem from a broad ecological and evolutionary perspective. We also argue that human activities are exacerbating the problem by increasing the tempo of LGT and bacterial evolution for many traits that are important to humans.
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Affiliation(s)
- Hatch W Stokes
- The i3 Institute, University of Technology, Broadway 2007, Sydney, NSW, Australia.
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19
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Cambray G, Sanchez-Alberola N, Campoy S, Guerin É, Da Re S, González-Zorn B, Ploy MC, Barbé J, Mazel D, Erill I. Prevalence of SOS-mediated control of integron integrase expression as an adaptive trait of chromosomal and mobile integrons. Mob DNA 2011; 2:6. [PMID: 21529368 PMCID: PMC3108266 DOI: 10.1186/1759-8753-2-6] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 04/30/2011] [Indexed: 11/26/2022] Open
Abstract
Background Integrons are found in hundreds of environmental bacterial species, but are mainly known as the agents responsible for the capture and spread of antibiotic-resistance determinants between Gram-negative pathogens. The SOS response is a regulatory network under control of the repressor protein LexA targeted at addressing DNA damage, thus promoting genetic variation in times of stress. We recently reported a direct link between the SOS response and the expression of integron integrases in Vibrio cholerae and a plasmid-borne class 1 mobile integron. SOS regulation enhances cassette swapping and capture in stressful conditions, while freezing the integron in steady environments. We conducted a systematic study of available integron integrase promoter sequences to analyze the extent of this relationship across the Bacteria domain. Results Our results showed that LexA controls the expression of a large fraction of integron integrases by binding to Escherichia coli-like LexA binding sites. In addition, the results provide experimental validation of LexA control of the integrase gene for another Vibrio chromosomal integron and for a multiresistance plasmid harboring two integrons. There was a significant correlation between lack of LexA control and predicted inactivation of integrase genes, even though experimental evidence also indicates that LexA regulation may be lost to enhance expression of integron cassettes. Conclusions Ancestral-state reconstruction on an integron integrase phylogeny led us to conclude that the ancestral integron was already regulated by LexA. The data also indicated that SOS regulation has been actively preserved in mobile integrons and large chromosomal integrons, suggesting that unregulated integrase activity is selected against. Nonetheless, additional adaptations have probably arisen to cope with unregulated integrase activity. Identifying them may be fundamental in deciphering the uneven distribution of integrons in the Bacteria domain.
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Affiliation(s)
- Guillaume Cambray
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS URA 2171, 75015 Paris, France
| | - Neus Sanchez-Alberola
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.,Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
| | - Susana Campoy
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - Émilie Guerin
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Sandra Da Re
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Bruno González-Zorn
- Departamento de Sanidad Animal, Facultad de Veterinaria, and VISAVET, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Marie-Cécile Ploy
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Jordi Barbé
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
| | - Didier Mazel
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS URA 2171, 75015 Paris, France
| | - Ivan Erill
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
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Affiliation(s)
- Guillaume Cambray,
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, F-75015 Paris, France;
- CNRS, URA2171, F-75015 Paris, France
| | - Anne-Marie Guerout,
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, F-75015 Paris, France;
- CNRS, URA2171, F-75015 Paris, France
| | - Didier Mazel
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, F-75015 Paris, France;
- CNRS, URA2171, F-75015 Paris, France
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21
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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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22
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Guerin E, Cambray G, Sanchez-Alberola N, Campoy S, Erill I, Da Re S, Gonzalez-Zorn B, Barbé J, Ploy MC, Mazel D. The SOS response controls integron recombination. Science 2009; 324:1034. [PMID: 19460999 DOI: 10.1126/science.1172914] [Citation(s) in RCA: 289] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Integrons are found in the genome of hundreds of environmental bacteria but are mainly known for their role in the capture and spread of antibiotic resistance determinants among Gram-negative pathogens. We report a direct link between this system and the ubiquitous SOS response. We found that LexA controlled expression of most integron integrases and consequently regulated cassette recombination. This regulatory coupling enhanced the potential for cassette swapping and capture in cells under stress, while minimizing cassette rearrangements or loss in constant environments. This finding exposes integrons as integrated adaptive systems and has implications for antibiotic treatment policies.
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Affiliation(s)
- Emilie Guerin
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, 87000 Limoges, France
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23
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Mertens K, Lantsheer L, Ennis DG, Samuel JE. Constitutive SOS expression and damage-inducible AddAB-mediated recombinational repair systems for Coxiella burnetii as potential adaptations for survival within macrophages. Mol Microbiol 2008; 69:1411-26. [PMID: 18647165 DOI: 10.1111/j.1365-2958.2008.06373.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
SUMMARY Coxiella burnetii, a Gram-negative obligate intracellular pathogen, replicates within an parasitophorous vacuole with lysosomal characteristics. To understand how C. burnetii maintains genomic integrity in this environment, a database search for genes involved in DNA repair was performed. Major components of repair, SOS response and recombination were identified, including recA and ruvABC, but lexA and recBCD were absent. Instead, C. burnetii possesses addAB orthologous genes, functional equivalents to recBCD. Survival after treatment with UV, mitomycin C (MC) or methyl methanesulfonate (MMS), as well as homologous recombination in Hfr mating was restored in Escherichia coli deletion strains by C. burnetii recA or addAB. Despite the absence of LexA, co-protease activity for C. burnetii RecA was demonstrated. Dominant-negative inhibition of C. burnetii RecA by recA mutant alleles, modelled after E. coli recA1 and recA56, was observed and more apparent with expression of C. burnetii RecAG159D mutant protein. Expression of a subset of repair genes in C. burnetii was monitored and, in contrast to the non-inducible E. coli recBCD, addAB expression was strongly upregulated under oxidative stress. Constitutive SOS gene expression due to the lack of LexA and induction of AddAB likely reflect a unique repair adaptation of C. burnetii to its hostile niche.
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Affiliation(s)
- Katja Mertens
- Department of Microbial and Molecular Pathogenesis, Texas A&M Health Science Center, College of Medicine, College Station, TX, USA
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24
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Abstract
Bacteria spend their lives buffeted by changing environmental conditions. To adapt to and survive these stresses, bacteria have global response systems that result in sweeping changes in gene expression and cellular metabolism. These responses are controlled by master regulators, which include: alternative sigma factors, such as RpoS and RpoH; small molecule effectors, such as ppGpp; gene repressors such as LexA; and, inorganic molecules, such as polyphosphate. The response pathways extensively overlap and are induced to various extents by the same environmental stresses. These stresses include nutritional deprivation, DNA damage, temperature shift, and exposure to antibiotics. All of these global stress responses include functions that can increase genetic variability. In particular, up-regulation and activation of error-prone DNA polymerases, down-regulation of error-correcting enzymes, and movement of mobile genetic elements are common features of several stress responses. The result is that under a variety of stressful conditions, bacteria are induced for genetic change. This transient mutator state may be important for adaptive evolution.
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Affiliation(s)
- Patricia L Foster
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
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25
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Aertsen A, Tesfazgi Mebrhatu M, Michiels CW. Activation of the Salmonella typhimurium Mrr protein. Biochem Biophys Res Commun 2008; 367:435-9. [PMID: 18178154 DOI: 10.1016/j.bbrc.2007.12.151] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2007] [Accepted: 12/26/2007] [Indexed: 11/18/2022]
Abstract
The Mrr protein of Escherichia coli K12 is a cryptic type IV restriction endonuclease with specificity for methylated DNA. Recently it was discovered that endogenous activation of E. coli Mrr could be triggered by high pressure stress, resulting in the generation of double strand breaks in the host chromosome and concomitant induction of the SOS response. In this report we focused on Mrr activity of Salmonella Typhimurium LT2, and although we surprisingly found no evidence of high pressure induced activation, a large number of constitutively activated Mrr mutants could be isolated when the mrr gene was routinely cloned in an expression vector. Analysis of several spontaneous mutants revealed different single mutations that rendered the Mrr protein constitutively active. Moreover, a spontaneous S. Typhimurium mutant could be isolated that displayed an increased basal SOS induction because of a point mutation in the chromosomal mrr gene. Based on these findings the physiological role of Mrr in the cell is discussed.
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Affiliation(s)
- Abram Aertsen
- Laboratory of Food Microbiology, Centre for Food and Microbial Technology, Department of Microbial and Molecular Systems (M(2)S), Faculty of Bioscience Engineering, K.U.Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
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Abstract
According to classical evolutionary theory, phenotypic variation originates from random mutations that are independent of selective pressure. However, recent findings suggest that organisms have evolved mechanisms to influence the timing or genomic location of heritable variability. Hypervariable contingency loci and epigenetic switches increase the variability of specific phenotypes; error-prone DNA replicases produce bursts of variability in times of stress. Interestingly, these mechanisms seem to tune the variability of a given phenotype to match the variability of the acting selective pressure. Although these observations do not undermine Darwin's theory, they suggest that selection and variability are less independent than once thought.
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Affiliation(s)
- Oliver J Rando
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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