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Atasoy M, Bartkova S, Çetecioğlu-Gürol Z, P Mira N, O'Byrne C, Pérez-Rodríguez F, Possas A, Scheler O, Sedláková-Kaduková J, Sinčák M, Steiger M, Ziv C, Lund PA. Methods for studying microbial acid stress responses: from molecules to populations. FEMS Microbiol Rev 2024; 48:fuae015. [PMID: 38760882 PMCID: PMC11418653 DOI: 10.1093/femsre/fuae015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 03/27/2024] [Accepted: 05/16/2024] [Indexed: 05/20/2024] Open
Abstract
The study of how micro-organisms detect and respond to different stresses has a long history of producing fundamental biological insights while being simultaneously of significance in many applied microbiological fields including infection, food and drink manufacture, and industrial and environmental biotechnology. This is well-illustrated by the large body of work on acid stress. Numerous different methods have been used to understand the impacts of low pH on growth and survival of micro-organisms, ranging from studies of single cells to large and heterogeneous populations, from the molecular or biophysical to the computational, and from well-understood model organisms to poorly defined and complex microbial consortia. Much is to be gained from an increased general awareness of these methods, and so the present review looks at examples of the different methods that have been used to study acid resistance, acid tolerance, and acid stress responses, and the insights they can lead to, as well as some of the problems involved in using them. We hope this will be of interest both within and well beyond the acid stress research community.
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Affiliation(s)
- Merve Atasoy
- UNLOCK, Wageningen University and Research, PO Box 9101, 6700 HB, the Netherlands
| | - Simona Bartkova
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
| | - Zeynep Çetecioğlu-Gürol
- Department of Industrial Biotechnology, KTH Royal Institute of Technology, Roslagstullsbacken 21 106 91 Stockholm, Stockholm, Sweden
| | - Nuno P Mira
- iBB, Institute for Bioengineering and Biosciences, Department of Bioengineering, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
- Associate Laboratory i4HB, Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Conor O'Byrne
- Microbiology, School of Biological and Chemical Sciences, University of Galway, University Road, Galway, H91 TK33, Ireland
| | - Fernando Pérez-Rodríguez
- Department of Food Science and Tehcnology, UIC Zoonosis y Enfermedades Emergentes ENZOEM, University of Córdoba, 14014 Córdoba, Spain
| | - Aricia Possas
- Department of Food Science and Tehcnology, UIC Zoonosis y Enfermedades Emergentes ENZOEM, University of Córdoba, 14014 Córdoba, Spain
| | - Ott Scheler
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
| | - Jana Sedláková-Kaduková
- Institute of Chemistry and Environmental Sciences, University of Ss. Cyril and Methodius, 91701 Trnava, Republic of Slovakia
| | - Mirka Sinčák
- Institute of Chemistry and Environmental Sciences, University of Ss. Cyril and Methodius, 91701 Trnava, Republic of Slovakia
| | - Matthias Steiger
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria
| | - Carmit Ziv
- Department of Postharvest Science, Agricultural Research Organization, Volcani Center, 7505101 Rishon LeZion, Israel
| | - Peter A Lund
- School of Biosciences and Institute of Microbiology of Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
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Yammine J, Doulgeraki AI, O'Byrne CP, Gharsallaoui A, Chihib NE, Karam L. The impact of different acidic conditions and food substrates on Listeria monocytogenes biofilms development and removal using nanoencapsulated carvacrol. Int J Food Microbiol 2024; 416:110676. [PMID: 38507974 DOI: 10.1016/j.ijfoodmicro.2024.110676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 02/16/2024] [Accepted: 03/09/2024] [Indexed: 03/22/2024]
Abstract
Listeria monocytogenes biofilms present a significant challenge in the food industry. This study explores the impact of different acidic conditions of culture media and food matrices on the development and removal of biofilms developed on stainless steel surfaces by wild-type (WT) L. monocytogenes strains as well as in two mutant derivatives, ΔsigB and ΔagrA, that have defects in the general stress response and quorum sensing, respectively. Additionally, the study investigates the efficacy of nanoencapsulated carvacrol as an antimicrobial against L. monocytogenes biofilms developed in Tryptic Soy Broth (TSB) culture media acidified to different pH conditions (3.5, 4.5, 5.5, 6.5), and in food substrates (apple juice, strained yogurt, vegetable soup, semi-skimmed milk) having the same pH levels. No biofilm formation was observed for all L. monocytogenes strains at pH levels of 3.5 and 4.5 in both culture media and food substrates. However, at pH 5.5 and 6.5, increased biofilm levels were observed in both the culture media and food substrates, with the WT strain showing significantly higher biofilm formation (3.04-6.05 log CFU cm-2) than the mutant strains (2.30-5.48 log CFU cm-2). For both applications, the nanoencapsulated carvacrol demonstrated more potent antimicrobial activity against biofilms developed at pH 5.5 with 2.23 to 3.61 log reductions, compared to 1.58-2.95 log reductions at pH 6.5, with mutants being more vulnerable in acidic environments. In food substrates, nanoencapsulated carvacrol induced lower log reductions (1.58-2.90) than the ones in TSB (2.02-3.61). These findings provide valuable insights into the impact of different acidic conditions on the development of L. monocytogenes biofilms on stainless steel surfaces and the potential application of nanoencapsulated carvacrol as a biofilm control agent in food processing environments.
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Affiliation(s)
- Jina Yammine
- Univ Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, Lille, France
| | - Agapi I Doulgeraki
- Laboratory of Food Microbiology and Hygiene, Department of Food Science & Technology, Faculty of Agriculture, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
| | - Conor P O'Byrne
- Bacterial Stress Response Group, Microbiology, School of Biological & Chemical Sciences, University of Galway, Galway H91 TK33, Ireland
| | - Adem Gharsallaoui
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, LAGEPP UMR 5007, Villeurbanne, France
| | - Nour-Eddine Chihib
- Univ Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, Lille, France
| | - Layal Karam
- Human Nutrition Department, College of Health Sciences, QU Health, Qatar University, Doha, Qatar.
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Wu J, Wang C, O'Byrne C. Metabolic reprogramming in the food-borne pathogen Listeria monocytogenes as a critical defence against acid stress. FEMS Microbiol Lett 2024; 371:fnae060. [PMID: 39118365 PMCID: PMC11334721 DOI: 10.1093/femsle/fnae060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 05/29/2024] [Accepted: 08/07/2024] [Indexed: 08/10/2024] Open
Abstract
The ability to sense and respond effectively to acidic stress is important for microorganisms to survive and proliferate in fluctuating environments. As specific metabolic activities can serve to buffer the cytoplasmic pH, microorganisms rewire their metabolism to favour these reactions and thereby mitigate acid stress. The orally acquired pathogen Listeria monocytogenes exploits alternative metabolic activities to overcome the acidic stress encountered in the human stomach or food products. In this minireview, we discuss the metabolic processes in L. monocytogenes that mitigate acid stress, with an emphasis on the proton-depleting reactions, including glutamate decarboxylation, arginine/agmatine deimination, and fermentative acetoin production. We also summarize the recent findings on regulatory mechanisms that control the expression of genes that are responsible for these metabolic activities, including the general stress response regulator SigB, arginine repressor ArgR, and the recently discovered RofA-like transcriptional regulatory GadR. We further discuss the importance of this metabolic reprogramming in the context of food products and within the host. Finally, we highlight some outstanding challenges in the field, including an understanding of acid-sensing mechanisms, the role of intraspecies heterogeneity in acid resistance, and how a fundamental understanding of acid stress response can be exploited for food formulation to improve food safety and reduce food waste.
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Affiliation(s)
- Jialun Wu
- Bacterial Stress Response Group, Microbiology, Ryan Institute, School of Biological and Chemical Sciences, University of Galway, H91 TK33, Galway, Ireland
| | - Chuhan Wang
- Bacterial Stress Response Group, Microbiology, Ryan Institute, School of Biological and Chemical Sciences, University of Galway, H91 TK33, Galway, Ireland
| | - Conor O'Byrne
- Bacterial Stress Response Group, Microbiology, Ryan Institute, School of Biological and Chemical Sciences, University of Galway, H91 TK33, Galway, Ireland
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Bombelli A, Araya-Cloutier C, Boeren S, Vincken JP, Abee T, den Besten HMW. Effects of the antimicrobial glabridin on membrane integrity and stress response activation in Listeria monocytogenes. Food Res Int 2024; 175:113687. [PMID: 38128979 DOI: 10.1016/j.foodres.2023.113687] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 11/02/2023] [Accepted: 11/06/2023] [Indexed: 12/23/2023]
Abstract
Glabridin is a prenylated isoflavan which can be extracted from liquorice roots and has shown antimicrobial activity against foodborne pathogens and spoilage microorganisms. However, its application may be hindered due to limited information about its mode of action. In this study, we aimed to investigate the mode of action of glabridin using a combined phenotypic and proteomic approach on Listeria monocytogenes. Fluorescence and transmission electron microscopy of cells exposed to glabridin showed membrane permeabilization upon treatment with lethal concentrations of glabridin. Comparative proteomics analysis of control cells and cells exposed to sub-lethal concentrations of glabridin showed upregulation of proteins related to the two-component systems LiaSR and VirRS, confirming cell envelope damage during glabridin treatment. Additional upregulation of SigmaB regulon members signified activation of the general stress response in L. monocytogenes during this treatment. In line with the observed upregulation of cell envelope and general stress response proteins, sub-lethal treatment of glabridin induced (cross)protection against lethal heat and low pH stress and against antimicrobials such as nisin and glabridin itself. Overall, this study sheds light on the mode of action of glabridin and activation of the main stress responses to this antimicrobial isoflavan and highlights possible implications of its use as a naturally derived antimicrobial compound.
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Affiliation(s)
- Alberto Bombelli
- Food Microbiology, Wageningen University & Research, Wageningen, the Netherlands; Food Chemistry, Wageningen University & Research, Wageningen, the Netherlands
| | | | - Sjef Boeren
- Laboratory of Biochemistry, Wageningen University & Research, Wageningen, the Netherlands
| | - Jean-Paul Vincken
- Food Chemistry, Wageningen University & Research, Wageningen, the Netherlands
| | - Tjakko Abee
- Food Microbiology, Wageningen University & Research, Wageningen, the Netherlands
| | - Heidy M W den Besten
- Food Microbiology, Wageningen University & Research, Wageningen, the Netherlands.
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5
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Wu J, McAuliffe O, O'Byrne CP. A novel RofA-family transcriptional regulator, GadR, controls the development of acid resistance in Listeria monocytogenes. mBio 2023; 14:e0171623. [PMID: 37882515 PMCID: PMC10746197 DOI: 10.1128/mbio.01716-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 09/19/2023] [Indexed: 10/27/2023] Open
Abstract
IMPORTANCE The ability to survive the acidic conditions found in the stomach is crucial for the food-borne pathogen Listeria monocytogenes to gain access to the mammalian gastrointestinal tract. Little is currently known about how acid resistance is regulated in this pathogen and why this trait is highly variable between strains. Here, we used comparative genomics to identify a novel RofA-family transcriptional regulator, GadR, that controls the development of acid resistance. The RofA family of regulators was previously found only in a small group of bacterial pathogens, including streptococci, where they regulate virulence properties. We show that gadR encodes the dominant regulator of acid resistance in L. monocytogenes and that its sequence variability accounts for previously observed differences between strains in this trait. Together, these findings significantly advance our understanding of how this important pathogen copes with acid stress and suggest a potential molecular target to aid its control in the food chain.
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Affiliation(s)
- Jialun Wu
- Bacterial Stress Response Group, Microbiology, Ryan Institute, School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
| | - Olivia McAuliffe
- Department of Food Biosciences, Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland
- School of Biological Sciences, Queen’s University Belfast, Belfast, Northern Ireland
| | - Conor P. O'Byrne
- Bacterial Stress Response Group, Microbiology, Ryan Institute, School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
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D'Onofrio F, Schirone M, Krasteva I, Tittarelli M, Iannetti L, Pomilio F, Torresi M, Paparella A, D'Alterio N, Luciani M. A comprehensive investigation of protein expression profiles in L. monocytogenes exposed to thermal abuse, mild acid, and salt stress conditions. Front Microbiol 2023; 14:1271787. [PMID: 37876777 PMCID: PMC10591339 DOI: 10.3389/fmicb.2023.1271787] [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: 08/02/2023] [Accepted: 09/19/2023] [Indexed: 10/26/2023] Open
Abstract
Preventing L. monocytogenes infection is crucial for food safety, considering its widespread presence in the environment and its association with contaminated RTE foods. The pathogen's ability to persist under adverse conditions, for example, in food processing facilities, is linked to virulence and resistance mechanisms, including biofilm formation. In this study, the protein expression patterns of two L. monocytogenes 1/2a strains, grown under environmental stressors (mild acidic pH, thermal abuse, and high concentration of NaCl), were investigated. Protein identification and prediction were performed by nLC-ESI-MS/MS and nine different bioinformatic software programs, respectively. Gene enrichment analysis was carried out by STRING v11.05. A total of 1,215 proteins were identified, of which 335 were non-cytosolic proteins and 265 were immunogenic proteins. Proteomic analysis revealed differences in protein expression between L. monocytogenes strains in stressful conditions. The two strains exhibited unique protein expression profiles linked to stress response, virulence, and pathogenesis. Studying the proteomic profiles of such microorganisms provides information about adaptation and potential treatments, highlighting their genetic diversity and demonstrating the utility of bioinformatics and proteomics for a broader analysis of pathogens.
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Affiliation(s)
- Federica D'Onofrio
- Department of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale”, Teramo, Italy
| | - Maria Schirone
- Department of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Ivanka Krasteva
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale”, Teramo, Italy
| | - Manuela Tittarelli
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale”, Teramo, Italy
| | - Luigi Iannetti
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale”, Teramo, Italy
| | - Francesco Pomilio
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale”, Teramo, Italy
| | - Marina Torresi
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale”, Teramo, Italy
| | - Antonello Paparella
- Department of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Nicola D'Alterio
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale”, Teramo, Italy
| | - Mirella Luciani
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale”, Teramo, Italy
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Sun L, Van Loey A, Buvé C, Michiels CW. Experimental Evolution Reveals a Novel Ene Reductase That Detoxifies α,β-Unsaturated Aldehydes in Listeria monocytogenes. Microbiol Spectr 2023; 11:e0487722. [PMID: 37036358 PMCID: PMC10269891 DOI: 10.1128/spectrum.04877-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 03/17/2023] [Indexed: 04/11/2023] Open
Abstract
The plant essential oil component trans-cinnamaldehyde (t-CIN) exhibits antibacterial activity against a broad range of foodborne pathogenic bacteria, including L. monocytogenes, but its mode of action is not fully understood. In this study, several independent mutants of L. monocytogenes with increased t-CIN tolerance were obtained via experimental evolution. Whole-genome sequencing (WGS) analysis revealed single-nucleotide-variation mutations in the yhfK gene, encoding an oxidoreductase of the short-chain dehydrogenases/reductases superfamily, in each mutant. The deletion of yhfK conferred increased sensitivity to t-CIN and several other α,β-unsaturated aldehydes, including trans-2-hexenal, citral, and 4-hydroxy-2-nonenal. The t-CIN tolerance of the deletion mutant was restored via genetic complementation with yhfK. Based on a gas chromatography-mass spectrometry (GC-MS) analysis of the culture supernatants, it is proposed that YhfK is an ene reductase that converts t-CIN to 3-phenylpropanal by reducing the C=C double bond of the α,β-unsaturated aldehyde moiety. YhfK homologs are widely distributed in Bacteria, and the deletion of the corresponding homolog in Bacillus subtilis also caused increased sensitivity to t-CIN and trans-2-hexenal, suggesting that this protein may have a conserved function to protect bacteria against toxic α,β-unsaturated aldehydes in their environments. IMPORTANCE While bacterial resistance against clinically used antibiotics has been well studied, less is known about resistance against other antimicrobials, such as natural compounds that could replace traditional food preservatives. In this work, we report that the food pathogen Listeria monocytogenes can rapidly develop an elevated tolerance against t-cinnamaldehyde, a natural antimicrobial from cinnamon, by single base pair changes in the yhfK gene. The enzyme encoded by this gene is an oxidoreductase, but its substrates and precise role were hitherto unknown. We demonstrate that the enzyme reduces the double bond in t-cinnamaldehyde and thereby abolishes its antibacterial activity. Furthermore, the mutations linked to t-CIN tolerance increased bacterial sensitivity to a related compound, suggesting that they modify the substrate specificity of the enzyme. Since the family of oxidoreductases to which YhfK belongs is of great interest in the mediation of stereospecific reactions in biocatalysis, our work may also have unanticipated application potential in this field.
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Affiliation(s)
- Lei Sun
- Department of Microbial and Molecular Systems and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Ann Van Loey
- Department of Microbial and Molecular Systems and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Carolien Buvé
- Department of Microbial and Molecular Systems and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Chris W. Michiels
- Department of Microbial and Molecular Systems and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
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Wu J, McAuliffe O, O'Byrne CP. Manganese uptake mediated by the NRAMP-type transporter MntH is required for acid tolerance in Listeria monocytogenes. Int J Food Microbiol 2023; 399:110238. [PMID: 37148667 DOI: 10.1016/j.ijfoodmicro.2023.110238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 04/25/2023] [Accepted: 04/27/2023] [Indexed: 05/08/2023]
Abstract
Listeria monocytogenes is a foodborne pathogen that is characterized by its ability to withstand mild stresses (i.e. cold, acid, salt) often encountered in food products or food processing environments. In the previous phenotypic and genotypic characterization of a collection of L. monocytogenes strains, we have identified one strain 1381, originally obtained from EURL-lm, as acid sensitive (reduced survival at pH 2.3) and extremely acid intolerant (no growth at pH 4.9, which supports the growth of most strains). In this study, we investigated the cause of acid intolerance in strain 1381 by isolating and sequencing reversion mutants that were capable of growth at low pH (pH 4.8) to a similar extent as another strain (1380) from the same MLST clonal complex (CC2). Whole genome sequencing showed that a truncation in mntH, which encodes a homologue of an NRAMP (Natural Resistance-Associated Macrophage Protein) type Mn2+ transporter, is responsible for the acid intolerance phenotype observed in strain 1381. However, the mntH truncation alone was not sufficient to explain the acid sensitivity of strain 1381 at lethal pH values as strain 1381R1 (a mntH+ revertant) exhibited similar acid survival to its parental strain at pH 2.3. Further growth experiments demonstrated that Mn2+ (but not Fe2+, Zn2+, Cu2+, Ca2+, or Mg2+) supplementation fully rescues the growth of strain 1381 under low pH conditions, suggesting that a Mn2+ limitation is the likely cause of growth arrest in the mntH- background. Consistent with the important role of Mn2+ in the acid stress response was the finding that mntH and mntB (both encoding Mn2+ transporters) had higher transcription levels following exposure to mild acid stress (pH 5). Taken together, these results provide evidence that MntH-mediated Mn2+ uptake is essential for the growth of L. monocytogenes under low pH conditions. Moreover, since strain 1381 was recommended for conducting food challenge studies by the European Union Reference Laboratory, the use of this strain in evaluating the growth of L. monocytogenes in low pH environments where Mn2+ is scarce should be reconsidered. Furthermore, since it is unknown when strain 1381 acquired the mntH frameshift mutation, the ability of the strains used for challenge studies to grow under food-related stresses needs to be routinely validated.
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Affiliation(s)
- Jialun Wu
- Bacterial Stress Response Group, Microbiology, Ryan Institute, School of Biological & Chemical Sciences, University of Galway, Galway H91 TK33, Ireland
| | | | - Conor P O'Byrne
- Bacterial Stress Response Group, Microbiology, Ryan Institute, School of Biological & Chemical Sciences, University of Galway, Galway H91 TK33, Ireland..
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Sibanda T, Buys EM. Listeria monocytogenes Pathogenesis: The Role of Stress Adaptation. Microorganisms 2022; 10:microorganisms10081522. [PMID: 36013940 PMCID: PMC9416357 DOI: 10.3390/microorganisms10081522] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/08/2022] [Accepted: 07/19/2022] [Indexed: 12/13/2022] Open
Abstract
Adaptive stress tolerance responses are the driving force behind the survival ability of Listeria monocytogenes in different environmental niches, within foods, and ultimately, the ability to cause human infections. Although the bacterial stress adaptive responses are primarily a necessity for survival in foods and the environment, some aspects of the stress responses are linked to bacterial pathogenesis. Food stress-induced adaptive tolerance responses to acid and osmotic stresses can protect the pathogen against similar stresses in the gastrointestinal tract (GIT) and, thus, directly aid its virulence potential. Moreover, once in the GIT, the reprogramming of gene expression from the stress survival-related genes to virulence-related genes allows L. monocytogenes to switch from an avirulent to a virulent state. This transition is controlled by two overlapping and interlinked transcriptional networks for general stress response (regulated by Sigma factor B, (SigB)) and virulence (regulated by the positive regulatory factor A (PrfA)). This review explores the current knowledge on the molecular basis of the connection between stress tolerance responses and the pathogenesis of L. monocytogenes. The review gives a detailed background on the currently known mechanisms of pathogenesis and stress adaptation. Furthermore, the paper looks at the current literature and theories on the overlaps and connections between the regulatory networks for SigB and PrfA.
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Affiliation(s)
- Thulani Sibanda
- Department of Consumer and Food Sciences, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa;
- Department of Applied Biology and Biochemistry, National University of Science and Technology, Bulawayo P.O. Box AC939, Zimbabwe
| | - Elna M. Buys
- Department of Consumer and Food Sciences, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa;
- Correspondence:
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Wu J, NicAogáin K, McAuliffe O, Jordan K, O’Byrne C. Phylogenetic and Phenotypic Analyses of a Collection of Food and Clinical Listeria monocytogenes Isolates Reveal Loss of Function of Sigma B from Several Clonal Complexes. Appl Environ Microbiol 2022; 88:e0005122. [PMID: 35481758 PMCID: PMC9128516 DOI: 10.1128/aem.00051-22] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 03/17/2022] [Indexed: 12/14/2022] Open
Abstract
To understand the molecular mechanisms that contribute to the stress responses of the important foodborne pathogen Listeria monocytogenes, we collected 139 strains (meat, n = 25; dairy, n = 10; vegetable, n = 8; seafood, n = 14; mixed food, n = 4; and food processing environments, n = 78), mostly isolated in Ireland, and subjected them to whole-genome sequencing. These strains were compared to 25 Irish clinical isolates and 4 well-studied reference strains. Core genome and pan-genome analysis confirmed a highly clonal and deeply branched population structure. Multilocus sequence typing showed that this collection contained a diverse range of strains from L. monocytogenes lineages I and II. Several groups of isolates with highly similar genome content were traced to single or multiple food business operators, providing evidence of strain persistence or prevalence, respectively. Phenotypic screening assays for tolerance to salt stress and resistance to acid stress revealed variants within several clonal complexes that were phenotypically distinct. Five of these phenotypic outliers were found to carry mutations in the sigB operon, which encodes the stress-inducible sigma factor sigma B. Transcriptional analysis confirmed that three of the strains that carried mutations in sigB, rsbV, or rsbU had reduced SigB activity, as predicted. These strains exhibited increased tolerance to salt stress and displayed decreased resistance to low pH stress. Overall, this study shows that loss-of-function mutations in the sigB operon are comparatively common in field isolates, probably reflecting the cost of the general stress response to reproductive fitness in this pathogen. IMPORTANCE The bacterial foodborne pathogen Listeria monocytogenes frequently contaminates various categories of food products and is able to cause life-threatening infections when ingested by humans. Thus, it is important to control the growth of this bacterium in food by understanding the mechanisms that allow its proliferation under suboptimal conditions. In this study, intraspecies heterogeneity in stress response was observed across a collection consisting of mainly Irish L. monocytogenes isolates. Through comparisons of genome sequence and phenotypes observed, we identified three strains with impairment of the general stress response regulator SigB. Two of these strains are used widely in food challenge studies for evaluating the growth potential of L. monocytogenes. Given that loss of SigB function is associated with atypical phenotypic properties, the use of these strains in food challenge studies should be re-evaluated.
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Affiliation(s)
- Jialun Wu
- Bacterial Stress Response Group, Microbiology, School of Biological and Chemical Sciences, National University of Ireland, Galway, Ireland
| | - Kerrie NicAogáin
- Bacterial Stress Response Group, Microbiology, School of Biological and Chemical Sciences, National University of Ireland, Galway, Ireland
| | | | - Kieran Jordan
- Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland
| | - Conor O’Byrne
- Bacterial Stress Response Group, Microbiology, School of Biological and Chemical Sciences, National University of Ireland, Galway, Ireland
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Guerreiro DN, Pucciarelli MG, Tiensuu T, Gudynaite D, Boyd A, Johansson J, García-del Portillo F, O’Byrne CP. Acid stress signals are integrated into the σB-dependent general stress response pathway via the stressosome in the food-borne pathogen Listeria monocytogenes. PLoS Pathog 2022; 18:e1010213. [PMID: 35275969 PMCID: PMC8942246 DOI: 10.1371/journal.ppat.1010213] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/23/2022] [Accepted: 02/28/2022] [Indexed: 12/17/2022] Open
Abstract
The general stress response (GSR) in Listeria monocytogenes plays a critical role in the survival of this pathogen in the host gastrointestinal tract. The GSR is regulated by the alternative sigma factor B (σB), whose role in protection against acid stress is well established. Here, we investigated the involvement of the stressosome, a sensory hub, in transducing low pH signals to induce the GSR. Mild acid shock (15 min at pH 5.0) activated σB and conferred protection against a subsequent lethal pH challenge. A mutant strain where the stressosome subunit RsbR1 was solely present retained the ability to induce σB activity at pH 5.0. The role of stressosome phosphorylation in signal transduction was investigated by mutating the putative phosphorylation sites in the core stressosome proteins RsbR1 (rsbR1-T175A, -T209A, -T241A) and RsbS (rsbS-S56A), or the stressosome kinase RsbT (rsbT-N49A). The rsbS S56A and rsbT N49A mutations abolished the response to low pH. The rsbR1-T209A and rsbR1-T241A mutants displayed constitutive σB activity. Mild acid shock upregulates invasion genes inlAB and stimulates epithelial cell invasion, effects that were abolished in mutants with an inactive or overactive stressosome. Overall, the results show that the stressosome is required for acid-induced activation of σB in L. monocytogenes. Furthermore, they show that RsbR1 can function independently of its paralogues and signal transduction requires RsbT-mediated phosphorylation of RsbS on S56 and RsbR1 on T209 but not T175. These insights shed light on the mechanisms of signal transduction that activate the GSR in L. monocytogenes in response to acidic environments, and highlight the role this sensory process in the early stages of the infectious cycle. The stress sensing hub known as the stressosome, found in many bacterial and archaeal lineages, plays a crucial role in both stress tolerance and virulence in the food-borne pathogen Listeria monocytogenes. However, the mechanisms that lead to its activation and the subsequent activation of the general stress response have remained elusive. In this study, we examined the signal transduction mechanisms that operate in the stressosome in response to acid stress. We found that only one of the five putative sensory proteins present in L. monocytogenes, RsbR1, was required for effective transduction of acid tress signals. We further found that phosphorylation of RsbS and RsbR1, mediated by the RsbT kinase, is essential for signal transduction. Failure to phosphorylate RsbS on Serine 56 completely abolished acid sensing by the stressosome, which prevented the development of adaptive acid tolerance. The acid-induced activation of internalin gene expression was also abolished in mutants with defective stressosome signalling, suggesting a role for the stressosome in the invasion of host cells. Together the data provide new insights into the mechanisms that activate the stressosome in response to acid stress and highlight the role this sensory hub plays in virulence.
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Affiliation(s)
- Duarte N. Guerreiro
- Bacterial Stress Response Group, Microbiology, School of Biological and Chemical Sciences, National University of Ireland, Galway, Ireland
| | - M. Graciela Pucciarelli
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB)-CSIC, Madrid, Spain
- Department of Molecular Biology, Universidad Autónoma de Madrid, Centre of Molecular Biology ‘Severo Ochoa’ (CBMSO CSIC-UAM), Madrid, Spain
| | - Teresa Tiensuu
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre of Microbial Research, Umeå, Sweden
| | - Diana Gudynaite
- Bacterial Stress Response Group, Microbiology, School of Biological and Chemical Sciences, National University of Ireland, Galway, Ireland
| | - Aoife Boyd
- Pathogenic Mechanisms Research Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Jörgen Johansson
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre of Microbial Research, Umeå, Sweden
| | | | - Conor P. O’Byrne
- Bacterial Stress Response Group, Microbiology, School of Biological and Chemical Sciences, National University of Ireland, Galway, Ireland
- * E-mail:
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12
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Abram F, Arcari T, Guerreiro D, O'Byrne CP. Evolutionary trade-offs between growth and survival: The delicate balance between reproductive success and longevity in bacteria. Adv Microb Physiol 2021; 79:133-162. [PMID: 34836610 DOI: 10.1016/bs.ampbs.2021.07.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
All living cells strive to allocate cellular resources in a way that promotes maximal evolutionary fitness. While there are many competing demands for resources the main decision making process centres on whether to proceed with growth and reproduction or to "hunker down" and invest in protection and survival (or to strike an optimal balance between these two processes). The transcriptional programme active at any given time largely determines which of these competing processes is dominant. At the top of the regulatory hierarchy are the sigma factors that commandeer the transcriptional machinery and determine which set of promoters are active at any given time. The regulatory inputs controlling their activity are therefore often highly complex, with multiple layers of regulation, allowing relevant environmental information to produce the most beneficial response. The tension between growth and survival is also evident in the developmental programme necessary to promote biofilm formation, which is typically associated with low growth rates and enhanced long-term survival. Nucleotide second messengers and energy pools (ATP/ADP levels) play critical roles in determining the fate of individual cells. Regulatory small RNAs frequently play important roles in the decision making processes too. In this review we discuss the trade-off that exists between reproduction and persistence in bacteria and discuss some of the recent advances in this fascinating field.
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Affiliation(s)
- Florence Abram
- Microbiology & Ryan Institute, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Talia Arcari
- Microbiology & Ryan Institute, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Duarte Guerreiro
- Microbiology & Ryan Institute, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Conor P O'Byrne
- Microbiology & Ryan Institute, School of Natural Sciences, National University of Ireland, Galway, Ireland.
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13
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Listeria monocytogenes requires the RsbX protein to prevent SigB-activation under non-stressed conditions. J Bacteriol 2021; 204:e0048621. [PMID: 34694900 PMCID: PMC8765406 DOI: 10.1128/jb.00486-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The survival of microbial cells under changing environmental conditions requires an efficient reprogramming of transcription, often mediated by alternative sigma factors. The Gram-positive human pathogen Listeria monocytogenes senses and responds to environmental stress mainly through the alternative sigma factor σB (SigB), which controls expression of the general stress response regulon. SigB activation is achieved through a complex series of phosphorylation/dephosphorylation events culminating in the release of SigB from its anti-sigma factor RsbW. At the top of the signal transduction pathway lies a large multiprotein complex known as the stressosome that is believed to act as a sensory hub for stresses. Following signal detection, stressosome proteins become phosphorylated. Resetting of the stressosome is hypothesized to be exerted by a putative phosphatase, RsbX, which presumably removes phosphate groups from stressosome proteins poststress. We addressed the role of the RsbX protein in modulating the activity of the stressosome and consequently regulating SigB activity in L. monocytogenes. We show that RsbX is required to reduce SigB activation levels under nonstress conditions and that it is required for appropriate SigB-mediated stress adaptation. A strain lacking RsbX displayed impaired motility and biofilm formation and also an increased survival at low pH. Our results could suggest that absence of RsbX alters the multiprotein composition of the stressosome without dramatically affecting its phosphorylation status. Overall, the data show that RsbX plays a critical role in modulating the signal transduction pathway by blocking SigB activation under nonstressed conditions. IMPORTANCE Pathogenic bacteria need to sense and respond to stresses to survive harsh environments and also to turn off the response when no longer facing stress. Activity of the stress sigma factor SigB in the human pathogen Listeria monocytogenes is controlled by a hierarchic system having a large stress-sensing multiprotein complex known as the stressosome at the top. Following stress exposure, proteins in the stressosome become phosphorylated, leading to SigB activation. We have studied the role of a putative phosphatase, RsbX, which is hypothesized to dephosphorylate stressosome proteins. RsbX is critical not only to switch off the stress response poststress but also to keep the activity of SigB low at nonstressed conditions to prevent unnecessary gene expression and save energy.
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14
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Characterization of the roles of activated charcoal and Chelex in the induction of PrfA regulon expression in complex medium. PLoS One 2021; 16:e0250989. [PMID: 33914817 PMCID: PMC8084165 DOI: 10.1371/journal.pone.0250989] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 04/16/2021] [Indexed: 11/21/2022] Open
Abstract
The foodborne pathogen Listeria monocytogenes is able to survive across a wide range of intra- and extra-host environments by appropriately modulating gene expression patterns in response to different stimuli. Positive Regulatory Factor A (PrfA) is the major transcriptional regulator of virulence gene expression in L. monocytogenes. It has long been known that activated charcoal is required to induce the expression of PrfA-regulated genes in complex media, such as Brain Heart Infusion (BHI), but not in chemically defined media. In this study, we show that the expression of the PrfA-regulated hly, which encodes listeriolysin O, is induced 5- and 8-fold in L. monocytogenes cells grown in Chelex-treated BHI (Ch-BHI) and in the presence of activated charcoal (AC-BHI), respectively, relative to cells grown in BHI medium. Specifically, we show that metal ions present in BHI broth plays a role in the reduced expression of the PrfA regulon. In addition, we show that expression of hly is induced when the levels of bioavailable extra- or intercellular iron are reduced. L. monocytogenes cells grown Ch-BHI and AC-BHI media showed similar levels of resistance to the iron-activated antibiotic, streptonigrin, indicating that activated charcoal reduces the intracellular labile iron pool. Metal depletion and exogenously added glutathione contributed synergistically to PrfA-regulated gene expression since glutathione further increased hly expression in metal-depleted BHI but not in BHI medium. Analyses of transcriptional reporter fusion expression patterns revealed that genes in the PrfA regulon are differentially expressed in response to metal depletion, metal excess and exogenous glutathione. Our results suggest that metal ion abundance plays a role in modulating expression of PrfA-regulated virulence genes in L. monocytogenes.
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15
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Alternative σ Factors Regulate Overlapping as Well as Distinct Stress Response and Metabolic Functions in Listeria monocytogenes under Stationary Phase Stress Condition. Pathogens 2021; 10:pathogens10040411. [PMID: 33915780 PMCID: PMC8066629 DOI: 10.3390/pathogens10040411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/23/2021] [Accepted: 03/26/2021] [Indexed: 12/13/2022] Open
Abstract
Listeria monocytogenes can regulate and fine-tune gene expression, to adapt to diverse stress conditions encountered during foodborne transmission. To further understand the contributions of alternative sigma (σ) factors to the regulation of L. monocytogenes gene expression, RNA-Seq was performed on L. monocytogenes strain 10403S and five isogenic mutants (four strains bearing in-frame null mutations in three out of four alternative σ factor genes, ΔCHL, ΔBHL, ΔBCL, and ΔBCH, and one strain bearing null mutations in all four genes, ΔBCHL), grown to stationary phase. Our data showed that 184, 35, 34, and 20 genes were positively regulated by σB, σL, σH, and σC (posterior probability > 0.9 and Fold Change (FC) > 5.0), respectively. Moreover, σB-dependent genes showed the highest FC (based on comparisons between the ΔCHL and the ΔBCHL strain), with 44 genes showing an FC > 100; only four σL-dependent, and no σH- or σC-dependent genes showed FC >100. While σB-regulated genes identified in this study are involved in stress-associated functions and metabolic pathways, σL appears to largely regulate genes involved in a few specific metabolic pathways, including positive regulation of operons encoding phosphoenolpyruvate (PEP)-dependent phosphotransferase systems (PTSs). Overall, our data show that (i) σB and σL directly and indirectly regulate genes involved in several energy metabolism-related functions; (ii) alternative σ factors are involved in complex regulatory networks and appear to have epistatic effects in stationary phase cells; and (iii) σB regulates multiple stress response pathways, while σL and σH positively regulate a smaller number of specific pathways.
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16
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Tran BM, Prabha H, Iyer A, O'Byrne C, Abee T, Poolman B. Measurement of Protein Mobility in Listeria monocytogenes Reveals a Unique Tolerance to Osmotic Stress and Temperature Dependence of Diffusion. Front Microbiol 2021; 12:640149. [PMID: 33679676 PMCID: PMC7925416 DOI: 10.3389/fmicb.2021.640149] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 01/21/2021] [Indexed: 11/18/2022] Open
Abstract
Protein mobility in the cytoplasm is essential for cellular functions, and slow diffusion may limit the rates of biochemical reactions in the living cell. Here, we determined the apparent lateral diffusion coefficient (DL) of GFP in Listeria monocytogenes as a function of osmotic stress, temperature, and media composition. We find that DL is much less affected by hyperosmotic stress in L. monocytogenes than under similar conditions in Lactococcus lactis and Escherichia coli. We find a temperature optimum for protein diffusion in L. monocytogenes at 30°C, which deviates from predicted trends from the generalized Stokes-Einstein equation under dilute conditions and suggests that the structure of the cytoplasm and macromolecular crowding vary as a function of temperature. The turgor pressure of L. monocytogenes is comparable to other Gram-positive bacteria like Bacillus subtilis and L. lactis but higher in a knockout strain lacking the stress-inducible sigma factor SigB. We discuss these findings in the context of how L. monocytogenes survives during environmental transmission and interaction with the human host.
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Affiliation(s)
- Buu Minh Tran
- Department of Biochemistry, University of Groningen, Groningen, Netherlands
| | - Haritha Prabha
- Department of Biochemistry, University of Groningen, Groningen, Netherlands
| | - Aditya Iyer
- Department of Biochemistry, University of Groningen, Groningen, Netherlands
| | - Conor O'Byrne
- School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Tjakko Abee
- Laboratory of Food Microbiology, Wageningen University Research, Wageningen, Netherlands
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Groningen, Netherlands
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17
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Mattila M, Somervuo P, Korkeala H, Stephan R, Tasara T. Transcriptomic and Phenotypic Analyses of the Sigma B-Dependent Characteristics and the Synergism between Sigma B and Sigma L in Listeria monocytogenes EGD-e. Microorganisms 2020; 8:microorganisms8111644. [PMID: 33114171 PMCID: PMC7690807 DOI: 10.3390/microorganisms8111644] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 12/19/2022] Open
Abstract
Numerous gene expression and stress adaptation responses in L. monocytogenes are regulated through alternative sigma factors σB and σL. Stress response phenotypes and transcriptomes were compared between L. monocytogenes EGD-e and its ΔsigB and ΔsigBL mutants. Targeted growth phenotypic analysis revealed that the ΔsigB and ΔsigBL mutants are impaired during growth under cold and organic-acid stress conditions. Phenotypic microarrays revealed increased sensitivity in both mutants to various antimicrobial compounds. Genes de-regulated in these two mutants were identified by genome-wide transcriptome analysis during exponential growth in BHI. The ΔsigB and ΔsigBL strains repressed 198 and 254 genes, respectively, compared to the parent EGD-e strain at 3 °C, whereas 86 and 139 genes, respectively, were repressed in these mutants during growth at 37 °C. Genes repressed in these mutants are involved in various cellular functions including transcription regulation, energy metabolism and nutrient transport functions, and viral-associated processes. Exposure to cold stress induced a significant increase in σB and σL co-dependent genes of L. monocytogenes EGD-e since most (62%) of the down-regulated genes uncovered at 3 °C were detected in the ΔsigBL double-deletion mutant but not in ΔsigB or ΔsigL single-deletion mutants. Overall, the current study provides an expanded insight into σB and σL phenotypic roles and functional interactions in L. monocytogenes. Besides previously known σB- and σL-dependent genes, the transcriptomes defined in ΔsigB and ΔsigBL mutants reveal several new genes that are positively regulated by σB alone, as well as those co-regulated through σB- and σL-dependent mechanisms during L. monocytogenes growth under optimal and cold-stress temperature conditions.
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Affiliation(s)
- Mirjami Mattila
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki, Finland; (M.M.); (P.S.); (H.K.)
| | - Panu Somervuo
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki, Finland; (M.M.); (P.S.); (H.K.)
| | - Hannu Korkeala
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki, Finland; (M.M.); (P.S.); (H.K.)
| | - Roger Stephan
- Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Winterthurerstr. 272, CH-8057 Zurich, Switzerland;
| | - Taurai Tasara
- Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Winterthurerstr. 272, CH-8057 Zurich, Switzerland;
- Correspondence: ; Tel.: +41-44-635-8669
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18
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Guerreiro DN, Arcari T, O'Byrne CP. The σ B-Mediated General Stress Response of Listeria monocytogenes: Life and Death Decision Making in a Pathogen. Front Microbiol 2020; 11:1505. [PMID: 32733414 PMCID: PMC7358398 DOI: 10.3389/fmicb.2020.01505] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 06/10/2020] [Indexed: 12/17/2022] Open
Abstract
Sensing and responding to environmental cues is critical for the adaptability and success of the food-borne bacterial pathogen Listeria monocytogenes. A supramolecular multi-protein complex known as the stressosome, which acts as a stress sensing hub, is responsible for orchestrating the activation of a signal transduction pathway resulting in the activation of σB, the sigma factor that controls the general stress response (GSR). When σB is released from the anti-sigma factor RsbW, a rapid up-regulation of the large σB regulon, comprised of ≥ 300 genes, ensures that cells respond appropriately to the new environmental conditions. A diversity of stresses including low pH, high osmolarity, and blue light are known to be sensed by the stressosome, resulting in a generalized increase in stress resistance. Appropriate activation of the stressosome and deployment of σB are critical to fitness as there is a trade-off between growth and stress protection when the GSR is deployed. We review the recent developments in this field and describe an up-to-date model of how this sensory organelle might integrate environmental signals to produce an appropriate activation of the GSR. Some of the outstanding questions and challenges in this fascinating field are also discussed.
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Affiliation(s)
- Duarte N Guerreiro
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Talia Arcari
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Conor P O'Byrne
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
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19
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Guerreiro DN, Wu J, Dessaux C, Oliveira AH, Tiensuu T, Gudynaite D, Marinho CM, Boyd A, García-Del Portillo F, Johansson J, O'Byrne CP. Mild Stress Conditions during Laboratory Culture Promote the Proliferation of Mutations That Negatively Affect Sigma B Activity in Listeria monocytogenes. J Bacteriol 2020; 202:e00751-19. [PMID: 32094160 PMCID: PMC7148139 DOI: 10.1128/jb.00751-19] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 02/01/2020] [Indexed: 12/18/2022] Open
Abstract
In Listeria monocytogenes, the full details of how stress signals are integrated into the σB regulatory pathway are not yet available. To help shed light on this question, we investigated a collection of transposon mutants that were predicted to have compromised activity of the alternative sigma factor B (σB). These mutants were tested for acid tolerance, a trait that is known to be under σB regulation, and they were found to display increased acid sensitivity, similar to a mutant lacking σB (ΔsigB). The transposon insertions were confirmed by whole-genome sequencing, but in each case, the strains were also found to carry a frameshift mutation in the sigB operon. The changes were predicted to result in premature stop codons, with negative consequences for σB activation, independently of the transposon location. Reduced σB activation in these mutants was confirmed. Growth measurements under conditions similar to those used during the construction of the transposon library revealed that the frameshifted sigB operon alleles conferred a growth advantage at higher temperatures, during late exponential phase. Mixed-culture experiments at 42°C demonstrated that the loss of σB activity allowed mutants to take over a population of parental bacteria. Together, our results suggest that mutations affecting σB activity can arise during laboratory culture because of the growth advantage conferred by these mutations under mild stress conditions. The data highlight the significant cost of stress protection in this foodborne pathogen and emphasize the need for whole-genome sequence analysis of newly constructed strains to confirm the expected genotype.IMPORTANCE In the present study, we investigated a collection of Listeria monocytogenes strains that all carried sigB operon mutations. The mutants all had reduced σB activity and were found to have a growth advantage under conditions of mild heat stress (42°C). In mixed cultures, these mutants outcompeted the wild type when mild heat stress was present but not at an optimal growth temperature. An analysis of 22,340 published L. monocytogenes genome sequences found a high rate of premature stop codons present in genes positively regulating σB activity. Together, these findings suggest that the occurrence of mutations that attenuate σB activity can be favored under conditions of mild stress, probably highlighting the burden on cellular resources that stems from deploying the general stress response.
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Affiliation(s)
- Duarte N Guerreiro
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Jialun Wu
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Charlotte Dessaux
- Laboratory of Intracellular Bacterial Pathogens, National Center for Biotechnology (CNB)-CSIC, Madrid, Spain
| | - Ana H Oliveira
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Center of Microbial Research, Umeå, Sweden
| | - Teresa Tiensuu
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Center of Microbial Research, Umeå, Sweden
| | - Diana Gudynaite
- Molecular Microbiology Department, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Catarina M Marinho
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland
- Université Bourgogne Franche-Conté, Dijon, France
- Institut National de la Recherche Agronomique, UMR Agroécologie, Dijon, France
| | - Aoife Boyd
- Pathogenic Mechanisms Research Group, National University of Ireland, Galway, Ireland
| | | | - Jörgen Johansson
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Center of Microbial Research, Umeå, Sweden
| | - Conor P O'Byrne
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland
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20
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Shao X, Fang K, Medina D, Wan J, Lee J, Hong SH. The probiotic,
Leuconostoc mesenteroides
, inhibits
Listeria monocytogenes
biofilm formation. J Food Saf 2020. [DOI: 10.1111/jfs.12750] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Xinhao Shao
- Department of Chemical and Biological EngineeringIllinois Institute of Technology Chicago Illinois
| | - Kuili Fang
- Department of Chemical and Biological EngineeringIllinois Institute of Technology Chicago Illinois
| | - Daniel Medina
- Department of Biomedical EngineeringIllinois Institute of Technology Chicago Illinois
| | - Jason Wan
- Institute for Food Safety and HealthIllinois Institute of Technology Bedford Park Illinois
| | - Jung‐Lim Lee
- Department of Human Ecology, Food Science and Biotechnology Program, Food Microbiology LaboratoryDelaware State University Dover Delaware
| | - Seok Hoon Hong
- Department of Chemical and Biological EngineeringIllinois Institute of Technology Chicago Illinois
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21
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Cortes BW, Naditz AL, Anast JM, Schmitz-Esser S. Transcriptome Sequencing of Listeria monocytogenes Reveals Major Gene Expression Changes in Response to Lactic Acid Stress Exposure but a Less Pronounced Response to Oxidative Stress. Front Microbiol 2020; 10:3110. [PMID: 32038553 PMCID: PMC6985202 DOI: 10.3389/fmicb.2019.03110] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 12/23/2019] [Indexed: 12/15/2022] Open
Abstract
Listeria monocytogenes is a well-characterized pathogen that represents a major threat to food safety. In this study, we examine the chromosomal and plasmid transcriptomes of two different L. monocytogenes strains, 6179 [belonging to sequence type (ST) 121] and R479a (ST8), in response to 30 min exposure to oxidative (0.01% hydrogen peroxide) and acid (1% lactic acid, pH 3.4) stress. The exposure to oxidative stress resulted in 102 and 9 differentially expressed (DE) genes in the chromosomal transcriptomes of 6179 and R479a, respectively. In contrast, 2280 and 2151 DE genes were observed in the respective chromosomal transcriptomes of 6179 and R479a in response to lactic acid stress. During lactic acid stress, we observed upregulation of numerous genes known to be involved in the L. monocytogenes stress response, including multiple members of the σB regulon, many of which have not been functionally characterized. Among these genes, homologs of lmo2230 were highly upregulated in both strains. Most notably, the σB-dependent non-coding RNA Rli47 was by far the most highly expressed gene in both 6179 and R479a, accounting for an average of 28 and 38% of all mapped reads in the respective chromosomal transcriptomes. In response to oxidative stress, one DE gene was identified in the 6179 plasmid transcriptome, and no DE genes were observed in the transcriptome of the R479a plasmid. However, lactic acid exposure resulted in upregulation of the stress response gene clpL, among others, on the 6179 plasmid. In R479a, a number of uncharacterized plasmid genes were upregulated, indicating a potential role in stress response. Furthermore, an average of 65% of all mapped transcriptome reads for the R479a plasmid following acid stress were mapped to an intergenic region bearing similarity to riboswitches involved in transition metal resistance. The results of this study support the conclusion that members of the σB regulon, particularly lmo2230 and the non-coding RNA Rli47, play an integral role in the response of L. monocytogenes to acid stress. Furthermore, we report the first global transcriptome sequencing analysis of L. monocytogenes plasmid gene expression and identify a putative, plasmid-encoded riboswitch with potential involvement in response to acid exposure.
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Affiliation(s)
- Bienvenido W Cortes
- Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA, United States.,Department of Animal Science, Iowa State University, Ames, IA, United States
| | - Annabel L Naditz
- Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA, United States.,Department of Animal Science, Iowa State University, Ames, IA, United States
| | - Justin M Anast
- Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA, United States.,Department of Animal Science, Iowa State University, Ames, IA, United States
| | - Stephan Schmitz-Esser
- Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, IA, United States.,Department of Animal Science, Iowa State University, Ames, IA, United States
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Horlbog JA, Stevens MJA, Stephan R, Guldimann C. Global Transcriptional Response of Three Highly Acid-Tolerant Field Strains of Listeria monocytogenes to HCl Stress. Microorganisms 2019; 7:microorganisms7100455. [PMID: 31623206 PMCID: PMC6843411 DOI: 10.3390/microorganisms7100455] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 10/08/2019] [Accepted: 10/10/2019] [Indexed: 12/15/2022] Open
Abstract
Tolerance to acid is of dual importance for the food-borne pathogen Listeria monocytogenes: acids are used as a preservative, and gastric acid is one of the first defenses within the host. There are considerable differences in the acid tolerance of strains. Here we present the transcriptomic response of acid-tolerant field strains of L. monocytogenes to HCl at pH 3.0. RNAseq revealed significant differential expression of genes involved in phosphotransferase systems, oxidative phosphorylation, cell morphology, motility, and biofilm formation. Genes in the acetoin biosynthesis pathway were upregulated, suggesting that L. monocytogenes shifts to metabolizing pyruvate to acetoin under organic acid stress. We also identified the formation of cell aggregates in microcolonies as a potential relief strategy. A motif search within the first 150 bp upstream of differentially expressed genes identified a novel potential regulatory sequence that may have a function in the regulation of virulence gene expression. Our data support a model where an excess of intracellular H+ ions is counteracted by pumping H+ out of the cytosol via cytochrome C under reduced activity of the ATP synthase. The observed morphological changes suggest that acid stress may cause cells to aggregate in biofilm microcolonies to create a more favorable microenvironment. Additionally, HCl stress in the host stomach may serve as (i) a signal to downregulate highly immunogenic flagella, and (ii) as an indicator for the imminent contact with host cells which triggers early stage virulence genes.
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Affiliation(s)
- Jule Anna Horlbog
- Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, 8006 Zürich, Switzerland.
| | - Marc J A Stevens
- Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, 8006 Zürich, Switzerland.
| | - Roger Stephan
- Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, 8006 Zürich, Switzerland.
| | - Claudia Guldimann
- Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, 8006 Zürich, Switzerland.
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Sheet S, Yesupatham S, Ghosh K, Choi MS, Shim KS, Lee YS. Modulatory effect of low-shear modeled microgravity on stress resistance, membrane lipid composition, virulence, and relevant gene expression in the food-borne pathogen Listeria monocytogenes. Enzyme Microb Technol 2019; 133:109440. [PMID: 31874690 DOI: 10.1016/j.enzmictec.2019.109440] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 09/27/2019] [Accepted: 10/04/2019] [Indexed: 12/17/2022]
Abstract
The present study investigated the influence of low-shear modeled microgravity (LSMMG) conditions on Listeria monocytogenes stress response (heat, cold, and acid), membrane fatty acid composition, and virulence potential as well as stress-/virulence-associated gene expression. The results showed that LSMMG-cultivated cells had lower survival rate and lower D-values under heat and acid stress conditions compared to cells grown under normal gravity (NG). Interestingly, the cold resistance was elevated in cells cultivated under LSMMG conditions when compared to NG conditions. A higher amount of anteiso-branched chain fatty acids and lower ratio of iso/anteiso were observed in LSMMG cultured cells, which would contribute to increased membrane fluidity. Under LSMMG conditions, upregulated expression of cold stress-related genes (cspA, cspB, and cspD) was noticed but no change in expression was observed for heat (dnaK, groES, clpC, clpP, and clpE) and acid stress-related genes (sigB). The LSMMG-grown cells showed inferior virulence capacity in terms of infection, cell cycle arrest, and apoptosis induction in Caco-2 cells compared to those grown under NG conditions. Approximately 3.65, 2.13, 4.02, and 2.65-fold downregulation of prfA, hly, inlA, and bsh genes, respectively, in LSMMG-cultured cells might be the reason for reduced virulence. In conclusion, these findings suggest that growth under LSMMG conditions stimulates alterations in L. monocytogenes stress/virulence response, perhaps due to changes in lipid composition and related genes expression.
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Affiliation(s)
- Sunirmal Sheet
- Department of Forest Science and Technology, College of Agriculture and Life Sciences,Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do, Republic of Korea
| | - Sathishkumar Yesupatham
- Department of Forest Science and Technology, College of Agriculture and Life Sciences,Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do, Republic of Korea; Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daehak-Ro, Daejeon, Republic of Korea
| | - Kuntal Ghosh
- Department of Biological Sciences, Midnapore City College, Kuturiya, P.O. Bhadutala, Pin-721129, Paschim Medinipur, West Bengal, India
| | - Mi-Sook Choi
- Department of Forest Science and Technology, College of Agriculture and Life Sciences,Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do, Republic of Korea
| | - Kwan Seob Shim
- Department of Animal Biotechnology, College of Agriculture and Life Sciences, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do, Republic of Korea
| | - Yang Soo Lee
- Department of Forest Science and Technology, College of Agriculture and Life Sciences,Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do, Republic of Korea.
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24
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Marinho CM, Dos Santos PT, Kallipolitis BH, Johansson J, Ignatov D, Guerreiro DN, Piveteau P, O’Byrne CP. The σ B-dependent regulatory sRNA Rli47 represses isoleucine biosynthesis in Listeria monocytogenes through a direct interaction with the ilvA transcript. RNA Biol 2019; 16:1424-1437. [PMID: 31242083 PMCID: PMC6779388 DOI: 10.1080/15476286.2019.1632776] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 06/06/2019] [Accepted: 06/11/2019] [Indexed: 12/25/2022] Open
Abstract
The facultative intracellular pathogen Listeria monocytogenes can persist and grow in a diverse range of environmental conditions, both outside and within its mammalian host. The alternative sigma factor Sigma B (σB) plays an important role in this adaptability and is critical for the transition into the host. While some of the functions of the σB regulon in facilitating this transition are understood the role of σB-dependent small regulatory RNAs (sRNAs) remain poorly characterized. In this study, we focused on elucidating the function of Rli47, a σB-dependent sRNA that is highly induced in the intestine and in macrophages. Using a combination of in silico and in vivo approaches, a binding interaction was predicted with the Shine-Dalgarno region of the ilvA mRNA, which encodes threonine deaminase, an enzyme required for branched-chain amino acid biosynthesis. Both ilvA transcript levels and threonine deaminase activity were increased in a deletion mutant lacking the rli47 gene. The Δrli47 mutant displayed a shorter growth lag in isoleucine-depleted growth media relative to the wild-type, and a similar phenotype was also observed in a mutant lacking σB. The impact of the Δrli47 on the global transcription profile of the cell was investigated using RNA-seq, and a significant role for Rli47 in modulating amino acid metabolism was uncovered. Taken together, the data point to a model where Rli47 is responsible for specifically repressing isoleucine biosynthesis as a way to restrict growth under harsh conditions, potentially contributing to the survival of L. monocytogenes in niches both outside and within the mammalian host.
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Affiliation(s)
- Catarina M. Marinho
- Agroécologie, AgroSup Dijon, INRA, Université de Bourgogne Franche-Comté, Dijon, France
- Bacterial Stress Response Group, National University of Ireland, Galway, Ireland
| | - Patrícia T. Dos Santos
- 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
| | - Jörgen Johansson
- Department of Molecular Biology; Molecular Infection Medicine, Sweden (MIMS), Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Dmitriy Ignatov
- Department of Molecular Biology; Molecular Infection Medicine, Sweden (MIMS), Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Duarte N. Guerreiro
- Bacterial Stress Response Group, National University of Ireland, Galway, Ireland
| | - Pascal Piveteau
- Agroécologie, AgroSup Dijon, INRA, Université de Bourgogne Franche-Comté, Dijon, France
| | - Conor P. O’Byrne
- Bacterial Stress Response Group, National University of Ireland, Galway, Ireland
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25
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Cross Talk between SigB and PrfA in Listeria monocytogenes Facilitates Transitions between Extra- and Intracellular Environments. Microbiol Mol Biol Rev 2019; 83:83/4/e00034-19. [PMID: 31484692 DOI: 10.1128/mmbr.00034-19] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The foodborne pathogen Listeria monocytogenes can modulate its transcriptome and proteome to ensure its survival during transmission through vastly differing environmental conditions. While L. monocytogenes utilizes a large array of regulators to achieve survival and growth in different intra- and extrahost environments, the alternative sigma factor σB and the transcriptional activator of virulence genes protein PrfA are two key transcriptional regulators essential for responding to environmental stress conditions and for host infection. Importantly, emerging evidence suggests that the shift from extrahost environments to the host gastrointestinal tract and, subsequently, to intracellular environments requires regulatory interplay between σB and PrfA at transcriptional, posttranscriptional, and protein activity levels. Here, we review the current evidence for cross talk and interplay between σB and PrfA and their respective regulons and highlight the plasticity of σB and PrfA cross talk and the role of this cross talk in facilitating successful transition of L. monocytogenes from diverse extrahost to diverse extra- and intracellular host environments.
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26
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Tiensuu T, Guerreiro DN, Oliveira AH, O’Byrne C, Johansson J. Flick of a switch: regulatory mechanisms allowing Listeria monocytogenes to transition from a saprophyte to a killer. Microbiology (Reading) 2019; 165:819-833. [DOI: 10.1099/mic.0.000808] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Teresa Tiensuu
- Department of Molecular Biology; Molecular Infection Medicine, Sweden (MIMS); Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Duarte N. Guerreiro
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland Galway, Galway H91 TK33, Ireland
| | - Ana H. Oliveira
- Department of Molecular Biology; Molecular Infection Medicine, Sweden (MIMS); Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Conor O’Byrne
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland Galway, Galway H91 TK33, Ireland
| | - Jörgen Johansson
- Department of Molecular Biology; Molecular Infection Medicine, Sweden (MIMS); Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
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27
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Hingston PA, Truelstrup Hansen L, Pombert JF, Wang S. Characterization of Listeria monocytogenes enhanced cold-tolerance variants isolated during prolonged cold storage. Int J Food Microbiol 2019; 306:108262. [PMID: 31362162 DOI: 10.1016/j.ijfoodmicro.2019.108262] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 05/04/2019] [Accepted: 07/07/2019] [Indexed: 11/25/2022]
Abstract
In this study, we show that growth and prolonged storage of Listeria monocytogenes at 4 °C can promote the selection of variants with enhanced cold and heat tolerance. Enhanced cold-tolerance (ECT) variants (n = 12) were successfully isolated from a strain with impaired cold growth abilities following 84 days of storage at 4 °C in brain heart infusion broth (BHIB). Whole genome sequencing, membrane fatty acid analysis, and stress tolerance profiling were performed on the parent strain and two ECT variants: one displaying regular-sized colonies and the other displaying small colonies when grown at 37 °C on BHI agar. Under cold stress conditions, the parent strain exhibited an impaired ability to produce branched-chain fatty acids which are known to be important for cold adaptation in L.monocytogenes. The ECT variants were able to overcome this limitation, a finding which is hypothesized to be associated with the identification of two independent single-nucleotide polymorphisms in genes encoding subunits of acetyl-coA carboxylase, an enzyme critical for fatty acid biosynthesis. While the ECT phenotype was not found to be associated with improved salt (BHIB + 6% NaCl, 25 °C), acid (BHIB pH 5, 25 °C) or desiccation (33% RH, 20 °C) tolerance, the small-colony variant exhibited significantly (p < 0.05) enhanced heat tolerance at 52 °C in buffered peptone water compared to the parent strain and the other variant. The results from this study demonstrate that the continuous use of refrigeration along the food-supply chain has the potential to select for L.monocytogenes variants with enhanced cold and heat tolerance, highlighting the impact that microbial intervention strategies can have on the evolution of bacterial strains and likewise, food safety.
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Affiliation(s)
- Patricia A Hingston
- Food, Nutrition and Health, The University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | - Siyun Wang
- Food, Nutrition and Health, The University of British Columbia, Vancouver, British Columbia, Canada.
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28
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Liu Y, Orsi RH, Gaballa A, Wiedmann M, Boor KJ, Guariglia-Oropeza V. Systematic review of the Listeria monocytogenes σB regulon supports a role in stress response, virulence and metabolism. Future Microbiol 2019; 14:801-828. [DOI: 10.2217/fmb-2019-0072] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Aim: Among the alternative sigma factors of Listeria monocytogenes, σB controls the largest regulon. The aim of this study was to perform a comprehensive review of σB-regulated genes, and the functions they confer. Materials & methods: A systematic search of PubMed and Web of Knowledge was carried out to identify members of the σB regulon based on experimental evidence of σB-dependent transcription and presence of a consensus σB-dependent promoter. Results: The literature review identified σB-dependent transcription units encompassing 304 genes encoding different functions including stress response and virulence. Conclusion: Our review supports the well-known roles of σB in virulence and stress response and provides new insight into novel roles for σB in metabolism and overall resilience of L. monocytogenes.
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Affiliation(s)
- Yichang Liu
- Department of Food Science, Cornell University, Ithaca, NY 14850, USA
| | - Renato H Orsi
- Department of Food Science, Cornell University, Ithaca, NY 14850, USA
| | - Ahmed Gaballa
- Department of Food Science, Cornell University, Ithaca, NY 14850, USA
| | - Martin Wiedmann
- Department of Food Science, Cornell University, Ithaca, NY 14850, USA
| | - Kathryn J Boor
- Department of Food Science, Cornell University, Ithaca, NY 14850, USA
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29
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Olwal CO, Ang'ienda PO, Ochiel DO. Alternative sigma factor B (σ B) and catalase enzyme contribute to Staphylococcus epidermidis biofilm's tolerance against physico-chemical disinfection. Sci Rep 2019; 9:5355. [PMID: 30926870 PMCID: PMC6440968 DOI: 10.1038/s41598-019-41797-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Accepted: 03/18/2019] [Indexed: 12/11/2022] Open
Abstract
Staphylococcus epidermidis is the predominant cause of recalcitrant biofilm-associated infections, which are often highly resistant to antibiotics. Thus, the use of physico-chemical agents for disinfection offers a more effective approach to the control of S. epidermidis biofilm infections. However, the underlying tolerance mechanisms employed by S. epidermidis biofilm against these physico-chemical disinfectants remain largely unknown. The expression of a σB-dependent gene, alkaline shock protein 23 (asp23) and catalase activity by S. epidermidis biofilm and planktonic cells exposed to heat (50 °C), 0.8 M sodium chloride (NaCl), 5 mM sodium hypochlorite (NaOCl) or 50 μM hydrogen peroxide (H2O2) for 60 minutes were compared. Significantly higher asp23 expression levels were observed in biofilms exposed to 50 °C, 5 mM NaOCl or 50 μM H2O2 compared to the corresponding planktonic cells (p < 0.05). Conversely, asp23 expression levels in biofilm and planktonic cells exposed to 0.8 M NaCl were not significantly different (p > 0.05). Further, biofilms exposed to 50 °C, 0.8 M NaCl, 5 mM NaOCl or 50 μM H2O2 exhibited significantly higher catalase activity than the planktonic cells (p < 0.05). These results suggest that activities of σB and catalase may be involved in the tolerance of S. epidermidis biofilm against physico-chemical disinfection.
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30
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Role and regulation of the stress activated sigma factor sigma B (σ B) in the saprophytic and host-associated life stages of Listeria monocytogenes. ADVANCES IN APPLIED MICROBIOLOGY 2019; 106:1-48. [PMID: 30798801 DOI: 10.1016/bs.aambs.2018.11.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The stress activated sigma factor sigma B (σB) plays a pivotal role in allowing the food-borne bacterial pathogen Listeria monocytogenes to modulate its transcriptional landscape in order to survive in a variety of harsh environments both outside and within the host. While we have a comparatively good understanding of the systems under the control of this sigma factor much less is known about how the activity of σB is controlled. In this review, we present a current model describing how this sigma factor is thought to be controlled including an overview of what is known about stress sensing and the early signal transduction events that trigger its activation. We discuss the known regulatory overlaps between σB and other protein and RNA regulators in the cell. Finally, we describe the role of σB in surviving both saprophytic and host-associated stresses. The complexity of the regulation of this sigma factor reflects the significant role that it plays in the persistence of this important pathogen in the natural environment, the food chain as well as within the host during the early stages of an infection. Understanding its regulation will be a critical step in helping to develop rational strategies to prevent its growth and survival in the food destined for human consumption and in the prevention of listeriosis.
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31
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Bucur FI, Grigore-Gurgu L, Crauwels P, Riedel CU, Nicolau AI. Resistance of Listeria monocytogenes to Stress Conditions Encountered in Food and Food Processing Environments. Front Microbiol 2018; 9:2700. [PMID: 30555426 PMCID: PMC6282059 DOI: 10.3389/fmicb.2018.02700] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 10/23/2018] [Indexed: 12/17/2022] Open
Abstract
Listeria monocytogenes is a human food-borne facultative intracellular pathogen that is resistant to a wide range of stress conditions. As a consequence, L. monocytogenes is extremely difficult to control along the entire food chain from production to storage and consumption. Frequent and recent outbreaks of L. monocytogenes infections illustrate that current measures of decontamination and preservation are suboptimal to control L. monocytogenes in food. In order to develop efficient measures to prevent contamination during processing and control growth during storage of food it is crucial to understand the mechanisms utilized by L. monocytogenes to tolerate the stress conditions in food matrices and food processing environments. Food-related stress conditions encountered by L. monocytogenes along the food chain are acidity, oxidative and osmotic stress, low or high temperatures, presence of bacteriocins and other preserving additives, and stresses as a consequence of applying alternative decontamination and preservation technologies such high hydrostatic pressure, pulsed and continuous UV light, pulsed electric fields (PEF). This review is aimed at providing a summary of the current knowledge on the response of L. monocytogenes toward these stresses and the mechanisms of stress resistance employed by this important food-borne bacterium. Circumstances when L. monocytogenes cells become more sensitive or more resistant are mentioned and existence of a cross-resistance when multiple stresses are present is pointed out.
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Affiliation(s)
- Florentina Ionela Bucur
- Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Galati, Romania
| | - Leontina Grigore-Gurgu
- Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Galati, Romania
| | - Peter Crauwels
- Institute of Microbiology and Biotechnology, Ulm University, Ulm, Germany
| | | | - Anca Ioana Nicolau
- Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Galati, Romania
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32
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de Grandi AZ, Pinto UM, Destro MT. Dual-species biofilm of Listeria monocytogenes and Escherichia coli on stainless steel surface. World J Microbiol Biotechnol 2018; 34:61. [PMID: 29651554 DOI: 10.1007/s11274-018-2445-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 04/09/2018] [Indexed: 11/25/2022]
Abstract
Listeria monocytogenes is a Gram-positive bacterium commonly associated with foodborne diseases. Due its ability to survive under adverse environmental conditions and to form biofilm, this bacterium is a major concern for the food industry, since it can compromise sanitation procedures and increase the risk of post-processing contamination. Little is known about the interaction between L. monocytogenes and Gram-negative bacteria on biofilm formation. Thus, in order to evaluate this interaction, Escherichia coli and L. monocytogenes were tested for their ability to form biofilms together or in monoculture. We also aimed to evaluate the ability of L. monocytogenes 1/2a and its isogenic mutant strain (ΔprfA ΔsigB) to form biofilm in the presence of E. coli. We assessed the importance of the virulence regulators, PrfA and σB, in this process since they are involved in many aspects of L. monocytogenes pathogenicity. Biofilm formation was assessed using stainless steel AISI 304 #4 slides immersed into brain heart infusion broth, reconstituted powder milk and E. coli preconditioned medium at 25 °C. Our results indicated that a higher amount of biofilm was formed by the wild type strain of L. monocytogenes than by its isogenic mutant, indicating that prfA and sigB are important for biofilm development, especially maturation under our experimental conditions. The presence of E. coli or its metabolites in preconditioned medium did not influence biofilm formation by L. monocytogenes. Our results confirm the possibility of concomitant biofilm formation by L. monocytogenes and E. coli, two bacteria of major significance in the food industry.
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Affiliation(s)
- Aline Zago de Grandi
- Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo, Av. Prof. Lineu Prestes 580 B.14, 05508-900, São Paulo, SP, Brazil
| | - Uelinton Manoel Pinto
- Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo, Av. Prof. Lineu Prestes 580 B.14, 05508-900, São Paulo, SP, Brazil.
- Food Research Center (FoRC), Faculty of Pharmaceutical Sciences, University of São Paulo, Av. Prof. Lineu Prestes 580 B.14, 05508-900, São Paulo, SP, Brazil.
| | - Maria Teresa Destro
- Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo, Av. Prof. Lineu Prestes 580 B.14, 05508-900, São Paulo, SP, Brazil
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33
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Pasquali F, Palma F, Guillier L, Lucchi A, De Cesare A, Manfreda G. Listeria monocytogenes Sequence Types 121 and 14 Repeatedly Isolated Within One Year of Sampling in a Rabbit Meat Processing Plant: Persistence and Ecophysiology. Front Microbiol 2018; 9:596. [PMID: 29662481 PMCID: PMC5890179 DOI: 10.3389/fmicb.2018.00596] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Accepted: 03/15/2018] [Indexed: 01/15/2023] Open
Abstract
Listeria monocytogenes is a foodborne pathogen adapted to survive and persist in multiple environments. Following two previous studies on prevalence and virulence of L. monocytogenes ST121 and ST14 repeatedly collected in a the same rabbit-meat processing plant, the research questions of the present study were to: (1) assess persistence of L. monocytogenes isolates from the rabbit-plant; (2) select genes associated to physiological adaptation to the food-processing environment; (3) compare presence/absence/truncation of these genes in newly sequenced and publicly available ST121 and ST14 genomes. A total of 273 draft genomes including ST121 and ST14 newly sequenced and publicly available draft genomes were analyzed. Whole-genome Single Nucleotide Polymorfism (wgSNP) analysis was performed separately on the assemblies of ST121 and ST14 draft genomes. SNPs alignments were used to infer phylogeny. A dataset of L. monocytogenes ecophysiology genes was built based on a comprehensive literature review. The 94 selected genes were screened on the assemblies of all ST121 and ST14 draft genomes. Significant gene enrichments were evaluated by statistical analyses. A persistent ST14 clone, including 23 out of 27 newly sequenced genomes, was circulating in the rabbit-meat plant along with two not persistent clones. A significant enrichment was observed in ST121 genomes concerning stress survival islet 2 (SSI-2) (alkaline and oxidative stress), qacH gene (resistance to benzalkonium chloride), cadA1C gene cassette (resistance to 70 mg/l of cadmium chloride) and a truncated version of actA gene (biofilm formation). Conversely, ST14 draft genomes were enriched with a full-length version of actA gene along with the Listeria Genomic Island 2 (LGI 2) including the ars operon (arsenic resistance) and the cadA4C gene cassette (resistance to 35 mg/l of cadmium chloride). Phenotypic tests confirmed ST121 as a weak biofilm producer in comparison to ST14. In conclusion, ST121 carried the qacH gene and was phenotypically resistant to quaternary ammonium compounds. This property might contribute to the high prevalence of ST121 in food processing plants. ST14 showed greater ability to form biofilms, which might contribute to the occasional colonization and persistence on harborage sites where sanitizing procedures are difficult to display.
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Affiliation(s)
- Frédérique Pasquali
- Dipartimento di Scienze e Tecnologie Agro-Alimentari, Alma Mater Studiorum - Università di Bologna, Bologna, Italy
| | - Federica Palma
- Dipartimento di Scienze e Tecnologie Agro-Alimentari, Alma Mater Studiorum - Università di Bologna, Bologna, Italy
| | - Laurent Guillier
- Laboratoire de Sécurité des Aliments, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail, Maisons-Alfort, France
| | - Alex Lucchi
- Dipartimento di Scienze e Tecnologie Agro-Alimentari, Alma Mater Studiorum - Università di Bologna, Bologna, Italy
| | - Alessandra De Cesare
- Dipartimento di Scienze e Tecnologie Agro-Alimentari, Alma Mater Studiorum - Università di Bologna, Bologna, Italy
| | - Gerardo Manfreda
- Dipartimento di Scienze e Tecnologie Agro-Alimentari, Alma Mater Studiorum - Università di Bologna, Bologna, Italy
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34
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Liu Y, Orsi RH, Boor KJ, Wiedmann M, Guariglia-Oropeza V. Home Alone: Elimination of All but One Alternative Sigma Factor in Listeria monocytogenes Allows Prediction of New Roles for σ B. Front Microbiol 2017; 8:1910. [PMID: 29075236 PMCID: PMC5641562 DOI: 10.3389/fmicb.2017.01910] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Accepted: 09/19/2017] [Indexed: 11/13/2022] Open
Abstract
Among Listeria monocytogenes' four alternative σ factors, σB controls the largest regulon. As σB-dependent transcription of some genes may be masked by overlaps among regulons, and as some σB-dependent genes are expressed only under very specific conditions, we hypothesized that the σB regulon is not yet fully defined. To further extend our understanding of the σB regulon, we used RNA-seq to identify σB-dependent genes in an L. monocytogenes strain that expresses σB following rhamnose induction, and in which genes encoding the other alternative sigma factors have been deleted. Analysis of RNA-seq data with multiple bioinformatics approaches, including a sliding window method that detects differentially transcribed 5' untranslated regions (UTRs), identified 105 σB-dependent transcription units (TUs) comprising 201 genes preceded by σB-dependent promoters. Of these 105 TUs, 7 TUs comprising 15 genes had not been identified previously as σB-dependent. An additional 23 genes not reported previously as σB-dependent were identified in 9 previously recognized σB-dependent TUs. Overall, 38 of these 201 genes had not been identified previously as members of the L. monocytogenes σB regulon. These newly identified σB-dependent genes encode proteins annotated as being involved in transcriptional regulation, oxidative and osmotic stress response, and in metabolism of energy, carbon and nucleotides. In total, 18 putative σB-dependent promoters were newly identified. Interestingly, a number of genes previously identified as σB-dependent did not show significant evidence for σB-dependent transcription in our experiments. Based on promoter analyses, a number of these genes showed evidence for co-regulation by σB and other transcriptional factors, suggesting that some σB-dependent genes require additional transcriptional regulators along with σB for transcription. Over-expression of a single alternative sigma factor in the absence of all other alternative sigma factors allowed us to: (i) identify new σB-dependent functions in L. monocytogenes, such as regulation of genes involved in 1,2-propanediol utilization (LMRG_00594-LMRG_00611) and biosynthesis of pyrimidine nucleotides (LMRG_00978-LMRG_00985); and (ii) identify new σB-dependent genes involved in stress response and pathogenesis functions. These data further support that σB not only regulates stress response functions, but also plays a broad role in L. monocytogenes homeostasis and resilience.
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Affiliation(s)
- Yichang Liu
- Department of Food Science, Cornell University, Ithaca, NY, United States
| | - Renato H Orsi
- Department of Food Science, Cornell University, Ithaca, NY, United States
| | - Kathryn J Boor
- Department of Food Science, Cornell University, Ithaca, NY, United States
| | - Martin Wiedmann
- Department of Food Science, Cornell University, Ithaca, NY, United States
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Vivant AL, Desneux J, Pourcher AM, Piveteau P. Transcriptomic Analysis of the Adaptation of Listeria monocytogenes to Lagoon and Soil Matrices Associated with a Piggery Environment: Comparison of Expression Profiles. Front Microbiol 2017; 8:1811. [PMID: 29018416 PMCID: PMC5623016 DOI: 10.3389/fmicb.2017.01811] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 09/05/2017] [Indexed: 12/20/2022] Open
Abstract
Understanding how Listeria monocytogenes, the causative agent of listeriosis, adapts to the environment is crucial. Adaptation to new matrices requires regulation of gene expression. To determine how the pathogen adapts to lagoon effluent and soil, two matrices where L. monocytogenes has been isolated, we compared the transcriptomes of L. monocytogenes CIP 110868 20 min and 24 h after its transfer to effluent and soil extract. Results showed major variations in the transcriptome of L. monocytogenes in the lagoon effluent but only minor modifications in the soil. In both the lagoon effluent and in the soil, genes involved in mobility and chemotaxis and in the transport of carbohydrates were the most frequently represented in the set of genes with higher transcript levels, and genes with phage-related functions were the most represented in the set of genes with lower transcript levels. A modification of the cell envelop was only found in the lagoon environment. Finally, the differential analysis included a large proportion of regulators, regulons, and ncRNAs.
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Affiliation(s)
- Anne-Laure Vivant
- UR OPAALE, IRSTEA, Rennes, France
- Université Bretagne Loire, Rennes, France
| | - Jeremy Desneux
- UR OPAALE, IRSTEA, Rennes, France
- Université Bretagne Loire, Rennes, France
| | | | - Pascal Piveteau
- Agroécologie, AgroSup Dijon, Institut National de la Recherche Agronomique, Université Bourgogne Franche-Comté, Dijon, France
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Omori Y, Miake K, Nakamura H, Kage-Nakadai E, Nishikawa Y. Influence of lactic acid and post-treatment recovery time on the heat resistance of Listeria monocytogenes. Int J Food Microbiol 2017. [DOI: 10.1016/j.ijfoodmicro.2017.06.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Guldimann C, Guariglia-Oropeza V, Harrand S, Kent D, Boor KJ, Wiedmann M. Stochastic and Differential Activation of σ B and PrfA in Listeria monocytogenes at the Single Cell Level under Different Environmental Stress Conditions. Front Microbiol 2017; 8:348. [PMID: 28352251 PMCID: PMC5349113 DOI: 10.3389/fmicb.2017.00348] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Accepted: 02/20/2017] [Indexed: 01/03/2023] Open
Abstract
During host infection, the foodborne pathogen Listeria monocytogenes must sense and respond to rapidly changing environmental conditions. Two transcriptional regulators, the alternative sigma factor B (σB) and the Positive Regulatory Factor A (PrfA), are key contributors to the transcriptomic responses that enable bacterial survival in the host gastrointestinal tract and invasion of host duodenal cells. Increases in temperature and osmolarity induce activity of these proteins; such conditions may be encountered in food matrices as well as within the host gastrointestinal tract. Differences in PrfA and σB activity between individual cells might affect the fate of a cell during host invasion, therefore, we hypothesized that PrfA and σB activities differ among individual cells under heat and salt stress. We used fluorescent reporter fusions to determine the relative proportions of cells with active σB or PrfA following exposure to 45°C heat or 4% NaCl. Activities of both PrfA and σB were induced stochastically, with fluorescence levels ranging from below detection to high among individual cells. The proportion of cells with active PrfA was significantly higher than the proportion with active σB under all tested conditions; under some conditions, nearly all cells had active PrfA. Our findings further support the growing body of evidence illustrating the stochastic nature of bacterial gene expression under conditions that are relevant for host invasion via food-borne, oral infection.
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Affiliation(s)
- Claudia Guldimann
- Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA
| | | | - Sophia Harrand
- Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA
| | - David Kent
- Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA
| | - Kathryn J Boor
- Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA
| | - Martin Wiedmann
- Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA
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Tremonte P, Succi M, Coppola R, Sorrentino E, Tipaldi L, Picariello G, Pannella G, Fraternali F. Homology-Based Modeling of Universal Stress Protein from Listeria innocua Up-Regulated under Acid Stress Conditions. Front Microbiol 2016; 7:1998. [PMID: 28066336 PMCID: PMC5168468 DOI: 10.3389/fmicb.2016.01998] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 11/29/2016] [Indexed: 01/31/2023] Open
Abstract
An Universal Stress Protein (USP) expressed under acid stress condition by Listeria innocua ATCC 33090 was investigated. The USP was up-regulated not only in the stationary phase but also during the exponential growth phase. The three dimensional (3D) structure of USP was predicted using a combined proteomic and bioinformatics approach. Phylogenetic analysis showed that the USP from Listeria detected in our study was distant from the USPs of other bacteria (such as Pseudomonas spp., Escherichia coli, Salmonella spp.) and clustered in a separate and heterogeneous class including several USPs from Listeria spp. and Lactobacillus spp. An important information on the studied USP was obtained from the 3D-structure established through the homology modeling procedure. In detail, the Model_USP-691 suggested that the investigated USP had a homo-tetrameric quaternary structure. Each monomer presented an architecture analogous to the Rossmann-like α/β-fold with five parallel β-strands, and four α-helices. The analysis of monomer-monomer interfaces and quality of the structure alignments confirmed the model reliability. In fact, the structurally and sequentially conserved hydrophobic residues of the β-strand 5 (in particular the residues V146 and V148) were involved in the inter-chains contact. Moreover, the highly conserved residues I139 and H141 in the region α4 were involved in the dimer association and functioned as hot spots into monomer–monomer interface assembly. The hypothetical assembly of dimers was also supported by the large interface area and by the negative value of solvation free energy gain upon interface interaction. Finally, the structurally conserved ATP-binding motif G-2X-G-9X-G(S/T-N) suggested for a putative role of ATP in stabilizing the tetrameric assembly of the USP. Therefore, the results obtained from a multiple approach, consisting in the application of kinetic, proteomic, phylogenetic and modeling analyses, suggest that Listeria USP could be considered a new type of ATP-binding USP involved in the response to acid stress condition during the exponential growth phase.
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Affiliation(s)
- Patrizio Tremonte
- Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy
| | - Mariantonietta Succi
- Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy
| | - Raffaele Coppola
- Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy
| | - Elena Sorrentino
- Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy
| | - Luca Tipaldi
- Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy
| | - Gianluca Picariello
- Institute of Food Science, National Research Council (ISA-CNR) Avellino, Italy
| | - Gianfranco Pannella
- Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy
| | - Franca Fraternali
- Randall Division of Cellular and Molecular Biophysics, New Hunt's House King's College London, UK
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Jarvis NA, O'Bryan CA, Ricke SC, Johnson MG, Crandall PG. A review of minimal and defined media for growth of Listeria monocytogenes. Food Control 2016. [DOI: 10.1016/j.foodcont.2016.02.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Huynh TN, Choi PH, Sureka K, Ledvina HE, Campillo J, Tong L, Woodward JJ. Cyclic di-AMP targets the cystathionine beta-synthase domain of the osmolyte transporter OpuC. Mol Microbiol 2016; 102:233-243. [PMID: 27378384 DOI: 10.1111/mmi.13456] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2016] [Indexed: 12/26/2022]
Abstract
Cellular turgor is of fundamental importance to bacterial growth and survival. Changes in external osmolarity as a consequence of fluctuating environmental conditions and colonization of diverse environments can significantly impact cytoplasmic water content, resulting in cellular lysis or plasmolysis. To ensure maintenance of appropriate cellular turgor, bacteria import ions and small organic osmolytes, deemed compatible solutes, to equilibrate cytoplasmic osmolarity with the extracellular environment. Here, we show that elevated levels of c-di-AMP, a ubiquitous second messenger among bacteria, result in significant susceptibility to elevated osmotic stress in the bacterial pathogen Listeria monocytogenes. We found that levels of import of the compatible solute carnitine show an inverse correlation with intracellular c-di-AMP content and that c-di-AMP directly binds to the CBS domain of the ATPase subunit of the carnitine importer OpuC. Biochemical and structural studies identify conserved residues required for this interaction and transport activity in bacterial cells. Overall, these studies reveal a role for c-di-AMP mediated regulation of compatible solute import and provide new insight into the molecular mechanisms by which this essential second messenger impacts bacterial physiology and adaptation to changing environmental conditions.
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Affiliation(s)
- TuAnh Ngoc Huynh
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA
| | - Philip H Choi
- Department of Biological Sciences, Columbia University, New York, NY, 10027, USA
| | - Kamakshi Sureka
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA
| | - Hannah E Ledvina
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA
| | - Julian Campillo
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY, 10027, USA.
| | - Joshua J Woodward
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA.
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Resilience in the Face of Uncertainty: Sigma Factor B Fine-Tunes Gene Expression To Support Homeostasis in Gram-Positive Bacteria. Appl Environ Microbiol 2016; 82:4456-4469. [PMID: 27208112 DOI: 10.1128/aem.00714-16] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Gram-positive bacteria are ubiquitous and diverse microorganisms that can survive and sometimes even thrive in continuously changing environments. The key to such resilience is the ability of members of a population to respond and adjust to dynamic conditions in the environment. In bacteria, such responses and adjustments are mediated, at least in part, through appropriate changes in the bacterial transcriptome in response to the conditions encountered. Resilience is important for bacterial survival in diverse, complex, and rapidly changing environments and requires coordinated networks that integrate individual, mechanistic responses to environmental cues to enable overall metabolic homeostasis. In many Gram-positive bacteria, a key transcriptional regulator of the response to changing environmental conditions is the alternative sigma factor σ(B) σ(B) has been characterized in a subset of Gram-positive bacteria, including the genera Bacillus, Listeria, and Staphylococcus Recent insight from next-generation-sequencing results indicates that σ(B)-dependent regulation of gene expression contributes to resilience, i.e., the coordination of complex networks responsive to environmental changes. This review explores contributions of σ(B) to resilience in Bacillus, Listeria, and Staphylococcus and illustrates recently described regulatory functions of σ(B).
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Loss of SigB in Listeria monocytogenes Strains EGD-e and 10403S Confers Hyperresistance to Hydrogen Peroxide in Stationary Phase under Aerobic Conditions. Appl Environ Microbiol 2016; 82:4584-4591. [PMID: 27208116 DOI: 10.1128/aem.00709-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 05/16/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED SigB is the main stress gene regulator in Listeria monocytogenes affecting the expression of more than 150 genes and thus contributing to multiple-stress resistance. Despite its clear role in most stresses, its role in oxidative stress is uncertain, as results accompanying the loss of sigB range from hyperresistance to hypersensitivity. Previously, these differences have been attributed to strain variation. In this study, we show conclusively that unlike for all other stresses, loss of sigB results in hyperresistance to H2O2 (more than 8 log CFU ml(-1) compared to the wild type) in aerobically grown stationary-phase cultures of L. monocytogenes strains 10403S and EGD-e. Furthermore, growth at 30°C resulted in higher resistance to oxidative stress than that at 37°C. Oxidative stress resistance seemed to be higher with higher levels of oxygen. Under anaerobic conditions, the loss of SigB in 10403S did not affect survival against H2O2, while in EGD-e, it resulted in a sensitive phenotype. During exponential phase, minor differences occurred, and this result was expected due to the absence of sigB transcription. Catalase tests were performed under all conditions, and stronger catalase results corresponded well with a higher survival rate, underpinning the important role of catalase in this phenotype. Furthermore, we assessed the catalase activity in protein lysates, which corresponded with the catalase tests and survival. In addition, reverse transcription-PCR (RT-PCR) showed no differences in transcription between the wild type and the ΔsigB mutant in various oxidative stress genes. Further investigation of the molecular mechanism behind this phenotype and its possible consequences for the overall phenotype of L. monocytogenes are under way. IMPORTANCE SigB is the most important stress gene regulator in L. monocytogenes and other Gram-positive bacteria. Its increased expression during stationary phase results in resistance to multiple stresses. However, despite its important role in general stress resistance, its expression is detrimental for the cell in the presence of oxidative stress, as it promotes hypersensitivity against hydrogen peroxide. This peculiar phenotype is an important element of the physiology of L. monocytogenes, and it might help us explain the behavior of this organism in environments where oxidative stress is present.
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O'Donoghue B, NicAogáin K, Bennett C, Conneely A, Tiensuu T, Johansson J, O'Byrne C. Blue-Light Inhibition of Listeria monocytogenes Growth Is Mediated by Reactive Oxygen Species and Is Influenced by σB and the Blue-Light Sensor Lmo0799. Appl Environ Microbiol 2016; 82:4017-4027. [PMID: 27129969 PMCID: PMC4907204 DOI: 10.1128/aem.00685-16] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 04/19/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Listeria monocytogenes senses blue light via the flavin mononucleotide-containing sensory protein Lmo0799, leading to activation of the general stress response sigma factor SigB (σ(B)). In this study, we investigated the physiological response of this foodborne pathogen to blue light. We show that blue light (460 to 470 nm) doses of 1.5 to 2 mW cm(-2) cause inhibition of growth on agar-based and liquid culture media. The inhibitory effects are dependent on cell density, with reduced effects evident when high cell numbers are present. The addition of 20 mM dimethylthiourea, a scavenger of reactive oxygen species, or catalase to the medium reverses the inhibitory effects of blue light, suggesting that growth inhibition is mediated by the formation of reactive oxygen species. A mutant strain lacking σ(B) (ΔsigB) was found to be less inhibited by blue light than the wild type, likely indicating the energetic cost of deploying the general stress response. When a lethal dose of light (8 mW cm(-2)) was applied to cells, the ΔsigB mutant displayed a marked increase in sensitivity to light compared to the wild type. To investigate the role of the blue-light sensor Lmo0799, mutants were constructed that either had a deletion of the gene (Δlmo0799) or alteration in a conserved cysteine residue at position 56, which is predicted to play a pivotal role in the photocycle of the protein (lmo0799 C56A). Both mutants displayed phenotypes similar to the ΔsigB mutant in the presence of blue light, providing genetic evidence that residue 56 is critical for light sensing in L. monocytogenes Taken together, these results demonstrate that L. monocytogenes is inhibited by blue light in a manner that depends on reactive oxygen species, and they demonstrate clear light-dependent phenotypes associated with σ(B) and the blue-light sensor Lmo0799. IMPORTANCE Listeria monocytogenes is a bacterial foodborne pathogen that can cause life-threatening infections in humans. It is known to be able to sense and respond to visible light. In this study, we examine the effects of blue light on the growth and survival of this pathogen. We show that growth can be inhibited at comparatively low doses of blue light, and that at higher doses, L. monocytogenes cells are killed. We present evidence suggesting that blue light inhibits this organism by causing the production of reactive oxygen species, such as hydrogen peroxide. We help clarify the mechanism of light sensing by constructing a "blind" version of the blue-light sensor protein. Finally, we show that activation of the general stress response by light has a negative effect on growth, probably because cellular resources are diverted into protective mechanisms rather than growth.
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Affiliation(s)
- Beth O'Donoghue
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Galway, Ireland
| | - Kerrie NicAogáin
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Galway, Ireland
| | - Claire Bennett
- National Centre for Laser Applications, School of Physics, National University of Ireland, Galway, Galway, Ireland
| | - Alan Conneely
- National Centre for Laser Applications, School of Physics, National University of Ireland, Galway, Galway, Ireland
| | - Teresa Tiensuu
- Department of Molecular Biology, Molecular Infection Medicine, Sweden, and Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Jörgen Johansson
- Department of Molecular Biology, Molecular Infection Medicine, Sweden, and Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Conor O'Byrne
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Galway, Ireland
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Müller-Herbst S, Wüstner S, Kabisch J, Pichner R, Scherer S. Acidified nitrite inhibits proliferation of Listeria monocytogenes - Transcriptional analysis of a preservation method. Int J Food Microbiol 2016; 226:33-41. [PMID: 27017279 DOI: 10.1016/j.ijfoodmicro.2016.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 02/29/2016] [Accepted: 03/05/2016] [Indexed: 11/16/2022]
Abstract
Sodium nitrite (NaNO2) is added as a preservative during raw meat processing such as raw sausage production to inhibit growth of pathogenic bacteria. In the present study it was shown in challenge assays that the addition of sodium nitrite indeed inhibited growth and survival of Listeria monocytogenes in short-ripened spreadable raw sausages. Furthermore, in vitro growth analyses were performed, which took into account combinations of various parameters of the raw sausage ripening process like temperature, oxygen availability, pH, NaCl concentration, and absence or presence of NaNO2. Data based on 300 growth conditions revealed that the inhibitory effect of nitrite was most prominent in combination with acidification, a combination that is also achieved during short-ripened spreadable raw sausage production. At pH6.0 and below, L. monocytogenes was unable to replicate in the presence of 200mg/l NaNO2. During the adaptation of L. monocytogenes to acidified nitrite stress (pH6.0, 200mg/l NaNO2) in comparison to acid exposure only (pH6.0, 0mg/l NaNO2), a massive transcriptional adaptation was observed using microarray analyses. In total, 202 genes were up-regulated and 204 genes were down-regulated. In accordance with growth inhibition, a down-regulation of genes encoding for proteins which are involved in central cellular processes, like cell wall/membrane/envelope biogenesis, translation and ribosomal structure and biogenesis, transcription, and replication, recombination and repair, was observed. Among the up-regulated genes the most prominent group belonged to poorly characterized genes. A considerable fraction of the up-regulated genes has been shown previously to be up-regulated intracellularly in macrophages, after exposure to acid shock or to be part of the SigB regulon. These data indicate that the adaptation to acidified nitrite partly overlaps with the adaptation to stress conditions being present during host colonization.
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Affiliation(s)
- Stefanie Müller-Herbst
- Lehrstuhl für Mikrobielle Ökologie, Technische Universität München, Weihenstephaner Berg 3, 85350 Freising, Germany; Zentralinstitut für Ernährungs- und Lebensmittelforschung (ZIEL), Technische Universität München, Weihenstephaner Berg 3, 85350 Freising, Germany.
| | - Stefanie Wüstner
- Lehrstuhl für Mikrobielle Ökologie, Technische Universität München, Weihenstephaner Berg 3, 85350 Freising, Germany.
| | - Jan Kabisch
- Institut für Mikrobiologie und Biotechnologie, MRI, Bundesforschungsinstitut für Ernährung und Lebensmittel, E.-C.-Baumann-Str. 20, 95326 Kulmbach, Germany.
| | - Rohtraud Pichner
- Institut für Mikrobiologie und Biotechnologie, MRI, Bundesforschungsinstitut für Ernährung und Lebensmittel, E.-C.-Baumann-Str. 20, 95326 Kulmbach, Germany.
| | - Siegfried Scherer
- Lehrstuhl für Mikrobielle Ökologie, Technische Universität München, Weihenstephaner Berg 3, 85350 Freising, Germany; Zentralinstitut für Ernährungs- und Lebensmittelforschung (ZIEL), Technische Universität München, Weihenstephaner Berg 3, 85350 Freising, Germany.
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The response of foodborne pathogens to osmotic and desiccation stresses in the food chain. Int J Food Microbiol 2016; 221:37-53. [PMID: 26803272 DOI: 10.1016/j.ijfoodmicro.2015.12.014] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 12/22/2015] [Accepted: 12/30/2015] [Indexed: 12/24/2022]
Abstract
In combination with other strategies, hyperosmolarity and desiccation are frequently used by the food processing industry as a means to prevent bacterial proliferation, and particularly that of foodborne pathogens, in food products. However, it is increasingly observed that bacteria, including human pathogens, encode mechanisms to survive and withstand these stresses. This review provides an overview of the mechanisms employed by Salmonella spp., Shiga toxin producing E. coli, Cronobacter spp., Listeria monocytogenes and Campylobacter spp. to tolerate osmotic and desiccation stresses and identifies gaps in knowledge which need to be addressed to ensure the safety of low water activity and desiccated food products.
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Rychli K, Grunert T, Ciolacu L, Zaiser A, Razzazi-Fazeli E, Schmitz-Esser S, Ehling-Schulz M, Wagner M. Exoproteome analysis reveals higher abundance of proteins linked to alkaline stress in persistent Listeria monocytogenes strains. Int J Food Microbiol 2015; 218:17-26. [PMID: 26594790 DOI: 10.1016/j.ijfoodmicro.2015.11.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 11/04/2015] [Accepted: 11/08/2015] [Indexed: 01/24/2023]
Abstract
The foodborne pathogen Listeria monocytogenes, responsible for listeriosis a rare but severe infection disease, can survive in the food processing environment for month or even years. So-called persistent L. monocytogenes strains greatly increase the risk of (re)contamination of food products, and are therefore a great challenge for food safety. However, our understanding of the mechanism underlying persistence is still fragmented. In this study we compared the exoproteome of three persistent strains with the reference strain EGDe under mild stress conditions using 2D differential gel electrophoresis. Principal component analysis including all differentially abundant protein spots showed that the exoproteome of strain EGDe (sequence type (ST) 35) is distinct from that of the persistent strain R479a (ST8) and the two closely related ST121 strains 4423 and 6179. Phylogenetic analyses based on multilocus ST genes showed similar grouping of the strains. Comparing the exoproteome of strain EGDe and the three persistent strains resulted in identification of 22 differentially expressed protein spots corresponding to 16 proteins. Six proteins were significantly increased in the persistent L. monocytogenes exoproteomes, among them proteins involved in alkaline stress response (e.g. the membrane anchored lipoprotein Lmo2637 and the NADPH dehydrogenase NamA). In parallel the persistent strains showed increased survival under alkaline stress, which is often provided during cleaning and disinfection in the food processing environments. In addition, gene expression of the proteins linked to stress response (Lmo2637, NamA, Fhs and QoxA) was higher in the persistent strain not only at 37 °C but also at 10 °C. Invasion efficiency of EGDe was higher in intestinal epithelial Caco2 and macrophage-like THP1 cells compared to the persistent strains. Concurrently we found higher expression of proteins involved in virulence in EGDe e.g. the actin-assembly-inducing protein ActA and the surface virulence associated protein SvpA. Furthermore proteins involved in cell wall modification, such as the lipoteichonic acid primase LtaP and the N-acetylmuramoyl-l-alanine amidase (Lmo2591) are more abundant in EGDe than in the persistent strains and could indirectly contribute to virulence. In conclusion this study provides information about a set of proteins that could potentially support survival of L. monocytogenes in abiotic niches in food processing environments. Based on these data, a more detailed analysis of the role of the identified proteins under stresses mimicking conditions in food producing environment is essential for further elucidate the mechanism of the phenomenon of persistence of L. monocytogenes.
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Affiliation(s)
- Kathrin Rychli
- Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
| | - Tom Grunert
- Functional Microbiology, Institute of Microbiology, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
| | - Luminita Ciolacu
- Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria; "Dunarea de Jos" University of Galaţi, 47 Domneasca St., 800008 Galaţi, Romania.
| | - Andreas Zaiser
- Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
| | - Ebrahim Razzazi-Fazeli
- VetCORE facility for research, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
| | - Stephan Schmitz-Esser
- Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
| | - Monika Ehling-Schulz
- Functional Microbiology, Institute of Microbiology, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
| | - Martin Wagner
- Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
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47
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Cebrián G, Arroyo C, Condón S, Mañas P. Osmotolerance provided by the alternative sigma factors σB and rpoS to Staphylococcus aureus and Escherichia coli is solute dependent and does not result in an increased growth fitness in NaCl containing media. Int J Food Microbiol 2015; 214:83-90. [PMID: 26256716 DOI: 10.1016/j.ijfoodmicro.2015.07.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Revised: 06/24/2015] [Accepted: 07/03/2015] [Indexed: 12/22/2022]
Abstract
The aim of this work was to examine the role of the alternative general stress sigma factors σ(B) and rpoS on the ability of Staphylococcus aureus and Escherichia coli, respectively, to grow in liquid and solid media of different osmolarity. For this purpose, S. aureus strain Newman and its isogenic ΔsigB mutant IK84 and E. coli strain BJ4 and its isogenic ΔrpoS mutant BJ4L1 were grown in media (TSBYE) with different concentrations of NaCl. Growth parameters (lag phase duration, growth rate and maximum number of microorganisms) and limiting growth concentrations (Maximum Non-Inhibitory Concentration - MNIC - and Minimum Inhibitory Concentration - MIC-) were determined. The mechanisms underlying the differences observed between parental and mutant strains were also explored. The absence of the sigma factors σ(B) and rpoS led to a decrease in the MNICs and MICs calculated for S. aureus and E. coli, respectively. Conversely, neither σ(B) nor rpoS provided with increased growth fitness to S. aureus and E. coli cells at NaCl concentrations up to 1.36M and 1M, respectively. The decreased osmotolerance of the σ(B) and rpoS deficient strains, as compared to their parental strains, was compensated by the addition of glycine-betaine (1mM) to the growth medium. It was also observed that the decreased tolerance to NaCl of the mutant strains was coincident with a decreased tolerance to sucrose, KCl, and LiCl but not to glycerol, MgCl2, and CaCl2. Results obtained also demonstrate that the increased osmotolerance of stationary growth phase E. coli cells, as compared to exponential growth phase ones, would be due to the activation of both rpoS-independent and rpoS-dependent mechanisms. This work will help to understand the mechanisms of bacterial resistance to osmotic stress and the role of the alternative sigma factors σ(B) and rpoS in this process.
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Affiliation(s)
- G Cebrián
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain.
| | - C Arroyo
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain
| | - S Condón
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain
| | - P Mañas
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain
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48
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Saá Ibusquiza P, Nierop Groot M, Debán-Valles A, Abee T, den Besten HM. Impact of growth conditions and role of sigB on Listeria monocytogenes fitness in single and mixed biofilms cultured with Lactobacillus plantarum. Food Res Int 2015. [DOI: 10.1016/j.foodres.2015.03.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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49
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Affiliation(s)
- Máire Begley
- Department of Biological Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland;
| | - Colin Hill
- School of Microbiology and Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland;
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50
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Role of sigB and osmolytes in desiccation survival of Listeria monocytogenes in simulated food soils on the surface of food grade stainless steel. Food Microbiol 2015; 46:443-451. [DOI: 10.1016/j.fm.2014.09.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/05/2014] [Accepted: 09/12/2014] [Indexed: 11/24/2022]
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