1
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Liu Y, Cui P, Tan R, Ru S. Rapid Membrane-Penetrating Hybrid Peptides Achieve Efficient Dual Antimicrobial and Antibiofilm Activity through a Triple Bactericidal Mechanism. ACS OMEGA 2024; 9:26133-26148. [PMID: 38911764 PMCID: PMC11191078 DOI: 10.1021/acsomega.4c01577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 05/21/2024] [Accepted: 05/24/2024] [Indexed: 06/25/2024]
Abstract
Antimicrobial peptides (AMPs) are a type of biomaterial used against multidrug resistant (MDR) bacteria. This study reports the design of a peptide family rich in tryptophan and lysine obtained by optimizing a natural AMP using single factor modification and pheromone hybridization to expedite the penetration and improve the antimicrobial activity of AMPs. S-4, L-4, and P-4 showed α-helical structures, exhibited extremely fast membrane penetration rates in vitro, and could kill MDR bacteria efficiently within 30 min. Intracellular fluorescence localization suggested rapid membrane-penetrating of AMPs within 1 min, making it more difficult for bacteria to develop resistance. Furthermore, they could effectively inhibit and destroy bacterial biofilms with dual antimicrobial and antibiofilm activity. In the treatment of skin infections caused by MDR-Acinetobacter baumannii in vivo , AMPs could effectively alleviate inflammation without toxic side effects. Additionally, the triple antimicrobial damage of AMPs was described in detail. AMPs rapidly penetrate the cell membrane, inducing cell membrane damage, triggering oxidative damage with a storm of reactive oxygen species and leading to bacterial death through leakage of cellular contents by complexing with DNA. The multiple damage is an important means by which AMPs can prevent bacterial resistance adequately.
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Affiliation(s)
| | | | - Rong Tan
- Lab of Environmental Health
and Ecological Engineering, College of Marine Life Science, Ocean University of China, Qingdao 266003, China
| | - Shaoguo Ru
- Lab of Environmental Health
and Ecological Engineering, College of Marine Life Science, Ocean University of China, Qingdao 266003, China
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2
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Lima LS, Müller TN, Ansiliero R, Schuster MB, Silva BL, Jaskulski IB, da Silva WP, Moroni LS. Biofilm formation by Listeria monocytogenes from the meat processing industry environment and the use of different combinations of detergents, sanitizers, and UV-A radiation to control this microorganism in planktonic and sessile forms. Braz J Microbiol 2024:10.1007/s42770-024-01361-7. [PMID: 38767749 DOI: 10.1007/s42770-024-01361-7] [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: 12/06/2023] [Accepted: 04/29/2024] [Indexed: 05/22/2024] Open
Abstract
This study aimed to evaluate the ability of biofilm formation by L. monocytogenes from the meat processing industry environment, as well as the use of different combinations of detergents, sanitizers, and UV-A radiation in the control of this microorganism in the planktonic and sessile forms. Four L. monocytogenes isolates were evaluated and showed moderate ability to form biofilm, as well as carried genes related to biofilm production (agrB, agrD, prfA, actA, cheA, cheY, flaA, sigB), and genes related to tolerance to sanitizers (lde and qacH). The biofilm-forming isolates of L. monocytogenes were susceptible to quaternary ammonium compound (QAC) and peracetic acid (PA) in planktonic form, with minimum inhibitory concentrations of 125 and 75 ppm, respectively, for contact times of 10 and 5 min. These concentrations are lower than those recommended by the manufacturers, which are at least 200 and 300 ppm for QAC and PA, respectively. Biofilms of L. monocytogenes formed from a pool of isolates on stainless steel and polyurethane coupons were subjected to 14 treatments involving acid and enzymatic detergents, QAC and PA sanitizers, and UV-A radiation at varying concentrations and contact times. All treatments reduced L. monocytogenes counts in the biofilm, indicating that the tested detergents, sanitizers, and UV-A radiation exhibited antimicrobial activity against biofilms on both surface types. Notably, the biofilm formed on polyurethane showed greater tolerance to the evaluated compounds than the biofilm on stainless steel, likely due to the material's surface facilitating faster microbial colonization and the development of a more complex structure, as observed by scanning electron microscopy. Listeria monocytogenes isolates from the meat processing industry carry genes associated with biofilm production and can form biofilms on both stainless steel and polyurethane surfaces, which may contribute to their persistence within meat processing lines. Despite carrying sanitizer tolerance genes, QAC and PA effectively controlled these microorganisms in their planktonic form. However, combinations of detergent (AC and ENZ) with sanitizers (QAC and PA) at minimum concentrations of 125 ppm and 300 ppm, respectively, were the most effective.
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Affiliation(s)
- Larissa Siqueira Lima
- Departamento de Engenharia de Alimentos e Engenharia Química, Universidade do Estado de Santa Catarina, Pinhalzinho, SC, 89870-000, Brazil
| | - Taís Nunzio Müller
- Departamento de Engenharia de Alimentos e Engenharia Química, Universidade do Estado de Santa Catarina, Pinhalzinho, SC, 89870-000, Brazil
| | - Rafaela Ansiliero
- Departamento de Engenharia de Alimentos e Engenharia Química, Universidade do Estado de Santa Catarina, Pinhalzinho, SC, 89870-000, Brazil
| | - Marcia Bär Schuster
- Departamento de Engenharia de Alimentos e Engenharia Química, Universidade do Estado de Santa Catarina, Pinhalzinho, SC, 89870-000, Brazil
| | - Bruna Louise Silva
- Centro Multiusuário, Centro de Ciências Tecnológicas, Universidade do Estado de Santa Catarina, Joinville, SC, 89219-710, Brazil
| | - Itiane Barcellos Jaskulski
- Departamento de Ciência e Tecnologia Agroindustrial, Faculdade de Agronomia, Universidade Federal de Pelotas, Capão do Leão, RS, 96001-970, Brazil
- Centro de Desenvolvimento Tecnológico, Departamento de Biotecnologia, Universidade Federal de Pelotas, Pelotas, RS, 960110-610, Brazil
| | - Wladimir Padilha da Silva
- Departamento de Ciência e Tecnologia Agroindustrial, Faculdade de Agronomia, Universidade Federal de Pelotas, Capão do Leão, RS, 96001-970, Brazil
- Centro de Desenvolvimento Tecnológico, Departamento de Biotecnologia, Universidade Federal de Pelotas, Pelotas, RS, 960110-610, Brazil
| | - Liziane Schittler Moroni
- Departamento de Engenharia de Alimentos e Engenharia Química, Universidade do Estado de Santa Catarina, Pinhalzinho, SC, 89870-000, Brazil.
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3
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Pan X, Shen J, Hong Y, Wu Y, Guo D, Zhao L, Bu X, Ben L, Wang X. Comparative Analysis of Growth, Survival, and Virulence Characteristics of Listeria monocytogenes Isolated from Imported Meat. Microorganisms 2024; 12:345. [PMID: 38399749 PMCID: PMC10891628 DOI: 10.3390/microorganisms12020345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 01/28/2024] [Accepted: 02/01/2024] [Indexed: 02/25/2024] Open
Abstract
Listeria monocytogenes is an important foodborne pathogen with worldwide prevalence. Understanding the variability in the potential pathogenicity among strains of different subtypes is crucial for risk assessment. In this study, the growth, survival, and virulence characteristics of 16 L. monocytogenes strains isolated from imported meat in China (2018-2020) were investigated. The maximum specific growth rate (μmax) and lag phase (λ) were evaluated using the time-to-detection (TTD) method and the Baranyi model at different temperatures (25, 30, and 37 °C). Survival characteristics were determined by D-values and population reduction after exposure to heat (60, 62.5, and 65 °C) and acid (HCl, pH = 2.5, 3.5, and 4.5). The potential virulence was evaluated via adhesion and invasion to Caco-2 cells, motility, and lethality to Galleria mellonella. The potential pathogenicity was compared among strains of different lineages and subtypes. The results indicate that the lineage I strains exhibited a higher growth rate than the lineage II strains at three growth temperatures, particularly serotype 4b within lineage I. At all temperatures tested, serotypes 1/2a and 1/2b consistently demonstrated higher heat resistance than the other subtypes. No significant differences in the log reduction were observed between the lineage I and lineage II strains at pH 2.5, 3.5, and 4.5. However, the serotype 1/2c strains exhibited significantly low acid resistance at pH 2.5. In terms of virulence, the lineage I strains outperformed the lineage II strains. The invasion rate to Caco-2 cells and lethality to G. mellonella exhibited by the serotype 4b strains were higher than those observed in the other serotypes. This study provides meaningful insights into the growth, survival, and virulence of L. monocytogenes, offering valuable information for understanding the correlation between the pathogenicity and subtypes of L. monocytogenes.
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Affiliation(s)
- Xinye Pan
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; (X.P.); (Y.H.); (X.B.); (L.B.)
| | - Jinling Shen
- Technology Center for Animal Plant and Food Inspection and Quarantine of Shanghai Customs, Shanghai 200135, China; (J.S.); (D.G.); (L.Z.)
| | - Yi Hong
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; (X.P.); (Y.H.); (X.B.); (L.B.)
| | - Yufan Wu
- Centre of Analysis and Test, School of Chemistry & Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China;
| | - Dehua Guo
- Technology Center for Animal Plant and Food Inspection and Quarantine of Shanghai Customs, Shanghai 200135, China; (J.S.); (D.G.); (L.Z.)
| | - Lina Zhao
- Technology Center for Animal Plant and Food Inspection and Quarantine of Shanghai Customs, Shanghai 200135, China; (J.S.); (D.G.); (L.Z.)
| | - Xiangfeng Bu
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; (X.P.); (Y.H.); (X.B.); (L.B.)
| | - Leijie Ben
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; (X.P.); (Y.H.); (X.B.); (L.B.)
| | - Xiang Wang
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; (X.P.); (Y.H.); (X.B.); (L.B.)
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4
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Meireles D, Pombinho R, Cabanes D. Signals behind Listeria monocytogenes virulence mechanisms. Gut Microbes 2024; 16:2369564. [PMID: 38979800 PMCID: PMC11236296 DOI: 10.1080/19490976.2024.2369564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 06/13/2024] [Indexed: 07/10/2024] Open
Abstract
The tight and coordinated regulation of virulence gene expression is crucial to ensure the survival and persistence of bacterial pathogens in different contexts within their hosts. Considering this, bacteria do not express virulence factors homogenously in time and space, either due to their associated fitness cost or to their detrimental effect at specific infection stages. To efficiently infect and persist into their hosts, bacteria have thus to monitor environmental cues or chemical cell-to-cell signaling mechanisms that allow their transition from the external environment to the host, and therefore adjust gene expression levels, intrinsic biological activities, and appropriate behaviors. Listeria monocytogenes (Lm), a major Gram-positive facultative intracellular pathogen, stands out for its adaptability and capacity to thrive in a wide range of environments. Because of that, Lm presents itself as a significant concern in food safety and public health, that can lead to potentially life-threatening infections in humans. A deeper understanding of the intricate bacterial virulence mechanisms and the signals that control them provide valuable insights into the dynamic interplay between Lm and the host. Therefore, this review addresses the role of some crucial signals behind Lm pathogenic virulence mechanisms and explores how the ability to assimilate and interpret these signals is fundamental for pathogenesis, identifying potential targets for innovative antimicrobial strategies.
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Affiliation(s)
- Diana Meireles
- Instituto de Investigação e Inovação em Saúde, Porto, Portugal
- Group of Molecular Microbiology, IBMC, Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar – ICBAS, Porto, Portugal
| | - Rita Pombinho
- Instituto de Investigação e Inovação em Saúde, Porto, Portugal
- Group of Molecular Microbiology, IBMC, Porto, Portugal
| | - Didier Cabanes
- Instituto de Investigação e Inovação em Saúde, Porto, Portugal
- Group of Molecular Microbiology, IBMC, Porto, Portugal
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5
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Schilcher K, Severn MM, Jenul C, Avina YSC, Keogh RA, Horswill AR. The Staphylococcus aureus CamS lipoprotein is a repressor of toxin production that shapes host-pathogen interaction. PLoS Biol 2024; 22:e3002451. [PMID: 38180978 PMCID: PMC10769083 DOI: 10.1371/journal.pbio.3002451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 11/27/2023] [Indexed: 01/07/2024] Open
Abstract
Lipoproteins of the opportunistic pathogen Staphylococcus aureus play a crucial role in various cellular processes and host interactions. Consisting of a protein and a lipid moiety, they support nutrient acquisition and anchor the protein to the bacterial membrane. Recently, we identified several processed and secreted small linear peptides that derive from the secretion signal sequence of S. aureus lipoproteins. Here, we show, for the first time, that the protein moiety of the S. aureus lipoprotein CamS has a biological role that is distinct from its associated linear peptide staph-cAM373. The small peptide was shown to be involved in interspecies horizontal gene transfer, the primary mechanism for the dissemination of antibiotic resistance among bacteria. We provide evidence that the CamS protein moiety is a potent repressor of cytotoxins, such as α-toxin and leukocidins. The CamS-mediated suppression of toxin transcription was reflected by altered disease severity in in vivo infection models involving skin and soft tissue, as well as bloodstream infections. Collectively, we have uncovered the role of the protein moiety of the staphylococcal lipoprotein CamS as a previously uncharacterized repressor of S. aureus toxin production, which consequently regulates virulence and disease outcomes. Notably, the camS gene is conserved in S. aureus, and we also demonstrated the muted transcriptional response of cytotoxins in 2 different S. aureus lineages. Our findings provide the first evidence of distinct biological functions of the protein moiety and its associated linear peptide for a specific lipoprotein. Therefore, lipoproteins in S. aureus consist of 3 functional components: a lipid moiety, a protein moiety, and a small linear peptide, with putative different biological roles that might not only determine the outcome of host-pathogen interactions but also drive the acquisition of antibiotic resistance determinants.
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Affiliation(s)
- Katrin Schilcher
- Department of Immunology and Microbiology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, United States of America
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Morgan M. Severn
- Department of Immunology and Microbiology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Christian Jenul
- Department of Immunology and Microbiology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, United States of America
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Young-Saeng C. Avina
- Department of Immunology and Microbiology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Rebecca A. Keogh
- Department of Immunology and Microbiology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Alexander R. Horswill
- Department of Immunology and Microbiology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, United States of America
- Department of Veterans Affairs, Eastern Colorado Health Care System, Aurora, Colorado, United States of America
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6
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Vaval Taylor DM, Xayarath B, Freitag NE. Two Permeases Associated with the Multifunctional CtaP Cysteine Transport System in Listeria monocytogenes Play Distinct Roles in Pathogenesis. Microbiol Spectr 2023; 11:e0331722. [PMID: 37199604 PMCID: PMC10269559 DOI: 10.1128/spectrum.03317-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Accepted: 04/05/2023] [Indexed: 05/19/2023] Open
Abstract
The soil-dwelling bacterium Listeria monocytogenes survives a multitude of conditions when residing in the outside environment and as a pathogen within host cells. Key to survival within the infected mammalian host is the expression of bacterial gene products necessary for nutrient acquisition. Similar to many bacteria, L. monocytogenes uses peptide import to acquire amino acids. Peptide transport systems play an important role in nutrient uptake as well as in additional functions that include bacterial quorum sensing and signal transduction, recycling of peptidoglycan fragments, adherence to eukaryotic cells, and alterations in antibiotic susceptibility. It has been previously described that CtaP, encoded by lmo0135, is a multifunctional protein associated with activities that include cysteine transport, resistance to acid, membrane integrity, and bacterial adherence to host cells. ctaP is located next to two genes predicted to encode membrane-bound permeases lmo0136 and lmo0137, termed CtpP1 and CtpP2, respectively. Here, we show that CtpP1 and CtpP2 are required for bacterial growth in the presence of low concentrations of cysteine and for virulence in mouse infection models. Taken together, the data identify distinct nonoverlapping roles for two related permeases that are important for the growth and survival of L. monocytogenes within host cells. IMPORTANCE Bacterial peptide transport systems are important for nutrient uptake and may additionally function in a variety of other roles, including bacterial communication, signal transduction, and bacterial adherence to eukaryotic cells. Peptide transport systems often consist of a substrate-binding protein associated with a membrane-spanning permease. The environmental bacterial pathogen Listeria monocytogenes uses the substrate-binding protein CtaP not only for cysteine transport but also for resistance to acid, maintenance of membrane integrity, and bacterial adherence to host cells. In this study, we demonstrate complementary yet distinct functional roles for two membrane permeases, CtpP1 and CtpP2, that are encoded by genes linked to ctaP and that contribute to bacterial growth, invasion, and pathogenicity.
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Affiliation(s)
- Diandra M. Vaval Taylor
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Bobbi Xayarath
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Nancy E. Freitag
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
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7
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Rivera-Lugo R, Huang S, Lee F, Méheust R, Iavarone AT, Sidebottom AM, Oldfield E, Portnoy DA, Light SH. Distinct Energy-Coupling Factor Transporter Subunits Enable Flavin Acquisition and Extracytosolic Trafficking for Extracellular Electron Transfer in Listeria monocytogenes. mBio 2023; 14:e0308522. [PMID: 36744898 PMCID: PMC9973259 DOI: 10.1128/mbio.03085-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 01/05/2023] [Indexed: 02/07/2023] Open
Abstract
A variety of electron transfer mechanisms link bacterial cytosolic electron pools with functionally diverse redox activities in the cell envelope and extracellular space. In Listeria monocytogenes, the ApbE-like enzyme FmnB catalyzes extracytosolic protein flavinylation, covalently linking a flavin cofactor to proteins that transfer electrons to extracellular acceptors. L. monocytogenes uses an energy-coupling factor (ECF) transporter complex that contains distinct substrate-binding, transmembrane, ATPase A, and ATPase A' subunits (RibU, EcfT, EcfA, and EcfA') to import environmental flavins, but the basis of extracytosolic flavin trafficking for FmnB flavinylation remains poorly defined. In this study, we show that the EetB and FmnA proteins are related to ECF transporter substrate-binding and transmembrane subunits, respectively, and are essential for exporting flavins from the cytosol for flavinylation. Comparisons of the flavin import versus export capabilities of L. monocytogenes strains lacking different ECF transporter subunits demonstrate a strict directionality of substrate-binding subunit transport but partial functional redundancy of transmembrane and ATPase subunits. Based on these results, we propose that ECF transporter complexes with different subunit compositions execute directional flavin import/export through a broadly conserved mechanism. Finally, we present genomic context analyses that show that related ECF exporter genes are distributed across members of the phylum Firmicutes and frequently colocalize with genes encoding flavinylated extracytosolic proteins. These findings clarify the basis of ECF transporter export and extracytosolic flavin cofactor trafficking in Firmicutes. IMPORTANCE Bacteria import vitamins and other essential compounds from their surroundings but also traffic related compounds from the cytosol to the cell envelope where they serve various functions. Studying the foodborne pathogen Listeria monocytogenes, we find that the modular use of subunits from a prominent class of bacterial transporters enables the import of environmental vitamin B2 cofactors and the extracytosolic trafficking of a vitamin B2-derived cofactor that facilitates redox reactions in the cell envelope. These studies clarify the basis of bidirectional small-molecule transport across the cytoplasmic membrane and the assembly of redox-active proteins within the cell envelope and extracellular space.
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Affiliation(s)
- Rafael Rivera-Lugo
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Shuo Huang
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Frank Lee
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Raphaël Méheust
- Génomique Métabolique, CEA, Genoscope, Institut François Jacob, Université d’Évry, Université Paris-Saclay, CNRS, Evry, France
| | - Anthony T. Iavarone
- QB3/Chemistry Mass Spectrometry Facility, University of California, Berkeley, Berkeley, California, USA
| | | | - Eric Oldfield
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Daniel A. Portnoy
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Samuel H. Light
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
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8
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Listeria monocytogenes-How This Pathogen Uses Its Virulence Mechanisms to Infect the Hosts. Pathogens 2022; 11:pathogens11121491. [PMID: 36558825 PMCID: PMC9783847 DOI: 10.3390/pathogens11121491] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/23/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022] Open
Abstract
Listeriosis is a serious food-borne illness, especially in susceptible populations, including children, pregnant women, and elderlies. The disease can occur in two forms: non-invasive febrile gastroenteritis and severe invasive listeriosis with septicemia, meningoencephalitis, perinatal infections, and abortion. Expression of each symptom depends on various bacterial virulence factors, immunological status of the infected person, and the number of ingested bacteria. Internalins, mainly InlA and InlB, invasins (invasin A, LAP), and other surface adhesion proteins (InlP1, InlP4) are responsible for epithelial cell binding, whereas internalin C (InlC) and actin assembly-inducing protein (ActA) are involved in cell-to-cell bacterial spread. L. monocytogenes is able to disseminate through the blood and invade diverse host organs. In persons with impaired immunity, the elderly, and pregnant women, the pathogen can also cross the blood-brain and placental barriers, which results in the invasion of the central nervous system and fetus infection, respectively. The aim of this comprehensive review is to summarize the current knowledge on the epidemiology of listeriosis and L. monocytogenes virulence mechanisms that are involved in host infection, with a special focus on their molecular and cellular aspects. We believe that all this information is crucial for a better understanding of the pathogenesis of L. monocytogenes infection.
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9
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Bacterial communication in the regulation of stress response in Listeria monocytogenes. Lebensm Wiss Technol 2022. [DOI: 10.1016/j.lwt.2021.112703] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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10
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Lee CD, Rizvi A, Edwards AN, DiCandia MA, Vargas Cuebas GG, Monteiro MP, McBride SM. Genetic mechanisms governing sporulation initiation in Clostridioides difficile. Curr Opin Microbiol 2021; 66:32-38. [PMID: 34933206 DOI: 10.1016/j.mib.2021.12.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 12/03/2021] [Accepted: 12/05/2021] [Indexed: 12/15/2022]
Abstract
As an anaerobe, Clostridioides difficile relies on the formation of a dormant spore for survival outside of the mammalian host's gastrointestinal tract. The spore is recalcitrant to desiccation, numerous disinfectants, UV light, and antibiotics, permitting long-term survival against environmental insults and efficient transmission from host to host. Although the morphological stages of spore formation are similar between C. difficile and other well-studied endospore-forming bacteria, the C. difficile genome does not appear to encode many of the known, conserved regulatory factors that are necessary to initiate sporulation in other spore-forming bacteria. The absence of early sporulation-specific orthologs suggests that C. difficile has evolved to control sporulation initiation in response to its unique and specific ecological niche and environmental cues within the host. Here, we review our current understanding and highlight the recent discoveries that have begun to unravel the regulatory pathways and molecular mechanisms by which C. difficile induces spore formation.
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Affiliation(s)
- Cheyenne D Lee
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Arshad Rizvi
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Adrianne N Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Michael A DiCandia
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Germán G Vargas Cuebas
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Marcos P Monteiro
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Shonna M McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA.
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11
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Quereda JJ, Morón-García A, Palacios-Gorba C, Dessaux C, García-del Portillo F, Pucciarelli MG, Ortega AD. Pathogenicity and virulence of Listeria monocytogenes: A trip from environmental to medical microbiology. Virulence 2021; 12:2509-2545. [PMID: 34612177 PMCID: PMC8496543 DOI: 10.1080/21505594.2021.1975526] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 08/23/2021] [Accepted: 08/25/2021] [Indexed: 01/02/2023] Open
Abstract
Listeria monocytogenes is a saprophytic gram-positive bacterium, and an opportunistic foodborne pathogen that can produce listeriosis in humans and animals. It has evolved an exceptional ability to adapt to stress conditions encountered in different environments, resulting in a ubiquitous distribution. Because some food preservation methods and disinfection protocols in food-processing environments cannot efficiently prevent contaminations, L. monocytogenes constitutes a threat to human health and a challenge to food safety. In the host, Listeria colonizes the gastrointestinal tract, crosses the intestinal barrier, and disseminates through the blood to target organs. In immunocompromised individuals, the elderly, and pregnant women, the pathogen can cross the blood-brain and placental barriers, leading to neurolisteriosis and materno-fetal listeriosis. Molecular and cell biology studies of infection have proven L. monocytogenes to be a versatile pathogen that deploys unique strategies to invade different cell types, survive and move inside the eukaryotic host cell, and spread from cell to cell. Here, we present the multifaceted Listeria life cycle from a comprehensive perspective. We discuss genetic features of pathogenic Listeria species, analyze factors involved in food contamination, and review bacterial strategies to tolerate stresses encountered both during food processing and along the host's gastrointestinal tract. Then we dissect host-pathogen interactions underlying listerial pathogenesis in mammals from a cell biology and systemic point of view. Finally, we summarize the epidemiology, pathophysiology, and clinical features of listeriosis in humans and animals. This work aims to gather information from different fields crucial for a comprehensive understanding of the pathogenesis of L. monocytogenes.
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Affiliation(s)
- Juan J. Quereda
- Departamento de Producción y Sanidad Animal, Salud Pública Veterinaria y Ciencia y Tecnología de los Alimentos, Facultad de Veterinaria, Universidad Cardenal Herrera-CEU, CEU Universities. Valencia, Spain
| | - Alvaro Morón-García
- Departamento de Biología Celular. Facultad de Ciencias Biológicas, Universidad Complutense de Madrid. Madrid, Spain
| | - Carla Palacios-Gorba
- Departamento de Producción y Sanidad Animal, Salud Pública Veterinaria y Ciencia y Tecnología de los Alimentos, Facultad de Veterinaria, Universidad Cardenal Herrera-CEU, CEU Universities. Valencia, Spain
| | - Charlotte Dessaux
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB)- Consejo Superior De Investigaciones Científicas (CSIC), Madrid, Spain
| | - Francisco García-del Portillo
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB)- Consejo Superior De Investigaciones Científicas (CSIC), Madrid, Spain
| | - M. Graciela Pucciarelli
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB)- Consejo Superior De Investigaciones Científicas (CSIC), Madrid, Spain
- Centro de Biología Molecular ‘Severo Ochoa’. Departamento de Biología Molecular, Facultad de Ciencias, Universidad Autónoma de Madrid. Madrid, Spain
| | - Alvaro D. Ortega
- Departamento de Biología Celular. Facultad de Ciencias Biológicas, Universidad Complutense de Madrid. Madrid, Spain
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB)- Consejo Superior De Investigaciones Científicas (CSIC), Madrid, Spain
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12
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Tan R, Wang M, Xu H, Qin L, Wang J, Cui P, Ru S. Improving the Activity of Antimicrobial Peptides Against Aquatic Pathogen Bacteria by Amino Acid Substitutions and Changing the Ratio of Hydrophobic Residues. Front Microbiol 2021; 12:773076. [PMID: 34733268 PMCID: PMC8558516 DOI: 10.3389/fmicb.2021.773076] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 09/28/2021] [Indexed: 12/02/2022] Open
Abstract
With the increasing number of drug-resistant bacteria, there is an urgent need for new antimicrobial agents, and antimicrobial peptides (AMPs), which exist in the human non-specific immune system, are one of the most promising candidates. It is an effective optimization strategy to modify antimicrobial peptides (AMPs) according to the distribution of amino acids and hydrophobic characteristics. The addition of bacterial pheromones to the N short peptide can increase the ability to recognize bacteria. In this study, we designed and synthesized AMP1–6 by amino acid substitution of mBjAMP1. Additionally, P-6, S-6, and L-6 were designed and synthesized by adding bacterial pheromones based on 1–6. Functional tests showed that the four AMPs had the ability to kill Gram-negative Vibrio anguillarum, Pseudomonas mendocina, and Vibrio parahaemolyticus, and Gram-positive Micrococcus luteus and Listeria monocytogenes. Additionally, all four AMPs induced permeabilization and depolarization of bacterial cell membranes and increased intracellular reactive oxygen species (ROS) levels. Importantly, they had little or no mammalian cytotoxicity. At the same time, 1–6 and L-6 protected the stability of intestinal flora in Sebastes schlegelii and increased the relative abundance of Lactobacillaceae. In summary, our results indicate that the designed AMPs have broad application prospects as a new type of polypeptide antimicrobial agent.
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Affiliation(s)
- Rong Tan
- College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Meiru Wang
- College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Huiqin Xu
- College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Lu Qin
- College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Jun Wang
- College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Pengfei Cui
- College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Shaoguo Ru
- College of Marine Life Science, Ocean University of China, Qingdao, China
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13
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Marito S, Keshari S, Traisaeng S, My DTT, Balasubramaniam A, Adi P, Hsieh MF, Herr DR, Huang CM. Electricity-producing Staphylococcus epidermidis counteracts Cutibacterium acnes. Sci Rep 2021; 11:12001. [PMID: 34099817 PMCID: PMC8184966 DOI: 10.1038/s41598-021-91398-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 05/10/2021] [Indexed: 12/19/2022] Open
Abstract
Staphylococcus epidermidis (S. epidermidis) ATCC 12228 was incubated with 2% polyethylene glycol (PEG)-8 Laurate to yield electricity which was measured by a voltage difference between electrodes. Production of electron was validated by a Ferrozine assay. The anti-Cutibacterium acnes (C. acnes) activity of electrogenic S. epidermidis was assessed in vitro and in vivo. The voltage change (~ 4.4 mV) reached a peak 60 min after pipetting S. epidermidis plus 2% PEG-8 Laurate onto anodes. The electricity produced by S. epidermidis caused significant growth attenuation and cell lysis of C. acnes. Intradermal injection of C. acnes and S. epidermidis plus PEG-8 Laurate into the mouse ear considerably suppressed the growth of C. acnes. This suppressive effect was noticeably reversed when cyclophilin A of S. epidermidis was inhibited, indicating the essential role of cyclophilin A in electricity production of S. epidermidis against C. acnes. In summary, we demonstrate for the first time that skin S. epidermidis, in the presence of PEG-8 Laurate, can mediate cyclophilin A to elicit an electrical current that has anti-C. acnes effects. Electricity generated by S. epidermidis may confer immediate innate immunity in acne lesions to rein in the overgrowth of C. acnes at the onset of acne vulgaris.
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Affiliation(s)
- Shinta Marito
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, Taiwan
| | - Sunita Keshari
- Department of Life Sciences, National Central University, Taoyuan, Taiwan
| | | | - Do Thi Tra My
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, Taiwan
| | - Arun Balasubramaniam
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, Taiwan
| | - Prakoso Adi
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, Taiwan
| | - Ming-Fa Hsieh
- Department of Biomedical Engineering, Chung Yuan Christian University, Taoyuan, Taiwan
| | | | - Chun-Ming Huang
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, Taiwan.
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14
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Vieira KCDO, Silva HRAD, Rocha IPM, Barboza E, Eller LKW. Foodborne pathogens in the omics era. Crit Rev Food Sci Nutr 2021; 62:6726-6741. [PMID: 33783282 DOI: 10.1080/10408398.2021.1905603] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Outbreaks and deaths related to Foodborne Diseases (FBD) occur constantly in the world, as a result of the consumption of contaminated foodstuffs with pathogens such as Listeria monocytogenes, Escherichia coli, Staphylococcus aureus, Salmonella spp, Clostridium spp. and Campylobacter spp. The purpose of this review is to discuss the main omic techniques applied in foodborne pathogen and to demonstrate their functionalities through the food chain and to guarantee the food safety. The main techniques presented are genomic, transcriptomic, secretomic, proteomic, and metabolomic, which together, in the field of food and nutrition, are known as "Foodomics." This review had highlighted the potential of omics to integrate variables that contribute to food safety and to enable us to understand their application on foodborne diseases. The appropriate use of these techniques had driven the definition of critical parameters to achieve successful results in the improvement of consumers health, costs and to obtain safe and high-quality products.
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Affiliation(s)
| | | | | | - Emmanuel Barboza
- Health Sciences Faculty, University of Western Sao Paulo, Presidente Prudente, Sao Paulo, Brazil
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15
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Pham MT, Yang JJ, Balasubramaniam A, Rahim AR, Adi P, Do TTM, Herr DR, Huang CM. Leuconostoc mesenteroides mediates an electrogenic pathway to attenuate the accumulation of abdominal fat mass induced by high fat diet. Sci Rep 2020; 10:21916. [PMID: 33318546 PMCID: PMC7736347 DOI: 10.1038/s41598-020-78835-9] [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: 07/17/2020] [Accepted: 11/27/2020] [Indexed: 11/26/2022] Open
Abstract
Although several electrogenic bacteria have been identified, the physiological effect of electricity generated by bacteria on host health remains elusive. We found that probiotic Leuconostoc mesenteroides (L. mesenteroides) can metabolize linoleic acid to yield electricity via an intracellular cyclophilin A-dependent pathway. Inhibition of cyclophilin A significantly abolished bacterial electricity and lowered the adhesion of L. mesenteroides to the human gut epithelial cell line. Butyrate from L. mesenteroides in the presence of linoleic acid were detectable and mediated free fatty acid receptor 2 (Ffar2) to reduce the lipid contents in differentiating 3T3-L1 adipocytes. Oral administration of L. mesenteroides plus linoleic acid remarkably reduced high-fat-diet (HFD)-induced formation of 4-hydroxy-2-nonenal (4-HNE), a reactive oxygen species (ROS) biomarker, and decreased abdominal fat mass in mice. The reduction of 4-HNE and abdominal fat mass was reversed when cyclophilin A inhibitor-pretreated bacteria were administered to mice. Our studies present a novel mechanism of reducing abdominal fat mass by electrogenic L. mesenteroides which may yield electrons to enhance colonization and sustain high amounts of butyrate to limit ROS during adipocyte differentiation.
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Affiliation(s)
- Minh Tan Pham
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, 32001, Taiwan
| | - John Jackson Yang
- Department of Life Sciences, National Central University, Taoyuan, Taiwan
| | - Arun Balasubramaniam
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, 32001, Taiwan
| | - Adelia Riezka Rahim
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, 32001, Taiwan
| | - Prakoso Adi
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, 32001, Taiwan
| | - Thi Tra My Do
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, 32001, Taiwan
| | - Deron Raymond Herr
- Department of Pharmacology, National University of Singapore, Singapore, Singapore
| | - Chun-Ming Huang
- Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, 32001, Taiwan.
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16
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Leseigneur C, Lê-Bury P, Pizarro-Cerdá J, Dussurget O. Emerging Evasion Mechanisms of Macrophage Defenses by Pathogenic Bacteria. Front Cell Infect Microbiol 2020; 10:577559. [PMID: 33102257 PMCID: PMC7545029 DOI: 10.3389/fcimb.2020.577559] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 08/26/2020] [Indexed: 12/22/2022] Open
Abstract
Macrophages participate to the first line of defense against infectious agents. Microbial pathogens evolved sophisticated mechanisms to escape macrophage killing. Here, we review recent discoveries and emerging concepts on bacterial molecular strategies to subvert macrophage immune responses. We focus on the expanding number of fascinating subversive tools developed by Listeria monocytogenes, Staphylococcus aureus, and pathogenic Yersinia spp., illustrating diversity and commonality in mechanisms used by microorganisms with different pathogenic lifestyles.
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Affiliation(s)
- Clarisse Leseigneur
- Unité de Recherche Yersinia, Institut Pasteur, Paris, France.,Université de Paris, Sorbonne Paris Cité, Paris, France
| | - Pierre Lê-Bury
- Unité de Recherche Yersinia, Institut Pasteur, Paris, France.,Université de Paris, Sorbonne Paris Cité, Paris, France
| | - Javier Pizarro-Cerdá
- Unité de Recherche Yersinia, Institut Pasteur, Paris, France.,National Reference Laboratory Plague & Other Yersiniosis, Institut Pasteur, Paris, France.,WHO Collaborative Research & Reference Centre for Yersinia, Institut Pasteur, Paris, France
| | - Olivier Dussurget
- Unité de Recherche Yersinia, Institut Pasteur, Paris, France.,Université de Paris, Sorbonne Paris Cité, Paris, France
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17
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Bianchi F, van den Bogaart G. Vacuolar escape of foodborne bacterial pathogens. J Cell Sci 2020; 134:134/5/jcs247221. [PMID: 32873733 DOI: 10.1242/jcs.247221] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The intracellular pathogens Listeria monocytogenes, Salmonella enterica, Shigella spp. and Staphylococcus aureus are major causes of foodborne illnesses. Following the ingestion of contaminated food or beverages, pathogens can invade epithelial cells, immune cells and other cell types. Pathogens survive and proliferate intracellularly via two main strategies. First, the pathogens can remain in membrane-bound vacuoles and tailor organellar trafficking to evade host-cell defenses and gain access to nutrients. Second, pathogens can rupture the vacuolar membrane and proliferate within the nutrient-rich cytosol of the host cell. Although this virulence strategy of vacuolar escape is well known for L. monocytogenes and Shigella spp., it has recently become clear that S. aureus and Salmonella spp. also gain access to the cytosol, and that this is important for their survival and growth. In this Review, we discuss the molecular mechanisms of how these intracellular pathogens rupture the vacuolar membrane by secreting a combination of proteins that lyse the membranes or that remodel the lipids of the vacuolar membrane, such as phospholipases. In addition, we also propose that oxidation of the vacuolar membrane also contributes to cytosolic pathogen escape. Understanding these escape mechanisms could aid in the identification of new therapeutic approaches to combat foodborne pathogens.
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Affiliation(s)
- Frans Bianchi
- Department of Molecular Immunology and Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9722GR Groningen, The Netherlands
| | - Geert van den Bogaart
- Department of Molecular Immunology and Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9722GR Groningen, The Netherlands .,Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 9625GA Nijmegen, The Netherlands
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18
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Roles of the Site 2 Protease Eep in Staphylococcus aureus. J Bacteriol 2020; 202:JB.00046-20. [PMID: 32457050 DOI: 10.1128/jb.00046-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 05/21/2020] [Indexed: 01/02/2023] Open
Abstract
In Enterococcus faecalis, the site 2 protease Eep generates sex pheromones, including cAM373. Intriguingly, in Staphylococcus aureus, a peptide similar to cAM373, named cAM373_SA, is produced from the camS gene. Here, we report that the staphylococcal Eep homolog is not only responsible for the production of cAM373_SA but also critical for staphylococcal virulence. As with other Eep proteins, the staphylococcal Eep protein has four transmembrane (TM) domains, with the predicted zinc metalloprotease active site (HEXXH) in the first TM domain. eep deletion reduced the cAM373_SA activity in the culture supernatant to the level of the camS deletion mutant. It also markedly decreased the cAM373 peptide peak in a high-performance liquid chromatography (HPLC) analysis. Proteomics analysis showed that Eep affects the production and/or the release of diverse proteins, including the signal peptidase subunit SpsB and the surface proteins SpA, SasG, and FnbA. eep deletion decreased the adherence of S. aureus to host epithelial cells; however, the adherence of the eep mutant was increased by overexpression of the surface proteins SpA, SasG, and FnbA. eep deletion reduced staphylococcal resistance to killing by human neutrophils as well as survival in a murine model of blood infection. The overexpression of the surface protein SpA in the eep mutant increased bacterial survival in the liver. Our study illustrates that in S. aureus, Eep not only generates cAM373_SA but also contributes to the survival of the bacterial pathogen in the host.IMPORTANCE The emergence of multidrug-resistant Staphylococcus aureus makes the treatment of staphylococcal infections much more difficult. S. aureus can acquire a drug resistance gene from other bacteria, such as Enterococcus faecalis Intriguingly, S. aureus produces a sex pheromone for the E. faecalis plasmid pAM373, raising the possibility that S. aureus actively promotes plasmid conjugation from E. faecalis In this study, we found that the staphylococcal Eep protein is responsible for sex pheromone processing and contributes to the survival of the bacteria in the host. These results will enhance future research on the drug resistance acquisition of S. aureus and can lead to the development of novel antivirulence drugs.
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19
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Cheng C, Sun J, Yu H, Ma T, Guan C, Zeng H, Zhang X, Chen Z, Song H. Listeriolysin O Pore-Forming Activity Is Required for ERK1/2 Phosphorylation During Listeria monocytogenes Infection. Front Immunol 2020; 11:1146. [PMID: 32582211 PMCID: PMC7283531 DOI: 10.3389/fimmu.2020.01146] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 05/11/2020] [Indexed: 12/18/2022] Open
Abstract
Listeriolysin O (LLO) is a cholesterol-dependent cytolysin that mediates escape of L. monocytogenes from phagosomes and enables the bacteria to grow within the host. LLO is a versatile tool allowing Listeria to trigger several cellular responses. In this study, rapid phosphorylation of ERK1/2 on Caco-2 cells caused by Listeria infection was demonstrated to be highly dependent on LLO activity. The effect could be strongly induced by adding purified recombinant LLO alone and could be inhibited by exogenous cholesterol. Lack of the PEST sequence, known to tightly control cytotoxicity of LLO, did not affect ERK1/2 activation. However, the recombinant non-cytolytic LLOT515AL516A, with mutations in the cholesterol-binding motif, was unable to trigger this response. Recombinant LLON478AV479A, which lacks most of the cytolytic activity, also failed to activate ERK1/2 phosphorylation, and this effect could be rescued when the protein concentration reached a cytolytic level. Infection with an LLO-deficient mutant (Δhly) or the mutant complementing LLOT515AL516A abrogated the capacity of the bacteria to activate ERK1/2. However, infection with the Δhly mutant complementing LLON478AV479A, which retained partial pore-forming ability and could grow intracellularly, was capable of triggering ERK1/2 phosphorylation. Collectively, these data suggest that ERK1/2 activation by L. monocytogenes depends on the permeabilization activity of LLO and more importantly correlates with the cholesterol-binding motif of LLO.
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Affiliation(s)
- Changyong Cheng
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
| | - Jing Sun
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
| | - Huifei Yu
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
| | - Tiantian Ma
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
| | - Chiyu Guan
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
| | - Huan Zeng
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
| | - Xian Zhang
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
| | - Zhongwei Chen
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
| | - Houhui Song
- Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China
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20
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Krypotou E, Scortti M, Grundström C, Oelker M, Luisi BF, Sauer-Eriksson AE, Vázquez-Boland J. Control of Bacterial Virulence through the Peptide Signature of the Habitat. Cell Rep 2020; 26:1815-1827.e5. [PMID: 30759392 PMCID: PMC6389498 DOI: 10.1016/j.celrep.2019.01.073] [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: 09/07/2018] [Revised: 11/09/2018] [Accepted: 01/17/2019] [Indexed: 12/20/2022] Open
Abstract
To optimize fitness, pathogens selectively activate their virulence program upon host entry. Here, we report that the facultative intracellular bacterium Listeria monocytogenes exploits exogenous oligopeptides, a ubiquitous organic N source, to sense the environment and control the activity of its virulence transcriptional activator, PrfA. Using a genetic screen in adsorbent-treated (PrfA-inducing) medium, we found that PrfA is functionally regulated by the balance between activating and inhibitory nutritional peptides scavenged via the Opp transport system. Activating peptides provide essential cysteine precursor for the PrfA-inducing cofactor glutathione (GSH). Non-cysteine-containing peptides cause promiscuous PrfA inhibition. Biophysical and co-crystallization studies reveal that peptides inhibit PrfA through steric blockade of the GSH binding site, a regulation mechanism directly linking bacterial virulence and metabolism. L. monocytogenes mutant analysis in macrophages and our functional data support a model in which changes in the balance of antagonistic Opp-imported oligopeptides promote PrfA induction intracellularly and PrfA repression outside the host. Listeria PrfA virulence regulation is controlled by antagonistic nutritional peptides Opp-imported peptides regulate PrfA upstream of the activating cofactor GSH PrfA is activated by peptides that provide essential cysteine for GSH biosynthesis Blockade of PrfA’s GSH binding site by peptides inhibits virulence gene activation
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Affiliation(s)
- Emilia Krypotou
- Microbial Pathogenesis Group, Infection Medicine, Edinburgh Medical School (Biomedical Sciences) and The Roslin Institute, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Mariela Scortti
- Microbial Pathogenesis Group, Infection Medicine, Edinburgh Medical School (Biomedical Sciences) and The Roslin Institute, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Christin Grundström
- Department of Chemistry and Umeå Centre for Microbial Research, Umeå University, 901 87 Umeå, Sweden
| | - Melanie Oelker
- Department of Chemistry and Umeå Centre for Microbial Research, Umeå University, 901 87 Umeå, Sweden
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | | | - José Vázquez-Boland
- Microbial Pathogenesis Group, Infection Medicine, Edinburgh Medical School (Biomedical Sciences) and The Roslin Institute, University of Edinburgh, Edinburgh EH16 4SB, UK.
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21
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Light SH, Méheust R, Ferrell JL, Cho J, Deng D, Agostoni M, Iavarone AT, Banfield JF, D’Orazio SEF, Portnoy DA. Extracellular electron transfer powers flavinylated extracellular reductases in Gram-positive bacteria. Proc Natl Acad Sci U S A 2019; 116:26892-26899. [PMID: 31818955 PMCID: PMC6936397 DOI: 10.1073/pnas.1915678116] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mineral-respiring bacteria use a process called extracellular electron transfer to route their respiratory electron transport chain to insoluble electron acceptors on the exterior of the cell. We recently characterized a flavin-based extracellular electron transfer system that is present in the foodborne pathogen Listeria monocytogenes, as well as many other Gram-positive bacteria, and which highlights a more generalized role for extracellular electron transfer in microbial metabolism. Here we identify a family of putative extracellular reductases that possess a conserved posttranslational flavinylation modification. Phylogenetic analyses suggest that divergent flavinylated extracellular reductase subfamilies possess distinct and often unidentified substrate specificities. We show that flavinylation of a member of the fumarate reductase subfamily allows this enzyme to receive electrons from the extracellular electron transfer system and support L. monocytogenes growth. We demonstrate that this represents a generalizable mechanism by finding that a L. monocytogenes strain engineered to express a flavinylated extracellular urocanate reductase uses urocanate by a related mechanism and to a similar effect. These studies thus identify an enzyme family that exploits a modular flavin-based electron transfer strategy to reduce distinct extracellular substrates and support a multifunctional view of the role of extracellular electron transfer activities in microbial physiology.
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Affiliation(s)
- Samuel H. Light
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720
| | - Raphaël Méheust
- Department of Earth and Planetary Science, University of California, Berkeley, CA 94720
- Innovative Genomics Institute, Berkeley, CA 94704
| | - Jessica L. Ferrell
- Department of Microbiology, Immunology & Molecular Genetics, University of Kentucky, Lexington, KY 40536-0298
| | - Jooyoung Cho
- Department of Microbiology, Immunology & Molecular Genetics, University of Kentucky, Lexington, KY 40536-0298
| | - David Deng
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720
| | - Marco Agostoni
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720
| | - Anthony T. Iavarone
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720
- QB3/Chemistry Mass Spectrometry Facility, University of California, Berkeley, CA 94720
| | - Jillian F. Banfield
- Department of Earth and Planetary Science, University of California, Berkeley, CA 94720
- Innovative Genomics Institute, Berkeley, CA 94704
| | - Sarah E. F. D’Orazio
- Department of Microbiology, Immunology & Molecular Genetics, University of Kentucky, Lexington, KY 40536-0298
| | - Daniel A. Portnoy
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720
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22
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Johansson J, Freitag NE. Regulation of Listeria monocytogenes Virulence. Microbiol Spectr 2019; 7:10.1128/microbiolspec.gpp3-0064-2019. [PMID: 31441398 PMCID: PMC10957223 DOI: 10.1128/microbiolspec.gpp3-0064-2019] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Indexed: 02/07/2023] Open
Abstract
Whereas obligate human and animal bacterial pathogens may be able to depend upon the warmth and relative stability of their chosen replication niche, environmental bacteria such as Listeria monocytogenes that harbor the ability to replicate both within animal cells and in the outside environment must maintain the capability to manage life under a variety of disparate conditions. Bacterial life in the outside environment requires adaptation to wide ranges of temperature, available nutrients, and physical stresses such as changes in pH and osmolarity as well as desiccation. Following ingestion by a susceptible animal host, the bacterium must adapt to similar changes during transit through the gastrointestinal tract and overcome a variety of barriers associated with host innate immune responses. Rapid alteration of patterns of gene expression and protein synthesis represent one strategy for quickly adapting to a dynamic host landscape. Here, we provide an overview of the impressive variety of strategies employed by the soil-dwelling, foodborne, mammalian pathogen L. monocytogenes to straddle diverse environments and optimize bacterial fitness both inside and outside host cells.
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Affiliation(s)
- Jörgen Johansson
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS) and Umeå Centre for Microbial Research (UCMR), Umeå University, 90187 Umeå, Sweden
| | - Nancy E Freitag
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago IL
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Hughes A, Wilson S, Dodson EJ, Turkenburg JP, Wilkinson AJ. Crystal structure of the putative peptide-binding protein AppA from Clostridium difficile. Acta Crystallogr F Struct Biol Commun 2019; 75:246-253. [PMID: 30950825 PMCID: PMC6450515 DOI: 10.1107/s2053230x1900178x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 01/30/2019] [Indexed: 12/21/2022] Open
Abstract
Peptides play an important signalling role in Bacillus subtilis, where their uptake by one of two ABC-type oligopeptide transporters, Opp and App, is required for efficient sporulation. Homologues of these transporters in Clostridium difficile have been characterized, but their role, and hence that of peptides, in regulating sporulation in this organism is less clear. Here, the oligopeptide-binding receptor proteins for these transporters, CdAppA and CdOppA, have been purified and partially characterized, and the crystal structure of CdAppA has been determined in an open unliganded form. Peptide binding to either protein could not be observed in Thermofluor assays with a set of ten peptides of varying lengths and compositions. Re-examination of the protein sequences together with structure comparisons prompts the proposal that CdAppA is not a versatile peptide-binding protein but instead may bind a restricted set of peptides. Meanwhile, CdOppA is likely to be the receptor protein for a nickel-uptake system.
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Affiliation(s)
- Adam Hughes
- Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, England
| | - Samuel Wilson
- Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, England
| | - Eleanor J. Dodson
- Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, England
| | - Johan P. Turkenburg
- Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, England
| | - Anthony J. Wilkinson
- Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, England
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24
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Abstract
The Gram-positive pathogen Listeria monocytogenes is able to promote its entry into a diverse range of mammalian host cells by triggering plasma membrane remodeling, leading to bacterial engulfment. Upon cell invasion, L. monocytogenes disrupts its internalization vacuole and translocates to the cytoplasm, where bacterial replication takes place. Subsequently, L. monocytogenes uses an actin-based motility system that allows bacterial cytoplasmic movement and cell-to-cell spread. L. monocytogenes therefore subverts host cell receptors, organelles and the cytoskeleton at different infection steps, manipulating diverse cellular functions that include ion transport, membrane trafficking, post-translational modifications, phosphoinositide production, innate immune responses as well as gene expression and DNA stability.
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25
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Light SH, Su L, Rivera-Lugo R, Cornejo JA, Louie A, Iavarone AT, Ajo-Franklin CM, Portnoy DA. A flavin-based extracellular electron transfer mechanism in diverse Gram-positive bacteria. Nature 2018; 562:140-144. [PMID: 30209391 PMCID: PMC6221200 DOI: 10.1038/s41586-018-0498-z] [Citation(s) in RCA: 312] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 08/03/2018] [Indexed: 11/10/2022]
Abstract
Extracellular electron transfer (EET) describes microbial bioelectrochemical processes in which electrons are transferred from the cytosol to the exterior of the cell1. Mineral-respiring bacteria use elaborate haem-based electron transfer mechanisms2-4 but the existence and mechanistic basis of other EETs remain largely unknown. Here we show that the food-borne pathogen Listeria monocytogenes uses a distinctive flavin-based EET mechanism to deliver electrons to iron or an electrode. By performing a forward genetic screen to identify L. monocytogenes mutants with diminished extracellular ferric iron reductase activity, we identified an eight-gene locus that is responsible for EET. This locus encodes a specialized NADH dehydrogenase that segregates EET from aerobic respiration by channelling electrons to a discrete membrane-localized quinone pool. Other proteins facilitate the assembly of an abundant extracellular flavoprotein that, in conjunction with free-molecule flavin shuttles, mediates electron transfer to extracellular acceptors. This system thus establishes a simple electron conduit that is compatible with the single-membrane structure of the Gram-positive cell. Activation of EET supports growth on non-fermentable carbon sources, and an EET mutant exhibited a competitive defect within the mouse gastrointestinal tract. Orthologues of the genes responsible for EET are present in hundreds of species across the Firmicutes phylum, including multiple pathogens and commensal members of the intestinal microbiota, and correlate with EET activity in assayed strains. These findings suggest a greater prevalence of EET-based growth capabilities and establish a previously underappreciated relevance for electrogenic bacteria across diverse environments, including host-associated microbial communities and infectious disease.
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Affiliation(s)
- Samuel H Light
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Lin Su
- Molecular Foundry, Molecular Biophysics and Integrated Bioimaging, and Synthetic Biology Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210018, China
| | - Rafael Rivera-Lugo
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Jose A Cornejo
- Molecular Foundry, Molecular Biophysics and Integrated Bioimaging, and Synthetic Biology Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Alexander Louie
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Anthony T Iavarone
- QB3/Chemistry Mass Spectrometry Facility, University of California, Berkeley, Berkeley, CA, USA
| | - Caroline M Ajo-Franklin
- Molecular Foundry, Molecular Biophysics and Integrated Bioimaging, and Synthetic Biology Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Daniel A Portnoy
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
- Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA.
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26
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Brown SP, Blackwell HE, Hammer BK. The State of the Union Is Strong: a Review of ASM's 6th Conference on Cell-Cell Communication in Bacteria. J Bacteriol 2018; 200:e00291-18. [PMID: 29760210 PMCID: PMC6018360 DOI: 10.1128/jb.00291-18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 6th American Society for Microbiology Conference on Cell-Cell Communication in Bacteria convened from 16 to 19 October 2017 in Athens, GA. In this minireview, we highlight some of the research presented at that meeting that addresses central questions emerging in the field, including the following questions. How are cell-cell communication circuits designed to generate responses? Where are bacteria communicating? Finally, why are bacteria engaging in such behaviors?
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Affiliation(s)
- Sam P Brown
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Helen E Blackwell
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Brian K Hammer
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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27
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A Quorum Sensing-Regulated Protein Binds Cell Wall Components and Enhances Lysozyme Resistance in Streptococcus pyogenes. J Bacteriol 2018; 200:JB.00701-17. [PMID: 29555699 DOI: 10.1128/jb.00701-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 03/10/2018] [Indexed: 12/28/2022] Open
Abstract
The Rgg2/3 quorum sensing (QS) system is conserved among all sequenced isolates of group A Streptococcus (GAS; Streptococcus pyogenes). The molecular architecture of the system consists of a transcriptional activator (Rgg2) and a transcriptional repressor (Rgg3) under the control of autoinducing peptide pheromones (SHP2 and SHP3). Activation of the Rgg2/3 pathway leads to increases in biofilm formation and resistance to the bactericidal effects of the host factor lysozyme. In this work, we show that deletion of a small gene, spy49_0414c, abolished both phenotypes in response to pheromone signaling. The gene encodes a small, positively charged, secreted protein, referred to as StcA. Analysis of recombinant StcA showed that it can directly interact with GAS cell wall preparations containing phosphodiester-linked carbohydrate polymers but not with preparations devoid of them. Immunofluorescence microscopy detected antibody against StcA bound to the surface of paraformaldehyde-fixed wild-type cells. Expression of StcA in bacterial culture induced a shift in the electrostatic potential of the bacterial cell surface, which became more positively charged. These results suggest that StcA promotes phenotypes by way of ionic interactions with the GAS cell wall, most likely with negatively charged cell wall-associated polysaccharides.IMPORTANCE This study focuses on a small protein, StcA, that is expressed and secreted under induction of Rgg2/3 QS, ionically associating with negatively charged domains on the cell surface. These data present a novel mechanism of resistance to the host factor lysozyme by GAS and have implications in the relevance of this circuit in the interaction between the bacterium and the human host that is mediated by the bacterial cell surface.
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Radoshevich L, Cossart P. Listeria monocytogenes: towards a complete picture of its physiology and pathogenesis. Nat Rev Microbiol 2018; 16:32-46. [PMID: 29176582 DOI: 10.1038/nrmicro.2017.126] [Citation(s) in RCA: 469] [Impact Index Per Article: 78.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Listeria monocytogenes is a food-borne pathogen responsible for a disease called listeriosis, which is potentially lethal in immunocompromised individuals. This bacterium, first used as a model to study cell-mediated immunity, has emerged over the past 20 years as a paradigm in infection biology, cell biology and fundamental microbiology. In this Review, we highlight recent advances in the understanding of human listeriosis and L. monocytogenes biology. We describe unsuspected modes of hijacking host cell biology, ranging from changes in organelle morphology to direct effects on host transcription via a new class of bacterial effectors called nucleomodulins. We then discuss advances in understanding infection in vivo, including the discovery of tissue-specific virulence factors and the 'arms race' among bacteria competing for a niche in the microbiota. Finally, we describe the complexity of bacterial regulation and physiology, incorporating new insights into the mechanisms of action of a series of riboregulators that are critical for efficient metabolic regulation, antibiotic resistance and interspecies competition.
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Affiliation(s)
- Lilliana Radoshevich
- Institut Pasteur, Unité des Interactions Bactéries-Cellules, Département de Biologie Cellulaire et Infection, F-75015 Paris, France
- Inserm, U604, F-75015 Paris, France
- French National Institute for Agricultural Research (INRA), Unité sous-contrat 2020, F-75015 Paris, France
- Department of Microbiology and Immunology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA
| | - Pascale Cossart
- Institut Pasteur, Unité des Interactions Bactéries-Cellules, Département de Biologie Cellulaire et Infection, F-75015 Paris, France
- Inserm, U604, F-75015 Paris, France
- French National Institute for Agricultural Research (INRA), Unité sous-contrat 2020, F-75015 Paris, France
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Controlled Activity of the Salmonella Invasion-Associated Injectisome Reveals Its Intracellular Role in the Cytosolic Population. mBio 2017; 8:mBio.01931-17. [PMID: 29208746 PMCID: PMC5717391 DOI: 10.1128/mbio.01931-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Salmonella invasion-associated type III secretion system (T3SS1) is an essential virulence factor required for entry into nonphagocytic cells and consequent uptake into a Salmonella-containing vacuole (SCV). While Salmonella is typically regarded as a vacuolar pathogen, a subset of bacteria escape from the SCV in epithelial cells and eventually hyperreplicate in the cytosol. T3SS1 is downregulated following bacterial entry into mammalian cells, but cytosolic Salmonella cells are T3SS1 induced, suggesting prolonged or resurgent activity of T3SS1 in this population. In order to investigate the postinternalization contributions of T3SS1 to the Salmonella infectious cycle in epithelial cells, we bypassed its requirement for bacterial entry by tagging the T3SS1-energizing ATPase InvC at the C terminus with peptides that are recognized by bacterial tail-specific proteases. This caused a dramatic increase in InvC turnover which rendered even assembled injectisomes inactive. Bacterial strains conditionally expressing these unstable InvC variants were proficient for invasion but underwent rapid and sustained intracellular inactivation of T3SS1 activity when InvC expression ceased. This allowed us to directly implicate T3SS1 activity in cytosolic colonization and bacterial egress. We subsequently identified two T3SS1-delivered effectors, SopB and SipA, that are required for efficient colonization of the epithelial cell cytosol. Overall, our findings support a multifaceted, postinvasion role for T3SS1 and its effectors in defining the cytosolic population of intracellular Salmonella. A needle-like apparatus, the type III secretion system (T3SS) injectisome, is absolutely required for Salmonella enterica to enter epithelial cells; this requirement has hampered the analysis of its postentry contributions. To identify T3SS1-dependent intracellular activities, in this study we overcame this limitation by developing a conditional inactivation in the T3SS whereby T3SS activity is chemically induced during culture in liquid broth, permitting bacterial entry into epithelial cells, but is quickly and perpetually inactivated in the absence of inducer. In this sense, the mutant acts like wild-type bacteria when extracellular and as a T3SS mutant once it enters a host cell. This “conditional” mutant allowed us to directly link activity of this T3SS with nascent vacuole lysis, cytosolic proliferation, and cellular egress, demonstrating that the invasion-associated T3SS also contributes to essential intracellular stages of the S. enterica infectious cycle.
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30
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Neiditch MB, Capodagli GC, Prehna G, Federle MJ. Genetic and Structural Analyses of RRNPP Intercellular Peptide Signaling of Gram-Positive Bacteria. Annu Rev Genet 2017; 51:311-333. [PMID: 28876981 PMCID: PMC6588834 DOI: 10.1146/annurev-genet-120116-023507] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Bacteria use diffusible chemical messengers, termed pheromones, to coordinate gene expression and behavior among cells in a community by a process known as quorum sensing. Pheromones of many gram-positive bacteria, such as Bacillus and Streptococcus, are small, linear peptides secreted from cells and subsequently detected by sensory receptors such as those belonging to the large family of RRNPP proteins. These proteins are cytoplasmic pheromone receptors sharing a structurally similar pheromone-binding domain that functions allosterically to regulate receptor activity. X-ray crystal structures of prototypical RRNPP members have provided atomic-level insights into their mechanism and regulation by pheromones. This review provides an overview of RRNPP prototype signaling; describes the structure-function of this protein family, which is spread widely among gram-positive bacteria; and suggests approaches to target RRNPP systems in order to manipulate beneficial and harmful bacterial behaviors.
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Affiliation(s)
- Matthew B Neiditch
- Department of Microbiology, Biochemistry, and Molecular Genetics, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey 07103, USA; ,
| | - Glenn C Capodagli
- Department of Microbiology, Biochemistry, and Molecular Genetics, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey 07103, USA; ,
| | - Gerd Prehna
- Center for Structural Biology, Research Resources Center and Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois 60607, USA;
| | - Michael J Federle
- Department of Medicinal Chemistry and Pharmacognosy and Center for Biomolecular Sciences, University of Illinois at Chicago, Chicago, Illinois 60607, USA;
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31
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Cheng C, Jiang L, Ma T, Wang H, Han X, Sun J, Yang Y, Chen Z, Yu H, Hang Y, Liu F, Wang B, Fang W, Huang H, Fang C, Cai C, Freitag N, Song H. Carboxyl-Terminal Residues N478 and V479 Required for the Cytolytic Activity of Listeriolysin O Play a Critical Role in Listeria monocytogenes Pathogenicity. Front Immunol 2017; 8:1439. [PMID: 29163512 PMCID: PMC5671954 DOI: 10.3389/fimmu.2017.01439] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 10/17/2017] [Indexed: 11/24/2022] Open
Abstract
Listeria monocytogenes is a facultative intracellular pathogen that secretes the cytolysin listeriolysin O (LLO), which enables the bacteria to cross the phagosomal membrane. L. monocytogenes regulates LLO activity in the phagosome and minimizes its activity in the host cytosol. Mutants that fail to compartmentalize LLO activity are cytotoxic and have attenuated virulence. Here, we showed that residues N478 and V479 of LLO are required for LLO hemolytic activity and bacterial virulence. A single N478A mutation (LLON478A) significantly increased the hemolytic activity of LLO at a neutral pH, while no difference was observed at the optimum acidic pH, compared with wild-type LLO. Conversely, the mutant LLOV479A exhibited lower hemolytic activity at the acidic pH, but not at the neutral pH. The double mutant LLON478AV479A showed a greater decrease in hemolytic activity at both the acidic and neutral pHs. Interestingly, strains producing LLON478A or LLOV479A lysed erythrocytes similarly to the wild-type strain. Surprisingly, bacteria-secreting LLON478AV479A had barely detectable hemolytic activity, but exhibited host cell cytotoxicity, escaped from the phagosome, grew intracellularly, and spread cell-to-cell with the same efficiency as the wild-type strain, but were highly attenuated in virulence in mice. These data demonstrate that these two residues are required for LLO hemolytic activity and pathogenicity in mice, but not for escape from the phagosome and cell-to-cell spreading. The finding that the nearly non-hemolytic LLON478AV479A mutant grew intracellularly indicates that mutagenesis of a virulence determinant is a novel approach for the development of live vaccine strains.
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Affiliation(s)
- Changyong Cheng
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Li Jiang
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Tiantian Ma
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Hang Wang
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Xiao Han
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Jing Sun
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Yongchun Yang
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Zhongwei Chen
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Huifei Yu
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Yi Hang
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Fengdan Liu
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Bosen Wang
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
| | - Weihuan Fang
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China.,Zhejiang University Institute of Preventive Veterinary Medicine, Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, China
| | - Huarong Huang
- College of Biological and Environmental Science, Institute of Developmental and Regenerative Biology, Hangzhou Normal University, Hangzhou, China
| | - Chun Fang
- College of Animal Science, Yangtze University, Hubei, China
| | - Chang Cai
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China.,School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, Australia
| | - Nancy Freitag
- Department of Microbiology and Immunology, University of Illinois at Chicago College of Medicine, Chicago, IL, United States
| | - Houhui Song
- College of Animal Science and Technology of Zhejiang A&F University, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Lin'an, China
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32
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Sternkopf Lillebæk EM, Lambert Nielsen S, Scheel Thomasen R, Færgeman NJ, Kallipolitis BH. Antimicrobial medium- and long-chain free fatty acids prevent PrfA-dependent activation of virulence genes in Listeria monocytogenes. Res Microbiol 2017; 168:547-557. [DOI: 10.1016/j.resmic.2017.03.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/06/2017] [Accepted: 03/13/2017] [Indexed: 12/11/2022]
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33
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Cheng C, Dong Z, Han X, Wang H, Jiang L, Sun J, Yang Y, Ma T, Shao C, Wang X, Chen Z, Fang W, Freitag NE, Huang H, Song H. Thioredoxin A Is Essential for Motility and Contributes to Host Infection of Listeria monocytogenes via Redox Interactions. Front Cell Infect Microbiol 2017; 7:287. [PMID: 28702378 PMCID: PMC5487381 DOI: 10.3389/fcimb.2017.00287] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 06/12/2017] [Indexed: 12/17/2022] Open
Abstract
Microbes employ the thioredoxin system to defend against oxidative stress and ensure correct disulfide bonding to maintain protein function. Listeria monocytogenes has been shown to encode a putative thioredoxin, TrxA, but its biological roles and underlying mechanisms remain unknown. Here, we showed that expression of L. monocytogenes TrxA is significantly induced in bacteria treated with the thiol-specific oxidizing agent, diamide. Deletion of trxA markedly compromised tolerance of the pathogen to diamide, and mainly impaired early stages of infection in human intestinal epithelial Caco-2 cells. In addition, most trxA mutant bacteria were not associated with polymerized actin, and the rare bacteria that were associated with polymerized actin displayed very short tails or clouds during infection. Deletion or constitutive overexpression of TrxA, which was regulated by SigH, severely attenuated the virulence of the pathogen. Transcriptome analysis of L. monocytogenes revealed over 270 genes that were differentially transcribed in the ΔtrxA mutant compared to the wild-type, especially for the virulence-associated genes plcA, mpl, hly, actA, and plcB. Particularly, deletion of TrxA completely reduced LLO expression, and thereby led to a thoroughly impaired hemolytic activity. Expression of these virulence factors are positively regulated by the master regulator PrfA that was found here to use TrxA to maintain its reduced forms for activation. Interestingly, the trxA deletion mutant completely lacked flagella and was non-motile. We further confirmed that this deficiency is attributable to TrxA in maintaining the reduced intracellular monomer status of MogR, the key regulator for flagellar formation, to ensure correct dimerization. In summary, we demonstrated for the first time that L. monocytogenes thioredoxin A as a vital cellular reductase is essential for maintaining a highly reducing environment in the bacterial cytosol, which provides a favorable condition for protein folding and activation, and therefore contributes to bacterial virulence and motility.
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Affiliation(s)
- Changyong Cheng
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Zhimei Dong
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Xiao Han
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Hang Wang
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Li Jiang
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Jing Sun
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Yongchun Yang
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Tiantian Ma
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Chunyan Shao
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Xiaodu Wang
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Zhongwei Chen
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
| | - Weihuan Fang
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China.,Zhejiang University Institute of Preventive Veterinary Medicine and Zhejiang Provincial Key Laboratory of Preventive Veterinary MedicineHangzhou, China
| | - Nancy E Freitag
- Department of Microbiology and Immunology, University of Illinois at ChicagoChicago, IL, United States
| | - Huarong Huang
- Institute of Developmental and Regenerative Biology, College of Biological and Environmental Science, Hangzhou Normal UniversityZhejiang, China
| | - Houhui Song
- China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection and Internet Technology, College of Animal Science and Technology of Zhejiang A&F UniversityLin'an, China
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Lebreton A, Stavru F, Brisse S, Cossart P. 1926-2016: 90 Years of listeriology. Microbes Infect 2016; 18:711-723. [PMID: 27876526 DOI: 10.1016/j.micinf.2016.10.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 10/26/2016] [Indexed: 01/28/2023]
Abstract
ISOPOL - for "International Symposium on Problems of Listeria and Listeriosis" - meetings gather every three years since 1957 participants from all over the world and allow exchange and update on a wide array of topics concerning Listeria and listeriosis, ranging from epidemiology, diagnostic and typing methods, to genomics, post-genomics, fundamental microbiology, cell biology and pathogenesis. The XIXth ISOPOL meeting took place in Paris from June 14th to 17th, 2016 at Institut Pasteur. We provide here a report of the talks that were given during the meeting, which represents an up-to-date overview of ongoing research on this important pathogen and biological model.
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Affiliation(s)
- Alice Lebreton
- École normale supérieure, PSL Research University, CNRS, Inserm, Institut de Biologie de l'École Normale Supérieure (IBENS), Équipe Infection et Devenir de l'ARN, 75005 Paris, France; INRA, IBENS, 75005 Paris, France
| | - Fabrizia Stavru
- Institut Pasteur, Unité des Interactions Bactéries-Cellules, 75015 Paris, France; Inserm, U604, 75015 Paris, France; INRA, USC2020, 75015 Paris, France; CNRS, SNC5101, Paris, France
| | - Sylvain Brisse
- Institut Pasteur, Molecular Prevention and Therapy of Human Diseases, 75724 Paris, France; Institut Pasteur, Microbial Evolutionary Genomics, 75724 Paris, France; CNRS, UMR 3525, Paris, France
| | - Pascale Cossart
- Institut Pasteur, Unité des Interactions Bactéries-Cellules, 75015 Paris, France; Inserm, U604, 75015 Paris, France; INRA, USC2020, 75015 Paris, France.
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Xayarath B, Freitag NE. When being alone is enough: noncanonical functions of canonical bacterial quorum-sensing systems. Future Microbiol 2016; 11:1447-1459. [PMID: 27750441 DOI: 10.2217/fmb-2016-0066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A number of bacterial pathogens are capable of detecting the presence of other bacteria located within their surrounding niche through a process of bacterial signaling and cell-to-cell communication commonly referred to as quorum sensing (QS). QS systems are commonly now described in the context of collective behaviors exhibited by groups of bacteria coordinating diverse arrays of physiological functions to enhance survival of the community. However, QS systems have also been implicated in a variety of processes distinct from the measure of bacterial cell density. This review will highlight noncanonical adaptations of canonical QS systems that have evolved to enable bacteria to detect nonself individuals within a population or to detect occupation of confined spaces.
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Affiliation(s)
- Bobbi Xayarath
- Department of Microbiology & Immunology, University of Illinois at Chicago, Chicago, IL 60612-7344, USA
| | - Nancy E Freitag
- Department of Microbiology & Immunology, University of Illinois at Chicago, Chicago, IL 60612-7344, USA
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An In Vivo Selection Identifies Listeria monocytogenes Genes Required to Sense the Intracellular Environment and Activate Virulence Factor Expression. PLoS Pathog 2016; 12:e1005741. [PMID: 27414028 PMCID: PMC4945081 DOI: 10.1371/journal.ppat.1005741] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 06/14/2016] [Indexed: 11/19/2022] Open
Abstract
Listeria monocytogenes is an environmental saprophyte and facultative intracellular bacterial pathogen with a well-defined life-cycle that involves escape from a phagosome, rapid cytosolic growth, and ActA-dependent cell-to-cell spread, all of which are dependent on the master transcriptional regulator PrfA. The environmental cues that lead to temporal and spatial control of L. monocytogenes virulence gene expression are poorly understood. In this study, we took advantage of the robust up-regulation of ActA that occurs intracellularly and expressed Cre recombinase from the actA promoter and 5' untranslated region in a strain in which loxP sites flanked essential genes, so that activation of actA led to bacterial death. Upon screening for transposon mutants that survived intracellularly, six genes were identified as necessary for ActA expression. Strikingly, most of the genes, including gshF, spxA1, yjbH, and ohrA, are predicted to play important roles in bacterial redox regulation. The mutants identified in the genetic selection fell into three broad categories: (1) those that failed to reach the cytosolic compartment; (2) mutants that entered the cytosol, but failed to activate the master virulence regulator PrfA; and (3) mutants that entered the cytosol and activated transcription of actA, but failed to synthesize it. The identification of mutants defective in vacuolar escape suggests that up-regulation of ActA occurs in the host cytosol and not the vacuole. Moreover, these results provide evidence for two non-redundant cytosolic cues; the first results in allosteric activation of PrfA via increased glutathione levels and transcriptional activation of actA while the second results in translational activation of actA and requires yjbH. Although the precise host cues have not yet been identified, we suggest that intracellular redox stress occurs as a consequence of both host and pathogen remodeling their metabolism upon infection.
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