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Muñoz-Echeverri LM, Benavides-López S, Geiger O, Trujillo-Roldán MA, Valdez-Cruz NA. Bacterial extracellular vesicles: biotechnological perspective for enhanced productivity. World J Microbiol Biotechnol 2024; 40:174. [PMID: 38642254 PMCID: PMC11032300 DOI: 10.1007/s11274-024-03963-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 03/19/2024] [Indexed: 04/22/2024]
Abstract
Bacterial extracellular vesicles (BEVs) are non-replicative nanostructures released by Gram-negative and Gram-positive bacteria as a survival mechanism and inter- and intraspecific communication mechanism. Due to BEVs physical, biochemical, and biofunctional characteristics, there is interest in producing and using them in developing new therapeutics, vaccines, or delivery systems. However, BEV release is typically low, limiting their application. Here, we provide a biotechnological perspective to enhance BEV production, highlighting current strategies. The strategies include the production of hypervesiculating strains through gene modification, bacteria culture under stress conditions, and artificial vesicles production. We discussed the effect of these production strategies on BEVs types, morphology, composition, and activity. Furthermore, we summarized general aspects of BEV biogenesis, functional capabilities, and applications, framing their current importance and the need to produce them in abundance. This review will expand the knowledge about the range of strategies associated with BEV bioprocesses to increase their productivity and extend their application possibilities.
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Affiliation(s)
- Laura M Muñoz-Echeverri
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México AP. 70228, Ciudad de México, C.P. 04510, México
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Unidad de Posgrado, Edificio D, 1° Piso, Circuito de Posgrados, Ciudad Universitaria, Coyoacán CDMX, C.P. 04510, México
| | - Santiago Benavides-López
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México AP. 70228, Ciudad de México, C.P. 04510, México
- Posgrado en Ciencias Biomédicas, Universidad Nacional Autónoma de México, Unidad de Posgrado, Edificio B, 1° Piso, Circuito de Posgrados, Ciudad Universitaria, Coyoacán CDMX, C.P. 04510, México
| | - Otto Geiger
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Av. Universidad s/n, Cuernavaca, Morelos, CP 62210, México
| | - Mauricio A Trujillo-Roldán
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México AP. 70228, Ciudad de México, C.P. 04510, México
- Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Km 107 Carretera, Tijuana-Ensenada, Baja California, 22860, México
| | - Norma A Valdez-Cruz
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México AP. 70228, Ciudad de México, C.P. 04510, México.
- Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Km 107 Carretera, Tijuana-Ensenada, Baja California, 22860, México.
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2
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Levy JG, Oh J, Mendoza Herrera A, Parida A, Lao L, Starkey J, Yuan P, Kan CC, Tamborindeguy C. A ' Candidatus Liberibacter solanacearum' Haplotype B-Specific Family of Candidate Bacterial Effectors. PHYTOPATHOLOGY 2023; 113:1708-1715. [PMID: 37665323 DOI: 10.1094/phyto-11-22-0438-v] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
'Candidatus Liberibacter solanacearum' (Lso) is a phloem-limited pathogen associated with devastating diseases in members of the Solanaceae and Apiaceae and vectored by several psyllid species. Different Lso haplotypes have been identified, and LsoA and LsoB are responsible for diseases in Solanaceae crops. Our efforts are aimed at identifying pathogenicity factors used by this bacterium to thrive in different hosts. Bacterial secreted proteins can play a role in host colonization or the manipulation of the host immune responses; these proteins are called effectors. In this study, we identified six LsoB-specific proteins with a conserved secretion motif as well as a conserved N-terminal domain in the mature protein. These proteins had different expression and secretion patterns but a similar subcellular localization in Nicotiana benthamiana leaves, suggesting that they play different roles regardless of their conserved secretion motif. One of these proteins, CKC_04425, was expressed at high levels in the insect vector and the host plant, indicating that it could play a role in both the plant and insect hosts, whereas the others were mainly expressed in the plant. One protein, CKC_05701, was able to efficiently suppress programmed cell death and reactive oxygen species production, suggesting that it may have a virulence role in LsoB-specific pathogenesis.
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Affiliation(s)
- Julien G Levy
- Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843
| | - Junepyo Oh
- Department of Entomology, Texas A&M University, College Station, TX 77843
| | | | - Adwaita Parida
- Department of Entomology, Texas A&M University, College Station, TX 77843
| | - Loi Lao
- Department of Entomology, Texas A&M University, College Station, TX 77843
| | - Jesse Starkey
- Department of Entomology, Texas A&M University, College Station, TX 77843
| | - Peiguo Yuan
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843
| | - Chia-Cheng Kan
- Department of Entomology, Texas A&M University, College Station, TX 77843
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3
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Sperandeo P, Martorana AM, Zaccaria M, Polissi A. Targeting the LPS export pathway for the development of novel therapeutics. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119406. [PMID: 36473551 DOI: 10.1016/j.bbamcr.2022.119406] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 10/14/2022] [Accepted: 11/01/2022] [Indexed: 12/12/2022]
Abstract
The rapid rise of multi-resistant bacteria is a global health threat. This is especially serious for Gram-negative bacteria in which the impermeable outer membrane (OM) acts as a shield against antibiotics. The development of new drugs with novel modes of actions to combat multi-drug resistant pathogens requires the selection of suitable processes to be targeted. The LPS export pathway is an excellent under exploited target for drug development. Indeed, LPS is the major determinant of the OM permeability barrier, and its biogenetic pathway is conserved in most Gram-negatives. Here we describe efforts to identify inhibitors of the multiprotein Lpt system that transports LPS to the cell surface. Despite none of these molecules has been approved for clinical use, they may represent valuable compounds for optimization. Finally, the recent discovery of a link between inhibition of LPS biogenesis and changes in peptidoglycan structure uncovers additional targets to develop novel therapeutic strategies.
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Affiliation(s)
- Paola Sperandeo
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Alessandra M Martorana
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Marta Zaccaria
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Alessandra Polissi
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy.
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4
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Horng YT, Dewi Panjaitan NS, Chang HJ, Wei YH, Chien CC, Yang HC, Chang HY, Soo PC. A protein containing the DUF1471 domain regulates biofilm formation and capsule production in Klebsiella pneumoniae. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2022; 55:1246-1254. [PMID: 34924339 DOI: 10.1016/j.jmii.2021.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/08/2021] [Accepted: 11/20/2021] [Indexed: 12/27/2022]
Abstract
BACKGROUND/PURPOSE Biofilms formed by Klebsiella pneumoniae on medical devices increase infection risk. Fimbriae and capsule polysaccharides (CPSs) are important factors involved in biofilm formation. KP1_4563 in K. pneumoniae NTUH-K2044, a small protein containing the DUF1471 domain, was reported to inhibit type 3 fimbriae function. In this study, we aimed to determine whether the KP1_4563 homolog is conserved in each K. pneumoniae isolate and what role it has in Klebsiella biofilms. METHODS The genomes of K. pneumoniae NTUH-K2044, CG43, MGH78578, KPPR1 and STU1 were compared. The KP1_4563 homolog in K. pneumoniae STU1 was named orfX. Biofilms of wild-type and orfX mutant strains from K. pneumoniae STU1 and one clinical isolate, 83535, were quantified. Transcription levels of the type 3 fimbrial genes, mrkA and mrkH, were investigated by RT-qPCR. MrkA of the wild-type and orfX mutant were observed by Western blotting. The morphology of bacterial cells was observed by transmission electron microscopy (TEM). Bacterial CPSs were quantified. RESULTS The gene and upstream region of orfX were conserved among the five K. pneumoniae isolates. Deletion of orfX enhanced Klebsiella biofilm formation. However, the amount of mRNA from mrkA and mrkH and the level of MrkA protein were not different between the wild type and orfX mutant. In contrast, the amount of CPS in orfX mutants was increased, compared to their parental strains, STU1 and 83535. CONCLUSION The role of orfX is speculated to be conserved in most K. pneumoniae isolates. OrfX negatively controlled biofilm formation by reducing CPS, not type 3 fimbriae, production.
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Affiliation(s)
- Yu-Tze Horng
- Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien, Taiwan, R.O.C
| | - Novaria Sari Dewi Panjaitan
- Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien, Taiwan, R.O.C
| | - Hui-Ju Chang
- Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien, Taiwan, R.O.C
| | - Yu-Hong Wei
- Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Taoyuan, Taiwan, R.O.C
| | - Chih-Ching Chien
- Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Taoyuan, Taiwan, R.O.C
| | - Hung-Chi Yang
- Department of Medical Laboratory Science and Biotechnology, Yuanpei University of Medical Technology, Hsinchu, Taiwan, R.O.C
| | - Heng-Yuan Chang
- School of Post-Baccalaureate Chinese Medicine, College of Medicine, Tzu Chi University, Hualien, Taiwan, R.O.C
| | - Po-Chi Soo
- Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien, Taiwan, R.O.C.
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5
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Liao C, Santoscoy MC, Craft J, Anderson C, Soupir ML, Jarboe LR. Allelic variation of Escherichia coli outer membrane protein A: Impact on cell surface properties, stress tolerance and allele distribution. PLoS One 2022; 17:e0276046. [PMID: 36227900 PMCID: PMC9560509 DOI: 10.1371/journal.pone.0276046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Accepted: 09/27/2022] [Indexed: 12/02/2022] Open
Abstract
Outer membrane protein A (OmpA) is one of the most abundant outer membrane proteins of Gram-negative bacteria and is known to have patterns of sequence variations at certain amino acids-allelic variation-in Escherichia coli. Here we subjected seven exemplar OmpA alleles expressed in a K-12 (MG1655) ΔompA background to further characterization. These alleles were observed to significantly impact cell surface charge (zeta potential), cell surface hydrophobicity, biofilm formation, sensitivity to killing by neutrophil elastase, and specific growth rate at 42°C and in the presence of acetate, demonstrating that OmpA is an attractive target for engineering cell surface properties and industrial phenotypes. It was also observed that cell surface charge and biofilm formation both significantly correlate with cell surface hydrophobicity, a cell property that is increasingly intriguing for bioproduction. While there was poor alignment between the observed experimental values relative to the known sequence variation, differences in hydrophobicity and biofilm formation did correspond to the identity of residue 203 (N vs T), located within the proposed dimerization domain. The relative abundance of the (I, δ) allele was increased in extraintestinal pathogenic E. coli (ExPEC) isolates relative to environmental isolates, with a corresponding decrease in (I, α) alleles in ExPEC relative to environmental isolates. The (I, α) and (I, δ) alleles differ at positions 203 and 251. Variations in distribution were also observed among ExPEC types and phylotypes. Thus, OmpA allelic variation and its influence on OmpA function warrant further investigation.
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Affiliation(s)
- Chunyu Liao
- Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, Iowa, United States of America
| | - Miguel C. Santoscoy
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa United States of America
| | - Julia Craft
- Department of Chemical and Biological Engineering, Biological Materials and Processes (BioMAP) NSF REU Program, Iowa State University, Ames, Iowa, United States of America
| | - Chiron Anderson
- Department of Chemical and Biological Engineering, Biological Materials and Processes (BioMAP) NSF REU Program, Iowa State University, Ames, Iowa, United States of America
| | - Michelle L. Soupir
- Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, Iowa, United States of America
| | - Laura R. Jarboe
- Interdepartmental Microbiology Graduate Program, Iowa State University, Ames, Iowa, United States of America
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa United States of America
- * E-mail:
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6
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Structural basis of lipoprotein recognition by the bacterial Lol trafficking chaperone LolA. Proc Natl Acad Sci U S A 2022; 119:e2208662119. [PMID: 36037338 PMCID: PMC9457489 DOI: 10.1073/pnas.2208662119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Lipoproteins in gram-negative bacteria underpin the formation and maintenance of the outer membrane that constitutes a vital protective barrier against antibiotics and other noxious molecules. An essential transport system comprising the LolABCDE proteins is required to traffic lipoproteins to the outer membrane. Following maturation on the inner membrane and extraction by the LolCDE transporter, lipoproteins are passed to the chaperone LolA that carries them across the periplasm prior to insertion into the outer membrane by the LolB receptor. Here, we report the molecular details of lipoprotein interaction with the chaperone LolA, a key intermediate located at the heart of the Lol pathway. The structure provides valuable insights into this important system and could be exploited to develop new antimicrobials. In gram-negative bacteria, lipoproteins are vital structural components of the outer membrane (OM) and crucial elements of machineries central to the physiology of the cell envelope. A dedicated apparatus, the Lol system, is required for the correct localization of OM lipoproteins and is essential for viability. The periplasmic chaperone LolA is central to this trafficking pathway, accepting triacylated lipoproteins from the inner membrane transporter LolCDE, before carrying them across the periplasm to the OM receptor LolB. Here, we report a crystal structure of liganded LolA, generated in vivo, revealing the molecular details of lipoprotein association. The structure highlights how LolA, initially primed to receive lipoprotein by interaction with LolC, further opens to accommodate the three ligand acyl chains in a precise conformation within its cavity. LolA forms extensive interactions with the acyl chains but not with any residue of the cargo, explaining the chaperone’s ability to transport structurally diverse lipoproteins. Structural characterization of a ligandedLolA variant incapable of lipoprotein release reveals aberrant association, demonstrating the importance of the LolCDE-coordinated, sequential opening of LolA for inserting lipoprotein in a manner productive for subsequent trafficking. Comparison with existing structures of LolA in complex with LolC or LolCDE reveals substantial overlap of the lipoprotein and LolC binding sites within the LolA cavity, demonstrating that insertion of lipoprotein acyl chains physically disengages the chaperone protein from the transporter by perturbing interaction with LolC. Taken together, our data provide a key step toward a complete understanding of a fundamentally important trafficking pathway.
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7
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A Defect in Lipoprotein Modification by Lgt Leads to Abnormal Morphology and Cell Death in Escherichia coli That Is Independent of Major Lipoprotein Lpp. J Bacteriol 2022; 204:e0016422. [PMID: 35938851 PMCID: PMC9487459 DOI: 10.1128/jb.00164-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Lgt is an essential enzyme in proteobacteria and therefore a potential target for novel antibiotics. The effect of Lgt depletion on growth, morphology, and viability was studied in Escherichia coli to assess whether absence of Lgt leads to cell death. Two Lgt depletion strains were used in which lgt was under the control of an arabinose-inducible promoter that allowed regulation of Lgt protein levels. Reduced levels of Lgt led to severe growth and morphological defects that could be restored by expressing lgt in trans, demonstrating that only Lgt is responsible for the distorted phenotypes. In the absence of major lipoprotein Lpp, growth defects were partially restored when low levels of Lgt were still present; however, lgt could not be deleted in the absence of Lpp. Our results demonstrate that Lpp is not the main cause of cell death under conditions of Lgt depletion and that other lipoproteins are important in cell envelope biogenesis and cell viability. Specific inhibitors of Lgt are thus promising for the development of novel antibiotics. IMPORTANCE Incomplete maturation and envelope mislocalization of lipoproteins, through inhibition or mutations in lipoprotein modification enzymes or transport to the outer membrane, are lethal in proteobacteria. Resistance to small-molecule inhibition or the appearance of suppressor mutations is often directly correlated with the presence of abundant outer membrane lipoprotein Lpp. Our results show that Lgt, the first enzyme of the lipoprotein modification pathway, is still required for growth and viability in the absence of Lpp and thus is necessary for the function of other essential lipoproteins in the cell envelope. This adds credence to the hypothesis that Lgt is essential in proteobacteria and an attractive target for the development of novel antibiotics.
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8
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Thoma J, Burmann BM. Architects of their own environment: How membrane proteins shape the Gram-negative cell envelope. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 128:1-34. [PMID: 35034716 DOI: 10.1016/bs.apcsb.2021.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Gram-negative bacteria are surrounded by a complex multilayered cell envelope, consisting of an inner and an outer membrane, and separated by the aqueous periplasm, which contains a thin peptidoglycan cell wall. These bacteria employ an arsenal of highly specialized membrane protein machineries to ensure the correct assembly and maintenance of the membranes forming the cell envelope. Here, we review the diverse protein systems, which perform these functions in Escherichia coli, such as the folding and insertion of membrane proteins, the transport of lipoproteins and lipopolysaccharide within the cell envelope, the targeting of phospholipids, and the regulation of mistargeted envelope components. Some of these protein machineries have been known for a long time, yet still hold surprises. Others have only recently been described and some are still missing pieces or yet remain to be discovered.
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Affiliation(s)
- Johannes Thoma
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Göteborg, Sweden; Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden.
| | - Björn M Burmann
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Göteborg, Sweden; Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
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9
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Harshaw NS, Stella NA, Lehner KM, Romanowski EG, Kowalski RP, Shanks RMQ. Antibiotics Used in Empiric Treatment of Ocular Infections Trigger the Bacterial Rcs Stress Response System Independent of Antibiotic Susceptibility. Antibiotics (Basel) 2021; 10:antibiotics10091033. [PMID: 34572615 PMCID: PMC8470065 DOI: 10.3390/antibiotics10091033] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/18/2021] [Accepted: 08/21/2021] [Indexed: 12/02/2022] Open
Abstract
The Rcs phosphorelay is a bacterial stress response system that responds to envelope stresses and in turn controls several virulence-associated pathways, including capsule, flagella, and toxin biosynthesis, of numerous bacterial species. The Rcs system also affects antibiotic tolerance, biofilm formation, and horizontal gene transfer. The Rcs system of the ocular bacterial pathogen Serratia marcescens was recently demonstrated to influence ocular pathogenesis in a rabbit model of keratitis, with Rcs-defective mutants causing greater pathology and Rcs-activated strains demonstrating reduced inflammation. The Rcs system is activated by a variety of insults, including β-lactam antibiotics and polymyxin B. In this study, we developed three luminescence-based transcriptional reporters for Rcs system activity and used them to test whether antibiotics used for empiric treatment of ocular infections influence Rcs system activity in a keratitis isolate of S. marcescens. These included antibiotics to which the bacteria were susceptible and resistant. Results indicate that cefazolin, ceftazidime, polymyxin B, and vancomycin activate the Rcs system to varying degrees in an RcsB-dependent manner, whereas ciprofloxacin and tobramycin activated the promoter fusions, but in an Rcs-independent manner. Although minimum inhibitory concentration (MIC) analysis demonstrated resistance of the test bacteria to polymyxin B and vancomycin, the Rcs system was activated by sub-inhibitory concentrations of these antibiotics. Together, these data indicate that a bacterial stress system that influences numerous pathogenic phenotypes and drug-tolerance is influenced by different classes of antibiotics despite the susceptibility status of the bacterium.
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10
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Steenhuis M, Corona F, ten Hagen-Jongman CM, Vollmer W, Lambin D, Selhorst P, Klaassen H, Versele M, Chaltin P, Luirink J. Combining Cell Envelope Stress Reporter Assays in a Screening Approach to Identify BAM Complex Inhibitors. ACS Infect Dis 2021; 7:2250-2263. [PMID: 34125508 PMCID: PMC8369490 DOI: 10.1021/acsinfecdis.0c00728] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Indexed: 12/11/2022]
Abstract
The development of new antibiotics is particularly problematic in Gram-negative bacteria due to the presence of the outer membrane (OM), which serves as a permeability barrier. Recently, the β-barrel assembly machine (BAM), located in the OM and responsible for β-barrel type OM protein (OMP) assembly, has been validated as a novel target for antibiotics. Here, we identified potential BAM complex inhibitors using a screening approach that reports on cell envelope σE and Rcs stress in Escherichia coli. Screening a library consisting of 316 953 compounds yielded five compounds that induced σE and Rcs stress responses, while not inducing the intracellular heat-shock response. Two of the five compounds (compounds 2 and 14) showed the characteristics of known BAM complex inhibitors: synergy with OMP biogenesis mutants, decrease in the abundance of various OMPs, and loss of OM integrity. Importantly, compound 2 also inhibited BAM-dependent OMP folding in an in vitro refolding assay using purified BAM complex reconstituted in proteoliposomes.
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Affiliation(s)
- Maurice Steenhuis
- Department
of Molecular Microbiology, Amsterdam Institute
of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081HV Amsterdam, The Netherlands
| | - Federico Corona
- Centre
for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle
upon Tyne NE2 4HH, United
Kingdom
| | - Corinne M. ten Hagen-Jongman
- Department
of Molecular Microbiology, Amsterdam Institute
of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081HV Amsterdam, The Netherlands
| | - Waldemar Vollmer
- Centre
for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle
upon Tyne NE2 4HH, United
Kingdom
| | - Dominique Lambin
- Centre
for Innovation and Stimulation of Drug Discovery (CISTIM), Gaston Geenslaan 2, B-3001 Leuven, Belgium
| | - Philippe Selhorst
- Centre
for Innovation and Stimulation of Drug Discovery (CISTIM), Gaston Geenslaan 2, B-3001 Leuven, Belgium
| | - Hugo Klaassen
- Centre
for Innovation and Stimulation of Drug Discovery (CISTIM), Gaston Geenslaan 2, B-3001 Leuven, Belgium
| | - Matthias Versele
- Centre
for Innovation and Stimulation of Drug Discovery (CISTIM), Gaston Geenslaan 2, B-3001 Leuven, Belgium
| | - Patrick Chaltin
- Center
for Drug Design and Development (CD3), KU
Leuven R&D, Waaistraat 6, B-3000 Leuven, Belgium
| | - Joen Luirink
- Department
of Molecular Microbiology, Amsterdam Institute
of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081HV Amsterdam, The Netherlands
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11
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Disorder is a critical component of lipoprotein sorting in Gram-negative bacteria. Nat Chem Biol 2021; 17:1093-1100. [PMID: 34326538 DOI: 10.1038/s41589-021-00845-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 06/29/2021] [Indexed: 01/01/2023]
Abstract
Gram-negative bacteria express structurally diverse lipoproteins in their cell envelope. Here, we find that approximately half of lipoproteins destined to the Escherichia coli outer membrane display an intrinsically disordered linker at their N terminus. Intrinsically disordered regions are common in proteins, but establishing their importance in vivo has remained challenging. As we sought to unravel how lipoproteins mature, we discovered that unstructured linkers are required for optimal trafficking by the Lol lipoprotein sorting system, whereby linker deletion re-routes three unrelated lipoproteins to the inner membrane. Focusing on the stress sensor RcsF, we found that replacing the linker with an artificial peptide restored normal outer-membrane targeting only when the peptide was of similar length and disordered. Overall, this study reveals the role played by intrinsic disorder in lipoprotein sorting, providing mechanistic insight into the biogenesis of these proteins and suggesting that evolution can select for intrinsic disorder that supports protein function.
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12
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El Rayes J, Rodríguez-Alonso R, Collet JF. Lipoproteins in Gram-negative bacteria: new insights into their biogenesis, subcellular targeting and functional roles. Curr Opin Microbiol 2021; 61:25-34. [PMID: 33667939 DOI: 10.1016/j.mib.2021.02.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 02/05/2021] [Accepted: 02/08/2021] [Indexed: 02/06/2023]
Abstract
Bacterial lipoproteins are globular proteins anchored to a membrane by a lipid moiety. By discovering new functions carried out by lipoproteins, recent research has highlighted the crucial roles played by these proteins in the cell envelope of Gram-negative bacteria. Here, after discussing the wide range of activities carried out by lipoproteins in the model bacterium Escherichia coli, we review new insights into the essential mechanisms involved in lipoprotein maturation, sorting and targeting to their final destination. A special attention will also be given to the recent identification of lipoproteins on the surface of E. coli and of other bacteria. The renewed interest in lipoproteins is driven by the need to identify novel targets for antibiotic development.
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Affiliation(s)
- Jessica El Rayes
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Raquel Rodríguez-Alonso
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Jean-François Collet
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium.
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13
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Steenhuis M, ten Hagen-Jongman CM, van Ulsen P, Luirink J. Stress-Based High-Throughput Screening Assays to Identify Inhibitors of Cell Envelope Biogenesis. Antibiotics (Basel) 2020; 9:antibiotics9110808. [PMID: 33202774 PMCID: PMC7698014 DOI: 10.3390/antibiotics9110808] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 11/10/2020] [Accepted: 11/11/2020] [Indexed: 11/16/2022] Open
Abstract
The structural integrity of the Gram-negative cell envelope is guarded by several stress responses, such as the σE, Cpx and Rcs systems. Here, we report on assays that monitor these responses in E. coli upon addition of antibacterial compounds. Interestingly, compromised peptidoglycan synthesis, outer membrane biogenesis and LPS integrity predominantly activated the Rcs response, which we developed into a robust HTS (high-throughput screening) assay that is suited for phenotypic compound screening. Furthermore, by interrogating all three cell envelope stress reporters, and a reporter for the cytosolic heat-shock response as control, we found that inhibitors of specific envelope targets induce stress reporter profiles that are distinct in quality, amplitude and kinetics. Finally, we show that by using a host strain with a more permeable outer membrane, large-scaffold antibiotics can also be identified by the reporter assays. Together, the data suggest that stress profiling is a useful first filter for HTS aimed at inhibitors of cell envelope processes.
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14
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Dekoninck K, Létoquart J, Laguri C, Demange P, Bevernaegie R, Simorre JP, Dehu O, Iorga BI, Elias B, Cho SH, Collet JF. Defining the function of OmpA in the Rcs stress response. eLife 2020; 9:60861. [PMID: 32985973 PMCID: PMC7553776 DOI: 10.7554/elife.60861] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 09/26/2020] [Indexed: 01/18/2023] Open
Abstract
OmpA, a protein commonly found in the outer membrane of Gram-negative bacteria, has served as a paradigm for the study of β-barrel proteins for several decades. In Escherichia coli, OmpA was previously reported to form complexes with RcsF, a surface-exposed lipoprotein that triggers the Rcs stress response when damage occurs in the outer membrane and the peptidoglycan. How OmpA interacts with RcsF and whether this interaction allows RcsF to reach the surface has remained unclear. Here, we integrated in vivo and in vitro approaches to establish that RcsF interacts with the C-terminal, periplasmic domain of OmpA, not with the N-terminal β-barrel, thus implying that RcsF does not reach the bacterial surface via OmpA. Our results suggest a novel function for OmpA in the cell envelope: OmpA competes with the inner membrane protein IgaA, the downstream Rcs component, for RcsF binding across the periplasm, thereby regulating the Rcs response.
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Affiliation(s)
- Kilian Dekoninck
- WELBIO, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain (UCLouvain), Brussels, Belgium
| | - Juliette Létoquart
- WELBIO, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain (UCLouvain), Brussels, Belgium
| | | | - Pascal Demange
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, Université Paul Sabatier, Toulouse, France
| | - Robin Bevernaegie
- Institut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Université catholique de Louvain (UCLouvain), Louvain-la-Neuve, Belgium
| | | | - Olivia Dehu
- de Duve Institute, Université catholique de Louvain (UCLouvain), Brussels, Belgium
| | - Bogdan I Iorga
- de Duve Institute, Université catholique de Louvain (UCLouvain), Brussels, Belgium.,Université Paris-Saclay, CNRS UPR 2301, Institut de Chimie des Substances Naturelles, Gif-sur-Yvette, France
| | - Benjamin Elias
- Institut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Université catholique de Louvain (UCLouvain), Louvain-la-Neuve, Belgium
| | - Seung-Hyun Cho
- WELBIO, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain (UCLouvain), Brussels, Belgium
| | - Jean-Francois Collet
- WELBIO, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain (UCLouvain), Brussels, Belgium
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15
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Collet JF, Cho SH, Iorga BI, Goemans CV. How the assembly and protection of the bacterial cell envelope depend on cysteine residues. J Biol Chem 2020; 295:11984-11994. [PMID: 32487747 PMCID: PMC7443483 DOI: 10.1074/jbc.rev120.011201] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/02/2020] [Indexed: 12/15/2022] Open
Abstract
The cell envelope of Gram-negative bacteria is a multilayered structure essential for bacterial viability; the peptidoglycan cell wall provides shape and osmotic protection to the cell, and the outer membrane serves as a permeability barrier against noxious compounds in the external environment. Assembling the envelope properly and maintaining its integrity are matters of life and death for bacteria. Our understanding of the mechanisms of envelope assembly and maintenance has increased tremendously over the past two decades. Here, we review the major achievements made during this time, giving central stage to the amino acid cysteine, one of the least abundant amino acid residues in proteins, whose unique chemical and physical properties often critically support biological processes. First, we review how cysteines contribute to envelope homeostasis by forming stabilizing disulfides in crucial bacterial assembly factors (LptD, BamA, and FtsN) and stress sensors (RcsF and NlpE). Second, we highlight the emerging role of enzymes that use cysteine residues to catalyze reactions that are necessary for proper envelope assembly, and we also explain how these enzymes are protected from oxidative inactivation. Finally, we suggest future areas of investigation, including a discussion of how cysteine residues could contribute to envelope homeostasis by functioning as redox switches. By highlighting the redox pathways that are active in the envelope of Escherichia coli, we provide a timely overview of the assembly of a cellular compartment that is the hallmark of Gram-negative bacteria.
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Affiliation(s)
| | - Seung-Hyun Cho
- de Duve Institute, UCLouvain, Brussels, Belgium; WELBIO, Brussels, Belgium
| | - Bogdan I Iorga
- de Duve Institute, UCLouvain, Brussels, Belgium; Université Paris-Saclay, CNRS UPR 2301, Institut de Chimie des Substances Naturelles, Gif-sur-Yvette, France
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16
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Ayoub Moubareck C. Polymyxins and Bacterial Membranes: A Review of Antibacterial Activity and Mechanisms of Resistance. MEMBRANES 2020; 10:membranes10080181. [PMID: 32784516 PMCID: PMC7463838 DOI: 10.3390/membranes10080181] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 07/30/2020] [Accepted: 07/31/2020] [Indexed: 12/19/2022]
Abstract
Following their initial discovery in the 1940s, polymyxin antibiotics fell into disfavor due to their potential clinical toxicity, especially nephrotoxicity. However, the dry antibiotic development pipeline, together with the rising global prevalence of infections caused by multidrug-resistant (MDR) Gram-negative bacteria have both rejuvenated clinical interest in these polypeptide antibiotics. Parallel to the revival of their use, investigations into the mechanisms of action and resistance to polymyxins have intensified. With an initial known effect on biological membranes, research has uncovered the detailed molecular and chemical interactions that polymyxins have with Gram-negative outer membranes and lipopolysaccharide structure. In addition, genetic and epidemiological studies have revealed the basis of resistance to these agents. Nowadays, resistance to polymyxins in MDR Gram-negative pathogens is well elucidated, with chromosomal as well as plasmid-encoded, transferrable pathways. The aims of the current review are to highlight the important chemical, microbiological, and pharmacological properties of polymyxins, to discuss their mechanistic effects on bacterial membranes, and to revise the current knowledge about Gram-negative acquired resistance to these agents. Finally, recent research, directed towards new perspectives for improving these old agents utilized in the 21st century, to combat drug-resistant pathogens, is summarized.
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17
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Wall EA, Majdalani N, Gottesman S. IgaA negatively regulates the Rcs Phosphorelay via contact with the RcsD Phosphotransfer Protein. PLoS Genet 2020; 16:e1008610. [PMID: 32716926 PMCID: PMC7418988 DOI: 10.1371/journal.pgen.1008610] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 08/11/2020] [Accepted: 06/10/2020] [Indexed: 01/13/2023] Open
Abstract
Two-component systems and phosphorelays play central roles in the ability of bacteria to rapidly respond to changing environments. In E. coli and related enterobacteria, the complex Rcs phosphorelay is a critical player in the bacterial response to antimicrobial peptides, beta-lactam antibiotics, and other disruptions at the cell surface. The Rcs system is unusual in that an inner membrane protein, IgaA, is essential due to its negative regulation of the RcsC/RcsD/RcsB phosphorelay. While it is known that IgaA transduces signals from the outer membrane lipoprotein RcsF, how it interacts with the phosphorelay has remained unknown. Here we performed in vivo interaction assays and genetic dissection of the critical proteins and found that IgaA interacts with the phosphorelay protein RcsD, and that this interaction is necessary for regulation. Interactions between IgaA and RcsD within their respective periplasmic domains of these two proteins anchor repression of signaling. However, the signaling response depends on a second interaction between cytoplasmic loop 1 of IgaA and a truncated Per-Arndt-Sim (PAS-like) domain in RcsD. A single point mutation in the PAS-like domain increased interactions between the two proteins and blocked induction of the phosphorelay. IgaA may regulate RcsC, the histidine kinase that initiates phosphotransfer through the phosphorelay, indirectly, via its contacts with RcsD. Unlike RcsD, and unlike many other histidine kinases, the periplasmic domain of RcsC is dispensable for the response to signals that induce the Rcs phosphorelay system. The multiple contacts between IgaA and RcsD constitute a poised sensing system, preventing potentially toxic over-activation of this phosphorelay while enabling it to rapidly and quantitatively respond to signals. The Rcs phosphorelay system plays a central role in allowing enterobacteria to sense and respond to antibiotics, host-produced antimicrobials, and interactions with surfaces. A unique negative regulator, IgaA, attenuates signaling from this pathway when it is not needed, but how IgaA controls the phosphorelay has been unclear. We define a set of critical interactions between IgaA and the phosphotransfer protein RcsD, including a periplasmic contact between IgaA and RcsD that mediates a necessary inhibition of Rcs signaling. Inhibition is further modulated by regulated interactions between the cytoplasmic domains of each protein, providing a sensitive regulatory switch.
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Affiliation(s)
- Erin A. Wall
- National Cancer Institute, Bethesda, Maryland, United States of America
| | - Nadim Majdalani
- National Cancer Institute, Bethesda, Maryland, United States of America
| | - Susan Gottesman
- National Cancer Institute, Bethesda, Maryland, United States of America
- * E-mail:
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18
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Rodríguez-Alonso R, Létoquart J, Nguyen VS, Louis G, Calabrese AN, Iorga BI, Radford SE, Cho SH, Remaut H, Collet JF. Structural insight into the formation of lipoprotein-β-barrel complexes. Nat Chem Biol 2020; 16:1019-1025. [PMID: 32572278 PMCID: PMC7610366 DOI: 10.1038/s41589-020-0575-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 05/15/2020] [Indexed: 12/14/2022]
Abstract
The β-barrel assembly machinery (BAM) inserts outer membrane β-barrel proteins (OMPs) in the outer membrane of Gram-negative bacteria. In Enterobacteriacea, BAM also mediates export of the stress sensor lipoprotein RcsF to the cell surface by assembling RcsF-OMP complexes. Here, we report the crystal structure of the key BAM component BamA in complex with RcsF. BamA adopts an inward-open conformation, with the lateral gate to the membrane closed. RcsF is lodged deep inside the lumen of the BamA barrel, binding regions proposed to undergo an outward and lateral opening during OMP insertion. On the basis of our structural and biochemical data, we propose a push-and-pull model for RcsF export upon conformational cycling of BamA and provide a mechanistic explanation for how RcsF uses its interaction with BamA to detect envelope stress. Our data also suggest that the flux of incoming OMP substrates is involved in the control of BAM activity.
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Affiliation(s)
- Raquel Rodríguez-Alonso
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Juliette Létoquart
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Van Son Nguyen
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.,Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium
| | - Gwennaelle Louis
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Bogdan I Iorga
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium.,Université Paris-Saclay, Institut de Chimie des Substances Naturelles, Gif-sur-Yvette, France
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Seung-Hyun Cho
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium. .,de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
| | - Han Remaut
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium. .,Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium.
| | - Jean-François Collet
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium. .,de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
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19
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Verma S, Prescott RA, Ingano L, Nickerson KP, Hill E, Faherty CS, Fasano A, Senger S, Cherayil BJ. The YrbE phospholipid transporter of Salmonella enterica serovar Typhi regulates the expression of flagellin and influences motility, adhesion and induction of epithelial inflammatory responses. Gut Microbes 2020; 11:526-538. [PMID: 31829769 PMCID: PMC7527071 DOI: 10.1080/19490976.2019.1697593] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
serovar Typhi is the etiologic agent of typhoid fever, a major public health problem in the developing world. Moving toward and adhering to the intestinal epithelium represents key initial steps of infection by S. Typhi. We examined the role of the S. Typhi yrbE gene, which encodes an inner membrane phospholipid transporter, in these interactions with epithelial cells. Disruption of yrbE resulted in elevated expression of flagellin and a hypermotile phenotype. It also significantly reduced the ability of S. Typhi to adhere to the HeLa epithelial cell line and to polarized primary epithelial cells derived from human ileal organoids. Interestingly, the yrbE-deficient strain of S. Typhi induced higher production of interleukin-8 from the primary human ileal epithelial cell monolayers compared to the wild-type bacteria. Deletion of the flagellin gene (fliC) in the yrbE-deficient S. Typhi inhibited motility and attenuated interleukin-8 production, but it did not correct the defect in adhesion. We also disrupted yrbE in S. Typhimurium. In contrast to the results in S. Typhi, the deficiency of yrbE in S. Typhimurium had no significant effect on flagellin expression, motility or adhesion to HeLa cells. Correspondingly, the lack of yrbE also had no effect on association with the intestine or the severity of intestinal inflammation in the mouse model of S. Typhimurium infection. Thus, our results point to an important and serovar-specific role played by yrbE in the early stages of intestinal infection by S. Typhi.
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Affiliation(s)
- Smriti Verma
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Rachel A. Prescott
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Laura Ingano
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Kourtney P. Nickerson
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Emily Hill
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Christina S. Faherty
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Alessio Fasano
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Stefania Senger
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Bobby J. Cherayil
- Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA,Department of Pediatrics, Harvard Medical School, Boston, MA, USA,CONTACT Bobby J. Cherayil Mucosal Immunology and Biology Research Center, Department of Pediatrics, Massachusetts General Hospital, Boston, MA, USA
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20
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Porins and small-molecule translocation across the outer membrane of Gram-negative bacteria. Nat Rev Microbiol 2019; 18:164-176. [DOI: 10.1038/s41579-019-0294-2] [Citation(s) in RCA: 135] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2019] [Indexed: 02/07/2023]
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21
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Delhaye A, Collet JF, Laloux G. A Fly on the Wall: How Stress Response Systems Can Sense and Respond to Damage to Peptidoglycan. Front Cell Infect Microbiol 2019; 9:380. [PMID: 31799211 PMCID: PMC6863773 DOI: 10.3389/fcimb.2019.00380] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 10/24/2019] [Indexed: 01/10/2023] Open
Abstract
The envelope of Gram-negative bacteria is critical for survival across a wide range of environmental conditions. The inner membrane, the periplasm and the outer membrane form a complex compartment, home to many essential processes. Hence, constant monitoring by envelope stress response systems ensure correct biogenesis of the envelope and maintain its homeostasis. Inside the periplasm, the cell wall, made of peptidoglycan, has been under the spotlight for its critical role in bacterial growth as well as being the target of many antibiotics. While much research is centered around understanding the role of the many enzymes involved in synthesizing the cell wall, much less is known about how the cell can detect perturbations of this assembly process, and how it is regulated during stress. In this review, we explore the current knowledge of cell wall defects sensing by stress response systems, mainly in the model bacterium Escherichia coli. We also discuss how these systems can respond to cell wall perturbations to increase fitness, and what implications this has on cell wall regulation.
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Affiliation(s)
- Antoine Delhaye
- de Duve Institute, UCLouvain, Brussels, Belgium.,Walloon Excellence in Life Sciences and Biotechnology (WELBIO), Brussels, Belgium
| | - Jean-François Collet
- de Duve Institute, UCLouvain, Brussels, Belgium.,Walloon Excellence in Life Sciences and Biotechnology (WELBIO), Brussels, Belgium
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22
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Giannini E, González LJ, Vila AJ. A simple protocol to characterize bacterial cell-envelope lipoproteins in a native-like environment. Protein Sci 2019; 28:2004-2010. [PMID: 31518027 DOI: 10.1002/pro.3728] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 01/04/2023]
Abstract
Physiological conditions in living cells are strictly regulated to allow, optimize, and coordinate biological processes. The bacterial cell envelope is the compartment where the communication with the external environment takes place. This involves membrane proteins, key players in many biological processes that ensure bacterial survival. The biochemical characterization of membrane proteins, either integral, lipidated or peripheral is challenging due to their mixed protein-lipid nature, making it difficult to purify and obtain considerable amounts of samples. In contrast to integral membrane proteins, lipidated proteins are usually purified as truncated soluble versions, neglecting the impact of the membrane environment. Here we report a simple and robust protocol to characterize bacterial lipidated proteins in spheroplasts from Escherichia coli using a β-lactamase as a model. The Metallo-β-lactamase NDM-1 is an enzyme anchored to the inner leaflet of the outer membrane of Gram-negative bacteria. Kinetic parameters and stability of the lipidated NDM-1 and the soluble unbound version (NDM-1 C26A) were measured in spheroplasts and periplasm, respectively. These studies revealed that membrane anchoring increases the KM of the enzyme, consequently decreasing the catalytic efficiency, while not affecting its kinetic stability. This approach can be used to characterize lipidated proteins avoiding the purification step while mimicking its native environment. This approach also helps in filling the gap between in vitro and in vivo studies.
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Affiliation(s)
- Estefanía Giannini
- Laboratorio de Metaloproteínas, Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Rosario, Argentina
| | - Lisandro J González
- Laboratorio de Metaloproteínas, Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Rosario, Argentina.,Área Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Alejandro J Vila
- Laboratorio de Metaloproteínas, Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Rosario, Argentina.,Área Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
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23
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Marsh JW, Mustapha MM, Griffith MP, Evans DR, Ezeonwuka C, Pasculle AW, Shutt KA, Sundermann A, Ayres AM, Shields RK, Babiker A, Cooper VS, Van Tyne D, Harrison LH. Evolution of Outbreak-Causing Carbapenem-Resistant Klebsiella pneumoniae ST258 at a Tertiary Care Hospital over 8 Years. mBio 2019; 10:e01945-19. [PMID: 31481386 PMCID: PMC6722418 DOI: 10.1128/mbio.01945-19] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/09/2019] [Indexed: 12/21/2022] Open
Abstract
Carbapenem-resistant Klebsiella pneumoniae (CRKP) strains belonging to sequence type 258 (ST258) are frequent causes of hospital-associated outbreaks and are a major contributor to the spread of carbapenemases. This genetic lineage emerged several decades ago and remains a major global health care challenge. In this study, genomic epidemiology was used to investigate the emergence, evolution, and persistence of ST258 carbapenem-resistant K. pneumoniae outbreak-causing lineages at a large tertiary care hospital over 8 years. A time-based phylogenetic analysis of 136 ST258 isolates demonstrated the succession of multiple genetically distinct ST258 sublineages over the 8-year period. Ongoing genomic surveillance identified the emergence and persistence of several distinct clonal ST258 populations. Patterns of multidrug resistance determinants and plasmid replicons were consistent with continued evolution and persistence of these populations. Five ST258 outbreaks were documented, including three that were caused by the same clonal lineage. Mutations in genes encoding effectors of biofilm production and iron acquisition were identified among persistent clones. Two emergent lineages bearing K. pneumoniae integrative conjugative element 10 (ICEKp10) and harboring yersiniabactin and colibactin virulence factors were identified. The results show how distinct ST258 subpopulations have evolved and persisted within the same hospital over nearly a decade.IMPORTANCE The carbapenem class of antibiotics is invaluable for the treatment of selected multidrug-resistant Gram-negative pathogens. The continued transmission of carbapenem-resistant bacteria such as ST258 K. pneumoniae is of serious global public health concern, as treatment options for these infections are limited. This genomic epidemiologic investigation traced the natural history of ST258 K. pneumoniae in a single health care setting over nearly a decade. We found that distinct ST258 subpopulations have caused both device-associated and ward-associated outbreaks, and some of these populations remain endemic within our hospital to the present day. The finding of virulence determinants among emergent ST258 clones supports the idea of convergent evolution of drug-resistant and virulent CRKP strains and highlights the need for continued surveillance, prevention, and control efforts to address emergent and evolving ST258 populations in the health care setting.
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Affiliation(s)
- Jane W Marsh
- Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
| | - Mustapha M Mustapha
- Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
| | - Marissa P Griffith
- Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
| | - Daniel R Evans
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Chinelo Ezeonwuka
- Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
| | - A William Pasculle
- Division of Microbiology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Kathleen A Shutt
- Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
| | - Alexander Sundermann
- Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
- Division of Hospital Epidemiology and Infection Control, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Ashley M Ayres
- Division of Hospital Epidemiology and Infection Control, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Ryan K Shields
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Ahmed Babiker
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Vaughn S Cooper
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Daria Van Tyne
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Lee H Harrison
- Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
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24
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Emerging Roles for NlpE as a Sensor for Lipoprotein Maturation and Transport to the Outer Membrane in Escherichia coli. mBio 2019; 10:mBio.01302-19. [PMID: 31239385 PMCID: PMC6593411 DOI: 10.1128/mbio.01302-19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Outer membrane biogenesis is a complex process for Gram-negative bacteria as the components are synthesized in the cytoplasm or at the inner membrane and then transported to the outer membrane. Stress pathways monitor and respond to problems encountered in assembling the outer membrane. The two-component system CpxAR was recently reported to be a stress pathway for transport of lipoproteins to the outer membrane, but it was unclear how this stress is sensed. May et al. [K. L. May, K. M. Outer membrane biogenesis is a complex process for Gram-negative bacteria as the components are synthesized in the cytoplasm or at the inner membrane and then transported to the outer membrane. Stress pathways monitor and respond to problems encountered in assembling the outer membrane. The two-component system CpxAR was recently reported to be a stress pathway for transport of lipoproteins to the outer membrane, but it was unclear how this stress is sensed. May et al. [K. L. May, K. M. Lehman, A. M. Mitchell, and M. Grabowicz, mBio 10(3):e00618-19, 2019, https://doi.org/10.1128/mBio.00618-19] determined that an outer membrane lipoprotein, NlpE, is the sensor for lipoprotein biogenesis stress. The group demonstrated that CpxAR is activated by the N-terminal domain of NlpE when the lipoprotein accumulates at the inner membrane. Further, this work resolved a previously debated role for NlpE in sensing copper stress; copper was shown to inhibit acylation of lipoproteins, preventing them from being transported to the outer membrane.
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The Lipoprotein NlpE Is a Cpx Sensor That Serves as a Sentinel for Protein Sorting and Folding Defects in the Escherichia coli Envelope. J Bacteriol 2019; 201:JB.00611-18. [PMID: 30833359 DOI: 10.1128/jb.00611-18] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 03/01/2019] [Indexed: 12/18/2022] Open
Abstract
The envelope of Gram-negative bacteria is a complex compartment that is essential for viability. To ensure survival of the bacterial cells in fluctuating environments, several signal transduction systems, called envelope stress response systems (ESRSs), exist to monitor envelope biogenesis and homeostasis. The Cpx two-component system is an extensively studied ESRS in Escherichia coli that is active during exposure to a vast array of stresses and protects the envelope under those harmful circumstances. Overproduction of NlpE, a two-domain outer membrane lipoprotein of unclear function, has been used in numerous studies as a molecular trigger to turn on the system artificially. However, the mechanism of Cpx activation by NlpE, as well as its physiological relevance, awaited further investigation. In this paper, we provide novel insights into the role played by NlpE in the Cpx system. We found that, among all outer membrane lipoproteins in E. coli, NlpE is sufficient to induce Cpx when lipoprotein trafficking is perturbed. Under such conditions, fitness is increased by the presence of NlpE. Moreover, we show that NlpE, through its N-terminal domain, physically interacts with the Cpx sensor kinase CpxA. Our data suggest that NlpE also serves to activate the Cpx system during oxidative folding defects in the periplasm and that its C-terminal domain is involved in the sensing mechanism. Overall, our data demonstrate that NlpE acts as a sentinel for two important envelope biogenesis processes, namely, lipoprotein sorting and oxidative folding, and they further establish NlpE as a bona fide member of the Cpx two-component system.IMPORTANCE Bacteria rely on a sophisticated envelope to shield them against challenging environmental conditions and therefore need to ensure correct envelope assembly and integrity. A major signaling pathway that performs this role in Gram-negative species is the Cpx system. An outer membrane lipoprotein of unclear function, NlpE, has long been exploited as a research tool to study Cpx in E. coli, since it triggers this system when overproduced or mislocalized; however, the mechanism and physiological relevance of the NlpE-Cpx connection have awaited further investigation. We elucidate a new function for NlpE by showing that it physically interacts with the Cpx sensor CpxA and acts as a sentinel that specifically monitors two essential envelope biogenesis processes, namely, lipoprotein sorting and oxidative folding.
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The Two-Component System ZraPSR Is a Novel ESR that Contributes to Intrinsic Antibiotic Tolerance in Escherichia coli. J Mol Biol 2018; 430:4971-4985. [DOI: 10.1016/j.jmb.2018.10.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 09/24/2018] [Accepted: 10/26/2018] [Indexed: 11/22/2022]
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Kimkes TEP, Heinemann M. Reassessing the role of the Escherichia coli CpxAR system in sensing surface contact. PLoS One 2018; 13:e0207181. [PMID: 30412611 PMCID: PMC6226299 DOI: 10.1371/journal.pone.0207181] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 10/29/2018] [Indexed: 12/23/2022] Open
Abstract
For proper biofilm formation, bacteria must have mechanisms in place to sense adhesion to surfaces. In Escherichia coli, the CpxAR and RcsCDB systems have been reported to sense surfaces. The CpxAR system is widely considered to be responsible for sensing attachment, specifically to hydrophobic surfaces. Here, using both single-cell and population-level analyses, we confirm RcsCDB activation upon surface contact, but find that the CpxAR system is not activated, in contrast to what had earlier been reported. Thus, the role of CpxAR in surface sensing and initiation of biofilm formation should be reconsidered.
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Affiliation(s)
- Tom E. P. Kimkes
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Matthias Heinemann
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
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Giannakopoulou N, Mendis N, Zhu L, Gruenheid S, Faucher SP, Le Moual H. The Virulence Effect of CpxRA in Citrobacter rodentium Is Independent of the Auxiliary Proteins NlpE and CpxP. Front Cell Infect Microbiol 2018; 8:320. [PMID: 30280092 PMCID: PMC6153362 DOI: 10.3389/fcimb.2018.00320] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 08/22/2018] [Indexed: 02/06/2023] Open
Abstract
Citrobacter rodentium is a murine pathogen used to model the intestinal infection caused by Enteropathogenic and Enterohemorrhagic Escherichia coli (EPEC and EHEC), two diarrheal pathogens responsible for morbidity and mortality in developing and developed countries, respectively. During infection, these bacteria must sense and adapt to the gut environment of the host. In order to adapt to changing environmental cues and modulate expression of specific genes, bacteria can use two-component signal transduction systems (TCS). We have shown that the deletion of the Cpx TCS in C. rodentium leads to a marked attenuation in virulence in C3H/HeJ mice. In E. coli, the Cpx TCS is reportedly activated in response to signals from the outer-membrane lipoprotein NlpE. We therefore investigated the role of NlpE in C. rodentium virulence. We also assessed the role of the reported negative regulator of CpxRA, CpxP. We found that as opposed to the ΔcpxRA strain, neither the ΔnlpE, ΔcpxP nor the ΔnlpEΔcpxP strains were significantly attenuated, and had similar in vivo localization to wild-type C. rodentium. The in vitro adherence of the Cpx auxiliary protein mutants, ΔnlpE, ΔcpxP, ΔnlpEΔcpxP, was comparable to wild-type C. rodentium, whereas the ΔcpxRA strain showed significantly decreased adherence. To further elucidate the mechanisms behind the contrasting virulence phenotypes, we performed microarrays in order to define the regulon of the Cpx TCS. We detected 393 genes differentially regulated in the ΔcpxRA strain. The gene expression profile of the ΔnlpE strain is strikingly different than the profile of ΔcpxRA with regards to the genes activated by CpxRA. Further, there is no clear inverse correlation in the expression pattern of the ΔcpxP strain in comparison to ΔcpxRA. Taken together, these data suggest that in these conditions, CpxRA activates gene expression in a largely NlpE- and CpxP-independent manner. Compared to wildtype, 161 genes were downregulated in the ΔcpxRA strain, while being upregulated or unchanged in the Cpx auxiliary protein deletion strains. This group of genes, which we hypothesize may contribute to the loss of virulence of ΔcpxRA, includes T6SS components, ompF, the regulator for colanic acid synthesis, and several genes involved in maltose metabolism.
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Affiliation(s)
| | - Nilmini Mendis
- Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, Canada
| | - Lei Zhu
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
| | - Samantha Gruenheid
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
| | - Sebastien P Faucher
- Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, Canada
| | - Hervé Le Moual
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
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Göpel Y, Görke B. Interaction of lipoprotein QseG with sensor kinase QseE in the periplasm controls the phosphorylation state of the two-component system QseE/QseF in Escherichia coli. PLoS Genet 2018; 14:e1007547. [PMID: 30040820 PMCID: PMC6075780 DOI: 10.1371/journal.pgen.1007547] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 08/03/2018] [Accepted: 07/08/2018] [Indexed: 01/26/2023] Open
Abstract
Histidine kinase QseE and response regulator QseF compose a two-component system in Enterobacteriaceae. In Escherichia coli K-12 QseF activates transcription of glmY and of rpoE from Sigma 54-dependent promoters by binding to upstream activating sequences. Small RNA GlmY and RpoE (Sigma 24) are important regulators of cell envelope homeostasis. In pathogenic Enterobacteriaceae QseE/QseF are required for virulence. In enterohemorrhagic E. coli QseE was reported to sense the host hormone epinephrine and to regulate virulence genes post-transcriptionally through employment of GlmY. The qseEGF operon contains a third gene, qseG, which encodes a lipoprotein attached to the inner leaflet of the outer membrane. Here, we show that QseG is essential and limiting for activity of QseE/QseF in E. coli K-12. Metabolic 32P-labelling followed by pull-down demonstrates that phosphorylation of the receiver domain of QseF in vivo requires QseE as well as QseG. Accordingly, QseG acts upstream and through QseE/QseF by stimulating activity of kinase QseE. 32P-labelling also reveals an additional phosphorylation in the QseF C-terminus of unknown origin, presumably at threonine/serine residue(s). Pulldown and two-hybrid assays demonstrate interaction of QseG with the periplasmic loop of QseE. A mutational screen identifies the Ser58Asn exchange in the periplasmic loop of QseE, which decreases interaction with QseG and concomitantly lowers QseE/QseF activity, indicating that QseG activates QseE by interaction. Finally, epinephrine is shown to have a moderate impact on QseE activity in E. coli K-12. Epinephrine slightly stimulates QseF phosphorylation and thereby glmY transcription, but exclusively during stationary growth and this requires both, QseE and QseG. Our data reveal a three-component signaling system, in which the phosphorylation state of QseE/QseF is governed by interaction with lipoprotein QseG in response to a signal likely derived from the cell envelope.
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Affiliation(s)
- Yvonne Göpel
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories (MFPL), University of Vienna, Vienna Biocenter (VBC), Vienna, Austria
| | - Boris Görke
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories (MFPL), University of Vienna, Vienna Biocenter (VBC), Vienna, Austria
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Salmonella Tol-Pal Reduces Outer Membrane Glycerophospholipid Levels for Envelope Homeostasis and Survival during Bacteremia. Infect Immun 2018; 86:IAI.00173-18. [PMID: 29735519 PMCID: PMC6013679 DOI: 10.1128/iai.00173-18] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 04/27/2018] [Indexed: 12/22/2022] Open
Abstract
Salmonellae regulate membrane lipids during infection, but the exact proteins and mechanisms that promote their survival during bacteremia remain largely unknown. Mutations in genes encoding the conserved Salmonella enterica serovar Typhimurium (S. Typhimurium) Tol-Pal apparatus caused the outer membrane (OM) sensor lipoprotein, RcsF, to become activated. The capsule activation phenotype for the mutants suggested that Tol-Pal might influence envelope lipid homeostasis. The mechanism involves reducing OM glycerophospholipid (GPL) levels, since the mutant salmonellae similarly accumulated phosphatidylglycerols (PGl) and phosphatidylethanolamines (PE) within the OM in comparison to the wild type. The data support the Escherichia coli model, whereby Tol-Pal directs retrograde GPL translocation across the periplasm. The S. Typhimurium mechanism involves contributions from YbgC, a cytoplasmic acyl coenzyme A (acyl-CoA) thioesterase, and CpoB, a periplasmic TolA-binding protein. The functional relationship between Tol-Pal and YbgC and CpoB was previously unresolved. The S. Typhimurium Tol-Pal proteins contribute similarly toward promoting OM-GPL homeostasis and Rcs signaling inactivity but differently toward promoting bacterial morphology, rifampin resistance, survival in macrophages, and survival in mice. For example, tolQ, tolR, tolA, and cpoB mutants were significantly more attenuated than ybgC, tolB, and pal mutants in a systemic mouse model of disease. Therefore, key roles exist for TolQ, TolR, TolA, and CpoB during murine bacteremia, which are independent of maintaining GPL homeostasis. The ability of TolQR to channel protons across the inner membrane (IM) is necessary for S. Typhimurium TolQRA function, since mutating conserved channel-facing residues rendered TolQ ineffective at rescuing deletion mutant phenotypes. Therefore, Tol-Pal promotes S. Typhimurium survival during bacteremia, in part, by reducing OM GPL concentrations, while TolQRA and CpoB enhance systemic virulence by additional mechanisms.
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Abstract
RcsB, a response regulator of the FixJ/NarL family, is at the center of a complex network of regulatory inputs and outputs. Cell surface stress is sensed by an outer membrane lipoprotein, RcsF, which regulates interactions of the inner membrane protein IgaA, lifting negative regulation of a phosphorelay. In vivo evidence supports a pathway in which histidine kinase RcsC transfers phosphate to phosphotransfer protein RcsD, resulting in phosphorylation of RcsB. RcsB acts either alone or in combination with RcsA to positively regulate capsule synthesis and synthesis of small RNA (sRNA) RprA as well as other genes, and to negatively regulate motility. RcsB in combination with other FixJ/NarL auxiliary proteins regulates yet other functions, independent of RcsB phosphorylation. Proper expression of Rcs and its targets is critical for success of Escherichia coli commensal strains, for proper development of biofilm, and for virulence in some pathogens. New understanding of how the Rcs phosphorelay works provides insight into the flexibility of the two-component system paradigm.
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Affiliation(s)
- Erin Wall
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
| | - Nadim Majdalani
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
| | - Susan Gottesman
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
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Hussein NA, Cho SH, Laloux G, Siam R, Collet JF. Distinct domains of Escherichia coli IgaA connect envelope stress sensing and down-regulation of the Rcs phosphorelay across subcellular compartments. PLoS Genet 2018; 14:e1007398. [PMID: 29852010 PMCID: PMC5978795 DOI: 10.1371/journal.pgen.1007398] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 05/08/2018] [Indexed: 12/14/2022] Open
Abstract
In enterobacteria, the Rcs system (Regulator of capsule synthesis) monitors envelope integrity and induces a stress response when damages occur in the outer membrane or in the peptidoglycan layer. Built around a two-component system, Rcs controls gene expression via a cascade of phosphoryl transfer reactions. Being particularly complex, Rcs also involves the outer membrane lipoprotein RcsF and the inner membrane essential protein IgaA (Intracellular growth attenuator). RcsF and IgaA, which are located upstream of the phosphorelay, are required for normal Rcs functioning. Here, we establish the stress-dependent formation of a complex between RcsF and the periplasmic domain of IgaA as the molecular signal triggering Rcs. Moreover, molecular dissection of IgaA reveals that its negative regulatory role on Rcs is mostly carried by its first N-terminal cytoplasmic domain. Altogether, our results support a model in which IgaA regulates Rcs activation by playing a direct role in the transfer of signals from the cell envelope to the cytoplasm. This remarkable feature further distinguishes Rcs from other envelope stress response systems. A thorough understanding of the mechanisms that allow bacteria to thrive in various environments is crucial to the development of new antibiotics, an urgent endeavor to combat antimicrobial resistance. A landmark feature of Gram-negative bacteria is the presence of a multi-layered envelope. Because this structure is essential, its integrity is constantly monitored to detect and respond to potential breaches in a fast and adequate manner. Here, we describe how IgaA, an essential protein present in the cytoplasmic membrane of enterobacteria, participates in the transfer of stress signals from the envelope to the cytoplasm. We provide evidence that IgaA works in concert with RcsF, a lipoprotein that is posted as a sentinel in the outermost envelope layer, to detect envelope stress: under stress conditions, RcsF forms a complex with the C-terminal, periplasmic domain of IgaA. As a result, cells turn on the Rcs response. We also discovered that the N-terminal, cytoplasmic domain of IgaA plays an important role in inhibiting Rcs in the absence of stress. Together, these findings reveal that distinct IgaA domains coordinate stress sensing and Rcs activation across the cytoplasmic membrane. They enhance our understanding of Rcs regulation and open new avenues for the development of new antibacterials.
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Affiliation(s)
- Nahla A. Hussein
- WELBIO, Brussels, Belgium
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- Biology Department, Biotechnology Graduate Program and YJ-Science and Technology Research Center, American University in Cairo, Cairo, Egypt
| | - Seung-Hyun Cho
- WELBIO, Brussels, Belgium
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Géraldine Laloux
- WELBIO, Brussels, Belgium
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Rania Siam
- Biology Department, Biotechnology Graduate Program and YJ-Science and Technology Research Center, American University in Cairo, Cairo, Egypt
| | - Jean-François Collet
- WELBIO, Brussels, Belgium
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- * E-mail:
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Ranava D, Caumont-Sarcos A, Albenne C, Ieva R. Bacterial machineries for the assembly of membrane-embedded β-barrel proteins. FEMS Microbiol Lett 2018; 365:4961134. [DOI: 10.1093/femsle/fny087] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 04/03/2018] [Indexed: 12/11/2022] Open
Affiliation(s)
- David Ranava
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
| | - Anne Caumont-Sarcos
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
| | - Cécile Albenne
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
| | - Raffaele Ieva
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
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Abstract
Lectin-like bacteriocins (LlpAs) are secreted by proteobacteria and selectively kill strains of their own or related species, and they are composed of two B-lectin domains with divergent sequences. In Pseudomonas spp., initial binding of these antibacterial proteins to cells is mediated by the carboxy-terminal domain through d-rhamnose residues present in the common polysaccharide antigen of their lipopolysaccharide, whereas the amino-terminal domain accounts for strain selectivity of killing. Here, we show that spontaneous LlpA-resistant mutants carry mutations in one of three surface-exposed moieties of the essential β-barrel outer membrane protein insertase BamA, the core component of the BAM complex. Polymorphism of this loop in different Pseudomonas groups is linked to LlpA susceptibility, and targeted cells all share the same signature motif in this loop. Since heterologous expression of such a bamA gene confers LlpA susceptibility upon a resistant strain, BamA represents the primary bacteriocin selectivity determinant in pseudomonads. Contrary to modular bacteriocins that require uptake via the Tol or Ton system, parasitism of BamA as an LlpA receptor advocates a novel bacteriocin killing mechanism initiated by impairment of the BAM machinery. Bacteria secrete a variety of molecules to eliminate microbial rivals. Bacteriocins are a pivotal group of peptides and proteins that assist in this fight, specifically killing related bacteria. In Gram-negative bacteria, these antibacterial proteins often comprise distinct domains for initial binding to a target cell’s surface and subsequent killing via enzymatic or pore-forming activity. Here, we show that lectin-like bacteriocins, a family of bacteriocins that lack the prototypical modular toxin architecture, also stand out by parasitizing BamA, the core component of the outer membrane protein assembly machinery. A particular surface-exposed loop of BamA, critical for its function, serves as a key discriminant for cellular recognition, and polymorphisms in this loop determine whether a strain is susceptible or immune to a particular bacteriocin. These findings suggest a novel mechanism of contact-dependent killing that does not require cellular uptake. The evolutionary advantage of piracy of an essential cellular compound is highlighted by the observation that contact-dependent growth inhibition, a distinct antagonistic system, can equally take advantage of this receptor.
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An IgaA/UmoB Family Protein from Serratia marcescens Regulates Motility, Capsular Polysaccharide Biosynthesis, and Secondary Metabolite Production. Appl Environ Microbiol 2018; 84:AEM.02575-17. [PMID: 29305504 DOI: 10.1128/aem.02575-17] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 12/23/2017] [Indexed: 12/28/2022] Open
Abstract
Secondary metabolites are an important source of pharmaceuticals and key modulators of microbe-microbe interactions. The bacterium Serratia marcescens is part of the Enterobacteriaceae family of eubacteria and produces a number of biologically active secondary metabolites. In this study, we screened for novel regulators of secondary metabolites synthesized by a clinical isolate of S. marcescens and found mutations in a gene for an uncharacterized UmoB/IgaA family member here named gumB Mutation of gumB conferred a severe loss of the secondary metabolites prodigiosin and serratamolide. The gumB mutation conferred pleiotropic phenotypes, including altered biofilm formation, highly increased capsular polysaccharide production, and loss of swimming and swarming motility. These phenotypes corresponded to transcriptional changes in fimA, wecA, and flhD Unlike other UmoB/IgaA family members, gumB was found to be not essential for growth in S. marcescens, yet igaA from Salmonella enterica, yrfF from Escherichia coli, and an uncharacterized predicted ortholog from Klebsiella pneumoniae complemented the gumB mutant secondary metabolite defects, suggesting highly conserved function. These data support the idea that UmoB/IgaA family proteins are functionally conserved and extend the known regulatory influence of UmoB/IgaA family proteins to the control of competition-associated secondary metabolites and biofilm formation.IMPORTANCE IgaA/UmoB family proteins are found in members of the Enterobacteriaceae family of bacteria, which are of environmental and public health importance. IgaA/UmoB family proteins are thought to be inner membrane proteins that report extracellular stresses to intracellular signaling pathways that respond to environmental challenge. This study introduces a new member of the IgaA/UmoB family and demonstrates a high degree of functional similarity between IgaA/UmoB family proteins. Moreover, this study extends the phenomena controlled by IgaA/UmoB family proteins to include the biosynthesis of antimicrobial secondary metabolites.
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Asmar AT, Ferreira JL, Cohen EJ, Cho SH, Beeby M, Hughes KT, Collet JF. Communication across the bacterial cell envelope depends on the size of the periplasm. PLoS Biol 2017; 15:e2004303. [PMID: 29257832 PMCID: PMC5736177 DOI: 10.1371/journal.pbio.2004303] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/10/2017] [Indexed: 12/28/2022] Open
Abstract
The cell envelope of gram-negative bacteria, a structure comprising an outer (OM) and an inner (IM) membrane, is essential for life. The OM and the IM are separated by the periplasm, a compartment that contains the peptidoglycan. The OM is tethered to the peptidoglycan via the lipoprotein, Lpp. However, the importance of the envelope's multilayered architecture remains unknown. Here, when we removed physical coupling between the OM and the peptidoglycan, cells lost the ability to sense defects in envelope integrity. Further experiments revealed that the critical parameter for the transmission of stress signals from the envelope to the cytoplasm, where cellular behaviour is controlled, is the IM-to-OM distance. Augmenting this distance by increasing the length of the lipoprotein Lpp destroyed signalling, whereas simultaneously increasing the length of the stress-sensing lipoprotein RcsF restored signalling. Our results demonstrate the physiological importance of the size of the periplasm. They also reveal that strict control over the IM-to-OM distance is required for effective envelope surveillance and protection, suggesting that cellular architecture and the structure of transenvelope protein complexes have been evolutionarily co-optimised for correct function. Similar strategies are likely at play in cellular compartments surrounded by 2 concentric membranes, such as chloroplasts and mitochondria.
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Affiliation(s)
- Abir T. Asmar
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Josie L. Ferreira
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Eli J. Cohen
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Seung-Hyun Cho
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Morgan Beeby
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Kelly T. Hughes
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Jean-François Collet
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- WELBIO, Université catholique de Louvain, Brussels, Belgium
- * E-mail:
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Guo XP, Sun YC. New Insights into the Non-orthodox Two Component Rcs Phosphorelay System. Front Microbiol 2017; 8:2014. [PMID: 29089936 PMCID: PMC5651002 DOI: 10.3389/fmicb.2017.02014] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 09/29/2017] [Indexed: 01/18/2023] Open
Abstract
The Rcs phosphorelay system, a non-orthodox two-component regulatory system, integrates environmental signals, regulates gene expression, and alters the physiological behavior of members of the Enterobacteriaceae family of Gram-negative bacteria. Recent studies of Rcs system focused on protein interactions, functions, and the evolution of Rcs system components and its auxiliary regulatory proteins. Herein we review the latest advances on the Rcs system proteins, and discuss the roles that the Rcs system plays in the environmental adaptation of various Enterobacteriaceae species.
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Affiliation(s)
- Xiao-Peng Guo
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yi-Cheng Sun
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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