1
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Maybin M, Ranade AM, Schombel U, Gisch N, Mamat U, Meredith TC. IS 1-mediated chromosomal amplification of the arn operon leads to polymyxin B resistance in Escherichia coli B strains. mBio 2024:e0063424. [PMID: 38904391 DOI: 10.1128/mbio.00634-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Accepted: 05/14/2024] [Indexed: 06/22/2024] Open
Abstract
Polymyxins [colistin and polymyxin B (PMB)] comprise an important class of natural product lipopeptide antibiotics used to treat multidrug-resistant Gram-negative bacterial infections. These positively charged lipopeptides interact with lipopolysaccharide (LPS) located in the outer membrane and disrupt the permeability barrier, leading to increased uptake and bacterial cell death. Many bacteria counter polymyxins by upregulating genes involved in the biosynthesis and transfer of amine-containing moieties to increase positively charged residues on LPS. Although 4-deoxy-l-aminoarabinose (Ara4N) and phosphoethanolamine (PEtN) are highly conserved LPS modifications in Escherichia coli, different lineages exhibit variable PMB susceptibilities and frequencies of resistance for reasons that are poorly understood. Herein, we describe a mechanism prevalent in E. coli B strains that depends on specific insertion sequence 1 (IS1) elements that flank genes involved in the biosynthesis and transfer of Ara4N to LPS. Spontaneous and transient chromosomal amplifications mediated by IS1 raise the frequency of PMB resistance by 10- to 100-fold in comparison to strains where a single IS1 element located 90 kb away from the end of the arn operon has been deleted. Amplification involving IS1 becomes the dominant resistance mechanism in the absence of PEtN modification. Isolates with amplified arn operons gradually lose their PMB-resistant phenotype with passaging, consistent with classical PMB heteroresistance behavior. Analysis of the whole genome transcriptome profile showed altered expression of genes residing both within and outside of the duplicated chromosomal segment, suggesting complex phenotypes including PMB resistance can result from tandem amplification events.IMPORTANCEPhenotypic variation in susceptibility and the emergence of resistant subpopulations are major challenges to the clinical use of polymyxins. While a large database of genes and alleles that can confer polymyxin resistance has been compiled, this report demonstrates that the chromosomal insertion sequence (IS) content and distribution warrant consideration as well. Amplification of large chromosomal segments containing the arn operon by IS1 increases the Ara4N content of the lipopolysaccharide layer in Escherichia coli B lineages using a mechanism that is orthogonal to transcriptional upregulation through two-component regulatory systems. Altogether, our work highlights the importance of IS elements in modulating gene expression and generating diverse subpopulations that can contribute to phenotypic polymyxin B heteroresistance.
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Affiliation(s)
- Michael Maybin
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Aditi M Ranade
- The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Ursula Schombel
- Division of Bioanalytical Chemistry, Priority Research Area Infections, Research Center Borstel, Leibniz Lung Center, Borstel, Germany
| | - Nicolas Gisch
- Division of Bioanalytical Chemistry, Priority Research Area Infections, Research Center Borstel, Leibniz Lung Center, Borstel, Germany
| | - Uwe Mamat
- Division of Cellular Microbiology, Priority Research Area Infections, Research Center Borstel, Leibniz Lung Center, Leibniz Research Alliance INFECTIONS, Borstel, Germany
| | - Timothy C Meredith
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
- The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
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2
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Yang Y, Chen H, Corey RA, Morales V, Quentin Y, Froment C, Caumont-Sarcos A, Albenne C, Burlet-Schiltz O, Ranava D, Stansfeld PJ, Marcoux J, Ieva R. LptM promotes oxidative maturation of the lipopolysaccharide translocon by substrate binding mimicry. Nat Commun 2023; 14:6368. [PMID: 37821449 PMCID: PMC10567701 DOI: 10.1038/s41467-023-42007-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 09/27/2023] [Indexed: 10/13/2023] Open
Abstract
Insertion of lipopolysaccharide (LPS) into the bacterial outer membrane (OM) is mediated by a druggable OM translocon consisting of a β-barrel membrane protein, LptD, and a lipoprotein, LptE. The β-barrel assembly machinery (BAM) assembles LptD together with LptE at the OM. In the enterobacterium Escherichia coli, formation of two native disulfide bonds in LptD controls translocon activation. Here we report the discovery of LptM (formerly YifL), a lipoprotein conserved in Enterobacteriaceae, that assembles together with LptD and LptE at the BAM complex. LptM stabilizes a conformation of LptD that can efficiently acquire native disulfide bonds, whereas its inactivation makes disulfide bond isomerization by DsbC become essential for viability. Our structural prediction and biochemical analyses indicate that LptM binds to sites in both LptD and LptE that are proposed to coordinate LPS insertion into the OM. These results suggest that, by mimicking LPS binding, LptM facilitates oxidative maturation of LptD, thereby activating the LPS translocon.
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Affiliation(s)
- Yiying Yang
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Haoxiang Chen
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Robin A Corey
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences Building, Bristol, BS8 1TD, UK
| | - Violette Morales
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Yves Quentin
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Carine Froment
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31077, France
- Infrastructure Nationale de Protéomique, ProFI, FR 2048, Toulouse, France
| | - Anne Caumont-Sarcos
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Cécile Albenne
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Odile Burlet-Schiltz
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31077, France
- Infrastructure Nationale de Protéomique, ProFI, FR 2048, Toulouse, France
| | - David Ranava
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Phillip J Stansfeld
- School of Life Sciences and Department of Chemistry, Gibbet Hill Campus, The University of Warwick, Coventry, CV4 7AL, UK
| | - Julien Marcoux
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31077, France
- Infrastructure Nationale de Protéomique, ProFI, FR 2048, Toulouse, France
| | - Raffaele Ieva
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France.
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3
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Kasimova AA, Shneider MM, Evseev PV, Shelenkov AA, Mikhailova YV, Miroshnikov KA, Chebotar IV, Shagin DA. The structure of Klebsiella pneumoniae K108 capsular polysaccharide is similar to Escherichia coli colanic acid. Int J Biol Macromol 2023:125403. [PMID: 37330077 DOI: 10.1016/j.ijbiomac.2023.125403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 05/02/2023] [Accepted: 06/13/2023] [Indexed: 06/19/2023]
Abstract
The clinical isolate of Klebsiella pneumoniae 1333/P225 was revealed as containing a KL108 K. pneumoniae K locus for capsule biosynthesis. The gene cluster demonstrated a high level of sequence and arrangement similarity with that of the E. coli colanic acid biosynthesis gene cluster. The KL108 gene cluster includes a gene of WcaD polymerase responsible for joining oligosaccharide K units into capsular polysaccharide (CPS), acetyltransferase, pyruvyltransferasefive and genes for glycosyltransferases (Gtrs), four of which have homologues in genetic units of the colanic acid synthesis. The fifth Gtr is specific to this cluster. The work involved the use of sugar analysis, Smith degradation and one- and two-dimensional 1H and 13C NMR spectroscopy to establish the structure of the K108 CPS. The CPS repetitive K unit is composed of branched pentasaccharide with three monosaccharides in the backbone and a disaccharide side chain. The main chain is the same as for colanic acid but the side chain differs. Two bacteriophages infecting K. pneumoniae strain 1333/P225 were isolated and structural depolymerase genes were determined; depolymerases Dep108.1 and Dep108.2 were cloned, expressed and purified. It was demonstrated that both depolymerases specifically cleave the β-Glcp-(1→4)-α-Fucp linkage between K108 units in the CPS.
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Affiliation(s)
- Anastasiya A Kasimova
- N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Science, Moscow, Russia
| | - Mikhail M Shneider
- M.M. Shemyakin and Y.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, Moscow, Russia.
| | - Peter V Evseev
- M.M. Shemyakin and Y.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, Moscow, Russia
| | | | | | - Konstantin A Miroshnikov
- M.M. Shemyakin and Y.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, Moscow, Russia
| | - Igor V Chebotar
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - Dmitry A Shagin
- Pirogov Russian National Research Medical University, Moscow, Russia
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4
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Anderson JR, Lam NB, Jackson JL, Dorenkott SM, Ticer T, Maldosevic E, Velez A, Camden MR, Ellis TN. Progressive Sub-MIC Exposure of Klebsiella pneumoniae 43816 to Cephalothin Induces the Evolution of Beta-Lactam Resistance without Acquisition of Beta-Lactamase Genes. Antibiotics (Basel) 2023; 12:antibiotics12050887. [PMID: 37237790 DOI: 10.3390/antibiotics12050887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 05/01/2023] [Accepted: 05/08/2023] [Indexed: 05/28/2023] Open
Abstract
Bacterial exposure to antibiotic concentrations below the minimum inhibitory concentration (MIC) may result in a selection window allowing for the rapid evolution of resistance. These sub-MIC concentrations are commonly found in soils and water supplies in the greater environment. This study aimed to evaluate the adaptive genetic changes in Klebsiella pneumoniae 43816 after prolonged but increasing sub-MIC levels of the common antibiotic cephalothin over a fourteen-day period. Over the course of the experiment, antibiotic concentrations increased from 0.5 μg/mL to 7.5 μg/mL. At the end of this extended exposure, the final adapted bacterial culture exhibited clinical resistance to both cephalothin and tetracycline, altered cellular and colony morphology, and a highly mucoid phenotype. Cephalothin resistance exceeded 125 μg/mL without the acquisition of beta-lactamase genes. Whole genome sequencing identified a series of genetic changes that could be mapped over the fourteen-day exposure period to the onset of antibiotic resistance. Specifically, mutations in the rpoB subunit of RNA Polymerase, the tetR/acrR regulator, and the wcaJ sugar transferase each fix at specific timepoints in the exposure regimen where the MIC susceptibility dramatically increased. These mutations indicate that alterations in the secretion of colanic acid and attachment of colonic acid to LPS may contribute to the resistant phenotype. These data demonstrate that very low sub-MIC concentrations of antibiotics can have dramatic impacts on the bacterial evolution of resistance. Additionally, this study demonstrates that beta-lactam resistance can be achieved through sequential accumulation of specific mutations without the acquisition of a beta-lactamase gene.
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Affiliation(s)
- Jasmine R Anderson
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
| | - Nghi B Lam
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
| | - Jazmyne L Jackson
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
| | - Sean M Dorenkott
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
| | - Taylor Ticer
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
| | - Emir Maldosevic
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
| | - Amanda Velez
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
| | - Megan R Camden
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
| | - Terri N Ellis
- Department of Biology, University of North Florida, Jacksonville, FL 32224, USA
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5
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Wang Q, Kim H, Halvorsen TM, Chen S, Hayes CS, Buie CR. Leveraging microfluidic dielectrophoresis to distinguish compositional variations of lipopolysaccharide in E. coli. Front Bioeng Biotechnol 2023; 11:991784. [PMID: 36873367 PMCID: PMC9979706 DOI: 10.3389/fbioe.2023.991784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 02/03/2023] [Indexed: 02/18/2023] Open
Abstract
Lipopolysaccharide (LPS) is the unique feature that composes the outer leaflet of the Gram-negative bacterial cell envelope. Variations in LPS structures affect a number of physiological processes, including outer membrane permeability, antimicrobial resistance, recognition by the host immune system, biofilm formation, and interbacterial competition. Rapid characterization of LPS properties is crucial for studying the relationship between these LPS structural changes and bacterial physiology. However, current assessments of LPS structures require LPS extraction and purification followed by cumbersome proteomic analysis. This paper demonstrates one of the first high-throughput and non-invasive strategies to directly distinguish Escherichia coli with different LPS structures. Using a combination of three-dimensional insulator-based dielectrophoresis (3DiDEP) and cell tracking in a linear electrokinetics assay, we elucidate the effect of structural changes in E. coli LPS oligosaccharides on electrokinetic mobility and polarizability. We show that our platform is sufficiently sensitive to detect LPS structural variations at the molecular level. To correlate electrokinetic properties of LPS with the outer membrane permeability, we further examined effects of LPS structural variations on bacterial susceptibility to colistin, an antibiotic known to disrupt the outer membrane by targeting LPS. Our results suggest that microfluidic electrokinetic platforms employing 3DiDEP can be a useful tool for isolating and selecting bacteria based on their LPS glycoforms. Future iterations of these platforms could be leveraged for rapid profiling of pathogens based on their surface LPS structural identity.
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Affiliation(s)
- Qianru Wang
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Hyungseok Kim
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Tiffany M Halvorsen
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Sijie Chen
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Cullen R Buie
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
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6
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Abstract
Chemical synthesis of a hexasaccharide relevant to colanic acid, which bears a high prevalence of polyanionic and acetyl decoration, has been achieved, highlighting stereoselective glycosylation and effective installation of O-acetyl and pyruvate residues.
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Affiliation(s)
- Xin Zhang
- State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Peng Xu
- State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.,School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 1 Sub-lane Xiangshan, Hangzhou 310024, China
| | - Biao Yu
- State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.,School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 1 Sub-lane Xiangshan, Hangzhou 310024, China
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7
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Abstract
Kingella kingae is a leading cause of bone and joint infections and other invasive diseases in young children. A key K. kingae virulence determinant is a secreted exopolysaccharide that mediates resistance to serum complement and neutrophils and is required for full pathogenicity. The K. kingae exopolysaccharide is a galactofuranose homopolymer called galactan and is encoded by the pamABC genes in the pamABCDE locus. In this study, we sought to define the mechanism by which galactan is tethered on the bacterial surface, a prerequisite for mediating evasion of host immune mechanisms. We found that the pamD and pamE genes encode glycosyltransferases and are required for synthesis of an atypical lipopolysaccharide (LPS) O-antigen. The LPS O-antigen in turn is required for anchoring of galactan, a novel mechanism for association of an exopolysaccharide with the bacterial surface.
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8
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The Inactivation of LPS Biosynthesis Genes in E. coli Cells Leads to Oxidative Stress. Cells 2022; 11:cells11172667. [PMID: 36078074 PMCID: PMC9454879 DOI: 10.3390/cells11172667] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 08/22/2022] [Accepted: 08/25/2022] [Indexed: 11/17/2022] Open
Abstract
Impaired lipopolysaccharide biosynthesis in Gram-negative bacteria results in the “deep rough” phenotype, which is characterized by increased sensitivity of cells to various hydrophobic compounds, including antibiotics novobiocin, actinomycin D, erythromycin, etc. The present study showed that E. coli mutants carrying deletions of the ADP-heptose biosynthesis genes became hypersensitive to a wide range of antibacterial drugs: DNA gyrase inhibitors, protein biosynthesis inhibitors (aminoglycosides, tetracycline), RNA polymerase inhibitors (rifampicin), and β-lactams (carbenicillin). In addition, it was found that inactivation of the gmhA, hldE, rfaD, and waaC genes led to dramatic changes in the redox status of cells: a decrease in the pool of reducing NADPH and ATP equivalents, the concentration of intracellular cysteine, a change in thiol homeostasis, and a deficiency in the formation of hydrogen sulfide. In “deep rough” mutants, intensive formation of reactive oxygen species was observed, which, along with a lack of reducing agents, such as reactive sulfur species or NADPH, leads to oxidative stress and an increase in the number of dead cells in the population. Within the framework of modern ideas about the role of oxidative stress as a universal mechanism of the bactericidal action of antibiotics, inhibition of the enzymes of ADP-heptose biosynthesis is a promising direction for increasing the effectiveness of existing antibiotics and solving the problem of multidrug resistance.
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9
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Sande C, Whitfield C. Capsules and Extracellular Polysaccharides in Escherichia coli and Salmonella. EcoSal Plus 2021; 9:eESP00332020. [PMID: 34910576 PMCID: PMC11163842 DOI: 10.1128/ecosalplus.esp-0033-2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Accepted: 10/26/2021] [Indexed: 12/16/2022]
Abstract
Escherichia coli and Salmonella isolates produce a range of different polysaccharide structures that play important roles in their biology. E. coli isolates often possess capsular polysaccharides (K antigens), which form a surface structural layer. These possess a wide range of repeat-unit structures. In contrast, only one capsular polymer (Vi antigen) is found in Salmonella, and it is confined to typhoidal serovars. In both genera, capsules are vital virulence determinants and are associated with the avoidance of host immune defenses. Some isolates of these species also produce a largely secreted exopolysaccharide called colanic acid as part of their complex Rcs-regulated phenotypes, but the precise function of this polysaccharide in microbial cell biology is not fully understood. E. coli isolates produce two additional secreted polysaccharides, bacterial cellulose and poly-N-acetylglucosamine, which play important roles in biofilm formation. Cellulose is also produced by Salmonella isolates, but the genes for poly-N-acetylglucosamine synthesis appear to have been lost during its evolution toward enhanced virulence. Here, we discuss the structures, functions, relationships, and sophisticated assembly mechanisms for these important biopolymers.
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Affiliation(s)
- Caitlin Sande
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Chris Whitfield
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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10
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Reid AJ, Eade CR, Jones KJ, Jorgenson MA, Troutman JM. Tracking Colanic Acid Repeat Unit Formation from Stepwise Biosynthesis Inactivation in Escherichia coli. Biochemistry 2021; 60:2221-2230. [PMID: 34159784 DOI: 10.1021/acs.biochem.1c00314] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Colanic acid is a glycopolymer loosely associated with the outer membrane of Escherichia coli that plays a role in pathogen survival. For nearly six decades since its discovery, the functional identities of the enzymes necessary to synthesize colanic acid have yet to be assessed in full. Herein, we developed a method for detecting the lipid-linked intermediates from each step of colanic acid biosynthesis in E. coli. The accumulation of each enzyme product was made possible by inactivating sequential genes involved in colanic acid biosynthesis and upregulating the colanic acid operon by inducing rcsA transcription. LC-MS analysis revealed that these accumulated materials were consistent with the well-documented composition analysis. Recapitulating the native bioassembly of colanic acid enabled us to identify the functional roles of the last two enzymes, WcaL and WcaK, associated with the formation of the lipid-linked oligosaccharide repeating unit of colanic acid. Importantly, biochemical evidence is provided for the formation of the final glycosylation hexasaccharide product formed by WcaL and the addition of a pyruvate moiety to form a pyruvylated hexasaccharide by WcaK. These findings provide insight into the development of methods for the identification of enzyme functions during cell envelope synthesis.
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Affiliation(s)
| | | | | | - Matthew A Jorgenson
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, Arkansas 72205, United States
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11
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Abstract
By evolving strains of E. coli that hyper-resist sedimentation, we discovered an uncharacterized mechanism that bacteria can use to remain in suspension indefinitely without expending energy. This unusual phenotype was traced to the anchoring of long colanic acid polymers (CAP) that project from the cell surface. Although each characterized mutant activated this same mechanism, the genes responsible and the strengths of the phenotypes varied. Mutations in rcsC, lpp, igaA, or the yjbEFGH operon were sufficient to stimulate sedimentation resistance, while mutations altering the cps promoter, cdgI, or yjbF provided phenotypic enhancements. The sedimentation resistances changed in response to temperature, growth phase, and carbon source and each mutant exhibited significantly reduced biofilm formation. We discovered that the degree of colony mucoidy exhibited by these mutants was not related to the degree of Rcs pathways activation or to the amount of CAP that was produced; rather, it was related to the fraction of CAP that was shed as a true exopolysaccharide. Therefore, these and other mutations that activate this phenotype are likely to be absent from genetic screens that relied on centrifugation to harvest bacteria. We also found that this anchored CAP form is not linked to LPS cores and may not be attached to the outer membrane.IMPORTANCEBacteria can partition in aqueous environments between surface-dwelling, planktonic, sedimentary, and biofilm forms. Residence in each location provides an advantage depending on nutritional and environmental stresses and a community of a single species is often observed to be distributed throughout two or more of these niches. Another adaptive strategy is to produce an extracellular capsule, which provides an environmental shield for the microbe and can allow escape from predators and immune systems. We discovered that bacteria can either shed or stably anchor capsules to dramatically alter their propensity to sediment. The degree to which the bacteria anchor their capsule is controlled by a stress sensing system, suggesting that anchoring may be used as an adaptive response to severe environmental challenges.
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12
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Saha S, Lach SR, Konovalova A. Homeostasis of the Gram-negative cell envelope. Curr Opin Microbiol 2021; 61:99-106. [PMID: 33901778 DOI: 10.1016/j.mib.2021.03.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/23/2021] [Accepted: 03/25/2021] [Indexed: 01/08/2023]
Abstract
The Gram-negative bacterial cell envelope is a complex structure and its homeostasis is essential for bacterial survival. Envelope stress responses (ESRs) are signal transduction pathways that monitor the fidelity of envelope assembly during normal growth and also detect and repair envelope damage caused by external assaults, including immune factors, protein toxins, and antibiotics. In this review, we focus on three best-studied ESRs and discuss the mechanisms by which ESRs detect various perturbations of envelope assembly and integrity and regulate envelope remodeling to promote bacterial survival. We will highlight the complex relationship of ESRs with envelope biogenesis pathways and discuss some of the challenges in this field on the road to mapping the global regulatory network of envelope homeostasis.
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Affiliation(s)
- Shreya Saha
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA
| | - Sarah R Lach
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA; MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, 6767 Bertner Avenue, Houston, TX, 77030, USA
| | - Anna Konovalova
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA.
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13
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Ranjan M, Khokhani D, Nayaka S, Srivastava S, Keyser ZP, Ranjan A. Genomic diversity and organization of complex polysaccharide biosynthesis clusters in the genus Dickeya. PLoS One 2021; 16:e0245727. [PMID: 33571209 PMCID: PMC7877592 DOI: 10.1371/journal.pone.0245727] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 01/07/2021] [Indexed: 11/18/2022] Open
Abstract
The pectinolytic genus Dickeya (formerly Erwinia chrysanthemi) comprises numerous pathogenic species which cause diseases in various crops and ornamental plants across the globe. Their pathogenicity is governed by complex multi-factorial processes of adaptive virulence gene regulation. Extracellular polysaccharides and lipopolysaccharides present on bacterial envelope surface play a significant role in the virulence of phytopathogenic bacteria. However, very little is known about the genomic location, diversity, and organization of the polysaccharide and lipopolysaccharide biosynthetic gene clusters in Dickeya. In the present study, we report the diversity and structural organization of the group 4 capsule (G4C)/O-antigen capsule, putative O-antigen lipopolysaccharide, enterobacterial common antigen, and core lipopolysaccharide biosynthesis clusters from 54 Dickeya strains. The presence of these clusters suggests that Dickeya has both capsule and lipopolysaccharide carrying O-antigen to their external surface. These gene clusters are key regulatory components in the composition and structure of the outer surface of Dickeya. The O-antigen capsule/group 4 capsule (G4C) coding region shows a variation in gene content and organization. Based on nucleotide sequence homology in these Dickeya strains, two distinct groups, G4C group I and G4C group II, exist. However, comparatively less variation is observed in the putative O-antigen lipopolysaccharide cluster in Dickeya spp. except for in Dickeya zeae. Also, enterobacterial common antigen and core lipopolysaccharide biosynthesis clusters are present mostly as conserved genomic regions. The variation in the O-antigen capsule and putative O-antigen lipopolysaccharide coding region in relation to their phylogeny suggests a role of multiple horizontal gene transfer (HGT) events. These multiple HGT processes might have been manifested into the current heterogeneity of O-antigen capsules and O-antigen lipopolysaccharides in Dickeya strains during its evolution.
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Affiliation(s)
- Manish Ranjan
- CSIR-National Botanical Research Institute (CSIR-NBRI), Lucknow, Uttar Pradesh, India
| | - Devanshi Khokhani
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Plant Pathology, University of Minnesota—Twin Cities, St. Paul, Minnesota, United States of America
| | - Sanjeeva Nayaka
- CSIR-National Botanical Research Institute (CSIR-NBRI), Lucknow, Uttar Pradesh, India
| | - Suchi Srivastava
- CSIR-National Botanical Research Institute (CSIR-NBRI), Lucknow, Uttar Pradesh, India
| | - Zachary P. Keyser
- Department of Agronomy, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Ashish Ranjan
- Department of Plant Pathology, University of Minnesota—Twin Cities, St. Paul, Minnesota, United States of America
- Department of Plant Sciences (SLS), University of Hyderabad, Hyderabad, India
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14
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Functions of the BamBCDE Lipoproteins Revealed by Bypass Mutations in BamA. J Bacteriol 2020; 202:JB.00401-20. [PMID: 32817097 DOI: 10.1128/jb.00401-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 08/13/2020] [Indexed: 12/27/2022] Open
Abstract
The heteropentomeric β-barrel assembly machine (BAM complex) is responsible for folding and inserting a diverse array of β-barrel outer membrane proteins (OMPs) into the outer membrane (OM) of Gram-negative bacteria. The BAM complex contains two essential proteins, the β-barrel OMP BamA and a lipoprotein BamD, whereas the auxiliary lipoproteins BamBCE are individually nonessential. Here, we identify and characterize three bamA mutations, the E-to-K change at position 470 (bamAE470K ), the A-to-P change at position 496 (bamAA496P ), and the A-to-S change at position 499 (bamAA499S ), that suppress the otherwise lethal ΔbamD, ΔbamB ΔbamC ΔbamE, and ΔbamC ΔbamD ΔbamE mutations. The viability of cells lacking different combinations of BAM complex lipoproteins provides the opportunity to examine the role of the individual proteins in OMP assembly. Results show that, in wild-type cells, BamBCE share a redundant function; at least one of these lipoproteins must be present to allow BamD to coordinate productively with BamA. Besides BamA regulation, BamD shares an additional essential function that is redundant with a second function of BamB. Remarkably, bamAE470K suppresses both, allowing the construction of a BAM complex composed solely of BamAE470K that is able to assemble OMPs in the absence of BamBCDE. This work demonstrates that the BAM complex lipoproteins do not participate in the catalytic folding of OMP substrates but rather function to increase the efficiency of the assembly process by coordinating and regulating the assembly of diverse OMP substrates.IMPORTANCE The folding and insertion of β-barrel outer membrane proteins (OMPs) are conserved processes in mitochondria, chloroplasts, and Gram-negative bacteria. In Gram-negative bacteria, OMPs are assembled into the outer membrane (OM) by the heteropentomeric β-barrel assembly machine (BAM complex). In this study, we probe the function of the individual BAM proteins and how they coordinate assembly of a diverse family of OMPs. Furthermore, we identify a gain-of-function bamA mutant capable of assembling OMPs independently of all four other BAM proteins. This work advances our understanding of OMP assembly and sheds light on how this process is distinct in Gram-negative bacteria.
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Lundstedt E, Kahne D, Ruiz N. Assembly and Maintenance of Lipids at the Bacterial Outer Membrane. Chem Rev 2020; 121:5098-5123. [PMID: 32955879 DOI: 10.1021/acs.chemrev.0c00587] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The outer membrane of Gram-negative bacteria is essential for their survival in harsh environments and provides intrinsic resistance to many antibiotics. This membrane is remarkable; it is a highly asymmetric lipid bilayer. The inner leaflet of the outer membrane contains phospholipids, whereas the fatty acyl chains attached to lipopolysaccharide (LPS) comprise the hydrophobic portion of the outer leaflet. This lipid asymmetry, and in particular the exclusion of phospholipids from the outer leaflet, is key to creating an almost impenetrable barrier to hydrophobic molecules that can otherwise pass through phospholipid bilayers. It has long been known that these lipids are not made in the outer membrane. It is now believed that conserved multisubunit protein machines extract these lipids after their synthesis is completed at the inner membrane and transport them to the outer membrane. A longstanding question is how the cell builds and maintains this asymmetric lipid bilayer in coordination with the assembly of the other components of the cell envelope. This Review describes the trans-envelope lipid transport systems that have been identified to participate in outer-membrane biogenesis: LPS transport via the Lpt machine, and phospholipid transport via the Mla pathway and several recently proposed transporters.
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Affiliation(s)
- Emily Lundstedt
- Department of Microbiology, The Ohio State University, Columbus, Ohio 43210, United States
| | - Daniel Kahne
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, United States.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Natividad Ruiz
- Department of Microbiology, The Ohio State University, Columbus, Ohio 43210, United States
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Lipopolysaccharide-Linked Enterobacterial Common Antigen (ECA LPS) Occurs in Rough Strains of Escherichia coli R1, R2, and R4. Int J Mol Sci 2020; 21:ijms21176038. [PMID: 32839412 PMCID: PMC7504096 DOI: 10.3390/ijms21176038] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/18/2020] [Accepted: 08/20/2020] [Indexed: 12/26/2022] Open
Abstract
Enterobacterial common antigen (ECA) is a conserved surface antigen characteristic for Enterobacteriaceae. It is consisting of trisaccharide repeating unit, →3)-α-d-Fucp4NAc-(1→4)-β-d-ManpNAcA-(1→4)-α-d-GlcpNAc-(1→, where prevailing forms include ECA linked to phosphatidylglycerol (ECAPG) and cyclic ECA (ECACYC). Lipopolysaccharide (LPS)-associated form (ECALPS) has been proved to date only for rough Shigella sonnei phase II. Depending on the structure organization, ECA constitutes surface antigen (ECAPG and ECALPS) or maintains the outer membrane permeability barrier (ECACYC). The existence of LPS was hypothesized in the 1960–80s on the basis of serological observations. Only a few Escherichia coli strains (i.e., R1, R2, R3, R4, and K-12) have led to the generation of anti-ECA antibodies upon immunization, excluding ECAPG as an immunogen and conjecturing ECALPS as the only immunogenic form. Here, we presented a structural survey of ECALPS in E. coli R1, R2, R3, and R4 to correlate previous serological observations with the presence of ECALPS. The low yields of ECALPS were identified in the R1, R2, and R4 strains, where ECA occupied outer core residues of LPS that used to be substituted by O-specific polysaccharide in the case of smooth LPS. Previously published observations and hypotheses regarding the immunogenicity and biosynthesis of ECALPS were discussed and correlated with presented herein structural data.
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Falchi FA, Di Lorenzo F, Pizzoccheri R, Casino G, Paroni M, Forti F, Molinaro A, Briani F. Overexpression of lpxT Gene in Escherichia coli Inhibits Cell Division and Causes Envelope Defects without Changing the Overall Phosphorylation Level of Lipid A. Microorganisms 2020; 8:E826. [PMID: 32486329 PMCID: PMC7356881 DOI: 10.3390/microorganisms8060826] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 05/27/2020] [Accepted: 05/28/2020] [Indexed: 12/20/2022] Open
Abstract
LpxT is an inner membrane protein that transfers a phosphate group from the essential lipid undecaprenyl pyrophosphate (C-55PP) to the lipid A moiety of lipopolysaccharide, generating a lipid A tris-phosphorylated species. The protein is encoded by the non-essential lpxT gene, which is conserved in distantly related Gram-negative bacteria. In this work, we investigated the phenotypic effect of lpxT ectopic expression from a plasmid in Escherichia coli. We found that lpxT induction inhibited cell division and led to the formation of elongated cells, mostly with absent or altered septa. Moreover, the cells became sensitive to detergents and to hypo-osmotic shock, indicating that they had cell envelope defects. These effects were not due to lipid A hyperphosphorylation or C-55PP sequestering, but most likely to defective lipopolysaccharide transport. Indeed, lpxT overexpression in mutants lacking the L,D-transpeptidase LdtD and LdtE, which protect cells with outer membrane defects from osmotic lysis, caused cell envelope defects. Moreover, we found that pyrophosphorylated lipid A was also produced in a lpxT deletion mutant, indicating that LpxT is not the only protein able to perform such lipid A modification in E. coli.
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Affiliation(s)
- Federica A. Falchi
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milano, Italy; (F.A.F.); (R.P.); (G.C.); (M.P.); (F.F.)
| | - Flaviana Di Lorenzo
- Dipartimento di Scienze Chimiche, Università degli Studi di Napoli Federico II, 80126 Napoli, Italy; (F.D.L.); (A.M.)
| | - Roberto Pizzoccheri
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milano, Italy; (F.A.F.); (R.P.); (G.C.); (M.P.); (F.F.)
| | - Gianluca Casino
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milano, Italy; (F.A.F.); (R.P.); (G.C.); (M.P.); (F.F.)
| | - Moira Paroni
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milano, Italy; (F.A.F.); (R.P.); (G.C.); (M.P.); (F.F.)
| | - Francesca Forti
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milano, Italy; (F.A.F.); (R.P.); (G.C.); (M.P.); (F.F.)
| | - Antonio Molinaro
- Dipartimento di Scienze Chimiche, Università degli Studi di Napoli Federico II, 80126 Napoli, Italy; (F.D.L.); (A.M.)
| | - Federica Briani
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milano, Italy; (F.A.F.); (R.P.); (G.C.); (M.P.); (F.F.)
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YejM Modulates Activity of the YciM/FtsH Protease Complex To Prevent Lethal Accumulation of Lipopolysaccharide. mBio 2020; 11:mBio.00598-20. [PMID: 32291302 PMCID: PMC7157816 DOI: 10.1128/mbio.00598-20] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Gram-negative bacteria are encapsulated by an outer membrane (OM) that is impermeable to large and hydrophobic molecules. As such, these bacteria are intrinsically resistant to several clinically relevant antibiotics. To better understand how the OM is established or maintained, we sought to clarify the function of the essential protein YejM in Escherichia coli. Here, we show that YejM inhibits activity of the YciM/FtsH protease complex, which regulates synthesis of the essential OM glycolipid lipopolysaccharide (LPS). Our data suggest that disrupting proper communication between LPS synthesis and transport to the OM leads to accumulation of LPS within the inner membrane (IM). The lethality associated with this event can be suppressed by increasing OM vesiculation. Our research has identified a completely novel signaling pathway that we propose coordinates LPS synthesis and transport. Lipopolysaccharide (LPS) is an essential glycolipid present in the outer membrane (OM) of many Gram-negative bacteria. Balanced biosynthesis of LPS is critical for cell viability; too little LPS weakens the OM, while too much LPS is lethal. In Escherichia coli, this balance is maintained by the YciM/FtsH protease complex, which adjusts LPS levels by degrading the LPS biosynthesis enzyme LpxC. Here, we provide evidence that activity of the YciM/FtsH protease complex is inhibited by the essential protein YejM. Using strains in which LpxC activity is reduced, we show that yciM is epistatic to yejM, demonstrating that YejM acts upstream of YciM to prevent toxic overproduction of LPS. Previous studies have shown that this toxicity can be suppressed by deleting lpp, which codes for a highly abundant OM lipoprotein. It was assumed that deletion of lpp restores lipid balance by increasing the number of acyl chains available for glycerophospholipid biosynthesis. We show that this is not the case. Rather, our data suggest that preventing attachment of lpp to the peptidoglycan sacculus allows excess LPS to be shed in vesicles. We propose that this loss of OM material allows continued transport of LPS to the OM, thus preventing lethal accumulation of LPS within the inner membrane. Overall, our data justify the commitment of three essential inner membrane proteins to avoid toxic over- or underproduction of LPS.
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19
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Hager FF, Sützl L, Stefanović C, Blaukopf M, Schäffer C. Pyruvate Substitutions on Glycoconjugates. Int J Mol Sci 2019; 20:E4929. [PMID: 31590345 PMCID: PMC6801904 DOI: 10.3390/ijms20194929] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 09/25/2019] [Accepted: 09/27/2019] [Indexed: 12/15/2022] Open
Abstract
Glycoconjugates are the most diverse biomolecules of life. Mostly located at the cell surface, they translate into cell-specific "barcodes" and offer a vast repertoire of functions, including support of cellular physiology, lifestyle, and pathogenicity. Functions can be fine-tuned by non-carbohydrate modifications on the constituting monosaccharides. Among these modifications is pyruvylation, which is present either in enol or ketal form. The most commonly best-understood example of pyruvylation is enol-pyruvylation of N-acetylglucosamine, which occurs at an early stage in the biosynthesis of the bacterial cell wall component peptidoglycan. Ketal-pyruvylation, in contrast, is present in diverse classes of glycoconjugates, from bacteria to algae to yeast-but not in humans. Mild purification strategies preventing the loss of the acid-labile ketal-pyruvyl group have led to a collection of elucidated pyruvylated glycan structures. However, knowledge of involved pyruvyltransferases creating a ring structure on various monosaccharides is scarce, mainly due to the lack of knowledge of fingerprint motifs of these enzymes and the unavailability of genome sequences of the organisms undergoing pyruvylation. This review compiles the current information on the widespread but under-investigated ketal-pyruvylation of monosaccharides, starting with different classes of pyruvylated glycoconjugates and associated functions, leading to pyruvyltransferases, their specificity and sequence space, and insight into pyruvate analytics.
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Affiliation(s)
- Fiona F Hager
- Department of NanoBiotechnology, NanoGlycobiology unit, Universität für Bodenkultur Wien, Muthgasse 11, A-1190 Vienna, Austria.
| | - Leander Sützl
- Department of Food Science and Technology, Food Biotechnology Laboratory, Muthgasse 11, Universität für Bodenkultur Wien, A-1190 Vienna, Austria.
| | - Cordula Stefanović
- Department of NanoBiotechnology, NanoGlycobiology unit, Universität für Bodenkultur Wien, Muthgasse 11, A-1190 Vienna, Austria.
| | - Markus Blaukopf
- Department of Chemistry, Division of Organic Chemistry, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Vienna, Austria.
| | - Christina Schäffer
- Department of NanoBiotechnology, NanoGlycobiology unit, Universität für Bodenkultur Wien, Muthgasse 11, A-1190 Vienna, Austria.
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20
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Pal S, Verma J, Mallick S, Rastogi SK, Kumar A, Ghosh AS. Absence of the glycosyltransferase WcaJ in Klebsiella pneumoniae ATCC13883 affects biofilm formation, increases polymyxin resistance and reduces murine macrophage activation. Microbiology (Reading) 2019; 165:891-904. [PMID: 31246167 DOI: 10.1099/mic.0.000827] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Shilpa Pal
- Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal-721302, India
| | - Jyoti Verma
- Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, West Bengal-721302, India
| | - Sathi Mallick
- Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal-721302, India
| | - Sumit Kumar Rastogi
- Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal-721302, India
| | - Akash Kumar
- Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal-721302, India
| | - Anindya S. Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal-721302, India
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21
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Islam R, Brown S, Taheri A, Dumenyo CK. The Gene Encoding NAD-Dependent Epimerase/Dehydratase, wcaG, Affects Cell Surface Properties, Virulence, and Extracellular Enzyme Production in the Soft Rot Phytopathogen, Pectobacterium carotovorum. Microorganisms 2019; 7:microorganisms7060172. [PMID: 31200539 PMCID: PMC6616942 DOI: 10.3390/microorganisms7060172] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 06/03/2019] [Accepted: 06/06/2019] [Indexed: 01/03/2023] Open
Abstract
Pectobacterium carotovorum is a gram-negative bacterium that, together with other soft rot Enterobacteriaceae causes soft rot disease in vegetables, fruits, and ornamental plants through the action of exoproteins including plant cell wall-degrading enzymes (PCWDEs). Although pathogenicity in these bacteria is complex, virulence levels are proportional to the levels of plant cell wall-degrading exoenzymes (PCWDEs) secreted. Two low enzyme-producing transposon Tn5 mutants were isolated, and compared to their parent KD100, the mutants were less virulent on celery petioles and carrot disks. The inactivated gene responsible for the reduced virulence phenotype in both mutants was identified as wcaG. The gene, wcaG (previously denoted fcl) encodes NAD-dependent epimerase/dehydratase, a homologue of GDP-fucose synthetase of Escherichia coli. In Escherichia coli, GDP-fucose synthetase is involved in the biosynthesis of the exopolysaccharide, colanic acid (CA). The wcaG mutants of P. carotovorum formed an enhanced level of biofilm in comparison to their parent. In the hydrophobicity test the mutants showed more hydrophobicity than the parent in hexane and hexadecane as solvents. Complementation of the mutants with extrachromosomal copies of the wild type gene restored these functions to parental levels. These data indicate that NAD-dependent epimerase/dehydratase plays a vital rule in cell surface properties, exoenzyme production, and virulence in P. carotovorum.
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Affiliation(s)
- Rabiul Islam
- Department of Agricultural and Environmental Sciences, Tennessee State University, 3500 John A. Merritt Blvd; Box 9543, Nashville, TN 37209, USA.
| | - Shyretha Brown
- Department of Agricultural and Environmental Sciences, Tennessee State University, 3500 John A. Merritt Blvd; Box 9543, Nashville, TN 37209, USA.
| | - Ali Taheri
- Department of Agricultural and Environmental Sciences, Tennessee State University, 3500 John A. Merritt Blvd; Box 9543, Nashville, TN 37209, USA.
| | - C Korsi Dumenyo
- Department of Agricultural and Environmental Sciences, Tennessee State University, 3500 John A. Merritt Blvd; Box 9543, Nashville, TN 37209, USA.
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Abstract
The cell envelope is the first line of defense between a bacterium and the world-at-large. Often, the initial steps that determine the outcome of chemical warfare, bacteriophage infections, and battles with other bacteria or the immune system greatly depend on the structure and composition of the bacterial cell surface. One of the most studied bacterial surface molecules is the glycolipid known as lipopolysaccharide (LPS), which is produced by most Gram-negative bacteria. Much of the initial attention LPS received in the early 1900s was owed to its ability to stimulate the immune system, for which the glycolipid was commonly known as endotoxin. It was later discovered that LPS also creates a permeability barrier at the cell surface and is a main contributor to the innate resistance that Gram-negative bacteria display against many antimicrobials. Not surprisingly, these important properties of LPS have driven a vast and still prolific body of literature for more than a hundred years. LPS research has also led to pioneering studies in bacterial envelope biogenesis and physiology, mostly using Escherichia coli and Salmonella as model systems. In this review, we will focus on the fundamental knowledge we have gained from studies of the complex structure of the LPS molecule and the biochemical pathways for its synthesis, as well as the transport of LPS across the bacterial envelope and its assembly at the cell surface.
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Scott PM, Erickson KM, Troutman JM. Identification of the Functional Roles of Six Key Proteins in the Biosynthesis of Enterobacteriaceae Colanic Acid. Biochemistry 2019; 58:1818-1830. [PMID: 30821147 DOI: 10.1021/acs.biochem.9b00040] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
When subjected to harsh conditions such as low pH, pathogenic Escherichia coli can secrete colanic acid to establish a protective barrier between the organism and the acidic environment. The colanic acid consists of a six-sugar repeating unit polymer comprised of glucose, fucose, galactose, and glucuronic acid. The region of the E. coli genome that encodes colanic acid biosynthesis has been reported, and the first enzyme in the biosynthesis pathway has been biochemically characterized. However, the specific roles of the remaining genes required for colanic acid biosynthesis have not been identified. Here we report the in vitro reconstitution of the next six steps in the assembly of the colanic acid repeating unit. To do this, we have cloned and overexpressed each gene within the colanic acid biosynthesis operon. We then tested the activity of the protein product of these genes using high-performance liquid chromatography analysis and a fluorescent analogue of the isoprenoid anchor bactoprenyl diphospho-glucose as a starting substrate. To ensure that retention time changes were associated with varying sugar additions or modifications, we developed a liquid chromatography-mass spectrometry method for analysis of the products produced by each enzyme. We have identified the function of all but one encoded glycosyltransferase and have identified the function of two acetyltransferases. This work demonstrates the centrality of acetylation in the biosynthesis of colanic acid and provides insight into the activity of key proteins involved in the production of an important and highly conserved bacterial glycopolymer.
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Kim H, Kim M, Bai J, Lim JA, Heu S, Ryu S. Colanic Acid Is a Novel Phage Receptor of Pectobacterium carotovorum subsp. carotovorum Phage POP72. Front Microbiol 2019; 10:143. [PMID: 30837957 PMCID: PMC6390001 DOI: 10.3389/fmicb.2019.00143] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 01/21/2019] [Indexed: 12/17/2022] Open
Abstract
The emergence and widespread nature of pathogen resistance to antibiotics and chemicals has led to the re-consideration of bacteriophages as an alternative biocontrol agent in several fields, including agriculture. In this study, we isolated and characterized a novel bacteriophage, POP72, that specifically infects Pectobacterium carotovorum subsp. carotovorum (Pcc), which frequently macerates agricultural crops. POP72 contains a 44,760 bp double-stranded DNA genome and belongs to the family Podoviridae. To determine the phage receptor for POP72, a random mutant library of Pcc was constructed using a Tn5 transposon and screened for resistance against POP72 infection. Most of the resistant clones had a Tn5 insertion in various genes associated with colanic acid (CA) biosynthesis. The phage adsorption rate and CA production decreased dramatically in the resistant clones. Complementation of the clones with the pUHE21-2 lacI q vector harboring genes associated with CA biosynthesis restored their sensitivity to POP72, as well as their ability to produce CA. These results suggest that CA functions as a novel phage receptor for POP72. The application of POP72 protected Chinese cabbage from Pcc infection, suggesting that phage POP72 would be an effective alternative antimicrobial agent to protect agricultural products from Pcc.
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Affiliation(s)
- Hyeongsoon Kim
- Department of Agricultural Biotechnology, Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
| | - Minsik Kim
- Department of Food and Nutrition, College of Human Ecology, Yonsei University, Seoul, South Korea
| | - Jaewoo Bai
- Department of Agricultural Biotechnology, Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
| | - Jeong-A Lim
- Research Group of Food Safety, Korea Food Research Institute, Seongnam, South Korea
| | - Sunggi Heu
- Crop Cultivation and Environmental Research Division, National Institute of Crop Science, Suwon, South Korea
| | - Sangryeol Ryu
- Department of Agricultural Biotechnology, Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea.,Center for Food and Bioconvergence, Seoul National University, Seoul, South Korea
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Current Progress in the Structural and Biochemical Characterization of Proteins Involved in the Assembly of Lipopolysaccharide. Int J Microbiol 2018; 2018:5319146. [PMID: 30595696 PMCID: PMC6286764 DOI: 10.1155/2018/5319146] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 10/29/2018] [Indexed: 12/25/2022] Open
Abstract
The lipid component of the outer leaflet of the outer membrane of Gram-negative bacteria is primarily composed of the glycolipid lipopolysaccharide (LPS), which serves to form a protective barrier against hydrophobic toxins and many antibiotics. LPS is comprised of three regions: the lipid A membrane anchor, the nonrepeating core oligosaccharide, and the repeating O-antigen polysaccharide. The lipid A portion is also referred to as endotoxin as its overstimulation of the toll-like receptor 4 during systemic infection precipitates potentially fatal septic shock. Because of the importance of LPS for the viability and virulence of human pathogens, understanding how LPS is synthesized and transported to the outer leaflet of the outer membrane is important for developing novel antibiotics to combat resistant Gram-negative strains. The following review describes the current state of our understanding of the proteins responsible for the synthesis and transport of LPS with an emphasis on the contribution of protein structures to our understanding of their functions. Because the lipid A portion of LPS is relatively well conserved, a detailed description of the biosynthetic enzymes in the Raetz pathway of lipid A synthesis is provided. Conversely, less well-conserved biosynthetic enzymes later in LPS synthesis are described primarily to demonstrate conserved principles of LPS synthesis. Finally, the conserved LPS transport systems are described in detail.
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Mychack A, Amrutha RN, Chung C, Cardenas Arevalo K, Reddy M, Janakiraman A. A synergistic role for two predicted inner membrane proteins of Escherichia coli in cell envelope integrity. Mol Microbiol 2018; 111:317-337. [PMID: 30368949 DOI: 10.1111/mmi.14157] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/22/2018] [Indexed: 01/21/2023]
Abstract
The bacterial cytoplasmic membrane is a principal site of protein translocation, lipid and peptidoglycan biogenesis, signal transduction, transporters and energy generating components of the respiratory chain. Although 25-30% of bacterial proteomes consist of membrane proteins, a comprehensive understanding of their influence on fundamental cellular processes is incomplete. Here, we show that YciB and DcrB, two small cytoplasmic membrane proteins of previously unknown functions, play an essential synergistic role in maintaining cell envelope integrity of Escherichia coli. Lack of both YciB and DcrB results in pleiotropic cell defects including increased levels of lipopolysaccharide, membrane vesiculation, dynamic shrinking and extension of the cytoplasmic membrane accompanied by lysis and cell death. The stalling of an abundant outer membrane lipoprotein, Lpp, at the periplasmic face of the inner membrane leads to lethal inner membrane-peptidoglycan linkages. Additionally, the periplasmic chaperone Skp contributes to yciB dcrB mutant cell death by possibly mistargeting stalled porins into the inner membrane. Consistent with the idea of a compromised envelope in the yciB dcrB mutant, multiple envelope stress response systems are induced, with Cpx signal transduction being required for growth. Taken together, our results suggest a fundamental role for YciB and DcrB in cell envelope biogenesis.
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Affiliation(s)
- Aaron Mychack
- Department of Biology, The City College of CUNY, New York, NY, 10031, USA.,Program in Biology, The Graduate Center, CUNY, Fifth Avenue, New York, NY, 10016, USA
| | - R N Amrutha
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, 500007, India
| | - Charlie Chung
- Department of Biology, The City College of CUNY, New York, NY, 10031, USA
| | | | - Manjula Reddy
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, 500007, India
| | - Anuradha Janakiraman
- Department of Biology, The City College of CUNY, New York, NY, 10031, USA.,Program in Biology, The Graduate Center, CUNY, Fifth Avenue, New York, NY, 10016, USA
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Peng Y, Tang S, Wang D, Zhong H, Jia H, Cai X, Zhang Z, Xiao M, Yang H, Wang J, Kristiansen K, Xu X, Li J. MetaPGN: a pipeline for construction and graphical visualization of annotated pangenome networks. Gigascience 2018; 7:5114262. [PMID: 30277499 PMCID: PMC6251982 DOI: 10.1093/gigascience/giy121] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 09/20/2018] [Indexed: 02/01/2023] Open
Abstract
Pangenome analyses facilitate the interpretation of genetic diversity and evolutionary history of a taxon. However, there is an urgent and unmet need to develop new tools for advanced pangenome construction and visualization, especially for metagenomic data. Here, we present an integrated pipeline, named MetaPGN, for construction and graphical visualization of pangenome networks from either microbial genomes or metagenomes. Given either isolated genomes or metagenomic assemblies coupled with a reference genome of the targeted taxon, MetaPGN generates a pangenome in a topological network, consisting of genes (nodes) and gene-gene genomic adjacencies (edges) of which biological information can be easily updated and retrieved. MetaPGN also includes a self-developed Cytoscape plugin for layout of and interaction with the resulting pangenome network, providing an intuitive and interactive interface for full exploration of genetic diversity. We demonstrate the utility of MetaPGN by constructing Escherichia coli pangenome networks from five E. coli pathogenic strains and 760 human gut microbiomes,revealing extensive genetic diversity of E. coli within both isolates and gut microbial populations. With the ability to extract and visualize gene contents and gene-gene physical adjacencies of a specific taxon from large-scale metagenomic data, MetaPGN provides advantages in expanding pangenome analysis to uncultured microbial taxa.
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Affiliation(s)
- Ye Peng
- School of Biology and Biological Engineering, South China University of Technology, Building B6, 382 Zhonghuan Road East, Guangzhou Higher Education Mega Center, Guangzhou 510006, China.,BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China
| | - Shanmei Tang
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China.,Shenzhen Key Laboratory of Human commensal microorganisms and Health Research, BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China
| | - Dan Wang
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China.,Shenzhen Key Laboratory of Human commensal microorganisms and Health Research, BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China
| | - Huanzi Zhong
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China.,Shenzhen Key Laboratory of Human commensal microorganisms and Health Research, BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,Laboratory of Genomics and Molecular Biomedicine, Department of Biology, University of Copenhagen, Copenhagen Biocenter, Ole MaalØes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Huijue Jia
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China.,Shenzhen Key Laboratory of Human commensal microorganisms and Health Research, BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China
| | - Xianghang Cai
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China
| | - Zhaoxi Zhang
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China
| | - Minfeng Xiao
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China
| | - Huanming Yang
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,James D. Watson Institute of Genome Sciences, No. 51, Zhijiang Road, Xihu District, Hangzhou 310058, China
| | - Jian Wang
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,James D. Watson Institute of Genome Sciences, No. 51, Zhijiang Road, Xihu District, Hangzhou 310058, China
| | - Karsten Kristiansen
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China.,Laboratory of Genomics and Molecular Biomedicine, Department of Biology, University of Copenhagen, Copenhagen Biocenter, Ole MaalØes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Xun Xu
- BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China
| | - Junhua Li
- School of Biology and Biological Engineering, South China University of Technology, Building B6, 382 Zhonghuan Road East, Guangzhou Higher Education Mega Center, Guangzhou 510006, China.,BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China.,China National GeneBank, BGI-Shenzhen, Dapeng New District, Shenzhen 518120, China.,Shenzhen Key Laboratory of Human commensal microorganisms and Health Research, BGI-Shenzhen, Building 11, Beishan Industrial Zone, Yantian, Shenzhen 518083, China
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Benforte FC, Colonnella MA, Ricardi MM, Solar Venero EC, Lizarraga L, López NI, Tribelli PM. Novel role of the LPS core glycosyltransferase WapH for cold adaptation in the Antarctic bacterium Pseudomonas extremaustralis. PLoS One 2018; 13:e0192559. [PMID: 29415056 PMCID: PMC5802925 DOI: 10.1371/journal.pone.0192559] [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: 10/29/2017] [Accepted: 01/25/2018] [Indexed: 11/19/2022] Open
Abstract
Psychrotroph microorganisms have developed cellular mechanisms to cope with cold stress. Cell envelopes are key components for bacterial survival. Outer membrane is a constituent of Gram negative bacterial envelopes, consisting of several components, such as lipopolysaccharides (LPS). In this work we investigated the relevance of envelope characteristics for cold adaptation in the Antarctic bacterium Pseudomonas extremaustralis by analyzing a mini Tn5 wapH mutant strain, encoding a core LPS glycosyltransferase. Our results showed that wapH strain is impaired to grow under low temperature but not for cold survival. The mutation in wapH, provoked a strong aggregative phenotype and modifications of envelope nanomechanical properties such as lower flexibility and higher turgor pressure, cell permeability and surface area to volume ratio (S/V). Changes in these characteristics were also observed in the wild type strain grown at different temperatures, showing higher cell flexibility but lower turgor pressure under cold conditions. Cold shock experiments indicated that an acclimation period in the wild type is necessary for cell flexibility and S/V ratio adjustments. Alteration in cell-cell interaction capabilities was observed in wapH strain. Mixed cells of wild type and wapH strains, as well as those of the wild type strain grown at different temperatures, showed a mosaic pattern of aggregation. These results indicate that wapH mutation provoked marked envelope alterations showing that LPS core conservation appears as a novel essential feature for active growth under cold conditions.
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Affiliation(s)
- Florencia C. Benforte
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Maria A. Colonnella
- Centro de Investigaciones en Bionanociencias, CONICET, Buenos Aires, Argentina
| | - Martiniano M. Ricardi
- Instituto de Fisiología, Biología Molecular y Neurociencias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | | | - Leonardo Lizarraga
- Centro de Investigaciones en Bionanociencias, CONICET, Buenos Aires, Argentina
| | - Nancy I. López
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- IQUIBICEN, CONICET, Buenos Aires, Argentina
- * E-mail: (NIL); (PMT)
| | - Paula M. Tribelli
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- IQUIBICEN, CONICET, Buenos Aires, Argentina
- * E-mail: (NIL); (PMT)
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29
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Effects of Lipopolysaccharide Core Sugar Deficiency on Colanic Acid Biosynthesis in Escherichia coli. J Bacteriol 2016; 198:1576-1584. [PMID: 27002133 DOI: 10.1128/jb.00094-16] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 03/12/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED When 10 Escherichia coli mutant strains with defects in lipopolysaccharide (LPS) core biosynthesis were grown on agar medium at 30°C, four of them, the ΔwaaF, ΔwaaG, ΔwaaP, and ΔwaaB strains, formed mucoid colonies, while the other six, the ΔwaaU, ΔwaaR, ΔwaaO, ΔwaaC, ΔwaaQ, and ΔwaaY strains, did not. Using light microscopy with tannin mordant staining, the presence of exopolysaccharide around the cells of the mutants that formed mucoid colonies could be discerned. The ΔwaaF mutant produced the largest amounts of exopolysaccharide, regardless of whether it was grown on agar or in liquid medium. The exopolysaccharide was isolated from the liquid growth medium of ΔwaaF cells, hydrolyzed, and analyzed by high-performance liquid chromatography with an ion-exchange column, and the results indicated that the exopolysaccharide was consistent with colanic acid. When the key genes related to the biosynthesis of colanic acid, i.e., wza, wzb, wzc, and wcaA, were deleted in the ΔwaaF background, the exopolysaccharide could not be produced any more, further confirming that it was colanic acid. Colanic acid could not be produced in strains in which rcsA, rcsB, rcsD, or rcsF was deleted in the ΔwaaF background, but a reduced level of colanic acid production was detected when the rcsC gene was deleted, suggesting that a change of lipopolysaccharide structure in ΔwaaF cells might be sensed by the RcsCDB phosphorelay system, leading to the production of colanic acid. The results demonstrate that E. coli cells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural deficiency of lipopolysaccharide. IMPORTANCE Lipopolysaccharide and colanic acid are important forms of exopolysaccharide for Escherichia coli cells. Their metabolism and biological significance have been investigated, but their interrelation with the cell stress response process is not understood. This study demonstrates, for the first time, that E. coli cells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural change of lipopolysaccharide, suggesting that bacterial cells can monitor the outer membrane integrity, which is essential for cell survival and damage repair.
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30
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Regulated Control of the Assembly and Diversity of LPS by Noncoding sRNAs. BIOMED RESEARCH INTERNATIONAL 2015; 2015:153561. [PMID: 26618164 PMCID: PMC4651636 DOI: 10.1155/2015/153561] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/07/2015] [Accepted: 10/13/2015] [Indexed: 01/31/2023]
Abstract
The outer membrane (OM) of Gram-negative bacteria is asymmetric due to the presence of lipopolysaccharide (LPS) facing the outer leaflet of the OM and phospholipids facing the periplasmic side. LPS is essential for bacterial viability, since it provides a permeability barrier and is a major virulence determinant in pathogenic bacteria. In Escherichia coli, several steps of LPS biosynthesis and assembly are regulated by the RpoE sigma factor and stress responsive two-component systems as well as dedicated small RNAs. LPS composition is highly heterogeneous and dynamically altered upon stress and other challenges in the environment because of the transcriptional activation of RpoE regulon members and posttranslational control by RpoE-regulated Hfq-dependent RybB and MicA sRNAs. The PhoP/Q two-component system further regulates Kdo2-lipid A modification via MgrR sRNA. Some of these structural alterations are critical for antibiotic resistance, OM integrity, virulence, survival in host, and adaptation to specific environmental niches. The heterogeneity arises following the incorporation of nonstoichiometric modifications in the lipid A part and alterations in the composition of inner and outer core of LPS. The biosynthesis of LPS and phospholipids is tightly coupled. This requires the availability of metabolic precursors, whose accumulation is controlled by sRNAs like SlrA, GlmZ, and GlmY.
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31
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Putker F, Bos MP, Tommassen J. Transport of lipopolysaccharide to the Gram-negative bacterial cell surface. FEMS Microbiol Rev 2015; 39:985-1002. [DOI: 10.1093/femsre/fuv026] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/05/2015] [Indexed: 12/15/2022] Open
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32
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Mamat U, Wilke K, Bramhill D, Schromm AB, Lindner B, Kohl TA, Corchero JL, Villaverde A, Schaffer L, Head SR, Souvignier C, Meredith TC, Woodard RW. Detoxifying Escherichia coli for endotoxin-free production of recombinant proteins. Microb Cell Fact 2015; 14:57. [PMID: 25890161 PMCID: PMC4404585 DOI: 10.1186/s12934-015-0241-5] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 04/07/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Lipopolysaccharide (LPS), also referred to as endotoxin, is the major constituent of the outer leaflet of the outer membrane of virtually all Gram-negative bacteria. The lipid A moiety, which anchors the LPS molecule to the outer membrane, acts as a potent agonist for Toll-like receptor 4/myeloid differentiation factor 2-mediated pro-inflammatory activity in mammals and, thus, represents the endotoxic principle of LPS. Recombinant proteins, commonly manufactured in Escherichia coli, are generally contaminated with endotoxin. Removal of bacterial endotoxin from recombinant therapeutic proteins is a challenging and expensive process that has been necessary to ensure the safety of the final product. RESULTS As an alternative strategy for common endotoxin removal methods, we have developed a series of E. coli strains that are able to grow and express recombinant proteins with the endotoxin precursor lipid IVA as the only LPS-related molecule in their outer membranes. Lipid IVA does not trigger an endotoxic response in humans typical of bacterial LPS chemotypes. Hence the engineered cells themselves, and the purified proteins expressed within these cells display extremely low endotoxin levels. CONCLUSIONS This paper describes the preparation and characterization of endotoxin-free E. coli strains, and demonstrates the direct production of recombinant proteins with negligible endotoxin contamination.
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Affiliation(s)
- Uwe Mamat
- Division of Structural Biochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 1-40, D-23845, Borstel, Germany.
| | - Kathleen Wilke
- Division of Structural Biochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 1-40, D-23845, Borstel, Germany.
| | - David Bramhill
- Research Corporation Technologies, Inc, 5210 East Williams Circle, Suite 240, Tucson, AZ, 85711-4410, USA. .,Present address: Bramhill Biological Consulting, LLC, 8240 East Moonstone Drive, Tucson, AZ, 85750, USA.
| | - Andra Beate Schromm
- Division of Immunobiophysics, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 1-40, D-23845, Borstel, Germany.
| | - Buko Lindner
- Division of Bioanalytical Chemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 1-40, D-23845, Borstel, Germany.
| | - Thomas Andreas Kohl
- Division of Molecular Mycobacteriology, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 1-40, D-23845, Borstel, Germany.
| | - José Luis Corchero
- CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, 08193, Cerdanyola del Vallès, Spain. .,Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, 08193, Cerdanyola del Vallès, Spain. .,Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193, Cerdanyola del Vallès, Spain.
| | - Antonio Villaverde
- CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, 08193, Cerdanyola del Vallès, Spain. .,Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, 08193, Cerdanyola del Vallès, Spain. .,Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193, Cerdanyola del Vallès, Spain.
| | - Lana Schaffer
- NGS and Microarray Core Facility, The Scripps Research Institute, 10550 North, Pines Road, La Jolla, Torrey, CA, 92037, USA.
| | - Steven Robert Head
- NGS and Microarray Core Facility, The Scripps Research Institute, 10550 North, Pines Road, La Jolla, Torrey, CA, 92037, USA.
| | - Chad Souvignier
- Research Corporation Technologies, Inc, 5210 East Williams Circle, Suite 240, Tucson, AZ, 85711-4410, USA.
| | - Timothy Charles Meredith
- Department of Biochemistry and Molecular Biology, 206 South Frear, Pennsylvania State University, University Park, PA, 16802, USA.
| | - Ronald Wesley Woodard
- Department of Medicinal Chemistry, University of Michigan, 428 Church Street, Ann Arbor, MI, 48109-1065, USA.
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33
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Furlong SE, Ford A, Albarnez-Rodriguez L, Valvano MA. Topological analysis of the Escherichia coli WcaJ protein reveals a new conserved configuration for the polyisoprenyl-phosphate hexose-1-phosphate transferase family. Sci Rep 2015; 5:9178. [PMID: 25776537 PMCID: PMC4361858 DOI: 10.1038/srep09178] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 02/24/2015] [Indexed: 11/25/2022] Open
Abstract
WcaJ is an Escherichia coli membrane enzyme catalysing the biosynthesis of undecaprenyl-diphosphate-glucose, the first step in the assembly of colanic acid exopolysaccharide. WcaJ belongs to a large family of polyisoprenyl-phosphate hexose-1-phosphate transferases (PHPTs) sharing a similar predicted topology consisting of an N-terminal domain containing four transmembrane helices (TMHs), a large central periplasmic loop, and a C-terminal domain containing the fifth TMH (TMH-V) and a cytosolic tail. However, the topology of PHPTs has not been experimentally validated. Here, we investigated the topology of WcaJ using a combination of LacZ/PhoA reporter fusions and sulfhydryl labelling by PEGylation of novel cysteine residues introduced into a cysteine-less WcaJ. The results showed that the large central loop and the C-terminal tail both reside in the cytoplasm and are separated by TMH-V, which does not fully span the membrane, likely forming a "hairpin" structure. Modelling of TMH-V revealed that a highly conserved proline might contribute to a helix-break-helix structure in all PHPT members. Bioinformatic analyses show that all of these features are conserved in PHPT homologues from Gram-negative and Gram-positive bacteria. Our data demonstrate a novel topological configuration for PHPTs, which is proposed as a signature for all members of this enzyme family.
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Affiliation(s)
- Sarah E. Furlong
- Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Amy Ford
- Centre for Infection and Immunity, Queen's University Belfast, Belfast, United Kingdom, BT9 7AE
| | - Lorena Albarnez-Rodriguez
- Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Miguel A. Valvano
- Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, N6A 5C1, Canada
- Centre for Infection and Immunity, Queen's University Belfast, Belfast, United Kingdom, BT9 7AE
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34
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Grabowicz M, Andres D, Lebar MD, Malojčić G, Kahne D, Silhavy TJ. A mutant Escherichia coli that attaches peptidoglycan to lipopolysaccharide and displays cell wall on its surface. eLife 2014; 3:e05334. [PMID: 25551294 PMCID: PMC4296511 DOI: 10.7554/elife.05334] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 12/24/2014] [Indexed: 12/03/2022] Open
Abstract
The lipopolysaccharide (LPS) forms the surface-exposed leaflet of the outer membrane (OM) of Gram-negative bacteria, an organelle that shields the underlying peptidoglycan (PG) cell wall. Both LPS and PG are essential cell envelope components that are synthesized independently and assembled by dedicated transenvelope multiprotein complexes. We have identified a point-mutation in the gene for O-antigen ligase (WaaL) in Escherichia coli that causes LPS to be modified with PG subunits, intersecting these two pathways. Synthesis of the PG-modified LPS (LPS*) requires ready access to the small PG precursor pool but does not weaken cell wall integrity, challenging models of precursor sequestration at PG assembly machinery. LPS* is efficiently transported to the cell surface without impairing OM function. Because LPS* contains the canonical vancomycin binding site, these surface-exposed molecules confer increased vancomycin-resistance by functioning as molecular decoys that titrate the antibiotic away from its intracellular target. This unexpected LPS glycosylation fuses two potent pathogen-associated molecular patterns (PAMPs). DOI:http://dx.doi.org/10.7554/eLife.05334.001 Tiny Gram-negative bacteria are one of humankind's deadliest foes, causing infections of wounds and the bloodstream that are very hard to treat. Many Gram-negative bacteria are resistant to several common antibiotics, and the few treatments available that can successfully kill the bacteria are often also toxic to the patients. Understanding how these bacteria elude antibiotics could help scientists develop better, less toxic treatments. Most bacteria are surrounded by a cell wall that helps protect the bacteria and gives them structure. Many broad-spectrum antibiotics, including penicillin and vancomycin, work by interfering with how this protective wall is built from molecules called peptidoglycans. However, Gram-negative bacteria have an outer membrane that prevents many antibiotics from reaching the cell wall, and so the antibiotics are unable to kill the bacteria. The outer membrane of Gram-negative bacteria is made up of sugars and fatty molecules called lipids. Recently, scientists discovered a mutation that interferes with the movement of the lipid and sugar molecules that make up the outer membrane, which compromises this protective layer and makes the bacteria more susceptible to antibiotics. To learn more about how this mutation interferes with the defenses of the Gram-negative bacteria Escherichia coli, Grabowicz et al. searched for compensating mutations that can counteract it and restore the antibiotic resistance of these mutant bacteria. The search revealed that a mutation in a gene called waaL increases E. coli's resistance to vancomycin, but not to other antibiotics. The gene encodes an enzyme, and the mutant form of the enzyme attaches some peptidoglycans to the surface of the outer membrane instead of incorporating them into the cell wall. The stray peptidoglycans on the cell's surface act as decoys, binding to vancomycin and keeping the drug from reaching its true target—the cell wall. The decoy strategy is similar to a mechanism used by Gram-positive bacteria—which lack a protective outer membrane—to resist vancomycin treatment, which also involves creating sites that bind the drug and keep it from its target. Vancomycin is not currently used clinically to treat E. coli or other Gram-negative infections because these bacteria are naturally quite resistant for other reasons. However, Grabowicz et al.'s findings do demonstrate how quickly bacteria can adapt and produce new defenses to antibiotics when old strategies fail. DOI:http://dx.doi.org/10.7554/eLife.05334.002
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Affiliation(s)
- Marcin Grabowicz
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Dorothee Andres
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Matthew D Lebar
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Goran Malojčić
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Daniel Kahne
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Princeton, United States
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35
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O'Brien JP, Needham BD, Brown DB, Trent MS, Brodbelt JS. Top-Down Strategies for the Structural Elucidation of Intact Gram-negative Bacterial Endotoxins. Chem Sci 2014; 5:4291-4301. [PMID: 25386333 PMCID: PMC4224326 DOI: 10.1039/c4sc01034e] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Re-modelling of lipopolysaccharides, which are the primary constituent of the outer cell membrane of Gram-negative bacteria, modulates pathogenesis and resistance to microbials. Reported herein is the characterization of intact Gram-negative bacterial lipooligosaccharides (LOS) via a new strategy utilizing online liquid chromatography (LC) coupled with ultraviolet photodissociation (UVPD) mass spectrometry. Compared to collision-based MS/MS methods, UVPD and UVPD/HCD promoted a greater array of cleavages within both the glycan and lipid moieties, including C-C, C-N, C-O cleavages in the acyl chains as well as glycosidic and cross-ring cleavages, thus providing the most far-reaching structural characterization of LOS. This LC-MS/MS strategy affords a robust analytical method to structurally characterize complex mixtures of bacterial endotoxins that maintains the integrity of the core oligosaccharide and lipid A domains of LOS, providing direct feedback about the cell envelope architectures and LOS modification strategies involved in resistance host innate immune defense.
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Affiliation(s)
- John P O'Brien
- Department of Chemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX, USA 78712
| | - Brittany D Needham
- The University of Texas at Austin, Department of Molecular Biosciences, 2506 Speedway A5000, Austin, TX, USA 78712
| | - Dusty B Brown
- The University of Texas at Austin, Department of Molecular Biosciences, 2506 Speedway A5000, Austin, TX, USA 78712
| | - M Stephen Trent
- The University of Texas at Austin, Department of Molecular Biosciences, 2506 Speedway A5000, Austin, TX, USA 78712
| | - Jennifer S Brodbelt
- Department of Chemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX, USA 78712
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36
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Abstract
Epsilon-poly-l-lysine (ε-PL) is a natural antimicrobial cationic peptide which is generally regarded as safe (GRAS) as a food preservative. Although its antimicrobial activity is well documented, its mechanism of action is only vaguely described. The aim of this study was to clarify ε-PL's mechanism of action using Escherichia coli and Listeria innocua as model organisms. We examined ε-PL's effect on cell morphology and membrane integrity and used an array of E. coli deletion mutants to study how specific outer membrane components affected the action of ε-PL. We furthermore studied its interaction with lipid bilayers using membrane models. In vitro cell studies indicated that divalent cations and the heptose I and II phosphate groups in the lipopolysaccharide layer of E. coli are critical for ε-PL's binding efficiency. ε-PL removed the lipopolysaccharide layer and affected cell morphology of E. coli, while L. innocua underwent minor morphological changes. Propidium iodide staining showed that ε-PL permeabilized the cytoplasmic membrane in both species, indicating the membrane as the site of attack. We compared the interaction with neutral or negatively charged membrane systems and showed that the interaction with ε-PL relied on negative charges on the membrane. Suspended membrane vesicles were disrupted by ε-PL, and a detergent-like disruption of E. coli membrane was confirmed by atomic force microscopy imaging of supported lipid bilayers. We hypothesize that ε-PL destabilizes membranes in a carpet-like mechanism by interacting with negatively charged phospholipid head groups, which displace divalent cations and enforce a negative curvature folding on membranes that leads to formation of vesicles/micelles.
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Kalynych S, Morona R, Cygler M. Progress in understanding the assembly process of bacterial O-antigen. FEMS Microbiol Rev 2014; 38:1048-65. [DOI: 10.1111/1574-6976.12070] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Revised: 01/28/2014] [Accepted: 02/24/2014] [Indexed: 12/20/2022] Open
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38
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Laverty G, Gorman SP, Gilmore BF. Biomolecular Mechanisms of Pseudomonas aeruginosa and Escherichia coli Biofilm Formation. Pathogens 2014; 3:596-632. [PMID: 25438014 PMCID: PMC4243431 DOI: 10.3390/pathogens3030596] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 07/10/2014] [Accepted: 07/14/2014] [Indexed: 12/13/2022] Open
Abstract
Pseudomonas aeruginosa and Escherichia coli are the most prevalent Gram-negative biofilm forming medical device associated pathogens, particularly with respect to catheter associated urinary tract infections. In a similar manner to Gram-positive bacteria, Gram-negative biofilm formation is fundamentally determined by a series of steps outlined more fully in this review, namely adhesion, cellular aggregation, and the production of an extracellular polymeric matrix. More specifically this review will explore the biosynthesis and role of pili and flagella in Gram-negative adhesion and accumulation on surfaces in Pseudomonas aeruginosa and Escherichia coli. The process of biofilm maturation is compared and contrasted in both species, namely the production of the exopolysaccharides via the polysaccharide synthesis locus (Psl), pellicle Formation (Pel) and alginic acid synthesis in Pseudomonas aeruginosa, and UDP-4-amino-4-deoxy-l-arabinose and colonic acid synthesis in Escherichia coli. An emphasis is placed on the importance of the LuxR homologue sdiA; the luxS/autoinducer-II; an autoinducer-III/epinephrine/norepinephrine and indole mediated Quorum sensing systems in enabling Gram-negative bacteria to adapt to their environments. The majority of Gram-negative biofilms consist of polysaccharides of a simple sugar structure (either homo- or heteropolysaccharides) that provide an optimum environment for the survival and maturation of bacteria, allowing them to display increased resistance to antibiotics and predation.
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Affiliation(s)
- Garry Laverty
- Biomaterials, Biofilm and Infection Control Research Group, School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK.
| | - Sean P Gorman
- Biomaterials, Biofilm and Infection Control Research Group, School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK.
| | - Brendan F Gilmore
- Biomaterials, Biofilm and Infection Control Research Group, School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK.
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Cress BF, Englaender JA, He W, Kasper D, Linhardt RJ, Koffas MAG. Masquerading microbial pathogens: capsular polysaccharides mimic host-tissue molecules. FEMS Microbiol Rev 2014; 38:660-97. [PMID: 24372337 PMCID: PMC4120193 DOI: 10.1111/1574-6976.12056] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 10/16/2013] [Accepted: 12/19/2013] [Indexed: 11/27/2022] Open
Abstract
The increasing prevalence of antibiotic-resistant bacteria portends an impending postantibiotic age, characterized by diminishing efficacy of common antibiotics and routine application of multifaceted, complementary therapeutic approaches to treat bacterial infections, particularly multidrug-resistant organisms. The first line of defense for most bacterial pathogens consists of a physical and immunologic barrier known as the capsule, commonly composed of a viscous layer of carbohydrates that are covalently bound to the cell wall in Gram-positive bacteria or often to lipids of the outer membrane in many Gram-negative bacteria. Bacterial capsular polysaccharides are a diverse class of high molecular weight polysaccharides contributing to virulence of many human pathogens in the gut, respiratory tree, urinary tract, and other host tissues, by hiding cell surface components that might otherwise elicit host immune response. This review highlights capsular polysaccharides that are structurally identical or similar to polysaccharides found in mammalian tissues, including polysialic acid and glycosaminoglycan capsules hyaluronan, heparosan, and chondroitin. Such nonimmunogenic coatings render pathogens insensitive to certain immune responses, effectively increasing residence time in host tissues and enabling pathologically relevant population densities to be reached. Biosynthetic pathways and capsular involvement in immune system evasion are described, providing a basis for potential therapies aimed at supplementing or replacing antibiotic treatment.
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Affiliation(s)
- Brady F Cress
- Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA
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40
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Kocharunchitt C, King T, Gobius K, Bowman JP, Ross T. Global genome response of Escherichia coli O157∶H7 Sakai during dynamic changes in growth kinetics induced by an abrupt downshift in water activity. PLoS One 2014; 9:e90422. [PMID: 24594867 PMCID: PMC3940904 DOI: 10.1371/journal.pone.0090422] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 01/30/2014] [Indexed: 01/10/2023] Open
Abstract
The present study was undertaken to investigate growth kinetics and time-dependent change in global expression of Escherichia coli O157∶H7 Sakai upon an abrupt downshift in water activity (aw). Based on viable count data, shifting E. coli from aw 0.993 to aw 0.985 or less caused an apparent loss, then recovery, of culturability. Exponential growth then resumed at a rate characteristic for the aw imposed. To understand the responses of this pathogen to abrupt osmotic stress, we employed an integrated genomic and proteomic approach to characterize its cellular response during exposure to a rapid downshift but still within the growth range from aw 0.993 to aw 0.967. Of particular interest, genes and proteins with cell envelope-related functions were induced during the initial loss and subsequent recovery of culturability. This implies that cells undergo remodeling of their envelope composition, enabling them to adapt to osmotic stress. Growth at low aw, however, involved up-regulating additional genes and proteins, which are involved in the biosynthesis of specific amino acids, and carbohydrate catabolism and energy generation. This suggests their important role in facilitating growth under such stress. Finally, we highlighted the ability of E. coli to activate multiple stress responses by transiently inducing the RpoE and RpoH regulons to control protein misfolding, while simultaneously activating the master stress regulator RpoS to mediate long-term adaptation to hyperosmolality. This investigation extends our understanding of the potential mechanisms used by pathogenic E. coli to adapt, survive and grow under osmotic stress, which could potentially be exploited to aid the selection and/or development of novel strategies to inactivate this pathogen.
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Affiliation(s)
- Chawalit Kocharunchitt
- Food Safety Centre, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tasmania, Australia
- * E-mail:
| | - Thea King
- Commonwealth Scientific and Industrial Research Organisation Animal, Food and Health Sciences, North Ryde, New South Wales, Australia
| | - Kari Gobius
- Commonwealth Scientific and Industrial Research Organisation Animal, Food and Health Sciences, Werribee, Victoria, Australia
| | - John P. Bowman
- Food Safety Centre, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tasmania, Australia
| | - Tom Ross
- Food Safety Centre, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tasmania, Australia
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41
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On the essentiality of lipopolysaccharide to Gram-negative bacteria. Curr Opin Microbiol 2013; 16:779-85. [PMID: 24148302 DOI: 10.1016/j.mib.2013.09.007] [Citation(s) in RCA: 210] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 09/23/2013] [Indexed: 01/26/2023]
Abstract
Lipopolysaccharide is a highly acylated saccharolipid located on the outer leaflet of the outer membrane of Gram-negative bacteria. Lipopolysaccharide is critical to maintaining the barrier function preventing the passive diffusion of hydrophobic solutes such as antibiotics and detergents into the cell. Lipopolysaccharide has been considered an essential component for outer membrane biogenesis and cell viability based on pioneering studies in the model Gram-negative organisms Escherichia coli and Salmonella. With the isolation of lipopolysaccharide-null mutants in Neisseria meningitidis, Moraxella catarrhalis, and most recently in Acinetobacter baumannii, it has become increasingly apparent that lipopolysaccharide is not an essential outer membrane building block in all organisms. We suggest the accumulation of toxic intermediates, misassembly of essential outer membrane porins, and outer membrane stress response pathways that are activated by mislocalized lipopolysaccharide may collectively contribute to the observed strain-dependent essentiality of lipopolysaccharide.
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42
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Chaput C, Spindler E, Gill RT, Zychlinsky A. O-antigen protects gram-negative bacteria from histone killing. PLoS One 2013; 8:e71097. [PMID: 23951089 PMCID: PMC3738592 DOI: 10.1371/journal.pone.0071097] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 06/24/2013] [Indexed: 12/15/2022] Open
Abstract
Beyond their traditional role of wrapping DNA, histones display antibacterial activity to Gram-negative and -positive bacteria. To identify bacterial components that allow survival to a histone challenge, we selected resistant bacteria from homologous Escherichia coli libraries that harbor plasmids carrying pieces of the chromosome in different sizes. We identified genes required for exopolysaccharide production and for the synthesis of the polysaccharide domain of the lipopolysaccharide, called O-antigen. Indeed, O-antigen and exopolysaccharide conferred further resistance to histones. Notably, O-antigen also conferred resistance to histones in the pathogens Shigella flexneri and Klebsiella pneumoniae.
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Affiliation(s)
- Catherine Chaput
- Department of Cellular Microbiology, Max-Planck Institute for Infection Biology, Berlin, Germany
- * E-mail: (CC); (AZ)
| | - Eileen Spindler
- Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado, United States of America
| | - Ryan T. Gill
- Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado, United States of America
| | - Arturo Zychlinsky
- Department of Cellular Microbiology, Max-Planck Institute for Infection Biology, Berlin, Germany
- * E-mail: (CC); (AZ)
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43
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A colanic acid operon deletion mutation enhances induction of early antibody responses by live attenuated Salmonella vaccine strains. Infect Immun 2013; 81:3148-62. [PMID: 23774599 DOI: 10.1128/iai.00097-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Colanic acid (CA) is a common exopolysaccharide produced by many genera in the Enterobacteriaceae. It is critical for biofilm formation on HEp-2 cells and on chicken intestinal tissue by Salmonella. In this study, we generated different CA synthesis gene mutants and evaluated the immune responses induced by these mutants. One of these mutations, Δ(wza-wcaM)8, which deleted the whole operon for CA synthesis, was introduced into two Salmonella vaccine strains attenuated by auxotrophic traits or by the regulated delayed attenuation strategy (RDAS). The mice immunized with the auxotrophic Salmonella vaccine strain with the deletion mutation Δ(wza-wcaM)8 developed higher vaginal IgA titers against the heterologous protective antigen and higher levels of antigen-specific IgA secretion cells in lungs. In Salmonella vaccine strains with RDAS, the strain with the Δ(wza-wcaM)8 mutation resulted in higher levels of protective antigen production during in vitro growth. Mice immunized with this strain developed higher serum IgG and mucosal IgA antibody responses at 2 weeks. This strain also resulted in better gamma interferon (IFN-γ) responses than the strain without this deletion at doses of 10(8) and 10(9) CFU. Thus, the mutation Δ(wza-wcaM)8 will be included in various recombinant attenuated Salmonella vaccine (RASV) strains with RDAS derived from Salmonella enterica serovar Paratyphi A and Salmonella enterica serovar Typhi to induce protective immunity against bacterial pathogens.
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Needham BD, Trent MS. Fortifying the barrier: the impact of lipid A remodelling on bacterial pathogenesis. Nat Rev Microbiol 2013; 11:467-81. [PMID: 23748343 PMCID: PMC6913092 DOI: 10.1038/nrmicro3047] [Citation(s) in RCA: 392] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Gram-negative bacteria decorate their outermost surface structure, lipopolysaccharide, with elaborate chemical moieties, which effectively disguises them from immune surveillance and protects them from the onslaught of host defences. Many of these changes occur on the lipid A moiety of lipopolysaccharide, a component that is crucial for host recognition of Gram-negative infection. In this Review, we describe the regulatory mechanisms controlling lipid A modification and discuss the impact of modifications on pathogenesis, bacterial physiology and bacterial interactions with the host immune system.
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Affiliation(s)
- Brittany D Needham
- The Institute of Cellular and Molecular Biology, The University of Texas at Austin, 78712, USA
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45
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Abstract
WaaL is a membrane enzyme that catalyzes the glycosidic bonding of a sugar at the proximal end of the undecaprenyl-diphosphate (Und-PP)-O-antigen with a terminal sugar of the lipid A-core oligosaccharide (OS). This is a critical step in lipopolysaccharide synthesis. We describe here an assay to perform the ligation reaction in vitro utilizing native substrates.
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46
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Mally M, Fontana C, Leibundgut-Landmann S, Laacisse L, Fan YY, Widmalm G, Aebi M. Glycoengineering of host mimicking type-2 LacNAc polymers and Lewis X antigens on bacterial cell surfaces. Mol Microbiol 2012; 87:112-31. [PMID: 23163552 DOI: 10.1111/mmi.12086] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2012] [Indexed: 01/27/2023]
Abstract
Bacterial carbohydrate structures play a central role in mediating a variety of host-pathogen interactions. Glycans can either elicit protective immune response or lead to escape of immune surveillance by mimicking host structures. Lipopolysaccharide (LPS), a major component on the surface of Gram-negative bacteria, is composed of a lipid A-core and the O-antigen polysaccharide. Pathogens like Neisseria meningitidis expose a lipooligosaccharide (LOS), which outermost glycans mimick mammalian epitopes to avoid immune recognition. Lewis X (Galβ1-4(Fucα1-3)GlcNAc) antigens of Helicobacter pylori or of the helminth Schistosoma mansoni modulate the immune response by interacting with receptors on human dendritic cells. In a glycoengineering approach we generate human carbohydrate structures on the surface of recombinant Gram-negative bacteria, such as Escherichia coli and Salmonella enterica sv. Typhimurium that lack O-antigen. A ubiquitous building block in mammalian N-linked protein glycans is Galβ1-4GlcNAc, referred to as a type-2 N-acetyllactosamine, LacNAc, sequence. Strains displaying polymeric LacNAc were generated by introducing a combination of glycosyltransferases that act on modified lipid A-cores, resulting in efficient expression of the carbohydrate epitope on bacterial cell surfaces. The poly-LacNAc scaffold was used as an acceptor for fucosylation leading to polymers of Lewis X antigens. We analysed the distribution of the carbohydrate epitopes by FACS, microscopy and ELISA and confirmed engineered LOS containing LacNAc and Lewis X repeats by MALDI-TOF and NMR analysis. Glycoengineered LOS induced pro-inflammatory response in murine dendritic cells. These bacterial strains can thus serve as tools to analyse the role of defined carbohydrate structures in different biological processes.
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Affiliation(s)
- Manuela Mally
- ETH Zurich, Institute of Microbiology, Wolfgang-Pauli-Str. 10, HCI F 406, CH- 8093 Zurich, Switzerland.
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47
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Platelet factor 4 binding to lipid A of Gram-negative bacteria exposes PF4/heparin-like epitopes. Blood 2012; 120:3345-52. [DOI: 10.1182/blood-2012-06-434985] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
AbstractThe positively charged chemokine platelet factor 4 (PF4) forms immunogenic complexes with heparin and other polyanions. Resulting antibodies can induce the adverse drug effect heparin-induced thrombocytopenia. PF4 also binds to bacteria, thereby exposing the same neoantigen(s) as with heparin. In this study, we identified the negatively charged lipopolysaccharide (LPS) as the PF4 binding structure on Gram-negative bacteria. We demonstrate by flow cytometry that mutant bacteria with progressively truncated LPS structures show increasingly enhanced PF4 binding activity. PF4 bound strongest to mutants lacking the O-antigen and core structure of LPS, but still exposing lipid A on their surfaces. Strikingly, PF4 bound more efficiently to bisphosphorylated lipid A than to monophosphorylated lipid A, suggesting that phosphate residues of lipid A mediate PF4 binding. Interactions of PF4 with Gram-negative bacteria, where only the lipid A part of LPS is exposed, induce epitopes on PF4 resembling those on PF4/heparin complexes as shown by binding of human anti-PF4/heparin antibodies. As both the lipid A on the surface of Gram-negative bacteria and the amino acids of PF4 contributing to polyanion binding are highly conserved, our results further support the hypothesis that neoepitope formation on PF4 after binding to bacteria is an ancient host defense mechanism.
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48
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Roles of the structural symbiosis polysaccharide (syp) genes in host colonization, biofilm formation, and polysaccharide biosynthesis in Vibrio fischeri. J Bacteriol 2012; 194:6736-47. [PMID: 23042998 DOI: 10.1128/jb.00707-12] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The symbiosis polysaccharide locus, syp, is required for Vibrio fischeri to form a symbiotic association with the squid Euprymna scolopes. It is also required for biofilm formation induced by the unlinked regulator RscS. The syp locus includes 18 genes that can be classified into four groups based on putative function: 4 genes encode putative regulators, 6 encode glycosyltransferases, 2 encode export proteins, and the remaining 6 encode proteins with other functions, including polysaccharide modification. To understand the roles of each of the 14 structural syp genes in colonization and biofilm formation, we generated nonpolar in-frame deletions of each gene. All of the deletion mutants exhibited defects in their ability to colonize juvenile squid, although the impact of the loss of SypB or SypI was modest. Consistent with their requirement for colonization, most of the structural genes were also required for RscS-induced biofilm formation. In particular, the production of wrinkled colonies, pellicles, and the matrix on the colony surface was eliminated or severely decreased in all mutants except for the sypB and sypI mutants; in contrast, only a subset of genes appeared to play a role in attachment to glass. Finally, immunoblotting data suggested that the structural Syp proteins are involved in polysaccharide production and/or export. These results provide important insights into the requirements for the syp genes under different environmental conditions and thus lay the groundwork for a more complete understanding of the matrix produced by V. fischeri to enhance cell-cell interactions and promote symbiotic colonization.
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49
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Yeom J, Lee Y, Park W. Effects of non-ionic solute stresses on biofilm formation and lipopolysaccharide production in Escherichia coli O157:H7. Res Microbiol 2012; 163:258-67. [DOI: 10.1016/j.resmic.2012.01.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 01/30/2012] [Indexed: 10/14/2022]
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50
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Functional characterization of UDP-glucose:undecaprenyl-phosphate glucose-1-phosphate transferases of Escherichia coli and Caulobacter crescentus. J Bacteriol 2012; 194:2646-57. [PMID: 22408159 DOI: 10.1128/jb.06052-11] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Escherichia coli K-12 WcaJ and the Caulobacter crescentus HfsE, PssY, and PssZ enzymes are predicted to initiate the synthesis of colanic acid (CA) capsule and holdfast polysaccharide, respectively. These proteins belong to a prokaryotic family of membrane enzymes that catalyze the formation of a phosphoanhydride bond joining a hexose-1-phosphate with undecaprenyl phosphate (Und-P). In this study, in vivo complementation assays of an E. coli K-12 wcaJ mutant demonstrated that WcaJ and PssY can complement CA synthesis. Furthermore, WcaJ can restore holdfast production in C. crescentus. In vitro transferase assays demonstrated that both WcaJ and PssY utilize UDP-glucose but not UDP-galactose. However, in a strain of Salmonella enterica serovar Typhimurium deficient in the WbaP O antigen initiating galactosyltransferase, complementation with WcaJ or PssY resulted in O-antigen production. Gas chromatography-mass spectrometry (GC-MS) analysis of the lipopolysaccharide (LPS) revealed the attachment of both CA and O-antigen molecules to lipid A-core oligosaccharide (OS). Therefore, while UDP-glucose is the preferred substrate of WcaJ and PssY, these enzymes can also utilize UDP-galactose. This unexpected feature of WcaJ and PssY may help to map specific residues responsible for the nucleotide diphosphate specificity of these or similar enzymes. Also, the reconstitution of O-antigen synthesis in Salmonella, CA capsule synthesis in E. coli, and holdfast synthesis provide biological assays of high sensitivity to examine the sugar-1-phosphate transferase specificity of heterologous proteins.
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