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Wang HJ, Hernández-Rocamora VM, Kuo CI, Hsieh KY, Lee SH, Ho MR, Tu Z, Vollmer W, Chang CI. Structural basis for the hydrolytic activity of the transpeptidase-like protein DpaA to detach Braun's lipoprotein from peptidoglycan. mBio 2023; 14:e0137923. [PMID: 37830798 PMCID: PMC10653827 DOI: 10.1128/mbio.01379-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 08/21/2023] [Indexed: 10/14/2023] Open
Abstract
IMPORTANCE Cross-linking reaction of Braun's lipoprotein (Lpp) to peptidoglycan (PG) is catalyzed by some members of the YkuD family of transpeptidases. However, the exact opposite reaction of cleaving the Lpp-PG cross-link is performed by DpaA, which is also a YkuD-like protein. In this work, we determined the crystal structure of DpaA to provide the molecular rationale for the ability of the transpeptidase-like protein to cleave, rather than form, the Lpp-PG linkage. Our findings also revealed the structural features that distinguish the different functional types of the YkuD family enzymes from one another.
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Affiliation(s)
- Hsiu-Jung Wang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Víctor M. Hernández-Rocamora
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Chiao-I Kuo
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Kan-Yen Hsieh
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Szu-Hui Lee
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Meng-Ru Ho
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Zhijay Tu
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Chung-I Chang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
- College of Life Science, Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
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2
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Alberge F, Lakey BD, Schaub RE, Dohnalkova AC, Lemmer KC, Dillard JP, Noguera DR, Donohue TJ. A previously uncharacterized divisome-associated lipoprotein, DalA, is needed for normal cell division in Rhodobacterales. mBio 2023; 14:e0120323. [PMID: 37389444 PMCID: PMC10470522 DOI: 10.1128/mbio.01203-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 05/23/2023] [Indexed: 07/01/2023] Open
Abstract
The bacterial cell envelope is a key subcellular compartment with important roles in antibiotic resistance, nutrient acquisition, and cell morphology. We seek to gain a better understanding of proteins that contribute to the function of the cell envelope in Alphaproteobacteria. Using Rhodobacter sphaeroides, we show that a previously uncharacterized protein, RSP_1200, is an outer membrane (OM) lipoprotein that non-covalently binds peptidoglycan (PG). Using a fluorescently tagged version of this protein, we find that RSP_1200 undergoes a dynamic repositioning during the cell cycle and is enriched at the septum during cell division. We show that the position of RSP_1200 mirrors the location of FtsZ rings, leading us to propose that RSP_1200 is a newly identified component of the R. sphaeroides' divisome. Additional support for this hypothesis includes the co-precipitation of RSP_1200 with FtsZ, the Pal protein, and several predicted PG L,D-transpeptidases. We also find that a ∆RSP_1200 mutation leads to defects in cell division, sensitivity to PG-active antibiotics, and results in the formation of OM protrusions at the septum during cell division. Based on these results, we propose to name RSP_1200 DalA (for division-associated lipoprotein A) and postulate that DalA serves as a scaffold to position or modulate the activity of PG transpeptidases that are needed to form envelope invaginations during cell division. We find that DalA homologs are present in members of the Rhodobacterales order within Alphaproteobacteria. Therefore, we propose that further analysis of this and related proteins will increase our understanding of the macromolecular machinery and proteins that participate in cell division in Gram-negative bacteria. IMPORTANCE Multi-protein complexes of the bacterial cell envelope orchestrate key processes like growth, division, biofilm formation, antimicrobial resistance, and production of valuable compounds. The subunits of these protein complexes are well studied in some bacteria, and differences in their composition and function are linked to variations in cell envelope composition, shape, and proliferation. However, some envelope protein complex subunits have no known homologs across the bacterial phylogeny. We find that Rhodobacter sphaeroides RSP_1200 is a newly identified lipoprotein (DalA) and that loss of this protein causes defects in cell division and changes the sensitivity to compounds, affecting cell envelope synthesis and function. We find that DalA forms a complex with proteins needed for cell division, binds the cell envelope polymer peptidoglycan, and colocalizes with enzymes involved in the assembly of this macromolecule. The analysis of DalA provides new information on the cell division machinery in this and possibly other Alphaproteobacteria.
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Affiliation(s)
- François Alberge
- />Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Bryan D. Lakey
- />Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Ryan E. Schaub
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Alice C. Dohnalkova
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA
| | | | - Joseph P. Dillard
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Daniel R. Noguera
- />Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Timothy J. Donohue
- />Wisconsin Energy Institute, Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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3
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Peptidoglycan Remodeling by an L,D-Transpeptidase, LdtD during Cold Shock in Escherichia coli. J Bacteriol 2023; 205:e0038222. [PMID: 36507682 PMCID: PMC9879098 DOI: 10.1128/jb.00382-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Peptidoglycan (PG) is a unique and essential component of the bacterial cell envelope. It is made up of several linear glycan polymers cross-linked through covalently attached stem peptides making it a fortified mesh-like sacculus around the bacterial cytosolic membrane. In most bacteria, including Escherichia coli, the stem peptide is made up of l-alanine (l-Ala1), d-glutamate (d-Glu2), meso-diaminopimelic acid (mDAP3), d-alanine (d-Ala4), and d-Ala5 with cross-links occurring either between d-ala4 and mDAP3 or between two mDAP3 residues. Of these, the cross-links of the 4-3 (d-Ala4-mDAP3) type are the most predominant and are formed by penicillin-binding D,D-transpeptidases, whereas the formation of less frequent 3-3 linkages (mDAP3-mDAP3) is catalyzed by L,D-transpeptidases. In this study, we found that the frequency of the 3-3 cross-linkages increased upon cold shock in exponentially growing E. coli and that the increase was mediated by an L,D-transpeptidase, LdtD. We found that a cold-inducible RNA helicase DeaD enhanced the cellular LdtD level by facilitating its translation resulting in an increased abundance of 3-3 cross-linkages during cold shock. However, DeaD was also required for optimal expression of LdtD during growth at ambient temperature. Overall, our study finds that E. coli undergoes PG remodeling during cold shock by altering the frequency of 3-3 cross-linkages, implying a role for these modifications in conferring fitness and survival advantage to bacteria growing in diverse environmental conditions. IMPORTANCE Most bacteria are surrounded by a protective exoskeleton called peptidoglycan (PG), an extensively cross-linked mesh-like macromolecule. In bacteria, such as Escherichia coli, the cross-links in the PG are of two types: a major fraction is of 4-3 type whereas a minor fraction is of 3-3 type. Here, we showed that E. coli exposed to cold shock had elevated levels of 3-3 cross-links due to the upregulation of an enzyme, LdtD, that catalyzed their formation. We showed that a cold-inducible RNA helicase DeaD enhanced the cellular LdtD level by facilitating its translation, resulting in increased 3-3 cross-links during cold shock. Our results suggest that PG remodeling contributes to the survival and fitness of bacteria growing in conditions of cold stress.
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PBP1A Directly Interacts with the Divisome Complex to Promote Septal Peptidoglycan Synthesis in Acinetobacter baumannii. J Bacteriol 2022; 204:e0023922. [PMID: 36317921 PMCID: PMC9765026 DOI: 10.1128/jb.00239-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The class A penicillin-binding proteins (aPBPs), PBP1A and PBP1B, are major peptidoglycan synthases that synthesize more than half of the peptidoglycan per generation in Escherichia coli. Whereas aPBPs have distinct roles in peptidoglycan biosynthesis during growth (i.e., elongation and division), they are semiredundant; disruption of either is rescued by the other to maintain envelope homeostasis and promote proper growth. Acinetobacter baumannii is a nosocomial pathogen that has a high propensity to overcome antimicrobial treatment. A. baumannii contains both PBP1A and PBP1B (encoded by mrcA and mrcB, respectively), but only mrcA deletion decreased fitness and contributed to colistin resistance through inactivation of lipooligosaccharide biosynthesis, indicating that PBP1B was not functionally redundant with the PBP1A activity. While previous studies suggested a distinct role for PBP1A in division, it was unknown whether its role in septal peptidoglycan biosynthesis was direct. Here, we show that A. baumannii PBP1A has a direct role in division through interactions with divisome components. PBP1A localizes to septal sites during growth, where it interacts with the transpeptidase PBP3, an essential division component that regulates daughter cell formation. PBP3 overexpression was sufficient to rescue the division defect in ΔmrcA A. baumannii; however, PBP1A overexpression was not sufficient to rescue the septal defect when PBP3 was inhibited, suggesting that their activity is not redundant. Overexpression of a major dd-carboxypeptidase, PBP5, also restored the canonical A. baumannii coccobacilli morphology in ΔmrcA cells. Together, these data support a direct role for PBP1A in A. baumannii division and highlights its role as a septal peptidoglycan synthase. IMPORTANCE Peptidoglycan biosynthesis is a validated target of β-lactam antibiotics, and it is critical that we understand essential processes in multidrug-resistant pathogens such as Acinetobacter baumannii. While model systems such as Escherichia coli have shown that PBP1A is associated with side wall peptidoglycan synthesis, we show herein that A. baumannii PBP1A directly interacts with the divisome component PBP3 to promote division, suggesting a unique role for the enzyme in this highly drug-resistant nosocomial pathogen. A. baumannii demonstrated unanticipated resistance and tolerance to envelope-targeting antibiotics, which may be driven by rewired peptidoglycan machinery and may underlie therapeutic failure during antibiotic treatment.
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5
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Xu Y, Hernández-Rocamora VM, Lorent JH, Cox R, Wang X, Bao X, Stel M, Vos G, van den Bos RM, Pieters RJ, Gray J, Vollmer W, Breukink E. Metabolic labeling of the bacterial peptidoglycan by functionalized glucosamine. iScience 2022; 25:104753. [PMID: 35942089 PMCID: PMC9356107 DOI: 10.1016/j.isci.2022.104753] [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: 03/10/2022] [Revised: 05/09/2022] [Accepted: 07/08/2022] [Indexed: 11/28/2022] Open
Abstract
N-Acetylglucosamine (GlcNAc) is an essential monosaccharide required in almost all organisms. Fluorescent labeling of the peptidoglycan (PG) on N-acetylglucosamine has been poorly explored. Here, we report on the labeling of the PG with a bioorthogonal handle on the GlcNAc. We developed a facile one-step synthesis of uridine diphosphate N-azidoacetylglucosamine (UDP-GlcNAz) using the glycosyltransferase OleD, followed by in vitro incorporation of GlcNAz into the peptidoglycan precursor Lipid II and fluorescent labeling of the azido group via click chemistry. In a PG synthesis assay, fluorescent GlcNAz-labeled Lipid II was incorporated into peptidoglycan by the DD-transpeptidase activity of bifunctional class A penicillin-binding proteins. We further demonstrate the incorporation of GlcNAz into the PG layer of OleD-expressed bacteria by feeding with 2-chloro-4-nitrophenyl GlcNAz (GlcNAz-CNP). Hence, our labeling method using the heterologous expression of OleD is useful to study PG synthesis and possibly other biological processes involving GlcNAc metabolism in vivo. Peptidoglycan consists of N-acetylglucosamine, N-acetylmuramic acid, and amino acids We developed a one-step synthesis of azide-labeled UDP-N-acetylglucosamine In vivo generated azide-labeled UDP-N-acetylglucosamine gets incorporated into peptidoglycan Bacteria were fluorescently labeled on N-acetylglucosamine of peptidoglycan
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Affiliation(s)
- Yang Xu
- Membrane Biochemistry and Biophysics, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | | | - Joseph H. Lorent
- Membrane Biochemistry and Biophysics, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Ruud Cox
- Membrane Biochemistry and Biophysics, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Xiaoqi Wang
- Membrane Biochemistry and Biophysics, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Xue Bao
- Membrane Biochemistry and Biophysics, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Marjon Stel
- Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 Utrecht, the Netherlands
| | - Gaël Vos
- Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 Utrecht, the Netherlands
| | - Ramon M. van den Bos
- Membrane Biochemistry and Biophysics, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Roland J. Pieters
- Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 Utrecht, the Netherlands
| | - Joe Gray
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, UK
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, UK
| | - Eefjan Breukink
- Membrane Biochemistry and Biophysics, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
- Corresponding author
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6
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Atze H, Liang Y, Hugonnet JE, Gutierrez A, Rusconi F, Arthur M. Heavy isotope labeling and mass spectrometry reveal unexpected remodeling of bacterial cell wall expansion in response to drugs. eLife 2022; 11:72863. [PMID: 35678393 PMCID: PMC9249393 DOI: 10.7554/elife.72863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 06/09/2022] [Indexed: 11/13/2022] Open
Abstract
Antibiotics of the β-lactam (penicillin) family inactivate target enzymes called D,D-transpeptidases or penicillin-binding proteins (PBPs) that catalyze the last cross-linking step of peptidoglycan synthesis. The resulting net-like macromolecule is the essential component of bacterial cell walls that sustains the osmotic pressure of the cytoplasm. In Escherichia coli, bypass of PBPs by the YcbB L,D-transpeptidase leads to resistance to these drugs. We developed a new method based on heavy isotope labeling and mass spectrometry to elucidate PBP- and YcbB-mediated peptidoglycan polymerization. PBPs and YcbB similarly participated in single-strand insertion of glycan chains into the expanding bacterial side wall. This absence of any transpeptidase-specific signature suggests that the peptidoglycan expansion mode is determined by other components of polymerization complexes. YcbB did mediate β-lactam resistance by insertion of multiple strands that were exclusively cross-linked to existing tripeptide-containing acceptors. We propose that this undocumented mode of polymerization depends upon accumulation of linear glycan chains due to PBP inactivation, formation of tripeptides due to cleavage of existing cross-links by a β-lactam-insensitive endopeptidase, and concerted cross-linking by YcbB.
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Affiliation(s)
- Heiner Atze
- INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France
| | | | | | - Arnaud Gutierrez
- INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France
| | | | - Michel Arthur
- INSERM, UMR-S 1138, Centre de Recherche des Cordeliers, Paris, France
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7
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Graham CLB, Newman H, Gillett FN, Smart K, Briggs N, Banzhaf M, Roper DI. A Dynamic Network of Proteins Facilitate Cell Envelope Biogenesis in Gram-Negative Bacteria. Int J Mol Sci 2021; 22:12831. [PMID: 34884635 PMCID: PMC8657477 DOI: 10.3390/ijms222312831] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/02/2021] [Accepted: 11/03/2021] [Indexed: 01/01/2023] Open
Abstract
Bacteria must maintain the ability to modify and repair the peptidoglycan layer without jeopardising its essential functions in cell shape, cellular integrity and intermolecular interactions. A range of new experimental techniques is bringing an advanced understanding of how bacteria regulate and achieve peptidoglycan synthesis, particularly in respect of the central role played by complexes of Sporulation, Elongation or Division (SEDs) and class B penicillin-binding proteins required for cell division, growth and shape. In this review we highlight relationships implicated by a bioinformatic approach between the outer membrane, cytoskeletal components, periplasmic control proteins, and cell elongation/division proteins to provide further perspective on the interactions of these cell division, growth and shape complexes. We detail the network of protein interactions that assist in the formation of peptidoglycan and highlight the increasingly dynamic and connected set of protein machinery and macrostructures that assist in creating the cell envelope layers in Gram-negative bacteria.
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Affiliation(s)
- Chris L. B. Graham
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK; (C.L.B.G.); (H.N.); (F.N.G.); (K.S.); (N.B.)
| | - Hector Newman
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK; (C.L.B.G.); (H.N.); (F.N.G.); (K.S.); (N.B.)
| | - Francesca N. Gillett
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK; (C.L.B.G.); (H.N.); (F.N.G.); (K.S.); (N.B.)
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK;
| | - Katie Smart
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK; (C.L.B.G.); (H.N.); (F.N.G.); (K.S.); (N.B.)
| | - Nicholas Briggs
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK; (C.L.B.G.); (H.N.); (F.N.G.); (K.S.); (N.B.)
| | - Manuel Banzhaf
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK;
| | - David I. Roper
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK; (C.L.B.G.); (H.N.); (F.N.G.); (K.S.); (N.B.)
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8
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Unipolar Peptidoglycan Synthesis in the Rhizobiales Requires an Essential Class A Penicillin-Binding Protein. mBio 2021; 12:e0234621. [PMID: 34544272 PMCID: PMC8546619 DOI: 10.1128/mbio.02346-21] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Members of the Rhizobiales are polarly growing bacteria that lack homologs of the canonical Rod complex. To investigate the mechanisms underlying polar cell wall synthesis, we systematically probed the function of cell wall synthesis enzymes in the plant pathogen Agrobacterium tumefaciens. The development of fluorescent d-amino acid dipeptide (FDAAD) probes, which are incorporated into peptidoglycan by penicillin-binding proteins in A. tumefaciens, enabled us to monitor changes in growth patterns in the mutants. Use of these fluorescent cell wall probes and peptidoglycan compositional analysis demonstrate that a single class A penicillin-binding protein is essential for polar peptidoglycan synthesis. Furthermore, we find evidence of an additional mode of cell wall synthesis that requires ld-transpeptidase activity. Genetic analysis and cell wall targeting antibiotics reveal that the mechanism of unipolar growth is conserved in Sinorhizobium and Brucella. This work provides insights into unipolar peptidoglycan biosynthesis employed by the Rhizobiales during cell elongation.
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9
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Luong P, Dube DH. Dismantling the bacterial glycocalyx: Chemical tools to probe, perturb, and image bacterial glycans. Bioorg Med Chem 2021; 42:116268. [PMID: 34130219 DOI: 10.1016/j.bmc.2021.116268] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 05/27/2021] [Accepted: 06/01/2021] [Indexed: 12/20/2022]
Abstract
The bacterial glycocalyx is a quintessential drug target comprised of structurally distinct glycans. Bacterial glycans bear unusual monosaccharide building blocks whose proper construction is critical for bacterial fitness, survival, and colonization in the human host. Despite their appeal as therapeutic targets, bacterial glycans are difficult to study due to the presence of rare bacterial monosaccharides that are linked and modified in atypical manners. Their structural complexity ultimately hampers their analytical characterization. This review highlights recent advances in bacterial chemical glycobiology and focuses on the development of chemical tools to probe, perturb, and image bacterial glycans and their biosynthesis. Current technologies have enabled the study of bacterial glycosylation machinery even in the absence of detailed structural information.
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Affiliation(s)
- Phuong Luong
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Danielle H Dube
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA.
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10
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Gurnani Serrano CK, Winkle M, Martorana AM, Biboy J, Morè N, Moynihan P, Banzhaf M, Vollmer W, Polissi A. ActS activates peptidoglycan amidases during outer membrane stress in Escherichia coli. Mol Microbiol 2021; 116:329-342. [PMID: 33660879 PMCID: PMC8360153 DOI: 10.1111/mmi.14712] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/26/2021] [Accepted: 03/02/2021] [Indexed: 12/22/2022]
Abstract
The integrity of the cell envelope of E. coli relies on the concerted activity of multi-protein machineries that synthesize the peptidoglycan (PG) and the outer membrane (OM). Our previous work found that the depletion of lipopolysaccharide (LPS) export to the OM induces an essential PG remodeling process involving LD-transpeptidases (LDTs), the glycosyltransferase function of PBP1B and the carboxypeptidase PBP6a. Consequently, cells with defective OM biogenesis lyse if they lack any of these PG enzymes. Here we report that the morphological defects, and lysis associated with a ldtF mutant with impaired LPS transport, are alleviated by the loss of the predicted OM-anchored lipoprotein ActS (formerly YgeR). We show that ActS is an inactive member of LytM-type peptidoglycan endopeptidases due to a degenerated catalytic domain. ActS is capable of activating all three main periplasmic peptidoglycan amidases, AmiA, AmiB, and AmiC, which were previously reported to be activated only by EnvC and/or NlpD. Our data also suggest that in vivo ActS preferentially activates AmiC and that its function is linked to cell envelope stress.
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Affiliation(s)
| | - Matthias Winkle
- The Centre for Bacterial Cell BiologyBiosciences InstituteNewcastle UniversityNewcastle upon TyneUK
| | - Alessandra M. Martorana
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoMilanItaly
| | - Jacob Biboy
- The Centre for Bacterial Cell BiologyBiosciences InstituteNewcastle UniversityNewcastle upon TyneUK
| | - Niccolo Morè
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoMilanItaly
- Present address:
Nikon Instruments Europe B.VAmsterdamNorth HollandNetherlands
| | - Patrick Moynihan
- Institute of Microbiology and InfectionSchool of Biological SciencesUniversity of BirminghamBirminghamUK
| | - Manuel Banzhaf
- Institute of Microbiology and InfectionSchool of Biological SciencesUniversity of BirminghamBirminghamUK
| | - Waldemar Vollmer
- The Centre for Bacterial Cell BiologyBiosciences InstituteNewcastle UniversityNewcastle upon TyneUK
| | - Alessandra Polissi
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoMilanItaly
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11
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Abstract
Gram-negative bacteria have a unique cell envelope with a lipopolysaccharide-containing outer membrane that is tightly connected to a thin layer of peptidoglycan. The tight connection between the outer membrane and peptidoglycan is needed to maintain the outer membrane as an impermeable barrier for many toxic molecules and antibiotics. Enterobacteriaceae such as Escherichia coli covalently attach the abundant outer membrane-anchored lipoprotein Lpp (Braun’s lipoprotein) to tripeptides in peptidoglycan, mediated by the transpeptidases LdtA, LdtB, and LdtC. LdtD and LdtE are members of the same family of ld-transpeptidases but they catalyze a different reaction, the formation of 3-3 cross-links in the peptidoglycan. The function of the sixth homologue in E. coli, LdtF, remains unclear, although it has been shown to become essential in cells with inhibited lipopolysaccharide export to the outer membrane. We now show that LdtF hydrolyzes the Lpp-peptidoglycan linkage, detaching Lpp from peptidoglycan, and have renamed LdtF to peptidoglycan meso-diaminopimelic acid protein amidase A (DpaA). We show that the detachment of Lpp from peptidoglycan is beneficial for the cell under certain stress conditions and that the deletion of dpaA allows frequent transposon inactivation in the lapB (yciM) gene, whose product downregulates lipopolysaccharide biosynthesis. DpaA-like proteins have characteristic sequence motifs and are present in many Gram-negative bacteria, of which some have no Lpp, raising the possibility that DpaA has other substrates in these species. Overall, our data show that the Lpp-peptidoglycan linkage in E. coli is more dynamic than previously appreciated.
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12
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Cleavage of Braun's lipoprotein Lpp from the bacterial peptidoglycan by a paralog of l,d-transpeptidases, LdtF. Proc Natl Acad Sci U S A 2021; 118:2101989118. [PMID: 33941679 DOI: 10.1073/pnas.2101989118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The gram-negative bacterial cell envelope is made up of an outer membrane (OM), an inner membrane (IM) that surrounds the cytoplasm, and a periplasmic space between the two membranes containing peptidoglycan (PG or murein). PG is an elastic polymer that forms a mesh-like sacculus around the IM, protecting cells from turgor and environmental stress conditions. In several bacteria, including Escherichia coli, the OM is tethered to PG by an abundant OM lipoprotein, Lpp (or Braun's lipoprotein), that functions to maintain the structural and functional integrity of the cell envelope. Since its discovery, Lpp has been studied extensively, and although l,d-transpeptidases, the enzymes that catalyze the formation of PG-Lpp linkages, have been earlier identified, it is not known how these linkages are modulated. Here, using genetic and biochemical approaches, we show that LdtF (formerly yafK), a newly identified paralog of l,d-transpeptidases in E. coli, is a murein hydrolytic enzyme that catalyzes cleavage of Lpp from the PG sacculus. LdtF also exhibits glycine-specific carboxypeptidase activity on muropeptides containing a terminal glycine residue. LdtF was earlier presumed to be an l,d-transpeptidase; however, our results show that it is indeed an l,d-endopeptidase that hydrolyzes the products generated by the l,d-transpeptidases. To summarize, this study describes the discovery of a murein endopeptidase with a hitherto unknown catalytic specificity that removes the PG-Lpp cross-links, suggesting a role for LdtF in the regulation of PG-OM linkages to maintain the structural integrity of the bacterial cell envelope.
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13
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New approaches and techniques for bacterial cell wall analysis. Curr Opin Microbiol 2021; 60:88-95. [PMID: 33631455 DOI: 10.1016/j.mib.2021.01.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 01/22/2021] [Accepted: 01/22/2021] [Indexed: 12/17/2022]
Abstract
Peptidoglycan (PG) has remained for decades in the spotlight of the never-ending battle against pathogenic bacteria as this essential bacterial structure is one of the most successful targets for antibiotics. Most of our current understanding about the composition, architecture, and dynamics of the PG relies on techniques which have experienced great technological and methodological improvements in the past years. Here we summarize recent advances in these methods with the intention to furnish a valuable resource for both PG experts and newcomers.
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14
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Schäfer AB, Wenzel M. A How-To Guide for Mode of Action Analysis of Antimicrobial Peptides. Front Cell Infect Microbiol 2020; 10:540898. [PMID: 33194788 PMCID: PMC7604286 DOI: 10.3389/fcimb.2020.540898] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 09/18/2020] [Indexed: 12/11/2022] Open
Abstract
Antimicrobial peptides (AMPs) are a promising alternative to classical antibiotics in the fight against multi-resistant bacteria. They are produced by organisms from all domains of life and constitute a nearly universal defense mechanism against infectious agents. No drug can be approved without information about its mechanism of action. In order to use them in a clinical setting, it is pivotal to understand how AMPs work. While many pore-forming AMPs are well-characterized in model membrane systems, non-pore-forming peptides are often poorly understood. Moreover, there is evidence that pore formation may not happen or not play a role in vivo. It is therefore imperative to study how AMPs interact with their targets in vivo and consequently kill microorganisms. This has been difficult in the past, since established methods did not provide much mechanistic detail. Especially, methods to study membrane-active compounds have been scarce. Recent advances, in particular in microscopy technology and cell biological labeling techniques, now allow studying mechanisms of AMPs in unprecedented detail. This review gives an overview of available in vivo methods to investigate the antibacterial mechanisms of AMPs. In addition to classical mode of action classification assays, we discuss global profiling techniques, such as genomic and proteomic approaches, as well as bacterial cytological profiling and other cell biological assays. We cover approaches to determine the effects of AMPs on cell morphology, outer membrane, cell wall, and inner membrane properties, cellular macromolecules, and protein targets. We particularly expand on methods to examine cytoplasmic membrane parameters, such as composition, thickness, organization, fluidity, potential, and the functionality of membrane-associated processes. This review aims to provide a guide for researchers, who seek a broad overview of the available methodology to study the mechanisms of AMPs in living bacteria.
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Affiliation(s)
| | - Michaela Wenzel
- Division of Chemical Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
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15
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Wood TE, Howard SA, Förster A, Nolan LM, Manoli E, Bullen NP, Yau HCL, Hachani A, Hayward RD, Whitney JC, Vollmer W, Freemont PS, Filloux A. The Pseudomonas aeruginosa T6SS Delivers a Periplasmic Toxin that Disrupts Bacterial Cell Morphology. Cell Rep 2020; 29:187-201.e7. [PMID: 31577948 PMCID: PMC6899460 DOI: 10.1016/j.celrep.2019.08.094] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 07/02/2019] [Accepted: 08/27/2019] [Indexed: 01/10/2023] Open
Abstract
The type VI secretion system (T6SS) is crucial in interbacterial competition and is a virulence determinant of many Gram-negative bacteria. Several T6SS effectors are covalently fused to secreted T6SS structural components such as the VgrG spike for delivery into target cells. In Pseudomonas aeruginosa, the VgrG2b effector was previously proposed to mediate bacterial internalization into eukaryotic cells. In this work, we find that the VgrG2b C-terminal domain (VgrG2bC-ter) elicits toxicity in the bacterial periplasm, counteracted by a cognate immunity protein. We resolve the structure of VgrG2bC-ter and confirm it is a member of the zinc-metallopeptidase family of enzymes. We show that this effector causes membrane blebbing at midcell, which suggests a distinct type of T6SS-mediated growth inhibition through interference with cell division, mimicking the impact of β-lactam antibiotics. Our study introduces a further effector family to the T6SS arsenal and demonstrates that VgrG2b can target both prokaryotic and eukaryotic cells. The structure of the VgrG2b C-terminal domain presents a metallopeptidase fold VgrG2b exerts antibacterial activity in the periplasmic space Toxicity of VgrG2b is counteracted by a cognate periplasmic immunity protein VgrG2bC-ter-intoxicated prey cells bleb at the midcell and lyse
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Affiliation(s)
- Thomas E Wood
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Sophie A Howard
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Andreas Förster
- Section of Structural Biology, Department of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Laura M Nolan
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Eleni Manoli
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Nathan P Bullen
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4K1, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Hamish C L Yau
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Abderrahman Hachani
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Richard D Hayward
- Division of Microbiology and Parasitology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, UK
| | - John C Whitney
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4K1, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Paul S Freemont
- Section of Structural Biology, Department of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Alain Filloux
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK.
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16
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Wodzanowski KA, Cassel SE, Grimes CL, Kloxin AM. Tools for probing host-bacteria interactions in the gut microenvironment: From molecular to cellular levels. Bioorg Med Chem Lett 2020; 30:127116. [PMID: 32223923 PMCID: PMC7476074 DOI: 10.1016/j.bmcl.2020.127116] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/28/2020] [Accepted: 03/15/2020] [Indexed: 12/31/2022]
Abstract
Healthy function of the gut microenvironment is dependent on complex interactions between the bacteria of the microbiome, epithelial and immune (host) cells, and the surrounding tissue. Misregulation of these interactions is implicated in disease. A range of tools have been developed to study these interactions, from mechanistic studies to therapeutic evaluation. In this Digest, we highlight select tools at the cellular and molecular level for probing specific cell-microenvironment interactions. Approaches are overviewed for controlling and probing cell-cell interactions, from transwell and microfluidic devices to engineered bacterial peptidoglycan fragments, and cell-matrix interactions, from three-dimensional scaffolds to chemical handles for in situ modifications.
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Affiliation(s)
| | - Samantha E Cassel
- Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, United States
| | - Catherine L Grimes
- Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States; Biological Sciences, University of Delaware, Newark, DE 19716, United States.
| | - April M Kloxin
- Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, United States; Materials Science and Engineering, University of Delaware, Newark, DE 19716, United States.
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17
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Kuru E, Radkov A, Meng X, Egan A, Alvarez L, Dowson A, Booher G, Breukink E, Roper DI, Cava F, Vollmer W, Brun Y, VanNieuwenhze MS. Mechanisms of Incorporation for D-Amino Acid Probes That Target Peptidoglycan Biosynthesis. ACS Chem Biol 2019; 14:2745-2756. [PMID: 31743648 PMCID: PMC6929685 DOI: 10.1021/acschembio.9b00664] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
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Bacteria exhibit a myriad of different morphologies,
through the
synthesis and modification of their essential peptidoglycan (PG) cell
wall. Our discovery of a fluorescent D-amino acid (FDAA)-based PG labeling approach provided a powerful method
for observing how these morphological changes occur. Given that PG
is unique to bacterial cells and a common target for antibiotics,
understanding the precise mechanism(s) for incorporation of (F)DAA-based
probes is a crucial determinant in understanding the role of PG synthesis
in bacterial cell biology and could provide a valuable tool in the
development of new antimicrobials to treat drug-resistant antibacterial
infections. Here, we systematically investigate the mechanisms of
FDAA probe incorporation into PG using two model organisms Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive). Our in vitro and in vivo data unequivocally demonstrate
that these bacteria incorporate FDAAs using two extracytoplasmic pathways:
through activity of their D,D-transpeptidases, and,
if present, by their L,D-transpeptidases and not
via cytoplasmic incorporation into a D-Ala-D-Ala
dipeptide precursor. Our data also revealed the unprecedented finding
that the DAA-drug, D-cycloserine, can be incorporated into
peptide stems by each of these transpeptidases, in addition to its
known inhibitory activity against D-alanine racemase and D-Ala-D-Ala ligase. These mechanistic findings enabled
development of a new, FDAA-based, in vitro labeling approach that
reports on subcellular distribution of muropeptides, an especially
important attribute to enable the study of bacteria with poorly defined
growth modes. An improved understanding of the incorporation mechanisms
utilized by DAA-based probes is essential when interpreting results
from high resolution experiments and highlights the antimicrobial
potential of synthetic DAAs.
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Affiliation(s)
- Erkin Kuru
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Atanas Radkov
- Department of Biochemistry and Biophysics, UCSF School of Medicine, San Francisco, California 94158, United States
| | - Xin Meng
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Alexander Egan
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, NE2 4AX, United Kingdom
| | - Laura Alvarez
- Department of Molecular Biology, Umeå University, SE-901 87, Umeå, Sweden
| | - Amanda Dowson
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, United Kingdom
| | - Garrett Booher
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Eefjan Breukink
- Department of Chemistry, Utrecht University, 3584 CH, Utrecht, Netherlands
| | - David I. Roper
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, United Kingdom
| | - Felipe Cava
- Department of Molecular Biology, Umeå University, SE-901 87, Umeå, Sweden
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, NE2 4AX, United Kingdom
| | - Yves Brun
- Department of Microbiology, Infectious Diseases, and Immunology, Faculty of Medicine, Université de Montréal, Montréal, Canada
| | - Michael S. VanNieuwenhze
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, United States
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Mueller EA, Egan AJ, Breukink E, Vollmer W, Levin PA. Plasticity of Escherichia coli cell wall metabolism promotes fitness and antibiotic resistance across environmental conditions. eLife 2019; 8:40754. [PMID: 30963998 PMCID: PMC6456298 DOI: 10.7554/elife.40754] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Accepted: 03/23/2019] [Indexed: 11/13/2022] Open
Abstract
Although the peptidoglycan cell wall is an essential structural and morphological feature of most bacterial cells, the extracytoplasmic enzymes involved in its synthesis are frequently dispensable under standard culture conditions. By modulating a single growth parameter-extracellular pH-we discovered a subset of these so-called 'redundant' enzymes in Escherichia coli are required for maximal fitness across pH environments. Among these pH specialists are the class A penicillin binding proteins PBP1a and PBP1b; defects in these enzymes attenuate growth in alkaline and acidic conditions, respectively. Genetic, biochemical, and cytological studies demonstrate that synthase activity is required for cell wall integrity across a wide pH range and influences pH-dependent changes in resistance to cell wall active antibiotics. Altogether, our findings reveal previously thought to be redundant enzymes are instead specialized for distinct environmental niches. This specialization may ensure robust growth and cell wall integrity in a wide range of conditions. Editorial note This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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Affiliation(s)
- Elizabeth A Mueller
- Department of Biology, Washington University in St. Louis, St. Louis, United States
| | - Alexander Jf Egan
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Eefjan Breukink
- Membrane Biochemistry and Biophysics, Department of Chemistry, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Petra Anne Levin
- Department of Biology, Washington University in St. Louis, St. Louis, United States
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Abstract
Assembly of the division machinery in Gram-negative and Gram-positive bacteria occurs in two time-dependent steps. First, the FtsZ proto-ring localizes at midcell including some FtsN molecules. Assembly of the division machinery in Gram-negative and Gram-positive bacteria occurs in two time-dependent steps. First, the FtsZ proto-ring localizes at midcell including some FtsN molecules. Subsequently, the proteins that catalyze and regulate septal peptidoglycan (PG) synthesis are recruited including among others, the FtsBLQ-PB1B-FtsW-PBP3 complex. Further accumulation of FtsN finally allows initiation of cell division. It was known that FtsA and FtsQLB somehow prevented this initiation. Recently, A. Boes, S. Olatunji, E. Breukink, and M. Terrak (mBio 10:e01912-18, 2019, https://doi.org/10.1128/mBio.01912-18) reported that this is caused by inhibition of the activity of the PG synthases by FtsBLQ, which has to be outcompeted by accumulation of the PBP1b activating FtsN. This supports a central structural as well as regulatory role for the FtsBLQ protein complex that is conserved only in prokaryotes, making it an attractive target for antibiotic development.
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20
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Dik DA, Madukoma CS, Tomoshige S, Kim C, Lastochkin E, Boggess WC, Fisher JF, Shrout JD, Mobashery S. Slt, MltD, and MltG of Pseudomonas aeruginosa as Targets of Bulgecin A in Potentiation of β-Lactam Antibiotics. ACS Chem Biol 2019; 14:296-303. [PMID: 30620575 DOI: 10.1021/acschembio.8b01025] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The interplay between the activities of lytic transglycosylases (LTs) and penicillin-binding proteins (PBPs) is critical for the health of the bacterial cell wall. Bulgecin A (a natural-product inhibitor of LTs) potentiates the activity of β-lactam antibiotics (inhibitors of PBPs), underscoring this intimate mechanistic interdependence. Bulgecin A in the presence of an appropriate β-lactam causes bulge deformation due to the formation of aberrant peptidoglycan at the division site of the bacterium. As Pseudomonas aeruginosa, a nefarious human pathogen, has 11 LT paralogs, the answer as to which LT activity correlates with β-lactam potentiation is important and is currently unknown. Growth of P. aeruginosa PAO1 strains harboring individual transposon-insertion mutants at each of the 11 genes for LTs, in the presence of the β-lactam antibiotic ceftazidime or meropenem, implicated the gene products of slt, mltD, and mltG (of the 11), in bulge formation and potentiation. Hence, the respective enzymes would be the targets of inhibition by bulgecin A, which was indeed documented. We further demonstrated by imaging in real time and by SEM that cell lysis occurs by the structural failure of this bulge. Upon removal of the β-lactam antibiotic prior to lysis, P. aeruginosa experiences delayed recovery from the elongation and bulge phenotype in the presence of bulgecin A. These observations argue for a collaborative role for the target LTs in the repair of the aberrant cell wall, the absence of activities of which in the presence of bulgecin A results in potentiation of the β-lactam antibiotic.
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Affiliation(s)
- David A. Dik
- Department of Chemistry and Biochemistry, University of Notre Dame, 352 McCourtney Hall, Notre Dame, Indiana 46556, United States
| | - Chinedu S. Madukoma
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, Indiana 46556, United States
| | - Shusuke Tomoshige
- Department of Chemistry and Biochemistry, University of Notre Dame, 352 McCourtney Hall, Notre Dame, Indiana 46556, United States
| | - Choonkeun Kim
- Department of Chemistry and Biochemistry, University of Notre Dame, 352 McCourtney Hall, Notre Dame, Indiana 46556, United States
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry, University of Notre Dame, 352 McCourtney Hall, Notre Dame, Indiana 46556, United States
| | - William C. Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame, 352 McCourtney Hall, Notre Dame, Indiana 46556, United States
| | - Jed F. Fisher
- Department of Chemistry and Biochemistry, University of Notre Dame, 352 McCourtney Hall, Notre Dame, Indiana 46556, United States
| | - Joshua D. Shrout
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, Indiana 46556, United States
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame, 352 McCourtney Hall, Notre Dame, Indiana 46556, United States
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