1
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Alvarado Obando M, Rey-Varela D, Cava F, Dörr T. Genetic interaction mapping reveals functional relationships between peptidoglycan endopeptidases and carboxypeptidases. PLoS Genet 2024; 20:e1011234. [PMID: 38598601 PMCID: PMC11034669 DOI: 10.1371/journal.pgen.1011234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 04/22/2024] [Accepted: 03/25/2024] [Indexed: 04/12/2024] Open
Abstract
Peptidoglycan (PG) is the main component of the bacterial cell wall; it maintains cell shape while protecting the cell from internal osmotic pressure and external environmental challenges. PG synthesis is essential for bacterial growth and survival, and a series of PG modifications are required to allow expansion of the sacculus. Endopeptidases (EPs), for example, cleave the crosslinks between adjacent PG strands to allow the incorporation of newly synthesized PG. EPs are collectively essential for bacterial growth and must likely be carefully regulated to prevent sacculus degradation and cell death. However, EP regulation mechanisms are poorly understood. Here, we used TnSeq to uncover novel EP regulators in Vibrio cholerae. This screen revealed that the carboxypeptidase DacA1 (PBP5) alleviates EP toxicity. dacA1 is essential for viability on LB medium, and this essentiality was suppressed by EP overexpression, revealing that EP toxicity both mitigates, and is mitigated by, a defect in dacA1. A subsequent suppressor screen to restore viability of ΔdacA1 in LB medium identified hypomorphic mutants in the PG synthesis pathway, as well as mutations that promote EP activation. Our data thus reveal a more complex role of DacA1 in maintaining PG homeostasis than previously assumed.
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Affiliation(s)
- Manuela Alvarado Obando
- Department of Microbiology, Cornell University, Ithaca, New York, United States of America
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
| | - Diego Rey-Varela
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Center for Microbial Research (UCMR), Science for Life Laboratory (SciLifeLab), Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Felipe Cava
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Center for Microbial Research (UCMR), Science for Life Laboratory (SciLifeLab), Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Tobias Dörr
- Department of Microbiology, Cornell University, Ithaca, New York, United States of America
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
- Cornell Institute for Host-Microbe Interactions and Disease (CIHMID), Ithaca, New York, United States of America
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2
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Bartlett TM, Sisley TA, Mychack A, Walker S, Baker RW, Rudner DZ, Bernhardt TG. FacZ is a GpsB-interacting protein that prevents aberrant division-site placement in Staphylococcus aureus. Nat Microbiol 2024; 9:801-813. [PMID: 38443581 PMCID: PMC10914604 DOI: 10.1038/s41564-024-01607-y] [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: 04/24/2023] [Accepted: 01/15/2024] [Indexed: 03/07/2024]
Abstract
Staphylococcus aureus is a Gram-positive pathogen responsible for antibiotic-resistant infections. To identify vulnerabilities in cell envelope biogenesis that may overcome resistance, we enriched for S. aureus transposon mutants with defects in cell surface integrity or cell division by sorting for cells that stain with propidium iodide or have increased light-scattering properties, respectively. Transposon sequencing of the sorted populations identified more than 20 previously uncharacterized factors impacting these processes. Cells inactivated for one of these proteins, factor preventing extra Z-rings (FacZ, SAOUHSC_01855), showed aberrant membrane invaginations and multiple FtsZ cytokinetic rings. These phenotypes were suppressed in mutants lacking the conserved cell-division protein GpsB, which forms an interaction hub bridging envelope biogenesis factors with the cytokinetic ring in S. aureus. FacZ was found to interact directly with GpsB in vitro and in vivo. We therefore propose that FacZ is an envelope biogenesis factor that antagonizes GpsB function to prevent aberrant division events in S. aureus.
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Affiliation(s)
- Thomas M Bartlett
- Department of Microbiology Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Tyler A Sisley
- Department of Microbiology Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Aaron Mychack
- Department of Microbiology Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Suzanne Walker
- Department of Microbiology Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Richard W Baker
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - David Z Rudner
- Department of Microbiology Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
| | - Thomas G Bernhardt
- Department of Microbiology Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
- Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA.
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3
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Tian D, Liu Y, Zhang Y, Liu Y, Xia Y, Xu B, Xu J, Yomo T. Implementation of Fluorescent-Protein-Based Quantification Analysis in L-Form Bacteria. Bioengineering (Basel) 2024; 11:81. [PMID: 38247958 PMCID: PMC10813599 DOI: 10.3390/bioengineering11010081] [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: 12/19/2023] [Revised: 01/09/2024] [Accepted: 01/12/2024] [Indexed: 01/23/2024] Open
Abstract
Cell-wall-less (L-form) bacteria exhibit morphological complexity and heterogeneity, complicating quantitative analysis of them under internal and external stimuli. Stable and efficient labeling is needed for the fluorescence-based quantitative cell analysis of L-forms during growth and proliferation. Here, we evaluated the expression of multiple fluorescent proteins (FPs) under different promoters in the Bacillus subtilis L-form strain LR2 using confocal microscopy and imaging flow cytometry. Among others, Pylb-derived NBP3510 showed a superior performance for inducing several FPs including EGFP and mKO2 in both the wild-type and L-form strains. Moreover, NBP3510 was also active in Escherichia coli and its L-form strain NC-7. Employing these established FP-labeled strains, we demonstrated distinct morphologies in the L-form bacteria in a quantitative manner. Given cell-wall-deficient bacteria are considered protocell and synthetic cell models, the generated cell lines in our work could be valuable for L-form-based research.
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Affiliation(s)
| | | | | | | | | | | | - Jian Xu
- Laboratory of Biology and Information Science, School of Life Sciences, East China Normal University, Shanghai 200062, China
| | - Tetsuya Yomo
- Laboratory of Biology and Information Science, School of Life Sciences, East China Normal University, Shanghai 200062, China
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4
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Obando MA, Dörr T. Novel role for peptidoglycan carboxypeptidases in maintaining the balance between bacterial cell wall synthesis and degradation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.12.548665. [PMID: 37503280 PMCID: PMC10369974 DOI: 10.1101/2023.07.12.548665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Peptidoglycan (PG) is the main component of the bacterial cell wall; it maintains cell shape while protecting the cell from internal osmotic pressure and external environmental challenges. PG synthesis is essential for bacterial growth and survival, and a series of PG modifications are required to allow expansion of the sacculus. Endopeptidases (EPs), for example, cleave the crosslinks between adjacent PG strands to allow the incorporation of newly synthesized PG. EPs are collectively essential for bacterial growth and must likely be carefully regulated to prevent sacculus degradation and cell death. However, EP regulation mechanisms are poorly understood. Here, we used TnSeq to uncover novel EP regulation factors in Vibrio cholerae. This screen revealed that the carboxypeptidase DacA1 (PBP5) alleviates EP toxicity. dacA1 is essential for viability on LB medium, and this essentiality was suppressed by EP overexpression, revealing that EP toxicity both mitigates, and is mitigated by, a defect in dacA1. A subsequent suppressor screen to restore viability of ΔdacA1 in LB medium was answered by hypomorphic mutants in the PG synthesis pathway, as well as mutations that promote PG degradation. Our data thus reveal a key role of DacA1 in maintaining the balance between PG synthesis and degradation.
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Affiliation(s)
- Manuela Alvarado Obando
- Department of Microbiology, Cornell University, Ithaca, NY
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
| | - Tobias Dörr
- Department of Microbiology, Cornell University, Ithaca, NY
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
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5
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Bartlett TM, Sisley TA, Mychack A, Walker S, Baker RW, Rudner DZ, Bernhardt TG. Identification of FacZ as a division site placement factor in Staphylococcus aureus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.24.538170. [PMID: 37162900 PMCID: PMC10168275 DOI: 10.1101/2023.04.24.538170] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Staphylococcus aureus is a gram-positive pathogen responsible for life-threatening infections that are difficult to treat due to antibiotic resistance. The identification of new vulnerabilities in essential processes like cell envelope biogenesis represents a promising avenue towards the development of anti-staphylococcal therapies that overcome resistance. To this end, we performed cell sorting-based enrichments for S. aureus mutants with defects in envelope integrity and cell division. We identified many known envelope biogenesis factors as well as a large collection of new factors with roles in this process. Mutants inactivated for one of the hits, the uncharacterized SAOUHSC_01855 protein, displayed aberrant membrane invaginations and multiple FtsZ cytokinetic ring structures. This factor is broadly distributed among Firmicutes, and its inactivation in B. subtilis similarly caused division and membrane defects. We therefore renamed the protein FacZ (Firmicute-associated coordinator of Z-rings). In S. aureus, inactivation of the conserved cell division protein GpsB suppressed the division and morphological defects of facZ mutants. Additionally, FacZ and GpsB were found to interact directly in a purified system. Thus, FacZ is a novel antagonist of GpsB function with a conserved role in controlling division site placement in S. aureus and other Firmicutes.
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Affiliation(s)
- Thomas M. Bartlett
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Tyler A. Sisley
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Aaron Mychack
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Suzanne Walker
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Richard W. Baker
- Department of Biochemistry & Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - David Z. Rudner
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Thomas G. Bernhardt
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, USA
- Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts, USA
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6
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Tian D, Wang C, Liu Y, Zhang Y, Caliari A, Lu H, Xia Y, Xu B, Xu J, Yomo T. Cell Sorting-Directed Selection of Bacterial Cells in Bigger Sizes Analyzed by Imaging Flow Cytometry during Experimental Evolution. Int J Mol Sci 2023; 24:ijms24043243. [PMID: 36834655 PMCID: PMC9966196 DOI: 10.3390/ijms24043243] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/20/2023] [Accepted: 01/26/2023] [Indexed: 02/10/2023] Open
Abstract
Cell morphology is an essential and phenotypic trait that can be easily tracked during adaptation and evolution to environmental changes. Thanks to the rapid development of quantitative analytical techniques for large populations of cells based on their optical properties, morphology can be easily determined and tracked during experimental evolution. Furthermore, the directed evolution of new culturable morphological phenotypes can find use in synthetic biology to refine fermentation processes. It remains unknown whether and how fast we can obtain a stable mutant with distinct morphologies using fluorescence-activated cell sorting (FACS)-directed experimental evolution. Taking advantage of FACS and imaging flow cytometry (IFC), we direct the experimental evolution of the E. coli population undergoing continuous passage of sorted cells with specific optical properties. After ten rounds of sorting and culturing, a lineage with large cells resulting from incomplete closure of the division ring was obtained. Genome sequencing highlighted a stop-gain mutation in amiC, leading to a dysfunctional AmiC division protein. The combination of FACS-based selection with IFC analysis to track the evolution of the bacteria population in real-time holds promise to rapidly select and culture new morphologies and association tendencies with many potential applications.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Jian Xu
- Correspondence: (J.X.); (T.Y.); Tel.: +86-(21)-62233727 (J.X. & T.Y.)
| | - Tetsuya Yomo
- Correspondence: (J.X.); (T.Y.); Tel.: +86-(21)-62233727 (J.X. & T.Y.)
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7
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McDowell LL, Quinn CL, Leeds JA, Silverman JA, Silver LL. Perspective on Antibacterial Lead Identification Challenges and the Role of Hypothesis-Driven Strategies. SLAS DISCOVERY 2020; 24:440-456. [PMID: 30890054 DOI: 10.1177/2472555218818786] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
For the past three decades, the pharmaceutical industry has undertaken many diverse approaches to discover novel antibiotics, with limited success. We have witnessed and personally experienced many mistakes, hurdles, and dead ends that have derailed projects and discouraged scientists and business leaders. Of the many factors that affect the outcomes of screening campaigns, a lack of understanding of the properties that drive efflux and permeability requirements across species has been a major barrier for advancing hits to leads. Hits that possess bacterial spectrum have seldom also possessed druglike properties required for developability and safety. Persistence in solving these two key barriers is necessary for the reinvestment into discovering antibacterial agents. This perspective narrates our experience in antibacterial discovery-our lessons learned about antibacterial challenges as well as best practices for screening strategies. One of the tenets that guides us is that drug discovery is a hypothesis-driven science. Application of this principle, at all steps in the antibacterial discovery process, should improve decision making and possibly the odds of what has become, in recent decades, an increasingly challenging endeavor with dwindling success rates.
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Affiliation(s)
- Laura L McDowell
- 1 Novartis Institutes for Biomedical Research, Emeryville, CA, USA
| | | | - Jennifer A Leeds
- 1 Novartis Institutes for Biomedical Research, Emeryville, CA, USA
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8
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Godinez WJ, Chan H, Hossain I, Li C, Ranjitkar S, Rasper D, Simmons RL, Zhang X, Feng BY. Morphological Deconvolution of Beta-Lactam Polyspecificity in E. coli. ACS Chem Biol 2019; 14:1217-1226. [PMID: 31184469 DOI: 10.1021/acschembio.9b00141] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Beta-lactams comprise one of the earliest classes of antibiotic therapies. These molecules covalently inhibit enzymes from the family of penicillin-binding proteins (PBPs), which are essential in construction of the bacterial cell wall. As a result, beta-lactams cause striking changes to cellular morphology, the nature of which varies by the range of PBPs simultaneously engaged in the cell. The traditional method of exploring beta-lactam polyspecificity is a gel-based binding assay which is low-throughput and typically is run ex situ in cell extracts. Here, we describe a medium-throughput, image-based assay combined with machine learning methods to automatically profile the activity of beta-lactams in E. coli cells. By testing for morphological change across a panel of strains with perturbations to individual PBP enzymes, our approach automatically and quantifiably relates different beta-lactam antibiotics according to their preferences for individual PBPs in cells. We show the potential of our approach for guiding the design of novel inhibitors toward different PBP-binding profiles by predicting the mechanisms of two recently reported PBP inhibitors.
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Affiliation(s)
- William J. Godinez
- Chemical Biology and Therapeutics, Novartis Institutes for BioMedical Research, Basel, Switzerland
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, California, United States
| | - Helen Chan
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, California, United States
| | - Imtiaz Hossain
- Chemical Biology and Therapeutics, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Cindy Li
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, California, United States
| | - Srijan Ranjitkar
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, California, United States
| | - Dita Rasper
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, California, United States
| | - Robert L. Simmons
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, California, United States
| | - Xian Zhang
- Chemical Biology and Therapeutics, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Brian Y. Feng
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, California, United States
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9
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Cesar S, Huang KC. Thinking big: the tunability of bacterial cell size. FEMS Microbiol Rev 2017; 41:672-678. [PMID: 28961755 DOI: 10.1093/femsre/fux026] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 05/10/2017] [Indexed: 11/13/2022] Open
Abstract
The determination of cell size is a fundamental challenge for all living organisms. In a given growth condition, cell size for a particular bacterial species typically falls within a narrow distribution. Nonetheless, size can vary enormously across species, and the size of a single bacterium can even vary substantially across growth conditions. Recent phenomenological studies have revived classic interest in how cells maintain their size and how they adjust their size with changes in growth rate. However, the mechanisms by which cells establish a particular size are relatively enigmatic. Here, we review existing knowledge on how size in rod-shaped bacteria is shaped by nutrient, mechanical, and genetic factors. We also examine obstacles to accurate size measurement and recent technologies that help to overcome these hurdles. Finally, we discuss the relevance of cell size to bacterial physiology.
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Affiliation(s)
- Spencer Cesar
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Kerwyn Casey Huang
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.,Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
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10
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Shi H, Colavin A, Bigos M, Tropini C, Monds RD, Huang KC. Deep Phenotypic Mapping of Bacterial Cytoskeletal Mutants Reveals Physiological Robustness to Cell Size. Curr Biol 2017; 27:3419-3429.e4. [DOI: 10.1016/j.cub.2017.09.065] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Revised: 08/31/2017] [Accepted: 09/29/2017] [Indexed: 11/25/2022]
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11
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van Teeseling MCF, de Pedro MA, Cava F. Determinants of Bacterial Morphology: From Fundamentals to Possibilities for Antimicrobial Targeting. Front Microbiol 2017; 8:1264. [PMID: 28740487 PMCID: PMC5502672 DOI: 10.3389/fmicb.2017.01264] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 06/23/2017] [Indexed: 12/11/2022] Open
Abstract
Bacterial morphology is extremely diverse. Specific shapes are the consequence of adaptive pressures optimizing bacterial fitness. Shape affects critical biological functions, including nutrient acquisition, motility, dispersion, stress resistance and interactions with other organisms. Although the characteristic shape of a bacterial species remains unchanged for vast numbers of generations, periodical variations occur throughout the cell (division) and life cycles, and these variations can be influenced by environmental conditions. Bacterial morphology is ultimately dictated by the net-like peptidoglycan (PG) sacculus. The species-specific shape of the PG sacculus at any time in the cell cycle is the product of multiple determinants. Some morphological determinants act as a cytoskeleton to guide biosynthetic complexes spatiotemporally, whereas others modify the PG sacculus after biosynthesis. Accumulating evidence supports critical roles of morphogenetic processes in bacteria-host interactions, including pathogenesis. Here, we review the molecular determinants underlying morphology, discuss the evidence linking bacterial morphology to niche adaptation and pathogenesis, and examine the potential of morphological determinants as antimicrobial targets.
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Affiliation(s)
- Muriel C F van Teeseling
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Miguel A de Pedro
- Centro de Biología Molecular "Severo Ochoa" - Consejo Superior de Investigaciones Científicas, Universidad Autónoma de MadridMadrid, Spain
| | - Felipe Cava
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
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12
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Ude C, Ben-Dov N, Jochums A, Li Z, Segal E, Scheper T, Beutel S. Online analysis of protein inclusion bodies produced in E. coli by monitoring alterations in scattered and reflected light. Appl Microbiol Biotechnol 2016; 100:4147-59. [PMID: 26940052 DOI: 10.1007/s00253-016-7403-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 02/15/2016] [Accepted: 02/17/2016] [Indexed: 12/29/2022]
Abstract
The online monitoring of recombinant protein aggregate inclusion bodies during microbial cultivation is an immense challenge. Measurement of scattered and reflected light offers a versatile and non-invasive measurement technique. Therefore, we investigated two methods to detect the formation of inclusion bodies and monitor their production: (1) online 180° scattered light measurement (λ = 625 nm) using a sensor platform during cultivation in shake flask and (2) online measurement of the light reflective interference using a porous Si-based optical biosensor (SiPA). It could be shown that 180° scattered light measurement allows monitoring of alterations in the optical properties of Escherichia coli BL21 cells, associated with the formation of inclusion bodies during cultivation. A reproducible linear correlation between the inclusion body concentration of the non-fluorescent protein human leukemia inhibitory factor (hLIF) carrying a thioredoxin tag and the shift ("Δamp") in scattered light signal intensity was observed. This was also observed for the glutathione-S-transferase-tagged green fluorescent protein (GFP-GST). Continuous online monitoring of reflective interference spectra reveals a significant increase in the bacterium refractive index during hLIF production in comparison to a non-induced reference that coincide with the formation of inclusion bodies. These online monitoring techniques could be applied for fast and cost-effective screening of different protein expression systems.
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Affiliation(s)
- Christian Ude
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany
| | - Nadav Ben-Dov
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, 32000, Haifa, Israel
| | - André Jochums
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany
| | - Zhaopeng Li
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany
| | - Ester Segal
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, 32000, Haifa, Israel
| | - Thomas Scheper
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany
| | - Sascha Beutel
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany.
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13
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Jorgenson MA, Kannan S, Laubacher ME, Young KD. Dead-end intermediates in the enterobacterial common antigen pathway induce morphological defects in Escherichia coli by competing for undecaprenyl phosphate. Mol Microbiol 2015; 100:1-14. [PMID: 26593043 DOI: 10.1111/mmi.13284] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/2015] [Indexed: 01/31/2023]
Abstract
Bacterial morphology is determined primarily by the architecture of the peptidoglycan (PG) cell wall, a mesh-like layer that encases the cell. To identify novel mechanisms that create or maintain cell shape in Escherichia coli, we used flow cytometry to screen a transposon insertion library and identified a wecE mutant that altered cell shape, causing cells to filament and swell. WecE is a sugar aminotransferase involved in the biosynthesis of enterobacterial common antigen (ECA), a non-essential outer membrane glycolipid of the Enterobacteriaceae. Loss of wecE interrupts biosynthesis of ECA and causes the accumulation of the undecaprenyl pyrophosphate-linked intermediate ECA-lipid II. The wecE shape defects were reversed by: (i) preventing initiation of ECA biosynthesis, (ii) increasing the synthesis of the lipid carrier undecaprenyl phosphate (Und-P), (iii) diverting Und-P to PG synthesis or (iv) promoting Und-P recycling. The results argue that the buildup of ECA-lipid II sequesters part of the pool of Und-P, which, in turn, adversely affects PG synthesis. The data strongly suggest there is competition for a common pool of Und-P, whose proper distribution to alternate metabolic pathways is required to maintain normal cell shape in E. coli.
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Affiliation(s)
- Matthew A Jorgenson
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Suresh Kannan
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Mary E Laubacher
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Kevin D Young
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
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14
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Baker CA, Rubinelli PM, Park SH, Ricke SC. Immuno-based detection of Shiga toxin-producing pathogenic Escherichia coli in food – A review on current approaches and potential strategies for optimization. Crit Rev Microbiol 2015; 42:656-75. [DOI: 10.3109/1040841x.2015.1009824] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Christopher A. Baker
- Department of Food Science, Center for Food Safety, University of Arkansas, Fayetteville, AR, USA
| | - Peter M. Rubinelli
- Department of Food Science, Center for Food Safety, University of Arkansas, Fayetteville, AR, USA
| | - Si Hong Park
- Department of Food Science, Center for Food Safety, University of Arkansas, Fayetteville, AR, USA
| | - Steven C. Ricke
- Department of Food Science, Center for Food Safety, University of Arkansas, Fayetteville, AR, USA
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15
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Comparison of the RAPID-B® flow cytometer and the BAX® system for the detection of non-O157 shiga toxin-producing Escherichia coli (STEC) in beef products. Food Control 2015. [DOI: 10.1016/j.foodcont.2014.08.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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16
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Kumarasiri M, Zhang W, Shi Q, Fisher JF, Mobashery S. Protonation states of active-site lysines of penicillin-binding protein 6 from Escherichia coli and the mechanistic implications. Proteins 2014; 82:1348-58. [PMID: 24375650 DOI: 10.1002/prot.24501] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 11/15/2013] [Accepted: 12/09/2013] [Indexed: 02/02/2023]
Abstract
The protonation states of the two active-site lysines (Lys69 and Lys235) of PBP 6 of Escherichia coli were explored to understand the active site chemistry of this enzyme. Each lysine was individually mutated to cysteine, and the resultant two mutant proteins were purified to homogeneity. Each protein was denatured, and its cysteine was chemically modified to produce an S-aminoethylated cysteine (γ-thialysine) residue. Following renaturation, the evaluation of the kinetics of the dd-carboxypeptidase activity of PBP 6 as a function of pH was found consistent with one lysine in its free-base (Lys69) and the other in the protonated state (Lys235) for optimal catalysis. The experimental estimates for their pKa values were compared with the pKa values calculated computationally, using molecular-dynamics simulations and a thermodynamic cycle. Study of the γ-thialysine69 showed that lysine at position 69 influenced the basic limb of catalysis, consistent with the fact that the two lysine side chains are in proximity to each other in the active site. Based on these observations, a reaction sequence for PBP 6 is proposed, wherein protonated Lys235 serves as the electrostatic substrate anchor and Lys69 as the conduit for protons in the course of the acylation and deacylation half-reactions.
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Affiliation(s)
- Malika Kumarasiri
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556
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The dynamics of peptidoglycan structure and function: conference report on the 3rd Great Wall Symposium. Res Microbiol 2013; 165:60-7. [PMID: 24239960 DOI: 10.1016/j.resmic.2013.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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18
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Sycuro LK, Rule CS, Petersen TW, Wyckoff TJ, Sessler T, Nagarkar DB, Khalid F, Pincus Z, Biboy J, Vollmer W, Salama NR. Flow cytometry-based enrichment for cell shape mutants identifies multiple genes that influence Helicobacter pylori morphology. Mol Microbiol 2013; 90:869-83. [PMID: 24112477 PMCID: PMC3844677 DOI: 10.1111/mmi.12405] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/17/2013] [Indexed: 12/17/2022]
Abstract
The helical cell shape of Helicobacter pylori is highly conserved and contributes to its ability to swim through and colonize the viscous gastric mucus layer. A multi-faceted peptidoglycan (PG) modification programme involving four recently characterized peptidases and two accessory proteins is essential for maintaining H. pylori's helicity. To expedite identification of additional shape-determining genes, we employed flow cytometry with fluorescence-activated cell sorting (FACS) to enrich a transposon library for bacterial cells with altered light scattering profiles that correlate with perturbed cell morphology. After a single round of sorting, 15% of our clones exhibited a stable cell shape defect, reflecting 37-fold enrichment. Sorted clones with straight rod morphology contained insertions in known PG peptidases, as well as an insertion in csd6, which we demonstrated has ld-carboxypeptidase activity and cleaves monomeric tetrapeptides in the PG sacculus, yielding tripeptides. Other mutants had only slight changes in helicity due to insertions in genes encoding MviN/MurJ, a protein possibly involved in initiating PG synthesis, and the hypothetical protein HPG27_782. Our findings demonstrate FACS robustly detects perturbations of bacterial cell shape and identify additional PG peptide modifications associated with helical cell shape in H. pylori.
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Affiliation(s)
- Laura K Sycuro
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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Frirdich E, Gaynor EC. Peptidoglycan hydrolases, bacterial shape, and pathogenesis. Curr Opin Microbiol 2013; 16:767-78. [PMID: 24121030 DOI: 10.1016/j.mib.2013.09.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/08/2013] [Accepted: 09/11/2013] [Indexed: 01/29/2023]
Abstract
Bacterial shape has always been hypothesized to play an important role in the biology of a species and in the ability of certain bacteria to influence human health. The recent discovery of peptidoglycan hydrolases that modulate shape has now allowed this hypothesis to be addressed directly. Genetic, biochemical, and phenotypic studies have found that changes in shape and underlying peptidoglycan structure influence many pathogenic attributes including surviving unfavorable conditions, predation, transmission, colonization, and host interactions. The diversity of bacterial shapes, niches, and lifestyles is also reflected in diverse mechanisms of hydrolase regulation, critical for maintaining peptidoglycan integrity and biological properties of the cell. Future studies will build on the current work described and further elucidate the intersection of peptidoglycan hydrolase activity, shape, and disease outcome.
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Affiliation(s)
- Emilisa Frirdich
- Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T1Z3
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Diverse functions for six glycosyltransferases in Caulobacter crescentus cell wall assembly. J Bacteriol 2013; 195:4527-35. [PMID: 23935048 DOI: 10.1128/jb.00600-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The essential process of peptidoglycan synthesis requires two enzymatic activities, transpeptidation and transglycosylation. While the PBP2 and PBP3 transpeptidases perform highly specialized functions that are widely conserved, the specific roles of different glycosyltransferases are poorly understood. For example, Caulobacter crescentus encodes six glycosyltransferase paralogs of largely unknown function. Using genetic analyses, we found that Caulobacter glycosyltransferases are primarily redundant but that PbpX is responsible for most of the essential glycosyltransferase activity. Cells containing PbpX as their sole glycosyltransferase are viable, and the loss of pbpX leads to a general defect in the integrity of the cell wall structure even in the presence of the other five glycosyltransferases. However, neither PbpX nor any of its paralogs is required for the specific processes of cell elongation or division, while the cell wall synthesis required for stalk biogenesis is only partially disrupted in several of the glycosyltransferase mutants. Despite their genetic redundancy, Caulobacter glycosyltransferases exhibit different subcellular localizations. We suggest that these enzymes have specialized roles and normally function in distinct subcomplexes but retain the ability to substitute for one another so as to ensure the robustness of the peptidoglycan synthesis process.
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Eliminating a set of four penicillin binding proteins triggers the Rcs phosphorelay and Cpx stress responses in Escherichia coli. J Bacteriol 2013; 195:4415-24. [PMID: 23893115 DOI: 10.1128/jb.00596-13] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Penicillin binding proteins (PBPs) are responsible for synthesizing and modifying the bacterial cell wall, and in Escherichia coli the loss of several nonessential low-molecular-weight PBPs gives rise to abnormalities in cell shape and division. To determine whether these proteins help connect the flagellar basal body to the peptidoglycan wall, we surveyed a set of PBP mutants and found that motility in an agar migration assay was compromised by the simultaneous absence of four enzymes: PBP4, PBP5, PBP7, and AmpH. A wild-type copy of any one of these restored migration, and complementation depended on the integrity of the PBP active-site serine. However, the migration defect was caused by the absence of flagella instead of improper flagellar assembly. Migration was restored if the flhDC genes were overexpressed or if the rcsB or cpxR genes were deleted. Thus, migration was inhibited because the Rcs and Cpx stress response systems were induced in the absence of these four specific PBPs. Furthermore, in this situation Rcs induction depended on the presence of CpxR. The results imply that small changes in peptidoglycan structure are sufficient to activate these stress responses, suggesting that a specific cell wall fragment may be the signal being sensed. The fact that four PBPs must be inactivated may explain why large perturbations to the envelope are required to induce stress responses.
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Structural analysis of the role of Pseudomonas aeruginosa penicillin-binding protein 5 in β-lactam resistance. Antimicrob Agents Chemother 2013; 57:3137-46. [PMID: 23629710 DOI: 10.1128/aac.00505-13] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Penicillin-binding protein 5 (PBP5) is one of the most abundant PBPs in Pseudomonas aeruginosa. Although its main function is that of a cell wall dd-carboxypeptidase, it possesses sufficient β-lactamase activity to contribute to the ability of P. aeruginosa to resist the antibiotic activity of the β-lactams. The study of these dual activities is important for understanding the mechanisms of antibiotic resistance by P. aeruginosa, an important human pathogen, and to the understanding of the evolution of β-lactamase activity from the PBP enzymes. We purified a soluble version of P. aeruginosa PBP5 (designated Pa sPBP5) by deletion of its C-terminal membrane anchor. Under in vitro conditions, Pa sPBP5 demonstrates both dd-carboxypeptidase and expanded-spectrum β-lactamase activities. Its crystal structure at a 2.05-Å resolution shows features closely resembling those of the class A β-lactamases, including a shortened loop spanning residues 74 to 78 near the active site and with respect to the conformations adopted by two active-site residues, Ser101 and Lys203. These features are absent in the related PBP5 of Escherichia coli. A comparison of the two Pa sPBP5 monomers in the asymmetric unit, together with molecular dynamics simulations, revealed an active-site flexibility that may explain its carbapenemase activity, a function that is absent in the E. coli PBP5 enzyme. Our functional and structural characterizations underscore the versatility of this PBP5 in contributing to the β-lactam resistance of P. aeruginosa while highlighting how broader β-lactamase activity may be encoded in the structural folds shared by the PBP and serine β-lactamase classes.
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