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Yan Q, Gomis Perez C, Karatekin E. Cell Membrane Tension Gradients, Membrane Flows, and Cellular Processes. Physiology (Bethesda) 2024; 39:0. [PMID: 38501962 DOI: 10.1152/physiol.00007.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 03/18/2024] [Accepted: 03/18/2024] [Indexed: 03/20/2024] Open
Abstract
Cell membrane tension affects and is affected by many fundamental cellular processes, yet it is poorly understood. Recent experiments show that membrane tension can propagate at vastly different speeds in different cell types, reflecting physiological adaptations. Here we briefly review the current knowledge about membrane tension gradients, membrane flows, and their physiological context.
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Affiliation(s)
- Qi Yan
- Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States
| | - Carolina Gomis Perez
- Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States
| | - Erdem Karatekin
- Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States
- Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States
- Wu Tsai Institute, Yale University, New Haven, Connecticut, United States
- Saints-Pères Paris Institute for the Neurosciences (SPPIN), Centre National de la Recherche Scientifique (CNRS), Paris, France
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2
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Serrano M, Martins D, Henriques AO. Clostridioides difficile Sporulation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1435:273-314. [PMID: 38175480 DOI: 10.1007/978-3-031-42108-2_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Some members of the Firmicutes phylum, including many members of the human gut microbiota, are able to differentiate a dormant and highly resistant cell type, the endospore (hereinafter spore for simplicity). Spore-formers can colonize virtually any habitat and, because of their resistance to a wide variety of physical and chemical insults, spores can remain viable in the environment for long periods of time. In the anaerobic enteric pathogen Clostridioides difficile the aetiologic agent is the oxygen-resistant spore, while the toxins produced by actively growing cells are the main cause of the disease symptoms. Here, we review the regulatory circuits that govern entry into sporulation. We also cover the role of spores in the infectious cycle of C. difficile in relation to spore structure and function and the main control points along spore morphogenesis.
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Affiliation(s)
- Mónica Serrano
- Instituto de Tecnologia Química e Biológica António Xavier, Oeiras, Portugal.
| | - Diogo Martins
- Instituto de Tecnologia Química e Biológica António Xavier, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica António Xavier, Oeiras, Portugal
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3
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Lablaine A, Chamot S, Serrano M, Billaudeau C, Bornard I, Carballido-López R, Carlin F, Henriques AO, Broussolle V. A new fluorescence-based approach for direct visualization of coat formation during sporulation in Bacillus cereus. Sci Rep 2023; 13:15136. [PMID: 37704668 PMCID: PMC10499802 DOI: 10.1038/s41598-023-42143-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 09/06/2023] [Indexed: 09/15/2023] Open
Abstract
The human pathogenic bacteria Bacillus cereus, Bacillus anthracis and the entomopathogenic Bacillus thuringiensis form spores encased in a protein coat surrounded by a balloon-like exosporium. These structures mediate spore interactions with its environment, including the host immune system, control the transit of molecules that trigger germination and thus are essential for the spore life cycle. Formation of the coat and exosporium has been traditionally visualized by transmission electronic microscopy on fixed cells. Recently, we showed that assembly of the exosporium can be directly observed in live B. cereus cells by super resolution-structured illumination microscopy (SR-SIM) using the membrane MitoTrackerGreen (MTG) dye. Here, we demonstrate that the different steps of coat formation can also be visualized by SR-SIM using MTG and SNAP-cell TMR-star dyes during B. cereus sporulation. We used these markers to characterize a subpopulation of engulfment-defective B. cereus cells that develops at a suboptimal sporulation temperature. Importantly, we predicted and confirmed that synthesis and accumulation of coat material, as well as synthesis of the σK-dependent protein BxpB, occur in cells arrested during engulfment. These results suggest that, unlike the well-studied model organism Bacillus subtilis, the activity of σK is not strictly linked to the state of forespore development in B. cereus.
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Affiliation(s)
- Armand Lablaine
- INRAE, Avignon Université, UMR SQPOV, 84000, Avignon, France
- MICALIS Institute, INRAE, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | | | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2780-157, Oeiras, Portugal
| | - Cyrille Billaudeau
- MICALIS Institute, INRAE, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | | | - Rut Carballido-López
- MICALIS Institute, INRAE, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | - Frédéric Carlin
- INRAE, Avignon Université, UMR SQPOV, 84000, Avignon, France
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2780-157, Oeiras, Portugal
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4
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Comparative transcriptome analysis reveals the biocontrol mechanism of Bacillus velezensis E68 against Fusarium graminearum DAOMC 180378, the causal agent of Fusarium head blight. PLoS One 2023; 18:e0277983. [PMID: 36701319 PMCID: PMC9879434 DOI: 10.1371/journal.pone.0277983] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 11/07/2022] [Indexed: 01/27/2023] Open
Abstract
Fusarium graminearum is the causal agent of Fusarium Head Blight, a serious disease affecting grain crops worldwide. Biological control involves the use of microorganisms to combat plant pathogens such as F. graminearum. Strains of Bacillus velezensis are common biological control candidates for use against F. graminearum and other plant pathogens, as they can secrete antifungal secondary metabolites. Here we study the interaction between B. velezensis E68 and F. graminearum DAOMC 180378 by employing a dual RNA-seq approach to assess the transcriptional changes in both organisms. In dual culture, B. velezensis up-regulated genes related to sporulation and phosphate stress and down-regulated genes related to secondary metabolism, biofilm formation and the tricarboxylic acid cycle. F. graminearum up-regulated genes encoding for killer protein 4-like proteins and genes relating to heavy metal tolerance, and down-regulated genes relating to trichothecene biosynthesis and phenol metabolism. This study provides insight into the molecular mechanisms involved in the interaction between a biocontrol bacterium and a phytopathogenic fungus.
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5
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Landajuela A, Braun M, Martínez-Calvo A, Rodrigues CDA, Gomis Perez C, Doan T, Rudner DZ, Wingreen NS, Karatekin E. Membrane fission during bacterial spore development requires cellular inflation driven by DNA translocation. Curr Biol 2022; 32:4186-4200.e8. [PMID: 36041438 PMCID: PMC9730832 DOI: 10.1016/j.cub.2022.08.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 04/26/2022] [Accepted: 08/08/2022] [Indexed: 12/14/2022]
Abstract
Bacteria require membrane fission for both cell division and endospore formation. In Bacillus subtilis, sporulation initiates with an asymmetric division that generates a large mother cell and a smaller forespore that contains only a quarter of its genome. As the mother cell membranes engulf the forespore, a DNA translocase pumps the rest of the chromosome into the small forespore compartment, inflating it due to increased turgor. When the engulfing membrane undergoes fission, the forespore is released into the mother cell cytoplasm. The B. subtilis protein FisB catalyzes membrane fission during sporulation, but the molecular basis is unclear. Here, we show that forespore inflation and FisB accumulation are both required for an efficient membrane fission. Forespore inflation leads to higher membrane tension in the engulfment membrane than in the mother cell membrane, causing the membrane to flow through the neck connecting the two membrane compartments. Thus, the mother cell supplies some of the membrane required for the growth of the membranes surrounding the forespore. The oligomerization of FisB at the membrane neck slows the equilibration of membrane tension by impeding the membrane flow. This leads to a further increase in the tension of the engulfment membrane, promoting its fission through lysis. Collectively, our data indicate that DNA translocation has a previously unappreciated second function in energizing the FisB-mediated membrane fission under energy-limited conditions.
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Affiliation(s)
- Ane Landajuela
- Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA.
| | - Martha Braun
- Nanobiology Institute, Yale University, West Haven, CT, USA; Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
| | - Alejandro Martínez-Calvo
- Princeton Center for Theoretical Science, Princeton University, Princeton, NJ 08544, USA; Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | | | - Carolina Gomis Perez
- Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA
| | - Thierry Doan
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Aix-Marseille Université-CNRS UMR7255, Marseilles, France
| | - David Z Rudner
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Ned S Wingreen
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Erdem Karatekin
- Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA; Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA; Université de Paris, Saints-Pères Paris Institute for the Neurosciences (SPPIN), Centre National de la Recherche Scientifique (CNRS), 75006 Paris, France.
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6
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Genetic Screens Identify Additional Genes Implicated in Envelope Remodeling during the Engulfment Stage of Bacillus subtilis Sporulation. mBio 2022; 13:e0173222. [PMID: 36066101 PMCID: PMC9600426 DOI: 10.1128/mbio.01732-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During bacterial endospore formation, the developing spore is internalized into the mother cell through a phagocytic-like process called engulfment, which involves synthesis and hydrolysis of peptidoglycan. Engulfment peptidoglycan hydrolysis requires the widely conserved and well-characterized DMP complex, composed of SpoIID, SpoIIM, and SpoIIP. In contrast, although peptidoglycan synthesis has been implicated in engulfment, the protein players involved are less well defined. The widely conserved SpoIIIAH-SpoIIQ interaction is also required for engulfment efficiency, functioning like a ratchet to promote membrane migration around the forespore. Here, we screened for additional factors required for engulfment using transposon sequencing in Bacillus subtilis mutants with mild engulfment defects. We discovered that YrvJ, a peptidoglycan hydrolase, and the MurA paralog MurAB, involved in peptidoglycan precursor synthesis, are required for efficient engulfment. Cytological analyses suggest that both factors are important for engulfment when the DMP complex is compromised and that MurAB is additionally required when the SpoIIIAH-SpoIIQ ratchet is abolished. Interestingly, despite the importance of MurAB for sporulation in B. subtilis, phylogenetic analyses of MurA paralogs indicate that there is no correlation between sporulation and the number of MurA paralogs and further reveal the existence of a third MurA paralog, MurAC, within the Firmicutes. Collectively, our studies identify two new factors that are required for efficient envelop remodeling during sporulation and highlight the importance of peptidoglycan precursor synthesis for efficient engulfment in B. subtilis and likely other endospore-forming bacteria.
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7
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Chan H, Mohamed AMT, Grainge I, Rodrigues CDA. FtsK and SpoIIIE, coordinators of chromosome segregation and envelope remodeling in bacteria. Trends Microbiol 2021; 30:480-494. [PMID: 34728126 DOI: 10.1016/j.tim.2021.10.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 10/05/2021] [Accepted: 10/06/2021] [Indexed: 10/19/2022]
Abstract
The translocation of DNA during bacterial cytokinesis is mediated by the SpoIIIE/FtsK family of proteins. These proteins ensure efficient chromosome segregation into sister cells by ATP-driven translocation of DNA and they control chromosome dimer resolution. How FtsK/SpoIIIE mediate chromosome translocation during cytokinesis in Gram-positive and Gram-negative organisms has been the subject of debate. Studies on FtsK in Escherichia coli, and recent work on SpoIIIE in Bacillus subtilis, have identified interactions between each translocase and the division machinery, supporting the idea that SpoIIIE and FtsK coordinate the final steps of cytokinesis with completion of chromosome segregation. Here we summarize and discuss the view that SpoIIIE and FtsK play similar roles in coordinating cytokinesis with chromosome segregation, during growth and differentiation.
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Affiliation(s)
- Helena Chan
- iThree Institute, University of Technology, Sydney, NSW, Australia
| | | | - Ian Grainge
- School of Environmental and Life Sciences, University of Newcastle, NSW, Australia.
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8
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Landajuela A, Braun M, Rodrigues CDA, Martínez-Calvo A, Doan T, Horenkamp F, Andronicos A, Shteyn V, Williams ND, Lin C, Wingreen NS, Rudner DZ, Karatekin E. FisB relies on homo-oligomerization and lipid binding to catalyze membrane fission in bacteria. PLoS Biol 2021; 19:e3001314. [PMID: 34185788 PMCID: PMC8274934 DOI: 10.1371/journal.pbio.3001314] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Revised: 07/12/2021] [Accepted: 06/07/2021] [Indexed: 11/18/2022] Open
Abstract
Little is known about mechanisms of membrane fission in bacteria despite their requirement for cytokinesis. The only known dedicated membrane fission machinery in bacteria, fission protein B (FisB), is expressed during sporulation in Bacillus subtilis and is required to release the developing spore into the mother cell cytoplasm. Here, we characterized the requirements for FisB-mediated membrane fission. FisB forms mobile clusters of approximately 12 molecules that give way to an immobile cluster at the engulfment pole containing approximately 40 proteins at the time of membrane fission. Analysis of FisB mutants revealed that binding to acidic lipids and homo-oligomerization are both critical for targeting FisB to the engulfment pole and membrane fission. Experiments using artificial membranes and filamentous cells suggest that FisB does not have an intrinsic ability to sense or induce membrane curvature but can bridge membranes. Finally, modeling suggests that homo-oligomerization and trans-interactions with membranes are sufficient to explain FisB accumulation at the membrane neck that connects the engulfment membrane to the rest of the mother cell membrane during late stages of engulfment. Together, our results show that FisB is a robust and unusual membrane fission protein that relies on homo-oligomerization, lipid binding, and the unique membrane topology generated during engulfment for localization and membrane scission, but surprisingly, not on lipid microdomains, negative-curvature lipids, or curvature sensing.
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Affiliation(s)
- Ane Landajuela
- Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States of America
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States of America
| | - Martha Braun
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States of America
- Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America
| | | | | | - Thierry Doan
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Aix-Marseille Université, Marseilles, France
| | - Florian Horenkamp
- Cell Biology, Yale University, New Haven, Connecticut, United States of America
| | - Anna Andronicos
- Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States of America
| | - Vladimir Shteyn
- Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States of America
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States of America
| | - Nathan D Williams
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States of America
- Cell Biology, Yale University, New Haven, Connecticut, United States of America
| | - Chenxiang Lin
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States of America
- Cell Biology, Yale University, New Haven, Connecticut, United States of America
| | - Ned S Wingreen
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - David Z Rudner
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Erdem Karatekin
- Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States of America
- Nanobiology Institute, Yale University, West Haven, Connecticut, United States of America
- Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America
- Université de Paris, SPPIN-Saints-Pères Paris Institute for the Neurosciences, Centre National de la Recherche Scientifique (CNRS), Paris, France
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9
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Chromosome Segregation and Peptidoglycan Remodeling Are Coordinated at a Highly Stabilized Septal Pore to Maintain Bacterial Spore Development. Dev Cell 2020; 56:36-51.e5. [PMID: 33383000 DOI: 10.1016/j.devcel.2020.12.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/21/2020] [Accepted: 12/07/2020] [Indexed: 11/23/2022]
Abstract
Asymmetric division, a hallmark of endospore development, generates two cells, a larger mother cell and a smaller forespore. Approximately 75% of the forespore chromosome must be translocated across the division septum into the forespore by the DNA translocase SpoIIIE. Asymmetric division also triggers cell-specific transcription, which initiates septal peptidoglycan remodeling involving synthetic and hydrolytic enzymes. How these processes are coordinated has remained a mystery. Using Bacillus subtilis, we identified factors that revealed the link between chromosome translocation and peptidoglycan remodeling. In cells lacking these factors, the asymmetric septum retracts, resulting in forespore cytoplasmic leakage and loss of DNA translocation. Importantly, these phenotypes depend on septal peptidoglycan hydrolysis. Our data support a model in which SpoIIIE is anchored at the edge of a septal pore, stabilized by newly synthesized peptidoglycan and protein-protein interactions across the septum. Together, these factors ensure coordination between chromosome translocation and septal peptidoglycan remodeling to maintain spore development.
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10
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Gabale U, Peña Palomino PA, Kim H, Chen W, Ressl S. The essential inner membrane protein YejM is a metalloenzyme. Sci Rep 2020; 10:17794. [PMID: 33082366 PMCID: PMC7576196 DOI: 10.1038/s41598-020-73660-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 09/18/2020] [Indexed: 12/27/2022] Open
Abstract
Recent recurrent outbreaks of Gram-negative bacteria show the critical need to target essential bacterial mechanisms to fight the increase of antibiotic resistance. Pathogenic Gram-negative bacteria have developed several strategies to protect themselves against the host immune response and antibiotics. One such strategy is to remodel the outer membrane where several genes are involved. yejM was discovered as an essential gene in E. coli and S. typhimurium that plays a critical role in their virulence by changing the outer membrane permeability. How the inner membrane protein YejM with its periplasmic domain changes membrane properties remains unknown. Despite overwhelming structural similarity between the periplasmic domains of two YejM homologues with hydrolases like arylsulfatases, no enzymatic activity has been previously reported for YejM. Our studies reveal an intact active site with bound metal ions in the structure of YejM periplasmic domain. Furthermore, we show that YejM has a phosphatase activity that is dependent on the presence of magnesium ions and is linked to its function of regulating outer membrane properties. Understanding the molecular mechanism by which YejM is involved in outer membrane remodeling will help to identify a new drug target in the fight against the increased antibiotic resistance.
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Affiliation(s)
- Uma Gabale
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA.
| | - Perla Arianna Peña Palomino
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA
| | - HyunAh Kim
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA
| | - Wenya Chen
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA
| | - Susanne Ressl
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S Hawthrone Dr, Bloomington, IN, 47405, USA.
- Department of Neuroscience, The University of Texas At Austin, 100 E. 24th St., NHB 2.504, Austin, TX, 78712, USA.
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Khanna K, Lopez-Garrido J, Pogliano K. Shaping an Endospore: Architectural Transformations During Bacillus subtilis Sporulation. Annu Rev Microbiol 2020; 74:361-386. [PMID: 32660383 PMCID: PMC7610358 DOI: 10.1146/annurev-micro-022520-074650] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Endospore formation in Bacillus subtilis provides an ideal model system for studying development in bacteria. Sporulation studies have contributed a wealth of information about the mechanisms of cell-specific gene expression, chromosome dynamics, protein localization, and membrane remodeling, while helping to dispel the early view that bacteria lack internal organization and interesting cell biological phenomena. In this review, we focus on the architectural transformations that lead to a profound reorganization of the cellular landscape during sporulation, from two cells that lie side by side to the endospore, the unique cell within a cell structure that is a hallmark of sporulation in B. subtilis and other spore-forming Firmicutes. We discuss new insights into the mechanisms that drive morphogenesis, with special emphasis on polar septation, chromosome translocation, and the phagocytosis-like process of engulfment, and also the key experimental advances that have proven valuable in revealing the inner workings of bacterial cells.
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Affiliation(s)
- Kanika Khanna
- Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA; ,
| | | | - Kit Pogliano
- Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA; ,
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12
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Royes J, Biou V, Dautin N, Tribet C, Miroux B. Inducible intracellular membranes: molecular aspects and emerging applications. Microb Cell Fact 2020; 19:176. [PMID: 32887610 PMCID: PMC7650269 DOI: 10.1186/s12934-020-01433-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 08/27/2020] [Indexed: 02/08/2023] Open
Abstract
Membrane remodeling and phospholipid biosynthesis are normally tightly regulated to maintain the shape and function of cells. Indeed, different physiological mechanisms ensure a precise coordination between de novo phospholipid biosynthesis and modulation of membrane morphology. Interestingly, the overproduction of certain membrane proteins hijack these regulation networks, leading to the formation of impressive intracellular membrane structures in both prokaryotic and eukaryotic cells. The proteins triggering an abnormal accumulation of membrane structures inside the cells (or membrane proliferation) share two major common features: (1) they promote the formation of highly curved membrane domains and (2) they lead to an enrichment in anionic, cone-shaped phospholipids (cardiolipin or phosphatidic acid) in the newly formed membranes. Taking into account the available examples of membrane proliferation upon protein overproduction, together with the latest biochemical, biophysical and structural data, we explore the relationship between protein synthesis and membrane biogenesis. We propose a mechanism for the formation of these non-physiological intracellular membranes that shares similarities with natural inner membrane structures found in α-proteobacteria, mitochondria and some viruses-infected cells, pointing towards a conserved feature through evolution. We hope that the information discussed in this review will give a better grasp of the biophysical mechanisms behind physiological and induced intracellular membrane proliferation, and inspire new applications, either for academia (high-yield membrane protein production and nanovesicle production) or industry (biofuel production and vaccine preparation).
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Affiliation(s)
- Jorge Royes
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Université de Paris, LBPC-PM, CNRS, UMR7099, 75005, Paris, France. .,Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild pour le Développement de la Recherche Scientifique, 75005, Paris, France. .,Département de Chimie, École Normale Supérieure, PASTEUR, PSL University, CNRS, Sorbonne Université, 24 Rue Lhomond, 75005, Paris, France.
| | - Valérie Biou
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Université de Paris, LBPC-PM, CNRS, UMR7099, 75005, Paris, France.,Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild pour le Développement de la Recherche Scientifique, 75005, Paris, France
| | - Nathalie Dautin
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Université de Paris, LBPC-PM, CNRS, UMR7099, 75005, Paris, France.,Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild pour le Développement de la Recherche Scientifique, 75005, Paris, France
| | - Christophe Tribet
- Département de Chimie, École Normale Supérieure, PASTEUR, PSL University, CNRS, Sorbonne Université, 24 Rue Lhomond, 75005, Paris, France
| | - Bruno Miroux
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Université de Paris, LBPC-PM, CNRS, UMR7099, 75005, Paris, France. .,Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild pour le Développement de la Recherche Scientifique, 75005, Paris, France.
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13
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Ramos-Silva P, Serrano M, Henriques AO. From Root to Tips: Sporulation Evolution and Specialization in Bacillus subtilis and the Intestinal Pathogen Clostridioides difficile. Mol Biol Evol 2020; 36:2714-2736. [PMID: 31350897 PMCID: PMC6878958 DOI: 10.1093/molbev/msz175] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Bacteria of the Firmicutes phylum are able to enter a developmental pathway that culminates with the formation of highly resistant, dormant endospores. Endospores allow environmental persistence, dissemination and for pathogens, are also infection vehicles. In both the model Bacillus subtilis, an aerobic organism, and in the intestinal pathogen Clostridioides difficile, an obligate anaerobe, sporulation mobilizes hundreds of genes. Their expression is coordinated between the forespore and the mother cell, the two cells that participate in the process, and is kept in close register with the course of morphogenesis. The evolutionary mechanisms by which sporulation emerged and evolved in these two species, and more broadly across Firmicutes, remain largely unknown. Here, we trace the origin and evolution of sporulation using the genes known to be involved in the process in B. subtilis and C. difficile, and estimating their gain-loss dynamics in a comprehensive bacterial macroevolutionary framework. We show that sporulation evolution was driven by two major gene gain events, the first at the base of the Firmicutes and the second at the base of the B. subtilis group and within the Peptostreptococcaceae family, which includes C. difficile. We also show that early and late sporulation regulons have been coevolving and that sporulation genes entail greater innovation in B. subtilis with many Bacilli lineage-restricted genes. In contrast, C. difficile more often recruits new sporulation genes by horizontal gene transfer, which reflects both its highly mobile genome, the complexity of the gut microbiota, and an adjustment of sporulation to the gut ecosystem.
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Affiliation(s)
- Paula Ramos-Silva
- Instituto Gulbenkian de Ciência, Oeiras, Portugal.,Marine Biodiversity Group, Naturalis Biodiversity Center, Leiden, The Netherlands
| | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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14
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Zhukovsky MA, Filograna A, Luini A, Corda D, Valente C. Protein Amphipathic Helix Insertion: A Mechanism to Induce Membrane Fission. Front Cell Dev Biol 2019; 7:291. [PMID: 31921835 PMCID: PMC6914677 DOI: 10.3389/fcell.2019.00291] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 11/06/2019] [Indexed: 12/19/2022] Open
Abstract
One of the fundamental features of biomembranes is the ability to fuse or to separate. These processes called respectively membrane fusion and fission are central in the homeostasis of events such as those related to intracellular membrane traffic. Proteins that contain amphipathic helices (AHs) were suggested to mediate membrane fission via shallow insertion of these helices into the lipid bilayer. Here we analyze the AH-containing proteins that have been identified as essential for membrane fission and categorize them in few subfamilies, including small GTPases, Atg proteins, and proteins containing either the ENTH/ANTH- or the BAR-domain. AH-containing fission-inducing proteins may require cofactors such as additional proteins (e.g., lipid-modifying enzymes), or lipids (e.g., phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], phosphatidic acid [PA], or cardiolipin). Both PA and cardiolipin possess a cone shape and a negative charge (-2) that favor the recruitment of the AHs of fission-inducing proteins. Instead, PtdIns(4,5)P2 is characterized by an high negative charge able to recruit basic residues of the AHs of fission-inducing proteins. Here we propose that the AHs of fission-inducing proteins contain sequence motifs that bind lipid cofactors; accordingly (K/R/H)(K/R/H)xx(K/R/H) is a PtdIns(4,5)P2-binding motif, (K/R)x6(F/Y) is a cardiolipin-binding motif, whereas KxK is a PA-binding motif. Following our analysis, we show that the AHs of many fission-inducing proteins possess five properties: (a) at least three basic residues on the hydrophilic side, (b) ability to oligomerize, (c) optimal (shallow) depth of insertion into the membrane, (d) positive cooperativity in membrane curvature generation, and (e) specific interaction with one of the lipids mentioned above. These lipid cofactors favor correct conformation, oligomeric state and optimal insertion depth. The most abundant lipid in a given organelle possessing high negative charge (more negative than -1) is usually the lipid cofactor in the fission event. Interestingly, naturally occurring mutations have been reported in AH-containing fission-inducing proteins and related to diseases such as centronuclear myopathy (amphiphysin 2), Charcot-Marie-Tooth disease (GDAP1), Parkinson's disease (α-synuclein). These findings add to the interest of the membrane fission process whose complete understanding will be instrumental for the elucidation of the pathogenesis of diseases involving mutations in the protein AHs.
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Affiliation(s)
- Mikhail A. Zhukovsky
- Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| | | | | | - Daniela Corda
- Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| | - Carmen Valente
- Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
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15
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Ribis JW, Fimlaid KA, Shen A. Differential requirements for conserved peptidoglycan remodeling enzymes during Clostridioides difficile spore formation. Mol Microbiol 2019; 110:370-389. [PMID: 30066347 DOI: 10.1111/mmi.14090] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2018] [Indexed: 12/24/2022]
Abstract
Spore formation is essential for the bacterial pathogen and obligate anaerobe, Clostridioides (Clostridium) difficile, to transmit disease. Completion of this process depends on the mother cell engulfing the developing forespore, but little is known about how engulfment occurs in C. difficile. In Bacillus subtilis, engulfment is mediated by a peptidoglycan degradation complex consisting of SpoIID, SpoIIP and SpoIIM, which are all individually required for spore formation. Using genetic analyses, we determined the functions of these engulfment-related proteins along with the putative endopeptidase, SpoIIQ, during C. difficile sporulation. While SpoIID, SpoIIP and SpoIIQ were critical for engulfment, loss of SpoIIM minimally impacted C. difficile spore formation. Interestingly, a small percentage of ∆spoIID and ∆spoIIQ cells generated heat-resistant spores through the actions of SpoIIQ and SpoIID, respectively. Loss of SpoIID and SpoIIQ also led to unique morphological phenotypes: asymmetric engulfment and forespore distortions, respectively. Catalytic mutant complementation analyses revealed that these phenotypes depend on the enzymatic activities of SpoIIP and SpoIID, respectively. Lastly, engulfment mutants mislocalized polymerized coat even though the basement layer coat proteins, SpoIVA and SipL, remained associated with the forespore. Collectively, these findings advance our understanding of several stages during infectious C. difficile spore assembly.
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Affiliation(s)
- John W Ribis
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.,Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT, USA
| | - Kelly A Fimlaid
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT, USA
| | - Aimee Shen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.,Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT, USA
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16
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Ramírez-Guadiana FH, Rodrigues CDA, Marquis KA, Campo N, Barajas-Ornelas RDC, Brock K, Marks DS, Kruse AC, Rudner DZ. Evidence that regulation of intramembrane proteolysis is mediated by substrate gating during sporulation in Bacillus subtilis. PLoS Genet 2018; 14:e1007753. [PMID: 30403663 PMCID: PMC6242693 DOI: 10.1371/journal.pgen.1007753] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 11/19/2018] [Accepted: 10/10/2018] [Indexed: 01/11/2023] Open
Abstract
During the morphological process of sporulation in Bacillus subtilis two adjacent daughter cells (called the mother cell and forespore) follow different programs of gene expression that are linked to each other by signal transduction pathways. At a late stage in development, a signaling pathway emanating from the forespore triggers the proteolytic activation of the mother cell transcription factor σK. Cleavage of pro-σK to its mature and active form is catalyzed by the intramembrane cleaving metalloprotease SpoIVFB (B), a Site-2 Protease (S2P) family member. B is held inactive by two mother-cell membrane proteins SpoIVFA (A) and BofA. Activation of pro-σK processing requires a site-1 signaling protease SpoIVB (IVB) that is secreted from the forespore into the space between the two cells. IVB cleaves the extracellular domain of A but how this cleavage activates intramembrane proteolysis has remained unclear. Structural studies of the Methanocaldococcus jannaschii S2P homolog identified closed (substrate-occluded) and open (substrate-accessible) conformations of the protease, but the biological relevance of these conformations has not been established. Here, using co-immunoprecipitation and fluorescence microscopy, we show that stable association between the membrane-embedded protease and its substrate requires IVB signaling. We further show that the cytoplasmic cystathionine-β-synthase (CBS) domain of the B protease is not critical for this interaction or for pro-σK processing, suggesting the IVB-dependent interaction site is in the membrane protease domain. Finally, we provide evidence that the B protease domain adopts both open and closed conformations in vivo. Collectively, our data support a substrate-gating model in which IVB-dependent cleavage of A on one side of the membrane triggers a conformational change in the membrane-embedded protease from a closed to an open state allowing pro-σK access to the caged interior of the protease. Regulated Intramembrane Proteolysis is a broadly conserved mechanism for transducing information across lipid bilayers. In these signaling pathways a protease on one side of the membrane triggers the activation of a membrane-embedded protease that cleaves its substrate within or adjacent to the cytoplasmic face of the membrane. Site-2 metalloproteases (S2P) are the most commonly used intramembrane cleaving proteases in these pathways but the mechanism by which cleavage on one side of the membrane triggers intramembrane proteolysis remains poorly understood. Here, we provide evidence for a substrate-gating model in which an extracellular signaling protease triggers a conformational change in a S2P family member from a closed to an open conformation allowing its substrate access to the catalytic center of the enzyme.
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Affiliation(s)
| | | | - Kathleen A. Marquis
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston MA United States of America
| | - Nathalie Campo
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston MA United States of America
| | | | - Kelly Brock
- Department of Systems Biology, Harvard Medical School, Boston, MA
| | - Debora S. Marks
- Department of Systems Biology, Harvard Medical School, Boston, MA
| | - Andrew C. Kruse
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA
| | - David Z. Rudner
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston MA United States of America
- * E-mail:
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Tanaka M, Suwatthanarak T, Arakaki A, Johnson BRG, Evans SD, Okochi M, Staniland SS, Matsunaga T. Enhanced Tubulation of Liposome Containing Cardiolipin by MamY Protein from Magnetotactic Bacteria. Biotechnol J 2018; 13:e1800087. [DOI: 10.1002/biot.201800087] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/18/2018] [Indexed: 01/22/2023]
Affiliation(s)
- Masayoshi Tanaka
- Department of Chemical Science and EngineeringTokyo Institute of Technology2‐12‐1, O‐okayama, Meguro‐kuTokyo 152‐8552Japan
| | - Thanawat Suwatthanarak
- Department of Chemical Science and EngineeringTokyo Institute of Technology2‐12‐1, O‐okayama, Meguro‐kuTokyo 152‐8552Japan
| | - Atsushi Arakaki
- Division of Biotechnology and Life ScienceInstitute of EngineeringTokyo University of Agriculture and Technology2‐24‐16 Naka‐cho, KoganeiTokyo 184‐8588Japan
| | | | - Stephen D. Evans
- School of Physics and AstronomyUniversity of LeedsLeeds LS2 9JTUK
| | - Mina Okochi
- Department of Chemical Science and EngineeringTokyo Institute of Technology2‐12‐1, O‐okayama, Meguro‐kuTokyo 152‐8552Japan
| | | | - Tadashi Matsunaga
- Division of Biotechnology and Life ScienceInstitute of EngineeringTokyo University of Agriculture and Technology2‐24‐16 Naka‐cho, KoganeiTokyo 184‐8588Japan
- Faculty of Science and EngineeringWaseda University3‐4‐1, Okubo, Shinjuku‐kuTokyo 169‐8555Japan
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18
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The New Kid on the Block: A Specialized Secretion System during Bacterial Sporulation. Trends Microbiol 2018; 26:663-676. [DOI: 10.1016/j.tim.2018.01.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 01/03/2018] [Accepted: 01/09/2018] [Indexed: 01/09/2023]
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19
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Yap LW, Endres RG. A model of cell-wall dynamics during sporulation in Bacillus subtilis. SOFT MATTER 2017; 13:8089-8095. [PMID: 29057401 DOI: 10.1039/c7sm00818j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
To survive starvation, Bacillus subtilis forms durable spores. After asymmetric cell division, the septum grows around the forespore in a process called engulfment, but the mechanism of force generation is unknown. Here, we derived a novel biophysical model for the dynamics of cell-wall remodeling during engulfment based on a balancing of dissipative, active, and mechanical forces. By plotting phase diagrams, we predict that sporulation is promoted by a line tension from the attachment of the septum to the outer cell wall, as well as by an imbalance in turgor pressures in the mother-cell and forespore compartments. We also predict that significant mother-cell growth hinders engulfment. Hence, relatively simple physical principles may guide this complex biological process.
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Affiliation(s)
- Li-Wei Yap
- Department of Life Sciences, Imperial College, London, UK.
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20
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Ramírez-Guadiana FH, Meeske AJ, Rodrigues CDA, Barajas-Ornelas RDC, Kruse AC, Rudner DZ. A two-step transport pathway allows the mother cell to nurture the developing spore in Bacillus subtilis. PLoS Genet 2017; 13:e1007015. [PMID: 28945739 PMCID: PMC5629000 DOI: 10.1371/journal.pgen.1007015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 10/05/2017] [Accepted: 09/09/2017] [Indexed: 11/18/2022] Open
Abstract
One of the hallmarks of bacterial endospore formation is the accumulation of high concentrations of pyridine-2,6-dicarboxylic acid (dipicolinic acid or DPA) in the developing spore. This small molecule comprises 5–15% of the dry weight of dormant spores and plays a central role in resistance to both wet heat and desiccation. DPA is synthesized in the mother cell at a late stage in sporulation and must be translocated across two membranes (the inner and outer forespore membranes) that separate the mother cell and forespore. The enzymes that synthesize DPA and the proteins required to translocate it across the inner forespore membrane were identified over two decades ago but the factors that transport DPA across the outer forespore membrane have remained mysterious. Here, we report that SpoVV (formerly YlbJ) is the missing DPA transporter. SpoVV is produced in the mother cell during the morphological process of engulfment and specifically localizes in the outer forespore membrane. Sporulating cells lacking SpoVV produce spores with low levels of DPA and cells engineered to express SpoVV and the DPA synthase during vegetative growth accumulate high levels of DPA in the culture medium. SpoVV resembles concentrative nucleoside transporters and mutagenesis of residues predicted to form the substrate-binding pocket supports the idea that SpoVV has a similar structure and could therefore function similarly. These findings provide a simple two-step transport mechanism by which the mother cell nurtures the developing spore. DPA produced in the mother cell is first translocated into the intermembrane space by SpoVV and is then imported into the forespore by the SpoVA complex. This pathway is likely to be broadly conserved as DPA synthase, SpoVV, and SpoVA proteins can be found in virtually all endospore forming bacteria. All pathogenic and non-pathogenic bacteria that differentiate into dormant endospores including Clostridium difficile, Bacillus anthracis, and Bacillus subtilis, contain very high concentrations of the small molecule dipicolinic acid (DPA). This molecule displaces water in the spore core where it plays an integral role in spore resistance and dormancy. DPA and its contribution to spore dehydration were discovered in 1953 but the molecular basis for its accumulation in the spore has remained unclear. The developing endospore resides within a mother cell that assembles protective layers around the spore and nurtures it by providing mother-cell-produced molecules. DPA is produced in the mother cell at a late stage in development and then must be translocated across two membranes into the spore core. Here, we report the discovery of the missing DPA transporter, homologs of which are present in virtually all endospore-forming bacteria. Our data provide evidence for a simple two-step transport pathway in which the mother cell nurtures the developing spore by sequentially moving DPA across the two membranes that surround it.
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Affiliation(s)
| | - Alexander J. Meeske
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, United States of America
| | | | | | - Andrew C. Kruse
- Department of Biochemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, United States of America
| | - David Z. Rudner
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, United States of America
- * E-mail:
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21
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Dissection of membrane-binding and -remodeling regions in two classes of bacterial phospholipid N-methyltransferases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2279-2288. [PMID: 28912104 DOI: 10.1016/j.bbamem.2017.09.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 08/25/2017] [Accepted: 09/10/2017] [Indexed: 01/08/2023]
Abstract
Bacterial phospholipid N-methyltransferases (Pmts) catalyze the formation of phosphatidylcholine (PC) via successive N-methylation of phosphatidylethanolamine (PE). They are classified into Sinorhizobium-type and Rhodobacter-type enzymes. The Sinorhizobium-type PmtA protein from the plant pathogen Agrobacterium tumefaciens is recruited to anionic lipids in the cytoplasmic membrane via two amphipathic helices called αA and αF. Besides its enzymatic activity, PmtA is able to remodel membranes mediated by the αA domain. According to the Heliquest program, αA- and αF-like amphipathic helices are also present in other Sinorhizobium- and Rhodobacter-type Pmt enzymes suggesting a conserved architecture of α-helical membrane-binding regions in these methyltransferases. As representatives of the two Pmt families, we investigated the membrane binding and remodeling capacity of Bradyrhizobium japonicum PmtA (Sinorhizobium-type) and PmtX1 (Rhodobacter-type), which act cooperatively to produce PC in consecutive methylation steps. We found that the αA regions in both enzymes bind anionic lipids similar to αA of A. tumefaciens PmtA. Membrane binding of PmtX1 αA is enhanced by its substrate monomethyl-PE indicating a substrate-controlled membrane association. The αA regions of all investigated enzymes remodel spherical liposomes into tubular filaments suggesting a conserved membrane-remodeling capacity of bacterial Pmts. Based on these results we propose that the molecular details of membrane-binding and remodeling are conserved among bacterial Pmts.
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22
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Carranza G, Angius F, Ilioaia O, Solgadi A, Miroux B, Arechaga I. Cardiolipin plays an essential role in the formation of intracellular membranes in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1124-1132. [PMID: 28284722 DOI: 10.1016/j.bbamem.2017.03.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/22/2017] [Accepted: 03/07/2017] [Indexed: 02/07/2023]
Abstract
Mitochondria, chloroplasts and photosynthetic bacteria are characterized by the presence of complex and intricate membrane systems. In contrast, non-photosynthetic bacteria lack membrane structures within their cytoplasm. However, large scale over-production of some membrane proteins, such as the fumarate reductase, the mannitol permease MtlA, the glycerol acyl transferase PlsB, the chemotaxis receptor Tsr or the ATP synthase subunit b, can induce the proliferation of intra cellular membranes (ICMs) in the cytoplasm of Escherichia coli. These ICMs are particularly rich in cardiolipin (CL). Here, we have studied the effect of CL in the generation of these membranous structures. We have deleted the three genes (clsA, clsB and clsC) responsible of CL biosynthesis in E. coli and analysed the effect of these mutations by fluorescent and electron microscopy and by lipid mass spectrometry. We have found that CL is essential in the formation of non-lamellar structures in the cytoplasm of E. coli cells. These results could help to understand the structuration of membranes in E. coli and other membrane organelles, such as mitochondria and ER.
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Affiliation(s)
- Gerardo Carranza
- Departamento de Biología Molecular and Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria - CSIC - SODERCAN, Santander, Spain
| | - Federica Angius
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Institut de Biologie Physico-Chimique, CNRS, Univ Paris Diderot, Sorbonne Paris Cité, PSL Research University, Paris, France
| | - Oana Ilioaia
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Institut de Biologie Physico-Chimique, CNRS, Univ Paris Diderot, Sorbonne Paris Cité, PSL Research University, Paris, France
| | - Audrey Solgadi
- Université Paris-Saclay, Institut Paris Saclay d'Innovation Thérapeutique, INSERM, CNRS, - Plateforme SAMM - CHATENAY-MALABRY, France
| | - Bruno Miroux
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Institut de Biologie Physico-Chimique, CNRS, Univ Paris Diderot, Sorbonne Paris Cité, PSL Research University, Paris, France.
| | - Ignacio Arechaga
- Departamento de Biología Molecular and Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria - CSIC - SODERCAN, Santander, Spain.
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Abstract
Membrane deformation by proteins is a universal phenomenon that has been studied extensively in eukaryotes but much less in prokaryotes. In this study, we discovered a membrane-deforming activity of the phospholipid N-methyltransferase PmtA from the plant-pathogenic bacterium Agrobacterium tumefaciens PmtA catalyzes the successive three-step N-methylation of phosphatidylethanolamine to phosphatidylcholine. Here, we defined the lipid and protein requirements for the membrane-remodeling activity of PmtA by a combination of transmission electron microscopy and liposome interaction studies. Dependent on the lipid composition, PmtA changes the shape of spherical liposomes either into filaments or small vesicles. Upon overproduction of PmtA in A. tumefaciens, vesicle-like structures occur in the cytoplasm, dependent on the presence of the anionic lipid cardiolipin. The N-terminal lipid-binding α-helix (αA) is involved in membrane deformation by PmtA. Two functionally distinct and spatially separated regions in αA can be distinguished. Anionic interactions by positively charged amino acids on one face of the helix are responsible for membrane recruitment of the enzyme. The opposite hydrophobic face of the helix is required for membrane remodeling, presumably by shallow insertion into the lipid bilayer.IMPORTANCE The ability to alter the morphology of biological membranes is known for a small number of some bacterial proteins. Our study adds the phospholipid N-methyltransferase PmtA as a new member to the category of bacterial membrane-remodeling proteins. A combination of in vivo and in vitro methods reveals the molecular requirements for membrane deformation at the protein and phospholipid level. The dual functionality of PmtA suggests a contribution of membrane biosynthesis enzymes to the complex morphology of bacterial membranes.
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Xu J, Gui M, Wang D, Xiang Y. The bacteriophage ϕ29 tail possesses a pore-forming loop for cell membrane penetration. Nature 2016; 534:544-7. [PMID: 27309813 DOI: 10.1038/nature18017] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 04/14/2016] [Indexed: 12/29/2022]
Abstract
Most bacteriophages are tailed bacteriophages with an isometric or a prolate head attached to a long contractile, long non-contractile, or short non-contractile tail. The tail is a complex machine that plays a central role in host cell recognition and attachment, cell wall and membrane penetration, and viral genome ejection. The mechanisms involved in the penetration of the inner host cell membrane by bacteriophage tails are not well understood. Here we describe structural and functional studies of the bacteriophage ϕ29 tail knob protein gene product 9 (gp9). The 2.0 Å crystal structure of gp9 shows that six gp9 molecules form a hexameric tube structure with six flexible hydrophobic loops blocking one end of the tube before DNA ejection. Sequence and structural analyses suggest that the loops in the tube could be membrane active. Further biochemical assays and electron microscopy structural analyses show that the six hydrophobic loops in the tube exit upon DNA ejection and form a channel that spans the lipid bilayer of the membrane and allows the release of the bacteriophage genomic DNA, suggesting that cell membrane penetration involves a pore-forming mechanism similar to that of certain non-enveloped eukaryotic viruses. A search of other phage tail proteins identified similar hydrophobic loops, which indicates that a common mechanism might be used for membrane penetration by prokaryotic viruses. These findings suggest that although prokaryotic and eukaryotic viruses use apparently very different mechanisms for infection, they have evolved similar mechanisms for breaching the cell membrane.
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Affiliation(s)
- Jingwei Xu
- Centre for Infectious Diseases Research, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Beijing Advanced Innovation Center for Structural Biology, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Miao Gui
- Centre for Infectious Diseases Research, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Beijing Advanced Innovation Center for Structural Biology, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Dianhong Wang
- Centre for Infectious Diseases Research, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Beijing Advanced Innovation Center for Structural Biology, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Ye Xiang
- Centre for Infectious Diseases Research, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Beijing Advanced Innovation Center for Structural Biology, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
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25
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Bohuszewicz O, Liu J, Low HH. Membrane remodelling in bacteria. J Struct Biol 2016; 196:3-14. [PMID: 27265614 DOI: 10.1016/j.jsb.2016.05.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 05/20/2016] [Accepted: 05/26/2016] [Indexed: 01/10/2023]
Abstract
In bacteria the ability to remodel membrane underpins basic cell processes such as growth, and more sophisticated adaptations like inter-cell crosstalk, organelle specialisation, and pathogenesis. Here, selected examples of membrane remodelling in bacteria are presented and the diverse mechanisms for inducing membrane fission, fusion, and curvature discussed. Compared to eukaryotes, relatively few curvature-inducing proteins have been characterised so far. Whilst it is likely that many such proteins remain to be discovered, it also reflects the importance of alternative membrane remodelling strategies in bacteria where passive mechanisms for generating curvature are utilised.
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Affiliation(s)
- Olga Bohuszewicz
- Department of Life Sciences, Imperial College, London SW7 2AZ, UK
| | - Jiwei Liu
- Department of Life Sciences, Imperial College, London SW7 2AZ, UK
| | - Harry H Low
- Department of Life Sciences, Imperial College, London SW7 2AZ, UK.
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Bose B, Reed SE, Besprozvannaya M, Burton BM. Missense Mutations Allow a Sequence-Blind Mutant of SpoIIIE to Successfully Translocate Chromosomes during Sporulation. PLoS One 2016; 11:e0148365. [PMID: 26849443 PMCID: PMC4744071 DOI: 10.1371/journal.pone.0148365] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 01/19/2016] [Indexed: 11/18/2022] Open
Abstract
SpoIIIE directionally pumps DNA across membranes during Bacillus subtilis sporulation and vegetative growth. The sequence-reading domain (γ domain) is required for directional DNA transport, and its deletion severely impairs sporulation. We selected suppressors of the spoIIIEΔγ sporulation defect. Unexpectedly, many suppressors were intragenic missense mutants, and some restore sporulation to near-wild-type levels. The mutant proteins are likely not more abundant, faster at translocating DNA, or sequence-sensitive, and rescue does not involve the SpoIIIE homolog SftA. Some mutants behave differently when co-expressed with spoIIIEΔγ, consistent with the idea that some, but not all, variants may form mixed oligomers. In full-length spoIIIE, these mutations do not affect sporulation, and yet the corresponding residues are rarely found in other SpoIIIE/FtsK family members. The suppressors do not rescue chromosome translocation defects during vegetative growth, indicating that the role of the γ domain cannot be fully replaced by these mutations. We present two models consistent with our findings: that the suppressors commit to transport in one arbitrarily-determined direction or delay spore development. It is surprising that missense mutations somehow rescue loss of an entire domain with a complex function, and this raises new questions about the mechanism by which SpoIIIE pumps DNA and the roles SpoIIIE plays in vivo.
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Affiliation(s)
- Baundauna Bose
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Sydney E. Reed
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Marina Besprozvannaya
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Briana M. Burton
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
- * E-mail:
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Widderich N, Rodrigues CDA, Commichau FM, Fischer KE, Ramirez-Guadiana FH, Rudner DZ, Bremer E. Salt-sensitivity of σ(H) and Spo0A prevents sporulation of Bacillus subtilis at high osmolarity avoiding death during cellular differentiation. Mol Microbiol 2016; 100:108-24. [PMID: 26712348 DOI: 10.1111/mmi.13304] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2015] [Indexed: 01/15/2023]
Abstract
The spore-forming bacterium Bacillus subtilis frequently experiences high osmolarity as a result of desiccation in the soil. The formation of a highly desiccation-resistant endospore might serve as a logical osmostress escape route when vegetative growth is no longer possible. However, sporulation efficiency drastically decreases concomitant with an increase in the external salinity. Fluorescence microscopy of sporulation-specific promoter fusions to gfp revealed that high salinity blocks entry into the sporulation pathway at a very early stage. Specifically, we show that both Spo0A- and SigH-dependent transcription are impaired. Furthermore, we demonstrate that the association of SigH with core RNA polymerase is reduced under these conditions. Suppressors that modestly increase sporulation efficiency at high salinity map to the coding region of sigH and in the regulatory region of kinA, encoding one the sensor kinases that activates Spo0A. These findings led us to discover that B. subtilis cells that overproduce KinA can bypass the salt-imposed block in sporulation. Importantly, these cells are impaired in the morphological process of engulfment and late forespore gene expression and frequently undergo lysis. Altogether our data indicate that B. subtilis blocks entry into sporulation in high-salinity environments preventing commitment to a developmental program that it cannot complete.
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Affiliation(s)
- Nils Widderich
- Department of Biology, Laboratory for Molecular Microbiology, Philipps-University Marburg, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany
| | - Christopher D A Rodrigues
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115-5701, USA
| | - Fabian M Commichau
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg August University Göttingen, Griesebachstr, 8, D-37077, Göttingen, Germany
| | - Kathleen E Fischer
- Department of Biology, Laboratory for Molecular Microbiology, Philipps-University Marburg, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany
| | - Fernando H Ramirez-Guadiana
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115-5701, USA
| | - David Z Rudner
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115-5701, USA
| | - Erhard Bremer
- Department of Biology, Laboratory for Molecular Microbiology, Philipps-University Marburg, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany
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Meeske AJ, Rodrigues CDA, Brady J, Lim HC, Bernhardt TG, Rudner DZ. High-Throughput Genetic Screens Identify a Large and Diverse Collection of New Sporulation Genes in Bacillus subtilis. PLoS Biol 2016; 14:e1002341. [PMID: 26735940 PMCID: PMC4703394 DOI: 10.1371/journal.pbio.1002341] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 11/25/2015] [Indexed: 01/09/2023] Open
Abstract
The differentiation of the bacterium Bacillus subtilis into a dormant spore is among the most well-characterized developmental pathways in biology. Classical genetic screens performed over the past half century identified scores of factors involved in every step of this morphological process. More recently, transcriptional profiling uncovered additional sporulation-induced genes required for successful spore development. Here, we used transposon-sequencing (Tn-seq) to assess whether there were any sporulation genes left to be discovered. Our screen identified 133 out of the 148 genes with known sporulation defects. Surprisingly, we discovered 24 additional genes that had not been previously implicated in spore formation. To investigate their functions, we used fluorescence microscopy to survey early, middle, and late stages of differentiation of null mutants from the B. subtilis ordered knockout collection. This analysis identified mutants that are delayed in the initiation of sporulation, defective in membrane remodeling, and impaired in spore maturation. Several mutants had novel sporulation phenotypes. We performed in-depth characterization of two new factors that participate in cell–cell signaling pathways during sporulation. One (SpoIIT) functions in the activation of σE in the mother cell; the other (SpoIIIL) is required for σG activity in the forespore. Our analysis also revealed that as many as 36 sporulation-induced genes with no previously reported mutant phenotypes are required for timely spore maturation. Finally, we discovered a large set of transposon insertions that trigger premature initiation of sporulation. Our results highlight the power of Tn-seq for the discovery of new genes and novel pathways in sporulation and, combined with the recently completed null mutant collection, open the door for similar screens in other, less well-characterized processes. Transposon sequencing enables the recovery of virtually all previously characterized genes required for the differentiation of the bacterium Bacillus subtilis into a dormant spore and identifies 24 new ones. When starved of nutrients, the bacterium Bacillus subtilis differentiates into a dormant spore that is impervious to environmental insults. Decades of research have uncovered over 100 genes required for spore formation. Molecular dissection of these genes has revealed factors that act at every stage of this developmental process. In this study, we used a high-throughput genetic screening method called transposon sequencing to assess whether there were any sporulation genes left to be discovered. This approach identified virtually all of the known sporulation genes, as well as 24 new ones. Furthermore, transposon sequencing enabled the discovery of two new sets of mutants in which the sporulation process was either delayed or accelerated. Using fluorescence microscopy, we determined the developmental stage at which each mutant was impaired and discovered mutants that are delayed in initiation of sporulation, or defective in morphogenesis, cell–cell signaling, or spore maturation. Our findings exemplify the utility of transposon sequencing to uncover new biology in well-studied processes, suggesting that it could similarly be used to identify novel genes required for other aspects of bacterial physiology, such as natural competence, stationary phase survival, or the responses to cell envelope stress and DNA damage.
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Affiliation(s)
- Alexander J. Meeske
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Christopher D. A. Rodrigues
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jacqueline Brady
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Hoong Chuin Lim
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Thomas G. Bernhardt
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - David Z. Rudner
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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Dalebroux ZD, Edrozo MB, Pfuetzner RA, Ressl S, Kulasekara BR, Blanc MP, Miller SI. Delivery of cardiolipins to the Salmonella outer membrane is necessary for survival within host tissues and virulence. Cell Host Microbe 2016; 17:441-51. [PMID: 25856753 DOI: 10.1016/j.chom.2015.03.003] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 01/05/2015] [Accepted: 02/27/2015] [Indexed: 12/22/2022]
Abstract
The outer membrane (OM) of Gram-negative bacteria is an asymmetric lipid bilayer that serves as a barrier to the environment. During infection, Gram-negative bacteria remodel their OM to promote survival and replication within host tissues. Salmonella rely on the PhoPQ two-component regulators to coordinate OM remodeling in response to environmental cues. In a screen for mediators of PhoPQ-regulated OM remodeling in Salmonella Typhimurium, we identified PbgA, a periplasmic domain-containing transmembrane protein, which binds cardiolipin glycerophospholipids near the inner membrane and promotes their PhoPQ-regulated trafficking to the OM. Purified-PbgA oligomers are tetrameric, and the periplasmic domain contains a globular region that binds to the OM in a PhoPQ-dependent manner. Thus, PbgA forms a complex that may bridge the envelope for regulated cardiolipin delivery. PbgA globular region-deleted mutant bacteria are severely attenuated for pathogenesis, suggesting that increased cardiolipin trafficking to the OM is necessary for Salmonella to survive within host tissues that activate PhoPQ.
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Affiliation(s)
- Zachary D Dalebroux
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Mauna B Edrozo
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Richard A Pfuetzner
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Susanne Ressl
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, 212 S. Hawthrone Drive, Bloomington, IN 47401, USA
| | | | - Marie-Pierre Blanc
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Samuel I Miller
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA; Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA; Department of Medicine, University of Washington, Seattle, WA 98195, USA.
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Abstract
The Gram-positive bacterium Bacillus subtilis initiates the formation of an endospore in response to conditions of nutrient limitation. The morphological differentiation that spores undergo initiates with the formation of an asymmetric septum near to one pole of the cell, forming a smaller compartment, the forespore, and a larger compartment, the mother cell. This process continues with the complex morphogenesis of the spore as governed by an intricate series of interactions between forespore and mother cell proteins across the inner and outer forespore membranes. Given that these interactions occur at a particular place in the cell, a critical question is how the proteins involved in these processes get properly targeted, and we discuss recent progress in identifying mechanisms responsible for this targeting.
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Fimlaid KA, Jensen O, Donnelly ML, Siegrist MS, Shen A. Regulation of Clostridium difficile Spore Formation by the SpoIIQ and SpoIIIA Proteins. PLoS Genet 2015; 11:e1005562. [PMID: 26465937 PMCID: PMC4605598 DOI: 10.1371/journal.pgen.1005562] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 09/10/2015] [Indexed: 01/05/2023] Open
Abstract
Sporulation is an ancient developmental process that involves the formation of a highly resistant endospore within a larger mother cell. In the model organism Bacillus subtilis, sporulation-specific sigma factors activate compartment-specific transcriptional programs that drive spore morphogenesis. σG activity in the forespore depends on the formation of a secretion complex, known as the “feeding tube,” that bridges the mother cell and forespore and maintains forespore integrity. Even though these channel components are conserved in all spore formers, recent studies in the major nosocomial pathogen Clostridium difficile suggested that these components are dispensable for σG activity. In this study, we investigated the requirements of the SpoIIQ and SpoIIIA proteins during C. difficile sporulation. C. difficile spoIIQ, spoIIIA, and spoIIIAH mutants exhibited defects in engulfment, tethering of coat to the forespore, and heat-resistant spore formation, even though they activate σG at wildtype levels. Although the spoIIQ, spoIIIA, and spoIIIAH mutants were defective in engulfment, metabolic labeling studies revealed that they nevertheless actively transformed the peptidoglycan at the leading edge of engulfment. In vitro pull-down assays further demonstrated that C. difficile SpoIIQ directly interacts with SpoIIIAH. Interestingly, mutation of the conserved Walker A ATP binding motif, but not the Walker B ATP hydrolysis motif, disrupted SpoIIIAA function during C. difficile spore formation. This finding contrasts with B. subtilis, which requires both Walker A and B motifs for SpoIIIAA function. Taken together, our findings suggest that inhibiting SpoIIQ, SpoIIIAA, or SpoIIIAH function could prevent the formation of infectious C. difficile spores and thus disease transmission. The bacterial spore-forming pathogen Clostridium difficile is a leading cause of nosocomial infections in the United States and represents a significant threat to healthcare systems around the world. As an obligate anaerobe, C. difficile must form spores in order to survive exit from the gastrointestinal tract. Accordingly, spore formation is essential for C. difficile disease transmission. Since the mechanisms controlling this process remain poorly characterized, we analyzed the importance of highly conserved secretion channel components during C. difficile sporulation. In the model organism Bacillus subtilis, this channel had previously been shown to function as a “feeding tube” that allows the mother cell to nurture the developing forespore and sustain transcription in the forespore. We show here that conserved components of this structure in C. difficile are dispensable for forespore transcription, although they are important for completing forespore engulfment and retaining the protective spore coat around the forespore, in contrast with B. subtilis. The results of our study suggest that targeting these conserved proteins could prevent C. difficile spore formation and thus disease transmission.
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Affiliation(s)
- Kelly A. Fimlaid
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
- Program in Cellular, Molecular & Biomedical Sciences, University of Vermont, Burlington, Vermont, United States of America
| | - Owen Jensen
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - M. Lauren Donnelly
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - M. Sloan Siegrist
- Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America
| | - Aimee Shen
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
- * E-mail:
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Stepanyants N, Macdonald PJ, Francy CA, Mears JA, Qi X, Ramachandran R. Cardiolipin's propensity for phase transition and its reorganization by dynamin-related protein 1 form a basis for mitochondrial membrane fission. Mol Biol Cell 2015; 26:3104-16. [PMID: 26157169 PMCID: PMC4551322 DOI: 10.1091/mbc.e15-06-0330] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 07/01/2015] [Indexed: 01/01/2023] Open
Abstract
Fluid cardiolipin (CL) promotes self-assembly of Drp1, a dynamin-family GTPase involved in mitochondrial fission. Drp1 sequesters CL into condensed membrane platforms and in a GTP-dependent manner increases the propensity of the lipid to undergo a nonbilayer phase transition. CL reorganization generates local membrane constriction for fission. Cardiolipin (CL) is an atypical, dimeric phospholipid essential for mitochondrial dynamics in eukaryotic cells. Dynamin-related protein 1 (Drp1), a cytosolic member of the dynamin superfamily of large GTPases, interacts with CL and functions to sustain the balance of mitochondrial division and fusion by catalyzing mitochondrial fission. Although recent studies have indicated a role for CL in stimulating Drp1 self-assembly and GTPase activity at the membrane surface, the mechanism by which CL functions in membrane fission, if at all, remains unclear. Here, using a variety of fluorescence spectroscopic and imaging approaches together with model membranes, we demonstrate that Drp1 and CL function cooperatively in effecting membrane constriction toward fission in three distinct steps. These involve 1) the preferential association of Drp1 with CL localized at a high spatial density in the membrane bilayer, 2) the reorganization of unconstrained, fluid-phase CL molecules in concert with Drp1 self-assembly, and 3) the increased propensity of CL to transition from a lamellar, bilayer arrangement to an inverted hexagonal, nonbilayer configuration in the presence of Drp1 and GTP, resulting in the creation of localized membrane constrictions that are primed for fission. Thus we propose that Drp1 and CL function in concert to catalyze mitochondrial division.
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Affiliation(s)
- Natalia Stepanyants
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Patrick J Macdonald
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Christopher A Francy
- Center for Mitochondrial Diseases, Case Western Reserve University School of Medicine, Cleveland, OH 44106 Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106 Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Jason A Mears
- Center for Mitochondrial Diseases, Case Western Reserve University School of Medicine, Cleveland, OH 44106 Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106 Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Xin Qi
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106 Center for Mitochondrial Diseases, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Rajesh Ramachandran
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106 Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
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Fimlaid KA, Shen A. Diverse mechanisms regulate sporulation sigma factor activity in the Firmicutes. Curr Opin Microbiol 2015; 24:88-95. [PMID: 25646759 DOI: 10.1016/j.mib.2015.01.006] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 12/23/2014] [Accepted: 01/10/2015] [Indexed: 11/27/2022]
Abstract
Sporulation allows bacteria to survive adverse conditions and is essential to the lifecycle of some obligate anaerobes. In Bacillus subtilis, the sporulation-specific sigma factors, σ(F), σ(E), σ(G), and σ(K), activate compartment-specific transcriptional programs that drive sporulation through its morphological stages. The regulation of these sigma factors was predicted to be conserved across the Firmicutes, since the regulatory proteins controlling their activation are largely conserved. However, recent studies in (Pepto)Clostridium difficile, Clostridium acetobutylicum, Clostridium perfringens, and Clostridium botulinum have revealed striking differences in the order, activation, and function of sporulation sigma factors. These studies indicate that gene conservation does not necessarily predict gene function and that new mechanisms for controlling cell fate determination remain to be discovered in the anaerobic Clostridia.
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Affiliation(s)
- Kelly A Fimlaid
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA; Cellular, Molecular and Biomedical Sciences Program, University of Vermont, Burlington, VT 05405, USA
| | - Aimee Shen
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA.
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Ojkic N, López-Garrido J, Pogliano K, Endres RG. Bistable forespore engulfment in Bacillus subtilis by a zipper mechanism in absence of the cell wall. PLoS Comput Biol 2014; 10:e1003912. [PMID: 25356555 PMCID: PMC4214620 DOI: 10.1371/journal.pcbi.1003912] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 09/16/2014] [Indexed: 12/22/2022] Open
Abstract
To survive starvation, the bacterium Bacillus subtilis forms durable spores. The initial step of sporulation is asymmetric cell division, leading to a large mother-cell and a small forespore compartment. After division is completed and the dividing septum is thinned, the mother cell engulfs the forespore in a slow process based on cell-wall degradation and synthesis. However, recently a new cell-wall independent mechanism was shown to significantly contribute, which can even lead to fast engulfment in 60 of the cases when the cell wall is completely removed. In this backup mechanism, strong ligand-receptor binding between mother-cell protein SpoIIIAH and forespore-protein SpoIIQ leads to zipper-like engulfment, but quantitative understanding is missing. In our work, we combined fluorescence image analysis and stochastic Langevin simulations of the fluctuating membrane to investigate the origin of fast bistable engulfment in absence of the cell wall. Our cell morphologies compare favorably with experimental time-lapse microscopy, with engulfment sensitive to the number of SpoIIQ-SpoIIIAH bonds in a threshold-like manner. By systematic exploration of model parameters, we predict regions of osmotic pressure and membrane-surface tension that produce successful engulfment. Indeed, decreasing the medium osmolarity in experiments prevents engulfment in line with our predictions. Forespore engulfment may thus not only be an ideal model system to study decision-making in single cells, but its biophysical principles are likely applicable to engulfment in other cell types, e.g. during phagocytosis in eukaryotes. When the bacterium B. subtilis runs out of food, it undergoes a fundamental development process by which it forms durable spores. Sporulation is initiated by asymmetric cell division after which the larger mother cell engulfs the smaller forespore, followed by spore maturation and release. This survival strategy is so robust that engulfment even proceeds when cells are deprived of their protective cell wall. Under these severe perturbations, 60 of the mother cells still engulf their forespores in only 10 of the normal engulfment time, while the remaining 40 of mother cells withdraw from engulfment. This all-or-none outcome of engulfment suggests decision-making, which was recently also identified in other types of engulfment, e.g. during phagocytosis when immune cells engulf and destroy pathogens. Here, we developed a biophysical model to explain fast bistable forespore engulfment in absence of the cell wall and energy sources. Our discovered principles may prove very general, thus predicting key ingredients of successful engulfment across all kingdoms of life.
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Affiliation(s)
- Nikola Ojkic
- Department of Life Sciences, Imperial College, London, United Kingdom
- Centre for Integrative Systems Biology and Bioinformatics, Imperial College, London, United Kingdom
- * E-mail:
| | - Javier López-Garrido
- Division of Biological Sciences, University of California, San Diego, La Jolla, California, United States of America
| | - Kit Pogliano
- Division of Biological Sciences, University of California, San Diego, La Jolla, California, United States of America
| | - Robert G. Endres
- Department of Life Sciences, Imperial College, London, United Kingdom
- Centre for Integrative Systems Biology and Bioinformatics, Imperial College, London, United Kingdom
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Abstract
Cardiolipin (CL) is an anionic phospholipid with a characteristically large curvature and is of growing interest for two primary reasons: (i) it binds to and regulates many peripheral membrane proteins in bacteria and mitochondria, and (ii) it is distributed asymmetrically in rod-shaped cells and is concentrated at the poles and division septum. Despite the growing number of studies of CL, its function in bacteria remains unknown. 10-N-Nonyl acridine orange (NAO) is widely used to image CL in bacteria and mitochondria, as its interaction with CL is reported to produce a characteristic red-shifted fluorescence emission. Using a suite of biophysical techniques, we quantitatively studied the interaction of NAO with anionic phospholipids under physiologically relevant conditions. We found that NAO is promiscuous in its binding and has photophysical properties that are largely insensitive to the structure of diverse anionic phospholipids to which it binds. Being unable to rely solely on NAO to characterize the localization of CL in Escherichia coli cells, we instead used quantitative fluorescence microscopy, mass spectrometry, and mutants deficient in specific classes of anionic phospholipids. We found CL and phosphatidylglycerol (PG) concentrated in the polar regions of E. coli cell membranes; depletion of CL by genetic approaches increased the concentration of PG at the poles. Previous studies suggested that some CL-binding proteins also have a high affinity for PG and display a pattern of cellular localization that is not influenced by depletion of CL. Framed within the context of these previous experiments, our results suggest that PG may play an essential role in bacterial physiology by maintaining the anionic character of polar membranes.
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36
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Tan IS, Ramamurthi KS. Spore formation in Bacillus subtilis. ENVIRONMENTAL MICROBIOLOGY REPORTS 2014; 6:212-25. [PMID: 24983526 PMCID: PMC4078662 DOI: 10.1111/1758-2229.12130] [Citation(s) in RCA: 223] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 11/05/2013] [Accepted: 11/19/2013] [Indexed: 05/04/2023]
Abstract
Although prokaryotes ordinarily undergo binary fission to produce two identical daughter cells, some are able to undergo alternative developmental pathways that produce daughter cells of distinct cell morphology and fate. One such example is a developmental programme called sporulation in the bacterium Bacillus subtilis, which occurs under conditions of environmental stress. Sporulation has long been used as a model system to help elucidate basic processes of developmental biology including transcription regulation, intercellular signalling, membrane remodelling, protein localization and cell fate determination. This review highlights some of the recent work that has been done to further understand prokaryotic cell differentiation during sporulation and its potential applications.
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Affiliation(s)
- Irene S Tan
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA; NIH-Johns Hopkins University Graduate Partnerships Program, Baltimore, MD, 21218, USA
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PhoPQ regulates acidic glycerophospholipid content of the Salmonella Typhimurium outer membrane. Proc Natl Acad Sci U S A 2014; 111:1963-8. [PMID: 24449881 DOI: 10.1073/pnas.1316901111] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Gram-negative bacteria have two lipid membranes separated by a periplasmic space containing peptidoglycan. The surface bilayer, or outer membrane (OM), provides a barrier to toxic molecules, including host cationic antimicrobial peptides (CAMPs). The OM comprises an outer leaflet of lipid A, the bioactive component of lipopolysaccharide (LPS), and an inner leaflet of glycerophospholipids (GPLs). The structure of lipid A is environmentally regulated in a manner that can promote bacterial infection by increasing bacterial resistance to CAMP and reducing LPS recognition by the innate immune system. The gastrointestinal pathogen, Salmonella Typhimurium, responds to acidic pH and CAMP through the PhoPQ two-component regulatory system, which stimulates lipid A remodeling, CAMP resistance, and intracellular survival within acidified phagosomes. Work here demonstrates that, in addition to regulating lipid A structure, the S. Typhimurium PhoPQ virulence regulators also regulate acidic GPL by increasing the levels of cardiolipins and palmitoylated acylphosphatidylglycerols within the OM. Triacylated palmitoyl-PG species were diminished in strains deleted for the PhoPQ-regulated OM lipid A palmitoyltransferase enzyme, PagP. Purified PagP transferred palmitate to PG consistent with PagP acylation of both lipid A and PG within the OM. Therefore, PhoPQ coordinately regulates OM acidic GPL with lipid A structure, suggesting that GPLs cooperate with lipid A to form an OM barrier critical for CAMP resistance and intracellular survival of S. Typhimurium.
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38
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Cornejo E, Abreu N, Komeili A. Compartmentalization and organelle formation in bacteria. Curr Opin Cell Biol 2014; 26:132-8. [PMID: 24440431 DOI: 10.1016/j.ceb.2013.12.007] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 12/17/2013] [Accepted: 12/17/2013] [Indexed: 12/19/2022]
Abstract
A number of bacterial species rely on compartmentalization to gain specific functionalities that will provide them with a selective advantage. Here, we will highlight several of these modes of bacterial compartmentalization with an eye toward describing the mechanisms of their formation and their evolutionary origins. Spore formation in Bacillus subtilis, outer membrane biogenesis in Gram-negative bacteria and protein diffusion barriers of Caulobacter crescentus will be used to demonstrate the physical, chemical, and compositional remodeling events that lead to compartmentalization. In addition, magnetosomes and carboxysomes will serve as models to examine the interplay between cytoskeletal systems and the subcellular positioning of organelles.
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Affiliation(s)
- Elias Cornejo
- Department of Plant and Microbial Biology, University of California, Berkeley, 111 Koshland Hall, Berkeley, CA 94720-3102, United States
| | - Nicole Abreu
- Department of Plant and Microbial Biology, University of California, Berkeley, 111 Koshland Hall, Berkeley, CA 94720-3102, United States
| | - Arash Komeili
- Department of Plant and Microbial Biology, University of California, Berkeley, 111 Koshland Hall, Berkeley, CA 94720-3102, United States.
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Pan R, Jones AD, Hu J. Cardiolipin-mediated mitochondrial dynamics and stress response in Arabidopsis. THE PLANT CELL 2014; 26:391-409. [PMID: 24443516 PMCID: PMC3963584 DOI: 10.1105/tpc.113.121095] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 12/19/2013] [Accepted: 12/27/2013] [Indexed: 05/19/2023]
Abstract
Mitochondria are essential and dynamic organelles in eukaryotes. Cardiolipin (CL) is a key phospholipid in mitochondrial membranes, playing important roles in maintaining the functional integrity and dynamics of mitochondria in animals and yeasts. However, CL's role in plants is just beginning to be elucidated. In this study, we used Arabidopsis thaliana to examine the subcellular distribution of CL and CARDIOLIPIN SYNTHASE (CLS) and analyzed loss-of-function cls mutants for defects in mitochondrial morphogenesis and stress response. We show that CL localizes to mitochondria and is enriched at specific domains, and CLS targets to the inner membrane of mitochondria with its C terminus in the intermembrane space. Furthermore, cls mutants exhibit significantly impaired growth as well as altered structural integrity and morphogenesis of mitochondria. In contrast to animals and yeasts, in which CL's effect on mitochondrial fusion is more profound, Arabidopsis CL plays a dominant role in mitochondrial fission and exerts this function, at least in part, through stabilizing the protein complex of the major mitochondrial fission factor, DYNAMIN-RELATED PROTEIN3. CL also plays a role in plant responses to heat and extended darkness, stresses that induce programmed cell death. Our study has uncovered conserved and plant-specific aspects of CL biology in mitochondrial dynamics and the organism response to environmental stresses.
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Affiliation(s)
- Ronghui Pan
- Michigan State University–Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - A. Daniel Jones
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824
| | - Jianping Hu
- Michigan State University–Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
- Plant Biology Department, Michigan State University, East Lansing, Michigan 48824
- Address correspondence to
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Abstract
Remodeling of membranes by fission or fusion has been extensively studied in eukaryotes, but proteins directly responsible for mediating such events in bacteria have not been discovered. A recent report identified a protein in Bacillus subtilis that exploits an affinity for a specific lipid to drive membrane fission during sporulation.
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Affiliation(s)
- Irene S Tan
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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