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The MinCDE Cell Division System Participates in the Regulation of Type III Secretion System (T3SS) Genes, Bacterial Virulence, and Motility in Xanthomonas oryzae pv. oryzae. Microorganisms 2022; 10:microorganisms10081549. [PMID: 36013967 PMCID: PMC9414521 DOI: 10.3390/microorganisms10081549] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/27/2022] [Accepted: 07/28/2022] [Indexed: 11/17/2022] Open
Abstract
Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight (BLB) in rice, which is one of the most severe bacterial diseases in rice in some Asian countries. The type III secretion system (T3SS) of Xoo encoded by the hypersensitive response and pathogenicity (hrp) genes is essential for its pathogenicity in host rice. Here, we identified the Min system (MinC, MinD, and MinE), a negative regulatory system for bacterial cell division encoded by minC, minD, and minE genes, which is involved in negative regulation of hrp genes (hrpB1 and hrpF) in Xoo. We found that the deletion of minC, minD, and minCDE resulted in enhanced hrpB1 and hrpF expression, which is dependent on two key hrp regulators HrpG and HrpX. The minC, minD, and minCDE mutants exhibited elongated cell lengths, and the classic Min system-defective cell morphology including minicells and short filamentations. Mutation of minC in Xoo resulted in significantly impaired virulence in host rice, swimming motility, and enhanced biofilm formation. Our transcriptome profiling also indicated some virulence genes were differentially expressed in the minC mutants. To our knowledge, this is the first report about the Min system participating in the regulation of T3SS expression. It sheds light on the understanding of Xoo virulence mechanisms.
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Warr AR, Klimova AN, Nwaobasi AN, Sandler SJ. Protease-deficient SOS constitutive cells have RecN-dependent cell division phenotypes. Mol Microbiol 2018; 111:405-422. [PMID: 30422330 DOI: 10.1111/mmi.14162] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/06/2018] [Indexed: 02/05/2023]
Abstract
In Escherichia coli, after DNA damage, the SOS response increases the transcription (and protein levels) of approximately 50 genes. As DNA repair ensues, the level of transcription returns to homeostatic levels. ClpXP and other proteases return the high levels of several SOS proteins to homeostasis. When all SOS genes are constitutively expressed and many SOS proteins are stabilized by the removal of ClpXP, microscopic analysis shows that cells filament, produce mini-cells and have branching protrusions along their length. The only SOS gene required (of 19 tested) for the cell length phenotype is recN. RecN is a member of the Structural Maintenance of Chromosome (SMC) class of proteins. It can hold pieces of DNA together and is important for double-strand break repair (DSBR). RecN is degraded by ClpXP. Overexpression of recN+ in the absence of ClpXP or recN4174 (A552S, A553V), a mutant not recognized by ClpXP, produce filamentous cells with nucleoid partitioning defects. It is hypothesized that when produced at high levels during the SOS response, RecN interferes with nucleoid partitioning and Z-Ring function by holding together sections of the nucleoid, or sister nucleoids, providing another way to inhibit cell division.
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Affiliation(s)
- Alyson R Warr
- Department of Microbiology, Morrill Science Center IV N203, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Anastasiia N Klimova
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Amy N Nwaobasi
- Department of Microbiology, Morrill Science Center IV N203, University of Massachusetts Amherst, Amherst, MA, 01003, USA.,University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT, 06032, USA
| | - Steven J Sandler
- Department of Microbiology, Morrill Science Center IV N203, University of Massachusetts Amherst, Amherst, MA, 01003, USA.,Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA, 01003, USA
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Lorenzoni ASG, Dantas GC, Bergsma T, Ferreira H, Scheffers DJ. Xanthomonas citri MinC Oscillates from Pole to Pole to Ensure Proper Cell Division and Shape. Front Microbiol 2017; 8:1352. [PMID: 28769912 PMCID: PMC5515816 DOI: 10.3389/fmicb.2017.01352] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 07/04/2017] [Indexed: 01/08/2023] Open
Abstract
Xanthomonas citri (Xac) is the causal agent of citrus canker, a disease that affects citrus crops and causes economic impact worldwide. To further characterize cell division in this plant pathogen, we investigated the role of the protein MinC in cell division, chromosome segregation, and peptidoglycan incorporation by deleting the gene minC using allele exchange. Xac with minC deleted exhibited the classic Δmin phenotype observed in other bacteria deleted for min components: minicells and short filamentation. In addition we noticed the formation of branches, which is similar to what was previously described for Escherichia coli deleted for either min or for several low molecular weight penicillin-binding proteins (PBPs). The branching phenotype was medium dependent and probably linked to gluconeogenic growth. We complemented the minC gene by integrating gfp-minC into the amy locus. Xac complemented strains displayed a wild-type phenotype. In addition, GFP-MinC oscillated from pole to pole, similar to MinCD oscillations observed in E. coli and more recently in Synechococcus elongatus. Further investigation of the branching phenotype revealed that in branching cells nucleoid organization, divisome formation and peptidoglycan incorporation were disrupted.
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Affiliation(s)
- André S G Lorenzoni
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningen, Netherlands
| | - Giordanni C Dantas
- Departamento de Bioquímica e Microbiologia, Instituto de Biociências, Universidade Estadual PaulistaRio Claro, Brazil
| | - Tessa Bergsma
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningen, Netherlands
| | - Henrique Ferreira
- Departamento de Bioquímica e Microbiologia, Instituto de Biociências, Universidade Estadual PaulistaRio Claro, Brazil
| | - Dirk-Jan Scheffers
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningen, Netherlands
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Kawazura T, Matsumoto K, Kojima K, Kato F, Kanai T, Niki H, Shiomi D. Exclusion of assembled MreB by anionic phospholipids at cell poles confers cell polarity for bidirectional growth. Mol Microbiol 2017; 104:472-486. [PMID: 28164388 DOI: 10.1111/mmi.13639] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/29/2017] [Indexed: 12/21/2022]
Abstract
Cell polarity determines the direction of cell growth in bacteria. MreB actin spatially regulates peptidoglycan synthesis to enable cells to elongate bidirectionally. MreB densely localizes in the cylindrical part of the rod cell and not in polar regions in Escherichia coli. When treated with A22, which inhibits MreB polymerization, rod-shaped cells became round and MreB was diffusely distributed throughout the cytoplasmic membrane. A22 removal resulted in restoration of the rod shape. Initially, diffuse MreB started to re-assemble, and MreB-free zones were subsequently observed in the cytoplasmic membrane. These MreB-free zones finally became cell poles, allowing the cells to elongate bidirectionally. When MreB was artificially located at the cell poles, an additional pole was created, indicating that artificial localization of MreB at the cell pole induced local peptidoglycan synthesis. It was found that the anionic phospholipids (aPLs), phosphatidylglycerol and cardiolipin, which were enriched in cell poles preferentially interact with monomeric MreB compared with assembled MreB in vitro. MreB tended to localize to cell poles in cells lacking both aPLs, resulting in production of Y-shaped cells. Their findings indicated that aPLs exclude assembled MreB from cell poles to establish cell polarity, thereby allowing cells to elongate in a particular direction.
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Affiliation(s)
- Takuma Kawazura
- Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan
| | - Kanon Matsumoto
- Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan
| | - Koki Kojima
- Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan
| | - Fumiya Kato
- Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan
| | - Tomomi Kanai
- Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan
| | - Hironori Niki
- Microbial Genetics Laboratory, Genetic Strains Research Center, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan.,Department of Genetics, The Graduate University for Advanced Studies, Sokendai, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan
| | - Daisuke Shiomi
- Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan
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Kirsebom LA, Dasgupta S, Fredrik Pettersson BM. Pleiomorphism in Mycobacterium. ADVANCES IN APPLIED MICROBIOLOGY 2016; 80:81-112. [PMID: 22794145 DOI: 10.1016/b978-0-12-394381-1.00004-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Morphological variants in mycobacterial cultures under different growth conditions, including aging of the culture, have been shown to include fibrous aggregates, biofilms, coccoids, and spores. Here we discuss the diversity in shape and size changes demonstrated by bacterial cells with special reference to pleiomorphism observed in Mycobacterium spp. in response to nutritional and other environmental stresses. Inherent asymmetry in cell division and compartmentalization of cell interior under different growth conditions might contribute toward the observed pleiomorphism in mycobacteria. The regulatory genes comprising the bacterial signaling pathway responsible for initiating morphogenesis are speculated upon from bioinformatic identifications of genes for known sensors, kinases, and phosphatases existing in mycobacterial genomes as well as on the basis of what is known in other bacteria.
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Claessen D, Rozen DE, Kuipers OP, Søgaard-Andersen L, van Wezel GP. Bacterial solutions to multicellularity: a tale of biofilms, filaments and fruiting bodies. Nat Rev Microbiol 2014; 12:115-24. [PMID: 24384602 DOI: 10.1038/nrmicro3178] [Citation(s) in RCA: 275] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Although bacteria frequently live as unicellular organisms, many spend at least part of their lives in complex communities, and some have adopted truly multicellular lifestyles and have abandoned unicellular growth. These transitions to multicellularity have occurred independently several times for various ecological reasons, resulting in a broad range of phenotypes. In this Review, we discuss the strategies that are used by bacteria to form and grow in multicellular structures that have hallmark features of multicellularity, including morphological differentiation, programmed cell death and patterning. In addition, we examine the evolutionary and ecological factors that lead to the wide range of coordinated multicellular behaviours that are observed in bacteria.
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Affiliation(s)
- Dennis Claessen
- 1] Molecular Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, P.O. Box 9502, 2300 RA Leiden, The Netherlands. [2]
| | - Daniel E Rozen
- 1] Molecular Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, P.O. Box 9502, 2300 RA Leiden, The Netherlands. [2]
| | - Oscar P Kuipers
- 1] Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Linnaeusborg, Nijenborgh 7, 9747 AG, Groningen, The Netherlands. [2] Kluyver Center for Genomics of Industrial Fermentation, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
| | - Lotte Søgaard-Andersen
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Strasse 10, 35043, Marburg, Germany
| | - Gilles P van Wezel
- Molecular Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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Association of a D-alanyl-D-alanine carboxypeptidase gene with the formation of aberrantly shaped cells during the induction of viable but nonculturable Vibrio parahaemolyticus. Appl Environ Microbiol 2013; 79:7305-12. [PMID: 24056454 DOI: 10.1128/aem.01723-13] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio parahaemolyticus is a halophilic Gram-negative bacterium that causes human gastroenteritis. When the viable but nonculturable (VBNC) state of this bacterium was induced by incubation at 4°C in Morita minimal salt solution containing 0.5% NaCl, the rod-shaped cells became coccoid, and various aberrantly shaped intermediates were formed in the initial stage. This study examined the factors that influence the formation of these aberrantly shaped cells. The proportion of aberrantly shaped cells was not affected in a medium containing D-cycloserine (50 μg/ml) but was lower in a medium containing cephalosporin C (10 μg/ml) than in the control medium without antibiotics. The proportion of aberrantly shaped cells was higher in a culture medium that contained 0.5% NaCl than in culture media containing 1.0 or 1.5% NaCl. The expression of 15 of 17 selected genes associated with cell wall synthesis was enhanced, and the expression of VP2468 (dacB), which encodes D-alanyl-D-alanine carboxypeptidase, was enhanced the most. The proportion of aberrantly shaped cells was significantly lower in the dacB mutant strain than in the parent strain, but the proportion was restored in the presence of the complementary dacB gene. This study suggests that disturbance of the dynamics of cell wall synthesis by enhanced expression of the VP2468 gene is associated with the formation of aberrantly shaped cells in the initial stage of induction of VBNC V. parahaemolyticus cells under specific conditions.
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Abstract
Rod-shaped bacteria such as Escherichia coli accurately maintain their shape from generation to generation. The cytoskeletal proteins MreB and FtsZ, which respectively guide parallel growth of the sidewall and perpendicular growth of the division septum, are important to maintain a straight sidewall and uniformly rounded cell poles. FtsZ normally assembles into a ring at the cell midpoint, called the Z ring, which is oriented perpendicular to the cell's axis and is thus in perfect position to guide growth of a perpendicular septum. In this issue of Molecular Microbiology, Potluri et al. show that low molecular weight penicillin binding proteins, particularly PBP5, have a role in maintaining the perpendicular geometry of the Z ring and subsequent septum in E. coli. When these factors are absent or perturbed, division septa are readily deformed, which results in abnormal cell poles that often bifurcate over time to generate branches. The data suggest that cellular branching in E. coli is specifically induced by aberrant septation events caused by mis-oriented Z rings and not by deformation of a growing cell pole or emergence of new tips from the sidewall, which are likely mechanisms of branching in other bacterial families.
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Affiliation(s)
- Veronica L Wells
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, TX 77030, USA
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Potluri LP, de Pedro MA, Young KD. Escherichia coli low-molecular-weight penicillin-binding proteins help orient septal FtsZ, and their absence leads to asymmetric cell division and branching. Mol Microbiol 2012; 84:203-24. [PMID: 22390731 DOI: 10.1111/j.1365-2958.2012.08023.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Escherichia coli cells lacking low-molecular-weight penicillin-binding proteins (LMW PBPs) exhibit morphological alterations that also appear when the septal protein FtsZ is mislocalized, suggesting that peptidoglycan modification and division may work together to produce cell shape. We found that in strains lacking PBP5 and other LMW PBPs, higher FtsZ concentrations increased the frequency of branched cells and incorrectly oriented Z rings by 10- to 15-fold. Invagination of these rings produced improperly oriented septa, which in turn gave rise to asymmetric cell poles that eventually elongated into branches. Branches always originated from the remnants of abnormal septation events, cementing the relationship between aberrant cell division and branch formation. In the absence of PBP5, PBP6 and DacD localized to nascent septa, suggesting that these PBPs can partially substitute for the loss of PBP5. We propose that branching begins when mislocalized FtsZ triggers the insertion of inert peptidoglycan at unusual positions during cell division. Only later, after normal cell wall elongation separates the patches, do branches become visible. Thus, a relationship between the LMW PBPs and cytoplasmic FtsZ ultimately affects cell division and overall shape.
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Affiliation(s)
- Lakshmi-Prasad Potluri
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
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Slayden RA, Belisle JT. Morphological features and signature gene response elicited by inactivation of FtsI in Mycobacterium tuberculosis. J Antimicrob Chemother 2008; 63:451-7. [PMID: 19109339 DOI: 10.1093/jac/dkn507] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES Universally conserved events in cell division provide the opportunity for the development of novel chemotherapeutics against Mycobacterium tuberculosis. The aim of this study was to use the beta-lactam antimicrobials cefalexin and piperacillin to inhibit FtsI and characterize the morphological changes and global transcriptional activities of genes to identify a signature response to FtsI inactivation. METHODS Cefalexin and piperacillin were used to block cell division, and microscopy was used to evaluate the effects on bacterial morphology and ultrastructure. Global transcriptional analysis was performed to determine the impact of FtsI inhibition on cell cycle processes and to identify molecular markers. RESULTS Inhibition of FtsI with cefalexin and piperacillin resulted in filamentous cells with multiple concentric rings and occasional branching as visualized by light and electron microscopy. Whole genome microarray-based transcriptional profiling and transcriptional mapping allowed the evaluation of cell cycle processes in response to inhibition of FtsI and characterization of transcriptional response and cell cycle processes. CONCLUSIONS This study substantiated that FtsZ-ring constriction and septal resolution require the transpeptidase activity of FtsI, making FtsI essential for cell division in M. tuberculosis. Therefore, FtsI is a target for drug discovery, and these studies provided a molecular signature of FtsI inactivation that can be applied to screening strategies for novel FtsI inhibitors.
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Affiliation(s)
- Richard A Slayden
- Department of Microbiology, Mycobacteria Research Laboratories, Colorado State University, Fort Collins, CO 80523, USA.
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Bacterial growth and cell division: a mycobacterial perspective. Microbiol Mol Biol Rev 2008; 72:126-56, table of contents. [PMID: 18322037 DOI: 10.1128/mmbr.00028-07] [Citation(s) in RCA: 271] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genus Mycobacterium is best known for its two major pathogenic species, M. tuberculosis and M. leprae, the causative agents of two of the world's oldest diseases, tuberculosis and leprosy, respectively. M. tuberculosis kills approximately two million people each year and is thought to latently infect one-third of the world's population. One of the most remarkable features of the nonsporulating M. tuberculosis is its ability to remain dormant within an individual for decades before reactivating into active tuberculosis. Thus, control of cell division is a critical part of the disease. The mycobacterial cell wall has unique characteristics and is impermeable to a number of compounds, a feature in part responsible for inherent resistance to numerous drugs. The complexity of the cell wall represents a challenge to the organism, requiring specialized mechanisms to allow cell division to occur. Besides these mycobacterial specializations, all bacteria face some common challenges when they divide. First, they must maintain their normal architecture during and after cell division. In the case of mycobacteria, that means synthesizing the many layers of complex cell wall and maintaining their rod shape. Second, they need to coordinate synthesis and breakdown of cell wall components to maintain integrity throughout division. Finally, they need to regulate cell division in response to environmental stimuli. Here we discuss these challenges and the mechanisms that mycobacteria employ to meet them. Because these organisms are difficult to study, in many cases we extrapolate from information known for gram-negative bacteria or more closely related GC-rich gram-positive organisms.
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Abstract
Recent advances have shown conclusively that bacterial cells possess distant but true homologues of actin (MreB, ParM, and the recently uncovered MamK protein). Despite weak amino acid sequence similarity, MreB and ParM exhibit high structural homology to actin. Just like F-actin in eukaryotes, MreB and ParM assemble into highly dynamic filamentous structures in vivo and in vitro. MreB-like proteins are essential for cell viability and have been implicated in major cellular processes, including cell morphogenesis, chromosome segregation, and cell polarity. ParM (a plasmid-encoded actin homologue) is responsible for driving plasmid-DNA partitioning. The dynamic prokaryotic actin-like cytoskeleton is thought to serve as a central organizer for the targeting and accurate positioning of proteins and nucleoprotein complexes, thereby (and by analogy to the eukaryotic cytoskeleton) spatially and temporally controlling macromolecular trafficking in bacterial cells. In this paper, the general properties and known functions of the actin orthologues in bacteria are reviewed.
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Affiliation(s)
- Rut Carballido-López
- Génétique Microbienne, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas Cedex, France.
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Zaritsky A, Woldringh CL, Einav M, Alexeeva S. Use of thymine limitation and thymine starvation to study bacterial physiology and cytology. J Bacteriol 2006; 188:1667-79. [PMID: 16484178 PMCID: PMC1426543 DOI: 10.1128/jb.188.5.1667-1679.2006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Arieh Zaritsky
- Department of Life Sciences, Ben-Gurion University of the Negev, POB 653, Be'er-Sheva 84105, Israel.
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14
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Scheffers DJ, Pinho MG. Bacterial cell wall synthesis: new insights from localization studies. Microbiol Mol Biol Rev 2006; 69:585-607. [PMID: 16339737 PMCID: PMC1306805 DOI: 10.1128/mmbr.69.4.585-607.2005] [Citation(s) in RCA: 414] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In order to maintain shape and withstand intracellular pressure, most bacteria are surrounded by a cell wall that consists mainly of the cross-linked polymer peptidoglycan (PG). The importance of PG for the maintenance of bacterial cell shape is underscored by the fact that, for various bacteria, several mutations affecting PG synthesis are associated with cell shape defects. In recent years, the application of fluorescence microscopy to the field of PG synthesis has led to an enormous increase in data on the relationship between cell wall synthesis and bacterial cell shape. First, a novel staining method enabled the visualization of PG precursor incorporation in live cells. Second, penicillin-binding proteins (PBPs), which mediate the final stages of PG synthesis, have been localized in various model organisms by means of immunofluorescence microscopy or green fluorescent protein fusions. In this review, we integrate the knowledge on the last stages of PG synthesis obtained in previous studies with the new data available on localization of PG synthesis and PBPs, in both rod-shaped and coccoid cells. We discuss a model in which, at least for a subset of PBPs, the presence of substrate is a major factor in determining PBP localization.
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Affiliation(s)
- Dirk-Jan Scheffers
- Department of Molecular Microbiology, Institute of Molecular Cell Biology, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands.
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Abstract
In rod-shaped bacteria, a surprisingly large number of proteins are localized to the cell poles. Polar positioning of proteins is crucial to many fundamental cellular processes. Formation of the pole occurs at the time of a prior cell division event and involves coordination of the cell division machinery with septal placement of newly-synthesized peptidoglycan. Development of polar peptidoglycan and outer membrane depends on the formation of the cytokinetic FtsZ ring at midcell. By contrast, positioning of at least two polar proteins depends on signals independent of both the assembly of the FtsZ ring and the synthesis of septal and polar peptidoglycan. We propose a model for distinct but interrelated developmental pathways for polar cell envelope synthesis and positional information recognized by polar proteins.
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Affiliation(s)
- Anuradha Janakiraman
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital/Harvard Medical School, 65 Landsdowne St., Cambridge, MA 02139, USA
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Wagner JK, Galvani CD, Brun YV. Caulobacter crescentus requires RodA and MreB for stalk synthesis and prevention of ectopic pole formation. J Bacteriol 2005; 187:544-53. [PMID: 15629926 PMCID: PMC543564 DOI: 10.1128/jb.187.2.544-553.2005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Caulobacter crescentus cells treated with amdinocillin, an antibiotic which specifically inhibits the cell elongation transpeptidase penicillin binding protein 2 in Escherichia coli, exhibit defects in stalk elongation and morphology, indicating that stalk synthesis may be a specialized form of cell elongation. In order to investigate this possibility further, we examined the roles of two other proteins important for cell elongation, RodA and MreB. We show that, in C. crescentus, the rodA gene is essential and that RodA depletion leads to a loss of control over stalk and cell body diameter and a stalk elongation defect. In addition, we demonstrate that MreB depletion leads to a stalk elongation defect and conclude that stalk elongation is a more constrained form of cell elongation. Our results strongly suggest that MreB by itself does not determine the diameter of the cell body or stalk. Finally, we show that cells recovering from MreB depletion exhibit a strong budding and branching cell body phenotype and possess ectopic poles, as evidenced by the presence of multiple, misplaced, and sometimes highly branched stalks at the ends of these buds and branches. This phenotype is also seen to a lesser extent in cells recovering from RodA depletion and amdinocillin treatment. We conclude that MreB, RodA, and the target(s) of amdinocillin all contribute to the maintenance of cellular polarity in C. crescentus.
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Affiliation(s)
- Jennifer K Wagner
- Department of Biology, Indiana University, Bloomington, IN 47405-3700, USA
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17
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Abstract
In free-living eubacteria an external shell of peptidoglycan opposes internal hydrostatic pressure and prevents membrane rupture and death. At the same time, this wall imposes on each cell a shape. Because shape is both stable and heritable, as is the ability of many organisms to execute defined morphological transformations, cells must actively choose from among a large repertoire of available shapes. How they do so has been debated for decades, but recently experiment has begun to catch up with theory. Two discoveries are particularly informative. First, specific protein assemblies, nucleated by FtsZ, MreB or Mbl, appear to act as internal scaffolds that influence cell shape, perhaps by correctly localizing synthetic enzymes. Second, defects in cell shape are correlated with the presence of inappropriately placed, metabolically inert patches of peptidoglycan. When combined with what we know about mutants affecting cellular morphology, these observations suggest that bacteria may fabricate specific shapes by directing the synthesis of two kinds of cell wall: a long-lived, rigid framework that defines overall topology, and a metabolically plastic peptidoglycan whose shape is directed by internal scaffolds.
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Affiliation(s)
- Kevin D Young
- Department of Microbiology and Immunology, University of North Dakota School of Medicine, Grand Forks 58202-9037, USA.
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18
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Affiliation(s)
- Lawrence Rothfield
- Department of Microbiology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA.
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19
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de Pedro MA, Young KD, Höltje JV, Schwarz H. Branching of Escherichia coli cells arises from multiple sites of inert peptidoglycan. J Bacteriol 2003; 185:1147-52. [PMID: 12562782 PMCID: PMC142844 DOI: 10.1128/jb.185.4.1147-1152.2003] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Some strains of Escherichia coli defective for dacA, the gene coding for penicillin-binding protein 5, exhibit a strong branching phenotype when cell division is blocked. Since such branch formation implies a differentiation of polar caps at ectopic locations in the cell envelope, we analyzed murein segregation and observed a strong correlation between areas of inert murein and these morphological anomalies. In particular, the tips of branches exhibited the same properties as those described for polar caps of wild-type cells, i.e., the synthesis and turnover of murein were inhibited. Also, the mobility of cell envelope proteins was apparently constrained in areas with morphological defects. Polar regions of branching cells and sacculi had aberrant morphologies with a very high frequency. Of special interest was that areas of inert murein at polar caps were often split by areas of active synthesis, a situation unlike that observed in wild-type cells. These observations suggest that in dacA mutants, branches and other morphological anomalies may arise from split polar caps or by de novo generation of new poles built around inert peptidoglycan patches in the side walls of the cell.
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Affiliation(s)
- Miguel A de Pedro
- Centro de Biología Molecular "Severo Ochoa," Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain.
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Yu XC, Margolin W. Deletion of the min operon results in increased thermosensitivity of an ftsZ84 mutant and abnormal FtsZ ring assembly, placement, and disassembly. J Bacteriol 2000; 182:6203-13. [PMID: 11029443 PMCID: PMC94757 DOI: 10.1128/jb.182.21.6203-6213.2000] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To investigate the interaction between FtsZ and the Min system during cell division of Escherichia coli, we examined the effects of combining a well-known thermosensitive mutation of ftsZ, ftsZ84, with DeltaminCDE, a deletion of the entire min locus. Because the Min system is thought to down-regulate Z-ring assembly, the prediction was that removing minCDE might at least partially suppress the thermosensitivity of ftsZ84, which can form colonies below 42 degrees C but not at or above 42 degrees C. Contrary to expectations, the double mutant was significantly more thermosensitive than the ftsZ84 single mutant. When shifted to the new lower nonpermissive temperature, the double mutant formed long filaments mostly devoid of Z rings, suggesting a likely cause of the increased thermosensitivity. Interestingly, even at 22 degrees C, many Z rings were missing in the double mutant, and the rings that were present were predominantly at the cell poles. Of these, a large number were present only at one pole. These cells exhibited a higher than expected incidence of polar divisions, with a bias toward the newest pole. Moreover, some cells exhibited dramatically elongated septa that stained for FtsZ, suggesting that the double mutant is defective in Z-ring disassembly, and providing a possible mechanism for the polar bias. Thermoresistant suppressors of the double mutant arose that had modestly increased levels of FtsZ84. These cells also exhibited elongated septa and, in addition, produced a high frequency of branched cells. A thermoresistant suppressor of the ftsZ84 single mutant also synthesized more FtsZ84 and produced branched cells. The evidence from this study indicates that removing the Min system exposes and exacerbates the inherent defects of the FtsZ84 protein, resulting in clear septation phenotypes even at low growth temperatures. Increasing levels of FtsZ84 can suppress some, but not all, of these phenotypes.
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Affiliation(s)
- X C Yu
- Department of Microbiology and Molecular Genetics, University of Texas-Houston Medical School, Houston, Texas 77030, USA
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Abstract
Perhaps the biggest single task facing a bacterial cell is to divide into daughter cells that contain the normal complement of chromosomes. Recent technical and conceptual breakthroughs in bacterial cell biology, combined with the flood of genome sequence information and the excellent genetic tools in several model systems, have shed new light on the mechanism of prokaryotic cell division. There is good evidence that in most species, a molecular machine, organized by the tubulin-like FtsZ protein, assembles at the site of division and orchestrates the splitting of the cell. The determinants that target the machine to the right place at the right time are beginning to be understood in the model systems, but it is still a mystery how the machine actually generates the constrictive force necessary for cytokinesis. Moreover, although some cell division determinants such as FtsZ are present in a broad spectrum of prokaryotic species, the lack of FtsZ in some species and different profiles of cell division proteins in different families suggests that there are diverse mechanisms for regulating cell division.
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Affiliation(s)
- W Margolin
- Department of Microbiology and Molecular Genetics, University of Texas-Houston Medical School, 6431 Fannin, Houston, Texas 77030, USA.
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Nelson DE, Young KD. Penicillin binding protein 5 affects cell diameter, contour, and morphology of Escherichia coli. J Bacteriol 2000; 182:1714-21. [PMID: 10692378 PMCID: PMC94470 DOI: 10.1128/jb.182.6.1714-1721.2000] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although general physiological functions have been ascribed to the high-molecular-weight penicillin binding proteins (PBPs) of Escherichia coli, the low-molecular-weight PBPs have no well-defined biological roles. When we examined the morphology of a set of E. coli mutants lacking multiple PBPs, we observed that strains expressing active PBP 5 produced cells of normal shape, while mutants lacking PBP 5 produced cells with altered diameters, contours, and topological features. These morphological effects were visible in untreated cells, but the defects were exacerbated in cells forced to filament by inactivation of PBP 3 or FtsZ. After filamentation, cellular diameter varied erratically along the length of individual filaments and many filaments exhibited extensive branching. Also, in general, the mean diameter of cells lacking PBP 5 was significantly increased compared to that of cells from isogenic strains expressing active PBP 5. Expression of cloned PBP 5 reversed the effects observed in DeltadacA mutants. Although deletion of PBP 5 was required for these phenotypes, the absence of additional PBPs magnified the effects. The greatest morphological alterations required that at least three PBPs in addition to PBP 5 be deleted from a single strain. In the extreme cases in which six or seven PBPs were deleted from a single mutant, cells and cell filaments expressing PBP 5 retained a normal morphology but cells and filaments lacking PBP 5 were aberrant. In no case did mutation of another PBP produce the same drastic morphological effects. We conclude that among the low-molecular-weight PBPs, PBP 5 plays a principle role in determining cell diameter, surface uniformity, and overall topology of the peptidoglycan sacculus.
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Affiliation(s)
- D E Nelson
- Department of Microbiology and Immunology, School of Medicine, University of North Dakota, Grand Forks, North Dakota 58202-9037, USA
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