1
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Herdman M, Isbilir B, von Kügelgen A, Schulze U, Wainman A, Bharat TAM. Cell cycle dependent coordination of surface layer biogenesis in Caulobacter crescentus. Nat Commun 2024; 15:3355. [PMID: 38637514 PMCID: PMC11026435 DOI: 10.1038/s41467-024-47529-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Accepted: 04/04/2024] [Indexed: 04/20/2024] Open
Abstract
Surface layers (S-layers) are proteinaceous, two-dimensional paracrystalline arrays that constitute a major component of the cell envelope in many prokaryotic species. In this study, we investigated S-layer biogenesis in the bacterial model organism Caulobacter crescentus. Fluorescence microscopy revealed localised incorporation of new S-layer at the poles and mid-cell, consistent with regions of cell growth in the cell cycle. Light microscopy and electron cryotomography investigations of drug-treated bacteria revealed that localised S-layer insertion is retained when cell division is inhibited, but is disrupted upon dysregulation of MreB or lipopolysaccharide. We further uncovered that S-layer biogenesis follows new peptidoglycan synthesis and localises to regions of high cell wall turnover. Finally, correlated cryo-light microscopy and electron cryotomographic analysis of regions of S-layer insertion showed the presence of discontinuities in the hexagonal S-layer lattice, contrasting with other S-layers completed by defined symmetric defects. Our findings present insights into how C. crescentus cells form an ordered S-layer on their surface in coordination with the biogenesis of other cell envelope components.
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Affiliation(s)
- Matthew Herdman
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK
| | - Buse Isbilir
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Andriko von Kügelgen
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Ulrike Schulze
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Alan Wainman
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK
| | - Tanmay A M Bharat
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK.
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2
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van Teeseling MCF. Elongation at Midcell in Preparation of Cell Division Requires FtsZ, but Not MreB nor PBP2 in Caulobacter crescentus. Front Microbiol 2021; 12:732031. [PMID: 34512611 PMCID: PMC8429850 DOI: 10.3389/fmicb.2021.732031] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/09/2021] [Indexed: 02/04/2023] Open
Abstract
Controlled growth of the cell wall is a key prerequisite for bacterial cell division. The existing view of the canonical rod-shaped bacterial cell dictates that newborn cells first elongate throughout their side walls using the elongasome protein complex, and subsequently use the divisome to coordinate constriction of the dividing daughter cells. Interestingly, another growth phase has been observed in between elongasome-mediated elongation and constriction, during which the cell elongates from the midcell outward. This growth phase, that has been observed in Escherichia coli and Caulobacter crescentus, remains severely understudied and its mechanisms remain elusive. One pressing open question is which role the elongasome key-component MreB plays in this respect. This study quantitatively investigates this growth phase in C. crescentus and focuses on the role of both divisome and elongasome components. This growth phase is found to initiate well after MreB localizes at midcell, although it does not require its presence at this subcellular location nor the action of key elongasome components. Instead, the divisome component FtsZ seems to be required for elongation at midcell. This study thus shines more light on this growth phase in an important model organism and paves the road to more in-depth studies.
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Affiliation(s)
- Muriel C F van Teeseling
- Junior Research Group Prokaryotic Cell Biology, Department Microbial Interactions, Institute of Microbiology, Friedrich-Schiller-Universität, Jena, Germany.,Department of Biology, University of Marburg, Marburg, Germany
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3
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Sugar-Phosphate Metabolism Regulates Stationary-Phase Entry and Stalk Elongation in Caulobacter crescentus. J Bacteriol 2020; 202:JB.00468-19. [PMID: 31767777 DOI: 10.1128/jb.00468-19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Accepted: 11/17/2019] [Indexed: 12/28/2022] Open
Abstract
Bacteria have a variety of mechanisms for adapting to environmental perturbations. Changes in oxygen availability result in a switch between aerobic and anaerobic respiration, whereas iron limitation may lead to siderophore secretion. In addition to metabolic adaptations, many organisms respond by altering their cell shape. Caulobacter crescentus, when grown under phosphate-limiting conditions, dramatically elongates its polar stalk appendage. The stalk is hypothesized to facilitate phosphate uptake; however, the mechanistic details of stalk synthesis are not well characterized. We used a chemical mutagenesis approach to isolate and characterize stalk-deficient mutants, one of which had two mutations in the phosphomannose isomerase gene (manA) that were necessary and sufficient to inhibit stalk elongation. Transcription of the pho regulon was unaffected in the manA mutant; therefore, ManA plays a unique regulatory role in stalk synthesis. The mutant ManA had reduced enzymatic activity, resulting in a 5-fold increase in the intracellular fructose 6-phosphate/mannose 6-phosphate ratio. This metabolic imbalance impaired the synthesis of cellular envelope components derived from mannose 6-phosphate, namely, lipopolysaccharide O-antigen and exopolysaccharide. Furthermore, the manA mutations prevented C. crescentus cells from efficiently entering stationary phase. Deletion of the stationary-phase response regulator gene spdR inhibited stalk elongation in wild-type cells, while overproduction of the alarmone ppGpp, which triggers growth arrest and stationary-phase entry, increased stalk length in the manA mutant strain. These results demonstrate that sugar-phosphate metabolism regulates stalk elongation independently of phosphate starvation.IMPORTANCE Metabolic control of bacterial cell shape is an important mechanism for adapting to environmental perturbations. Caulobacter crescentus dramatically elongates its polar stalk appendage in response to phosphate starvation. To investigate the mechanism of this morphological adaptation, we isolated stalk-deficient mutants, one of which had mutations in the phosphomannose isomerase gene (manA) that blocked stalk elongation, despite normal activation of the phosphate starvation response. The mutant ManA resulted in an imbalance in sugar-phosphate concentrations, which had effects on the synthesis of cellular envelope components and entry into stationary phase. Due to the interconnectivity of metabolic pathways, our findings may suggest more generally that the modulation of bacterial cell shape involves the regulation of growth phase and the synthesis of cellular building blocks.
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4
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Lariviere PJ, Mahone CR, Santiago-Collazo G, Howell M, Daitch AK, Zeinert R, Chien P, Brown PJB, Goley ED. An Essential Regulator of Bacterial Division Links FtsZ to Cell Wall Synthase Activation. Curr Biol 2019; 29:1460-1470.e4. [PMID: 31031115 PMCID: PMC6504580 DOI: 10.1016/j.cub.2019.03.066] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 02/01/2019] [Accepted: 03/27/2019] [Indexed: 11/18/2022]
Abstract
Bacterial growth and division require insertion of new peptidoglycan (PG) into the existing cell wall by PG synthase enzymes. Emerging evidence suggests that many PG synthases require activation to function; however, it is unclear how activation of division-specific PG synthases occurs. The FtsZ cytoskeleton has been implicated as a regulator of PG synthesis during division, but the mechanisms through which it acts are unknown. Here, we show that FzlA, an FtsZ-binding protein and essential regulator of constriction in Caulobacter crescentus, helps link FtsZ to PG synthesis to promote division. We find that hyperactive mutants of the PG synthases FtsW and FtsI specifically render fzlA, but not other division genes, non-essential. However, FzlA is still required to maintain proper constriction rate and efficiency in a hyperactive PG synthase background. Intriguingly, loss of fzlA in the presence of hyperactivated FtsWI causes cells to rotate about the division plane during constriction and sensitizes cells to cell-wall-specific antibiotics. We demonstrate that FzlA-dependent signaling to division-specific PG synthesis is conserved in another α-proteobacterium, Agrobacterium tumefaciens. These data establish that FzlA helps link FtsZ to cell wall remodeling and is required for signaling to both activate and spatially orient PG synthesis during division. Overall, our findings support the paradigm that activation of SEDS-PBP PG synthases is a broadly conserved requirement for bacterial morphogenesis.
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Affiliation(s)
- Patrick J Lariviere
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Christopher R Mahone
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | | | - Matthew Howell
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Allison K Daitch
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Rilee Zeinert
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Pamela J B Brown
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Erin D Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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5
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Stankeviciute G, Miguel AV, Radkov A, Chou S, Huang KC, Klein EA. Differential modes of crosslinking establish spatially distinct regions of peptidoglycan in
Caulobacter crescentus. Mol Microbiol 2019; 111:995-1008. [DOI: 10.1111/mmi.14199] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2019] [Indexed: 11/28/2022]
Affiliation(s)
- Gabriele Stankeviciute
- Center for Computational and Integrative Biology Rutgers University‐Camden Camden NJ 08102USA
| | - Amanda V. Miguel
- Department of Bioengineering Stanford University Stanford CA 94305USA
| | - Atanas Radkov
- Department of Biochemistry and Biophysics University of California San Francisco San Francisco CA 94158USA
| | - Seemay Chou
- Department of Biochemistry and Biophysics University of California San Francisco San Francisco CA 94158USA
- Chan Zuckerberg Biohub San Francisco CA 94158USA
| | - Kerwyn Casey Huang
- Department of Bioengineering Stanford University Stanford CA 94305USA
- Chan Zuckerberg Biohub San Francisco CA 94158USA
- Department of Microbiology and Immunology Stanford University School of Medicine Stanford CA 94305USA
| | - Eric A. Klein
- Center for Computational and Integrative Biology Rutgers University‐Camden Camden NJ 08102USA
- Biology Department Rutgers University‐Camden Camden NJ 08102USA
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6
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A specialized MreB-dependent cell wall biosynthetic complex mediates the formation of stalk-specific peptidoglycan in Caulobacter crescentus. PLoS Genet 2019; 15:e1007897. [PMID: 30707707 PMCID: PMC6373972 DOI: 10.1371/journal.pgen.1007897] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 02/13/2019] [Accepted: 12/14/2018] [Indexed: 11/19/2022] Open
Abstract
Many bacteria have complex cell shapes, but the mechanisms producing their distinctive morphologies are still poorly understood. Caulobacter crescentus, for instance, exhibits a stalk-like extension that carries an adhesive holdfast mediating surface attachment. This structure forms through zonal peptidoglycan biosynthesis at the old cell pole and elongates extensively under phosphate-limiting conditions. We analyzed the composition of cell body and stalk peptidoglycan and identified significant differences in the nature and proportion of peptide crosslinks, indicating that the stalk represents a distinct subcellular domain with specific mechanical properties. To identify factors that participate in stalk formation, we systematically inactivated and localized predicted components of the cell wall biosynthetic machinery of C. crescentus. Our results show that the biosynthesis of stalk peptidoglycan involves a dedicated peptidoglycan biosynthetic complex that combines specific components of the divisome and elongasome, suggesting that the repurposing of preexisting machinery provides a straightforward means to evolve new morphological traits.
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7
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den Blaauwen T. Is Longitudinal Division in Rod-Shaped Bacteria a Matter of Swapping Axis? Front Microbiol 2018; 9:822. [PMID: 29867786 PMCID: PMC5952006 DOI: 10.3389/fmicb.2018.00822] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 04/11/2018] [Indexed: 01/21/2023] Open
Abstract
The morphology of bacterial species shows a wealth of variation from star-shaped to spherical and rod- to spiral-shaped, to mention a few. Their mode of growth and division is also very diverse and flexible ranging from polar growth and lateral surface increase to midcell expansion and from perpendicular to longitudinal asymmetric division. Gammaproteobacterial rod-shaped species such as Escherchia coli divide perpendicularly and grow in length, whereas the genetically very similar rod-shaped symbiotic Thiosymbion divide longitudinally, and some species even divide asynchronously while growing in width. The ovococcal Streptococcus pneumoniae also lengthens and divides perpendicularly, yet it is genetically very different from E. coli. Are these differences as dramatic as is suggested by visual inspection, or can they all be achieved by subtle variation in the regulation of the same protein complexes that synthesize the cell envelope? Most bacteria rely on the cytoskeletal polymer FtsZ to organize cell division, but only a subset of species use the actin homolog MreB for length growth, although some of them are morphologically not that different. Poles are usually negative determinant for cell division. Curved cell poles can be inert or active with respect to peptidoglycan synthesis, can localize chemotaxis and other sensing proteins or other bacterial equipment, such as pili, depending on the species. But what is actually the definition of a pole? This review discusses the possible common denominators for growth and division of distinct and similar bacterial species.
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Affiliation(s)
- Tanneke den Blaauwen
- Bacterial Cell Biology and Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
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8
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Zielińska A, Billini M, Möll A, Kremer K, Briegel A, Izquierdo Martinez A, Jensen GJ, Thanbichler M. LytM factors affect the recruitment of autolysins to the cell division site in Caulobacter crescentus. Mol Microbiol 2017; 106:419-438. [PMID: 28833791 DOI: 10.1111/mmi.13775] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/18/2017] [Indexed: 12/24/2022]
Abstract
Most bacteria possess a peptidoglycan cell wall that determines their morphology and provides mechanical robustness during osmotic challenges. The biosynthesis of this structure is achieved by a large set of synthetic and lytic enzymes with varying substrate specificities. Although the biochemical functions of these proteins are conserved and well-investigated, the precise roles of individual factors and the regulatory mechanisms coordinating their activities in time and space remain incompletely understood. Here, we comprehensively analyze the autolytic machinery of the alphaproteobacterial model organism Caulobacter crescentus, with a specific focus on LytM-like endopeptidases, soluble lytic transglycosylases and amidases. Our data reveal a high degree of redundancy within each protein family but also specialized functions for individual family members under stress conditions. In addition, we identify two lytic transglycosylases and an amidase as new divisome components that are recruited to midcell at distinct stages of the cell cycle. The midcell localization of these proteins is affected by two LytM factors with degenerate catalytic domains, DipM and LdpF, which may serve as regulatory hubs coordinating the activities of multiple autolytic enzymes during cell constriction and fission respectively. These findings set the stage for in-depth studies of the molecular mechanisms that control peptidoglycan remodeling in C. crescentus.
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Affiliation(s)
- Aleksandra Zielińska
- Faculty of Biology, Philipps-Universität, Marburg 35043, Germany.,Max Planck Institute for Terrestrial Microbiology, Marburg 35043, Germany
| | - Maria Billini
- Faculty of Biology, Philipps-Universität, Marburg 35043, Germany.,Max Planck Institute for Terrestrial Microbiology, Marburg 35043, Germany
| | - Andrea Möll
- Faculty of Biology, Philipps-Universität, Marburg 35043, Germany.,Max Planck Institute for Terrestrial Microbiology, Marburg 35043, Germany
| | - Katharina Kremer
- Faculty of Biology, Philipps-Universität, Marburg 35043, Germany
| | - Ariane Briegel
- Divison of Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.,Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Adrian Izquierdo Martinez
- Faculty of Biology, Philipps-Universität, Marburg 35043, Germany.,Max Planck Institute for Terrestrial Microbiology, Marburg 35043, Germany
| | - Grant J Jensen
- Divison of Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.,Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Martin Thanbichler
- Faculty of Biology, Philipps-Universität, Marburg 35043, Germany.,Max Planck Institute for Terrestrial Microbiology, Marburg 35043, Germany.,LOEWE Center for Synthetic Microbiology, Marburg 35043, Germany
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9
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Curtis PD. Stalk formation of Brevundimonas and how it compares to Caulobacter crescentus. PLoS One 2017; 12:e0184063. [PMID: 28886080 PMCID: PMC5590869 DOI: 10.1371/journal.pone.0184063] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 08/17/2017] [Indexed: 11/18/2022] Open
Abstract
The Caulobacter crescentus cell extension known as a stalk represents an unusual bacterial morphology. C. crescentus produces stalks under multiple nutrient conditions, but the length of the stalk is increased in response to phosphate starvation. However, the exact function of the stalk is not known, nor is it known how much stalk biogenesis or function is conserved with other stalked bacteria. Work presented here shows that many organisms in the Caulobacter genus and the next closest genus (Brevundimonas) generally do not synthesize stalks in the relatively-rich PYE growth medium, suggesting that the synthesis of a stalk under nutrient-rich conditions by C. crescentus may be the exception instead of the norm among its phylogenetic group. Brevundimonas subvibrioides can be induced to synthesize stalks by genetically mimicking phosphate starvation conditions, indicating stalk synthesis in this organism may be performed on an as-need basis. This mutation, however, does not appear to increase the incidence of holdfast synthesis. While B. subvibrioides stalks appear to be synthesized with the same polarity with respect to holdfast as C. crescentus stalks, evidence is presented that suggests B. subvibrioides may disassemble stalks when they are no longer needed. Many homologs of C. crescentus genes encoding stalk-associated proteins are absent in the B. subvibrioides genome, and B. subvibrioides PstA-GFP as well as C. crescentus StpX-GFP are able to enter the B. subvibrioides stalk compartment, calling into question the level of compartmentalization of the B. subvibrioides stalk. In summary, this work begins to address how much the C. crescentus model for this unusual morphological adaptation can be extended to related organisms.
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Affiliation(s)
- Patrick D. Curtis
- Department of Biology, University of Mississippi, University, MS, United States of America
- * E-mail:
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10
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Meier EL, Razavi S, Inoue T, Goley ED. A novel membrane anchor for FtsZ is linked to cell wall hydrolysis in Caulobacter crescentus. Mol Microbiol 2016; 101:265-80. [PMID: 27028265 DOI: 10.1111/mmi.13388] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 03/29/2016] [Accepted: 03/29/2016] [Indexed: 12/23/2022]
Abstract
In most bacteria, the tubulin-like GTPase FtsZ forms an annulus at midcell (the Z-ring) which recruits the division machinery and regulates cell wall remodeling. Although both activities require membrane attachment of FtsZ, few membrane anchors have been characterized. FtsA is considered to be the primary membrane tether for FtsZ in bacteria, however in Caulobacter crescentus, FtsA arrives at midcell after stable Z-ring assembly and early FtsZ-directed cell wall synthesis. We hypothesized that additional proteins tether FtsZ to the membrane and demonstrate that in C. crescentus, FzlC is one such membrane anchor. FzlC associates with membranes directly in vivo and in vitro and recruits FtsZ to membranes in vitro. As for most known membrane anchors, the C-terminal peptide of FtsZ is required for its recruitment to membranes by FzlC in vitro and midcell recruitment of FzlC in cells. In vivo, overproduction of FzlC causes cytokinesis defects whereas deletion of fzlC causes synthetic defects with dipM, ftsE and amiC mutants, implicating FzlC in cell wall hydrolysis. Our characterization of FzlC as a novel membrane anchor for FtsZ expands our understanding of FtsZ regulators and establishes a role for membrane-anchored FtsZ in the regulation of cell wall hydrolysis.
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Affiliation(s)
- Elizabeth L Meier
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, Maryland, 21205, USA
| | - Shiva Razavi
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, Maryland, 21205, USA
| | - Takanari Inoue
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, Maryland, 21205, USA.,Department of Cell Biology, Johns Hopkins University School of Medicine, 855 N. Wolfe Street, Baltimore, Maryland, 21205, USA
| | - Erin D Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, Maryland, 21205, USA
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11
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Randich AM, Brun YV. Molecular mechanisms for the evolution of bacterial morphologies and growth modes. Front Microbiol 2015; 6:580. [PMID: 26106381 PMCID: PMC4460556 DOI: 10.3389/fmicb.2015.00580] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/26/2015] [Indexed: 12/13/2022] Open
Abstract
Bacteria exhibit a rich diversity of morphologies. Within this diversity, there is a uniformity of shape for each species that is replicated faithfully each generation, suggesting that bacterial shape is as selectable as any other biochemical adaptation. We describe the spatiotemporal mechanisms that target peptidoglycan synthesis to different subcellular zones to generate the rod-shape of model organisms Escherichia coli and Bacillus subtilis. We then demonstrate, using the related genera Caulobacter and Asticcacaulis as examples, how the modularity of the core components of the peptidoglycan synthesis machinery permits repositioning of the machinery to achieve different growth modes and morphologies. Finally, we highlight cases in which the mechanisms that underlie morphological evolution are beginning to be understood, and how they depend upon the expansion and diversification of the core components of the peptidoglycan synthesis machinery.
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Affiliation(s)
- Amelia M Randich
- Department of Biology, Indiana University , Bloomington, IN, USA
| | - Yves V Brun
- Department of Biology, Indiana University , Bloomington, IN, USA
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12
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Curtis PD, Brun YV. Identification of essential alphaproteobacterial genes reveals operational variability in conserved developmental and cell cycle systems. Mol Microbiol 2014; 93:713-35. [PMID: 24975755 DOI: 10.1111/mmi.12686] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2014] [Indexed: 12/22/2022]
Abstract
The cell cycle of Caulobacter crescentus is controlled by a complex signalling network that co-ordinates events. Genome sequencing has revealed many C. crescentus cell cycle genes are conserved in other Alphaproteobacteria, but it is not clear to what extent their function is conserved. As many cell cycle regulatory genes are essential in C. crescentus, the essential genes of two Alphaproteobacteria, Agrobacterium tumefaciens (Rhizobiales) and Brevundimonas subvibrioides (Caulobacterales), were elucidated to identify changes in cell cycle protein function over different phylogenetic distances as demonstrated by changes in essentiality. The results show the majority of conserved essential genes are involved in critical cell cycle processes. Changes in component essentiality reflect major changes in lifestyle, such as divisome components in A. tumefaciens resulting from that organism's different growth pattern. Larger variability of essentiality was observed in cell cycle regulators, suggesting regulatory mechanisms are more customizable than the processes they regulate. Examples include variability in the essentiality of divJ and divK spatial cell cycle regulators, and non-essentiality of the highly conserved and usually essential DNA methyltransferase CcrM. These results show that while essential cell functions are conserved across varying genetic distance, much of a given organism's essential gene pool is specific to that organism.
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Affiliation(s)
- Patrick D Curtis
- Department of Biology, University of Mississippi, University, MS, 38677, USA
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13
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Function and localization dynamics of bifunctional penicillin-binding proteins in Caulobacter crescentus. J Bacteriol 2014; 196:1627-39. [PMID: 24532768 DOI: 10.1128/jb.01194-13] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The peptidoglycan cell wall of bacteria is a complex macromolecule composed of glycan strands that are cross-linked by short peptide bridges. Its biosynthesis involves a conserved group of enzymes, the bifunctional penicillin-binding proteins (bPBPs), which contain both a transglycosylase and a transpeptidase domain, thus being able to elongate the glycan strands and, at the same time, generate the peptide cross-links. The stalked model bacterium Caulobacter crescentus possesses five bPBP paralogs, named Pbp1A, PbpC, PbpX, PbpY, and PbpZ, whose function is still incompletely understood. In this study, we show that any of these proteins except for PbpZ is sufficient for growth and normal morphogenesis when expressed at native or elevated levels, whereas inactivation of all five paralogs is lethal. Growth analyses indicate a central role of PbpX in the resistance of C. crescentus against the noncanonical amino acid d-alanine. Moreover, we show that PbpX and PbpY localize to the cell division site. Their recruitment to the divisome is dependent on the essential cell division protein FtsN and likely involves interactions with FtsL and the putative peptidoglycan hydrolase DipM. The same interaction pattern is observed for Pbp1A and PbpC, although these proteins do not accumulate at midcell. Our findings demonstrate that the bPBPs of C. crescentus are, to a large extent, redundant and have retained the ability to interact with the peptidoglycan biosynthetic machineries responsible for cell elongation, cytokinesis, and stalk growth. Nevertheless, they may preferentially act in specific peptidoglycan biosynthetic complexes, thereby facilitating the independent regulation of distinct growth processes.
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