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Yagüe P, Willemse J, Xiao X, Zhang L, Manteca A, van Wezel GP. FtsZ phosphorylation pleiotropically affects Z-ladder formation, antibiotic production, and morphogenesis in Streptomyces coelicolor. Antonie Van Leeuwenhoek 2023; 116:1-19. [PMID: 36383329 PMCID: PMC9823044 DOI: 10.1007/s10482-022-01778-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 08/27/2022] [Indexed: 11/17/2022]
Abstract
The GTPase FtsZ forms the cell division scaffold in bacteria, which mediates the recruitment of the other components of the divisome. Streptomycetes undergo two different forms of cell division. Septa without detectable peptidoglycan divide the highly compartmentalised young hyphae during early vegetative growth, and cross-walls are formed that dissect the hyphae into long multinucleoid compartments in the substrate mycelium, while ladders of septa are formed in the aerial hyphae that lead to chains of uninucleoid spores. In a previous study, we analysed the phosphoproteome of Streptomyces coelicolor and showed that FtsZ is phosphorylated at Ser 317 and Ser389. Substituting Ser-Ser for either Glu-Glu (mimicking phosphorylation) or Ala-Ala (mimicking non-phosphorylation) hinted at changes in antibiotic production. Here we analyse development, colony morphology, spore resistance, and antibiotic production in FtsZ knockout mutants expressing FtsZ alleles mimicking Ser319 and Ser387 phosphorylation and non-phosphorylation: AA (no phosphorylation), AE, EA (mixed), and EE (double phosphorylation). The FtsZ-eGFP AE, EA and EE alleles were not able to form observable FtsZ-eGFP ladders when they were expressed in the S. coelicolor wild-type strain, whereas the AA allele could form apparently normal eGFP Z-ladders. The FtsZ mutant expressing the FtsZ EE or EA or AE alleles is able to sporulate indicating that the mutant alleles are able to form functional Z-rings leading to sporulation when the wild-type FtsZ gene is absent. The four mutants were pleiotropically affected in colony morphogenesis, antibiotic production, substrate mycelium differentiation and sporulation (sporulation timing and spore resistance) which may be an indirect result of the effect in sporulation Z-ladder formation. Each mutant showed a distinctive phenotype in antibiotic production, single colony morphology, and sporulation (sporulation timing and spore resistance) indicating that the different FtsZ phosphomimetic alleles led to different phenotypes. Taken together, our data provide evidence for a pleiotropic effect of FtsZ phosphorylation in colony morphology, antibiotic production, and sporulation.
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Affiliation(s)
- Paula Yagüe
- grid.5132.50000 0001 2312 1970Department of Molecular Biotechnology, Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 AB Leiden, The Netherlands
| | - Joost Willemse
- grid.5132.50000 0001 2312 1970Department of Molecular Biotechnology, Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 AB Leiden, The Netherlands
| | - Xiansha Xiao
- grid.5132.50000 0001 2312 1970Department of Molecular Biotechnology, Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 AB Leiden, The Netherlands
| | - Le Zhang
- grid.5132.50000 0001 2312 1970Department of Molecular Biotechnology, Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 AB Leiden, The Netherlands
| | - Angel Manteca
- grid.10863.3c0000 0001 2164 6351Departamento de Biología Funcional e IUOPA, Área de Microbiología, Facultad de Medicina, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Gilles P. van Wezel
- grid.5132.50000 0001 2312 1970Department of Molecular Biotechnology, Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 AB Leiden, The Netherlands
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2
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Coltharp C, Xiao J. Beyond force generation: Why is a dynamic ring of FtsZ polymers essential for bacterial cytokinesis? Bioessays 2016; 39:1-11. [PMID: 28004447 DOI: 10.1002/bies.201600179] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We propose that the essential function of the most highly conserved protein in bacterial cytokinesis, FtsZ, is not to generate a mechanical force to drive cell division. Rather, we suggest that FtsZ acts as a signal-processing hub to coordinate cell wall synthesis at the division septum with a diverse array of cellular processes, ensuring that the cell divides smoothly at the correct time and place, and with the correct septum morphology. Here, we explore how the polymerization properties of FtsZ, which have been widely attributed to force generation, can also be advantageous in this signal processing role. We suggest mechanisms by which FtsZ senses and integrates both mechanical and biochemical signals, and conclude by proposing experiments to investigate how FtsZ contributes to the remarkable spatial and temporal precision of bacterial cytokinesis.
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Affiliation(s)
- Carla Coltharp
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Jie Xiao
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA
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3
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Hsu YP, Meng X, VanNieuwenhze M. Methods for visualization of peptidoglycan biosynthesis. METHODS IN MICROBIOLOGY 2016. [DOI: 10.1016/bs.mim.2016.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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4
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White CL, Gober JW. MreB: pilot or passenger of cell wall synthesis? Trends Microbiol 2012; 20:74-9. [DOI: 10.1016/j.tim.2011.11.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 11/07/2011] [Accepted: 11/10/2011] [Indexed: 01/08/2023]
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5
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Schmidt M, Creutziger M, Lenz P. Influence of molecular noise on the growth of single cells and bacterial populations. PLoS One 2012; 7:e29932. [PMID: 22238678 PMCID: PMC3253122 DOI: 10.1371/journal.pone.0029932] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 12/07/2011] [Indexed: 12/02/2022] Open
Abstract
During the last decades experimental studies have revealed that single cells of a growing bacterial population are significantly exposed to molecular noise. Important sources for noise are low levels of metabolites and enzymes that cause significant statistical variations in the outcome of biochemical reactions. In this way molecular noise affects biological processes such as nutrient uptake, chemotactic tumbling behavior, or gene expression of genetically identical cells. These processes give rise to significant cell-to-cell variations of many directly observable quantities such as protein levels, cell sizes or individual doubling times. In this study we theoretically explore if there are evolutionary benefits of noise for a growing population of bacteria. We analyze different situations where noise is either suppressed or where it affects single cell behavior. We consider two specific examples that have been experimentally observed in wild-type Escherichia coli cells: (i) the precision of division site placement (at which molecular noise is highly suppressed) and (ii) the occurrence of noise-induced phenotypic variations in fluctuating environments. Surprisingly, our analysis reveals that in these specific situations both regulatory schemes [i.e. suppression of noise in example (i) and allowance of noise in example (ii)] do not lead to an increased growth rate of the population. Assuming that the observed regulatory schemes are indeed caused by the presence of noise our findings indicate that the evolutionary benefits of noise are more subtle than a simple growth advantage for a bacterial population in nutrient rich conditions.
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Affiliation(s)
- Mischa Schmidt
- Fachbereich Physik, Philipps-Universität Marburg, Marburg, Germany
| | | | - Peter Lenz
- Fachbereich Physik, Philipps-Universität Marburg, Marburg, Germany
- Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Marburg, Germany
- * E-mail:
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6
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Jiang H, Si F, Margolin W, Sun SX. Mechanical control of bacterial cell shape. Biophys J 2011; 101:327-35. [PMID: 21767484 DOI: 10.1016/j.bpj.2011.06.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 05/29/2011] [Accepted: 06/01/2011] [Indexed: 01/31/2023] Open
Abstract
In bacteria, cytoskeletal filament bundles such as MreB control the cell morphology and determine whether the cell takes on a spherical or a rod-like shape. Here we use a theoretical model to describe the interplay of cell wall growth, mechanics, and cytoskeletal filaments in shaping the bacterial cell. We predict that growing cells without MreB exhibit an instability that favors rounded cells. MreB can mechanically reinforce the cell wall and prevent the onset of instability. We propose that the overall bacterial shape is determined by a dynamic turnover of cell wall material that is controlled by mechanical stresses in the wall. The model affirms that morphological transformations with and without MreB are reversible, and quantitatively describes the growth of irregular shapes and cells undergoing division. The theory also suggests a unique coupling between mechanics and chemistry that can control organismal shapes in general.
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Affiliation(s)
- Hongyuan Jiang
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, USA
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7
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The composition and organization of cytoplasm in prebiotic cells. Int J Mol Sci 2011; 12:1650-9. [PMID: 21673913 PMCID: PMC3111624 DOI: 10.3390/ijms12031650] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Revised: 02/15/2011] [Accepted: 02/23/2011] [Indexed: 11/17/2022] Open
Abstract
This article discusses the hypothesized composition and organization of cytoplasm in prebiotic cells from a theoretical perspective and also based upon what is currently known about bacterial cytoplasm. It is unknown if the first prebiotic, microscopic scale, cytoplasm was initially contained within a primitive, continuous, semipermeable membrane, or was an uncontained gel substance, that later became enclosed by a continuous membrane. Another possibility is that the first cytoplasm in prebiotic cells and a primitive membrane organized at the same time, permitting a rapid transition to the first cell(s) capable of growth and division, thus assisting with the emergence of life on Earth less than a billion years after the formation of the Earth. It is hypothesized that the organization and composition of cytoplasm progressed initially from an unstructured, microscopic hydrogel to a more complex cytoplasm, that may have been in the volume magnitude of about 0.1-0.2 μm(3) (possibly less if a nanocell) prior to the first cell division.
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8
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Jiang H, Sun SX. Morphology, growth, and size limit of bacterial cells. PHYSICAL REVIEW LETTERS 2010; 105:028101. [PMID: 20867742 PMCID: PMC3633209 DOI: 10.1103/physrevlett.105.028101] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Indexed: 05/20/2023]
Abstract
Bacterial cells utilize a living peptidoglycan network (PG) to separate the cell interior from the surroundings. The shape of the cell is controlled by PG synthesis and cytoskeletal proteins that form bundles and filaments underneath the cell wall. The PG layer also resists turgor pressure and protects the cell from osmotic shock. We argue that mechanical influences alter the chemical equilibrium of the reversible PG assembly and determine the cell shape and cell size. Using a mechanochemical approach, we show that the cell shape can be regarded as a steady state of a growing network under the influence of turgor pressure and mechanical stress. Using simple elastic models, we predict the size of common spherical and rodlike bacteria. The influence of cytoskeletal bundles such as crescentin and MreB are discussed within the context of our model.
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Affiliation(s)
- Hongyuan Jiang
- Department of Mechanical Engineering and Whitaker Biomedical Engineering Institute, Johns Hopkins University, Baltimore, Maryland 21218, USA
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9
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Abstract
Prokaryotes come in a wide variety of shapes, determined largely by natural selection, physical constraints, and patterns of cell growth and division. Because of their relative simplicity, bacterial cells are excellent models for how genes and proteins can directly determine morphology. Recent advances in cytological methods for bacteria have shown that distinct cytoskeletal filaments composed of actin and tubulin homologs are important for guiding growth patterns of the cell wall in bacteria, and that the glycan strands that constitute the wall are generally perpendicular to the direction of growth. This cytoskeleton-directed cell wall patterning is strikingly reminiscent of how plant cell wall growth is regulated by microtubules. In rod-shaped bacilli, helical cables of actin-like MreB protein stretch along the cell length and orchestrate elongation of the cell wall, whereas the tubulin-like FtsZ protein directs formation of the division septum and the resulting cell poles. The overlap and interplay between these two systems and the peptidoglycan-synthesizing enzymes they recruit are the major driving forces of cylindrical shapes. Round cocci, on the other hand, have lost their MreB cables and instead must grow mainly via their division septum, giving them their characteristic round or ovoid shapes. Other bacteria that lack MreB homologs or even cell walls use distinct cytoskeletal systems to maintain their distinct shapes. Here I review what is known about the mechanisms that determine the shape of prokaryotic cells.
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Affiliation(s)
- William Margolin
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin Street, Houston, TX 77030, USA.
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10
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Oehler S, Müller-Hill B. High local concentration: a fundamental strategy of life. J Mol Biol 2009; 395:242-53. [PMID: 19883663 DOI: 10.1016/j.jmb.2009.10.056] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 10/22/2009] [Accepted: 10/27/2009] [Indexed: 12/26/2022]
Abstract
Local increase in concentration is a basic principle of transcriptional control. Closer inspection reveals that it is a major force governing all interactions within and between proteins and DNA. Local increase in concentration acts on all levels of organization of living matter. The structures and functions of two central molecules of life-the linear polymers DNA and protein-are particularly illuminating examples. Local increase in concentration leads to cooperative or competitive interactions between molecules. It is an important principle of life.
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Affiliation(s)
- Stefan Oehler
- Biomedical Sciences Research Center Alexander Fleming, 34 Fleming Street, GR-16672 Vari, Greece.
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11
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Costa T, Priyadarshini R, Jacobs-Wagner C. Localization of PBP3 in Caulobacter crescentus is highly dynamic and largely relies on its functional transpeptidase domain. Mol Microbiol 2008; 70:634-51. [PMID: 18786147 DOI: 10.1111/j.1365-2958.2008.06432.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In rod-shaped bacteria, septal peptidoglycan synthesis involves the late recruitment of the ftsI gene product (PBP3 in Escherichia coli) to the FtsZ ring. We show that in Caulobacter crescentus, PBP3 accumulates at the new pole at the beginning of the cell cycle. Fluorescence recovery after photobleaching experiments reveal that polar PBP3 molecules are, constantly and independently of FtsZ, replaced by those present in the cellular pool, implying that polar PBP3 is not a remnant of the previous division. By the time cell constriction is initiated, all PBP3 polar accumulation has disappeared in favour of an FtsZ-dependent localization near midcell, consistent with PBP3 function in cell division. Kymograph analysis of time-lapse experiments shows that the recruitment of PBP3 to the FtsZ ring is progressive and initiated very early on, shortly after FtsZ ring formation and well before cell constriction starts. Accumulation of PBP3 near midcell is also highly dynamic with a rapid exchange of PBP3 molecules between midcell and cellular pools. Localization of PBP3 at both midcell and pole appears multifactorial, primarily requiring the catalytic site of PBP3. Collectively, our results suggest a role for PBP3 in pole morphogenesis and provide new insights into the process of peptidoglycan assembly during division.
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Affiliation(s)
- Teresa Costa
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
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12
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Layec S, Decaris B, Leblond-Bourget N. Diversity of Firmicutes peptidoglycan hydrolases and specificities of those involved in daughter cell separation. Res Microbiol 2008; 159:507-15. [PMID: 18656532 DOI: 10.1016/j.resmic.2008.06.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Revised: 06/04/2008] [Accepted: 06/10/2008] [Indexed: 11/29/2022]
Abstract
Within Streptococcus thermophilus, Cse was identified as the major cell disconnecting peptidoglycan hydrolase (PGH) and was demonstrated to be species-specific. To identify cell disconnecting PGHs encoded by other Streptococcus genomes, we explored the diversity of domains carried by Firmicutes PGHs, and especially that of enzymes involved in daughter cell separation. This work brings to light the diversity of PGHs and reveals that each species recruits its own cell-separating enzyme distinct from that of the others. This specificity is probably correlated with the diversity of substrates found in the bacterial cell wall.
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Affiliation(s)
- Séverine Layec
- Laboratoire de Génétique et Microbiologie, UMR INRA/UHP 1128, IFR 110, Faculté des Sciences et Techniques, Nancy-Université, BP 239, 54506 Vandoeuvre-lès-Nancy, France
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13
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Cell shape determination in Escherichia coli. Curr Opin Microbiol 2007; 10:606-10. [DOI: 10.1016/j.mib.2007.09.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Accepted: 09/05/2007] [Indexed: 11/19/2022]
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14
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Harold FM. Bacterial morphogenesis: learning how cells make cells. Curr Opin Microbiol 2007; 10:591-5. [PMID: 17703990 DOI: 10.1016/j.mib.2007.07.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Accepted: 07/02/2007] [Indexed: 11/21/2022]
Abstract
Bacteria furnish tractable models for complex biological processes, and morphogenesis is now taking its turn. We can already explain in general terms how such elementary forms as rods and cocci are produced, and the shapes of several individual organisms are coming into focus. In most bacteria shape is maintained by the cell wall, specifically the peptidoglycan layer, which has the attributes of a strong stiff fabric. Compliance of that fabric with turgor pressure is an important aspect of morphogenesis. The shape of the wall sacculus is determined by the way it is deposited, which is controlled by a cytoskeleton made up of two molecular families. One, related to the eukaryotic tubulins, is responsible for the construction of the septum and the poles. The other, related to eukaryotic actins, localizes peptidoglycan synthesis in the lateral walls of rod-shaped cells. Just how the cytoskeleton itself is organized remains to be discovered, but it seems likely that, as in eukaryotes, the cytoskeleton is produced by self-organized assembly, guided by the fabric of the cell.
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Affiliation(s)
- Franklin M Harold
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
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15
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Koch AL, De Pedro MA. Partition of Old Murein in Small Patches over the Entire Wall of E. coli Cells Forced to Grow as a Coccoid. Curr Microbiol 2006; 52:249-53. [PMID: 16550459 DOI: 10.1007/s00284-005-4548-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2005] [Accepted: 09/15/2005] [Indexed: 10/24/2022]
Abstract
With the development of a technique to visualize the ages of different portions of the sacculus, De Pedro et al. showed that the sacculus of Escherichia coli was tripartite: (i) the establish poles contained only old wall, (ii) the nascent poles (or septa) were composed entirely of new murein, and (iii) the elongating cylindrical wall was a mixture of patches of both old and new peptidoglycan. This short note presents a computer analysis of data files of work presented in the recent paper by De Pedro et al. of the growth pattern of the wall of E. coli forced to grow in a quite unusual morphology as large spheres in the presence of mecillinam. Compared with rod-shaped cells, only very small patches (spikes) of old wall were retained interspersed with new murein during the conversion to large spheroids. This subdivision appeared to be the case for both the previous wall of the poles, which are ordinarily retained intact, and the previous patches retained within the cylindrical wall. These very small patches after the conversion to spheroids were much smaller than the sidewall patches in rod-shaped cells reported previously. This implies that the mechanism that prevents the insertion of new wall into both the wall of the poles and the old wall patches of the sidewall in the presence of mecillinam is superseded by insertion throughout the old wall. The work in the De Pedro et al. paper from 2001 was done with cells of same strain as in the earlier papers with rod-shaped cells, so the results of computer analysis of the fluorescence micrographs can be critically compared.
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Affiliation(s)
- Arthur L Koch
- Biology Department, Indiana University, 1001 East Third Street, Bloomington, Indiana, 47405-6801, USA.
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16
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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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17
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Abstract
A living cell is not an aggregate of molecules but an organized pattern, structured in space and in time. This article addresses some conceptual issues in the genesis of spatial architecture, including how molecules find their proper location in cell space, the origins of supramolecular order, the role of the genes, cell morphology, the continuity of cells, and the inheritance of order. The discussion is framed around a hierarchy of physiological processes that bridge the gap between nanometer-sized molecules and cells three to six orders of magnitude larger. Stepping stones include molecular self-organization, directional physiology, spatial markers, gradients, fields, and physical forces. The knowledge at hand leads to an unconventional interpretation of biological order. I have come to think of cells as self-organized systems composed of genetically specified elements plus heritable structures. The smallest self that can be fairly said to organize itself is the whole cell. If structure, form, and function are ever to be computed from data at a lower level, the starting point will be not the genome, but a spatially organized system of molecules. This conclusion invites us to reconsider our understanding of what genes do, what organisms are, and how living systems could have arisen on the early Earth.
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Affiliation(s)
- Franklin M Harold
- Department of Microbiology, University of Washington, Seattle 98195, USA.
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18
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Abstract
The motility of some kinds of bacteria depends on their spiral form, as does the virulence of certain pathogenic species. We propose a novel mechanism for the development of spiral shape in bacteria and the supercoiling of chains ('filaments') of many cells. Recently discovered actin-like proteins lying just under the cell wall form fibers that play a role in maintaining cell shape. Some species have a single actin-like fiber helically wrapped around the cell, while others have two fibers wrapped in the same direction. Here, we show that if these fibers elongate more slowly than growth lengthens the cell, the cell both twists and bends, taking on a spiral shape. We tested this mechanism using a mathematical model of expanding fiber-wound structures and via experiments that measure the shape changes of elongating physical models. Comparison of the model with in vivo experiments on stationary phase Caulobacter crescentus filaments provide the first evidence that mechanical stretching of cytoskeletal fibers influences cell morphology. Any hydraulic cylinder can spiral by this mechanism if it is reinforced by stretch-resistant fibers wrapped helically in the same direction, or shortened by contractile elements. This might be useful in the design of man-made actuators.
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Affiliation(s)
- Charles W Wolgemuth
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030-3505, USA
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19
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Kuo MMC, Haynes WJ, Loukin SH, Kung C, Saimi Y. Prokaryotic K(+) channels: from crystal structures to diversity. FEMS Microbiol Rev 2005; 29:961-85. [PMID: 16026885 DOI: 10.1016/j.femsre.2005.03.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2004] [Revised: 03/21/2005] [Accepted: 03/23/2005] [Indexed: 10/25/2022] Open
Abstract
The deep roots and wide branches of the K(+)-channel family are evident from genome surveys and laboratory experimentation. K(+)-channel genes are widespread and found in nearly all the free-living bacteria, archaea and eukarya. The conservation of basic structures and mechanisms such as the K(+) filter, the gate, and some of the gate's regulatory domains have allowed general insights on animal K(+) channels to be gained from crystal structures of prokaryotic channels. Since microbes are the great majority of life's diversity, it is not surprising that microbial genomes reveal structural motifs beyond those found in animals. There are open-reading frames that encode K(+)-channel subunits with unconventional filter sequences, or regulatory domains of different sizes and numbers not previously known. Parasitic or symbiotic bacteria tend not to have K(+) channels, while those showing lifestyle versatility often have more than one K(+)-channel gene. It is speculated that prokaryotic K(+) channels function to allow adaptation to environmental and metabolic changes, although the actual roles of these channels in prokaryotes are not yet known. Unlike enzymes in basic metabolism, K(+) channel, though evolved early, appear to play more diverse roles than revealed by animal research. Finding and sorting out these roles will be the goal and challenge of the near future.
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Affiliation(s)
- Mario M-C Kuo
- Laboratory of Molecular Biology, University of Wisconsin, 1525 Linden Drive, Madison, WI 53706, USA
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20
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Covert MW, Famili I, Palsson BO. Identifying constraints that govern cell behavior: a key to converting conceptual to computational models in biology? Biotechnol Bioeng 2004; 84:763-72. [PMID: 14708117 DOI: 10.1002/bit.10849] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Cells must abide by a number of constraints. The environmental constrains of cellular behavior and physicochemical limitations affect cellular processes. To regulate and adapt their functions, cells impose constraints on themselves. Enumerating, understanding, and applying these constraints leads to a constraints-based modeling formalism that has been helpful in converting conceptual models to computational models in biology. The continued success of the constraints-based approach depends upon identification and incorporation of new constraints to more accurately define cellular capabilities. This review considers constraints in terms of environmental, physicochemical, and self-imposed regulatory and evolutionary constraints with the purpose of refining current constraints-based models of cell phenotype.
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Affiliation(s)
- Markus W Covert
- Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
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21
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Touhami A, Jericho MH, Beveridge TJ. Atomic force microscopy of cell growth and division in Staphylococcus aureus. J Bacteriol 2004; 186:3286-95. [PMID: 15150213 PMCID: PMC415778 DOI: 10.1128/jb.186.11.3286-3295.2004] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The growth and division of Staphylococcus aureus was monitored by atomic force microscopy (AFM) and thin-section transmission electron microscopy (TEM). A good correlation of the structural events of division was found using the two microscopies, and AFM was able to provide new additional information. AFM was performed under water, ensuring that all structures were in the hydrated condition. Sequential images on the same structure revealed progressive changes to surfaces, suggesting the cells were growing while images were being taken. Using AFM small depressions were seen around the septal annulus at the onset of division that could be attributed to so-called murosomes (Giesbrecht et al., Arch. Microbiol. 141:315-324, 1985). The new cell wall formed from the cross wall (i.e., completed septum) after cell separation and possessed concentric surface rings and a central depression; these structures could be correlated to a midline of reactive material in the developing septum that was seen by TEM. The older wall, that which was not derived from a newly formed cross wall, was partitioned into two different surface zones, smooth and gel-like zones, with different adhesive properties that could be attributed to cell wall turnover. The new and old wall topographies are equated to possible peptidoglycan arrangements, but no conclusion can be made regarding the planar or scaffolding models.
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Affiliation(s)
- Ahmed Touhami
- Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 3J5
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Abstract
Members of the actin-like MreB family of proteins localize as a helical filament in bacteria and are important for determining cylindrical cell shape. Recent results show that new cell wall biosynthesis occurs along a helical track dependent on one of these actin homologs, providing new insights into bacterial cell growth, division and shape.
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Affiliation(s)
- William Margolin
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, 6431 Fannin, Houston, TX 77030, USA.
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De Pedro MA, Schwarz H, Koch AL. Patchiness of murein insertion into the sidewall of Escherichia coli. MICROBIOLOGY (READING, ENGLAND) 2003; 149:1753-1761. [PMID: 12855727 DOI: 10.1099/mic.0.26125-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This paper extends, with computer techniques, the authors' previous work on the kinetics of pole wall and sidewall synthesis in Escherichia coli. These findings extend the conclusion that the nascent poles are made of entirely new material and that no new material is inserted into old poles. This requires re-evaluation of ideas in the literature about wall growth and cell division. Mechanisms of various types have been suggested for the growth of Gram-negative rod-shaped bacteria and these will also require major re-evaluation because of the finding, reported here, that the sidewall is made in several modes: patches of new murein, bands of new material largely going circumferentially around the cell, and areas of the sidewall that are enlarged by an intimate and regular admixture of new with the old muropeptides.
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Affiliation(s)
- Miguel A De Pedro
- Centro de Biologia Molecular 'Severo Ochoa', Consejo Superior de Investigaciones Cientificas-Universidad Autónoma de Madrid, Facultad de Ciencias, 28049 Madrid, Spain
| | - Heinz Schwarz
- Max-Planck-Institut für Entwicklungsbiologie, 72076 Tübingen, Germany
| | - Arthur L Koch
- Biology Department, Indiana University, Bloomington, IN 47405-6801, USA
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Daniel RA, Errington J. Control of cell morphogenesis in bacteria: two distinct ways to make a rod-shaped cell. Cell 2003; 113:767-76. [PMID: 12809607 DOI: 10.1016/s0092-8674(03)00421-5] [Citation(s) in RCA: 590] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Cell shape in most eubacteria is maintained by a tough external peptidoglycan cell wall. Recently, cell shape determining proteins of the MreB family were shown to form helical, actin-like cables in the cell. We used a fluorescent derivative of the antibiotic vancomycin as a probe for nascent peptidoglycan synthesis in unfixed cells of various Gram-positive bacteria. In the rod-shaped bacterium B. subtilis, synthesis of the cylindrical part of the cell wall occurs in a helical pattern governed by an MreB homolog, Mbl. However, a few rod-shaped bacteria have no MreB system. Here, a rod-like shape can be achieved by a completely different mechanism based on use of polar growth zones derived from the division machinery. These results provide insights into the diverse molecular strategies used by bacteria to control their cellular morphology, as well as suggesting ways in which these strategies may impact on growth rates and cell envelope structure.
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Affiliation(s)
- Richard A Daniel
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, United Kingdom
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25
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Abstract
In the turgid cells of plants, protists, fungi, and bacteria, walls resist swelling; they also confer shape on the cell. These two functions are not unrelated: cell physiologists have generally agreed that morphogenesis turns on the deformation of existing wall and the deposition of new wall, while turgor pressure produces the work of expansion. In 1990, I summed up consensus in a phrase: "localized compliance with the global force of turgor pressure." My purpose here is to survey the impact of recent discoveries on the traditional conceptual framework. Topics include the recognition of a cytoskeleton in bacteria; the tide of information and insight about budding in yeast; the role of the Spitzenkörper in hyphal extension; calcium ions and actin dynamics in shaping a tip; and the interplay of protons, expansins and cellulose fibrils in cells of higher plants.
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Affiliation(s)
- Franklin M Harold
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
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Abstract
Generally speaking, bacteria grow and divide indefinitely, and as long as the growth conditions are maintained they retain constant dimensions and shapes with little variation. How they do this is a question that I have been considering for three decades. Here, I discuss two hypothetical mechanisms, one for Gram-positive rods and the other for Gram-negative rods. These mechanisms are consistent with what is known, but make some unproven assumptions.
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Affiliation(s)
- Arthur L Koch
- Biology Dept, Indiana University, Bloomington, IN 47405-6801, USA.
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Affiliation(s)
- Martin A Line
- School of Agricultural Science, University of Tasmania, Hobart, Tasmania 7001, Australia1
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Affiliation(s)
- A L Koch
- Department of Biology, Indiana University, 1001 E. Third St., Bloomington, IN 47405-6801, USA.
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