551
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Shum H, Gaffney EA, Smith DJ. Modelling bacterial behaviour close to a no-slip plane boundary: the influence of bacterial geometry. Proc Math Phys Eng Sci 2010. [DOI: 10.1098/rspa.2009.0520] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We describe a boundary-element method used to model the hydrodynamics of a bacterium propelled by a single helical flagellum. Using this model, we optimize the power efficiency of swimming with respect to cell body and flagellum geometrical parameters, and find that optima for swimming in unbounded fluid and near a no-slip plane boundary are nearly indistinguishable. We also consider the novel optimization objective of torque efficiency and find a very different optimal shape. Excluding effects such as Brownian motion and electrostatic interactions, it is demonstrated that hydrodynamic forces may trap the bacterium in a stable, circular orbit near the boundary, leading to the empirically observable surface accumulation of bacteria. Furthermore, the details and even the existence of this stable orbit depend on geometrical parameters of the bacterium, as described in this article. These results shed some light on the phenomenon of surface accumulation of micro-organisms and offer hydrodynamic explanations as to why some bacteria may accumulate more readily than others based on morphology.
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Affiliation(s)
- H. Shum
- Mathematical Institute, University of Oxford, 24-29 St Giles’, Oxford OX1 3LB, UK
| | - E. A. Gaffney
- Mathematical Institute, University of Oxford, 24-29 St Giles’, Oxford OX1 3LB, UK
- Centre for Human Reproductive Science, Birmingham Women’s National Health Service Foundation Trust, Metchley Park Road, Edgbaston, Birmingham B15 2TG, UK
| | - D. J. Smith
- Centre for Human Reproductive Science, Birmingham Women’s National Health Service Foundation Trust, Metchley Park Road, Edgbaston, Birmingham B15 2TG, UK
- School of Mathematics and School of Clinical and Experimental Medicine, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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552
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Mazumder S, Falkinham JO, Dietrich AM, Puri IK. Role of hydrophobicity in bacterial adherence to carbon nanostructures and biofilm formation. BIOFOULING 2010; 26:333-339. [PMID: 20087805 DOI: 10.1080/08927010903531491] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The role of cell and surface hydrophobicity in the adherence of the waterborne bacterium Mycobacterium smegmatis to nanostructures and biofilm formation was investigated. Carbon nanostructures (CNs) were synthesized using a flame reactor and deposited on stainless steel grids and foils, and on silicon wafers that had different initial surface hydrophobicities. Surface hydrophobicity was measured as the contact angle of water droplets. The surfaces were incubated in suspensions of isogenic hydrophobic and hydrophilic strains of M. smegmatis and temporal measurements of the numbers of adherent cells were made. The hydrophobic, rough mutant of M. smegmatis adhered more readily and formed denser biofilms on all surfaces compared to its hydrophilic, smooth parent. Biofilm formation led to alterations in the hydrophobicity of the substratum surfaces, demonstrating that bacterial cells attached to CNs are capable of modifying the surface characteristics.
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Affiliation(s)
- Sonal Mazumder
- Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
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553
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Shchepelina O, Kozlovskaya V, Singamaneni S, Kharlampieva E, Tsukruk VV. Replication of anisotropic dispersed particulates and complex continuous templates. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/c0jm00049c] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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554
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MreB drives de novo rod morphogenesis in Caulobacter crescentus via remodeling of the cell wall. J Bacteriol 2009; 192:1671-84. [PMID: 20023035 DOI: 10.1128/jb.01311-09] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
MreB, the bacterial actin-like cytoskeleton, is required for the rod morphology of many bacterial species. Disruption of MreB function results in loss of rod morphology and cell rounding. Here, we show that the widely used MreB inhibitor A22 causes MreB-independent growth inhibition that varies with the drug concentration, culture medium conditions, and bacterial species tested. MP265, an A22 structural analog, is less toxic than A22 for growth yet equally efficient for disrupting the MreB cytoskeleton. The action of A22 and MP265 is enhanced by basic pH of the culture medium. Using this knowledge and the rapid reversibility of drug action, we examined the restoration of rod shape in lemon-shaped Caulobacter crescentus cells pretreated with MP265 or A22 under nontoxic conditions. We found that reversible restoration of MreB function after drug removal causes extensive morphological changes including a remarkable cell thinning accompanied with elongation, cell branching, and shedding of outer membrane vesicles. We also thoroughly characterized the composition of C. crescentus peptidoglycan by high-performance liquid chromatography and mass spectrometry and showed that MreB disruption and recovery of rod shape following restoration of MreB function are accompanied by considerable changes in composition. Our results provide insight into MreB function in peptidoglycan remodeling and rod shape morphogenesis and suggest that MreB promotes the transglycosylase activity of penicillin-binding proteins.
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555
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Mukhopadhyay R, Wingreen NS. Curvature and shape determination of growing bacteria. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:062901. [PMID: 20365209 PMCID: PMC2873841 DOI: 10.1103/physreve.80.062901] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 09/29/2009] [Indexed: 05/20/2023]
Abstract
Bacterial cells come in a variety of shapes, determined by the stress-bearing cell wall. Though many molecular details about the cell wall are known, our understanding of how a particular shape is produced during cell growth is at its infancy. Experiments on curved Escherichia coli grown in microtraps, and on naturally curved Caulobacter crescentus, reveal different modes of growth: one preserving arc length and the other preserving radius of curvature. We present a simple model for curved cell growth that relates these two growth modes to distinct but related growth rules--"hooplike growth" and "self-similar growth"--and discuss the implications for microscopic growth mechanisms.
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Affiliation(s)
- Ranjan Mukhopadhyay
- Department of Physics, Clark University, Worcester, Massachusetts 01610, USA
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556
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Protistan predation affects trichloroethene biodegradation in a bedrock aquifer. Appl Environ Microbiol 2009; 75:7588-93. [PMID: 19820148 DOI: 10.1128/aem.01820-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Despite extensive research on the bottom-up force of resource availability (e.g., electron donors and acceptors), slow biodegradation rates and stalling at cis-dichloroethene (cDCE) and vinyl chloride continue to be observed in aquifers contaminated with trichloroethene (TCE). The objective of this research was to gauge the impact of the top-down force of protistan predation on TCE biodegradation in laboratory microcosms. When indigenous bacteria from an electron donor-limited TCE-contaminated bedrock aquifer were present, the indigenous protists inhibited reductive dechlorination altogether. The presence of protists during organic carbon-amended conditions caused the bacteria to elongate (length:width, > or =10:1), but reductive dechlorination was still inhibited. When a commercially available dechlorinating bacterial culture and an organic carbon amendment were added in he presence of protists, the elongated bacteria predominated and reductive dechlorination stalled at cDCE. When protists were removed under organic carbon-amended conditions, reductive dechlorination stalled at cDCE, whereas in the presence organic carbon and bacterial amendments, the total chlorinated ethene concentration decreased, indicating TCE was converted to ethene and/or CO2. The data suggested that indigenous protists grazed dechlorinators to extremely low levels, inhibiting dechlorination altogether. Hence, in situ bioremediation/bioaugmentation may not be successful in mineralizing TCE unless the top-down force of protistan predation is inhibited.
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557
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Goncharenko AV, Chang YC. Effective dielectric properties of biological cells: generalization of the spectral density function approach. J Phys Chem B 2009; 113:9924-31. [PMID: 19569640 DOI: 10.1021/jp900703a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We suggest an extension of the spectral density function approach to describe the complex dielectric response of suspensions of arbitrarily shaped particles having a thin shell, in particular, biological cells. The approach is shown to give analytical results in some simple but practically important cases. In the general case, for the 3-phase systems it reduces to determination of the spectral density function for the suspension of a certain kind. Prospects and limitations of the approach, as well as practical examples, are also considered.
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Affiliation(s)
- Anatoliy V Goncharenko
- Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei 115, Taiwan, ROC.
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558
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Abstract
Simple visual inspection of bacteria indicated that, at least in some otherwise symmetric cells, structures such as flagella were often seen at a single pole. Because these structures are composed of proteins, it was not clear how to reconcile these observations of morphological asymmetry with the widely held view of bacteria as unstructured "bags of enzymes." However, over the last decade, numerous GFP tagged proteins have been found at specific intracellular locations such as the poles of the cells, indicating that bacteria have a high degree of intracellular organization. Here we will explore the role of chromosomal asymmetry and the presence of "new" and "old" poles that result from the cytokinesis of rod-shaped cells in establishing bipolar and monopolar protein localization patterns. This article is intended to be illustrative, not exhaustive, so we have focused on examples drawn largely from Caulobacter crescentus and Bacillus subtilis, two bacteria that undergo dramatic morphological transformation. We will highlight how breaking monopolar symmetry is essential for the correct development of these organisms.
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Affiliation(s)
- Jonathan Dworkin
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York 10032, USA.
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559
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Dynes JJ, Lawrence JR, Korber DR, Swerhone GDW, Leppard GG, Hitchcock AP. Morphological and biochemical changes in Pseudomonas fluorescens biofilms induced by sub-inhibitory exposure to antimicrobial agents. Can J Microbiol 2009; 55:163-78. [PMID: 19295649 DOI: 10.1139/w08-109] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Confocal laser scanning microscopy (CLSM) and scanning transmission X-ray microscopy (STXM) were used to examine the morphological and biochemical changes in Pseudomonas fluorescens biofilms grown in the presence of subinhibitory concentrations of 4 antimicrobial agents: triclosan, benzalkonium chloride, chlorhexidine dihydrochloride, and trisodium phosphate. CLSM analyses using the stains SYTO9 and propidium iodide indicated that the antimicrobial agents affected cell membrane integrity and cellular density to differing degrees. However, fluorescein diacetate assays and plate counts demonstrated that the cells remained metabolically active. Fluorescent lectin binding assays showed that changes in the arrangement and composition of the exopolymer matrix of the biofilms also occurred and that these changes depended on the antimicrobial agent. Detailed single cell analyses using STXM provided evidence that the cell morphology, and the spatial distribution and relative amounts of protein, lipids and polysaccharides in the biofilms and within the cells were different for each antimicrobial. The distribution of chlorhexidine in the biofilm, determined from its distinct spectral signature, was localized mainly inside the bacterial cells. Each antimicrobial agent elicited a unique response; P. fluorescens cells and biofilms changed their morphology and architecture, as well as the distribution and abundance of biomacromolecules, in particular the exopolymer matrix. Pseudomonas fluorescens also exhibited adaptation to benzalkonium chloride at 10 microg/mL. Our observations point to the importance of changes in the quantity and chemistry of the exopolymeric matrix in the response to antimicrobial agents and suggest their importance as targets for control.
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Affiliation(s)
- James J Dynes
- Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON-L8S-4M1, Canada
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560
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Stecchini M, Spaziani M, Torre MD, Pacor S. Bacillus cereuscell and spore properties as influenced by the micro-structure of the medium. J Appl Microbiol 2009; 106:1838-48. [DOI: 10.1111/j.1365-2672.2009.04162.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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561
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Locsei JT, Pedley TJ. Run and tumble chemotaxis in a shear flow: the effect of temporal comparisons, persistence, rotational diffusion, and cell shape. Bull Math Biol 2009; 71:1089-116. [PMID: 19198954 DOI: 10.1007/s11538-009-9395-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Accepted: 01/07/2009] [Indexed: 10/21/2022]
Abstract
Escherichia coli is a motile bacterium that moves up a chemoattractant gradient by performing a biased random walk composed of alternating runs and tumbles. This paper presents calculations of the chemotactic drift velocity v (d) (the mean velocity up the chemoattractant gradient) of an E. coli cell performing chemotaxis in a uniform, steady shear flow, with a weak chemoattractant gradient at right angles to the flow. Extending earlier models, a combined analytic and numerical approach is used to assess the effect of several complications, namely (i) a cell cannot detect a chemoattractant gradient directly but rather makes temporal comparisons of chemoattractant concentration, (ii) the tumbles exhibit persistence of direction, meaning that the swimming directions before and after a tumble are correlated, (iii) the cell suffers random re-orientations due to rotational Brownian motion, and (iv) the non-spherical shape of the cell affects the way that it is rotated by the shear flow. These complications influence the dependence of v(d) on the shear rate gamma. When they are all included, it is found that (a) shear disrupts chemotaxis and shear rates beyond gamma approximately 2 s(-1) render chemotaxis ineffective, (b) in terms of maximizing drift velocity, persistence of direction is advantageous in a quiescent fluid but disadvantageous in a shear flow, and (c) a more elongated body shape is advantageous in performing chemotaxis in a shear flow.
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Affiliation(s)
- J T Locsei
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 9EW, UK.
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562
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563
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Three-dimensional macromolecular organization of cryofixed Myxococcus xanthus biofilms as revealed by electron microscopic tomography. J Bacteriol 2009; 191:2077-82. [PMID: 19168614 DOI: 10.1128/jb.01333-08] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Despite the fact that most bacteria grow in biofilms in natural and pathogenic ecosystems, very little is known about the ultrastructure of their component cells or about the details of their community architecture. We used high-pressure freezing and freeze-substitution to minimize the artifacts of chemical fixation, sample aggregation, and sample extraction. As a further innovation we have, for the first time in biofilm research, used electron tomography and three-dimensional (3D) visualization to better resolve the macromolecular 3D ultrastructure of a biofilm. This combination of superb specimen preparation and greatly improved resolution in the z axis has opened a window in studies of Myxococcus xanthus cell ultrastructure and biofilm community architecture. New structural information on the chromatin body, cytoplasmic organization, membrane apposition between adjacent cells, and structure and distribution of pili and vesicles in the biofilm matrix is presented.
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564
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Newby DT, Pepper IL, Maier RM. Microbial Transport. Environ Microbiol 2009. [DOI: 10.1016/b978-0-12-370519-8.00019-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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565
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Abstract
The development of biomaterials for drug delivery, tissue engineering and medical diagnostics has traditionally been based on new chemistries. However, there is growing recognition that the physical as well as the chemical properties of materials can regulate biological responses. Here, we review this transition with regard to selected physical properties including size, shape, mechanical properties, surface texture and compartmentalization. In each case, we present examples demonstrating the significance of these properties in biology. We also discuss synthesis methods and biological applications for designer biomaterials, which offer unique physical properties.
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Affiliation(s)
- Samir Mitragotri
- Department of Chemical Engineering, University of California Santa Barbara, California 93106, USA.
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566
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Complex regulatory pathways coordinate cell-cycle progression and development in Caulobacter crescentus. Adv Microb Physiol 2008; 54:1-101. [PMID: 18929067 DOI: 10.1016/s0065-2911(08)00001-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Caulobacter crescentus has become the predominant bacterial model system to study the regulation of cell-cycle progression. Stage-specific processes such as chromosome replication and segregation, and cell division are coordinated with the development of four polar structures: the flagellum, pili, stalk, and holdfast. The production, activation, localization, and proteolysis of specific regulatory proteins at precise times during the cell cycle culminate in the ability of the cell to produce two physiologically distinct daughter cells. We examine the recent advances that have enhanced our understanding of the mechanisms of temporal and spatial regulation that occur during cell-cycle progression.
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567
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Abstract
In bacterial cells, the peptidoglycan cell wall is the stress-bearing structure that dictates cell shape. Although many molecular details of the composition and assembly of cell-wall components are known, how the network of peptidoglycan subunits is organized to give the cell shape during normal growth and how it is reorganized in response to damage or environmental forces have been relatively unexplored. In this work, we introduce a quantitative physical model of the bacterial cell wall that predicts the mechanical response of cell shape to peptidoglycan damage and perturbation in the rod-shaped Gram-negative bacterium Escherichia coli. To test these predictions, we use time-lapse imaging experiments to show that damage often manifests as a bulge on the sidewall, coupled to large-scale bending of the cylindrical cell wall around the bulge. Our physical model also suggests a surprising robustness of cell shape to peptidoglycan defects, helping explain the observed porosity of the cell wall and the ability of cells to grow and maintain their shape even under conditions that limit peptide crosslinking. Finally, we show that many common bacterial cell shapes can be realized within the same model via simple spatial patterning of peptidoglycan defects, suggesting that minor patterning changes could underlie the great diversity of shapes observed in the bacterial kingdom.
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568
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Nejidat A, Saadi I, Ronen Z. Effect of flagella expression on adhesion ofAchromobacter piechaudiito chalk surfaces. J Appl Microbiol 2008; 105:2009-14. [DOI: 10.1111/j.1365-2672.2008.03930.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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569
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Abstract
AIMS To examine the diversity of cultivable 0.2 micron filtrate biofilm forming bacteria from drinking water systems. METHODS AND RESULTS Potable chlorinated drinking water hosts phylogenetically diverse ultramicrocells (UMC) (0.2 and 0.1 microm filterable). UMC (starved or dwarf bacteria) were isolated by cultivation on minimal medium from a flow system wall model with polyvinyl chloride (PVC) pipes. All cultivated cells (25 different isolates) did not maintain their ultra-size after passages on rich media. Cultured UMC were identified by their 16S ribosomal DNA sequences. The results showed that they were closely related to uncultured and cultured members of the Proteobacteria, Actinobacteria and Firmicutes. The isolates of phylum Actinobacteria included representatives of a diverse set of Actinobacterial families: Micrococcaceae, Microbacteriaceae, Dermabacteraceae, Nocardiaceae and Nocardioidaceae. CONCLUSIONS This study is the first to show an abundance of cultivable UMC of various phyla in drinking water system, including a high frequency of bacteria known to be involved in opportunistic infections, such as Stenotrophomonas maltophilia, Microbacterium sp., Pandoraea sp. and Afipia strains. SIGNIFICANCE AND IMPACT OF THE STUDY Chlorinated tap water filtrate (0.2 and 0.1 microm) still harbours opportunistic micro-organisms that can pose some health threat.
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Affiliation(s)
- F S Silbaq
- Mar Elias Educational Institutions and Mar Elias Campus, Ibillin, Galilee, Israel.
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570
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Shiomi D, Sakai M, Niki H. Determination of bacterial rod shape by a novel cytoskeletal membrane protein. EMBO J 2008; 27:3081-91. [PMID: 19008860 DOI: 10.1038/emboj.2008.234] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Accepted: 10/15/2008] [Indexed: 11/09/2022] Open
Abstract
Cell shape is critical for growth, and some genes are involved in bacterial cell morphogenesis. Here, we report a novel gene, rodZ, required for the determination of rod shape in Escherichia coli. Cells lacking rodZ no longer had rod shape but rather were round or oval. These round cells were smaller than known round mutant cells, including mreB and pbpA mutants; both are known to lose rod shape. Morphogenesis from rod cells to round cells and vice versa, caused by depletion and overproduction of RodZ, respectively, revealed that RodZ could regulate the length of the long axis of the cell. RodZ is a membrane protein with bitopic topology such that the N-terminal region including a helix-turn-helix motif is in the cytoplasm, whereas the C-terminal region is exposed in the periplasm. GFP-RodZ forms spirals along the lateral axis of the cell beneath the cell membrane, similar to the MreB bacterial actin. Thus, RodZ may mediate spatial information from cytoskeletal proteins in the cytoplasm to a peptidoglycan synthesis machinery in the periplasm.
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Affiliation(s)
- Daisuke Shiomi
- Microbial Genetics Laboratory, Genetic Strains Research Center, National Institute of Genetics, Mishima, Japan
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571
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Jean JS, Lee MK, Wang SM, Chattopadhyay P, Maity JP. Effects of inorganic nutrient levels on the biodegradation of benzene, toluene, and xylene (BTX) by Pseudomonas spp. in a laboratory porous media sand aquifer model. BIORESOURCE TECHNOLOGY 2008; 99:7807-7815. [PMID: 18329875 DOI: 10.1016/j.biortech.2008.01.064] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2007] [Revised: 01/17/2008] [Accepted: 01/20/2008] [Indexed: 05/26/2023]
Abstract
The effect of inorganic nutrients (sulfate, phosphate, and ammonium chloride) on the aerobic biodegradation of benzene, toluene, and xylene (BTX) by Pseudomonas spp. was studied in the laboratory using a glass sand tank. The increase of nutrient levels resulted in enhanced bacterial growth and BTX degradation. Sulfate and phosphate serve as key electron acceptors in the microbiological processes degrading BTX. The observed bacterial morphological changes during BTX degradation reveal that the filamentous bacteria were the dominant species at low temperatures about 20 degrees C. The spherical and rod-shaped cells became dominant at higher temperatures ranging from 25 degrees C to 28 degrees C. When the BTX mixture was allowed to be biodegraded for longer incubation periods of 21-42 h at high phosphate concentrations, large amounts of rod-shaped cells were clustered. The morphological adaptation appears to be controlled by the temperature and nutrient levels in the sandy medium where Pseudomonas spp. thrives.
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Affiliation(s)
- Jiin-Shuh Jean
- Department of Earth Sciences, National Cheng Kung University, Tainan City 70101, Taiwan.
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572
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Abstract
In recent years, relatively simple MEMS fabrications have helped accelerate our knowledge of the microbial cell. Current progress and challenges in the application of lab-on-a-chip devices to the viable microbe are reviewed. Furthermore, the degree to which microbiologists are becoming the engineers and are tailoring microbial cells and protocells as potential components for bioMEMS devices is highlighted. We conclude this is a highly productive time for microbiologists and microengineers to unite their shared interest in the micron scale world.
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Affiliation(s)
- Colin J Ingham
- Top Institute Food and Nutrition, Nieuwe Kanaal 9A, 6709, PA, Wageningen, The Netherlands.
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573
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Wang Y, Hammes F, Düggelin M, Egli T. Influence of size, shape, and flexibility on bacterial passage through micropore membrane filters. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:6749-6754. [PMID: 18800559 DOI: 10.1021/es800720n] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Sterilization of fluids by means of microfiltration is commonly applied in research laboratories as well as in pharmaceutical and industrial processes. Sterile micropore filters are subject to microbiological validation, where Brevundimonas diminuta is used as a standard test organism. However, several recent reports on the ubiquitous presence of filterable bacteria in aquatic environments have cast doubt on the accuracy and validity of the standard filter-testing method. Six different bacterial species of various sizes and shapes (Hylemonella gracilis, Escherichia coli, Sphingopyxis alaskensis, Vibrio cholerae, Legionella pneumophila, and B. diminuta) were tested for their filterability through sterile micropore filters. In all cases, the slender spirillum-shaped Hylemonella gracilis cells showed a superior ability to pass through sterile membrane filters. Our results provide solid evidence that the overall shape (including flexibility), instead of biovolume, is the determining factor for the filterability of bacteria, whereas cultivation conditions also play a crucial role. Furthermore, the filtration volume has a more important effect on the passage percentage in comparison with other technical variables tested (including flux and filter material). Based on our findings, we recommend a re-evaluation of the grading system for sterile filters, and suggest that the species Hylemonella should be considered as an alternative filter-testing organism for the quality assessment of micropore filters.
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Affiliation(s)
- Yingying Wang
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland
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574
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Smalyukh II, Butler J, Shrout JD, Parsek MR, Wong GCL. Elasticity-mediated nematiclike bacterial organization in model extracellular DNA matrix. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:030701. [PMID: 18850984 DOI: 10.1103/physreve.78.030701] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2008] [Indexed: 05/13/2023]
Abstract
DNA is a common extracellular matrix component of bacterial biofilms. We find that bacteria can spontaneously order in a matrix of aligned concentrated DNA, in which rod-shaped cells of Pseudomonas aeruginosa follow the orientation of extended DNA chains. The alignment of bacteria is ensured by elasticity and liquid crystalline properties of the DNA matrix. These findings show how behavior of planktonic bacteria may be modified in extracellular polymeric substances of biofilms and illustrate the potential of using complex fluids to manipulate embedded nanosized and microsized active particles.
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Affiliation(s)
- Ivan I Smalyukh
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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575
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Ghosh AS, Chowdhury C, Nelson DE. Physiological functions of D-alanine carboxypeptidases in Escherichia coli. Trends Microbiol 2008; 16:309-17. [PMID: 18539032 DOI: 10.1016/j.tim.2008.04.006] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2008] [Revised: 04/09/2008] [Accepted: 04/30/2008] [Indexed: 11/16/2022]
Abstract
Bacterial cell shape is, in part, mediated by the peptidoglycan (murein) sacculus. Penicillin-binding proteins (PBPs) catalyze the final stages of murein biogenesis and are the targets of beta-lactam antibiotics. Several low molecular mass PBPs including PBP4, PBP5, PBP6 and DacD seem to possess DD-carboxypeptidase (DD-CPase) activity, but these proteins are dispensable for survival in laboratory culture. The physiological functions of DD-CPases in vivo are unresolved and it is unclear why bacteria retain these seemingly non-essential and enzymatically redundant enzymes. However, PBP5 clearly contributes to maintenance of cell shape in some PBP mutant backgrounds. In this review, we focus on recent findings concerning the physiological functions of the DD-CPases in vivo, identify gaps in the current knowledge of these proteins and suggest some possible courses for future study that might help reconcile current models of bacterial cell morphology.
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Affiliation(s)
- Anindya S Ghosh
- Department of Biotechnology, Indian Institute of Technology, Kharagpur, District-West Midnapore, West Bengal, PIN-721302, India.
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576
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Zhang X, Newman E. Deficiency in l-serine deaminase results in abnormal growth and cell division of Escherichia coli K-12. Mol Microbiol 2008; 69:870-81. [PMID: 18532981 DOI: 10.1111/j.1365-2958.2008.06315.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The loss of the ability to deaminate l-serine severely impairs growth and cell division in Escherichia coli K-12. A strain from which the three genes (sdaA, sdaB, tdcG) coding for this organism's three l-serine deaminases had been deleted grows well in glucose minimal medium but, on subculture into minimal medium with glucose and casamino acids, it makes very large, abnormally shaped cells, many of which lyse. When inoculated into Luria-Bertani (LB) broth with or without glucose, it makes very long filaments. Provision of S-adenosylmethionine restores cell division in LB broth with glucose, and repairs much of the difficulty in growth in medium with casamino acids. We suggest that replication of E. coli is regulated by methylation, that an unusually high intracellular l-serine concentration, in the presence of other amino acids, starves the cell for S-adenosylmethionine and that it is the absence of S-adenosylmethionine and/or of C1-tetrahydrofolate derivatives that prevents normal cell division.
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Affiliation(s)
- Xiao Zhang
- Biology Department, Concordia University, 1455 de Maisonneuve Ave, Montreal, Quebec, Canada
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577
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Affiliation(s)
- Dylan M. Morris
- Division of Biology, California Institute of Technology, Pasadena, California 91125;
| | - Grant J. Jensen
- Division of Biology, California Institute of Technology, Pasadena, California 91125;
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578
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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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579
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Reyes-Lamothe R, Wang X, Sherratt D. Escherichia coli and its chromosome. Trends Microbiol 2008; 16:238-45. [DOI: 10.1016/j.tim.2008.02.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 02/23/2008] [Accepted: 02/29/2008] [Indexed: 01/22/2023]
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580
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Fiuza M, Canova MJ, Zanella-Cléon I, Becchi M, Cozzone AJ, Mateos LM, Kremer L, Gil JA, Molle V. From the characterization of the four serine/threonine protein kinases (PknA/B/G/L) of Corynebacterium glutamicum toward the role of PknA and PknB in cell division. J Biol Chem 2008; 283:18099-112. [PMID: 18442973 DOI: 10.1074/jbc.m802615200] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Corynebacterium glutamicum contains four serine/threonine protein kinases (STPKs) named PknA, PknB, PknG, and PknL. Here we present the first biochemical and comparative analysis of all four C. glutamicum STPKs and investigate their potential role in cell shape control and peptidoglycan synthesis during cell division. In vitro assays demonstrated that, except for PknG, all STPKs exhibited autokinase activity. We provide evidence that activation of PknG is part of a phosphorylation cascade mechanism that relies on PknA activity. Following phosphorylation by PknA, PknG could transphosphorylate its specific substrate OdhI in vitro. A mass spectrometry profiling approach was also used to identify the phosphoresidues in all four STPKs. The results indicate that the nature, number, and localization of the phosphoacceptors varies from one kinase to the other. Disruption of either pknL or pknG in C. glutamicum resulted in viable mutants presenting a typical cell morphology and growth rate. In contrast, we failed to obtain null mutants of pknA or pknB, supporting the notion that these genes are essential. Conditional mutants of pknA or pknB were therefore created, leading to partial depletion of PknA or PknB. This resulted in elongated cells, indicative of a cell division defect. Moreover, overexpression of PknA or PknB in C. glutamicum resulted in a lack of apical growth and therefore a coccoid-like morphology. These findings indicate that pknA and pknB are key players in signal transduction pathways for the regulation of the cell shape and both are essential for sustaining corynebacterial growth.
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Affiliation(s)
- Maria Fiuza
- Departamento de Biología Molecular, Area de Microbiología, Facultad de Biología, Universidad de León, León, Spain
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581
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Justice SS, Hunstad DA, Cegelski L, Hultgren SJ. Morphological plasticity as a bacterial survival strategy. Nat Rev Microbiol 2008; 6:162-8. [PMID: 18157153 DOI: 10.1038/nrmicro1820] [Citation(s) in RCA: 387] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bacteria have evolved complex systems to maintain consistent cell morphologies. Nevertheless, in certain circumstances, bacteria alter this highly regulated process to transform into filamentous organisms. Accumulating evidence attributes important biological roles to filamentation in stressful environments, including, but not limited to, sites of interaction between pathogenic bacteria and their hosts. Filamentation could represent an intended response to specific environmental cues that promote survival amidst the threats of consumption and killing.
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Affiliation(s)
- Sheryl S Justice
- Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio 43205, USA
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582
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Self-organization in high-density bacterial colonies: efficient crowd control. PLoS Biol 2008; 5:e302. [PMID: 18044986 PMCID: PMC2043048 DOI: 10.1371/journal.pbio.0050302] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Accepted: 09/21/2007] [Indexed: 12/14/2022] Open
Abstract
Colonies of bacterial cells can display complex collective dynamics, frequently culminating in the formation of biofilms and other ordered super-structures. Recent studies suggest that to cope with local environmental challenges, bacterial cells can actively seek out small chambers or cavities and assemble there, engaging in quorum sensing behavior. By using a novel microfluidic device, we showed that within chambers of distinct shapes and sizes allowing continuous cell escape, bacterial colonies can gradually self-organize. The directions of orientation of cells, their growth, and collective motion are mutually correlated and dictated by the chamber walls and locations of chamber exits. The ultimate highly organized steady state is conducive to a more-organized escape of cells from the chambers and increased access of nutrients into and evacuation of waste out of the colonies. Using a computational model, we suggest that the lengths of the cells might be optimized to maximize self-organization while minimizing the potential for stampede-like exit blockage. The self-organization described here may be crucial for the early stage of the organization of high-density bacterial colonies populating small, physically confined growth niches. It suggests that this phenomenon can play a critical role in bacterial biofilm initiation and development of other complex multicellular bacterial super-structures, including those implicated in infectious diseases.
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583
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Three-dimensional imaging of the highly bent architecture of Bdellovibrio bacteriovorus by using cryo-electron tomography. J Bacteriol 2008; 190:2588-96. [PMID: 18203829 DOI: 10.1128/jb.01538-07] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bdellovibrio bacteriovorus cells are small deltaproteobacterial cells that feed on other gram-negative bacteria, including human pathogens. Using cryo-electron tomography, we demonstrated that B. bacteriovorus cells are capable of substantial flexibility and local deformation of the outer and inner membranes without loss of cell integrity. These shape changes can occur in less than 2 min, and analysis of the internal architecture of highly bent cells showed that the overall distribution of molecular machines and the nucleoid is similar to that in moderately bent cells. B. bacteriovorus cells appear to contain an extensive internal network of short and long filamentous structures. We propose that rearrangements of these structures, in combination with the unique properties of the cell envelope, may underlie the remarkable ability of B. bacteriovorus cells to find and enter bacterial prey.
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584
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Morphological changes in an acidophilic bacterium induced by heavy metals. Extremophiles 2008; 12:279-84. [DOI: 10.1007/s00792-007-0128-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Accepted: 11/22/2007] [Indexed: 10/22/2022]
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585
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The Min system as a general cell geometry detection mechanism: branch lengths in Y-shaped Escherichia coli cells affect Min oscillation patterns and division dynamics. J Bacteriol 2008; 190:2106-17. [PMID: 18178745 DOI: 10.1128/jb.00720-07] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Escherichia coli, division site placement is regulated by the dynamic behavior of the MinCDE proteins, which oscillate from pole to pole and confine septation to the centers of normal rod-shaped cells. Some current mathematical models explain these oscillations by considering interactions among the Min proteins without recourse to additional localization signals. So far, such models have been applied only to regularly shaped bacteria, but here we test these models further by employing aberrantly shaped E. coli cells as miniature reactors. The locations of MinCDE proteins fused to derivatives of green fluorescent protein were monitored in branched cells with at least three conspicuous poles. MinCDE most often moved from one branch to another in an invariant order, following a nonreversing clockwise or counterclockwise direction over the time periods observed. In cells with two short branches or nubs, the proteins oscillated symmetrically from one end to the other. The locations of FtsZ rings were consistent with a broad MinC-free zone near the branch junctions, and Min rings exhibited the surprising behavior of moving quickly from one possible position to another. Using a reaction-diffusion model that reproduces the observed MinCD oscillations in rod-shaped and round E. coli, we predict that the oscillation patterns in branched cells are a natural response of Min behavior in cellular geometries having different relative branch lengths. The results provide further evidence that Min protein oscillations act as a general cell geometry detection mechanism that can locate poles even in branched cells.
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586
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Aaron M, Charbon G, Lam H, Schwarz H, Vollmer W, Jacobs-Wagner C. The tubulin homologue FtsZ contributes to cell elongation by guiding cell wall precursor synthesis in Caulobacter crescentus. Mol Microbiol 2007; 64:938-52. [PMID: 17501919 DOI: 10.1111/j.1365-2958.2007.05720.x] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The tubulin homologue FtsZ is well known for its essential function in bacterial cell division. Here, we show that in Caulobacter crescentus, FtsZ also plays a major role in cell elongation by spatially regulating the location of MurG, which produces the essential lipid II peptidoglycan cell wall precursor. The early assembly of FtsZ into a highly mobile ring-like structure during cell elongation is quickly followed by the recruitment of MurG and a major redirection of peptidoglycan precursor synthesis to the midcell region. These FtsZ-dependent events occur well before cell constriction and contribute to cell elongation. In the absence of FtsZ, MurG fails to accumulate near midcell and cell elongation proceeds unperturbed in appearance by insertion of peptidoglycan material along the entire sidewalls. Evidence suggests that bacteria use both a FtsZ-independent and a FtsZ-dependent mode of peptidoglycan synthesis to elongate, the importance of each mode depending on the timing of FtsZ assembly during elongation.
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Affiliation(s)
- Michelle Aaron
- Department of Molecular, Cellular, and Developmental Biology, and Microbiology Program, Yale University, New Haven, CT 06520, USA
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587
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Lawler ML, Brun YV. Advantages and mechanisms of polarity and cell shape determination in Caulobacter crescentus. Curr Opin Microbiol 2007; 10:630-7. [PMID: 17997127 DOI: 10.1016/j.mib.2007.09.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Accepted: 09/14/2007] [Indexed: 11/19/2022]
Abstract
The tremendous diversity of bacterial cell shapes and the targeting of proteins and macromolecular complexes to specific subcellular sites strongly suggest that cellular organization provides important advantages to bacteria in their environment. Key advances have been made in the understanding of the mechanism and function of polarity and cell shape by studying the aquatic bacterium Caulobacter crescentus, whose cell cycle progression involves the ordered synthesis of different polar structures, and culminates in the biosynthesis of a thin polar cell envelope extension called the stalk. Recent results indicate that the important function of polar development is to maximize cell attachment to surfaces and to improve nutrient uptake by nonmotile and attached cells. Major progress has been made in understanding the regulatory network that coordinates polar development and morphogenesis and the role of polar localization of regulatory proteins.
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Affiliation(s)
- Melanie L Lawler
- Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405-3700, USA
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588
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Young KD. Bacterial morphology: why have different shapes? Curr Opin Microbiol 2007; 10:596-600. [PMID: 17981076 DOI: 10.1016/j.mib.2007.09.009] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2007] [Revised: 09/06/2007] [Accepted: 09/07/2007] [Indexed: 10/22/2022]
Abstract
The fact that bacteria have different shapes is not surprising; after all, we teach the concept early and often and use it in identification and classification. However, why bacteria should have a particular shape is a question that receives much less attention. The answer is that morphology is just another way microorganisms cope with their environment, another tool for gaining a competitive advantage. Recent work has established that bacterial morphology has an evolutionary history and has highlighted the survival value of different shapes for accessing nutrients, moving from one place to another, and escaping predators. Shape may be so important in some of these endeavors that an organism may change its morphology to fit the circumstances. In short, if a bacterium needs to eat, divide or survive, or if it needs to attach, move or differentiate, then it can benefit from adopting an appropriate shape.
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Affiliation(s)
- Kevin D Young
- Department of Microbiology and Immunology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202-9037, USA.
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589
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Carballido-López R, Formstone A. Shape determination in Bacillus subtilis. Curr Opin Microbiol 2007; 10:611-6. [PMID: 17981078 DOI: 10.1016/j.mib.2007.09.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Accepted: 09/14/2007] [Indexed: 11/19/2022]
Abstract
The discovery of cytoskeletal elements in prokaryotes has dramatically changed the way we think about bacterial cell morphogenesis. The rod shape of Bacillus subtilis is maintained by the two major polymers (peptidoglycan and teichoic acids) of its thick cell wall and determined by the way these are inserted during growth. The current view is that the dynamic tubulin-like (FtsZ) and actin-like (MreB) cytoskeletons orchestrate, both in time and space, the assembly of macromolecular machineries that effect cell wall synthesis and hydrolysis during cell division and cell elongation, respectively.
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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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590
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Cabeen MT, Jacobs-Wagner C. Skin and bones: the bacterial cytoskeleton, cell wall, and cell morphogenesis. ACTA ACUST UNITED AC 2007; 179:381-7. [PMID: 17967949 PMCID: PMC2064785 DOI: 10.1083/jcb.200708001] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The bacterial world is full of varying cell shapes and sizes, and individual species perpetuate a defined morphology generation after generation. We review recent findings and ideas about how bacteria use the cytoskeleton and other strategies to regulate cell growth in time and space to produce different shapes and sizes.
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Affiliation(s)
- Matthew T Cabeen
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
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591
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Wang Y, Hammes F, Boon N, Egli T. Quantification of the filterability of freshwater bacteria through 0.45, 0.22, and 0.1 microm pore size filters and shape-dependent enrichment of filterable bacterial communities. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2007; 41:7080-6. [PMID: 17993151 DOI: 10.1021/es0707198] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Micro-filtration is a standard process for sterilization in scientific research, medical, and industrial applications, and to remove particles in drinking water or wastewater treatment. It is generally assumed, and confirmed by quantifying filtration efficiency by plating, that filters with a 0.1-0.45 microm pore size can retain bacteria. In contrast to this assumption, we have regularly observed the passage of a significant fraction of natural freshwater bacterial communities through 0.45, 0.22, and 0.1 microm pore size filters. Flow cytometry and a regrowth assay were applied in the present study to quantify and cultivate filterable bacteria. Here we show for the first time a systematic quantification of their filterability, especially their ability to pass through 0.1 microm pore size filters. The filtered bacteria were subsequently able to grow on natural assimilable organic carbon (AOC) with specific growth rates up to 0.47 h(-1). We were able to enrich bacteria communities that pass preferentially through all three pore size filters at significantly increased percentages using successive filtration-regrowth cycles. In all instances, the dominant microbial populations comprised slender spirillum-shaped Hylemonella gracilis strains, suggesting shape-dependent selection during the filtration process. This quantification of the omnipresence of microfilterable bacterial in natural freshwater and their regrowth characteristics demand a change in the sterile filtration practice used in industrial and engineering applications as well as scientific research.
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Affiliation(s)
- Yingying Wang
- Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), PO Box 611, Uberlandstrasse 133, CH-8600 Dübendorf, Switzerland
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592
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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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593
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Swidsinski A, Sydora BC, Doerffel Y, Loening-Baucke V, Vaneechoutte M, Lupicki M, Scholze J, Lochs H, Dieleman LA. Viscosity gradient within the mucus layer determines the mucosal barrier function and the spatial organization of the intestinal microbiota. Inflamm Bowel Dis 2007; 13:963-70. [PMID: 17455202 DOI: 10.1002/ibd.20163] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Migration is an important virulence factor for intestinal bacteria. However, the role of bacterial mobility in the penetration of viscous mucus and their spatial organization within the colon is relatively unknown. METHODS Movements of fecal bacteria were assessed in gels of varying agarose concentrations and were compared with patterns of bacterial distribution observed in colons from conventional and Enterobacter cloacae-monoassociated mice. Bacteria were visualized using fluorescence in situ hybridization. RESULTS Long curly bacteria moved best in moderate viscosity gels, short rods and cocci preferred a low viscous environment, whereas high viscosity immobilized all bacterial groups. The spatial distribution of bacteria in the murine colon was also shape- and not taxonomy-dependent, indicating the existence of vertical (surface to lumen) and longitudinal (proximal to distal colon) viscosity gradients within the mucus layer. Our results suggest that mucus viscosity is low in goblet cells, at the crypt basis and close to the intestinal lumen, whereas sites adjacent to the columnar epithelium have a high mucus viscosity. The mucus viscosity increased progressively toward the distal colon, separating bacteria selectively in the proximal colon and completely in the distal colon. CONCLUSIONS The site-specific regulation of mucus secretion and dehydration make the mucus layer firm and impenetrable for bacteria in regions close to the intestinal mucosa but loose and lubricating in regions adjacent to the luminal contents. Selective control of mucus secretion and dehydration may prove to be a key factor in the management of chronic diseases in which intestinal pathogens are involved.
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Affiliation(s)
- Alexander Swidsinski
- Humboldt University, Charité Hospital, CCM, Laboratory for Molecular Genetics, Polymicrobial Infections and Bacterial Biofilms, Berlin, Germany.
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594
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Abstract
Understanding the mechanisms underlying the establishment of different bacterial cell shapes and the advantage that a particular shape imparts is one of the most fascinating and challenging areas of study in microbiology. One remarkable example of bacterial morphogenesis is the elaboration of long, tubular extensions of the cell envelope of certain aquatic bacteria. These appendages (also called prosthecae or stalks) possess features that make them particularly amenable models for experiments designed to uncover general principles of cell morphogenesis and of cell shape function. Recent evidence supports the hypothesis that stalk synthesis in Caulobacter crescentus is a specialized form of cell elongation that confers to the cell substantial advantages in nutrient uptake. Further insights into the mechanisms and function of stalk synthesis will require a multidisciplinary systems biology approach using principles and methodologies from ecology and evolutionary biology to biophysics and mathematical modelling.
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Affiliation(s)
- Jennifer K Wagner
- Division of Infectious Diseases, Massachusetts General Hospital/Harvard Medical School, Cambridge, MA 02139, USA
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595
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Legaree BA, Daniels K, Weadge JT, Cockburn D, Clarke AJ. Function of penicillin-binding protein 2 in viability and morphology of Pseudomonas aeruginosa. J Antimicrob Chemother 2007; 59:411-24. [PMID: 17289762 DOI: 10.1093/jac/dkl536] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES To investigate the function of penicillin-binding protein 2 (PBP 2) in Pseudomonas aeruginosa PAO1. METHODS The growth and morphology of P. aeruginosa cultured in the absence and presence of mecillinam was assessed. The gene encoding PBP 2, pbpA, was identified in the genome of P. aeruginosa PAO1 and both its full-length and an engineered truncated form were cloned and expressed in Escherichia coli. Site-directed mutagenesis was used to confirm Ser-327 as the catalytic nucleophile of its transpeptidase domain. Allelic exchange was used to construct a chromosomal mutant of pbpA in strain PAO1. RESULTS PAO1 grew with a spherical morphology in the presence of mecillinam at concentrations as high as 2000 mg/L. Both wild-type and truncated, soluble forms of PBP 2 were shown to bind penicillins and a competition assay demonstrated their specificity for mecillinam. The PAO1 DeltapbpA insertional mutant also grew as spheres, and complementation with a plasmid encoding active pbpA, but not with an inactive Ser-327 --> Ala derivative, restored rod-shape morphology. MIC values of a variety of beta-lactams were significantly lower for the insertional mutant compared with wild-type PAO1. The muropeptide profile of peptidoglycan from PAO1 DeltapbpA analysed by HPLC/MALDI TOF MS indicated wild-type levels of cross-linking despite the loss of PBP 2 transpeptidase activity. CONCLUSIONS PBP 2 in P. aeruginosa is responsible for the rod-shape morphology of the cells and contributes significantly to beta-lactam resistance. The viability of cells lacking an active PBP 2 suggests that the organization of the peptidoglycan biosynthetic machinery is different in this pathogen compared with E. coli.
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Affiliation(s)
- Blaine A Legaree
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1 Canada
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