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Gullbrand B, Nordström K. FtsZ ring formation without subsequent cell division after replication runout in Escherichia coli. Mol Microbiol 2000; 36:1349-59. [PMID: 10931285 DOI: 10.1046/j.1365-2958.2000.01949.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In this report, we have investigated cell division after inhibition of initiation of chromosome replication in Escherichia coli. In a culture grown to the stationary phase, cells containing more than one chromosome were able to divide some time after restart of growth, under conditions not allowing initiation of chromosome replication. This shows that there is no requirement for cell division to take place within a certain time after initiation of chromosome replication. Continued growth without initiation of replication resulted in filamented cells that generally did not have any constrictions. Interestingly, FtsZ rings were formed in a majority of these cells as they reached a certain cell length. These rings appeared and were maintained for some time at the cell quarter positions on both sides of the centrally localized nucleoid. These results confirm previous findings that cell division sites are formed independently of chromosome replication and indicate that FtsZ ring assembly is dependent on cell size rather than on the capacity of the cell to divide. Disruption of the mukB gene caused a significant increase in the region occupied by DNA after the replication runout, consistent with a role of MukB in chromosome condensation. The aberrant nucleoid structure was accompanied by a shift in FtsZ ring positioning, indicating an effect of the nucleoid on the positioning of the FtsZ ring. A narrow cell length interval was found, under and over which primarily central and non-central FtsZ rings, respectively, were observed. This finding correlates well with the previously observed oscillatory movement of MinC and MinD in short and long cells.
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Affiliation(s)
- B Gullbrand
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Sweden
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52
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Zaritsky A, Van Geel A, Fishov I, Pas E, Einav M, Woldringh CL. Visualizing multiple constrictions in spheroidal Escherichia coli cells. Biochimie 1999; 81:897-900. [PMID: 10572303 DOI: 10.1016/s0300-9084(99)00206-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
An Escherichia coli cell grows by elongation and divides in a perpendicular plane. Alternating planes of successive divisions in three dimensions can only be ascertained when multiple constrictions exist simultaneously in large, spheroidal cells (with extended constriction process), if the division signals are enhanced. Large, spheroidal cells are obtained by a brief mecillinam treatment, and more frequent divisions are achieved by manipulating the rate of chromosome replication without affecting cell mass growth rate. Such a procedure has recently been performed by thymine-limitation of E. coli K12 strain CR34 (Zaritsky et al., Microbiology 145 (1999), 1052-1022). Enhancing the replication rate in cells with multi-forked replicating chromosomes (by addition of deoxyguanosine) shortens the intervals between successive terminations and thus triggers divisions more frequently. Monoclonal antibodies against FtsZ were used to visualize the rings of secondary constrictions, but apparent shortage of FtsZ to complete rings over wide cells allowed assembly of arcs only. The arcs observed were not parallel nor perpendicular; the tilted constriction planes are consistent with our 3-D 'nucleoid segregation'model for division under conditions which relieve the cylindrical constraint for nucleoid segregation by the bacillari peptidoglycan sacculus (Woldringh et al. , J. Bacteriol. 176 (1994) 6030-6038). The shortage in FtsZ may explain the longer time required to complete the division process in wide cells with long circumferences, observed during thymine step-up. Overexpression of fusion protein FtsZ-GFP on a multi-copy plasmid should circumvent the shortage.
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Affiliation(s)
- A Zaritsky
- Department of Life Sciences, Ben-Gurion University of the Negev, POB 653, Be'er-Sheva84105, Israel
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53
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Santos JM, Freire P, Vicente M, Arraiano CM. The stationary-phase morphogene bolA from Escherichia coli is induced by stress during early stages of growth. Mol Microbiol 1999; 32:789-98. [PMID: 10361282 DOI: 10.1046/j.1365-2958.1999.01397.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Escherichia coli morphogene bolA causes round morphology when overexpressed. The expression of bolA is mainly regulated by a sigmas-dependent gearbox promoter bolA1p. Such regulation results in increased relative levels of expression at slow growth rates, as seen with those attained at the onset of stationary phase. We demonstrate that bolA1p is also induced during early logarithmic growth in response to several forms of stress, and that this induction can be partially sigmas independent. Sudden carbon starvation results in a 17-fold increase in mRNA levels derived from bolA1p 1 h after stress imposition. Increased osmolarity results in a more than 20-fold increase after the same period. Considerable increases in bolA1p mRNA levels were also detected as a result of heat shock, acidic stress and oxidative stress, which has been shown to inhibit sigmas translation. The orders of magnitude of bolA1p induction in log phase due to sudden starvation, osmotic shock and oxidative stress surpass the levels reached in stationary phase. Under sudden carbon starvation and osmotic shock, the cells changed their morphology, resembling those cells in which bolA is overexpressed in stationary phase. Increased expression and morphological changes due to sudden carbon starvation and osmotic shock still occur when sigmaS is not present in a rpoS- background. The results show that expression of bolA is not confined to stationary phase, but it can also play an important role in general stress response. We propose that bolA1p stress induction overrides the normal regulation imposed by growth rate, which is strictly the result of sigmaS-directed transcription.
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Affiliation(s)
- J M Santos
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa. Apt 127, 2780 Oeiras, Portugal
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54
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Botello E, Nordström K. Effects of chromosome underreplication on cell division in Escherichia coli. J Bacteriol 1998; 180:6364-74. [PMID: 9829948 PMCID: PMC107724 DOI: 10.1128/jb.180.23.6364-6374.1998] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The key processes of the bacterial cell cycle are controlled and coordinated to match cellular mass growth. We have studied the coordination between replication and cell division by using a temperature-controlled Escherichia coli intR1 strain. In this strain, the initiation time for chromosome replication can be displaced to later (underreplication) or earlier (overreplication) times in the cell cycle. We used underreplication conditions to study the response of cell division to a delayed initiation of replication. The bacteria were grown exponentially at 39 degreesC (normal DNA/mass ratio) and shifted to 38 and 37 degreesC. In the last two cases, new, stable, lower DNA/mass ratios were obtained. The rate of replication elongation was not affected under these conditions. At increasing degrees of underreplication, increasing proportions of the cells became elongated. Cell division took place in the middle in cells of normal size, whereas the longer cells divided at twice that size to produce one daughter cell of normal size and one three times as big. The elongated cells often produced one daughter cell lacking a chromosome; this was always the smallest daughter cells, and it was the size of a normal newborn cell. These results favor a model in which cell division takes place at only distinct cell sizes. Furthermore, the elongated cells had a lower probability of dividing than the cells of normal size, and they often contained more than two nucleoids. This suggests that for cell division to occur, not only must replication and nucleoid partitioning be completed, but also the DNA/mass ratio must be above a certain threshold value. Our data support the ideas that cell division has its own control system and that there is a checkpoint at which cell division may be abolished if previous key cell cycle processes have not run to completion.
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Affiliation(s)
- E Botello
- Department of Microbiology, Biomedical Center, Uppsala University, S-751 23 Uppsala, Sweden
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55
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Santos Sierra S, Giraldo R, Díaz Orejas R. Functional interactions between chpB and parD, two homologous conditional killer systems found in the Escherichia coli chromosome and in plasmid R1. FEMS Microbiol Lett 1998; 168:51-8. [PMID: 9812362 DOI: 10.1111/j.1574-6968.1998.tb13254.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
parD and chpB are homologous conditional killer systems of plasmid and chromosomal origin, respectively. They are bicistronic operons encoding a killer protein (Kid and ChpBK) and an antidote (Kis and ChpBI). It is shown that the antidote of the chpB system can neutralize the toxin of the parD system. This activity is improved by particular amino acid changes at the amino end of the ChpBI antidote. It is further shown that the chpB system is weakly autoregulated and that the activity of a second promoter, previously identified upstream of the regulated promoter, can modulate the functional interactions between the chpB and parD systems.
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56
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Cano DA, Mouslim C, Ayala JA, García-del Portillo F, Casadesús J. Cell division inhibition in Salmonella typhimurium histidine-constitutive strains: an ftsI-like defect in the presence of wild-type penicillin-binding protein 3 levels. J Bacteriol 1998; 180:5231-4. [PMID: 9748459 PMCID: PMC107562 DOI: 10.1128/jb.180.19.5231-5234.1998] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Histidine-constitutive (Hisc) strains of Salmonella typhimurium undergo cell division inhibition in the presence of high concentrations of a metabolizable carbon source. Filaments formed by Hisc strains show constrictions and contain evenly spaced nucleoids, suggesting a defect in septum formation. Inhibitors of penicillin-binding protein 3 (PBP3) induce a filamentation pattern identical to that of Hisc strains. However, the Hisc septation defect is caused neither by reduced PBP3 synthesis nor by reduced PBP3 activity. Gross modifications of peptidoglycan composition are also ruled out. D-Cycloserine, an inhibitor of the soluble pathway producing peptidoglycan precursors, causes phenotypic suppression of filamentation, suggesting that the septation defect of Hisc strains may be caused by scarcity of PBP3 substrate.
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Affiliation(s)
- D A Cano
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville 41080, Spain
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57
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Levine C, Marians KJ. Identification of dnaX as a high-copy suppressor of the conditional lethal and partition phenotypes of the parE10 allele. J Bacteriol 1998; 180:1232-40. [PMID: 9495763 PMCID: PMC107012 DOI: 10.1128/jb.180.5.1232-1240.1998] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Termination of DNA replication, complete topological unlinking of the parental template DNA strands, partition of the daughter chromosomes, and cell division follow in an ordered and interdependent sequence during normal bacterial growth. In Escherichia coli, topoisomerase IV (Topo IV), encoded by parE and parC, is responsible for decatenation of the two newly formed chromosomes. In an effort to uncover the pathway of information flow between the macromolecular processes that describe these events, we identified dnaX, encoding the tau and gamma subunits of the DNA polymerase III holoenzyme, as a high-copy suppressor of the temperature-sensitive phenotype of the parE10 allele. We show that suppression derives from overexpression of the gamma, but not the tau, subunit of the holoenzyme and that the partition defect of parE10 cells is nearly completely reverted at the nonpermissive temperature as well. These observations suggest a possible association between Topo IV and the replication machinery.
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Affiliation(s)
- C Levine
- Molecular Biology Graduate Program, Cornell University Graduate School of Medical Sciences, New York, New York 10021, USA
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58
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Van de Merwe WP, Li ZZ, Bronk BV, Czégé J. Polarized light scattering for rapid observation of bacterial size changes. Biophys J 1997; 73:500-6. [PMID: 9199812 PMCID: PMC1180949 DOI: 10.1016/s0006-3495(97)78088-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The effect of changing growth conditions on the diameter of rod-shaped bacteria was studied in vivo with the use of polarized light scattering. The value of a ratio of scattering matrix elements was measured as a function of scattering angle at various times after nutritional "upshift" for two strains of Escherichia coli cells. The peak locations of the scattering function were calibrated against the diameter for rod-shaped bacteria. The peaks moved toward smaller angles as a function of time after upshift, indicating that the diameter was increasing. Under special conditions, substantial peak shifts occurred within a few minutes of growth condition change, indicating a rapid onset of growth in diameter. The rate of increase of the diameters after upshift was obtained from the angular shift of peak location. This rate was approximately 14 nm/min for E. coli K12 and approximately 9 nm/min for E. coli B/r at 37 degrees C. The rate of diameter increase is smaller at lower temperatures. Experiments with Bacillus megaterium showed that any diameter change after nutritional upshift at 37 degrees C is limited to at most a very small increase, at least for the strain and medium tested.
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Affiliation(s)
- W P Van de Merwe
- Biomedical Instrumentation Center, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799, USA.
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59
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Abstract
Peptidoglycan (murein) segregation has been studied by means of a new labeling method. The method relies on the ability of Escherichia coli cells to incorporate D-Cys into macromolecular murein. The incorporation depends on a periplasmic amino acid exchange reaction. At low concentrations, D-Cys is innocuous to the cell. The distribution of modified murein in purified sacculi can be traced and visualized by immunodetection of the -SH groups by fluorescence and electron microscopy techniques. Analysis of murein segregation in wild-type and cell division mutant strains revealed that murein in polar caps is metabolically inert and is segregated in a conservative fashion. Elongation of the sacculus apparently occurs by diffuse insertion of precursors over the cylindrical part of the cell surface. At the initiation of cell division, there is a FtsZ-dependent localized activation of murein synthesis at the potential division sites. Penicillin-binding protein 3 and the products of the division genes ftsA and ftsQ are dispensable for the activation of division sites. As a consequence, under restrictive conditions ftsA,ftsI,or ftsQ mutants generate filamentous sacculi with rings of all-new murein at the positions where septa would otherwise develop.
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Affiliation(s)
- M A de Pedro
- Centro de Biología Molecular Severo Ochoa Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Facultad de Ciencias, Spain.
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60
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Abstract
The phenotype of a minC mutant has been reexamined and found to correspond closely to the quantitative predictions of Teather et al. (R. M. Teather, J. F. Collins, and W. D. Donachie, J. Bacteriol. 118:407-413, 1974). We confirm that the number of septa formed per generation per cell length is fixed and independent of the number of available division sites and that "division potential" is directly proportional to cell length. In the minC mutant, septa form with equal probabilities at cell poles, cell centers, and cell quarters. In addition, we show that the time to next division is inversely related to cell length while division is asynchronous in long cells, suggesting that a single cell can form only one septum at a time.
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Affiliation(s)
- W D Donachie
- Institute of Cell and Molecular Biology, University of Edinburgh, Scotland.
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61
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Ruiz-Echevarría MJ, de la Cueva G, Díaz-Orejas R. Translational coupling and limited degradation of a polycistronic messenger modulate differential gene expression in the parD stability system of plasmid R1. MOLECULAR & GENERAL GENETICS : MGG 1995; 248:599-609. [PMID: 7476860 DOI: 10.1007/bf02423456] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The parD stability system of plasmid R1 is an auto-regulated operon containing two genes, kis and kid, that code, respectively, for a killer protein (Kid) and for an antagonist of Kid action (Kis protein). A polycistronic transcript and a shorter mRNA, coding only for Kis and ending in a stem-loop sequence, have been identified as the main parD transcripts in cells carrying a derepressed parD operon. In this communication we show that both parD mRNAs have a half-life close to 1 min and are present in similar amounts. Using an assay based on cell-free extracts of Escherichia coli, we demonstrate that the short kis mRNA originates from limited degradation of the bicistronic parD transcript and that the stem-loop structure within the 5' end of the kid gene is specifically required for the formation of this short transcript. In vivo experiments show that synthesis of Kis is required for efficient synthesis of Kid. These data indicate that RNA processing and translational coupling are important mechanisms that modulate the differential expression of the two genes, kis and kid, in the bicistronic parD operon.
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62
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Flores A, Casadesús J. Suppression of the pleiotropic effects of HisH and HisF overproduction identifies four novel loci on the Salmonella typhimurium chromosome: osmH, sfiW, sfiX, and sfiY. J Bacteriol 1995; 177:4841-50. [PMID: 7665459 PMCID: PMC177256 DOI: 10.1128/jb.177.17.4841-4850.1995] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Insertion mutations that suppress some or all the pleiotropic effects of HisH and HisF overproduction were obtained by using transposons Tn10dTet and Tn10dCam. All suppressor mutations proved to be recessive, indicating that their effects were caused by loss of function; thus, the suppressors identify genes that are necessary to trigger the pleiotropic response when HisH and HisF are overproduced. Genetic mapping of the suppressor mutations identifies four novel loci on the Salmonella typhimurium genetic map. Mutations in osmH (min 49) behave as general suppressors that abolish all manifestations of the pleiotropic response. Mutations in sfiY (min 83) suppress cell division inhibition and thermosensitivity but not osmosensitivity. Mutations that suppress only cell division inhibition define another locus, sfiX (min 44). A fourth novel locus, sfiW (min 19), is also involved in cell division inhibition. The phenotype of sfiW mutations is in turn pleiotropic: they suppress cell division inhibition, make S. typhimurium unable to grow in minimal media, and cause slow growth and abnormal colony and cell shape. The inability of sfiW mutants to grow in minimal medium cannot be relieved by any known nutritional requirement or by the use of carbon sources other than glucose. The hierarchy of suppressor phenotypes and the existence of epistatic effects among suppressor mutations suggest a pathway-like model for the Hisc pleiotropic response.
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Affiliation(s)
- A Flores
- Departamento de Genética, Universidad de Sevilla, Spain
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63
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Donachie WD, Addinall S, Begg K. Cell shape and chromosome partition in prokaryotes or, why E. coli is rod-shaped and haploid. Bioessays 1995; 17:569-76. [PMID: 7575501 DOI: 10.1002/bies.950170616] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In the rod-shaped cells of E. coli, chromosome segregation takes place immediately after replication has been completed. A septum then forms between the two sister chromosomes. In the absence of certain membrane proteins, cells grow instead as large, multichromosomal spheres that divide successively in planes that are at right angles to one another. Although multichromosomal, the spherical cells cannot be maintained as heterozygotes. These observations imply that, in these mutants, each individual chromosome gives rise to a separate clone of descendant cells. This suggests a model in which sites for cell division form between pairs of sister chromosomes at the time of segregation, but are not used in spherical cells until further rounds of replication have taken place, thus ensuring clonal ('hierarchical') segregation of chromosomes into progeny cells. The role of the morphogenetic membrane proteins is to convert the basically spherical cell into a cylinder that is able to divide as soon as replication and segregation have been completed, and thus to maximise the number of viable cells per genome.
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Affiliation(s)
- W D Donachie
- Institute of Cell and Molecular Biology, University of Edinburgh, Scotland
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64
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Abstract
The harmonious growth and cell-to-cell uniformity of steady-state bacterial populations indicate the existence of a well-regulated cell cycle, responding to a set of internal signals. In Escherichia coli, the key events of this cycle are the initiation of DNA replication, nucleoid segregation and the initiation of cell division. The replication initiator is the DnaA protein. In nucleoid segregation, the MukB protein, required for proper partitioning, may be a member of the myosin-kinesin superfamily of mechanoenzymes. In cell division, the FtsZ protein has a tubulin motif, is a GTPase and polymerizes in a ring around midcell during septation; the FtsA protein has an actin-like structure. The nature of the internal signals triggering these events is not known but candidates include cell mass, the superhelical density of the chromosome and the concentration of two regulatory nucleotides, cyclic AMP and ppGpp. The involvement of cytoskeletal-like proteins in key cycle events encourages the notion of a fundamental biological unity in cell cycle regulation in all organisms.
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Affiliation(s)
- D Vinella
- Institut Jacques Monod, CNRS, Université Paris 7, France
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65
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Kid, a small protein of the parD stability system of plasmid R1, is an inhibitor of DNA replication acting at the initiation of DNA synthesis. J Mol Biol 1995. [DOI: 10.1016/s0022-2836(05)80138-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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66
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James GA, Korber DR, Caldwell DE, Costerton JW. Digital image analysis of growth and starvation responses of a surface-colonizing Acinetobacter sp. J Bacteriol 1995; 177:907-15. [PMID: 7860599 PMCID: PMC176682 DOI: 10.1128/jb.177.4.907-915.1995] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Surface growth of an Acinetobacter sp. cultivated under several nutrient regimens was examined by using continuous-flow slide culture, phase-contrast microscopy, scanning confocal laser microscopy, and computer image analysis. Irrigation of attached coccoid stationary-phase Acinetobacter sp. cells with high-nutrient medium resulted in a transition from coccoid to bacillar morphology. Digital image analysis revealed that this transition was biphasic. During phase I, both the length and the width of cells increased. In contrast, cell width remained constant during phase II, while both cell length and cell area increased at a rate greater than in phase I. Cells were capable of growth and division without morphological transition when irrigated with a low-nutrient medium. Rod-shaped cells reverted to cocci by reduction-division when irrigated with starvation medium. This resulted in conservation of cell area (biomass) with an increase in cell number. In addition, the changes in cell morphology were accompanied by changes in the stability of cell attachment. During phase I, coccoid cells remained firmly attached. Following transition in high-nutrient medium, bacillar cells displayed detachment, transient attachment, and drifting behaviors, resulting in a spreading colonization pattern. In contrast, cells irrigated with a low-nutrient medium remained firmly attached to the surface and eventually formed tightly packed microcolonies. It is hypothesized that the coccoid and bacillar Acinetobacter sp. morphotypes and associated behavior represent specialized physiological adaptations for attachment and colonization in low-nutrient systems (coccoid morphotype) or dispersion under high-nutrient conditions (bacillar morphotype).
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Affiliation(s)
- G A James
- Department of Biological Sciences, University of Calgary, Alberta, Canada
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67
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Schreiber G, Ron EZ, Glaser G. ppGpp-mediated regulation of DNA replication and cell division in Escherichia coli. Curr Microbiol 1995; 30:27-32. [PMID: 7765879 DOI: 10.1007/bf00294520] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
ppGpp serves as an alarmon in prokaryotes, distributing and coordinating different cellular processes according to the nutritional potential of the growth medium. This work is interpreted as favoring the view that, in addition to its previously documented role in regulating the rate of ribosome synthesis, ppGpp participates in coordinating DNA replication and cell division. We studied the effects of ppGpp on the cell division cycle, using cells containing plasmid pSM11 that codes for the 55-kDa truncated RelA protein under the inducible Ptac promoter. In this system it was found that the rate of initiation of new rounds of DNA replication is inversely correlated with the intracellular level of ppGpp. Furthermore, ppGpp levels similar to those found during the activation of stringent control inhibited replication initiation, in a manner comparable to that resulting from inhibition of protein synthesis by amino acid starvation or by chloramphenicol addition. However, in contrast to chloramphenicol treatment, elevated ppGpp levels did not block septum formation, and, in fact, there is some evidence for enhanced septation. As a result, the residual cell division following elevation in ppGpp levels was higher than after chloramphenicol treatment, resulting in cells with a size similar to that of stationary phase cells.
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Affiliation(s)
- G Schreiber
- Department of Cellular Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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68
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Khattar MM, Begg KJ, Donachie WD. Identification of FtsW and characterization of a new ftsW division mutant of Escherichia coli. J Bacteriol 1994; 176:7140-7. [PMID: 7961485 PMCID: PMC197100 DOI: 10.1128/jb.176.23.7140-7147.1994] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The product of the ftsW gene has been identified as a polypeptide that, like the related RodA protein, shows anomalous mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. FtsW is produced at low levels that can be increased by altering the translation initiation region of the mRNA. Overproduction of FtsW strongly inhibits cell growth. A new mutant allele, ftsW201, causes a temperature-dependent block in the initiation stage of cell division which is similar to the division block in ftsZ mutants. The block in initiation of division in the ftsW201 allele is shown to be independent of FtsZ or the FtsZ inhibitor, SulA. In addition, the ftsW201 mutant is hypersensitive to overproduction of the division initiation protein FtsZ at the permissive temperature. Our results suggest a role for FtsW in an early stage of division which may involve an interaction with FtsZ.
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Affiliation(s)
- M M Khattar
- Institute of Cell and Molecular Biology, University of Edinburgh, Scotland
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69
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Sánchez M, Dopazo A, Pla J, Robinson AC, Vicente M. Characterisation of mutant alleles of the cell division protein FtsA, a regulator and structural component of the Escherichia coli septator. Biochimie 1994; 76:1071-4. [PMID: 7748929 DOI: 10.1016/0300-9084(94)90032-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Two alleles of ftsA, a gene that encodes an essential cell division protein in Escherichia coli, have-been mapped at the nucleotide level. The mutations are located inside domains that are conserved in an ATP-binding protein family. The ftsA2 mutation lies in the adenine-binding domain, and the ftsA3 in the ribose-binding domain. The defect in ampicillin binding to PBP3 described for allele ftsA3 is allele-specific. This supports the hypothesis of the existence of different domains in FtsA having different functions.
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Affiliation(s)
- M Sánchez
- Departamento de Biología Celular y del Desarrollo, CIB, CSIC, Madrid, Spain
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70
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Satta G, Fontana R, Canepari P. The two-competing site (TCS) model for cell shape regulation in bacteria: the envelope as an integration point for the regulatory circuits of essential physiological events. Adv Microb Physiol 1994; 36:181-245. [PMID: 7942315 DOI: 10.1016/s0065-2911(08)60180-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- G Satta
- Institute of Microbiology, Catholic University of Sacred Heart, Rome, Italy
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71
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Donachie WD. What is the minimum number of dedicated functions required for a basic cell cycle? Curr Opin Genet Dev 1992; 2:792-8. [PMID: 1458027 DOI: 10.1016/s0959-437x(05)80141-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The genome of Escherichia coli has a coding capacity for about 4500 proteins but only a small number of these appear to be specific for the periodic events (initiation of DNA replication, chromosome partitioning and cell division) that punctuate the cell-duplication cycle: furthermore, many of these cell cycle dedicated functions are dispensible under certain conditions, although their presence undoubtedly increases the fitness of the organism to survive in a competitive environment. A simplified but effective cell replication cycle can probably operate with only a few cycle-dedicated proteins, in addition to those required for cell growth itself.
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Affiliation(s)
- W D Donachie
- Institute of Cell and Molecular Biology, University of Edinburgh, Scotland
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72
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Cooper S. Synthesis of the cell surface during the division cycle of rod-shaped, gram-negative bacteria. Microbiol Rev 1991; 55:649-74. [PMID: 1779930 PMCID: PMC372841 DOI: 10.1128/mr.55.4.649-674.1991] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
When the growth of the gram-negative bacterial cell wall is considered in relation to the synthesis of the other components of the cell, a new understanding of the pattern of wall synthesis emerges. Rather than a switch in synthesis between the side wall and pole, there is a partitioning of synthesis such that the volume of the cell increases exponentially and thus perfectly encloses the exponentially increasing cytoplasm. This allows the density of the cell to remain constant during the division cycle. This model is explored at both the cellular and molecular levels to give a unified description of wall synthesis which has the following components: (i) there is no demonstrable turnover of peptidoglycan during cell growth, (ii) the side wall grows by diffuse intercalation, (iii) pole synthesis starts by some mechanism and is preferentially synthesized compared with side wall, and (iv) the combined side wall and pole syntheses enclose the newly synthesized cytoplasm at a constant cell density. The central role of the surface stress model in wall growth is distinguished from, and preferred to, models that propose cell-cycle-specific signals as triggers of changes in the rate of wall synthesis. The actual rate of wall synthesis during the division cycle is neither exponential nor linear, but is close to exponential when compared with protein synthesis during the division cycle.
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Affiliation(s)
- S Cooper
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-0620
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73
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Ruiz-Echevarría MJ, Berzal-Herranz A, Gerdes K, Díaz-Orejas R. The kis and kid genes of the parD maintenance system of plasmid R1 form an operon that is autoregulated at the level of transcription by the co-ordinated action of the Kis and Kid proteins. Mol Microbiol 1991; 5:2685-93. [PMID: 1779758 DOI: 10.1111/j.1365-2958.1991.tb01977.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Stability mediated by the parD system of plasmid R1 is modulated by a killer protein, Kid, and by an antagonist of this function, Kis. Determination of the 5' ends of ParD transcripts, revealed that the genes coding for these proteins are transcribed from a single promoter. Analysis of the 3' end of the ParD RNAs indicated the existence of two transcripts: one of them coding for the Kis and Kid proteins, and the other coding only for Kis. Analysis of the effects of parD+ and kis+ recombinants on the beta-galactosidase levels expressed by different transcriptional and translational parD-lacZ fusions, and on the ParD RNA levels determined by a derepressed parD mutant, indicated that the Kis and Kid proteins repress coordinately the parD system at the transcriptional level. We discuss the relevance of these results in terms of the activities of the Kis and Kid proteins and in the context of the stabilization mediated by parD.
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74
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Kooijman SA, Muller EB, Stouthamer AH. Microbial growth dynamics on the basis of individual budgets. Antonie Van Leeuwenhoek 1991; 60:159-74. [PMID: 1807193 DOI: 10.1007/bf00430363] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The popular theories for microbial dynamics by Monod, Pirt and Droop are shown to be special cases of a model for individual budgets, in which growth and maintenance are on the expense of reserve materials. The dynamics of reserve materials is a first order process with a relaxation time proportional to cell length; maintenance is proportional to cell volume, and uptake, which depends hyperbolically on substrate density, is proportional to cell volume as well. Because of the latter, population dynamics depends on the behaviour of the individuals in a simple way, such that the cell volume distribution has no quantitative effect. When uptake is proportional to the surface area of the cell, which is realistic from a physical point of view, the relation between the individual level and the population one becomes more complicated and the cell size and shape distribution affects population dynamics. It is shown how the changing shape of rods modifies uptake and, consequently, growth. The concept of energy conductance, defined as the ratio of the maximum surface area specific uptake and the volume specific energy reserve has been introduced in the analysis of microbial dynamics. The first tentative results indicate that the value for E. coli is close to the mean value for a wide variety of animals. Properties of the model for cell suspension at constant substrate densities are analyzed and tested against a variety of experimental data from the literature on both the individual and the population level.
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Affiliation(s)
- S A Kooijman
- Biological Laboratory, Free University, Amsterdam, The Netherlands
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75
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Abstract
Many differentiation processes in both prokaryotes and eukaryotes begin with an asymmetric division, producing 'daughter' cells that differ in size and developmental fate. This is particularly obvious in the well-studied prokaryotic life cycles of Caulobacter and Bacillus. In no system, however, is the mechanism of asymmetric division understood. Here I propose a model for the mechanism of asymmetric division during sporulation in Bacillus subtilis. The model explains both the timing and asymmetric localization of spore-septum formation. It also explains the morphological phenotypes of various asporogenous (spo) mutants.
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Affiliation(s)
- J Errington
- Sir William Dunn School of Pathology, University of Oxford, UK
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76
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Ruiz-Echevarría MJ, de Torrontegui G, Giménez-Gallego G, Díaz-Orejas R. Structural and functional comparison between the stability systems ParD of plasmid R1 and Ccd of plasmid F. MOLECULAR & GENERAL GENETICS : MGG 1991; 225:355-62. [PMID: 2017133 DOI: 10.1007/bf00261674] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The stability determined by the systems ParD of plasmid R1 and Ccd of plasmid F is due to the concerted action of two proteins, a cytotoxin and an antagonist of this function. In this paper we report that CcdA and Kis proteins, the antagonists of the Ccd and ParD systems respectively, share significant sequence homologies at both ends. In Kis, these regions seem to correspond to two different domains. Despite the structural similarities, Kis and CcdA are not interchangeable. In addition we have shown that the cytotoxins of these systems, the Kid and CcdB proteins, do not share structural homologies. In contrast to CcdB, the Kid protein of the ParD system induces RecA-dependent cleavage of the cI repressor of bacteriophage lambda very inefficiently or not at all. The functional implications of these results are discussed.
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77
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Gilbert P, Collier PJ, Brown MR. Influence of growth rate on susceptibility to antimicrobial agents: biofilms, cell cycle, dormancy, and stringent response. Antimicrob Agents Chemother 1990; 34:1865-8. [PMID: 2291653 PMCID: PMC171955 DOI: 10.1128/aac.34.10.1865] [Citation(s) in RCA: 305] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- P Gilbert
- Department of Pharmaceutical Sciences, Aston University Birmingham United Kingdom
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78
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Abstract
Cell division is regulated so that it occurs only once per cell cycle. In Escherichia coli, a rod-shaped bacterium, division normally takes place at the center of the long axis of the cell; however, in the minicell mutant, division can also take place at the cell pole. Such divisions take place at the expense of normal divisions, resulting in an overall increase in nucleated cell length. We report here that increasing the level of FtsZ can completely suppress the cell length of the minicell mutant by increasing the frequency at which cell division events take place. This result suggests that the level of FtsZ controls the frequency of cell division in E. coli.
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Affiliation(s)
- E Bi
- Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City 66103
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79
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D'Ari R, Maguin E, Bouloc P, Jaffé A, Robin A, Liébart JC, Joseleau-Petit D. Aspects of cell cycle regulation. Res Microbiol 1990; 141:9-16. [PMID: 2194254 DOI: 10.1016/0923-2508(90)90093-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- R D'Ari
- Institut Jacques Monod, Université Paris 7
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80
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Affiliation(s)
- W D Donachie
- Department of Molecular Biology, University of Edinburgh
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81
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Puyet A, Cánovas JL. Changes of Escherichia coli cell cycle parameters during fast growth and throughout growth with limiting amounts of thymine. Arch Microbiol 1989; 152:578-83. [PMID: 2686574 DOI: 10.1007/bf00425490] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
It is generally accepted that during fast growth of Escherichia coli, the time (D) between the end of a round of DNA replication and cell division is constant. This concept is not consistent with the fact that average cell mass of a culture is an exponential function of the growth rate, if it is also accepted that average cell mass per origin of DNA replication (Mi) changes with growth rate and negative exponential cell age distribution is taken into account. Data obtained from cell composition analysis of E. coli OV-2 have shown that not only Mi but also D varied with growth rate at generation times (tau) between 54 and 30 min. E. coli OV-2 is a thymine auxotroph in which the replication time (C) can be lengthened, without inducing changes in tau, by growth with limiting amounts of thymine. This property has been used to study the relationship between cell size and division from cell composition measurements during growth with different amounts of thymine. When C increased, average cell mass at the end of a round of DNA replication also increased while D decreased, but only the time lapse (d) between the end of a replication round and cell constriction initiation appeared to be affected because the constriction period remained fairly constant. We propose that the rate at which cells proceed to constriction initiation from the end of replication is regulated by cell mass at this event, big cells having shorter d times than small cells.
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Affiliation(s)
- A Puyet
- Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
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82
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Cooper S. The constrained hoop: an explanation of the overshoot in cell length during a shift-up of Escherichia coli. J Bacteriol 1989; 171:5239-43. [PMID: 2676969 PMCID: PMC210357 DOI: 10.1128/jb.171.10.5239-5243.1989] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- S Cooper
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-0620
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83
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Donachie WD, Begg KJ. Chromosome partition in Escherichia coli requires postreplication protein synthesis. J Bacteriol 1989; 171:5405-9. [PMID: 2676975 PMCID: PMC210377 DOI: 10.1128/jb.171.10.5405-5409.1989] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
After inhibition of protein synthesis, the number of nuclear bodies (nucleoids) visible in cells of Escherichia coli B/rA corresponded closely to the number of completely replicated chromosomes. We calculated that nucleoid partition follows almost immediately after replication forks reach the chromosome terminus. We show that such a partition is dependent on protein synthesis and that this may reflect the requirement that cells must achieve a certain minimum length before partition (and subsequent cell division) can take place.
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Affiliation(s)
- W D Donachie
- Department of Molecular Biology, University of Edinburgh, Scotland
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84
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Dewar SJ, Kagan-Zur V, Begg KJ, Donachie WD. Transcriptional regulation of cell division genes in Escherichia coli. Mol Microbiol 1989; 3:1371-7. [PMID: 2515414 DOI: 10.1111/j.1365-2958.1989.tb00118.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The complete Escherichia coli ftsQ coding sequence, together with part of the ftsA coding sequence, has been cloned upstream of the lacZ open reading frame in a lambda-vector (lambda JFL100). Cells which are lysogenic for lambda JFL100 transcribe the cloned lacZ from promoter(s) within the ftsQ and ftsA sequences. The level of beta-galactosidase produced is dependent on growth rate (and/or cell size) and is derepressed in an ftsA-deficient mutant. Transcription during the cell cycle is restricted to the time of cell division.
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Affiliation(s)
- S J Dewar
- Department of Molecular Biology, University of Edinburgh, UK
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85
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Donachie WD, Begg KJ. Cell length, nucleoid separation, and cell division of rod-shaped and spherical cells of Escherichia coli. J Bacteriol 1989; 171:4633-9. [PMID: 2670889 PMCID: PMC210261 DOI: 10.1128/jb.171.9.4633-4639.1989] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
By comparing the dimensions and DNA contents of normal rod-shaped Escherichia coli with those of mutants that grow as spheres or ellipsoids, we have determined that two parameters remain unchanged: the DNA/mass ratio and the average cell length (diameter, for spherical cells). In consequence, the average volumes and DNA contents of the spherical mutant cells are about four to six times greater than those of rod-shaped cells growing at a similar rate. In addition, it was found that cells of both rod and sphere forms had approximately the same number of nucleoids (as seen when the DNA was condensed after inhibition of protein synthesis). The nucleoids of the spherical cells therefore consist of four to six completed chromosomes each (polytene nucleoids). We suggest that the attainment of a minimum cell length is necessary for nucleoid separation after chromosome replication and that such a separation is itself a prerequisite for septum formation.
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Affiliation(s)
- W D Donachie
- Department of Molecular Biology, University of Edinburgh, Scotland
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86
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Prats R, de Pedro MA. Normal growth and division of Escherichia coli with a reduced amount of murein. J Bacteriol 1989; 171:3740-5. [PMID: 2500418 PMCID: PMC210119 DOI: 10.1128/jb.171.7.3740-3745.1989] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The classical model of a murein monolayer for the structure of the murein sacculus of Escherichia coli is at present a controversial matter due to recent advances in the microscopic and biochemical knowledge of this cellular component (B. Glauner, J.-V. Höltje, and U. Schwarz, J. Biol. Chem. 263:10088-10095, 1988; M. Leduc, C. Frehel, E. Siegel, and J. van Heijenoort, manuscript in preparation). We have studied how the limitation in the supply of the murein-specific precursor meso-diaminopimelic acid (DAP) would affect cell growth and morphology as well as murein structure and content per unit of surface area in E. coli strains auxotrophic for DAP. Our observations indicated that the amount of murein per unit of cell surface area could be reduced by about 50% when the external concentration of DAP was equal to or lower than 0.5 microgram/ml. Cells with a reduced amount of murein did not show any detectable alteration in their morphology and characteristics of growth. Furthermore, no major alterations in murein structure were observed by high-pressure liquid chromatography analysis. However, the modification of murein that normally takes place at the initiation of the stationary phase was partially prevented. These results favor the alternative hypothesis of a thin, multilayered structure for the sacculus of E. coli rather than the monolayer model.
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Affiliation(s)
- R Prats
- Centro de Biología Molecular, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Spain
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87
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Ortega S, de Torrontegui G, Díaz R. Isolation and characterization of a conditional replication mutant of the antibiotic resistance factor R1 affected in the gene of the replication protein repA. MOLECULAR & GENERAL GENETICS : MGG 1989; 217:111-7. [PMID: 2671646 DOI: 10.1007/bf00330949] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In vitro mutagenesis with hydroxylamine of a ParD- miniderivative of R1, pAB174, yielded mutants that were less stable in the cell than pAB174. Some of these mutants had a thermosensitive phenotype. The replication of pAB2623, one of the thermosensitive mutants, was inhibited in the cell at the restrictive temperature of 42 degrees C. The efficiency of the RepA protein of pAB2623 to promote replication of R1 in an in vitro assay was greatly reduced. Sequence analysis indicated that the repA gene of pAB2623 contains, close to its 3' end, two GC-AT transitions, separated by a single base, that change two consecutive codons of the gene. These results indicate that the phenotype of the mutant is the consequence of a mutated RepA protein and is consistent with the requirement of RepA for the in vivo replication of this plasmid.
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Affiliation(s)
- S Ortega
- Centro de Investigaciones Biológicas (C.S.I.C.), Madrid, Spain
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88
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Bravo A, Ortega S, de Torrontegui G, Díaz R. Killing of Escherichia coli cells modulated by components of the stability system ParD of plasmid R1. MOLECULAR & GENERAL GENETICS : MGG 1988; 215:146-51. [PMID: 3071737 DOI: 10.1007/bf00331316] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The proteins P10 and P12 have been shown to be gene products of a new stability system, ParD, of plasmid R1. It is now shown that an R1 miniplasmid, pAB112, carrying a trans-complementable amber mutation in the gene of the P10 protein, is lethal for the host in the absence of suppression. This lethal effect is suppressed in a supF background and also by deletions in pAB112 that affect the gene of the P12 protein. These data indicate that the P12 protein has a lethal effect on the host and that this effect is neutralized by the P10 protein. The possibility that the stabilization conferred by the ParD system could be due to a counterselection, mediated by P12, of cells that lose the plasmid at cell division, is discussed.
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Affiliation(s)
- A Bravo
- Centro de Investigaciones Biológicas, (C.S.I.C.), Madrid, Spain
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89
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Aldea M, Hernández-Chico C, de la Campa AG, Kushner SR, Vicente M. Identification, cloning, and expression of bolA, an ftsZ-dependent morphogene of Escherichia coli. J Bacteriol 1988; 170:5169-76. [PMID: 3053647 PMCID: PMC211586 DOI: 10.1128/jb.170.11.5169-5176.1988] [Citation(s) in RCA: 99] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A newly found morphogene of Escherichia coli, bolA, mapping at min 10 of the genetic map, was cloned in a 7.2-kilobase BamHI fragment and identified by its ability to produce osmotically stable spherical cells when overexpressed. This gene codes for a polypeptide of 13 kilodaltons. Overexpression of bolA+ was achieved in low-copy-number vectors with operon fusions to the tet and lac promoters, indicating a clockwise direction of transcription. While no modification of any of the penicillin-binding proteins was observed, morphological effects due to overexpression of bolA+ were shown to be dependent on the presence of an active ftsZ gene product. Our results suggest the existence of a mechanism mediated by FtsZ for modifying the conformation of nascent murein in the early steps of septum formation.
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Affiliation(s)
- M Aldea
- Department of Genetics, University of Georgia, Athens 30602
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90
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Segregation of elongation potential inEscherichia coli mediated by thewee genetic system. Curr Microbiol 1988. [DOI: 10.1007/bf01570871] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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91
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Robinson AC, Begg KJ, Sweeney J, Condie A, Donachie WD. Mapping and characterization of mutants of the Escherichia coli cell division gene, ftsA. Mol Microbiol 1988; 2:581-8. [PMID: 2846985 DOI: 10.1111/j.1365-2958.1988.tb00066.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Eight independent temperature-sensitive mutants of the cell division protein FtsA have been studied. They fall into two classes in terms of their behaviour at 42 degrees C and recovery at 30 degrees C. The first class shows salt-dependent temperature-sensitivity and reversible inactivation of FtsA protein at 42 degrees C. The second shows irreversible inactivation which is not prevented by salt. Recovery of the ability to divide at 30 degrees C is rapid in mutants of the first group, but is delayed for approximately a generation time in the second group. This suggests that irreversible inactivation of FtsA causes extensive damage to the division machinery. The amino acid substitutions show clustering to a limited domain of the protein, and one particular substitution is found in three of the mutants.
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Affiliation(s)
- A C Robinson
- Department of Molecular Biology, University of Edinburgh, UK
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92
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Ayala JA, Plá J, Desviat LR, de Pedro MA. A lacZ-pbpB gene fusion coding for an inducible hybrid protein that recognizes localized sites in the inner membrane of Escherichia coli. J Bacteriol 1988; 170:3333-41. [PMID: 3136138 PMCID: PMC211299 DOI: 10.1128/jb.170.8.3333-3341.1988] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
An in-phase gene fusion consisting of the 5'-terminal 1,314 base pairs (bp) of the structural gene for beta-galactosidase (lacZ) and the 3'-terminal 1,644 bp of the structural gene coding for penicillin-binding protein 3 (pbpB) of Escherichia coli was constructed and cloned in the plasmid pDIAM64. The product of the fusion gene was a remarkably stable protein with an apparent molecular weight of 110,000 (p110) that retained the ability to covalently interact with beta-lactam antibiotics. The fusion protein was found associated with the membrane at low levels of induction, but it accumulated in the cytoplasm of cells induced for a long time as inclusion bodies of high density. Inclusion bodies were localized at defined positions corresponding to septal sites in all of the pDIAM64-containing strains tested except PAT84 and GD113 (which carry the ftsZ84 mutant allele). These findings indicate a possible role of the FtsZ protein in the integration of Pbp3 into the membrane and in septum localization during the cell division cycle.
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Affiliation(s)
- J A Ayala
- Instituto de Biología Molecular, Universidad Autónoma de Madrid, Spain
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93
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Kirkwood TB, Burdett ID. Estimating the growth pattern of micro-organisms in distinct stages of the cell cycle. J Theor Biol 1988; 130:255-73. [PMID: 3138503 DOI: 10.1016/s0022-5193(88)80029-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Knowledge of the growth patterns of micro-organisms is required to understand how cell growth and division are controlled and co-ordinated in relation to mechanisms of wall assembly and chromosome duplication. Direct observation, e.g. by time-lapse studies, is usually limited in accuracy by the small size of the cells. Indirect methods have therefore been developed which give estimates of the growth patterns of cells, based on the analysis of distributions of cell size in populations in balanced exponential growth. Previously, we have compared such methods (Burdett & Kirkwood, 1983) and concluded that the most powerful approach is that proposed by Collins & Richmond (1962), in which growth rate is calculated as a function of cell size using size distributions of extant, separating and new-born cells. A limitation of this method has been, however, that it gives only an estimate for the average growth rate of cells at a given size, irrespective of the state of progress of individual cells through the cell cycle. In this paper, we describe an extension to the standard Collins-Richmond procedure which provides separate estimates for the growth pattern of cells in distinct stages of the cell cycle, and we illustrate the method in relation to growth of mononucleate, binucleate and septate cells of Bacillus subtilis. It is demonstrated that this three-stage analysis is clearly superior to the standard method, in that it provides more detailed and probably more realistic information. We also demonstrate how to assess the precision and accuracy of the estimated growth pattern. Generalization of the method to any number of stages and to multiple as well as binary fission is described.
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Affiliation(s)
- T B Kirkwood
- Laboratory of Computing, National Institute for Medical Research, London, England
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94
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Kretschmer S. Stepwise increase of elongation rate in individual hyphae ofStreptomyces granaticolor during outgrowth. J Basic Microbiol 1988. [DOI: 10.1002/jobm.3620280106] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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95
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Cooper S. Rate and topography of cell wall synthesis during the division cycle of Salmonella typhimurium. J Bacteriol 1988; 170:422-30. [PMID: 3275624 PMCID: PMC210659 DOI: 10.1128/jb.170.1.422-430.1988] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The rates of synthesis of peptidoglycan and protein during the division cycle of Salmonella typhimurium have been measured by using the membrane elution technique and differentially labeled diaminopimelic acid and leucine. The cells were labeled during unperturbed exponential growth and then bound to a nitrocellulose membrane by filtration. Newborn cells were eluted from the membrane with fresh medium. The radioactivity in the newborn cells in successive fractions was determined. As the cells are eluted from the membrane as a function of their cell cycle age at the time of labeling, the rate of incorporation of the different radioactive compounds as a function of cell cycle age can be determined. During the first part of the division cycle, the ratio of the rates of protein and peptidoglycan synthesis was constant. During the latter part of the division cycle, there was an increase in the rate of peptidoglycan synthesis relative to the rate of protein synthesis. These results support a simple, bipartite model of cell surface increase in rod-shaped cells. Before the start of constriction, the cell surface increased only by cylindrical extension. After cell constriction started, the cell surface increased by both cylinder and pole growth. The increase in surface area was partitioned between the cylinder and the pole so that the volume of the cell increased exponentially. No variation in cell density occurred because the increase in surface allowed a continuous exponential increase in cell volume that accommodated the exponential increase in cell mass. Protein was synthesized exponentially during the division cycle. The rate of cell surface increase was described by a complex equation which is neither linear nor exponential.
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Affiliation(s)
- S Cooper
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-0620
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96
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Grover NB, Woldringh CL, Koppes LJ. Elongation and surface extension of individual cells of Escherichia coli B/r: comparison of theoretical and experimental size distributions. J Theor Biol 1987; 129:337-48. [PMID: 3332028 DOI: 10.1016/s0022-5193(87)80006-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The way individual cells grow and divide uniquely determines the (time-invariant) cell size distribution of populations in steady-state exponential growth. In the preceding article, theoretical distributions were derived for two exponential and six linear models containing a small number of adjustable parameters but no assumptions other than that all cells obey the same growth law. The linear models differ from each other with respect to the timing of the presumptive doubling in their growth rate, the exponential models--according to whether there is or is not a part of the cell that does not contribute to the growth rate. Here we compared the size distributions predicted by each of these models with those of cell length and surface area measured by electron microscopy; the quality of the fit, as determined by the mean-square successive-differences test and the chi 2 goodness-of-fit test, was taken as a measure of the adequacy of the model. The actual data came from two slow-growing E. coli B/r cultures, an A strain (pi = 125 min) and a K strain (pi = 106 min), and a correction was introduced in each to account for the distortion caused by the finite size of the picture frame. The parameter estimates produced by the various models are quite reliable (cv less than 0.1%); we discuss them briefly and compare their values in the two strains. All the length extension models were rejected outright whereas most of the surface growth versions were not. When the same models were tested on A-strain data from a faster growing culture (tau = 21 min), those models that provided an adequate fit to the cell surface area data proved equally satisfactory in the case of cell length. These findings are evaluated and shown to be consistent with cell surface area rather than cell length being the dimension under active control. Three surface area models, all linear, are rejected--those in which doubling of the growth rate occurs with a constant probability from cell birth, at a particular cell age, and precisely at cell division. The evidence in the literature that appears to contradict this last result, rejection of the simple linear surface growth model, is shown to be faulty. The 16 original models are here reduced to five, two involving exponential surface growth and three linear, and possible reasons are presented for our inability to discriminate further at this stage.
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Affiliation(s)
- N B Grover
- Hubert H. Humphrey Centre for Experimental Medicine and Cancer Research, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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97
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Koppes LJ, Woldringh CL, Grover NB. Predicted steady-state cell size distributions for various growth models. J Theor Biol 1987; 129:325-35. [PMID: 3455465 DOI: 10.1016/s0022-5193(87)80005-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The question of how an individual bacterial cell grows during its life cycle remains controversial. In 1962 Collins and Richmond derived a very general expression relating the size distributions of newborn, dividing and extant cells in steady-state growth and their growth rate; it represents the most powerful framework currently available for the analysis of bacterial growth kinetics. The Collins-Richmond equation is in effect a statement of the conservation of cell numbers for populations in steady-state exponential growth. It has usually been used to calculate the growth rate from a measured cell size distribution under various assumptions regarding the dividing and newborn cell distributions, but can also be applied in reverse--to compute the theoretical cell size distribution from a specified growth law. This has the advantage that it is not limited to models in which growth rate is a deterministic function of cell size, such as in simple exponential or linear growth, but permits evaluation of far more sophisticated hypotheses. Here we employed this reverse approach to obtain theoretical cell size distributions for two exponential and six linear growth models. The former differ as to whether there exists in each cell a minimal size that does not contribute to growth, the latter as to when the presumptive doubling of the growth rate takes place: in the linear age models, it is taken to occur at a particular cell age, at a fixed time prior to division, or at division itself; in the linear size models, the growth rate is considered to double with a constant probability from cell birth, with a constant probability but only after the cell has reached a minimal size, or after the minimal size has been attained but with a probability that increases linearly with cell size. Each model contains a small number of adjustable parameters but no assumptions other than that all cells obey the same growth law. In the present article, the various growth laws are described and rigorous mathematical expressions developed to predict the size distribution of extant cells in steady-state exponential growth; in the following paper, these predictions are tested against high-quality experimental data.
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Affiliation(s)
- L J Koppes
- Department of Microbiology, University of Uppsala, Sweden
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98
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Hussain K, Elliott EJ, Salmond GP. The parD- mutant of Escherichia coli also carries a gyrAam mutation. The complete sequence of gyrA. Mol Microbiol 1987; 1:259-73. [PMID: 2834621 DOI: 10.1111/j.1365-2958.1987.tb01932.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The phenotype of a recently-described mutant (OV6), conditionally defective in chromosome partitioning and septal positioning, was originally thought to be due to a new gene (parD) mapping at 88.4 min. We have now shown that, in addition to the parD mutation, OV6 carries a gyrAam mutation and that this mutation is probably responsible for the gross phenotype of the mutant. We have cloned the gyrA gene, identified the GyrA protein, sequenced the gyrA gene and flanking genes, cloned and sequenced the gyrAam mutation, and identified its truncated product. In addition, we have identified the transcriptional start point of the gyrA gene. The E. coli GyrA protein has extensive homologies with Gyrase proteins of other organisms and weak sequence homologies with some eukaryotic cytoskeletal proteins.
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Affiliation(s)
- K Hussain
- Department of Biological Sciences, University of Warwick, Coventry, UK
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99
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Bravo A, de Torrontegui G, Díaz R. Identification of components of a new stability system of plasmid R1, ParD, that is close to the origin of replication of this plasmid. MOLECULAR & GENERAL GENETICS : MGG 1987; 210:101-10. [PMID: 3323833 DOI: 10.1007/bf00337764] [Citation(s) in RCA: 123] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We provide evidence that a mutation which derepresses an autoregulated system that is located in the vicinity of the basic replicon of R1, stabilizes the ParA- and ParB- miniplasmid of R1 pKN1562, without increasing its copy number. The system, which we have called ParD, maps inside the 1.45-kb PstI-EcoRI fragment that is adjacent to the origin of replication of the plasmid. Two proteins whose expression is coordinated are components of the system. The sequence of the PstI-EcoRI fragment was obtained. The wild-type ParD system determines in cis a basal but detectable stability.
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Affiliation(s)
- A Bravo
- Centro de Investigaciones Biológicas (C.S.I.C.), Velázquez, Madrid, Spain
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100
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Hussain K, Begg KJ, Salmond GP, Donachie WD. ParD: a new gene coding for a protein required for chromosome partitioning and septum localization in Escherichia coli. Mol Microbiol 1987; 1:73-81. [PMID: 3330757 DOI: 10.1111/j.1365-2958.1987.tb00529.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A new gene, parD, has been located at 88.5 min on the genetic map of E. coli. Cells carrying an amber mutation in this gene, together with a temperature-sensitive suppressor tRNA, are able to grow, synthesize DNA and divide at both 30 degrees C and 42 degrees C. At 42 degrees C, however, they are defective both in the separation of replicated chromosomes and in the placement of septa. Both the amount of DNA and the number of septa per cell mass are normal in cells growing at 42 degrees C: only the localization of the chromosomes and septa are altered. As a result, cells of random sizes are produced at 42 degrees C and the smallest of these contain no DNA.
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Affiliation(s)
- K Hussain
- Department of Biological Sciences, University of Warwick, Coventry, UK
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