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Estimating Z-ring radius and contraction in dividing Escherichia coli
Kungliga Tekniska Högskolan, Stockholm.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Kungliga Tekniska Högskolan, Stockholm.
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2010 (English)In: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 76, no 1, 151-158 p.Article in journal (Refereed) Published
Abstract [en]

We present a fluorescence recovery after photobleaching-based method for monitoring the progression of septal Z-ring contraction in dividing Escherichia coli cells. In a large number of cells undergoing division, we irreversibly bleached cytosolically expressed Enhanced Green Fluorescent Protein on one side of the septal invagination and followed the fluorescence relaxation on both sides of the septum. Since the relaxation time depends on the cross-sectional area of the septum, it can be used to determine the septal radius r. Assuming that the fraction of the observed cells with r-values in a given interval reflects the duration of that interval in the division process we could derive an approximate time-course for the contraction event, as a population average. By applying the method repeatedly on individual cells, the contraction process was also followed in real time. On a population average level, our data are best described by a linear contraction process in time. However, on the single cell level the contraction processes display a complex behaviour, with varying levels of activity. The proposed approach provides a simple yet versatile method for studying Z-ring contraction in vivo, and will help to elucidate its underlying mechanisms.

Place, publisher, year, edition, pages
2010. Vol. 76, no 1, 151-158 p.
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-62904DOI: 10.1111/j.1365-2958.2010.07087.xOAI: oai:DiVA.org:su-62904DiVA: diva2:445466
Available from: 2011-10-04 Created: 2011-10-04 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Cell division in Escherichia coli
Open this publication in new window or tab >>Cell division in Escherichia coli
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Gram-negative bacterium Escherichia coli is a model system to describe the biochemistry and cell biology of cell division in bacteria. This process can be divided into three major steps. The first step involves the replication of the DNA, followed by an elongation step in which the cells become twice as long. In the last step the elongated cell constricts in the middle and the two daughter cells are separated. The cell division process in E. coli has been extensively studied for at least 50 years and a lot is known, however many details are still vague. New proteins involved in the process continue to be identified and the number of these proteins as well as the interactions among them are not yet fully known. It is therefore not completely understood how the contraction proceeds to form two daughter cells. In this thesis, I have carried out experiments that contribute to our understanding of cell division in E. coli. Using fluorescence microscopy I show that the contraction of the inner membrane in dividing E. coli proceeds in a linear fashion and that the periplasm closes after the cytoplasm. I have also analyzed the oligomeric state of two proteins involved in the cell division and I show that the early cell division protein ZipA can dimerize. This could explain how this protein can bundle FtsZ protofilaments, as it could bridge two protofilaments. Penicillin-binding protein 5 (PBP5) has been found to localize to the septum and it has been suggested to be connected to cell division. I have found that PBP5 forms a homo-oligomeric complex, most likely a dimer. The dimer can be modeled in a back-to-back conformation with the catalytic domains being flexible. This allows PBP5 to reach for pentapeptides of the peptidoglycan at different distances from the membrane. An understanding of the mechanisms used by the cell division proteins and their protein: protein interactions can be a first step towards determining new antibiotic targets.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2011. 61 p.
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-62908 (URN)978-91-7447-339-1 (ISBN)
Public defence
2011-11-18, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 14:00 (English)
Opponent
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Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: Manuscript. Available from: 2011-10-27 Created: 2011-10-04 Last updated: 2011-10-18Bibliographically approved

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