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MreB of Streptomyces coelicolor is not essential for vegetative growth but is required for the integrity of aerial hyphae and spores
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
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2006 (English)In: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 60, no 4, 838-852 p.Article in journal (Refereed) Published
Abstract [en]

MreB forms a cytoskeleton in many rod-shaped bacteria which is involved in cell shape determination and chromosome segregation. PCR-based and Southern analysis of various actinomycetes, supported by analysis of genome sequences, revealed mreB homologues only in genera that form an aerial mycelium and sporulate. We analysed MreB in one such organism, Streptomyces coelicolor. Ectopic overexpression of mreB impaired growth, and caused swellings and lysis of hyphae. A null mutant with apparently normal vegetative growth was generated. However, aerial hyphae of this mutant were swelling and lysing; spores doubled their volume and lost their characteristic resistance to stress conditions. Loss of cell wall consistency was observed in MreB-depleted spores by transmission electron microscopy. An MreB-EGFP fusion was constructed to localize MreB in the mycelium. No clearly localized signal was seen in vegetative mycelium. However, strong fluorescence was observed at the septa of sporulating aerial hyphae, then as bipolar foci in young spores, and finally in a ring- or shell-like pattern inside the spores. Immunogold electron microscopy using MreB-specific antibodies revealed that MreB is located immediately underneath the internal spore wall. Thus, MreB is not essential for vegetative growth of S. coelicolor, but exerts its function in the formation of environmentally stable spores, and appears to primarily influence the assembly of the spore cell wall.

Place, publisher, year, edition, pages
2006. Vol. 60, no 4, 838-852 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-94047DOI: 10.1111/j.1365-2958.2006.05134.xPubMedID: 16677297OAI: oai:DiVA.org:uu-94047DiVA: diva2:167750
Available from: 2006-02-24 Created: 2006-02-24 Last updated: 2013-03-21Bibliographically approved
In thesis
1. Developmental Control of Cell Division in Streptomyces coelicolor
Open this publication in new window or tab >>Developmental Control of Cell Division in Streptomyces coelicolor
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cell division in the Gram-positive bacterium Streptomyces coelicolor starts with the assembly of the tubulin homologue FtsZ into a cytokinetic ring (the Z ring) at the site of septation. In stark contrast to the binary fission of most bacteria, the syncytial hyphal cells of S. coelicolor exploit two types of cell division with strikingly different outcomes depending on the developmental stage.

The main goal of this study has been to identify developmental mechanisms that modulate this differential performance of the basic cell division machinery.

By isolation and characterization of a non-sporulating ftsZ mutant, we demonstrated that the requirements for Z-ring formation differ between the two types of septation. The ftsZ17(Spo) mutation abolished septation without overtly affecting vegetative growth. This mutant was defective in the assembly of FtsZ into regularly spaced Z rings in sporogenic hyphae, suggesting that the assembly of Z rings is developmentally controlled during sporulation.

An FtsZ-EGFP translational fusion was constructed and used to visualize the progression of FtsZ ring assembly in vivo. This revealed that polymerization of FtsZ occurred throughout the sporogenic cell, with no evidence for pre-determined nucleation sites, and that the placement of multiple Z rings is a dynamic process and involves remodeling of spiral-shaped FtsZ intermediates into regularly spaced rings.

The dynamics of the multiple Z-rings assembly during sporulation was perturbed by the action of the protein CrgA, which is important for coordinating growth and cell division in sporogenic hyphae. CrgA was also found to affect the timing of ftsZ expression and the turnover of the FtsZ protein.

S. coelicolor is the main genetic model of the streptomycetes, which are major industrial antibiotic producers. The control of cell division in these organisms differs from that of other bacteria like Escherichia coli. Thus, it is of fundamental importance to clarify how the streptomycetes reproduce themselves.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 70 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 149
Microbiology, FtsZ, cell division, Streptomyces, GFP, bacterial development, Mikrobiologi
National Category
urn:nbn:se:uu:diva-6412 (URN)91-554-6469-6 (ISBN)
Public defence
2006-03-17, C10:305, BMC, Husargatan 3, Uppsala, 10:00
Available from: 2006-02-24 Created: 2006-02-24Bibliographically approved

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