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MreB of Streptomyces coelicolor is not required for vegetative growth but is involved in spore wall synthesis

Author

  • Paola Mazza
  • Elke E. Noens
  • Kathrin Schirner
  • Nina Grantcharova
  • A. Mieke Mommass
  • Henk K. Koerten
  • Gunther Muth
  • Klas Flärdh
  • Gilles van Wezel
  • Wolfgang Wohlleben

Summary, in English

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.

Publishing year

2006

Language

English

Pages

838-852

Publication/Series

Molecular Microbiology

Volume

60

Issue

4

Document type

Journal article

Publisher

Wiley-Blackwell

Topic

  • Biological Sciences

Status

Published

ISBN/ISSN/Other

  • ISSN: 1365-2958