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Peptidoglycan transformations during Bacillus subtilis sporulation.

Authors
  • 1
  • 1 Division of Biology, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA.
Type
Published Article
Journal
Molecular Microbiology
1365-2958
Publisher
Wiley Blackwell (Blackwell Publishing)
Publication Date
Volume
88
Issue
4
Pages
673–686
Identifiers
DOI: 10.1111/mmi.12201
PMID: 23531131
Source
Medline
License
Unknown

Abstract

While vegetative Bacillus subtilis cells and mature spores are both surrounded by a thick layer of peptidoglycan (PG, a polymer of glycan strands cross-linked by peptide bridges), it has remained unclear whether PG surrounds prespores during engulfment. To clarify this issue, we generated a slender ΔponA mutant that enabled high-resolution electron cryotomographic imaging. Three-dimensional reconstructions of whole cells in near-native states revealed a thin PG-like layer extending from the lateral cell wall around the prespore throughout engulfment. Cryotomography of purified sacculi and fluorescent labelling of PG in live cells confirmed that PG surrounds the prespore. The presence of PG throughout engulfment suggests new roles for PG in sporulation, including a new model for how PG synthesis might drive engulfment, and obviates the need to synthesize a PG layer de novo during cortex formation. In addition, it reveals that B. subtilis can synthesize thin, Gram-negative-like PG layers as well as its thick, archetypal Gram-positive cell wall. The continuous transformations from thick to thin and back to thick during sporulation suggest that both forms of PG have the same basic architecture (circumferential). Endopeptidase activity may be the main switch that governs whether a thin or a thick PG layer is assembled.

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