title: Peptidoglycan transformations during Bacillus subtilis sporulation.
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.
authors.affiliation: Division of Biology, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA.
authors.forename: Elitza I
authors.initials: EI
authors.lastname: Tocheva
authors.forename: Javier
authors.initials: J
authors.lastname: López-Garrido
authors.forename: H Velocity
authors.initials: HV
authors.lastname: Hughes
authors.forename: Jennifer
authors.initials: J
authors.lastname: Fredlund
authors.forename: Erkin
authors.initials: E
authors.lastname: Kuru
authors.forename: Michael S
authors.initials: MS
authors.lastname: Vannieuwenhze
authors.forename: Yves V
authors.initials: YV
authors.lastname: Brun
authors.forename: Kit
authors.initials: K
authors.lastname: Pogliano
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Jensen
mesh_terms: D001412:Bacillus subtilis / Q000254:growth & development* / Q000648:ultrastructure*; D020285:Cryoelectron Microscopy; D055032:Electron Microscope Tomography; D010457:Peptidoglycan / Q000378:metabolism* / Q000648:ultrastructure*; D013171:Spores, Bacterial / Q000254:growth & development* / Q000648:ultrastructure*
chemical_list: D010457:Peptidoglycan