title: Sporulation, bacterial cell envelopes and the origin of life.
abstract: Electron cryotomography (ECT) enables the 3D reconstruction of intact cells in a near-native state. Images produced by ECT have led to the proposal that an ancient sporulation-like event gave rise to the second membrane in diderm bacteria. Tomograms of sporulating monoderm and diderm bacterial cells show how sporulation can lead to the generation of diderm cells. Tomograms of Gram-negative and Gram-positive cell walls and purified sacculi suggest that they are more closely related than previously thought and support the hypothesis that they share a common origin. Mapping the distribution of cell envelope architectures onto a recent phylogenetic tree of life indicates that the diderm cell plan, and therefore the sporulation-like event that gave rise to it, must be very ancient. One explanation for this model is that during the cataclysmic transitions of the early Earth, cellular evolution may have gone through a bottleneck in which only spores survived, which implies that the last bacterial common ancestor was a spore.
authors.affiliation: Department of Stomatology and the Department of Biochemistry and Molecular Medicine, Université de Montréal, P. O. Box 6128 Station Centre-Ville, Montreal, Québec H3C 3J7, Canada.
authors.forename: Elitza I
authors.initials: EI
authors.lastname: Tocheva
authors.affiliation: Department of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.
authors.forename: Davi R
authors.initials: DR
authors.lastname: Ortega
authors.affiliation: Howard Hughes Medical Institute, Department of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA.
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Jensen
mesh_terms: D005075:Biological Evolution; D002462:Cell Membrane / Q000737:chemistry* / Q000648:ultrastructure; D002473:Cell Wall / Q000737:chemistry* / Q000648:ultrastructure; D006090:Gram-Negative Bacteria / Q000648:ultrastructure; D006094:Gram-Positive Bacteria / Q000502:physiology* / Q000648:ultrastructure; D010457:Peptidoglycan / Q000737:chemistry; D010802:Phylogeny; D013171:Spores, Bacterial / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D010457:Peptidoglycan