title: Outer membrane continuity and septosome formation between vegetative cells in the filaments of Anabaena sp. PCC 7120.
abstract: Anabaena sp. PCC 7120 is a prototype filamentous nitrogen-fixing cyanobacterium, in which nitrogen fixation and photosynthesis are spatially separated. Recent molecular and cellular studies have established the importance of molecular exchange between cells in the filament, but the routes involved are still under investigation. Two current models propose either a continuous periplasm or direct connections between adjacent cells whose integrity requires the protein SepJ. We used electron tomography to analyze the ultrastructure of the septum between vegetative cells in the Anabaena filament and were able to visualize intercellular connections that we term 'SEPTOSOMES'. We observed that, whereas the existence of the septosome does not depend on the presence of SepJ, the spacing between the two plasma membranes of the septum was significantly decreased in a ΔsepJ mutant. In addition, we observed that the peptidoglycan layer of each cell enters the septum but the outer membrane does not. Thus, each cell in the filament is individually surrounded by a plasma membrane and a peptidoglycan layer, and physical cell-cell contacts are mediated by the septosome.
authors.affiliation: Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.
authors.forename: Laura
authors.initials: L
authors.lastname: Wilk
authors.forename: Mike
authors.initials: M
authors.lastname: Strauss
authors.forename: Mareike
authors.initials: M
authors.lastname: Rudolf
authors.forename: Kerstin
authors.initials: K
authors.lastname: Nicolaisen
authors.forename: Enrique
authors.initials: E
authors.lastname: Flores
authors.forename: Werner
authors.initials: W
authors.lastname: Kühlbrandt
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D017033:Anabaena / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure*; D001422:Bacterial Adhesion; D002462:Cell Membrane / Q000648:ultrastructure*; D055032:Electron Microscope Tomography; D017353:Gene Deletion; D008565:Membrane Proteins / Q000235:genetics; D010457:Peptidoglycan / Q000648:ultrastructure
chemical_list: D008565:Membrane Proteins; D010457:Peptidoglycan