title: Ignicoccus hospitalis and Nanoarchaeum equitans: ultrastructure, cell-cell interaction, and 3D reconstruction from serial sections of freeze-substituted cells and by electron cryotomography.
abstract: Ultrastructure and intercellular interaction of Ignicoccus hospitalis and Nanoarchaeum equitans were investigated using two different electron microscopy approaches, by three-dimensional reconstructions from serial sections, and by electron cryotomography. Serial sections were assembled into 3D reconstructions, for visualizing the unusual complexity of I. hospitalis, its huge periplasmic space, the vesiculating cytoplasmic membrane, and the outer membrane. The cytoplasm contains fibres which are reminiscent to a cytoskeleton. Cell division in I. hospitalis is complex, and different to that in Euryarchaeota or Bacteria. An irregular invagination of the cytoplasmic membrane is followed by separation of the two cytoplasms. Simultaneous constriction of cytoplasmic plus outer membrane is not observed. Cells of N. equitans show a classical mode of cell division, by constriction in the mid-plane. Their cytoplasm exhibits two types of fibres, elongated and ring-shaped. Electron micrographs of contact sites between I. hospitalis and N. equitans exhibit two modes of interaction. One is indirect and mediated by thin fibres; in other cells the two cell surfaces are in direct contact. The two membranes of I. hospitalis cells are frequently seen in direct contact, possibly a prerequisite for transporting metabolites or substrates from the cytoplasm of one cell to the other. Rarely, a transport based on cargo vesicles is observed between I. hospitalis and N. equitans.
authors.affiliation: Centre for Electron Microscopy, Faculty for Biology and Preclinical Medicine, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Junglas
authors.forename: Ariane
authors.initials: A
authors.lastname: Briegel
authors.forename: Tillmann
authors.initials: T
authors.lastname: Burghardt
authors.forename: Paul
authors.initials: P
authors.lastname: Walther
authors.forename: Reinhard
authors.initials: R
authors.lastname: Wirth
authors.forename: Harald
authors.initials: H
authors.lastname: Huber
authors.forename: Reinhard
authors.initials: R
authors.lastname: Rachel
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure; D003593:Cytoplasm / Q000648:ultrastructure; D019620:Desulfurococcaceae / Q000254:growth & development* / Q000648:ultrastructure*; D021621:Imaging, Three-Dimensional / Q000379:methods; D046529:Microscopy, Electron, Transmission; D046588:Nanoarchaeota / Q000254:growth & development* / Q000648:ultrastructure*; D014054:Tomography / Q000379:methods