Antonie van Leeuwenhoek

, Volume 102, Issue 2, pp 203–219

The unusual cell biology of the hyperthermophilic Crenarchaeon Ignicoccus hospitalis

  • Harald Huber
  • Ulf Küper
  • Stefanie Daxer
  • Reinhard Rachel
Invited Review Paper

DOI: 10.1007/s10482-012-9748-5

Cite this article as:
Huber, H., Küper, U., Daxer, S. et al. Antonie van Leeuwenhoek (2012) 102: 203. doi:10.1007/s10482-012-9748-5

Abstract

The Crenarchaeon Ignicoccus hospitalis is an anaerobic, obligate chemolithoautotrophic hyperthermophile, growing by reduction of elemental sulfur using molecular hydrogen as electron donor. Together with Nanoarchaeum equitans it forms a unique, archaeal biocoenosis, in which I. hospitalis serves as host for N. equitans. Both organisms can be cultivated in a stable coculture which is mandatory for N. equitans but not for I. hospitalis. This strong dependence is affirmed by the fact that N. equitans obtains its lipids and amino acids from the host. I. hospitalis cells exhibit several unique features: they can adhere to surfaces by extracellular appendages (‘fibers’) which are not used for motility; they use a novel CO2 fixation pathway, the dicarboxylate/4-hydroxybutyrate pathway; and they exhibit a unique cell envelope for Archaea consisting of two membranes but lacking an S-layer. These membranes form two cell compartments, a tightly packed cytoplasm surrounded by a weakly staining intermembrane compartment (IMC) with a variable width from 20 to 1,000 nm. In this IMC, many round or elongated vesicles are found which may function as carriers of lipids or proteins out of the cytoplasm. Based on immuno-EM analyses and immuno-fluorescence experiments it was demonstrated recently that the A1AO ATP synthase, the H2:sulfur oxidoreductase complex and the acetyl-CoA synthetase (ACS) of I. hospitalis are located in its outermost membrane. Therefore, this membrane is energized and is here renamed as “outer cellular membrane” (OCM). Among all prokaryotes possessing two membranes in their cell envelope, I. hospitalis is the first organism with an energized outermost membrane and ATP synthesis outside the cytoplasm. Since DNA and ribosomes are localized in the cytoplasm, energy conservation is separated from information processing and protein biosynthesis in I. hospitalis. This raises questions concerning the function and characterization of the two membranes, the two cell compartments and of a possible ATP transfer to N. equitans.

Keywords

Ignicoccus hospitalis Cell biology Archaea ATP synthase Cell compartimentation Immuno-localization Nanoarchaeum equitans 

Supplementary material

10482_2012_9748_MOESM1_ESM.pdf (1005 kb)
Supplementary material 1 (PDF 1,005 kb)

Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Harald Huber
    • 1
  • Ulf Küper
    • 1
    • 3
  • Stefanie Daxer
    • 1
  • Reinhard Rachel
    • 2
  1. 1.Institute for Microbiology and Archaea Center, Faculty of Biology and Preclinical MedicineUniversity RegensburgRegensburgGermany
  2. 2.Faculty of Biology and Preclinical Medicine, Center for Electron MicroscopyUniversity RegensburgRegensburgGermany
  3. 3.BASFLudwigshafenGermany

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