Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation

  • Nature volume 426, pages 172176 (13 November 2003)
  • doi:10.1038/nature01945
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Giardia intestinalis (syn. lamblia) is one of the most widespread intestinal protozoan pathogens worldwide, causing hundreds of thousands of cases of diarrhoea each year1. Giardia is a member of the diplomonads, often described as an ancient protist group whose primitive nature is suggested by the lack of typical eukaryotic organelles (for example, mitochondria, peroxisomes), the presence of a poorly developed endomembrane system and by their early branching in a number of gene phylogenies1,2. The discovery of nuclear genes of putative mitochondrial ancestry in Giardia3,4,5,6,7 and the recent identification of mitochondrial remnant organelles in amitochondrial protists such as Entamoeba histolytica8,9 and Trachipleistophora hominis10 suggest that the eukaryotic amitochondrial state is not a primitive condition but is rather the result of reductive evolution. Using an in vitro protein reconstitution assay and specific antibodies against IscS and IscU—two mitochondrial marker proteins involved in iron–sulphur cluster biosynthesis—here we demonstrate that Giardia contains mitochondrial remnant organelles (mitosomes) bounded by double membranes that function in iron–sulphur protein maturation. Our results indicate that Giardia is not primitively amitochondrial and that it has retained a functional organelle derived from the original mitochondrial endosymbiont.

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We thank G. Clark, J. Bowyer and S. Cutting for critically reading the manuscript. A recombinant plasmid containing the T. vaginalis ferredoxin gene was provided by J. P. Germanas and K. Krause. The use of partial genome sequence information from the Giardia Genome Project Database26 is acknowledged. The technical assistance of J. James and N. Sommerville is also acknowledged. M.H. is a sabbatical visitor supported by CINVESTAV, México. Research at the Rockefeller University (gene cloning, antibody generation) was supported by a NIH grant to M.M. Research at Charles University (in vitro assembly of Fe–S clusters) was supported by a grant from FIRCA to J.Tachezy. J.M.L. (electron microscopy) was supported by a Research Leave Fellowship from the Wellcome Trust and by Tenovus Scotland. Research at Royal Holloway (bioinformatics, cell fractionation, fluorescence confocal microscopy, manuscript writing, project coordination) was supported by a Wellcome Trust grant to J.Tovar.

Author information

Author notes

    • Lidya B Sánchez

    Present address: Public Health Research Institute, Newark, New Jersey 07103, USA


  1. School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK

    • Jorge Tovar
    • , Gloria León-Avila
    • , Mark van der Giezen
    •  & Manuel Hernández
  2. The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA

    • Lidya B Sánchez
    •  & Miklós Müller
  3. Department of Parasitology, Faculty of Science, Charles University, 12844 Prague 2, Czech Republic

    • Robert Sutak
    •  & Jan Tachezy
  4. School of Life Sciences, WTB/MSI complex, University of Dundee, Dundee DD1 5EH, UK

    • John M. Lucocq


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Competing interests

The authors declare that they have no competing financial interests.

Corresponding author

Correspondence to Jorge Tovar.


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