Open Access Research article

The [FeFe] hydrogenase of Nyctotherus ovalis has a chimeric origin

Brigitte Boxma18, Guenola Ricard2, Angela HAM van Hoek17, Edouard Severing1, Seung-Yeo Moon-van der Staay1, Georg WM van der Staay1, Theo A van Alen1, Rob M de Graaf1, Geert Cremers1, Michiel Kwantes1, Neil R McEwan3, C Jamie Newbold3, Jean-Pierre Jouany4, Tadeusz Michalowski5, Peter Pristas6, Martijn A Huynen2* and Johannes HP Hackstein1

Author Affiliations

1 Department of Evolutionary Microbiology, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands

2 Nijmegen Centre for Molecular Life Sciences (NCMLS) and Center for Molecular and Biomolecular Informatics, CMBI 260 Radboud University Nijmegen Medical Centre, PO Box 9101, NL- 6500 HB Nijmegen, The Netherlands

3 The Institute of Rural Science, University of Wales Aberystwyth, Llanbadarn Fawr, Aberystwyth, Ceredigion, SY23 3AL, Wales, UK

4 INRA, UR1213 Herbivores, Theix, F-63122 St Genès Champanelle, France

5 Kielanowski Institute of Animal Physiology and Nutrition, Polish Acedemy of Sciences, Instytucka 3, P-05-110 Jablonna, near Warsaw, Poland

6 Institute of Animal Physiology, Slovak Academy of Sciences, Soltesovej 4 SK-040 01 Kosice, Slovakia

7 RIKILT – Institute of Food Safety, Wageningen UR, The Netherlands

8 Intervet International, Boxmeer, The Netherlands

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BMC Evolutionary Biology 2007, 7:230  doi:10.1186/1471-2148-7-230

Published: 16 November 2007



The hydrogenosomes of the anaerobic ciliate Nyctotherus ovalis show how mitochondria can evolve into hydrogenosomes because they possess a mitochondrial genome and parts of an electron-transport chain on the one hand, and a hydrogenase on the other hand. The hydrogenase permits direct reoxidation of NADH because it consists of a [FeFe] hydrogenase module that is fused to two modules, which are homologous to the 24 kDa and the 51 kDa subunits of a mitochondrial complex I.


The [FeFe] hydrogenase belongs to a clade of hydrogenases that are different from well-known eukaryotic hydrogenases. The 24 kDa and the 51 kDa modules are most closely related to homologous modules that function in bacterial [NiFe] hydrogenases. Paralogous, mitochondrial 24 kDa and 51 kDa modules function in the mitochondrial complex I in N. ovalis. The different hydrogenase modules have been fused to form a polyprotein that is targeted into the hydrogenosome.


The hydrogenase and their associated modules have most likely been acquired by independent lateral gene transfer from different sources. This scenario for a concerted lateral gene transfer is in agreement with the evolution of the hydrogenosome from a genuine ciliate mitochondrion by evolutionary tinkering.