Hydrogenosome

A hydrogenosome is a membrane-enclosed organelle of ciliates, trichomonads and fungi. It produces molecular hydrogen and ATP. This organelle is thought to have most likely evolved from mitochondria.

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History

Hydrogenosomes were discovered in the early 1970s by Lindmark and Müller in the US^[1].

Description

Hydrogenosomes are approximately 1 micrometre in diameter and are so called because they produce molecular hydrogen. Like mitochondria, they are bound by distinct double membranes and have an inner membrane with some cristae-like projections. Hydrogenosomes evolved from mitochondria by the concomitant loss of classical mitochondrial features, most notably its genome. A hydrogenosomal genome could not be detected in Neocallimastix, Trichomonas vaginalis and Trichomonas foetus ^[2]. However, a hydrogenosomal genome has been detected in the cockroach ciliate Nyctotherus ovalis in 1998 ^[3].

Sources

The best studied hydrogenosomes are those of the sexually transmitted parasites Trichomonas vaginalis and Tritrichomonas foetus and those from rumen chytrids such as Neocallimastix.

The anaerobic ciliated protozoan Nyctotherus ovalis, found in the hindgut of several species of cockroach, has numerous hydrogenosomes that are intimately associated with endosymbiotic methane-producing Archaea, the latter using the hydrogen produced by the hydrogenosomes. The matrix of N. ovalis hydrogenosomes contains ribosome-like particles of the same size as a numerous type of ribosome (70s) of the endosymbiotic methanogenic Archaea. This suggested the presence of an organellar genome which was discovered indeed by Akhmanova and later partly sequenced by Boxma.^[4][5]

References

1. ^ Lindmark D G & Müller M, "Hydrogenosome, a cytoplasmic organelle of the anaerobic flagellate Tritrichomonas foetus, and its role in pyruvate metabolism" J Biol Chem 1973 248:7724−7728.
2. ^ van der Giezen et al, "Mitochondrion-derived organelles in protists and fungi", Int Rev Cytol 2005, 244:175-225.
3. ^ Akhmanova et al, Nature 1998 396:527.
4. ^ Akhmanova et al, Nature 1998 396:527.
5. ^ Boxma et al, Nature 2005 434:74-79.