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Hydrogenosome
 
 
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A hydrogenosome is a membrane-enclosed organelle
Organelle

In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid membrane....
 of some anaerobic
Anaerobic organism

An anaerobic organism is any organism that does not require oxygen for growth and may even die in its presence....
 ciliate
Ciliate

The ciliates are a group of protists characterized by the presence of hair-like organelles called cilium, which are identical in structure to flagellum but typically shorter and present in much larger numbers with a different undulating pattern than flagella....
s, trichomonads and fungi. The hydrogenosomes of trichomonads (the most studied of the hydrogenosome-containing microorganisms) produce molecular hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
, acetate
Acetate

An acetate, or ethanoate, is either a salt or ester of acetic acid.In chemistry, the abbreviation Ac refers to the acetyl group. The anion and the functional group may be written as -OAc and AcO-, or OAc respectively....
, carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 and ATP
Adenosine triphosphate

This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer....
 by the combined actions of pyruvate:ferredoxin oxido-reductase
Pyruvate synthase

In enzymology, a pyruvate synthase is an enzyme that catalysis the chemical reactionThe 3 substrate of this enzyme are pyruvate, coenzyme A, and oxidized ferredoxin, whereas its 4 product are acetyl-CoA, carbon dioxide, reduced ferredoxin, and hydrogen ion....
, hydrogenase
Hydrogenase

A hydrogenase is an enzyme that Catalysis the reversible Redox of molecular hydrogen . Hydrogenases play a vital role in Glycolysis.Hydrogen uptake is coupled to the reduction of electron acceptors such as oxygen, nitrate, sulfate, carbon dioxide, and fumarate, whereas proton reduction is essential in pyruvate fermentation and in the di...
, acetate:succinate CoA transferase
Acetate CoA-transferase

In enzymology, an acetate CoA-transferase is an enzyme that catalysis the chemical reactionThus, the two substrate of this enzyme are acyl-CoA and acetate, whereas its two product are fatty acid anion and acetyl-CoA....
 and succinate thiokinase
Succinyl coenzyme A synthetase

Succinyl coenzyme A synthetase catalysis the formation of succinate and coenzyme-A, a 4-carbon metabolite, from succinyl-CoA....
. Superoxide dismutase
Superoxide dismutase

The enzyme superoxide dismutase , catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide. As such, it is an important antioxidant defense in nearly all cells exposed to oxygen....
, malate dehydrogenase
Malate dehydrogenase

Malate dehydrogenase is an enzyme in the citric acid cycle that catalysis the conversion of malate into oxaloacetate and vice versa . Malate dehydrogenase is not to be confused with malic enzyme, which catalyzes the conversion of malate to pyruvate producing NADPH....
 (decarboxylating), ferredoxin
Ferredoxin

Ferredoxins are iron-sulfur proteins that mediate electron transfer in a range of metabolic reactions. The term "ferredoxin" was coined by D.C....
, adenylate kinase
Adenylate kinase

Adenylate kinase is a phosphotransferase enzyme that catalyzes the interconversion of adenine nucleotides, and plays an important role in cellular energy homeostasis ....
 and NADH:ferredoxin oxido-reductase
Ferredoxin-NAD+ reductase

In enzymology, a ferredoxin---NAD+ reductase is an enzyme that catalysis the chemical reactionThus, the two substrate of this enzyme are reduced ferredoxin and nicotinamide adenine dinucleotide, whereas its 3 product are oxidized ferredoxin, nicotinamide adenine dinucleotide, and hydrogen ion....
 are also localized in the hydrogenosome. This organelle is thought to have evolved
Evolution

In biology, evolution is change in the heritability trait of a population of organisms from one generation to the next. These changes are caused by a combination of three main processes: variation, reproduction, and selection....
 from mitochondria, though in the case of trichomonad hydrogenosomes the question remains open.

ogenosomes were isolated, purified, biochemically characterized and named in the early 1970s by D.






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A hydrogenosome is a membrane-enclosed organelle
Organelle

In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid membrane....
 of some anaerobic
Anaerobic organism

An anaerobic organism is any organism that does not require oxygen for growth and may even die in its presence....
 ciliate
Ciliate

The ciliates are a group of protists characterized by the presence of hair-like organelles called cilium, which are identical in structure to flagellum but typically shorter and present in much larger numbers with a different undulating pattern than flagella....
s, trichomonads and fungi. The hydrogenosomes of trichomonads (the most studied of the hydrogenosome-containing microorganisms) produce molecular hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
, acetate
Acetate

An acetate, or ethanoate, is either a salt or ester of acetic acid.In chemistry, the abbreviation Ac refers to the acetyl group. The anion and the functional group may be written as -OAc and AcO-, or OAc respectively....
, carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 and ATP
Adenosine triphosphate

This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer....
 by the combined actions of pyruvate:ferredoxin oxido-reductase
Pyruvate synthase

In enzymology, a pyruvate synthase is an enzyme that catalysis the chemical reactionThe 3 substrate of this enzyme are pyruvate, coenzyme A, and oxidized ferredoxin, whereas its 4 product are acetyl-CoA, carbon dioxide, reduced ferredoxin, and hydrogen ion....
, hydrogenase
Hydrogenase

A hydrogenase is an enzyme that Catalysis the reversible Redox of molecular hydrogen . Hydrogenases play a vital role in Glycolysis.Hydrogen uptake is coupled to the reduction of electron acceptors such as oxygen, nitrate, sulfate, carbon dioxide, and fumarate, whereas proton reduction is essential in pyruvate fermentation and in the di...
, acetate:succinate CoA transferase
Acetate CoA-transferase

In enzymology, an acetate CoA-transferase is an enzyme that catalysis the chemical reactionThus, the two substrate of this enzyme are acyl-CoA and acetate, whereas its two product are fatty acid anion and acetyl-CoA....
 and succinate thiokinase
Succinyl coenzyme A synthetase

Succinyl coenzyme A synthetase catalysis the formation of succinate and coenzyme-A, a 4-carbon metabolite, from succinyl-CoA....
. Superoxide dismutase
Superoxide dismutase

The enzyme superoxide dismutase , catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide. As such, it is an important antioxidant defense in nearly all cells exposed to oxygen....
, malate dehydrogenase
Malate dehydrogenase

Malate dehydrogenase is an enzyme in the citric acid cycle that catalysis the conversion of malate into oxaloacetate and vice versa . Malate dehydrogenase is not to be confused with malic enzyme, which catalyzes the conversion of malate to pyruvate producing NADPH....
 (decarboxylating), ferredoxin
Ferredoxin

Ferredoxins are iron-sulfur proteins that mediate electron transfer in a range of metabolic reactions. The term "ferredoxin" was coined by D.C....
, adenylate kinase
Adenylate kinase

Adenylate kinase is a phosphotransferase enzyme that catalyzes the interconversion of adenine nucleotides, and plays an important role in cellular energy homeostasis ....
 and NADH:ferredoxin oxido-reductase
Ferredoxin-NAD+ reductase

In enzymology, a ferredoxin---NAD+ reductase is an enzyme that catalysis the chemical reactionThus, the two substrate of this enzyme are reduced ferredoxin and nicotinamide adenine dinucleotide, whereas its 3 product are oxidized ferredoxin, nicotinamide adenine dinucleotide, and hydrogen ion....
 are also localized in the hydrogenosome. This organelle is thought to have evolved
Evolution

In biology, evolution is change in the heritability trait of a population of organisms from one generation to the next. These changes are caused by a combination of three main processes: variation, reproduction, and selection....
 from mitochondria, though in the case of trichomonad hydrogenosomes the question remains open.

History

Hydrogenosomes were isolated, purified, biochemically characterized and named in the early 1970s by D. G. Lindmark and M. Müller at Rockefeller University
Rockefeller University

The Rockefeller University is a private university which focuses primarily on basic research in the biomedical fields and offers graduate and postgraduate education....
. In addition to this seminal study on hydrogenosomes, they also demonstrated, for the first time, the presence of pyruvate:ferredoxin oxido-reductase and hydrogenase in eukaryote
Eukaryote

Animals, plants, fungus, and protists are eukaryotes , organisms whose Cell are organized into complex structures enclosed within Cell membrane....
s. Further studies were subsequentially conducted on the biochemical cytology and subcellular organization of anaerobic protozoan parasites (Trichomonas vaginalis
Trichomonas vaginalis

Trichomonas vaginalis, an Anaerobic organism, parasite flagellated protozoan, is the causative agent of trichomoniasis, and is the most common pathogenic protozoan infection of humans in industrialized countries....
, Tritrichomonas foetus
Tritrichomonas foetus

Tritrichomonas foetus' is a single celled flagellated protozoan parasite that is known to be a pathogen of the bovine reproductive tract as well as the intestinal tract of cats....
, Monocercomonas sp., Giardia lamblia
Giardia lamblia

File:Giardia life cycle en.svgGiardia lamblia is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis....
, Entamoeba
Entamoeba

Entamoeba is a genus of Amoebozoa found as internal parasitisms or commensalisms of animals.In 1875, Fedor L?sch described the first proven case of amoebic dysentery in St Petersburg, Russia....
 sp., and Hexamita inflata). Using information obtained from hydrogenosomal and biochemical cytology studies these researchers determined the mode of action of metronidazole
Metronidazole

Metronidazole is a nitroimidazole antibiotic medication used mainly in the treatment of infections caused by susceptible organisms, particularly anaerobe bacterium and protozoa....
 (Flagyl) in 1976. Metronidazole is today recognized as the gold standard chemotherapeutic agent
Chemotherapy

Chemotherapy, in its most general sense, refers to treatment of disease by chemicals that kill cells, specifically those of micro-organisms or cancer....
 for the treatment of anaerobic infections caused by prokaryote
Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other cell membrane-bound organelles. They differ from the eukaryotes, which have a cell nucleus....
s (clostridia
Clostridium

Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores....
, Bacteroides
Bacteroides

Bacteroides is a genus of Gram-negative, bacillus Bacterium. Bacteroides species are non-endospore-forming, Anaerobic bacteria, and may be either motile or non-motile, depending on the species....
, Helicobacter
Helicobacter

Helicobacter is a genus of Gram-negative bacterium possessing a characteristic helix shape. They were initially considered to be members of the Campylobacter genus, but since 1989 they have been grouped in their own genus....
) and eukaryotes (Trichomonas, Tritrichomonas, Giardia, Entamoeba). Metronidazole is taken up by diffusion. Once taken up by anaerobes, it is non-enzymatically reduced by reduced ferredoxin which is produced by the action of pyruvate:ferredoxin oxido-reductase. This reduction cause the production of toxic products (to the anaerobic cell) and allows for selective accumulation in anaerobes.

Description

Hydrogenosomes are approximately 1 micrometre
Micrometre

A micrometre or micron is one Micro- of a metre, or equivalently one thousandth of a millimetre. It is also commonly known as a micron....
 in diameter and are so called because they produce molecular hydrogen. Like mitochondria, they are bound by distinct double membranes and one has an inner membrane with some cristae-like projections. Some hydrogenosomes may have evolved from mitochondria by the concomitant loss of classical mitochondrial features, most notably its genome
Genome

In classical genetics, the genome of a diploid organism including eukarya refers to a full set of chromosomes or genes in a gamete; thereby, a regular somatic cell contains two full sets of genomes....
. A hydrogenosomal genome could not be detected in Neocallimastix
Neocallimastigomycota

Neocallimastigomycota is a phylum of anaerobic fungi, found mainly within the stomachs of ruminants, but with possible distributions elsewhere....
, Trichomonas vaginalis and Tritrichomonas foetus. However, a hydrogenosomal genome has been detected in the cockroach ciliate Nyctotherus ovalis, and the stramenopile Blastocystis
Blastocystis

Blastocystis is a single-celled parasite of the phylum Heterokontophyta, comprising several species, living in humans and animals.Blastocystis is a highly prevalent parasite that infects the gastrointestinal tract....
. The similarity between Nyctotherus and Blastocystis, which are only distantly related, is believed to be the result of convergent evolution, and calls into question whether there is a clear-cut distinction between mitochondria, hydrogenosomes, and mitosomes (another kind of degenerate mitochondria).

Sources

The best studied hydrogenosomes are those of the sexually transmitted parasites Trichomonas vaginalis and Tritrichomonas foetus and those from rumen
Rumen

The rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals....
 chytrids such as Neocallimastix.

The anaerobic ciliated protozoan Nyctotherus ovalis, found in the hindgut
Hindgut

The hindgut is the posterior part of the alimentary canal. It includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon, rectum and upper part of the anal canal....
 of several species of cockroach, has numerous hydrogenosomes that are intimately associated with endosymbiotic
Endosymbiont

An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis . Examples are nitrogen-fixing bacterium which live in root nodules on legume roots, single-celled algae inside reef-building corals, and bacterial endosymbionts that provide essential nutrients to about 10%?15% of in...
 methane-producing archaea
Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . Archaea, like bacteria, are prokaryotic....
, the latter using the hydrogen produced by the hydrogenosomes. The matrix of N. ovalis hydrogenosomes contains ribosome
Ribosome

Ribosomes are complexes of RNA and protein that are found in all cell s. Ribosomes from bacteria, archaea and eukaryotes, the three domains of life on Earth, have significantly different structure and RNA....
-like particles of the same size as a numerous type of ribosome (70s) of the endosymbiotic methanogen
Methanogen

Methanogens are archaea that produce methane as a metabolic byproduct in anoxic conditions. They are common in wetlands, where they are responsible for marsh gas, and in the guts of animals such as ruminants and humans, where they are responsible for the methane content of flatulence....
ic archaea. This suggested the presence of an organellar genome which was indeed discovered by Akhmanova and later partly sequenced by Boxma.

See also

  • Mitochondria
  • Chloroplast
    Chloroplast

    Chloroplasts are organelles found in plant cells and other eukaryote organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve Thermodynamic free energy in the form of Adenosine triphosphate and reduce NADP to NADPH through a complex set of processes called photosynthesis....