The diplomonads are a group of flagellates, most of which are parasitic. They include most notably Giardia lamblia, which causes giardiasis in humans. They are placed among the metamonads, and appear particularly close relatives of the retortamonads.
With a few exceptions, diplomonads are double cells: they have two nuclei, each with four associated flagella, arranged symmetrically about the body's main axis. Like their relatives, they lack mitochondria, but are now known to possess mitochondrial relics called mitosomes. These are not used in ATP synthesis the way mitochondria are, but are involved in the maturation of iron-sulfur proteins.
Diplomonads used to be considered one of the most primitive eukaryotes and some thought that they might have been the link between eukaryotes and prokaryotes because though diplomonads are very characteristic eukaryotes, one main difference is that they lack mitochondria.
Diplomonads do not possess mitochondria, and thus they cannot perform respiration and instead must obtain their energy from fermentative processes.
Diplomonads are able to ferment sugars such as glucose to produce energy, and they are also capable of fermenting the amino acid arginine as a means of obtaining energy.
Diplomonads are common microaerophilic protists in anoxic environments, and most known diplomonads have been isolated as either commensals or parasites of the metazoan intestinal tract [1].
Binucleate diplomonads are believed to be related to mono-nucleate anaerobic protists such as retortamonads and enteromonads [1,3,4].
Giardia intestinalis) are perhaps the most well known of the diplomonads and are unique among diplomonads due to the presence of the ventral disc, which is a novel microtubule organelle that facilitates attachment to the intestinal microvilli in vertebrate hosts [7,8].
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