diplomonad

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diplomonad

a member of the group at one time considered to be an order of the Protozoan class Zoomastigophora but more recently considered to be of kingdom-equivalent status. The group contains both free-living and parasitic forms. see CLASSIFICATION.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
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Chapters are written from a molecular and genomic perspective, with speculative models for future research, and address the genome projects for and cytoskeletons of Entamoeba histolytica, Trichomonas vaginalis, Giardia and other diplomonads; genomic analyses and manipulation of gene expression in Entamoeba histolytica; nuclear and chromosomal structure and replication in Giardia; and the mitochondrion-like organelles of a fourth anaerobe, Blastocystis.
Phylogenetic analyses suggested that the short Fe-hydrogenase genes of entamoeba and diplomonads share a common ancestor, while the long Fe-hydrogenase gene of entamoeba appears to have been laterally transferred from a bacterium.
Second, entamoebas and diplomonads have long been thought not to produce hydrogen gas in culture, although a recent report suggests giardias may produce hydrogen under anaerobic conditions (Lindmark and Muller, 1973; Reeves, 1984; Brown et al., 1998; Muller, 1998; Lloyd and Harris, 2002).
Microsporidia and diplomonads, single-celled eukaryotes that live as parasites inside other cells, seem to carry genes resembling those that encode mitochondrial proteins.
The newly recognized relationship between mitochondria and hydrogenosomes, as well as the research on microsporidia and diplomonads, pushes the origin of these two organelles back to the earliest eukaryotes, if not earlier.
One explanation, the hypothesis preferred by Brugerolle and Taylor (1977) and by Vickerman (I 989), assumes the free-living status to be plesiomorphic for the diplomonads (Fig.
If this is true, intestinal parasitism is clearly plesiomorphic for the diplomonads, having arisen long before the divergence of this group from the parasitic ancestor shared with the retortomonads.
These purportedly primitively amitochondriate protists included the microsporidia, pelobionts, diplomonads, retortamonads, oxymonads, entamoebae, trichomonads, and other parabasalids.
There is evidence that many archezoan groups are secondarily amitochondriate (4-8) although the diplomonads and parabasalids have clung more resolutely to the base of the eukaryotic tree than other taxa.
These are the diplomonads, the trichomonads, and the microsporidia, all groups that consist largely of parasitic species (8).
There are thus some uncertainties about microsporidia, but the EF phylogenies might seem to be consistent with the proposal, made by Cavalier-Smith (11, 12) before any molecular data became available, that diplomonads (including Giardia), parabasalids (including Trichomonas), and microsporidia could be primitively amitochondriate, and that a taxon Archezoa could be created for these protists.
Among the early-branching amitochondriate protists, diplomonads remained as possible candidates for being primitively amitochondriate.

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