Breviatea

Mitochondrion-related organelles Mitochondrion-related organelles (MROs) are organelles that evolved from a degradation of ancestral, fully functional mitochondria. Among Breviatea, MROs are present in Pygsuia, Breviata and Subulatomonas. In the cells of Pygsuia, for which the complete transcriptome is known, there is a single smooth MRO that lacks a mitochondrial genome and most components of the electron transport chain. Of the citric acid cycle enzymes, which are present in the mitochondria in other organisms, only two are present in Pygsuia: fumarase and succinate dehydrogenase. In contrast, Lenisia cells contain multiple MROs with cristae. == Evolution ==

Breviatea is a clade of basal eukaryotes. They are closely related to the apusomonads and the Opisthokonta supergroup, and together they compose the larger clade Obazoa, which is the sister group to Amoebozoa. Within Breviatea, the four known species are distributed into smaller clades of two species each: one uniting Breviata with Subulatomonas, and one uniting Lenisia with Pygsuia. == Taxonomy ==

History The class Breviatea was created in 2004 by British protozoologist Thomas Cavalier-Smith to group a problematic taxon previously known as Mastigamoeba invertens. This organism, initially classified in the Archamoebae within phylum Amoebozoa, appeared to strongly diverge in phylogenetic trees based on ribosomal RNA and had a structure very different from other archamoebae. Because of these results, M. invertens was separated into the order Breviatida, contained in the monotypic class Breviatea. In 2016, a fourth breviate Lenisia limosa was described without a family rank. Classification There are currently four accepted genera, each containing only one species. • Breviata • Breviata anathema • Lenisia • Lenisia limosa • Pygsuia • Pygsuia biforma • Subulatomonas • Subulatomonas tetraspora == Distribution ==

Breviate species have been found in aquatic environments in various parts of the world, including off the coast of Prince Edward Island on the eastern coast of North America, around the San Juan Islands on the western coast of North America, off the coast of Catalonia in Spain, and in the Wadden Sea along the coast of Germany. == References ==