Breviatea

Breviatea, commonly known as breviate amoebae, are a group of free-living, amitochondriate protists with uncertain phylogenetic position. They are biflagellate, and can live in anaerobic (oxygen-free) environments. They are currently placed in the Obazoa clade. They likely do not possess vinculin proteins. Their metabolism relies on fermentative production of ATP as an adaptation to their low-oxygen environment.

The lineage emerged roughly one billion years ago, at a time when the oxygen content of the Earth's oceans was low, and they thus developed anaerobic lifestyles. Together with apusomonads, they are the closest relatives of the opisthokonts, a group that includes animals and fungi. ==Characteristics== === 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.