Anaeramoeba

As the name implies, Anaeramoeba are anaerobic amoeboid organisms which form a fan-like shape similar to that of Flamella. At least two species can also sometimes assume flagellate forms; with either two or four flagella. They contain double-membrane bound organelles called hydrogenosomes, which is a type of mitochondria-related organelles (MROs) and assumed to be derived from mitochondria,^[1] to perform metabolism in anaerobic environments. The hydrogenosomes in Anaeramoeba are closely associated with H₂-consuming bacterial symbionts, which are enveloped by Anaeramoeba host's membrane called symbiosome^[2].

Anaeramoeba specimens were first isolated in 2017, from shallow marine sediments around the world^[3]. Despite the similarities to Flamella in both morphology and environment, genetic analyses found that Anaeramoeba do not belong within Amoebozoa.^[3] Instead, Anaeramoeba represents a newly identified protist belonging to Metamonads, as a close relative to parabasalids.^[1]

Anaeramoeba's symbiosome is a unique highly elaborate membrane-bound structure that houses their bacterial symbionts in close association with their hydrogenosomes that allow efficient metabolic syntrophy between the hosts and the symbionts^[2]. In A. flamelloides BUSSELTON2, the symbionts are suggested to be Desulfobacteraceae, that uses the hydrogenosome products from the host, including H₂, acetate and propionate ^[2], together with sulfate that they acquire through deep membrane-pits of the symbiosome to the cell-surrounding environment, in their metabolic pathways ^[2].